Ewing Sarcoma

MONDO:0012817 Pathograph 26 Show in embeddings browser bone sarcoma

Ewing sarcoma is an aggressive pediatric bone and soft tissue malignancy characterized by the pathognomonic EWS-FLI1 fusion gene, present in approximately 85% of cases. This translocation t(11;22)(q24;q12) creates a chimeric transcription factor that forms dosage-sensitive chromatin hubs, rewires chromatin at GGAA microsatellites, activates core regulatory circuitry, represses lineage and tumor-suppressive programs through NuRD/CHD4-associated mechanisms, alters metabolism and DNA repair, and blocks lineage differentiation. The fusion is diagnostic and remains a compelling but challenging therapeutic target; developmental IGF-1/YAP1 signaling, germline GGAA-repeat architecture, ETV6 counter-regulation, DHX9/SLFN11 replication-stress biology, and secondary events such as STAG2 loss can modify the fusion-driven pathograph and contribute to high-risk biology.

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16
Pathophys.
4
Histopath.
7
Phenotypes
4
Hypotheses
5
Gaps
26
Pathograph
4
Genes
7
Medical Actions
2
Subtypes
4
Models
2
Deep Research
4
Hyp. Reports
🏷

Classifications

Harrison's Chapter
ONCOLOGY_HEMATOLOGY
ICD-O Morphology
Sarcoma
◆

Subtypes

2
Osseous Ewing Sarcoma MONDO:0002625
Primary tumors arising in bone, most commonly the pelvis, femur, and other long bones. Accounts for approximately 80% of Ewing sarcoma cases. Typically presents with localized pain and swelling.
Extraosseous Ewing Sarcoma MONDO:0018270
Primary tumors arising in soft tissues outside of bone. Can occur in chest wall, paravertebral region, or extremities. Shares the same EWS-FLI1 fusion and treated similarly to osseous disease.
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Mechanistic Hypotheses

4
Canonical EWS-FLI1 fusion enhanceropathy model
canonical_fusion_enhanceropathy_model CANONICAL
EWS-FLI1 is the truncal disease driver. Its EWSR1 low-complexity domain and FLI1 DNA-binding domain form dosage-sensitive chromatin hubs and retarget chromatin machinery to GGAA microsatellites and ETS elements. The mechanism includes BAF-supported enhancer activation, NuRD/CHD4-associated repression, ETV6 counter-regulation at short GGAA repeats, core regulatory circuitry, blocked differentiation, metabolic rewiring, and proliferation.
Pathograph links
EWS-FLI1 Fusion Oncogene -> EWS-FLI1 Hub and Dosage Control DIRECT Endogenous EWS-FLI1 forms dynamic low-complexity-domain-dependent chromatin hubs, and tumor behavior is sensitive to both excessive and submaximal fusion protein activity.
EWS-FLI1 Fusion Oncogene -> BAF Complex Retargeting DIRECT The EWSR1-derived low-complexity domain enables EWS-FLI1 to recruit BAF chromatin-remodeling complexes to tumor-specific enhancers.
EWS-FLI1 Fusion Oncogene -> GGAA Microsatellite Enhancer Reprogramming DIRECT EWS-FLI1 occupies GGAA microsatellite repeats and canonical ETS sites, creating de novo enhancers while repressing other enhancer classes.
EWS-FLI1 Fusion Oncogene -> NuRD/CHD4 Repressive Chromatin Program DIRECT EWS-FLI1 has a direct repressive arm involving NuRD-associated chromatin machinery, including CHD4 and LSD1/HDAC activity, in addition to its enhancer-activation arm.
EWS-FLI1 Fusion Oncogene -> Blocked Differentiation INDIRECT KNOWN INTERMEDIATES Fusion-driven transcriptional repression and downstream transcription factors suppress mesenchymal differentiation programs. Intermediates: enhancer repression of mesenchymal lineage regulators; NKX2-2-mediated repression of mesenchymal features
EWS-FLI1 Fusion Oncogene -> ATF4-Serine-Glycine Metabolic Reprogramming DIRECT EWS-FLI1 directly activates ATF4 and metabolic stress-response programs.
BAF Complex Retargeting -> GGAA Microsatellite Enhancer Reprogramming DIRECT BAF retargeting supports tumor-specific enhancer activation downstream of EWS-FLI1 occupancy.
EWS-FLI1 Hub and Dosage Control -> GGAA Microsatellite Enhancer Reprogramming DIRECT Dynamic EWS-FLI1 hubs concentrate the fusion on chromatin and tune enhancer activation at GGAA microsatellites.
EWS-FLI1 Hub and Dosage Control -> Tumor Cell Proliferation and Survival INDIRECT KNOWN INTERMEDIATES TRIM8-dependent fusion-protein turnover defines a tolerated oncogene dosage window required for Ewing sarcoma cell survival. Intermediates: TRIM8-mediated EWS-FLI1 degradation; oncogene overdose avoidance
EWS-FLI1 Hub and Dosage Control -> Metastatic Disease INDIRECT KNOWN INTERMEDIATES Graded EWS-FLI1 loss can produce non-linear phenotypes, including a pro-metastatic state at modest depletion. Intermediates: submaximal EWS-FLI1 depletion; epithelial-mesenchymal plasticity
GGAA Microsatellite Enhancer Reprogramming -> Core Regulatory Circuitry Activation DIRECT EWS-FLI1 establishes super-enhancers for KLF15, TCF4, and NKX2-2, building an autoregulatory transcription-factor circuit.
GGAA Microsatellite Enhancer Reprogramming -> Blocked Differentiation DIRECT Aberrant enhancer repression suppresses mesenchymal lineage regulators.
GGAA Microsatellite Enhancer Reprogramming -> ETV6 GGAA Counter-Regulation INDIRECT KNOWN INTERMEDIATES Native ETS factor ETV6 competes with EWS-FLI1 at short GGAA repeats and restrains a subset of fusion-driven enhancer activity. Intermediates: competition at short GGAA repeats
ETV6 GGAA Counter-Regulation -> GGAA Microsatellite Enhancer Reprogramming DIRECT ETV6 competition modulates EWS-FLI1 occupancy and output at short GGAA microsatellite enhancers.
ETV6 GGAA Counter-Regulation -> Tumor Cell Proliferation and Survival INDIRECT KNOWN INTERMEDIATES ETV6 perturbation can increase EWS-FLI1-driven transcriptional stress and suppress tumor growth in preclinical models. Intermediates: EWS-FLI1 hyperactivation; cellular stress
GGAA Microsatellite Germline Susceptibility Architecture -> GGAA Microsatellite Enhancer Reprogramming DIRECT Germline GGAA repeat length and purity alter the strength of EWS-FLI1 neo-enhancer formation at susceptible loci.
GGAA Microsatellite Germline Susceptibility Architecture -> Tumor Cell Proliferation and Survival INDIRECT KNOWN INTERMEDIATES Susceptibility-locus enhancer activation can increase expression of proliferation-associated transcriptional regulators. Intermediates: EGR2 enhancer activation; RREB1-mediated RAS/MAPK-associated transcription
NuRD/CHD4 Repressive Chromatin Program -> Blocked Differentiation INDIRECT KNOWN INTERMEDIATES NuRD/LSD1/HDAC-mediated repression helps EWS-FLI1 maintain an immature, transformed state. Intermediates: repression of lineage-regulatory genes; repression of tumor-suppressive target genes
NuRD/CHD4 Repressive Chromatin Program -> Tumor Cell Proliferation and Survival INDIRECT KNOWN INTERMEDIATES CHD4/NuRD dependence links the transcriptional pathograph to DNA-damage buffering and tumor cell survival. Intermediates: CHD4-dependent chromatin architecture maintenance; suppression of spontaneous DNA damage
Core Regulatory Circuitry Activation -> Tumor Cell Proliferation and Survival DIRECT Core regulatory transcription factors sustain proliferation and oncogenic signaling pathways in Ewing sarcoma cells.
Core Regulatory Circuitry Activation -> Blocked Differentiation INDIRECT KNOWN INTERMEDIATES Core regulatory circuitry reinforces the undifferentiated tumor state. Intermediates: NKX2-2-mediated repression of mesenchymal features
ATF4-Serine-Glycine Metabolic Reprogramming -> Tumor Cell Proliferation and Survival INDIRECT KNOWN INTERMEDIATES Fusion-driven metabolic rewiring supports biomass production, redox state, and survival in rapidly proliferating tumor cells. Intermediates: serine-glycine biosynthesis; glutamine uptake; one-carbon metabolism
Tumor Cell Proliferation and Survival -> Soft Tissue Mass / Localized Swelling INDIRECT KNOWN INTERMEDIATES Sustained proliferation and impaired differentiation produce the expanding local tumor mass. Intermediates: expansion of poorly differentiated malignant cells
Deep research
OpenScientist citations 50 citations 2026-05-28T12:05:36.809795
Show evidence (4 references)
PMID:25453903 SUPPORT In Vitro
"EWS-FLI1 establishes an oncogenic regulatory program governing both tumor"
Supports the canonical fusion enhanceropathy model.
PMID:41659683 SUPPORT In Vitro
"forms dynamic, sub-diffraction-limit hubs with mechanisms of dissolution that"
Supports dynamic endogenous EWS-FLI1 hub formation as a refinement of the canonical model.
PMID:23178492 SUPPORT In Vitro
"the repressive function of EWS/FLI is absolutely required for the oncogenic function"
Supports including direct transcriptional repression in the canonical mechanism.
+ 1 more reference
Permissive developmental cell-of-origin model
cell_of_origin_context_model EMERGING
EWS-FLI1 transformation depends on developmental timing, progenitor state, inherited GGAA repeat architecture, and cooperating developmental signals. Neural crest-related and embryonic mesenchymal progenitors are leading candidates, and IGF-1/YAP1 signaling is a new non-genetic cooperating mechanism, but the decisive human chromatin and differentiation-state features remain unresolved.
Pathograph links
GGAA Microsatellite Germline Susceptibility Architecture -> GGAA Microsatellite Enhancer Reprogramming DIRECT Germline GGAA repeat length and purity alter the strength of EWS-FLI1 neo-enhancer formation at susceptible loci.
GGAA Microsatellite Germline Susceptibility Architecture -> Tumor Cell Proliferation and Survival INDIRECT KNOWN INTERMEDIATES Susceptibility-locus enhancer activation can increase expression of proliferation-associated transcriptional regulators. Intermediates: EGR2 enhancer activation; RREB1-mediated RAS/MAPK-associated transcription
Permissive Progenitor Cell State -> EWS-FLI1 Fusion Oncogene INDIRECT UNKNOWN INTERMEDIATES The progenitor chromatin state is hypothesized to determine whether EWS-FLI1 expression is tolerated and can initiate an Ewing-like program.
Permissive Progenitor Cell State -> GGAA Microsatellite Enhancer Reprogramming INDIRECT UNKNOWN INTERMEDIATES Developmental chromatin context may determine which GGAA microsatellites become functional EWS-FLI1 enhancers.
Permissive Progenitor Cell State -> IGF-1/YAP1 Developmental Cooperation INDIRECT KNOWN INTERMEDIATES Growth-factor signaling in a permissive mesenchymal developmental window may convert EWS-FLI1 expression from toxic or malformed development into stable malignant transformation. Intermediates: pubertal IGF-1 exposure; YAP1/TEAD transcriptional signaling
IGF-1/YAP1 Developmental Cooperation -> Tumor Cell Proliferation and Survival INDIRECT KNOWN INTERMEDIATES IGF-1/YAP1 signaling can cooperate with EWS-FLI1 to promote stable transformation and tumorigenicity in a developmental mesenchymal context. Intermediates: YAP1/TEAD transcriptional activity; stable transformation of EWS-FLI1-mutant mesenchymal cells
IGF-1/YAP1 Developmental Cooperation -> Blocked Differentiation INDIRECT UNKNOWN INTERMEDIATES The developmental signaling state may help lock EWS-FLI1-expressing progenitors into an aberrant fate rather than normal mesenchymal differentiation.
Deep research
OpenScientist citations 46 citations 2026-05-28T12:54:01.089018
Show evidence (3 references)
PMID:41136396 SUPPORT In Vitro
"is able to endow transforming capacity when expressed in undifferentiated, early"
Supports the developmental-context hypothesis in embryonic mesenchymal stem cells.
PMID:40080499 SUPPORT Model Organism
"concentrations mimicking serum levels during puberty"
Supports IGF-1/YAP1 signaling as a developmental cooperating mechanism.
PMID:36787739 SUPPORT Human Clinical
"germline microsatellite variation at the 6p25.1 EwS"
Supports inherited GGAA microsatellite architecture as part of the permissive-context model.
Transcription-coupled replication stress vulnerability model
replication_stress_vulnerability_model ALTERNATIVE
EWS-FLI1-induced transcription creates R-loops, replication stress, and BRCA1-linked repair defects. The model is best represented as a superimposed vulnerability framework with DHX9-dependent R-loop resolution, direct SLFN11 activation and fork blocking, USP1-survivin stress buffering, and possible repair-pathway defects. These arms may explain sensitivity to genotoxic therapy and resistance adaptation.
Pathograph links
EWS-FLI1 Fusion Oncogene -> ATF4-Serine-Glycine Metabolic Reprogramming DIRECT EWS-FLI1 directly activates ATF4 and metabolic stress-response programs.
EWS-FLI1 Fusion Oncogene -> Replication Stress and Impaired Homologous Recombination INDIRECT KNOWN INTERMEDIATES Fusion-driven transcriptional stress produces R-loops, replication stress, and BRCA1-linked homologous-recombination defects. Intermediates: high-output transcription; R-loop accumulation
EWS-FLI1 Fusion Oncogene -> R-loop Resolution and Replication-Fork Vulnerability DIRECT EWS-FLI1 can amplify replication stress through DHX9 sequestration and through transcriptional activation of SLFN11-dependent fork-blocking responses to DNA-targeted therapy.
NuRD/CHD4 Repressive Chromatin Program -> Tumor Cell Proliferation and Survival INDIRECT KNOWN INTERMEDIATES CHD4/NuRD dependence links the transcriptional pathograph to DNA-damage buffering and tumor cell survival. Intermediates: CHD4-dependent chromatin architecture maintenance; suppression of spontaneous DNA damage
Replication Stress and Impaired Homologous Recombination -> Tumor Cell Proliferation and Survival INDIRECT KNOWN INTERMEDIATES Replication stress creates a survival bottleneck that Ewing sarcoma cells can buffer through USP1-survivin signaling. Intermediates: USP1-driven survivin stabilization; suppression of replication-stress-induced apoptosis
R-loop Resolution and Replication-Fork Vulnerability -> Replication Stress and Impaired Homologous Recombination DIRECT DHX9 sequestration increases unresolved R-loops, and SLFN11 blocks fork progression when replication is stressed.
R-loop Resolution and Replication-Fork Vulnerability -> Tumor Cell Proliferation and Survival UNKNOWN The same R-loop and fork-blocking state can increase treatment sensitivity or select resistant cells with altered DHX9 or SLFN11 activity.
STAG2-Modified Enhancer State -> Replication Stress and Impaired Homologous Recombination INDIRECT KNOWN INTERMEDIATES STAG2 loss can compound the fusion-driven DNA-damage state through replication-fork and homologous-recombination vulnerabilities. Intermediates: replication fork stalling; homologous-recombination impairment
Tumor Cell Proliferation and Survival -> Metastatic Disease UNKNOWN Which survival and stress-adaptation states drive dissemination and relapse remains incompletely resolved.
Deep research
OpenScientist citations 33 citations 2026-05-28T13:31:43.663508
Show evidence (3 references)
PMID:29513652 SUPPORT In Vitro
"mechanistic basis of the sensitivity of Ewing sarcoma to chemotherapy (including"
Supports the replication-stress vulnerability model.
PMID:40721661 SUPPORT In Vitro
"sequestering DHX9 helicase, ultimately resulting in"
Supports the DHX9-dependent R-loop arm of the vulnerability model.
PMID:25779942 SUPPORT In Vitro
"EWS-FLI1 binds near the transcription start site of SLFN11 promoter"
Supports direct EWS-FLI1 activation of SLFN11 within this vulnerability model.
STAG2/cohesin-modified high-risk enhancer model
cohesin_modified_high_risk_model EMERGING
STAG2 loss modifies the canonical EWS-FLI1 pathograph by altering cohesin architecture, enhancer-promoter contacts, PRC2/CTCF-regulated chromatin states, and possibly replication-fork repair stress. The leading model is selective amplification of multimeric GGAA enhancer output in a high-risk subset. This model is qualified by unresolved enhancer-versus-PRC2-versus-DDR mechanisms and by population-specific clinical effects: the COG Western-cohort STAG2 protein-loss prognostic association has not replicated uniformly, including a Japanese comprehensive genomic profiling cohort in which STAG2 mutation frequency was lower and CDKN2A/B deletions were prognostic instead.
Pathograph links
GGAA Microsatellite Enhancer Reprogramming -> STAG2-Modified Enhancer State INDIRECT KNOWN INTERMEDIATES STAG2 loss reshapes EWS-FLI1 occupancy across monomeric and multimeric GGAA-repeat enhancer classes. Intermediates: cohesin-dependent enhancer-promoter contacts
STAG2-Modified Enhancer State -> GGAA Microsatellite Enhancer Reprogramming DIRECT STAG2/cohesin status changes enhancer-promoter communication at long EWS-FLI1-bound GGAA repeats and rewires enhancer output.
STAG2-Modified Enhancer State -> Replication Stress and Impaired Homologous Recombination INDIRECT KNOWN INTERMEDIATES STAG2 loss can compound the fusion-driven DNA-damage state through replication-fork and homologous-recombination vulnerabilities. Intermediates: replication fork stalling; homologous-recombination impairment
STAG2-Modified Enhancer State -> Metastatic Disease INDIRECT KNOWN INTERMEDIATES STAG2 loss can promote an aggressive, metastasis-prone transcriptional state. Intermediates: altered enhancer-promoter contacts; PRC2 derepression; migratory and neurodevelopmental program rewiring
Tumor Cell Proliferation and Survival -> Metastatic Disease UNKNOWN Which survival and stress-adaptation states drive dissemination and relapse remains incompletely resolved.
Deep research
OpenScientist citations 32 citations 2026-05-28T14:12:55.507949
Show evidence (4 references)
PMID:41950086 SUPPORT In Vitro
"oncogenic transcriptional state in Ewing sarcoma."
Supports the STAG2-modified high-risk enhancer model.
PMID:39487368 SUPPORT In Vitro
"cohesin-STAG2 facilitates communication between"
Supports STAG2-dependent enhancer-promoter communication at long GGAA repeats.
PMID:36221002 SUPPORT Human Clinical
"5-year event-free survival was 54% (95% CI 34-70%) and"
Supports the high-risk clinical association for STAG2 protein loss.
+ 1 more reference
?

Discussions and Knowledge Gaps

5
Which human progenitor state is truly permissive for EWS-FLI1 transformation, and what chromatin or differentiation-state features distinguish transforming early mesenchymal or neural crest-like cells from non-transforming MSC states?
KNOWLEDGE GAP OPEN gap_ewing_cell_of_origin_context
Attached to
pathophysiology#Permissive Progenitor Cell State pathophysiology#IGF-1/YAP1 Developmental Cooperation pathophysiology#GGAA Microsatellite Germline Susceptibility Architecture pathophysiology#EWS-FLI1 Fusion Oncogene pathophysiology#GGAA Microsatellite Enhancer Reprogramming
Neural crest-derived cells, bone marrow-derived MSCs, pediatric MSCs, adult MSCs, and 2025 embryonic MSC models support overlapping but not identical origin hypotheses. The unresolved mechanism is not simply whether EWS-FLI1 can alter transcription, but which developmental chromatin state lets GGAA enhancer rewiring become transforming rather than toxic, senescent, or differentiation-inducing. IGF-1/YAP1 signaling and germline GGAA repeat architecture now provide concrete cooperating mechanisms, but neither yet defines the full permissive human progenitor state.
Proposed experiments
Isogenic developmental-context EWS-FLI1 induction panel
isogenic stem-cell transformation assay
exp_ewing_isogenic_developmental_context_panel
Build an inducible or safe-harbor knock-in EWS-FLI1 panel across hPSC-derived migratory neural crest cells, early mesenchymal progenitors, osteochondral progenitors, pediatric MSCs, and adult MSCs. Measure the same fusion dose and timing across lineages, then compare enhancer activation, differentiation blockade, DNA-damage state, senescence, and xenograft or organoid tumorigenicity.
Model systems
hPSC-derived neural crest and early mesenchymal progenitor panel
Genome-engineered human pluripotent stem cell derivatives with matched EWS-FLI1 induction across candidate Ewing sarcoma cells of origin.
IPSC DERIVED MODEL PMID:41136396 link
human NCBITaxon:9606
migratory neural crest cell CL:0000333 early mesenchymal stem cell CL:0000134
Perturbations
Inducible EWS-FLI1 expression
pathophysiology#EWS-FLI1 Fusion Oncogene
Express matched EWS-FLI1 at controlled dose and timing across candidate progenitor states.
EWSR1 hgnc:3508 FLI1 hgnc:3749
Pubertal IGF-1/YAP1 modulation
pathophysiology#IGF-1/YAP1 Developmental Cooperation
Add pubertal-range IGF-1 exposure and YAP1/TEAD inhibition or knockout arms to determine whether the cooperating signal is conserved in human progenitors.
IGF1 hgnc:5464 YAP1 hgnc:16262
Readouts
GGAA enhancer activation by developmental state
pathophysiology#GGAA Microsatellite Enhancer Reprogramming
Compare EWS-FLI1 occupancy, chromatin accessibility, and H3K27ac gain at endogenous GGAA microsatellites.
chromatin remodeling GO:0006338
single-cell ATAC-seq CUT&Tag single-cell RNA-seq
Direction: POSITIVE
Transformation and differentiation blockade
pathophysiology#Blocked Differentiation
Measure loss of mesenchymal/osteochondral differentiation capacity, acquisition of Ewing-like transcription, senescence avoidance, and tumor formation in permissive contexts.
mesenchymal cell differentiation GO:0048762
differentiation assay xenograft tumorigenicity assay
Direction: NEGATIVE
Controls
Isogenic uninduced progenitor controls
Same genetic background and differentiation state without EWS-FLI1 induction.
Nonpermissive adult MSC comparator
Mature MSC context expected to show incomplete transformation or toxicity.
Fusion knockdown or degron rescue
Acute EWS-FLI1 withdrawal after Ewing-like state acquisition.
Decision criterion
The cell-of-origin model is prioritized when a specific progenitor state reproducibly shows EWS-FLI1-dependent GGAA enhancer activation, Ewing-like core regulatory circuitry, differentiation blockade, and tumorigenicity while closely related states fail one or more of those criteria.
Would support
pathophysiology#Permissive Progenitor Cell State pathophysiology#IGF-1/YAP1 Developmental Cooperation pathophysiology#GGAA Microsatellite Enhancer Reprogramming pathophysiology#Blocked Differentiation
Would refute
pathophysiology#Permissive Progenitor Cell State
Show evidence (2 references)
PMID:41136396 SUPPORT In Vitro
"mesenchymal stem cells (heMSCs) results in the acquisition of an ES"
Supports the feasibility and rationale for testing early human mesenchymal contexts.
PMID:21559395 SUPPORT In Vitro
"similar to hNCSC than any other normal tissue, including MSC, indicating that"
Supports including neural crest-derived progenitors in the comparative panel.
Show evidence (3 references)
PMID:41136396 SUPPORT In Vitro
"whose cellular origin remains unclear."
Directly states the knowledge gap.
PMID:40080499 SUPPORT Model Organism
"concentrations mimicking serum levels during puberty"
Supports adding IGF-1/YAP1 as a concrete cooperating mechanism that still needs human validation.
PMID:36787739 SUPPORT Human Clinical
"had longer alleles (>135"
Supports inherited GGAA architecture as part of the permissive-context gap.
What GGAA microsatellite grammar and cofactor context make EWS-FLI1 binding oncogenic, and why do ETV6, BAF, and STAG2/cohesin perturbations produce different enhancer and differentiation outcomes?
KNOWLEDGE GAP OPEN gap_ewing_ggaa_enhancer_grammar
Attached to
pathophysiology#EWS-FLI1 Hub and Dosage Control pathophysiology#BAF Complex Retargeting pathophysiology#GGAA Microsatellite Enhancer Reprogramming pathophysiology#ETV6 GGAA Counter-Regulation pathophysiology#GGAA Microsatellite Germline Susceptibility Architecture pathophysiology#STAG2-Modified Enhancer State
EWS-FLI1 binds GGAA repeats, but binding alone does not explain why some microsatellites become oncogenic enhancers, why germline repeat length at EGR2 and RREB1 changes susceptibility, why ETV6 antagonism can redirect occupancy toward differentiation, or why STAG2 loss selectively amplifies multimeric GGAA enhancer programs. This gap is the enhancer-grammar layer of the pathograph, now spanning DNA sequence, hub dosage, native ETS competition, and cohesin state.
Proposed experiments
Endogenous GGAA enhancer grammar saturation editing
pooled endogenous enhancer saturation editing experiment
exp_ewing_endogenous_ggaa_saturation_editing
Use multiplex prime/base editing or CRISPR replacement to vary repeat length, repeat purity, flanking ETS motifs, and local chromatin context at endogenous EWS-FLI1-bound GGAA microsatellites. Combine these edits with acute BAF, ETV6, and STAG2 perturbations to quantify how enhancer grammar and cofactor state determine transcriptional output.
Model systems
Ewing sarcoma cell-line and early progenitor enhancer-editing panel
EWS-FLI1-positive Ewing sarcoma cell lines plus permissive progenitor models with editable endogenous GGAA microsatellite enhancers.
CELL LINE PMID:41950086 link
human NCBITaxon:9606
Perturbations
GGAA microsatellite sequence editing
pathophysiology#GGAA Microsatellite Enhancer Reprogramming
Edit endogenous EWS-FLI1-bound GGAA repeats across short, intermediate, and long repeat classes, including susceptibility alleles at EGR2 and RREB1.
EGR2 hgnc:3239 RREB1 hgnc:10449
ETV6, STAG2, and BAF cofactor perturbation
pathophysiology#BAF Complex Retargeting
Combine enhancer edits with degron, CRISPRi, or knockout perturbations of ETV6, STAG2, and BAF complex activity.
ETV6 hgnc:3495 STAG2 hgnc:11355
Readouts
Enhancer occupancy and activity
pathophysiology#GGAA Microsatellite Enhancer Reprogramming
Quantify EWS-FLI1 occupancy, BAF recruitment, chromatin accessibility, H3K27ac, enhancer-promoter contact, and target-gene transcription for each edited enhancer allele.
regulation of gene expression GO:0010468
CUT&Tag ATAC-seq HiChIP single-cell RNA-seq
Direction: POSITIVE
Differentiation versus proliferation outcome
pathophysiology#Core Regulatory Circuitry Activation
Determine whether edited enhancer states reinforce Ewing core regulatory circuitry, drive mesenchymal differentiation, or reduce tumor cell growth.
cell population proliferation GO:0008283
pooled growth screen differentiation marker profiling
Direction: POSITIVE
Controls
Synonymous non-GGAA neutral edits
Editing controls matched for guide delivery and repair outcome.
EWS-FLI1 degron withdrawal
Fusion-dependence control for edited enhancer activity.
Decision criterion
A causal enhancer-grammar rule is supported when endogenous repeat edits produce predictable EWS-FLI1 occupancy, BAF recruitment, enhancer-promoter contact, and transcriptional changes that reverse with fusion withdrawal and change coherently under ETV6 or STAG2 perturbation.
Would support
pathophysiology#GGAA Microsatellite Enhancer Reprogramming pathophysiology#BAF Complex Retargeting pathophysiology#STAG2-Modified Enhancer State
Would refute
pathophysiology#STAG2-Modified Enhancer State
Show evidence (2 references)
PMID:36658219 SUPPORT In Vitro
"with EWS-FLI1 for binding to select DNA elements enriched for short GGAA repeat"
Supports testing ETV6 as an enhancer-grammar modifier.
PMID:41950086 SUPPORT In Vitro
"activity at multimeric microsatellite enhancers."
Supports testing repeat-length-dependent STAG2 effects.
Show evidence (4 references)
PMID:25453903 SUPPORT In Vitro
"induce chromatin opening and create de novo enhancers that physically interact"
Establishes the enhancer phenomenon whose causal sequence rules remain unresolved.
PMID:26214589 SUPPORT In Vitro
"A risk allele connected adjacent GGAA repeats by"
Supports germline repeat architecture as a testable enhancer-grammar variable.
PMID:36787739 SUPPORT Human Clinical
"50 microsatellite alleles at 6p25.1 and observed"
Supports long-read resolution of germline GGAA alleles as part of the enhancer-grammar gap.
+ 1 more reference
Which EWS-FLI1-dependent chromatin-accessibility states are causal tumor dependencies rather than passenger signatures, and can an automated high-throughput chromatin assay distinguish therapeutically useful chromatin reversal from nonspecific cytotoxicity?
KNOWLEDGE GAP OPEN gap_ewing_chromatin_reversal_screen
Attached to
pathophysiology#EWS-FLI1 Fusion Oncogene pathophysiology#EWS-FLI1 Hub and Dosage Control pathophysiology#GGAA Microsatellite Enhancer Reprogramming pathophysiology#ETV6 GGAA Counter-Regulation pathophysiology#NuRD/CHD4 Repressive Chromatin Program pathophysiology#Core Regulatory Circuitry Activation
Ian Davis lab work showed that EWS-FLI1 retargets chromatin, creates nucleosome-depleted enhancer states, and can be assayed with automated high-throughput FAIRE. However, the therapeutic interpretation remains unresolved: a compound or degrader that reduces an Ewing chromatin signature could act by direct fusion-pathway reversal, by ETV6 or NuRD/HDAC/LSD1 modifier biology, by reduced EWS-FLI1 expression, or by general toxicity. A mechanism-resolved chromatin perturbation screen would convert this chromatin phenotype into a decision rule for prioritizing causal nodes and cloud-lab-ready follow-up experiments.
Proposed experiments
Automated EWS-FLI1 chromatin-reversal perturbation screen
automated high-throughput chromatin-accessibility perturbation screen
exp_ewing_automated_chromatin_reversal_screen
Run an automated plate-based chromatin-accessibility screen in Ewing sarcoma models using HT-FAIRE, ATAC-qPCR, or low-input ATAC-seq readouts at sentinel EWS-FLI1 GGAA enhancers, ETV6-competed short GGAA elements, and repressed mesenchymal enhancers. Screen annotated epigenetic compounds, targeted degraders, kinase/chemical-probe libraries, and EWS-FLI1 or ETV6 perturbation controls, then triage hits by matched viability, fusion expression, enhancer activity, and transcriptional rescue.
Model systems
Ewing sarcoma chromatin-accessibility screening panel
EWS-FLI1-positive Ewing sarcoma cell lines with sentinel GGAA enhancers and matched orthogonal chromatin, expression, and viability assays.
CELL LINE PMID:26929321 link
human NCBITaxon:9606
Perturbations
Epigenetic compound and degrader library
pathophysiology#GGAA Microsatellite Enhancer Reprogramming
Apply annotated epigenetic inhibitors, targeted degraders, and chemical probe libraries with dose and time gradients suitable for automated liquid handling.
EWS-FLI1 and ETV6 perturbation controls
pathophysiology#EWS-FLI1 Fusion Oncogene
Include acute fusion knockdown or degron withdrawal, ETV6 degradation or knockdown, and vehicle controls to calibrate chromatin-reversal directionality.
EWSR1 hgnc:3508 FLI1 hgnc:3749 ETV6 hgnc:3495
Readouts
Sentinel chromatin-accessibility reversal
pathophysiology#GGAA Microsatellite Enhancer Reprogramming
Quantify accessibility at EWS-FLI1-activated GGAA enhancers, ETV6- competed short GGAA elements, and fusion-repressed mesenchymal enhancers.
chromatin remodeling GO:0006338
HT-FAIRE ATAC-qPCR low-input ATAC-seq
Direction: NEGATIVE
Mechanism-resolved transcriptional rescue
pathophysiology#Core Regulatory Circuitry Activation
Pair chromatin hits with targeted RNA-seq or Perturb-seq to determine whether KLF15/TCF4/NKX2-2 circuitry, mesenchymal differentiation genes, EWS-FLI1 abundance, or generic stress pathways explain the response.
regulation of gene expression GO:0010468
targeted RNA-seq Perturb-seq immunoblotting
Direction: NEGATIVE
Growth and toxicity separation
pathophysiology#Tumor Cell Proliferation and Survival
Measure viability, apoptosis, and clonogenic growth in the same dose and time grid to separate mechanism-specific chromatin reversal from nonspecific cytotoxicity.
cell population proliferation GO:0008283
viability assay apoptosis assay clonogenic survival assay
Direction: NEGATIVE
Controls
EWS-FLI1 knockdown positive control
Calibrates the expected chromatin-accessibility direction for true fusion-pathway reversal.
Short-exposure viability control
Flags compounds whose chromatin signal is secondary to acute cell loss or global toxicity.
Non-Ewing sarcoma comparator cells
Tests whether hits reverse a Ewing-specific chromatin state rather than general chromatin accessibility.
Decision criterion
A chromatin-reversal hit is prioritized when it reproducibly shifts sentinel EWS-FLI1 accessibility and transcription toward the fusion- withdrawal state at concentrations and times that precede broad cytotoxicity, and when the response maps to a declared mechanism node such as ETV6 competition, NuRD/HDAC/LSD1 repression, or EWS-FLI1 dosage.
Would support
pathophysiology#GGAA Microsatellite Enhancer Reprogramming pathophysiology#ETV6 GGAA Counter-Regulation pathophysiology#NuRD/CHD4 Repressive Chromatin Program pathophysiology#Tumor Cell Proliferation and Survival
Would refute
pathophysiology#GGAA Microsatellite Enhancer Reprogramming pathophysiology#ETV6 GGAA Counter-Regulation
Show evidence (3 references)
PMID:26929321 SUPPORT In Vitro
"high-throughput, automated assay."
Supports the feasibility of automated chromatin-accessibility screening in this disease context.
PMID:26929321 SUPPORT In Vitro
"regions of aberrant nucleosome"
Supports using EWS-FLI1-dependent accessibility regions as the primary assay signal.
+ 1 more reference
Show evidence (2 references)
PMID:22086061 SUPPORT In Vitro
"EWS-FLI chimera acquired chromatin-altering activity"
Establishes the EWS-FLI1 chromatin-altering phenomenon that motivates the knowledge gap.
PMID:26929321 SUPPORT In Vitro
"does not depend on the a priori selection of a single molecular target"
Supports chromatin-signature screening as a target-agnostic route to mechanism discovery.
Which EWS-FLI1-induced DHX9/R-loop, SLFN11 fork-blocking, BRCA1, STAG2, and USP1-survivin states determine whether replication stress causes chemosensitivity, PARP/USP1/ATR inhibitor vulnerability, or survival and relapse?
KNOWLEDGE GAP OPEN gap_ewing_replication_stress_response
Attached to
pathophysiology#R-loop Resolution and Replication-Fork Vulnerability pathophysiology#Replication Stress and Impaired Homologous Recombination pathophysiology#STAG2-Modified Enhancer State pathophysiology#Tumor Cell Proliferation and Survival treatment#Neoadjuvant Chemotherapy
Ewing sarcoma is sensitive to genotoxic chemotherapy, and EWS-FLI1 creates R-loops, replication stress, SLFN11-dependent fork blocking, and homologous-recombination defects. However, high-risk and relapsed tumors survive therapy, and it is not yet clear which molecular stress-state measurements predict response to PARP, ATR, USP1, or chemotherapy combinations.
Proposed experiments
Replication-stress pharmacodynamic response panel
perturbation-response pharmacodynamic experiment
exp_ewing_replication_stress_pharmacodynamic_panel
Profile matched diagnosis-relapse samples, patient-derived cultures, and Ewing sarcoma cell lines under etoposide, doxorubicin, PARP inhibition, USP1 inhibition, and combinations. Perturb EWS-FLI1, DHX9, SLFN11, BRCA1, USP1, and BIRC5 to separate primary fusion-induced stress, fork blocking, and survival adaptation.
Model systems
Matched Ewing sarcoma patient-derived culture and cell-line panel
Human Ewing sarcoma cultures and cell lines stratified by therapy response, STAG2 status, and replication-stress markers.
PRIMARY CELL CULTURE PMID:37478161 link
human NCBITaxon:9606
Perturbations
Genotoxic and targeted stress perturbation
pathophysiology#Replication Stress and Impaired Homologous Recombination
Compare standard genotoxic agents with PARP and USP1 inhibition under fusion knockdown or repair/survival gene perturbation.
DHX9 hgnc:2750 SLFN11 hgnc:26633 BRCA1 hgnc:1100 USP1 hgnc:12607 BIRC5 hgnc:593
Readouts
R-loop, fork-blocking, and homologous-recombination response
pathophysiology#R-loop Resolution and Replication-Fork Vulnerability
Measure R-loop burden, DHX9 occupancy, SLFN11 chromatin recruitment, replication fork stress, gamma-H2AX, RAD51 foci, BRCA1 localization, and transcription-coupled DNA damage after treatment.
double-strand break repair via homologous recombination GO:0000724
DRIP-seq DNA fiber assay immunofluorescence DNA repair foci assay
Direction: NEGATIVE
Cell survival under replication stress
pathophysiology#Tumor Cell Proliferation and Survival
Quantify apoptosis, clonogenic survival, and drug synergy across chemotherapy, PARP inhibition, and USP1 inhibition.
cell population proliferation GO:0008283
clonogenic survival assay apoptosis assay
Direction: NEGATIVE
Controls
EWS-FLI1 knockdown or degron control
Tests whether replication-stress markers are fusion-dependent.
Isogenic USP1 or BIRC5 rescue
Separates USP1-survivin survival adaptation from upstream R-loop burden.
Decision criterion
A predictive stress-state model is supported when baseline or early treatment-induced R-loop/BRCA1/USP1-survivin readouts reproducibly predict death, survival, or drug synergy across independent patient-derived models and are reversed by the corresponding genetic rescue or withdrawal.
Would support
pathophysiology#R-loop Resolution and Replication-Fork Vulnerability pathophysiology#Replication Stress and Impaired Homologous Recombination pathophysiology#Tumor Cell Proliferation and Survival
Would refute
pathophysiology#Replication Stress and Impaired Homologous Recombination
Show evidence (4 references)
PMID:29513652 SUPPORT In Vitro
"etoposide, but the underlying molecular basis of this sensitivity is unclear."
Supports the unresolved response-mechanism framing.
PMID:37478161 SUPPORT In Vitro
"USP1 inhibition sensitizes cells to doxorubicin and etoposide treatment."
Supports USP1 as a testable stress-survival target.
+ 2 more references
Show evidence (2 references)
PMID:37478161 SUPPORT In Vitro
"override activation of apoptosis or cellular senescence in response to increased"
Directly states the survival-under-replication-stress knowledge gap.
PMID:40721661 SUPPORT In Vitro
"excessive DHX9 or reduced EWS::FLI1 levels render"
Supports unresolved resistance prediction involving DHX9 and fusion dosage.
In STAG2-altered Ewing sarcoma, which causal arm best explains high-risk disease: multimeric GGAA enhancer amplification, PRC2/CTCF chromatin rewiring, replication-fork repair vulnerability, or a context-specific combination of these mechanisms?
KNOWLEDGE GAP OPEN gap_ewing_stag2_cohesin_high_risk_mechanism
Attached to
pathophysiology#STAG2-Modified Enhancer State pathophysiology#GGAA Microsatellite Enhancer Reprogramming pathophysiology#R-loop Resolution and Replication-Fork Vulnerability pathophysiology#Replication Stress and Impaired Homologous Recombination phenotype#Metastatic Disease
The reviewed literature supports that STAG2 loss reshapes GGAA enhancer-promoter contacts and is clinically adverse, but the mechanism is not a single clean edge. EWS-FLI1-dependent long-GGAA contacts, EWS-FLI1- independent CTCF changes, PRC2 derepression, TP53 co-alteration, and replication-fork stress could each contribute differently across cohorts, ancestry backgrounds, and treatment states.
Proposed experiments
STAG2-stratified primary-tumor chromatin and DDR atlas
STAG2-stratified multi-omic mechanism atlas
exp_ewing_stag2_primary_tumor_chromatin_ddr_atlas
Profile STAG2-positive and STAG2-negative primary and relapse Ewing sarcoma specimens with matched WGS, long-read GGAA microsatellite typing, RNA-seq, ATAC-seq or CUT&Tag, H3K27ac/H3K27me3, CTCF/cohesin occupancy, and DNA-damage response markers. Pair the tumor atlas with isogenic STAG2 rescue or knockout in Ewing sarcoma cultures to separate enhancer, PRC2/CTCF, and replication-stress arms.
Model systems
STAG2-positive and STAG2-negative Ewing sarcoma tumor cohort
Banked diagnostic and relapse Ewing sarcoma tumors with STAG2 protein status, mutation calls, clinical outcome, and ancestry-aware GGAA repeat genotyping.
OTHER PMID:36221002 link
human NCBITaxon:9606
Perturbations
STAG2 rescue or knockout
pathophysiology#STAG2-Modified Enhancer State
Restore STAG2 in STAG2-deficient Ewing sarcoma models and remove STAG2 in matched STAG2-proficient models while stratifying by TP53 status.
STAG2 hgnc:11355
Readouts
Enhancer, PRC2, and CTCF arm partition
pathophysiology#STAG2-Modified Enhancer State
Quantify EWS-FLI1 occupancy at short and long GGAA repeats, enhancer-promoter contacts, H3K27ac, H3K27me3, CTCF loops, and neurodevelopmental or migratory target-gene expression.
chromosome organization GO:0051276
long-read microsatellite genotyping Capture Hi-C ATAC-seq CUT&Tag
Direction: POSITIVE
Replication-fork and repair-stress response
pathophysiology#Replication Stress and Impaired Homologous Recombination
Measure DNA fiber fork progression, gamma-H2AX, RAD51 foci, PARP/ATR inhibitor response, and chemotherapy response by STAG2 state.
DNA replication GO:0006260
DNA fiber assay immunofluorescence DNA repair foci assay drug-response matrix
Direction: NEGATIVE
Controls
STAG2-wild-type matched tumors
Stage-, site-, age-, and ancestry-matched tumors retaining STAG2 expression.
Isogenic rescue controls
STAG2 restoration or knockout controls that separate STAG2 effects from cell-line background.
Decision criterion
The STAG2 high-risk model is strengthened if STAG2-negative primary tumors reproduce long-GGAA enhancer amplification and if isogenic rescue reverses the predicted enhancer, PRC2/CTCF, or DDR arm. A single dominant arm would be prioritized only if it predicts clinical outcome and drug response better than the alternatives.
Would support
pathophysiology#STAG2-Modified Enhancer State pathophysiology#GGAA Microsatellite Enhancer Reprogramming pathophysiology#Replication Stress and Impaired Homologous Recombination
Would refute
pathophysiology#STAG2-Modified Enhancer State
Show evidence (2 references)
PMID:39487368 SUPPORT In Vitro
"cohesin-STAG2 facilitates communication between"
Supports measuring STAG2-dependent long-GGAA enhancer-promoter contacts.
PMID:36221002 SUPPORT Human Clinical
"carries a poor prognosis."
Supports the need for primary-tumor clinical stratification by STAG2 loss.
Show evidence (3 references)
PMID:39487368 SUPPORT In Vitro
"Changes in CTCF-dependent chromatin contacts involving"
Supports the unresolved CTCF arm of the STAG2 mechanism.
PMID:36221002 SUPPORT Human Clinical
"carries a poor prognosis."
Supports STAG2 protein loss as a clinically meaningful high-risk state.
PMID:25223734 SUPPORT Human Clinical
"STAG2 mutations and CDKN2A deletions were mutually exclusive"
Supports the need to stratify STAG2 effects against other high-risk genomic routes.
⚙

Pathophysiology

16
EWS-FLI1 Fusion Oncogene
The t(11;22)(q24;q12) translocation fuses the EWS gene (EWSR1) on chromosome 22 with the FLI1 gene on chromosome 11. The resulting EWS-FLI1 protein functions as an aberrant FET-ETS transcription factor. It is the truncal driver of most Ewing sarcomas, but its oncogenic effect depends on a permissive developmental cell state and on downstream enhancer, transcriptional, metabolic, and DNA damage-response programs.
Canonical EWS-FLI1 fusion enhanceropathy model Transcription-coupled replication stress vulnerability model
mesenchymal stem cell CL:0000134
EWSR1 hgnc:3508 FLI1 hgnc:3749
positive regulation of transcription by RNA polymerase II GO:0045944 ⚠ ABNORMAL
bone tissue UBERON:0002481
Experimental models
Ewing sarcoma tumor organoid model systems ORGANOID Models fusion-positive tumor biology in a 3D non-animal context.
Patient-derived Ewing sarcoma culture panel PRIMARY CELL CULTURE Models EWSR1 fusion-positive tumor state in patient-derived cultures.
Human embryonic mesenchymal stem cell EWS-FLI1 transformation model PRIMARY CELL CULTURE Models EWS-FLI1 oncogene expression in an embryonic human mesenchymal developmental context, with xenograft tumor formation demonstrating transformation capacity.
Downstream
EWS-FLI1 Hub and Dosage Control Endogenous EWS-FLI1 forms dynamic low-complexity-domain-dependent chromatin hubs, and tumor behavior is sensitive to both excessive and submaximal fusion protein activity. Canonical EWS-FLI1 fusion enhanceropathy model
BAF Complex Retargeting The EWSR1-derived low-complexity domain enables EWS-FLI1 to recruit BAF chromatin-remodeling complexes to tumor-specific enhancers. Canonical EWS-FLI1 fusion enhanceropathy model
GGAA Microsatellite Enhancer Reprogramming EWS-FLI1 occupies GGAA microsatellite repeats and canonical ETS sites, creating de novo enhancers while repressing other enhancer classes. Canonical EWS-FLI1 fusion enhanceropathy model
NuRD/CHD4 Repressive Chromatin Program EWS-FLI1 has a direct repressive arm involving NuRD-associated chromatin machinery, including CHD4 and LSD1/HDAC activity, in addition to its enhancer-activation arm. Canonical EWS-FLI1 fusion enhanceropathy model
Blocked Differentiation Fusion-driven transcriptional repression and downstream transcription factors suppress mesenchymal differentiation programs. Canonical EWS-FLI1 fusion enhanceropathy model
ATF4-Serine-Glycine Metabolic Reprogramming EWS-FLI1 directly activates ATF4 and metabolic stress-response programs. Canonical EWS-FLI1 fusion enhanceropathy model Transcription-coupled replication stress vulnerability model
Replication Stress and Impaired Homologous Recombination Fusion-driven transcriptional stress produces R-loops, replication stress, and BRCA1-linked homologous-recombination defects. Transcription-coupled replication stress vulnerability model
R-loop Resolution and Replication-Fork Vulnerability EWS-FLI1 can amplify replication stress through DHX9 sequestration and through transcriptional activation of SLFN11-dependent fork-blocking responses to DNA-targeted therapy. Transcription-coupled replication stress vulnerability model
Show evidence (3 references)
PMID:33741715 PARTIAL In Vitro
"Ewing sarcomas are driven by EWS-ETS fusions, most commonly EWS-FLI1"
This supports EWS-FLI1 as a key driver fusion in Ewing sarcoma, but not all specific structural details in the descriptor.
PMID:17250957 SUPPORT
"It is associated in 85% of cases with the"
Directly supports the 85% frequency of EWS-FLI1 translocation and its structural details.
PMID:17250957 SUPPORT
"resulting EWS-FLI-1 fusion protein is believed to behave as an aberrant"
Supports the role of EWS-FLI1 as an aberrant transcription factor driving tumor development.
BAF Complex Retargeting
EWS-FLI1 uses the EWSR1 low-complexity/prion-like domain to retarget BRG1/BRM-associated factor (BAF/SWI-SNF) chromatin-remodeling complexes to tumor-specific enhancers. This neomorphic recruitment depends on tyrosine residues linked to phase-transition behavior of the EWSR1 domain and helps establish oncogenic enhancer activity.
Canonical EWS-FLI1 fusion enhanceropathy model
chromatin remodeling GO:0006338 ⚠ ABNORMAL
chromatin GO:0000785
Downstream
GGAA Microsatellite Enhancer Reprogramming BAF retargeting supports tumor-specific enhancer activation downstream of EWS-FLI1 occupancy. Canonical EWS-FLI1 fusion enhanceropathy model
Show evidence (2 references)
PMID:28844694 SUPPORT In Vitro
"recruited by the EWS-FLI1 fusion protein to tumor-specific enhancers and"
Demonstrates that EWS-FLI1 recruits BAF complexes to tumor-specific enhancers and that this recruitment contributes to gene activation.
PMID:28844694 SUPPORT In Vitro
"necessary for phase transitions of the EWSR1 prion-like domain."
Supports the phase-transition/prion-like-domain component of BAF retargeting by EWS-FLI1.
EWS-FLI1 Hub and Dosage Control
Endogenous EWS-FLI1 forms dynamic sub-diffraction chromatin hubs rather than stable macroscopic condensates. These hubs and downstream GGAA enhancer outputs are dosage-sensitive: a narrow range of low-complexity-domain interaction and fusion protein abundance supports oncogenic transcription, while excessive or insufficient EWS-FLI1 can alter differentiation, stress, survival, and metastatic plasticity.
Canonical EWS-FLI1 fusion enhanceropathy model
EWSR1 hgnc:3508 FLI1 hgnc:3749 TRIM8 hgnc:15579
regulation of gene expression GO:0010468 ⚠ ABNORMAL protein ubiquitination GO:0016567 ⚠ ABNORMAL protein stabilization GO:0050821 ↕ DYSREGULATED
Downstream
GGAA Microsatellite Enhancer Reprogramming Dynamic EWS-FLI1 hubs concentrate the fusion on chromatin and tune enhancer activation at GGAA microsatellites. Canonical EWS-FLI1 fusion enhanceropathy model
Tumor Cell Proliferation and Survival TRIM8-dependent fusion-protein turnover defines a tolerated oncogene dosage window required for Ewing sarcoma cell survival. Canonical EWS-FLI1 fusion enhanceropathy model
Metastatic Disease Graded EWS-FLI1 loss can produce non-linear phenotypes, including a pro-metastatic state at modest depletion. Canonical EWS-FLI1 fusion enhanceropathy model
Show evidence (4 references)
PMID:41659683 SUPPORT In Vitro
"forms dynamic, sub-diffraction-limit hubs with mechanisms of dissolution that"
Supports endogenous dynamic EWS-FLI1 hub formation rather than stable macroscopic condensates.
PMID:35483357 SUPPORT In Vitro
"narrow optimum of LCD-LCD interactions to activate its target genes associated"
Supports a narrow low-complexity-domain interaction window for oncogenic transcription.
PMID:34329586 SUPPORT In Vitro
"TRIM8 knockout led to an increase in EWS/FLI protein levels"
Supports TRIM8-mediated control of EWS-FLI1 protein abundance and oncogene overdose.
+ 1 more reference
GGAA Microsatellite Enhancer Reprogramming
EWS-FLI1 binds GGAA microsatellite repeats and canonical ETS motifs, remodeling the enhancer landscape. At GGAA repeats, multimeric EWS-FLI1 opens chromatin and creates de novo enhancers that contact target promoters; at conserved ETS enhancers, EWS-FLI1 can displace wild-type ETS factors and repress tumor suppressor and lineage-regulatory programs.
Canonical EWS-FLI1 fusion enhanceropathy model STAG2/cohesin-modified high-risk enhancer model
regulation of gene expression GO:0010468 ⚠ ABNORMAL chromatin remodeling GO:0006338 ⚠ ABNORMAL
chromatin GO:0000785
Downstream
Core Regulatory Circuitry Activation EWS-FLI1 establishes super-enhancers for KLF15, TCF4, and NKX2-2, building an autoregulatory transcription-factor circuit. Canonical EWS-FLI1 fusion enhanceropathy model
Blocked Differentiation Aberrant enhancer repression suppresses mesenchymal lineage regulators. Canonical EWS-FLI1 fusion enhanceropathy model
STAG2-Modified Enhancer State STAG2 loss reshapes EWS-FLI1 occupancy across monomeric and multimeric GGAA-repeat enhancer classes. STAG2/cohesin-modified high-risk enhancer model
ETV6 GGAA Counter-Regulation Native ETS factor ETV6 competes with EWS-FLI1 at short GGAA repeats and restrains a subset of fusion-driven enhancer activity. Canonical EWS-FLI1 fusion enhanceropathy model
Show evidence (6 references)
PMID:25453903 SUPPORT In Vitro
"reprograms gene regulatory circuits in Ewing sarcoma by directly inducing or"
Directly supports enhancer-level reprogramming as a central EWS-FLI1 mechanism.
PMID:25453903 SUPPORT In Vitro
"induce chromatin opening and create de novo enhancers that physically interact"
Supports GGAA-repeat enhancer creation and chromatin opening.
PMID:22086061 SUPPORT In Vitro
"EWS-FLI targets regions of the genome"
Supports Ian Davis lab evidence that the fusion retargets chromatin differently from wild-type FLI1.
+ 3 more references
ETV6 GGAA Counter-Regulation
ETV6 is a native ETS-family factor that competes with EWS-FLI1 at select short GGAA-repeat elements. This counter-regulatory layer restrains part of the enhanceropathy, and forced ETV6 degradation can paradoxically increase EWS-FLI1 transcriptional stress and tumor cell death.
Canonical EWS-FLI1 fusion enhanceropathy model
ETV6 hgnc:3495
regulation of gene expression GO:0010468 ⚠ ABNORMAL
Downstream
GGAA Microsatellite Enhancer Reprogramming ETV6 competition modulates EWS-FLI1 occupancy and output at short GGAA microsatellite enhancers. Canonical EWS-FLI1 fusion enhanceropathy model
Tumor Cell Proliferation and Survival ETV6 perturbation can increase EWS-FLI1-driven transcriptional stress and suppress tumor growth in preclinical models. Canonical EWS-FLI1 fusion enhanceropathy model
Show evidence (2 references)
PMID:36658219 SUPPORT In Vitro
"with EWS-FLI1 for binding to select DNA elements enriched for short GGAA repeat"
Supports ETV6 competition with EWS-FLI1 at short GGAA-repeat elements.
PMID:40215343 SUPPORT In Vitro
"EWS::FLI1 at short GGAA repeats to restrain"
Supports ETV6 as a restraining factor and therapeutic vulnerability.
GGAA Microsatellite Germline Susceptibility Architecture
Germline variation in GGAA microsatellite architecture can determine how strongly the acquired EWS-FLI1 fusion converts a locus into a neo-enhancer. At EGR2 and RREB1 susceptibility loci, longer or newly contiguous GGAA repeat alleles increase EWS-FLI1 binding and enhancer output, linking inherited repeat length to the somatic enhanceropathy and proliferative transcriptional programs.
Canonical EWS-FLI1 fusion enhanceropathy model Permissive developmental cell-of-origin model
EGR2 hgnc:3239 RREB1 hgnc:10449
regulation of gene expression GO:0010468 ⚠ ABNORMAL chromatin remodeling GO:0006338 ⚠ ABNORMAL cell population proliferation GO:0008283 ↑ INCREASED
Downstream
GGAA Microsatellite Enhancer Reprogramming Germline GGAA repeat length and purity alter the strength of EWS-FLI1 neo-enhancer formation at susceptible loci. Canonical EWS-FLI1 fusion enhanceropathy model Permissive developmental cell-of-origin model
Tumor Cell Proliferation and Survival Susceptibility-locus enhancer activation can increase expression of proliferation-associated transcriptional regulators. Canonical EWS-FLI1 fusion enhanceropathy model Permissive developmental cell-of-origin model
Show evidence (4 references)
PMID:26214589 SUPPORT In Vitro
"A risk allele connected adjacent GGAA repeats by"
Supports the mechanism by which a germline risk allele creates a stronger GGAA enhancer at EGR2.
PMID:26214589 SUPPORT In Vitro
"EWSR1-FLI1 preferentially bound to the A risk allele"
Supports allele-specific EWS-FLI1 binding at a germline susceptibility repeat.
PMID:36787739 SUPPORT Human Clinical
"had longer alleles (>135"
Supports longer germline GGAA alleles in Ewing sarcoma cases at the RREB1-associated susceptibility locus.
+ 1 more reference
NuRD/CHD4 Repressive Chromatin Program
EWS-FLI1 is not only an enhancer-activating transcription factor; it also directly represses tumor-suppressive and lineage-regulatory loci through NuRD-associated chromatin machinery. CHD4/NuRD and LSD1/HDAC functions support EWS-FLI1-mediated repression, global chromatin architecture, survival, and protection from spontaneous DNA damage.
Canonical EWS-FLI1 fusion enhanceropathy model Transcription-coupled replication stress vulnerability model
CHD4 hgnc:1919
negative regulation of transcription by RNA polymerase II GO:0000122 ⚠ ABNORMAL chromatin organization GO:0006325 ⚠ ABNORMAL DNA repair GO:0006281 ⚠ ABNORMAL
Downstream
Blocked Differentiation NuRD/LSD1/HDAC-mediated repression helps EWS-FLI1 maintain an immature, transformed state. Canonical EWS-FLI1 fusion enhanceropathy model
Tumor Cell Proliferation and Survival CHD4/NuRD dependence links the transcriptional pathograph to DNA-damage buffering and tumor cell survival. Canonical EWS-FLI1 fusion enhanceropathy model Transcription-coupled replication stress vulnerability model
Show evidence (4 references)
PMID:23178492 SUPPORT In Vitro
"transcriptional repression by EWS/FLI is mediated through direct binding of the NuRD complex"
Supports the direct EWS-FLI1-NuRD repressive arm of the pathograph.
PMID:23178492 SUPPORT In Vitro
"the repressive function of EWS/FLI is absolutely required for the oncogenic function"
Supports the need to represent repression as a causal oncogenic arm, not only as a side effect.
PMID:37963210 SUPPORT In Vitro
"induced tumor cell death by apoptosis and abolished colony formation"
Supports CHD4/NuRD as a survival dependency in Ewing sarcoma cells.
+ 1 more reference
Core Regulatory Circuitry Activation
EWS-FLI1 activates super-enhancers controlling a core regulatory circuitry composed of transcription factors including KLF15, TCF4, and NKX2-2. These factors reinforce their own and each other's regulatory elements and cooperate with EWS-FLI1 to sustain proliferation, survival signaling, and the Ewing transcriptional state.
Canonical EWS-FLI1 fusion enhanceropathy model
KLF15 hgnc:14536 TCF4 hgnc:11634 NKX2-2 hgnc:7835
regulation of gene expression GO:0010468 ⚠ ABNORMAL cell population proliferation GO:0008283 ↑ INCREASED
Downstream
Tumor Cell Proliferation and Survival Core regulatory transcription factors sustain proliferation and oncogenic signaling pathways in Ewing sarcoma cells. Canonical EWS-FLI1 fusion enhanceropathy model
Blocked Differentiation Core regulatory circuitry reinforces the undifferentiated tumor state. Canonical EWS-FLI1 fusion enhanceropathy model
Show evidence (2 references)
PMID:33080033 SUPPORT In Vitro
"each of these three TFs to activate their transcription."
Supports direct establishment of KLF15, TCF4, and NKX2-2 super-enhancers by EWS-FLI1.
PMID:33080033 SUPPORT In Vitro
"contribute significantly to cell proliferation of Ewing sarcoma both in vitro"
Supports the downstream proliferation role of the core regulatory circuitry.
Blocked Differentiation
EWS-FLI1 and its downstream transcriptional circuitry repress mesenchymal lineage regulators, maintaining Ewing sarcoma cells in an immature, proliferative state. This mechanism is linked to the unresolved cell-of-origin question because only some early progenitor contexts tolerate EWS-FLI1 and progress toward an Ewing-like state.
cell differentiation GO:0030154 ↓ DECREASED mesenchymal cell differentiation GO:0048762 ↓ DECREASED
Show evidence (2 references)
PMID:26000096 SUPPORT In Vitro
"NKX2-2 mediates the EWS/FLI-controlled block of mesenchymal features."
Directly supports EWS/FLI-mediated repression of mesenchymal features and blocked differentiation programs.
PMID:25453903 SUPPORT In Vitro
"and mesenchymal lineage regulators while activating oncogenes and potential"
Supports enhancer-level repression of mesenchymal lineage regulators.
ATF4-Serine-Glycine Metabolic Reprogramming
EWS-FLI1 and menin converge on ATF4 to activate a serine synthesis pathway transcriptional program. EWS-FLI1 also upregulates glutamine uptake and one-carbon cycle genes, linking fusion-driven transcription to biosynthetic metabolism, redox state, and survival.
Canonical EWS-FLI1 fusion enhanceropathy model
ATF4 hgnc:786 PHGDH hgnc:8923 SLC1A5 hgnc:10943
L-serine biosynthetic process GO:0006564 ↑ INCREASED L-glutamine transport GO:0006868 ↑ INCREASED generation of precursor metabolites and energy GO:0006091 ⚠ ABNORMAL
Downstream
Tumor Cell Proliferation and Survival Fusion-driven metabolic rewiring supports biomass production, redox state, and survival in rapidly proliferating tumor cells. Canonical EWS-FLI1 fusion enhanceropathy model
Show evidence (3 references)
PMID:33741715 SUPPORT In Vitro
"directly activate ATF4 transcription."
Supports direct fusion-driven ATF4 activation.
PMID:29873416 SUPPORT In Vitro
"required for serine-glycine biosynthesis and uptake of the alternative nutrient"
Supports direct EWS-FLI1 control of serine-glycine biosynthesis and glutamine uptake.
PMID:29873416 SUPPORT In Vitro
"serine-glycine metabolism or glutamine uptake are potential targetable"
Supports the therapeutic-vulnerability interpretation of this metabolic mechanism.
Replication Stress and Impaired Homologous Recombination
EWS-FLI1-driven high-output transcription alters the response to DNA damage, increases R-loop accumulation and replication stress, and impairs BRCA1-linked homologous recombination. Survival under this stress state can depend on factors such as USP1 and survivin, creating both chemotherapy sensitivity and resistance-adaptation questions.
Transcription-coupled replication stress vulnerability model
BRCA1 hgnc:1100 USP1 hgnc:12607 BIRC5 hgnc:593
DNA replication GO:0006260 ↕ DYSREGULATED double-strand break repair via homologous recombination GO:0000724 ↓ DECREASED DNA repair GO:0006281 ↓ DECREASED
Experimental models
Human embryonic mesenchymal stem cell EWS-FLI1 transformation model PRIMARY CELL CULTURE EWS-FLI1-expressing heMSCs show defective BRCA1-mediated DNA repair, modeling the replication stress and HRR deficiency arm of the pathograph.
Downstream
Tumor Cell Proliferation and Survival Replication stress creates a survival bottleneck that Ewing sarcoma cells can buffer through USP1-survivin signaling. Transcription-coupled replication stress vulnerability model
Show evidence (3 references)
PMID:29513652 SUPPORT In Vitro
"damage-induced transcription, accumulation of R-loops and increased replication"
Supports R-loop accumulation and replication stress downstream of EWS-FLI1 activity.
PMID:29513652 SUPPORT In Vitro
"homologous recombination is impaired in Ewing sarcoma"
Supports the homologous-recombination defect in this node.
PMID:37478161 SUPPORT In Vitro
"USP1-Survivin axis promotes EWS cell survival, and USP1 inhibition sensitizes"
Supports the survival adaptation downstream of replication stress.
R-loop Resolution and Replication-Fork Vulnerability
EWS-FLI1 creates a replication-stress vulnerability through more than bulk transcriptional load. It can sequester the DHX9 helicase and impair R-loop resolution after topoisomerase stress, while also directly increasing SLFN11 expression. SLFN11 then blocks stressed replication forks, linking the fusion program to chemotherapy sensitivity, resistance through DHX9 or SLFN11 state, and the broader DNA-damage response pathograph.
Transcription-coupled replication stress vulnerability model
EWSR1 hgnc:3508 FLI1 hgnc:3749 DHX9 hgnc:2750 SLFN11 hgnc:26633
DNA replication GO:0006260 ↕ DYSREGULATED DNA damage checkpoint signaling GO:0000077 ⚠ ABNORMAL DNA repair GO:0006281 ⚠ ABNORMAL
Downstream
Replication Stress and Impaired Homologous Recombination DHX9 sequestration increases unresolved R-loops, and SLFN11 blocks fork progression when replication is stressed. Transcription-coupled replication stress vulnerability model
Tumor Cell Proliferation and Survival The same R-loop and fork-blocking state can increase treatment sensitivity or select resistant cells with altered DHX9 or SLFN11 activity. Transcription-coupled replication stress vulnerability model
Show evidence (4 references)
PMID:40721661 SUPPORT In Vitro
"sequestering DHX9 helicase, ultimately resulting in"
Supports the direct DHX9-sequestration arm of the R-loop mechanism.
PMID:25779942 SUPPORT In Vitro
"EWS-FLI1 binds near the transcription start site of SLFN11 promoter"
Supports SLFN11 as a direct EWS-FLI1 transcriptional target.
PMID:25779942 SUPPORT Human Clinical
"patients with higher SLFN11 expression showed better"
Supports clinical relevance of SLFN11 expression for outcome in Ewing sarcoma.
+ 1 more reference
STAG2-Modified Enhancer State
Loss-of-function STAG2 alterations in a subset of Ewing sarcomas reshape cohesin-dependent chromatin architecture, EWS-FLI1 enhancer occupancy, and DNA-damage response state. Current evidence supports a model in which STAG2 loss selectively amplifies multimeric GGAA microsatellite enhancer programs while also altering PRC2- and CTCF-dependent contacts. Clinically, STAG2 protein loss and STAG2/TP53 co-alteration mark high-risk disease, but the relative contributions of enhancer amplification, PRC2 derepression, and replication-fork vulnerability remain unresolved.
STAG2/cohesin-modified high-risk enhancer model Transcription-coupled replication stress vulnerability model
STAG2 hgnc:11355
chromatin remodeling GO:0006338 ⚠ ABNORMAL chromosome organization GO:0051276 ⚠ ABNORMAL regulation of gene expression GO:0010468 ⚠ ABNORMAL DNA replication GO:0006260 ↕ DYSREGULATED DNA repair GO:0006281 ⚠ ABNORMAL
Downstream
GGAA Microsatellite Enhancer Reprogramming STAG2/cohesin status changes enhancer-promoter communication at long EWS-FLI1-bound GGAA repeats and rewires enhancer output. STAG2/cohesin-modified high-risk enhancer model
Replication Stress and Impaired Homologous Recombination STAG2 loss can compound the fusion-driven DNA-damage state through replication-fork and homologous-recombination vulnerabilities. STAG2/cohesin-modified high-risk enhancer model Transcription-coupled replication stress vulnerability model
Metastatic Disease STAG2 loss can promote an aggressive, metastasis-prone transcriptional state. STAG2/cohesin-modified high-risk enhancer model
Show evidence (9 references)
PMID:34129824 SUPPORT In Vitro
"contacts. Moreover, loss of STAG2 also disrupted PRC2-mediated regulation of"
Supports STAG2 loss as a chromatin and transcriptional rewiring mechanism.
PMID:34129824 SUPPORT Model Organism
"the metastatic potential of Ewing sarcoma xenografts."
Supports the metastasis-promoting consequence in xenograft models.
PMID:41950086 SUPPORT In Vitro
"rather than globally attenuates, EWS-FLI1 function, amplifying a high-risk"
Supports the current model that STAG2 loss changes the quality of EWS-FLI1 enhancer activity.
+ 6 more references
Tumor Cell Proliferation and Survival
Multiple fusion-driven mechanisms converge on tumor cell proliferation and survival: core regulatory circuitry sustains oncogenic signaling, metabolic reprogramming supplies biomass and redox buffering, and replication-stress adaptation prevents apoptosis during genotoxic stress.
Canonical EWS-FLI1 fusion enhanceropathy model STAG2/cohesin-modified high-risk enhancer model Transcription-coupled replication stress vulnerability model
cell population proliferation GO:0008283 ↑ INCREASED
Experimental models
Ewing sarcoma tumor organoid model systems ORGANOID Enables preclinical testing of tumor growth and survival responses.
Patient-derived Ewing sarcoma culture panel PRIMARY CELL CULTURE Assays patient-derived proliferation and therapy-response phenotypes.
Flow-perfusion Ewing sarcoma 3D scaffold coculture CO CULTURE Models stromal support of growth and drug-resistance phenotypes.
Downstream
Soft Tissue Mass / Localized Swelling Sustained proliferation and impaired differentiation produce the expanding local tumor mass. Canonical EWS-FLI1 fusion enhanceropathy model
Metastatic Disease Which survival and stress-adaptation states drive dissemination and relapse remains incompletely resolved. STAG2/cohesin-modified high-risk enhancer model Transcription-coupled replication stress vulnerability model
Permissive Progenitor Cell State
The cell of origin remains unresolved. Mesenchymal stem/progenitor and neural crest-derived progenitor models support the hypothesis that EWS-FLI1 is oncogenic only in specific early developmental cell states with permissive chromatin and differentiation programs. A 2025 embryonic mesenchymal stem cell model supports transformation from undifferentiated early heMSCs, while earlier work supports neural crest-related states as Ewing-like.
Permissive developmental cell-of-origin model
early mesenchymal stem cell CL:0000134 migratory neural crest cell CL:0000333
cell differentiation GO:0030154 ⚠ ABNORMAL
Experimental models
Human embryonic mesenchymal stem cell EWS-FLI1 transformation model PRIMARY CELL CULTURE Demonstrates that only undifferentiated, early heMSCs (not adult MSCs or pediatric MSCs) fully support EWS-FLI1 transformation, linking progenitor developmental state to oncogenic permissiveness.
Downstream
EWS-FLI1 Fusion Oncogene The progenitor chromatin state is hypothesized to determine whether EWS-FLI1 expression is tolerated and can initiate an Ewing-like program. Permissive developmental cell-of-origin model
GGAA Microsatellite Enhancer Reprogramming Developmental chromatin context may determine which GGAA microsatellites become functional EWS-FLI1 enhancers. Permissive developmental cell-of-origin model
IGF-1/YAP1 Developmental Cooperation Growth-factor signaling in a permissive mesenchymal developmental window may convert EWS-FLI1 expression from toxic or malformed development into stable malignant transformation. Permissive developmental cell-of-origin model
Show evidence (4 references)
PMID:21559395 SUPPORT In Vitro
"cells have been implicated as cells of origin."
Supports the leading mesenchymal and neural crest cell-of-origin hypotheses.
PMID:21559395 SUPPORT In Vitro
"initiates transition to an ESFT-like state."
Supports the ability of EWS-FLI1 to initiate an Ewing-like state in neural crest-related cells.
PMID:41136396 SUPPORT In Vitro
"by EWSR::ETS rearrangements whose cellular origin remains unclear."
Establishes the unresolved nature of the cell-of-origin question.
+ 1 more reference
IGF-1/YAP1 Developmental Cooperation
Pubertal IGF-1 signaling is a proposed non-genetic cooperating mechanism that can reprogram EWS-FLI1-mutant mesenchymal cells toward stable transformation through YAP1/TEAD activity. This mechanism helps explain the adolescent age peak and the rarity of recurrent cooperating mutations, but it remains to be validated across human progenitor systems and across established tumor maintenance states.
Permissive developmental cell-of-origin model
limb-derived mesenchymal progenitor cell CL:0000134
IGF1 hgnc:5464 YAP1 hgnc:16262
insulin-like growth factor receptor signaling pathway GO:0048009 ↑ INCREASED intracellular signal transduction GO:0035556 ⚠ ABNORMAL cell fate commitment GO:0045165 ⚠ ABNORMAL
Experimental models
Flow-perfusion Ewing sarcoma 3D scaffold coculture CO CULTURE Assays IGF-1/IGF-1R signaling under controlled tumor-stroma and shear-stress conditions.
Downstream
Tumor Cell Proliferation and Survival IGF-1/YAP1 signaling can cooperate with EWS-FLI1 to promote stable transformation and tumorigenicity in a developmental mesenchymal context. Permissive developmental cell-of-origin model
Blocked Differentiation The developmental signaling state may help lock EWS-FLI1-expressing progenitors into an aberrant fate rather than normal mesenchymal differentiation. Permissive developmental cell-of-origin model
Show evidence (2 references)
PMID:40080499 SUPPORT Model Organism
"concentrations mimicking serum levels during puberty"
Supports pubertal-level IGF-1 exposure as a cooperating developmental signal.
PMID:40080499 SUPPORT Model Organism
"Yap1 plays a central role."
Supports YAP1 as the central mediator of the IGF-1 cooperating mechanism.
✶

Histopathology

4
Small Round Cell Tumor VERY_FREQUENT
Ewing sarcoma is a small round cell tumor of bone or soft tissue.
Show evidence (1 reference)
PMID:35117540 SUPPORT Human Clinical
"Ewing sarcoma is a small round cell tumor of bone or soft tissue"
Abstract defines Ewing sarcoma as a small round cell tumor of bone or soft tissue.
Homer Wright Rosette-like Formation OCCASIONAL
Atypical Ewing sarcoma of bone can show rosette-like textures resembling Homer-Wright rosettes, reflecting neuroectodermal differentiation features in a minority of cases rather than a required diagnostic feature.
Show evidence (1 reference)
PMID:3113717 SUPPORT Human Clinical
"Ewing's sarcoma (ES) of bone may occasionally display rosette-like textures mimicking Homer-Wright ones"
Supports Homer Wright rosette-like formation as an occasional histopathologic pattern in atypical Ewing sarcoma of bone.
High Grade Tumor VERY_FREQUENT
Ewing sarcoma is classified as high grade by definition. Tumors are aggressive and highly malignant, and high-grade morphology is a universal feature used in staging and treatment stratification.
Show evidence (1 reference)
PMID:35117540 SUPPORT Human Clinical
"originating from the neuroectoderm. Aggressive and highly malignant are the main"
Supports high-grade classification as a defining histopathological feature of Ewing sarcoma: the abstract describes it as aggressive and highly malignant, consistent with universal high-grade tumor designation.
Geographic Tumor Necrosis FREQUENT
Tumor cell necrosis can be assessed in Ewing sarcoma resection specimens, especially after neoadjuvant chemotherapy. The degree of tumor necrosis is a clinically meaningful histologic response marker: greater than or equal to 90% tumor necrosis defines a good chemotherapy response in many studies and is associated with improved local recurrence-free survival.
Show evidence (1 reference)
PMID:17177205 SUPPORT Human Clinical
"90% tumor necrosis), had superior LRFS at 5 years (86% vs 51%, P = .015)."
Supports post-chemotherapy tumor necrosis as an Ewing sarcoma histologic-response measure with prognostic significance.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Ewing Sarcoma Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

7
Blood 1
Anemia OCCASIONAL Anemia HP:0001903
Metabolism 1
Fever OCCASIONAL Fever HP:0001945
Musculoskeletal 1
Pathologic Fracture OCCASIONAL Pathologic fracture HP:0002756
Constitutional 1
Bone Pain FREQUENT Bone pain HP:0002653
Show evidence (1 reference)
PMID:34235109 SUPPORT Human Clinical
"Pain (75.3%) was the most common symptom at presentation."
Provides Ewing sarcoma-specific cohort evidence that pain is the most common presenting symptom and supports the FREQUENT frequency assignment.
Growth 1
Weight Loss OCCASIONAL Weight loss HP:0001824
Neoplasm 2
Soft Tissue Mass / Localized Swelling VERY_FREQUENT Soft tissue neoplasm HP:0031459
Metastatic Disease FREQUENT Neoplasm HP:0002664
Show evidence (3 references)
PMID:30215968 SUPPORT Human Clinical
"lowers the five-year survival rate to 20% to 30%."
Confirms that metastatic disease lowers five-year survival to 20-30%.
PMID:17301523 SUPPORT Human Clinical
"an approximately 10-30% 5-year event-free survival rate."
Confirms the poor prognosis for metastatic Ewing sarcoma with quantitative survival data.
PMID:36669140 SUPPORT Human Clinical
"The 3-year EFS estimates were 37.4%"
Provides precise 3-year EFS data from the COG AEWS1221 phase III trial for metastatic Ewing sarcoma.
🧬

Genetic Associations

4
EWS-FLI1 Fusion (Somatic Fusion Oncogene)
Show evidence (1 reference)
PMID:17250957 SUPPORT Human Clinical
"It is associated in 85% of cases with the"
Directly confirms the 85% frequency of the t(11;22) translocation creating EWS-FLI1.
STAG2 (Somatic Tumor Suppressor Mutation)
Gene: STAG2 hgnc:11355 variant_origin: SOMATIC
Show evidence (2 references)
PMID:25223734 SUPPORT Human Clinical
"detected in STAG2 (17%), CDKN2A (12%), TP53 (7%)"
Establishes STAG2 as one of the most common recurrent somatic alterations in Ewing sarcoma.
PMID:36221002 SUPPORT Human Clinical
"5-year event-free survival was 54% (95% CI 34-70%) and"
Supports the adverse clinical association of STAG2 protein loss in localized Ewing sarcoma.
TP53 (Somatic Tumor Suppressor Mutation)
Gene: TP53 hgnc:11998 variant_origin: SOMATIC
Show evidence (1 reference)
PMID:25223734 SUPPORT Human Clinical
"STAG2 and TP53 mutations are often"
Supports TP53 mutation as part of the high-risk STAG2/TP53 co-altered Ewing sarcoma subset.
CDKN2A (Somatic Tumor Suppressor Deletion)
Gene: CDKN2A hgnc:1787 variant_origin: SOMATIC
Show evidence (1 reference)
PMID:25223734 SUPPORT Human Clinical
"STAG2 mutations and CDKN2A deletions were mutually exclusive"
Supports CDKN2A deletion as a recurrent secondary alteration distinct from STAG2-mutant Ewing sarcoma.
💊

Medical Actions

7
Neoadjuvant Chemotherapy
Action: Neoadjuvant Chemotherapy NCIT:C213450
Agent: vincristine CHEBI:28445 doxorubicin CHEBI:28748 cyclophosphamide CHEBI:4027 ifosfamide CHEBI:5864 etoposide CHEBI:4911
Intensive multi-agent chemotherapy (vincristine, doxorubicin, cyclophosphamide alternating with ifosfamide/etoposide - VDC/IE) is standard. Neoadjuvant chemotherapy shrinks tumors before local control.
Show evidence (3 references)
PMID:20152770 SUPPORT Human Clinical
"Cooperative group studies have led to chemotherapy regimens"
Confirms the five-drug chemotherapy backbone used in Ewing sarcoma treatment.
PMID:17301523 SUPPORT Human Clinical
"standard chemotherapy for localized ESFT"
Confirms VDC/IE as the standard North American chemotherapy regimen for Ewing sarcoma.
PMID:36669140 SUPPORT Human Clinical
"interval-compressed vincristine/doxorubicin/cyclophosphamide alternating once"
Confirms VDC/IE as standard chemotherapy backbone in the COG phase III trial for metastatic Ewing sarcoma.
Surgical Resection
Action: Definitive Surgical Resection NCIT:C154430
Wide surgical resection with negative margins is preferred when feasible without excessive morbidity. Reconstruction may be needed for limb salvage.
Show evidence (1 reference)
PMID:35117540 SUPPORT Human Clinical
"CT combined surgery achieved"
Supports that chemotherapy combined with surgery achieves the best survival outcomes.
Radiation Therapy
Action: Radiation Therapy NCIT:C15313
Definitive radiation is used for unresectable tumors or when surgery would cause significant morbidity. Also used post-operatively for close or positive margins.
Show evidence (1 reference)
PMID:33818887 SUPPORT Human Clinical
"surgery, definitive radiation, or a combination of surgery and radiation"
Confirms the role of definitive radiation as a local treatment option in Ewing sarcoma management.
Adjuvant Chemotherapy
Action: chemotherapy MAXO:0000647
Additional chemotherapy after local control to eliminate micrometastatic disease. Total treatment duration is typically 9-12 months.
PARP Inhibitor Combination Therapy
Action: Pharmacotherapy NCIT:C15986
Agent: talazoparib CHEBI:231344 temozolomide CHEBI:72564
Investigational PARP-targeted treatment strategies for recurrent or refractory Ewing sarcoma aim to exploit fusion-linked replication stress and homologous-recombination defects. Clinical talazoparib plus temozolomide was feasible but showed no objective Ewing responses in a small phase 2 cohort, while dual PARP-HDAC inhibition has preclinical activity in Ewing sarcoma cells and spheroids.
Mechanism Target:
MODULATES Replication Stress and Impaired Homologous Recombination — PARP inhibition targets the DNA-repair and replication-stress axis modeled in Ewing sarcoma, with combination strategies intended to deepen synthetic-lethal pressure on tumor cells.
Show evidence (1 reference)
PMID:37279093 SUPPORT In Vitro
"bifunctional PARPi (kt-3283) with dual activity toward PARP1/2 and HDAC enzymes in Ewing sarcoma cells."
Supports direct targeting of PARP-dependent DNA-repair biology in Ewing sarcoma cells, coupled to chromatin modulation through HDAC inhibition.
MODULATES NuRD/CHD4 Repressive Chromatin Program — Dual PARP-HDAC inhibition links the replication-stress vulnerability to chromatin-state modulation represented by the NuRD/CHD4/LSD1 repressive pathograph arm.
Show evidence (1 reference)
PMID:37279093 SUPPORT In Vitro
"kt-3283 displayed enhanced cytotoxicity in Ewing sarcoma models."
Supports a chromatin-linked PARP-HDAC treatment concept in Ewing sarcoma models.
Show evidence (2 references)
PMID:31724813 PARTIAL Human Clinical
"0 of 10 EWS subjects experienced an objective response; two experienced prolonged SD."
Clinical evidence supports feasibility but only partial therapeutic support because objective responses were not observed in the phase 2 Ewing cohort.
PMID:37279093 SUPPORT In Vitro
"In three-dimensional spheroid models of Ewing sarcoma, kt-3283 showed efficacy"
Supports preclinical activity of dual PARP-HDAC inhibition in 3D Ewing sarcoma spheroid models.
LSD1 Inhibitor Therapy
Action: Pharmacotherapy NCIT:C15986
Agent: seclidemstat NCIT:C154328
LSD1/KDM1A inhibition with seclidemstat (SP-2577) is an investigational strategy for fusion-positive sarcomas that attempts to reverse or modulate FET-fusion transcriptional programs. In Ewing sarcoma, the rationale links directly to the EWS-FLI1-associated NuRD/CHD4/LSD1 repressive chromatin arm.
Mechanism Target:
MODULATES NuRD/CHD4 Repressive Chromatin Program — Seclidemstat is intended to modulate LSD1-linked transcriptional and chromatin programs downstream of EWS-FLI1 and related FET fusion proteins.
Show evidence (1 reference)
PMID:40852926 SUPPORT In Vitro
"Seclidemstat recapitulated much of SP-2509 transcriptional activity in Ewing sarcoma."
Supports seclidemstat modulation of the Ewing sarcoma transcriptional program linked to the LSD1 pathograph arm.
Show evidence (2 references)
PMID:40852926 SUPPORT In Vitro
"seclidemstat (SP-2577), is currently in clinical trials for FET-rearranged sarcomas (NCT03600649)"
Supports seclidemstat as an emerging clinical-stage therapy for FET-rearranged sarcomas including Ewing sarcoma.
PMID:34453478 PARTIAL Model Organism
"inhibited growth of three of eight Ewing sarcoma (EwS)"
Supports in vivo preclinical activity in a subset of Ewing xenografts, but only partial support because the same abstract reports limited activity overall.
USP1 Inhibitor Therapy
Action: Pharmacotherapy NCIT:C15986
Agent: USP1 inhibitor NCIT:C471
USP1 inhibition is a preclinical targeted strategy aimed at the EWS-FLI1 induced USP1-survivin survival buffer that helps Ewing sarcoma cells tolerate endogenous replication stress and standard chemotherapy exposure.
Mechanism Target:
INHIBITS Replication Stress and Impaired Homologous Recombination — USP1 inhibition blocks a survival adaptation within the replication-stress node by destabilizing the USP1-survivin axis and sensitizing cells to DNA damaging chemotherapy.
Show evidence (1 reference)
PMID:37478161 SUPPORT In Vitro
"USP1 inhibition sensitizes cells to doxorubicin and etoposide treatment."
Supports targeting the USP1-dependent replication-stress survival buffer in Ewing sarcoma cells.
Show evidence (1 reference)
PMID:37478161 SUPPORT In Vitro
"USP1 knockdown or inhibition arrests EWS cell growth and induces cell death by apoptosis."
Supports USP1 inhibition as a preclinical targeted treatment concept in Ewing sarcoma.
🔬

Biochemical Markers

1
EWS-FLI1 Fusion Detection
Show evidence (1 reference)
PMID:17301523 SUPPORT Human Clinical
"EWS-FLI 1 among Ewing sarcoma"
Supports molecular detection of EWS-FLI1 fusion as a defining diagnostic feature.
🧫

Experimental Models

4
Ewing sarcoma tumor organoid model systems ORGANOID namo:Organoid
Tumor organoids are part of the current Ewing sarcoma preclinical model landscape and provide a non-animal 3D system for therapy evaluation and mechanism-focused modeling alongside cell lines and xenografts.
Ewing sarcoma tumor organoid preclinical modeling
Organism
human NCBITaxon:9606
Cell source
Ewing sarcoma tumor-derived cells
Culture
Three-dimensional tumor organoid culture
Publication
PMID:40911901
Pathograph links
EWS-FLI1 Fusion Oncogene Models fusion-positive tumor biology in a 3D non-animal context.
Tumor Cell Proliferation and Survival Enables preclinical testing of tumor growth and survival responses.
Show evidence (1 reference)
PMID:40911901 SUPPORT Other
"vitro (cell lines and tumor organoids) and in vivo (mouse and nonmammalian xenografts) model systems."
Supports tumor organoids as part of the Ewing sarcoma preclinical modeling landscape.
Patient-derived Ewing sarcoma culture panel PRIMARY_CELL_CULTURE namo:TwoDCellCulture
Patient-derived Ewing sarcoma cultures provide a primary-cell in vitro non-animal model for studying EWSR1 fusion status, proliferation, migration, and treatment response in models that differ transcriptionally from long-established cell lines.
Ewing sarcoma patient-derived ES cultures preclinical drug response testing
Organism
human NCBITaxon:9606
Cell source
Patient-derived Ewing sarcoma tumor cultures
Culture
Patient-derived in vitro culture
Publication
PMID:41681984
Pathograph links
EWS-FLI1 Fusion Oncogene Models EWSR1 fusion-positive tumor state in patient-derived cultures.
Tumor Cell Proliferation and Survival Assays patient-derived proliferation and therapy-response phenotypes.
Findings
Patient-derived Ewing cultures retain EWSR1 fusion DNA and clinically relevant treatment-response features.
Show evidence (1 reference)
PMID:41681984 SUPPORT In Vitro
"All PDES contain EWSR1 fusion DNA"
Supports PDES as patient-derived, fusion-positive Ewing sarcoma models.
Show evidence (1 reference)
PMID:41681984 SUPPORT In Vitro
"we have established and characterised patient-derived ES cultures (PDES) in vitro."
Supports this as a patient-derived in vitro Ewing sarcoma model system.
Flow-perfusion Ewing sarcoma 3D scaffold coculture CO_CULTURE namo:OrganOnChip
Flow-perfusion 3D scaffold cocultures combine Ewing sarcoma cells with mesenchymal stromal cells under biomechanical stimulation, enabling controlled testing of tumor-stroma signaling, IGF-1R/STAT3 biology, and drug-resistance mechanisms that are absent from standard monolayer systems.
Ewing sarcoma tumor-stroma coculture flow perfusion
mesenchymal stem cell CL:0000134
Organism
human NCBITaxon:9606
Cell source
Ewing sarcoma cells cocultured with mesenchymal stem cells
Culture
3D scaffold coculture in a flow perfusion bioreactor
Publication
PMID:27923328
Pathograph links
IGF-1/YAP1 Developmental Cooperation Assays IGF-1/IGF-1R signaling under controlled tumor-stroma and shear-stress conditions.
Tumor Cell Proliferation and Survival Models stromal support of growth and drug-resistance phenotypes.
Show evidence (2 references)
PMID:27923328 SUPPORT In Vitro
"ES cells and mesenchymal stem cells (MSCs) in 3D scaffolds within a flow perfusion bioreactor"
Supports this as a 3D tumor-stroma coculture model for Ewing sarcoma.
PMID:26240353 SUPPORT In Vitro
"poly(ε-caprolactone) 3D scaffolds within a flow perfusion bioreactor."
Supports the flow-perfusion scaffold format for Ewing sarcoma drug-sensitivity modeling.
Human embryonic mesenchymal stem cell EWS-FLI1 transformation model PRIMARY_CELL_CULTURE namo:TwoDCellCulture
Human embryonic mesenchymal stem cells (heMSCs) transduced with EWS::FLI1 acquire an Ewing sarcoma transcriptome and form tumors in xenograft models, providing a human-cell-based non-established-cell-line new approach methodology for studying cell-of-origin context, DNA damage repair defects, and fusion-gene transformation. This model differs from adult MSC and neural-crest-based models in that only undifferentiated early heMSCs fully support EWS-FLI1 oncogenic transformation.
Ewing sarcoma EWS-FLI1 transformation embryonic developmental context
mesenchymal stem cell CL:0000134
Organism
human NCBITaxon:9606
Cell source
Human embryonic mesenchymal stem cells (heMSCs) transduced with EWS::FLI1 lentivirus
Culture
Primary embryonic MSC culture with lentiviral oncogene transduction and xenograft validation
Publication
PMID:41136396
Pathograph links
EWS-FLI1 Fusion Oncogene Models EWS-FLI1 oncogene expression in an embryonic human mesenchymal developmental context, with xenograft tumor formation demonstrating transformation capacity.
Permissive Progenitor Cell State Demonstrates that only undifferentiated, early heMSCs (not adult MSCs or pediatric MSCs) fully support EWS-FLI1 transformation, linking progenitor developmental state to oncogenic permissiveness.
Replication Stress and Impaired Homologous Recombination EWS-FLI1-expressing heMSCs show defective BRCA1-mediated DNA repair, modeling the replication stress and HRR deficiency arm of the pathograph.
Findings
EWS::FLI1 expression in undifferentiated human embryonic MSCs enforces an Ewing sarcoma transcriptome and enables tumor formation in xenografts, with evidence of defective DNA damage repair.
Show evidence (1 reference)
PMID:41136396 SUPPORT Model Organism
"heMSCs results in the formation of tumors expressing characteristic ES markers."
Supports this model: EWS-FLI1-transduced heMSCs form Ewing sarcoma-like tumors in xenograft hosts, validating transformation capacity in the embryonic MSC developmental context.
Show evidence (1 reference)
PMID:41136396 SUPPORT In Vitro
"is able to endow transforming capacity when expressed in undifferentiated, early"
Supports using early embryonic MSCs as a primary-cell new approach methodology for studying EWS-FLI1 transformation: only undifferentiated heMSCs — not adult MSCs or pediatric MSCs — fully support oncogene-driven transformation.
{ }

Source YAML

click to show 
name: Ewing Sarcoma
creation_date: '2026-01-26T02:55:13Z'
updated_date: '2026-05-03T05:12:56Z'
description: >-
  Ewing sarcoma is an aggressive pediatric bone and soft tissue malignancy
  characterized by the pathognomonic EWS-FLI1 fusion gene, present in approximately
  85% of cases. This translocation t(11;22)(q24;q12) creates a chimeric transcription
  factor that forms dosage-sensitive chromatin hubs, rewires chromatin at GGAA
  microsatellites, activates core regulatory circuitry, represses lineage and
  tumor-suppressive programs through NuRD/CHD4-associated mechanisms, alters
  metabolism and DNA repair, and blocks lineage differentiation. The fusion is
  diagnostic and remains a compelling but challenging therapeutic target; developmental
  IGF-1/YAP1 signaling, germline GGAA-repeat architecture, ETV6 counter-regulation,
  DHX9/SLFN11 replication-stress biology, and secondary events such as STAG2 loss
  can modify the fusion-driven pathograph and contribute to high-risk biology.
categories:
- Pediatric Cancer
- Bone Cancer
- Sarcoma
parents:
- bone sarcoma
has_subtypes:
- name: Osseous Ewing Sarcoma
  subtype_term:
    preferred_term: Ewing sarcoma of bone
    term:
      id: MONDO:0002625
      label: Ewing sarcoma of bone
  description: >-
    Primary tumors arising in bone, most commonly the pelvis, femur, and other
    long bones. Accounts for approximately 80% of Ewing sarcoma cases. Typically
    presents with localized pain and swelling.
- name: Extraosseous Ewing Sarcoma
  subtype_term:
    preferred_term: extraskeletal Ewing sarcoma
    term:
      id: MONDO:0018270
      label: extraskeletal Ewing sarcoma
  description: >-
    Primary tumors arising in soft tissues outside of bone. Can occur in chest
    wall, paravertebral region, or extremities. Shares the same EWS-FLI1 fusion
    and treated similarly to osseous disease.
pathophysiology:
- name: EWS-FLI1 Fusion Oncogene
  description: >-
    The t(11;22)(q24;q12) translocation fuses the EWS gene (EWSR1) on chromosome 22
    with the FLI1 gene on chromosome 11. The resulting EWS-FLI1 protein functions
    as an aberrant FET-ETS transcription factor. It is the truncal driver of most
    Ewing sarcomas, but its oncogenic effect depends on a permissive developmental
    cell state and on downstream enhancer, transcriptional, metabolic, and DNA
    damage-response programs.
  cell_types:
  - preferred_term: mesenchymal stem cell
    term:
      id: CL:0000134
      label: mesenchymal stem cell
  genes:
  - preferred_term: EWSR1
    term:
      id: hgnc:3508
      label: EWSR1
  - preferred_term: FLI1
    term:
      id: hgnc:3749
      label: FLI1
  biological_processes:
  - preferred_term: positive regulation of transcription by RNA polymerase II
    modifier: ABNORMAL
    term:
      id: GO:0045944
      label: positive regulation of transcription by RNA polymerase II
  locations:
  - preferred_term: bone tissue
    term:
      id: UBERON:0002481
      label: bone tissue
  downstream:
  - target: EWS-FLI1 Hub and Dosage Control
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      Endogenous EWS-FLI1 forms dynamic low-complexity-domain-dependent chromatin
      hubs, and tumor behavior is sensitive to both excessive and submaximal
      fusion protein activity.
  - target: BAF Complex Retargeting
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      The EWSR1-derived low-complexity domain enables EWS-FLI1 to recruit BAF
      chromatin-remodeling complexes to tumor-specific enhancers.
  - target: GGAA Microsatellite Enhancer Reprogramming
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      EWS-FLI1 occupies GGAA microsatellite repeats and canonical ETS sites,
      creating de novo enhancers while repressing other enhancer classes.
  - target: NuRD/CHD4 Repressive Chromatin Program
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      EWS-FLI1 has a direct repressive arm involving NuRD-associated chromatin
      machinery, including CHD4 and LSD1/HDAC activity, in addition to its
      enhancer-activation arm.
  - target: Blocked Differentiation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - enhancer repression of mesenchymal lineage regulators
    - NKX2-2-mediated repression of mesenchymal features
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      Fusion-driven transcriptional repression and downstream transcription
      factors suppress mesenchymal differentiation programs.
  - target: ATF4-Serine-Glycine Metabolic Reprogramming
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    - replication_stress_vulnerability_model
    description: EWS-FLI1 directly activates ATF4 and metabolic stress-response programs.
  - target: Replication Stress and Impaired Homologous Recombination
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - high-output transcription
    - R-loop accumulation
    hypothesis_groups:
    - replication_stress_vulnerability_model
    description: >-
      Fusion-driven transcriptional stress produces R-loops, replication stress,
      and BRCA1-linked homologous-recombination defects.
  - target: R-loop Resolution and Replication-Fork Vulnerability
    causal_link_type: DIRECT
    hypothesis_groups:
    - replication_stress_vulnerability_model
    description: >-
      EWS-FLI1 can amplify replication stress through DHX9 sequestration and
      through transcriptional activation of SLFN11-dependent fork-blocking
      responses to DNA-targeted therapy.
  evidence:
  - reference: PMID:33741715
    reference_title: "EWS-FLI1 and Menin Converge to Regulate ATF4 Activity in Ewing Sarcoma."
    supports: PARTIAL
    evidence_source: IN_VITRO
    snippet: "Ewing sarcomas are driven by EWS-ETS fusions, most commonly EWS-FLI1"
    explanation: This supports EWS-FLI1 as a key driver fusion in Ewing sarcoma, but not all specific structural details in the descriptor.
  - reference: PMID:17250957
    reference_title: "The Biology of Ewing sarcoma."
    supports: SUPPORT
    snippet: "It is associated in 85% of cases with the"
    explanation: Directly supports the 85% frequency of EWS-FLI1 translocation and its structural details.
  - reference: PMID:17250957
    reference_title: "The Biology of Ewing sarcoma."
    supports: SUPPORT
    snippet: "resulting EWS-FLI-1 fusion protein is believed to behave as an aberrant"
    explanation: Supports the role of EWS-FLI1 as an aberrant transcription factor driving tumor development.
- name: BAF Complex Retargeting
  description: >-
    EWS-FLI1 uses the EWSR1 low-complexity/prion-like domain to retarget
    BRG1/BRM-associated factor (BAF/SWI-SNF) chromatin-remodeling complexes to
    tumor-specific enhancers. This neomorphic recruitment depends on tyrosine
    residues linked to phase-transition behavior of the EWSR1 domain and helps
    establish oncogenic enhancer activity.
  biological_processes:
  - preferred_term: chromatin remodeling
    modifier: ABNORMAL
    term:
      id: GO:0006338
      label: chromatin remodeling
  cellular_components:
  - preferred_term: chromatin
    term:
      id: GO:0000785
      label: chromatin
  downstream:
  - target: GGAA Microsatellite Enhancer Reprogramming
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      BAF retargeting supports tumor-specific enhancer activation downstream of
      EWS-FLI1 occupancy.
  evidence:
  - reference: PMID:28844694
    reference_title: "Cancer-Specific Retargeting of BAF Complexes by a Prion-like Domain."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "recruited by the EWS-FLI1 fusion protein to tumor-specific enhancers and"
    explanation: >-
      Demonstrates that EWS-FLI1 recruits BAF complexes to tumor-specific
      enhancers and that this recruitment contributes to gene activation.
  - reference: PMID:28844694
    reference_title: "Cancer-Specific Retargeting of BAF Complexes by a Prion-like Domain."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "necessary for phase transitions of the EWSR1 prion-like domain."
    explanation: >-
      Supports the phase-transition/prion-like-domain component of BAF
      retargeting by EWS-FLI1.
- name: EWS-FLI1 Hub and Dosage Control
  description: >-
    Endogenous EWS-FLI1 forms dynamic sub-diffraction chromatin hubs rather than
    stable macroscopic condensates. These hubs and downstream GGAA enhancer outputs
    are dosage-sensitive: a narrow range of low-complexity-domain interaction and
    fusion protein abundance supports oncogenic transcription, while excessive or
    insufficient EWS-FLI1 can alter differentiation, stress, survival, and metastatic
    plasticity.
  mechanism_confidence: PROVISIONAL
  genes:
  - preferred_term: EWSR1
    term:
      id: hgnc:3508
      label: EWSR1
  - preferred_term: FLI1
    term:
      id: hgnc:3749
      label: FLI1
  - preferred_term: TRIM8
    term:
      id: hgnc:15579
      label: TRIM8
  biological_processes:
  - preferred_term: regulation of gene expression
    modifier: ABNORMAL
    term:
      id: GO:0010468
      label: regulation of gene expression
  - preferred_term: protein ubiquitination
    modifier: ABNORMAL
    term:
      id: GO:0016567
      label: protein ubiquitination
  - preferred_term: protein stabilization
    modifier: DYSREGULATED
    term:
      id: GO:0050821
      label: protein stabilization
  downstream:
  - target: GGAA Microsatellite Enhancer Reprogramming
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      Dynamic EWS-FLI1 hubs concentrate the fusion on chromatin and tune
      enhancer activation at GGAA microsatellites.
  - target: Tumor Cell Proliferation and Survival
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - TRIM8-mediated EWS-FLI1 degradation
    - oncogene overdose avoidance
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      TRIM8-dependent fusion-protein turnover defines a tolerated oncogene dosage
      window required for Ewing sarcoma cell survival.
  - target: Metastatic Disease
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - submaximal EWS-FLI1 depletion
    - epithelial-mesenchymal plasticity
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      Graded EWS-FLI1 loss can produce non-linear phenotypes, including a
      pro-metastatic state at modest depletion.
  evidence:
  - reference: PMID:41659683
    reference_title: "Dynamic regulation of endogenous transcription factor hubs at single-molecule resolution."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "forms dynamic, sub-diffraction-limit hubs with mechanisms of dissolution that"
    explanation: Supports endogenous dynamic EWS-FLI1 hub formation rather than stable macroscopic condensates.
  - reference: PMID:35483357
    reference_title: "Tuning levels of low-complexity domain interactions to modulate endogenous oncogenic transcription."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "narrow optimum of LCD-LCD interactions to activate its target genes associated"
    explanation: Supports a narrow low-complexity-domain interaction window for oncogenic transcription.
  - reference: PMID:34329586
    reference_title: "TRIM8 modulates the EWS/FLI oncoprotein to promote survival in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "TRIM8 knockout led to an increase in EWS/FLI protein levels"
    explanation: Supports TRIM8-mediated control of EWS-FLI1 protein abundance and oncogene overdose.
  - reference: PMID:41484205
    reference_title: "Modelling EWS::FLI1 protein fluctuations reveal determinants of tumor plasticity in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "depletion promoted a pro-metastatic phenotype"
    explanation: Supports the non-linear dosage-plasticity edge linking submaximal EWS-FLI1 loss to metastatic behavior.
- name: GGAA Microsatellite Enhancer Reprogramming
  description: >-
    EWS-FLI1 binds GGAA microsatellite repeats and canonical ETS motifs,
    remodeling the enhancer landscape. At GGAA repeats, multimeric EWS-FLI1
    opens chromatin and creates de novo enhancers that contact target promoters;
    at conserved ETS enhancers, EWS-FLI1 can displace wild-type ETS factors and
    repress tumor suppressor and lineage-regulatory programs.
  biological_processes:
  - preferred_term: regulation of gene expression
    modifier: ABNORMAL
    term:
      id: GO:0010468
      label: regulation of gene expression
  - preferred_term: chromatin remodeling
    modifier: ABNORMAL
    term:
      id: GO:0006338
      label: chromatin remodeling
  cellular_components:
  - preferred_term: chromatin
    term:
      id: GO:0000785
      label: chromatin
  downstream:
  - target: Core Regulatory Circuitry Activation
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      EWS-FLI1 establishes super-enhancers for KLF15, TCF4, and NKX2-2, building
      an autoregulatory transcription-factor circuit.
  - target: Blocked Differentiation
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: Aberrant enhancer repression suppresses mesenchymal lineage regulators.
  - target: STAG2-Modified Enhancer State
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - cohesin-dependent enhancer-promoter contacts
    hypothesis_groups:
    - cohesin_modified_high_risk_model
    description: >-
      STAG2 loss reshapes EWS-FLI1 occupancy across monomeric and multimeric
      GGAA-repeat enhancer classes.
  - target: ETV6 GGAA Counter-Regulation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - competition at short GGAA repeats
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      Native ETS factor ETV6 competes with EWS-FLI1 at short GGAA repeats and
      restrains a subset of fusion-driven enhancer activity.
  evidence:
  - reference: PMID:25453903
    reference_title: "EWS-FLI1 utilizes divergent chromatin remodeling mechanisms to directly activate or repress enhancer elements in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "reprograms gene regulatory circuits in Ewing sarcoma by directly inducing or"
    explanation: Directly supports enhancer-level reprogramming as a central EWS-FLI1 mechanism.
  - reference: PMID:25453903
    reference_title: "EWS-FLI1 utilizes divergent chromatin remodeling mechanisms to directly activate or repress enhancer elements in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "induce chromatin opening and create de novo enhancers that physically interact"
    explanation: Supports GGAA-repeat enhancer creation and chromatin opening.
  - reference: PMID:22086061
    reference_title: "Tumor-specific retargeting of an oncogenic transcription factor chimera results in dysregulation of chromatin and transcription."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "EWS-FLI targets regions of the genome"
    explanation: Supports Ian Davis lab evidence that the fusion retargets chromatin differently from wild-type FLI1.
  - reference: PMID:22086061
    reference_title: "Tumor-specific retargeting of an oncogenic transcription factor chimera results in dysregulation of chromatin and transcription."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Expression of EWS-FLI results in nucleosome depletion at targeted sites"
    explanation: Supports the chromatin-accessibility arm of the EWS-FLI1 enhanceropathy.
  - reference: PMID:41950086
    reference_title: "STAG2 loss amplifies EWS-FLI1-driven microsatellite enhancer activity promoting Ewing sarcoma aggressiveness."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "EWS-FLI1 engages GGAA microsatellite repeats to"
    explanation: Confirms the GGAA microsatellite enhancer mechanism in a recent STAG2-focused study.
  - reference: PMID:28134926
    reference_title: "DNA methylation heterogeneity defines a disease spectrum in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "DNA hypomethylation at enhancers regulated"
    explanation: Supports enhancer reprogramming as a recurrent epigenomic feature in patient tumors.
- name: ETV6 GGAA Counter-Regulation
  description: >-
    ETV6 is a native ETS-family factor that competes with EWS-FLI1 at select
    short GGAA-repeat elements. This counter-regulatory layer restrains part of
    the enhanceropathy, and forced ETV6 degradation can paradoxically increase
    EWS-FLI1 transcriptional stress and tumor cell death.
  mechanism_confidence: PROVISIONAL
  genes:
  - preferred_term: ETV6
    term:
      id: hgnc:3495
      label: ETV6
  biological_processes:
  - preferred_term: regulation of gene expression
    modifier: ABNORMAL
    term:
      id: GO:0010468
      label: regulation of gene expression
  downstream:
  - target: GGAA Microsatellite Enhancer Reprogramming
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      ETV6 competition modulates EWS-FLI1 occupancy and output at short GGAA
      microsatellite enhancers.
  - target: Tumor Cell Proliferation and Survival
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - EWS-FLI1 hyperactivation
    - cellular stress
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      ETV6 perturbation can increase EWS-FLI1-driven transcriptional stress and
      suppress tumor growth in preclinical models.
  evidence:
  - reference: PMID:36658219
    reference_title: "ETV6 dependency in Ewing sarcoma by antagonism of EWS-FLI1-mediated enhancer activation."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "with EWS-FLI1 for binding to select DNA elements enriched for short GGAA repeat"
    explanation: Supports ETV6 competition with EWS-FLI1 at short GGAA-repeat elements.
  - reference: PMID:40215343
    reference_title: "(GGAA)(3)-Based TF-PROTACs Enable Targeted Degradation of ETV6 to Inhibit Ewing Sarcoma Growth."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "EWS::FLI1 at short GGAA repeats to restrain"
    explanation: Supports ETV6 as a restraining factor and therapeutic vulnerability.
- name: GGAA Microsatellite Germline Susceptibility Architecture
  description: >-
    Germline variation in GGAA microsatellite architecture can determine how
    strongly the acquired EWS-FLI1 fusion converts a locus into a neo-enhancer.
    At EGR2 and RREB1 susceptibility loci, longer or newly contiguous GGAA repeat
    alleles increase EWS-FLI1 binding and enhancer output, linking inherited
    repeat length to the somatic enhanceropathy and proliferative transcriptional
    programs.
  mechanism_confidence: PROVISIONAL
  genes:
  - preferred_term: EGR2
    term:
      id: hgnc:3239
      label: EGR2
  - preferred_term: RREB1
    term:
      id: hgnc:10449
      label: RREB1
  biological_processes:
  - preferred_term: regulation of gene expression
    modifier: ABNORMAL
    term:
      id: GO:0010468
      label: regulation of gene expression
  - preferred_term: chromatin remodeling
    modifier: ABNORMAL
    term:
      id: GO:0006338
      label: chromatin remodeling
  - preferred_term: cell population proliferation
    modifier: INCREASED
    term:
      id: GO:0008283
      label: cell population proliferation
  downstream:
  - target: GGAA Microsatellite Enhancer Reprogramming
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    - cell_of_origin_context_model
    description: >-
      Germline GGAA repeat length and purity alter the strength of EWS-FLI1
      neo-enhancer formation at susceptible loci.
  - target: Tumor Cell Proliferation and Survival
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - EGR2 enhancer activation
    - RREB1-mediated RAS/MAPK-associated transcription
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    - cell_of_origin_context_model
    description: >-
      Susceptibility-locus enhancer activation can increase expression of
      proliferation-associated transcriptional regulators.
  evidence:
  - reference: PMID:26214589
    reference_title: "Chimeric EWSR1-FLI1 regulates the Ewing sarcoma susceptibility gene EGR2 via a GGAA microsatellite."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "A risk allele connected adjacent GGAA repeats by"
    explanation: Supports the mechanism by which a germline risk allele creates a stronger GGAA enhancer at EGR2.
  - reference: PMID:26214589
    reference_title: "Chimeric EWSR1-FLI1 regulates the Ewing sarcoma susceptibility gene EGR2 via a GGAA microsatellite."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "EWSR1-FLI1 preferentially bound to the A risk allele"
    explanation: Supports allele-specific EWS-FLI1 binding at a germline susceptibility repeat.
  - reference: PMID:36787739
    reference_title: "Targeted long-read sequencing of the Ewing sarcoma 6p25.1 susceptibility locus identifies germline-somatic interactions with EWSR1-FLI1 binding."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "had longer alleles (>135"
    explanation: Supports longer germline GGAA alleles in Ewing sarcoma cases at the RREB1-associated susceptibility locus.
  - reference: PMID:36787739
    reference_title: "Targeted long-read sequencing of the Ewing sarcoma 6p25.1 susceptibility locus identifies germline-somatic interactions with EWSR1-FLI1 binding."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "RREB1 knockdown reduced proliferation and clonogenic potential"
    explanation: Links the RREB1 susceptibility enhancer mechanism to proliferation and clonogenic growth.
- name: NuRD/CHD4 Repressive Chromatin Program
  description: >-
    EWS-FLI1 is not only an enhancer-activating transcription factor; it also
    directly represses tumor-suppressive and lineage-regulatory loci through
    NuRD-associated chromatin machinery. CHD4/NuRD and LSD1/HDAC functions support
    EWS-FLI1-mediated repression, global chromatin architecture, survival, and
    protection from spontaneous DNA damage.
  genes:
  - preferred_term: CHD4
    term:
      id: hgnc:1919
      label: CHD4
  biological_processes:
  - preferred_term: negative regulation of transcription by RNA polymerase II
    modifier: ABNORMAL
    term:
      id: GO:0000122
      label: negative regulation of transcription by RNA polymerase II
  - preferred_term: chromatin organization
    modifier: ABNORMAL
    term:
      id: GO:0006325
      label: chromatin organization
  - preferred_term: DNA repair
    modifier: ABNORMAL
    term:
      id: GO:0006281
      label: DNA repair
  downstream:
  - target: Blocked Differentiation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - repression of lineage-regulatory genes
    - repression of tumor-suppressive target genes
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      NuRD/LSD1/HDAC-mediated repression helps EWS-FLI1 maintain an immature,
      transformed state.
  - target: Tumor Cell Proliferation and Survival
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - CHD4-dependent chromatin architecture maintenance
    - suppression of spontaneous DNA damage
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    - replication_stress_vulnerability_model
    description: >-
      CHD4/NuRD dependence links the transcriptional pathograph to DNA-damage
      buffering and tumor cell survival.
  evidence:
  - reference: PMID:23178492
    reference_title: "Mechanism and relevance of EWS/FLI-mediated transcriptional repression in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "transcriptional repression by EWS/FLI is mediated through direct binding of the NuRD complex"
    explanation: Supports the direct EWS-FLI1-NuRD repressive arm of the pathograph.
  - reference: PMID:23178492
    reference_title: "Mechanism and relevance of EWS/FLI-mediated transcriptional repression in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "the repressive function of EWS/FLI is absolutely required for the oncogenic function"
    explanation: Supports the need to represent repression as a causal oncogenic arm, not only as a side effect.
  - reference: PMID:37963210
    reference_title: "The Chromatin Remodeler CHD4 Sustains Ewing Sarcoma Cell Survival by Controlling Global Chromatin Architecture."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "induced tumor cell death by apoptosis and abolished colony formation"
    explanation: Supports CHD4/NuRD as a survival dependency in Ewing sarcoma cells.
  - reference: PMID:24963049
    reference_title: "Reversible LSD1 inhibition interferes with global EWS/ETS transcriptional activity and impedes Ewing sarcoma tumor growth."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "utilizes lysine-specific demethylase 1 (LSD1) to"
    explanation: Supports LSD1 as part of the EWS/ETS repressive chromatin arm and as a therapeutic vulnerability.
- name: Core Regulatory Circuitry Activation
  description: >-
    EWS-FLI1 activates super-enhancers controlling a core regulatory circuitry
    composed of transcription factors including KLF15, TCF4, and NKX2-2. These
    factors reinforce their own and each other's regulatory elements and cooperate
    with EWS-FLI1 to sustain proliferation, survival signaling, and the Ewing
    transcriptional state.
  genes:
  - preferred_term: KLF15
    term:
      id: hgnc:14536
      label: KLF15
  - preferred_term: TCF4
    term:
      id: hgnc:11634
      label: TCF4
  - preferred_term: NKX2-2
    term:
      id: hgnc:7835
      label: NKX2-2
  biological_processes:
  - preferred_term: regulation of gene expression
    modifier: ABNORMAL
    term:
      id: GO:0010468
      label: regulation of gene expression
  - preferred_term: cell population proliferation
    modifier: INCREASED
    term:
      id: GO:0008283
      label: cell population proliferation
  downstream:
  - target: Tumor Cell Proliferation and Survival
    causal_link_type: DIRECT
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      Core regulatory transcription factors sustain proliferation and oncogenic
      signaling pathways in Ewing sarcoma cells.
  - target: Blocked Differentiation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - NKX2-2-mediated repression of mesenchymal features
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: Core regulatory circuitry reinforces the undifferentiated tumor state.
  evidence:
  - reference: PMID:33080033
    reference_title: "EWS-FLI1 regulates and cooperates with core regulatory circuitry in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "each of these three TFs to activate their transcription."
    explanation: >-
      Supports direct establishment of KLF15, TCF4, and NKX2-2 super-enhancers
      by EWS-FLI1.
  - reference: PMID:33080033
    reference_title: "EWS-FLI1 regulates and cooperates with core regulatory circuitry in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "contribute significantly to cell proliferation of Ewing sarcoma both in vitro"
    explanation: Supports the downstream proliferation role of the core regulatory circuitry.
- name: Blocked Differentiation
  description: >-
    EWS-FLI1 and its downstream transcriptional circuitry repress mesenchymal
    lineage regulators, maintaining Ewing sarcoma cells in an immature,
    proliferative state. This mechanism is linked to the unresolved cell-of-origin
    question because only some early progenitor contexts tolerate EWS-FLI1 and
    progress toward an Ewing-like state.
  biological_processes:
  - preferred_term: cell differentiation
    modifier: DECREASED
    term:
      id: GO:0030154
      label: cell differentiation
  - preferred_term: mesenchymal cell differentiation
    modifier: DECREASED
    term:
      id: GO:0048762
      label: mesenchymal cell differentiation
  evidence:
  - reference: PMID:26000096
    reference_title: "EWS/FLI utilizes NKX2-2 to repress mesenchymal features of Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "NKX2-2 mediates the EWS/FLI-controlled block of mesenchymal features."
    explanation: Directly supports EWS/FLI-mediated repression of mesenchymal features and blocked differentiation programs.
  - reference: PMID:25453903
    reference_title: "EWS-FLI1 utilizes divergent chromatin remodeling mechanisms to directly activate or repress enhancer elements in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "and mesenchymal lineage regulators while activating oncogenes and potential"
    explanation: Supports enhancer-level repression of mesenchymal lineage regulators.
- name: ATF4-Serine-Glycine Metabolic Reprogramming
  description: >-
    EWS-FLI1 and menin converge on ATF4 to activate a serine synthesis pathway
    transcriptional program. EWS-FLI1 also upregulates glutamine uptake and
    one-carbon cycle genes, linking fusion-driven transcription to biosynthetic
    metabolism, redox state, and survival.
  genes:
  - preferred_term: ATF4
    term:
      id: hgnc:786
      label: ATF4
  - preferred_term: PHGDH
    term:
      id: hgnc:8923
      label: PHGDH
  - preferred_term: SLC1A5
    term:
      id: hgnc:10943
      label: SLC1A5
  biological_processes:
  - preferred_term: L-serine biosynthetic process
    modifier: INCREASED
    term:
      id: GO:0006564
      label: L-serine biosynthetic process
  - preferred_term: L-glutamine transport
    modifier: INCREASED
    term:
      id: GO:0006868
      label: L-glutamine transport
  - preferred_term: generation of precursor metabolites and energy
    modifier: ABNORMAL
    term:
      id: GO:0006091
      label: generation of precursor metabolites and energy
  downstream:
  - target: Tumor Cell Proliferation and Survival
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - serine-glycine biosynthesis
    - glutamine uptake
    - one-carbon metabolism
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: >-
      Fusion-driven metabolic rewiring supports biomass production, redox state,
      and survival in rapidly proliferating tumor cells.
  evidence:
  - reference: PMID:33741715
    reference_title: "EWS-FLI1 and Menin Converge to Regulate ATF4 Activity in Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "directly activate ATF4 transcription."
    explanation: Supports direct fusion-driven ATF4 activation.
  - reference: PMID:29873416
    reference_title: "EWS-FLI1 reprograms the metabolism of Ewing sarcoma cells via positive regulation of glutamine import and serine-glycine biosynthesis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "required for serine-glycine biosynthesis and uptake of the alternative nutrient"
    explanation: Supports direct EWS-FLI1 control of serine-glycine biosynthesis and glutamine uptake.
  - reference: PMID:29873416
    reference_title: "EWS-FLI1 reprograms the metabolism of Ewing sarcoma cells via positive regulation of glutamine import and serine-glycine biosynthesis."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "serine-glycine metabolism or glutamine uptake are potential targetable"
    explanation: Supports the therapeutic-vulnerability interpretation of this metabolic mechanism.
- name: Replication Stress and Impaired Homologous Recombination
  conforms_to: "dna_repair_synthetic_lethality#PARP and Platinum Synthetic Lethality"
  description: >-
    EWS-FLI1-driven high-output transcription alters the response to DNA damage,
    increases R-loop accumulation and replication stress, and impairs BRCA1-linked
    homologous recombination. Survival under this stress state can depend on
    factors such as USP1 and survivin, creating both chemotherapy sensitivity and
    resistance-adaptation questions.
  genes:
  - preferred_term: BRCA1
    term:
      id: hgnc:1100
      label: BRCA1
  - preferred_term: USP1
    term:
      id: hgnc:12607
      label: USP1
  - preferred_term: BIRC5
    term:
      id: hgnc:593
      label: BIRC5
  biological_processes:
  - preferred_term: DNA replication
    modifier: DYSREGULATED
    term:
      id: GO:0006260
      label: DNA replication
  - preferred_term: double-strand break repair via homologous recombination
    modifier: DECREASED
    term:
      id: GO:0000724
      label: double-strand break repair via homologous recombination
  - preferred_term: DNA repair
    modifier: DECREASED
    term:
      id: GO:0006281
      label: DNA repair
  downstream:
  - target: Tumor Cell Proliferation and Survival
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - USP1-driven survivin stabilization
    - suppression of replication-stress-induced apoptosis
    hypothesis_groups:
    - replication_stress_vulnerability_model
    description: >-
      Replication stress creates a survival bottleneck that Ewing sarcoma cells
      can buffer through USP1-survivin signaling.
  evidence:
  - reference: PMID:29513652
    reference_title: "EWS-FLI1 increases transcription to cause R-loops and block BRCA1 repair in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "damage-induced transcription, accumulation of R-loops and increased replication"
    explanation: Supports R-loop accumulation and replication stress downstream of EWS-FLI1 activity.
  - reference: PMID:29513652
    reference_title: "EWS-FLI1 increases transcription to cause R-loops and block BRCA1 repair in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "homologous recombination is impaired in Ewing sarcoma"
    explanation: Supports the homologous-recombination defect in this node.
  - reference: PMID:37478161
    reference_title: "USP1 Expression Driven by EWS::FLI1 Transcription Factor Stabilizes Survivin and Mitigates Replication Stress in Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "USP1-Survivin axis promotes EWS cell survival, and USP1 inhibition sensitizes"
    explanation: Supports the survival adaptation downstream of replication stress.
- name: R-loop Resolution and Replication-Fork Vulnerability
  description: >-
    EWS-FLI1 creates a replication-stress vulnerability through more than bulk
    transcriptional load. It can sequester the DHX9 helicase and impair R-loop
    resolution after topoisomerase stress, while also directly increasing SLFN11
    expression. SLFN11 then blocks stressed replication forks, linking the fusion
    program to chemotherapy sensitivity, resistance through DHX9 or SLFN11 state,
    and the broader DNA-damage response pathograph.
  mechanism_confidence: PROVISIONAL
  genes:
  - preferred_term: EWSR1
    term:
      id: hgnc:3508
      label: EWSR1
  - preferred_term: FLI1
    term:
      id: hgnc:3749
      label: FLI1
  - preferred_term: DHX9
    term:
      id: hgnc:2750
      label: DHX9
  - preferred_term: SLFN11
    term:
      id: hgnc:26633
      label: SLFN11
  biological_processes:
  - preferred_term: DNA replication
    modifier: DYSREGULATED
    term:
      id: GO:0006260
      label: DNA replication
  - preferred_term: DNA damage checkpoint signaling
    modifier: ABNORMAL
    term:
      id: GO:0000077
      label: DNA damage checkpoint signaling
  - preferred_term: DNA repair
    modifier: ABNORMAL
    term:
      id: GO:0006281
      label: DNA repair
  downstream:
  - target: Replication Stress and Impaired Homologous Recombination
    causal_link_type: DIRECT
    hypothesis_groups:
    - replication_stress_vulnerability_model
    description: >-
      DHX9 sequestration increases unresolved R-loops, and SLFN11 blocks fork
      progression when replication is stressed.
  - target: Tumor Cell Proliferation and Survival
    causal_link_type: UNKNOWN
    hypothesis_groups:
    - replication_stress_vulnerability_model
    description: >-
      The same R-loop and fork-blocking state can increase treatment sensitivity
      or select resistant cells with altered DHX9 or SLFN11 activity.
  evidence:
  - reference: PMID:40721661
    reference_title: "EWS::FLI1-DHX9 interaction promotes Ewing sarcoma sensitivity to DNA topoisomerase 1 poisons by altering R-loop metabolism."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "sequestering DHX9 helicase, ultimately resulting in"
    explanation: Supports the direct DHX9-sequestration arm of the R-loop mechanism.
  - reference: PMID:25779942
    reference_title: "SLFN11 Is a Transcriptional Target of EWS-FLI1 and a Determinant of Drug Response in Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "EWS-FLI1 binds near the transcription start site of SLFN11 promoter"
    explanation: Supports SLFN11 as a direct EWS-FLI1 transcriptional target.
  - reference: PMID:25779942
    reference_title: "SLFN11 Is a Transcriptional Target of EWS-FLI1 and a Determinant of Drug Response in Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "patients with higher SLFN11 expression showed better"
    explanation: Supports clinical relevance of SLFN11 expression for outcome in Ewing sarcoma.
  - reference: PMID:29395061
    reference_title: "SLFN11 Blocks Stressed Replication Forks Independently of ATR."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "selectively blocks fork progression while inducing chromatin opening"
    explanation: Supports the fork-blocking mechanism downstream of SLFN11.
- name: STAG2-Modified Enhancer State
  description: >-
    Loss-of-function STAG2 alterations in a subset of Ewing sarcomas reshape
    cohesin-dependent chromatin architecture, EWS-FLI1 enhancer occupancy, and
    DNA-damage response state. Current evidence supports a model in which STAG2
    loss selectively amplifies multimeric GGAA microsatellite enhancer programs
    while also altering PRC2- and CTCF-dependent contacts. Clinically, STAG2
    protein loss and STAG2/TP53 co-alteration mark high-risk disease, but the
    relative contributions of enhancer amplification, PRC2 derepression, and
    replication-fork vulnerability remain unresolved.
  mechanism_confidence: PROVISIONAL
  genes:
  - preferred_term: STAG2
    term:
      id: hgnc:11355
      label: STAG2
  biological_processes:
  - preferred_term: chromatin remodeling
    modifier: ABNORMAL
    term:
      id: GO:0006338
      label: chromatin remodeling
  - preferred_term: chromosome organization
    modifier: ABNORMAL
    term:
      id: GO:0051276
      label: chromosome organization
  - preferred_term: regulation of gene expression
    modifier: ABNORMAL
    term:
      id: GO:0010468
      label: regulation of gene expression
  - preferred_term: DNA replication
    modifier: DYSREGULATED
    term:
      id: GO:0006260
      label: DNA replication
  - preferred_term: DNA repair
    modifier: ABNORMAL
    term:
      id: GO:0006281
      label: DNA repair
  downstream:
  - target: GGAA Microsatellite Enhancer Reprogramming
    causal_link_type: DIRECT
    hypothesis_groups:
    - cohesin_modified_high_risk_model
    description: >-
      STAG2/cohesin status changes enhancer-promoter communication at long
      EWS-FLI1-bound GGAA repeats and rewires enhancer output.
  - target: Replication Stress and Impaired Homologous Recombination
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - replication fork stalling
    - homologous-recombination impairment
    hypothesis_groups:
    - cohesin_modified_high_risk_model
    - replication_stress_vulnerability_model
    description: >-
      STAG2 loss can compound the fusion-driven DNA-damage state through
      replication-fork and homologous-recombination vulnerabilities.
  - target: Metastatic Disease
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - altered enhancer-promoter contacts
    - PRC2 derepression
    - migratory and neurodevelopmental program rewiring
    hypothesis_groups:
    - cohesin_modified_high_risk_model
    description: STAG2 loss can promote an aggressive, metastasis-prone transcriptional state.
  evidence:
  - reference: PMID:34129824
    reference_title: "STAG2 loss rewires oncogenic and developmental programs to promote metastasis in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "contacts. Moreover, loss of STAG2 also disrupted PRC2-mediated regulation of"
    explanation: Supports STAG2 loss as a chromatin and transcriptional rewiring mechanism.
  - reference: PMID:34129824
    reference_title: "STAG2 loss rewires oncogenic and developmental programs to promote metastasis in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "the metastatic potential of Ewing sarcoma xenografts."
    explanation: Supports the metastasis-promoting consequence in xenograft models.
  - reference: PMID:41950086
    reference_title: "STAG2 loss amplifies EWS-FLI1-driven microsatellite enhancer activity promoting Ewing sarcoma aggressiveness."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "rather than globally attenuates, EWS-FLI1 function, amplifying a high-risk"
    explanation: Supports the current model that STAG2 loss changes the quality of EWS-FLI1 enhancer activity.
  - reference: PMID:39487368
    reference_title: "STAG2 loss in Ewing sarcoma alters enhancer-promoter contacts dependent and independent of EWS::FLI1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "cohesin-STAG2 facilitates communication between"
    explanation: Supports STAG2/cohesin control of long-GGAA neo-enhancer to promoter communication.
  - reference: PMID:39487368
    reference_title: "STAG2 loss in Ewing sarcoma alters enhancer-promoter contacts dependent and independent of EWS::FLI1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Changes in CTCF-dependent chromatin contacts involving"
    explanation: Supports an EWS-FLI1-independent CTCF-contact arm of STAG2 loss.
  - reference: PMID:36221002
    reference_title: "Adverse prognostic impact of the loss of STAG2 protein expression in patients with newly diagnosed localised Ewing sarcoma: A report from the Children's Oncology Group."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "5-year event-free survival was 54% (95% CI 34-70%) and"
    explanation: Supports adverse clinical prognosis associated with STAG2 protein loss in localized Ewing sarcoma.
  - reference: PMID:25223734
    reference_title: "Genomic landscape of Ewing sarcoma defines an aggressive subtype with co-association of STAG2 and TP53 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "STAG2 and TP53 mutations are often"
    explanation: Supports the high-risk STAG2/TP53 co-alteration component of the model.
  - reference: PMID:30975996
    reference_title: "A requirement for STAG2 in replication fork progression creates a targetable synthetic lethality in cohesin-mutant cancers."
    supports: PARTIAL
    evidence_source: IN_VITRO
    snippet: "for DNA replication fork progression"
    explanation: Supports the replication-fork vulnerability arm, with broader cancer models including an Ewing sarcoma isogenic pair.
  - reference: PMID:37985839
    reference_title: "STAG2 Regulates Homologous Recombination Repair and Sensitivity to ATM Inhibition."
    supports: PARTIAL
    evidence_source: IN_VITRO
    snippet: "reducing homologous recombination (HR) repair"
    explanation: Supports a STAG2-linked homologous-recombination vulnerability that may compound Ewing sarcoma replication stress.
- name: Tumor Cell Proliferation and Survival
  description: >-
    Multiple fusion-driven mechanisms converge on tumor cell proliferation and
    survival: core regulatory circuitry sustains oncogenic signaling, metabolic
    reprogramming supplies biomass and redox buffering, and replication-stress
    adaptation prevents apoptosis during genotoxic stress.
  biological_processes:
  - preferred_term: cell population proliferation
    modifier: INCREASED
    term:
      id: GO:0008283
      label: cell population proliferation
  downstream:
  - target: Soft Tissue Mass / Localized Swelling
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - expansion of poorly differentiated malignant cells
    hypothesis_groups:
    - canonical_fusion_enhanceropathy_model
    description: Sustained proliferation and impaired differentiation produce the expanding local tumor mass.
  - target: Metastatic Disease
    causal_link_type: UNKNOWN
    hypothesis_groups:
    - cohesin_modified_high_risk_model
    - replication_stress_vulnerability_model
    description: >-
      Which survival and stress-adaptation states drive dissemination and relapse
      remains incompletely resolved.
- name: Permissive Progenitor Cell State
  description: >-
    The cell of origin remains unresolved. Mesenchymal stem/progenitor and neural
    crest-derived progenitor models support the hypothesis that EWS-FLI1 is
    oncogenic only in specific early developmental cell states with permissive
    chromatin and differentiation programs. A 2025 embryonic mesenchymal stem
    cell model supports transformation from undifferentiated early heMSCs, while
    earlier work supports neural crest-related states as Ewing-like.
  mechanism_confidence: PROVISIONAL
  cell_types:
  - preferred_term: early mesenchymal stem cell
    term:
      id: CL:0000134
      label: mesenchymal stem cell
  - preferred_term: migratory neural crest cell
    term:
      id: CL:0000333
      label: migratory neural crest cell
  biological_processes:
  - preferred_term: cell differentiation
    modifier: ABNORMAL
    term:
      id: GO:0030154
      label: cell differentiation
  downstream:
  - target: EWS-FLI1 Fusion Oncogene
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - cell_of_origin_context_model
    description: >-
      The progenitor chromatin state is hypothesized to determine whether
      EWS-FLI1 expression is tolerated and can initiate an Ewing-like program.
  - target: GGAA Microsatellite Enhancer Reprogramming
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - cell_of_origin_context_model
    description: >-
      Developmental chromatin context may determine which GGAA microsatellites
      become functional EWS-FLI1 enhancers.
  - target: IGF-1/YAP1 Developmental Cooperation
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - pubertal IGF-1 exposure
    - YAP1/TEAD transcriptional signaling
    hypothesis_groups:
    - cell_of_origin_context_model
    description: >-
      Growth-factor signaling in a permissive mesenchymal developmental window
      may convert EWS-FLI1 expression from toxic or malformed development into
      stable malignant transformation.
  evidence:
  - reference: PMID:21559395
    reference_title: "Modeling initiation of Ewing sarcoma in human neural crest cells."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "cells have been implicated as cells of origin."
    explanation: Supports the leading mesenchymal and neural crest cell-of-origin hypotheses.
  - reference: PMID:21559395
    reference_title: "Modeling initiation of Ewing sarcoma in human neural crest cells."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "initiates transition to an ESFT-like state."
    explanation: Supports the ability of EWS-FLI1 to initiate an Ewing-like state in neural crest-related cells.
  - reference: PMID:41136396
    reference_title: "EWS::FLI1 expression in human embryonic mesenchymal stem cells leads to transcriptional reprograming, defective DNA damage repair and Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "by EWSR::ETS rearrangements whose cellular origin remains unclear."
    explanation: Establishes the unresolved nature of the cell-of-origin question.
  - reference: PMID:41136396
    reference_title: "EWS::FLI1 expression in human embryonic mesenchymal stem cells leads to transcriptional reprograming, defective DNA damage repair and Ewing sarcoma."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "heMSCs results in the formation of tumors expressing characteristic ES markers."
    explanation: Supports the embryonic mesenchymal stem-cell transformation model in xenografts.
- name: IGF-1/YAP1 Developmental Cooperation
  description: >-
    Pubertal IGF-1 signaling is a proposed non-genetic cooperating mechanism
    that can reprogram EWS-FLI1-mutant mesenchymal cells toward stable
    transformation through YAP1/TEAD activity. This mechanism helps explain the
    adolescent age peak and the rarity of recurrent cooperating mutations, but
    it remains to be validated across human progenitor systems and across
    established tumor maintenance states.
  mechanism_confidence: PROVISIONAL
  cell_types:
  - preferred_term: limb-derived mesenchymal progenitor cell
    term:
      id: CL:0000134
      label: mesenchymal stem cell
  genes:
  - preferred_term: IGF1
    term:
      id: hgnc:5464
      label: IGF1
  - preferred_term: YAP1
    term:
      id: hgnc:16262
      label: YAP1
  biological_processes:
  - preferred_term: insulin-like growth factor receptor signaling pathway
    modifier: INCREASED
    term:
      id: GO:0048009
      label: insulin-like growth factor receptor signaling pathway
  - preferred_term: intracellular signal transduction
    modifier: ABNORMAL
    term:
      id: GO:0035556
      label: intracellular signal transduction
  - preferred_term: cell fate commitment
    modifier: ABNORMAL
    term:
      id: GO:0045165
      label: cell fate commitment
  downstream:
  - target: Tumor Cell Proliferation and Survival
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - YAP1/TEAD transcriptional activity
    - stable transformation of EWS-FLI1-mutant mesenchymal cells
    hypothesis_groups:
    - cell_of_origin_context_model
    description: >-
      IGF-1/YAP1 signaling can cooperate with EWS-FLI1 to promote stable
      transformation and tumorigenicity in a developmental mesenchymal context.
  - target: Blocked Differentiation
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    hypothesis_groups:
    - cell_of_origin_context_model
    description: >-
      The developmental signaling state may help lock EWS-FLI1-expressing
      progenitors into an aberrant fate rather than normal mesenchymal
      differentiation.
  evidence:
  - reference: PMID:40080499
    reference_title: "YAP1 is a key regulator of EWS::FLI1-dependent malignant transformation upon IGF-1-mediated reprogramming of bone mesenchymal stem cells."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "concentrations mimicking serum levels during puberty"
    explanation: Supports pubertal-level IGF-1 exposure as a cooperating developmental signal.
  - reference: PMID:40080499
    reference_title: "YAP1 is a key regulator of EWS::FLI1-dependent malignant transformation upon IGF-1-mediated reprogramming of bone mesenchymal stem cells."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "Yap1 plays a central role."
    explanation: Supports YAP1 as the central mediator of the IGF-1 cooperating mechanism.
mechanistic_hypotheses:
- hypothesis_group_id: canonical_fusion_enhanceropathy_model
  hypothesis_label: Canonical EWS-FLI1 fusion enhanceropathy model
  status: CANONICAL
  description: >-
    EWS-FLI1 is the truncal disease driver. Its EWSR1 low-complexity domain and
    FLI1 DNA-binding domain form dosage-sensitive chromatin hubs and retarget
    chromatin machinery to GGAA microsatellites and ETS elements. The mechanism
    includes BAF-supported enhancer activation, NuRD/CHD4-associated repression,
    ETV6 counter-regulation at short GGAA repeats, core regulatory circuitry,
    blocked differentiation, metabolic rewiring, and proliferation.
  evidence:
  - reference: PMID:25453903
    reference_title: "EWS-FLI1 utilizes divergent chromatin remodeling mechanisms to directly activate or repress enhancer elements in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "EWS-FLI1 establishes an oncogenic regulatory program governing both tumor"
    explanation: Supports the canonical fusion enhanceropathy model.
  - reference: PMID:41659683
    reference_title: "Dynamic regulation of endogenous transcription factor hubs at single-molecule resolution."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "forms dynamic, sub-diffraction-limit hubs with mechanisms of dissolution that"
    explanation: Supports dynamic endogenous EWS-FLI1 hub formation as a refinement of the canonical model.
  - reference: PMID:23178492
    reference_title: "Mechanism and relevance of EWS/FLI-mediated transcriptional repression in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "the repressive function of EWS/FLI is absolutely required for the oncogenic function"
    explanation: Supports including direct transcriptional repression in the canonical mechanism.
  - reference: PMID:40215343
    reference_title: "(GGAA)(3)-Based TF-PROTACs Enable Targeted Degradation of ETV6 to Inhibit Ewing Sarcoma Growth."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "EWS::FLI1 at short GGAA repeats to restrain"
    explanation: Supports ETV6 as a counter-regulatory modifier of the GGAA enhanceropathy.
- hypothesis_group_id: cell_of_origin_context_model
  hypothesis_label: Permissive developmental cell-of-origin model
  status: EMERGING
  description: >-
    EWS-FLI1 transformation depends on developmental timing, progenitor state,
    inherited GGAA repeat architecture, and cooperating developmental signals.
    Neural crest-related and embryonic mesenchymal progenitors are leading
    candidates, and IGF-1/YAP1 signaling is a new non-genetic cooperating
    mechanism, but the decisive human chromatin and differentiation-state
    features remain unresolved.
  evidence:
  - reference: PMID:41136396
    reference_title: "EWS::FLI1 expression in human embryonic mesenchymal stem cells leads to transcriptional reprograming, defective DNA damage repair and Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "is able to endow transforming capacity when expressed in undifferentiated, early"
    explanation: Supports the developmental-context hypothesis in embryonic mesenchymal stem cells.
  - reference: PMID:40080499
    reference_title: "YAP1 is a key regulator of EWS::FLI1-dependent malignant transformation upon IGF-1-mediated reprogramming of bone mesenchymal stem cells."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "concentrations mimicking serum levels during puberty"
    explanation: Supports IGF-1/YAP1 signaling as a developmental cooperating mechanism.
  - reference: PMID:36787739
    reference_title: "Targeted long-read sequencing of the Ewing sarcoma 6p25.1 susceptibility locus identifies germline-somatic interactions with EWSR1-FLI1 binding."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "germline microsatellite variation at the 6p25.1 EwS"
    explanation: Supports inherited GGAA microsatellite architecture as part of the permissive-context model.
- hypothesis_group_id: replication_stress_vulnerability_model
  hypothesis_label: Transcription-coupled replication stress vulnerability model
  status: ALTERNATIVE
  description: >-
    EWS-FLI1-induced transcription creates R-loops, replication stress, and
    BRCA1-linked repair defects. The model is best represented as a superimposed
    vulnerability framework with DHX9-dependent R-loop resolution, direct SLFN11
    activation and fork blocking, USP1-survivin stress buffering, and possible
    repair-pathway defects. These arms may explain sensitivity to genotoxic
    therapy and resistance adaptation.
  evidence:
  - reference: PMID:29513652
    reference_title: "EWS-FLI1 increases transcription to cause R-loops and block BRCA1 repair in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "mechanistic basis of the sensitivity of Ewing sarcoma to chemotherapy (including"
    explanation: Supports the replication-stress vulnerability model.
  - reference: PMID:40721661
    reference_title: "EWS::FLI1-DHX9 interaction promotes Ewing sarcoma sensitivity to DNA topoisomerase 1 poisons by altering R-loop metabolism."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "sequestering DHX9 helicase, ultimately resulting in"
    explanation: Supports the DHX9-dependent R-loop arm of the vulnerability model.
  - reference: PMID:25779942
    reference_title: "SLFN11 Is a Transcriptional Target of EWS-FLI1 and a Determinant of Drug Response in Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "EWS-FLI1 binds near the transcription start site of SLFN11 promoter"
    explanation: Supports direct EWS-FLI1 activation of SLFN11 within this vulnerability model.
- hypothesis_group_id: cohesin_modified_high_risk_model
  hypothesis_label: STAG2/cohesin-modified high-risk enhancer model
  status: EMERGING
  description: >-
    STAG2 loss modifies the canonical EWS-FLI1 pathograph by altering cohesin
    architecture, enhancer-promoter contacts, PRC2/CTCF-regulated chromatin
    states, and possibly replication-fork repair stress. The leading model is
    selective amplification of multimeric GGAA enhancer output in a high-risk
    subset. This model is qualified by unresolved
    enhancer-versus-PRC2-versus-DDR mechanisms and by population-specific
    clinical effects: the COG Western-cohort STAG2 protein-loss prognostic
    association has not replicated uniformly, including a Japanese comprehensive
    genomic profiling cohort in which STAG2 mutation frequency was lower and
    CDKN2A/B deletions were prognostic instead.
  evidence:
  - reference: PMID:41950086
    reference_title: "STAG2 loss amplifies EWS-FLI1-driven microsatellite enhancer activity promoting Ewing sarcoma aggressiveness."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "oncogenic transcriptional state in Ewing sarcoma."
    explanation: Supports the STAG2-modified high-risk enhancer model.
  - reference: PMID:39487368
    reference_title: "STAG2 loss in Ewing sarcoma alters enhancer-promoter contacts dependent and independent of EWS::FLI1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "cohesin-STAG2 facilitates communication between"
    explanation: Supports STAG2-dependent enhancer-promoter communication at long GGAA repeats.
  - reference: PMID:36221002
    reference_title: "Adverse prognostic impact of the loss of STAG2 protein expression in patients with newly diagnosed localised Ewing sarcoma: A report from the Children's Oncology Group."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "5-year event-free survival was 54% (95% CI 34-70%) and"
    explanation: Supports the high-risk clinical association for STAG2 protein loss.
  - reference: PMID:41206913
    reference_title: "Analysis of comprehensive genomic profiling test for Ewing sarcoma in pediatric patients and adults using the nationwide clinical and genomic database in Japan."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "enrollment for STAG2 and TP53 mutations (P = .663 and P = .767), but those with"
    explanation: >-
      Qualifies the clinical universality of the STAG2 high-risk model: this
      Japanese cohort did not find a significant survival association for STAG2
      mutation after genomic profiling enrollment, supporting a
      population-qualified rather than universal prognostic claim.
histopathology:
- name: Small Round Cell Tumor
  finding_term:
    preferred_term: Ewing Sarcoma
    term:
      id: NCIT:C4817
      label: Ewing Sarcoma
  frequency: VERY_FREQUENT
  description: Ewing sarcoma is a small round cell tumor of bone or soft tissue.
  notes: >-
    Local NCIT places Ewing Sarcoma under both morphologic finding and neoplasm
    by special category hierarchies, and its definition explicitly captures the
    small round cell morphology.
  evidence:
  - reference: PMID:35117540
    reference_title: "Effects of different treatments and other factors on the prognosis of patients with ewing sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ewing sarcoma is a small round cell tumor of bone or soft tissue"
    explanation: Abstract defines Ewing sarcoma as a small round cell tumor of bone or soft tissue.
- name: Homer Wright Rosette-like Formation
  finding_term:
    preferred_term: Homer Wright Rosette Formation
    term:
      id: NCIT:C35942
      label: Homer Wright Rosette Formation
  frequency: OCCASIONAL
  description: >-
    Atypical Ewing sarcoma of bone can show rosette-like textures resembling
    Homer-Wright rosettes, reflecting neuroectodermal differentiation features
    in a minority of cases rather than a required diagnostic feature.
  evidence:
  - reference: PMID:3113717
    reference_title: "Small round blue cell sarcoma of bone mimicking atypical Ewing's sarcoma with neuroectodermal features. An analysis of five cases with immunohistochemical and electron microscopic support."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Ewing's sarcoma (ES) of bone may occasionally display rosette-like textures mimicking Homer-Wright ones"
    explanation: >-
      Supports Homer Wright rosette-like formation as an occasional
      histopathologic pattern in atypical Ewing sarcoma of bone.
- name: High Grade Tumor
  finding_term:
    preferred_term: high grade
    term:
      id: NCIT:C14158
      label: High Grade
  frequency: VERY_FREQUENT
  description: >-
    Ewing sarcoma is classified as high grade by definition. Tumors are
    aggressive and highly malignant, and high-grade morphology is a universal
    feature used in staging and treatment stratification.
  evidence:
  - reference: PMID:35117540
    reference_title: "Effects of different treatments and other factors on the prognosis of patients with ewing sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "originating from the neuroectoderm. Aggressive and highly malignant are the main"
    explanation: >-
      Supports high-grade classification as a defining histopathological
      feature of Ewing sarcoma: the abstract describes it as aggressive and
      highly malignant, consistent with universal high-grade tumor designation.
- name: Geographic Tumor Necrosis
  finding_term:
    preferred_term: tumor cell necrosis
    term:
      id: NCIT:C35957
      label: Tumor Cell Necrosis
  frequency: FREQUENT
  description: >-
    Tumor cell necrosis can be assessed in Ewing sarcoma resection specimens,
    especially after neoadjuvant chemotherapy. The degree of tumor necrosis is a
    clinically meaningful histologic response marker: greater than or equal to
    90% tumor necrosis defines a good chemotherapy response in many studies and
    is associated with improved local recurrence-free survival.
  evidence:
  - reference: PMID:17177205
    reference_title: "Chemotherapy response is an important predictor of local recurrence in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "90% tumor necrosis), had superior LRFS at 5 years (86% vs 51%, P = .015)."
    explanation: >-
      Supports post-chemotherapy tumor necrosis as an Ewing sarcoma
      histologic-response measure with prognostic significance.

phenotypes:
- category: Musculoskeletal
  name: Bone Pain
  frequency: FREQUENT
  diagnostic: true
  description: >-
    Localized bone pain is a common presenting symptom and may be present for
    weeks to months before diagnosis. Pain may be intermittent initially and
    worsen progressively.
  phenotype_term:
    preferred_term: Bone pain
    term:
      id: HP:0002653
      label: Bone pain
  evidence:
  - reference: PMID:34235109
    reference_title: "Clinical Profile and Outcome of Adult Ewing Sarcoma: A Retrospective Analysis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Pain (75.3%) was the most common symptom at presentation."
    explanation: >-
      Provides Ewing sarcoma-specific cohort evidence that pain is the most
      common presenting symptom and supports the FREQUENT frequency assignment.
- category: Musculoskeletal
  name: Soft Tissue Mass / Localized Swelling
  frequency: VERY_FREQUENT
  diagnostic: true
  description: >-
    A palpable mass or localized swelling may develop as tumor extends through
    the bone cortex into surrounding soft tissues. The mass is often firm and
    may be tender or warm, and may initially be attributed to trauma or infection.
  phenotype_term:
    preferred_term: Soft tissue neoplasm
    term:
      id: HP:0031459
      label: Soft tissue neoplasm
- category: Constitutional
  name: Fever
  frequency: OCCASIONAL
  description: >-
    Systemic symptoms including fever may occur, sometimes leading to initial
    misdiagnosis as osteomyelitis.
  phenotype_term:
    preferred_term: Fever
    term:
      id: HP:0001945
      label: Fever
- category: Constitutional
  name: Weight Loss
  frequency: OCCASIONAL
  description: >-
    Unintentional weight loss may occur with advanced or metastatic disease.
  phenotype_term:
    preferred_term: Weight loss
    term:
      id: HP:0001824
      label: Weight loss
- category: Systemic
  name: Metastatic Disease
  frequency: FREQUENT
  description: >-
    Approximately 25% of patients have metastases at diagnosis, most commonly
    to lungs, bone, and bone marrow. Metastatic disease significantly worsens
    prognosis with five-year survival dropping to 20-30%.
  phenotype_term:
    preferred_term: Neoplasm
    term:
      id: HP:0002664
      label: Neoplasm
  evidence:
  - reference: PMID:30215968
    reference_title: "Bone Cancer: Diagnosis and Treatment Principles."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "lowers the five-year survival rate to 20% to 30%."
    explanation: Confirms that metastatic disease lowers five-year survival to 20-30%.
  - reference: PMID:17301523
    reference_title: "[Ewing sarcoma]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "an approximately 10-30% 5-year event-free survival rate."
    explanation: Confirms the poor prognosis for metastatic Ewing sarcoma with quantitative survival data.
  - reference: PMID:36669140
    reference_title: "Randomized Phase III Trial of Ganitumab With Interval-Compressed Chemotherapy for Patients With Newly Diagnosed Metastatic Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The 3-year EFS estimates were 37.4%"
    explanation: Provides precise 3-year EFS data from the COG AEWS1221 phase III trial for metastatic Ewing sarcoma.
- category: Musculoskeletal
  name: Pathologic Fracture
  frequency: OCCASIONAL
  description: >-
    Pathologic fracture through weakened bone may be the presenting event in
    some patients. Bone destruction by tumor reduces structural integrity.
  phenotype_term:
    preferred_term: Pathologic fracture
    term:
      id: HP:0002756
      label: Pathologic fracture
- category: Hematologic
  name: Anemia
  frequency: OCCASIONAL
  description: >-
    Anemia may be present, particularly in patients with advanced or metastatic
    disease. It can result from bone marrow involvement or chronic disease.
  phenotype_term:
    preferred_term: Anemia
    term:
      id: HP:0001903
      label: Anemia
biochemical:
- name: EWS-FLI1 Fusion Detection
  notes: >-
    RT-PCR or FISH detection of EWS-FLI1 fusion (or variant EWS-ERG, EWS-ETV1)
    is diagnostic. Approximately 85% have EWS-FLI1, and most others have
    alternative ETS family fusions.
  evidence:
  - reference: PMID:17301523
    reference_title: "[Ewing sarcoma]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "EWS-FLI 1 among Ewing sarcoma"
    explanation: Supports molecular detection of EWS-FLI1 fusion as a defining diagnostic feature.
genetic:
- name: EWS-FLI1 Fusion
  association: Somatic Fusion Oncogene
  notes: >-
    The t(11;22)(q24;q12) translocation creates the EWS-FLI1 fusion in 85%
    of cases. EWS-ERG t(21;22) accounts for most remaining cases. All Ewing
    sarcomas harbor EWS-ETS family fusions, which are both diagnostic and
    represent the primary oncogenic driver.
  evidence:
  - reference: PMID:17250957
    reference_title: "The Biology of Ewing sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "It is associated in 85% of cases with the"
    explanation: Directly confirms the 85% frequency of the t(11;22) translocation creating EWS-FLI1.
- name: STAG2
  association: Somatic Tumor Suppressor Mutation
  variant_origin: SOMATIC
  frequency: 17%
  gene_term:
    preferred_term: STAG2
    term:
      id: hgnc:11355
      label: STAG2
  notes: >-
    STAG2 loss-of-function mutation or protein loss defines a clinically
    important high-risk Ewing sarcoma subset. STAG2 alteration co-occurs with
    TP53 mutation in some tumors and is mutually exclusive with CDKN2A deletion,
    indicating distinct secondary genetic routes layered on the EWS-ETS fusion.
  evidence:
  - reference: PMID:25223734
    reference_title: "Genomic landscape of Ewing sarcoma defines an aggressive subtype with co-association of STAG2 and TP53 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "detected in STAG2 (17%), CDKN2A (12%), TP53 (7%)"
    explanation: Establishes STAG2 as one of the most common recurrent somatic alterations in Ewing sarcoma.
  - reference: PMID:36221002
    reference_title: "Adverse prognostic impact of the loss of STAG2 protein expression in patients with newly diagnosed localised Ewing sarcoma: A report from the Children's Oncology Group."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "5-year event-free survival was 54% (95% CI 34-70%) and"
    explanation: Supports the adverse clinical association of STAG2 protein loss in localized Ewing sarcoma.
- name: TP53
  association: Somatic Tumor Suppressor Mutation
  variant_origin: SOMATIC
  frequency: 7%
  gene_term:
    preferred_term: TP53
    term:
      id: hgnc:11998
      label: TP53
  notes: >-
    TP53 is recurrently mutated in a minority of Ewing sarcomas and co-occurs
    with STAG2 mutation in an aggressive secondary-genetic subset.
  evidence:
  - reference: PMID:25223734
    reference_title: "Genomic landscape of Ewing sarcoma defines an aggressive subtype with co-association of STAG2 and TP53 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "STAG2 and TP53 mutations are often"
    explanation: Supports TP53 mutation as part of the high-risk STAG2/TP53 co-altered Ewing sarcoma subset.
- name: CDKN2A
  association: Somatic Tumor Suppressor Deletion
  variant_origin: SOMATIC
  frequency: 12%
  gene_term:
    preferred_term: CDKN2A
    term:
      id: hgnc:1787
      label: CDKN2A
  notes: >-
    CDKN2A deletion is a recurrent secondary alteration in Ewing sarcoma and
    appears largely mutually exclusive with STAG2 mutation, suggesting a
    distinct cell-cycle checkpoint route to progression.
  evidence:
  - reference: PMID:25223734
    reference_title: "Genomic landscape of Ewing sarcoma defines an aggressive subtype with co-association of STAG2 and TP53 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "STAG2 mutations and CDKN2A deletions were mutually exclusive"
    explanation: Supports CDKN2A deletion as a recurrent secondary alteration distinct from STAG2-mutant Ewing sarcoma.
treatments:
- name: Neoadjuvant Chemotherapy
  description: >-
    Intensive multi-agent chemotherapy (vincristine, doxorubicin, cyclophosphamide
    alternating with ifosfamide/etoposide - VDC/IE) is standard. Neoadjuvant
    chemotherapy shrinks tumors before local control.
  treatment_term:
    preferred_term: Neoadjuvant Chemotherapy
    term:
      id: NCIT:C213450
      label: Neoadjuvant Chemotherapy
    therapeutic_agent:
    - preferred_term: vincristine
      term:
        id: CHEBI:28445
        label: vincristine
    - preferred_term: doxorubicin
      term:
        id: CHEBI:28748
        label: doxorubicin
    - preferred_term: cyclophosphamide
      term:
        id: CHEBI:4027
        label: cyclophosphamide
    - preferred_term: ifosfamide
      term:
        id: CHEBI:5864
        label: ifosfamide
    - preferred_term: etoposide
      term:
        id: CHEBI:4911
        label: etoposide
  evidence:
  - reference: PMID:20152770
    reference_title: "Ewing's sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cooperative group studies have led to chemotherapy regimens"
    explanation: Confirms the five-drug chemotherapy backbone used in Ewing sarcoma treatment.
  - reference: PMID:17301523
    reference_title: "[Ewing sarcoma]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "standard chemotherapy for localized ESFT"
    explanation: Confirms VDC/IE as the standard North American chemotherapy regimen for Ewing sarcoma.
  - reference: PMID:36669140
    reference_title: "Randomized Phase III Trial of Ganitumab With Interval-Compressed Chemotherapy for Patients With Newly Diagnosed Metastatic Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "interval-compressed vincristine/doxorubicin/cyclophosphamide alternating once"
    explanation: Confirms VDC/IE as standard chemotherapy backbone in the COG phase III trial for metastatic Ewing sarcoma.
- name: Surgical Resection
  description: >-
    Wide surgical resection with negative margins is preferred when feasible
    without excessive morbidity. Reconstruction may be needed for limb salvage.
  treatment_term:
    preferred_term: Definitive Surgical Resection
    term:
      id: NCIT:C154430
      label: Definitive Surgical Resection
  evidence:
  - reference: PMID:35117540
    reference_title: "Effects of different treatments and other factors on the prognosis of patients with ewing sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "CT combined surgery achieved"
    explanation: Supports that chemotherapy combined with surgery achieves the best survival outcomes.
- name: Radiation Therapy
  description: >-
    Definitive radiation is used for unresectable tumors or when surgery would
    cause significant morbidity. Also used post-operatively for close or
    positive margins.
  treatment_term:
    preferred_term: Radiation Therapy
    term:
      id: NCIT:C15313
      label: Radiation Therapy
  evidence:
  - reference: PMID:33818887
    reference_title: "Ewing sarcoma."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "surgery, definitive radiation, or a combination of surgery and radiation"
    explanation: Confirms the role of definitive radiation as a local treatment option in Ewing sarcoma management.
- name: Adjuvant Chemotherapy
  description: >-
    Additional chemotherapy after local control to eliminate micrometastatic
    disease. Total treatment duration is typically 9-12 months.
  treatment_term:
    preferred_term: chemotherapy
    term:
      id: MAXO:0000647
      label: chemotherapy
- name: PARP Inhibitor Combination Therapy
  description: >-
    Investigational PARP-targeted treatment strategies for recurrent or
    refractory Ewing sarcoma aim to exploit fusion-linked replication stress
    and homologous-recombination defects. Clinical talazoparib plus
    temozolomide was feasible but showed no objective Ewing responses in a
    small phase 2 cohort, while dual PARP-HDAC inhibition has preclinical
    activity in Ewing sarcoma cells and spheroids.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: talazoparib
      term:
        id: CHEBI:231344
        label: talazoparib
    - preferred_term: temozolomide
      term:
        id: CHEBI:72564
        label: temozolomide
  target_mechanisms:
  - target: Replication Stress and Impaired Homologous Recombination
    treatment_effect: MODULATES
    description: >-
      PARP inhibition targets the DNA-repair and replication-stress axis
      modeled in Ewing sarcoma, with combination strategies intended to deepen
      synthetic-lethal pressure on tumor cells.
    evidence:
    - reference: PMID:37279093
      reference_title: "Development of a Novel Bifunctional PARP-HDAC Inhibitor with Activity in Ewing Sarcoma."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "bifunctional PARPi (kt-3283) with dual activity toward PARP1/2 and HDAC enzymes in Ewing sarcoma cells."
      explanation: >-
        Supports direct targeting of PARP-dependent DNA-repair biology in Ewing
        sarcoma cells, coupled to chromatin modulation through HDAC inhibition.
  - target: NuRD/CHD4 Repressive Chromatin Program
    treatment_effect: MODULATES
    description: >-
      Dual PARP-HDAC inhibition links the replication-stress vulnerability to
      chromatin-state modulation represented by the NuRD/CHD4/LSD1 repressive
      pathograph arm.
    evidence:
    - reference: PMID:37279093
      reference_title: "Development of a Novel Bifunctional PARP-HDAC Inhibitor with Activity in Ewing Sarcoma."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "kt-3283 displayed enhanced cytotoxicity in Ewing sarcoma models."
      explanation: >-
        Supports a chromatin-linked PARP-HDAC treatment concept in Ewing
        sarcoma models.
  evidence:
  - reference: PMID:31724813
    reference_title: "Phase 1/2 trial of talazoparib in combination with temozolomide in children and adolescents with refractory/recurrent solid tumors including Ewing sarcoma: A Children's Oncology Group Phase 1 Consortium study (ADVL1411)."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "0 of 10 EWS subjects experienced an objective response; two experienced prolonged SD."
    explanation: >-
      Clinical evidence supports feasibility but only partial therapeutic
      support because objective responses were not observed in the phase 2
      Ewing cohort.
  - reference: PMID:37279093
    reference_title: "Development of a Novel Bifunctional PARP-HDAC Inhibitor with Activity in Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "In three-dimensional spheroid models of Ewing sarcoma, kt-3283 showed efficacy"
    explanation: Supports preclinical activity of dual PARP-HDAC inhibition in 3D Ewing sarcoma spheroid models.
- name: LSD1 Inhibitor Therapy
  description: >-
    LSD1/KDM1A inhibition with seclidemstat (SP-2577) is an investigational
    strategy for fusion-positive sarcomas that attempts to reverse or modulate
    FET-fusion transcriptional programs. In Ewing sarcoma, the rationale links
    directly to the EWS-FLI1-associated NuRD/CHD4/LSD1 repressive chromatin arm.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: seclidemstat
      term:
        id: NCIT:C154328
        label: Seclidemstat
  target_mechanisms:
  - target: NuRD/CHD4 Repressive Chromatin Program
    treatment_effect: MODULATES
    description: >-
      Seclidemstat is intended to modulate LSD1-linked transcriptional and
      chromatin programs downstream of EWS-FLI1 and related FET fusion proteins.
    evidence:
    - reference: PMID:40852926
      reference_title: "Seclidemstat (SP-2577) Induces Transcriptomic Reprogramming and Cytotoxicity in Multiple Fusion-Positive Sarcomas."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "Seclidemstat recapitulated much of SP-2509 transcriptional activity in Ewing sarcoma."
      explanation: Supports seclidemstat modulation of the Ewing sarcoma transcriptional program linked to the LSD1 pathograph arm.
  evidence:
  - reference: PMID:40852926
    reference_title: "Seclidemstat (SP-2577) Induces Transcriptomic Reprogramming and Cytotoxicity in Multiple Fusion-Positive Sarcomas."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "seclidemstat (SP-2577), is currently in clinical trials for FET-rearranged sarcomas (NCT03600649)"
    explanation: Supports seclidemstat as an emerging clinical-stage therapy for FET-rearranged sarcomas including Ewing sarcoma.
  - reference: PMID:34453478
    reference_title: "In vivo evaluation of the lysine-specific demethylase (KDM1A/LSD1) inhibitor SP-2577 (Seclidemstat) against pediatric sarcoma preclinical models: A report from the Pediatric Preclinical Testing Consortium (PPTC)."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "inhibited growth of three of eight Ewing sarcoma (EwS)"
    explanation: >-
      Supports in vivo preclinical activity in a subset of Ewing xenografts, but
      only partial support because the same abstract reports limited activity
      overall.
- name: USP1 Inhibitor Therapy
  description: >-
    USP1 inhibition is a preclinical targeted strategy aimed at the EWS-FLI1
    induced USP1-survivin survival buffer that helps Ewing sarcoma cells tolerate
    endogenous replication stress and standard chemotherapy exposure.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: USP1 inhibitor
      description: >-
        Local NCIT/CHEBI search did not identify a USP1-specific inhibitor
        class; this uses the broader NCIT enzyme inhibitor class while
        preserving USP1 specificity in preferred_term.
      term:
        id: NCIT:C471
        label: Enzyme Inhibitor
  target_mechanisms:
  - target: Replication Stress and Impaired Homologous Recombination
    treatment_effect: INHIBITS
    description: >-
      USP1 inhibition blocks a survival adaptation within the replication-stress
      node by destabilizing the USP1-survivin axis and sensitizing cells to DNA
      damaging chemotherapy.
    evidence:
    - reference: PMID:37478161
      reference_title: "USP1 Expression Driven by EWS::FLI1 Transcription Factor Stabilizes Survivin and Mitigates Replication Stress in Ewing Sarcoma."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "USP1 inhibition sensitizes cells to doxorubicin and etoposide treatment."
      explanation: >-
        Supports targeting the USP1-dependent replication-stress survival
        buffer in Ewing sarcoma cells.
  evidence:
  - reference: PMID:37478161
    reference_title: "USP1 Expression Driven by EWS::FLI1 Transcription Factor Stabilizes Survivin and Mitigates Replication Stress in Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "USP1 knockdown or inhibition arrests EWS cell growth and induces cell death by apoptosis."
    explanation: Supports USP1 inhibition as a preclinical targeted treatment concept in Ewing sarcoma.
experimental_models:
- name: Ewing sarcoma tumor organoid model systems
  description: >-
    Tumor organoids are part of the current Ewing sarcoma preclinical model
    landscape and provide a non-animal 3D system for therapy evaluation and
    mechanism-focused modeling alongside cell lines and xenografts.
  experimental_model_type: ORGANOID
  namo_type: namo:Organoid
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  conditions:
  - Ewing sarcoma
  - tumor organoid preclinical modeling
  cell_source: Ewing sarcoma tumor-derived cells
  culture_system: Three-dimensional tumor organoid culture
  publication: PMID:40911901
  modeled_mechanisms:
  - target: EWS-FLI1 Fusion Oncogene
    description: Models fusion-positive tumor biology in a 3D non-animal context.
  - target: Tumor Cell Proliferation and Survival
    description: Enables preclinical testing of tumor growth and survival responses.
  evidence:
  - reference: PMID:40911901
    reference_title: "Advancing Preclinical Biology for Ewing Sarcoma: An International Effort."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "vitro (cell lines and tumor organoids) and in vivo (mouse and nonmammalian xenografts) model systems."
    explanation: Supports tumor organoids as part of the Ewing sarcoma preclinical modeling landscape.
- name: Patient-derived Ewing sarcoma culture panel
  description: >-
    Patient-derived Ewing sarcoma cultures provide a primary-cell in vitro
    non-animal model for studying EWSR1 fusion status, proliferation, migration,
    and treatment response in models that differ transcriptionally from
    long-established cell lines.
  experimental_model_type: PRIMARY_CELL_CULTURE
  namo_type: namo:TwoDCellCulture
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  conditions:
  - Ewing sarcoma
  - patient-derived ES cultures
  - preclinical drug response testing
  cell_source: Patient-derived Ewing sarcoma tumor cultures
  culture_system: Patient-derived in vitro culture
  publication: PMID:41681984
  modeled_mechanisms:
  - target: EWS-FLI1 Fusion Oncogene
    description: Models EWSR1 fusion-positive tumor state in patient-derived cultures.
  - target: Tumor Cell Proliferation and Survival
    description: Assays patient-derived proliferation and therapy-response phenotypes.
  findings:
  - statement: Patient-derived Ewing cultures retain EWSR1 fusion DNA and clinically relevant treatment-response features.
    evidence:
    - reference: PMID:41681984
      reference_title: "Characterisation of Bespoke Patient-Derived In Vitro Models of Ewing Sarcoma."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "All PDES contain EWSR1 fusion DNA"
      explanation: Supports PDES as patient-derived, fusion-positive Ewing sarcoma models.
  evidence:
  - reference: PMID:41681984
    reference_title: "Characterisation of Bespoke Patient-Derived In Vitro Models of Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "we have established and characterised patient-derived ES cultures (PDES) in vitro."
    explanation: Supports this as a patient-derived in vitro Ewing sarcoma model system.
- name: Flow-perfusion Ewing sarcoma 3D scaffold coculture
  description: >-
    Flow-perfusion 3D scaffold cocultures combine Ewing sarcoma cells with
    mesenchymal stromal cells under biomechanical stimulation, enabling
    controlled testing of tumor-stroma signaling, IGF-1R/STAT3 biology, and
    drug-resistance mechanisms that are absent from standard monolayer systems.
  experimental_model_type: CO_CULTURE
  namo_type: namo:OrganOnChip
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_types:
  - preferred_term: mesenchymal stem cell
    term:
      id: CL:0000134
      label: mesenchymal stem cell
  conditions:
  - Ewing sarcoma
  - tumor-stroma coculture
  - flow perfusion
  cell_source: Ewing sarcoma cells cocultured with mesenchymal stem cells
  culture_system: 3D scaffold coculture in a flow perfusion bioreactor
  publication: PMID:27923328
  modeled_mechanisms:
  - target: IGF-1/YAP1 Developmental Cooperation
    description: Assays IGF-1/IGF-1R signaling under controlled tumor-stroma and shear-stress conditions.
  - target: Tumor Cell Proliferation and Survival
    description: Models stromal support of growth and drug-resistance phenotypes.
  evidence:
  - reference: PMID:27923328
    reference_title: "Modeling Stroma-Induced Drug Resistance in a Tissue-Engineered Tumor Model of Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "ES cells and mesenchymal stem cells (MSCs) in 3D scaffolds within a flow perfusion bioreactor"
    explanation: Supports this as a 3D tumor-stroma coculture model for Ewing sarcoma.
  - reference: PMID:26240353
    reference_title: "Flow perfusion effects on three-dimensional culture and drug sensitivity of Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "poly(ε-caprolactone) 3D scaffolds within a flow perfusion bioreactor."
    explanation: Supports the flow-perfusion scaffold format for Ewing sarcoma drug-sensitivity modeling.
- name: Human embryonic mesenchymal stem cell EWS-FLI1 transformation model
  description: >-
    Human embryonic mesenchymal stem cells (heMSCs) transduced with EWS::FLI1
    acquire an Ewing sarcoma transcriptome and form tumors in xenograft models,
    providing a human-cell-based non-established-cell-line new approach
    methodology for studying
    cell-of-origin context, DNA damage repair defects, and fusion-gene
    transformation. This model differs from adult MSC and neural-crest-based
    models in that only undifferentiated early heMSCs fully support EWS-FLI1
    oncogenic transformation.
  experimental_model_type: PRIMARY_CELL_CULTURE
  namo_type: namo:TwoDCellCulture
  organism:
    preferred_term: human
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_types:
  - preferred_term: mesenchymal stem cell
    term:
      id: CL:0000134
      label: mesenchymal stem cell
  conditions:
  - Ewing sarcoma
  - EWS-FLI1 transformation
  - embryonic developmental context
  cell_source: Human embryonic mesenchymal stem cells (heMSCs) transduced with EWS::FLI1 lentivirus
  culture_system: Primary embryonic MSC culture with lentiviral oncogene transduction and xenograft validation
  publication: PMID:41136396
  modeled_mechanisms:
  - target: EWS-FLI1 Fusion Oncogene
    description: >-
      Models EWS-FLI1 oncogene expression in an embryonic human mesenchymal
      developmental context, with xenograft tumor formation demonstrating
      transformation capacity.
  - target: Permissive Progenitor Cell State
    description: >-
      Demonstrates that only undifferentiated, early heMSCs (not adult MSCs or
      pediatric MSCs) fully support EWS-FLI1 transformation, linking progenitor
      developmental state to oncogenic permissiveness.
  - target: Replication Stress and Impaired Homologous Recombination
    description: >-
      EWS-FLI1-expressing heMSCs show defective BRCA1-mediated DNA repair,
      modeling the replication stress and HRR deficiency arm of the pathograph.
  findings:
  - statement: >-
      EWS::FLI1 expression in undifferentiated human embryonic MSCs enforces an
      Ewing sarcoma transcriptome and enables tumor formation in xenografts, with
      evidence of defective DNA damage repair.
    evidence:
    - reference: PMID:41136396
      reference_title: "EWS::FLI1 expression in human embryonic mesenchymal stem cells leads to transcriptional reprograming, defective DNA damage repair and Ewing sarcoma."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: "heMSCs results in the formation of tumors expressing characteristic ES markers."
      explanation: >-
        Supports this model: EWS-FLI1-transduced heMSCs form Ewing sarcoma-like
        tumors in xenograft hosts, validating transformation capacity in the
        embryonic MSC developmental context.
  evidence:
  - reference: PMID:41136396
    reference_title: "EWS::FLI1 expression in human embryonic mesenchymal stem cells leads to transcriptional reprograming, defective DNA damage repair and Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "is able to endow transforming capacity when expressed in undifferentiated, early"
    explanation: >-
      Supports using early embryonic MSCs as a primary-cell new approach
      methodology for studying EWS-FLI1 transformation: only undifferentiated
      heMSCs — not adult MSCs or pediatric MSCs — fully support oncogene-driven
      transformation.
discussions:
- discussion_id: gap_ewing_cell_of_origin_context
  prompt: >-
    Which human progenitor state is truly permissive for EWS-FLI1 transformation,
    and what chromatin or differentiation-state features distinguish transforming
    early mesenchymal or neural crest-like cells from non-transforming MSC states?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Permissive Progenitor Cell State
  - pathophysiology#IGF-1/YAP1 Developmental Cooperation
  - pathophysiology#GGAA Microsatellite Germline Susceptibility Architecture
  - pathophysiology#EWS-FLI1 Fusion Oncogene
  - pathophysiology#GGAA Microsatellite Enhancer Reprogramming
  rationale: >-
    Neural crest-derived cells, bone marrow-derived MSCs, pediatric MSCs, adult
    MSCs, and 2025 embryonic MSC models support overlapping but not identical
    origin hypotheses. The unresolved mechanism is not simply whether EWS-FLI1
    can alter transcription, but which developmental chromatin state lets GGAA
    enhancer rewiring become transforming rather than toxic, senescent, or
    differentiation-inducing. IGF-1/YAP1 signaling and germline GGAA repeat
    architecture now provide concrete cooperating mechanisms, but neither yet
    defines the full permissive human progenitor state.
  proposed_experiments:
  - experiment_id: exp_ewing_isogenic_developmental_context_panel
    name: Isogenic developmental-context EWS-FLI1 induction panel
    description: >-
      Build an inducible or safe-harbor knock-in EWS-FLI1 panel across
      hPSC-derived migratory neural crest cells, early mesenchymal progenitors,
      osteochondral progenitors, pediatric MSCs, and adult MSCs. Measure the same
      fusion dose and timing across lineages, then compare enhancer activation,
      differentiation blockade, DNA-damage state, senescence, and xenograft or
      organoid tumorigenicity.
    experiment_type:
      preferred_term: isogenic stem-cell transformation assay
    model_systems:
    - name: hPSC-derived neural crest and early mesenchymal progenitor panel
      description: >-
        Genome-engineered human pluripotent stem cell derivatives with matched
        EWS-FLI1 induction across candidate Ewing sarcoma cells of origin.
      experimental_model_type: IPSC_DERIVED_MODEL
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      cell_types:
      - preferred_term: migratory neural crest cell
        term:
          id: CL:0000333
          label: migratory neural crest cell
      - preferred_term: early mesenchymal stem cell
        term:
          id: CL:0000134
          label: mesenchymal stem cell
      publication: PMID:41136396
      modeled_mechanisms:
      - target: Permissive Progenitor Cell State
        description: Tests whether early developmental context permits EWS-FLI1 transformation.
      - target: GGAA Microsatellite Enhancer Reprogramming
        description: Measures whether the same fusion activates different GGAA enhancer programs by cell state.
    perturbations:
    - name: Inducible EWS-FLI1 expression
      target: pathophysiology#EWS-FLI1 Fusion Oncogene
      description: >
        Express matched EWS-FLI1 at controlled dose and timing across candidate
        progenitor states.
      genes:
      - preferred_term: EWSR1
        term:
          id: hgnc:3508
          label: EWSR1
      - preferred_term: FLI1
        term:
          id: hgnc:3749
          label: FLI1
    - name: Pubertal IGF-1/YAP1 modulation
      target: pathophysiology#IGF-1/YAP1 Developmental Cooperation
      description: >
        Add pubertal-range IGF-1 exposure and YAP1/TEAD inhibition or knockout
        arms to determine whether the cooperating signal is conserved in human
        progenitors.
      genes:
      - preferred_term: IGF1
        term:
          id: hgnc:5464
          label: IGF1
      - preferred_term: YAP1
        term:
          id: hgnc:16262
          label: YAP1
    readouts:
    - name: GGAA enhancer activation by developmental state
      target: pathophysiology#GGAA Microsatellite Enhancer Reprogramming
      description: >
        Compare EWS-FLI1 occupancy, chromatin accessibility, and H3K27ac gain at
        endogenous GGAA microsatellites.
      biological_processes:
      - preferred_term: chromatin remodeling
        term:
          id: GO:0006338
          label: chromatin remodeling
      assays:
      - preferred_term: single-cell ATAC-seq
      - preferred_term: CUT&Tag
      - preferred_term: single-cell RNA-seq
      direction: POSITIVE
    - name: Transformation and differentiation blockade
      target: pathophysiology#Blocked Differentiation
      description: >
        Measure loss of mesenchymal/osteochondral differentiation capacity,
        acquisition of Ewing-like transcription, senescence avoidance, and
        tumor formation in permissive contexts.
      biological_processes:
      - preferred_term: mesenchymal cell differentiation
        term:
          id: GO:0048762
          label: mesenchymal cell differentiation
      assays:
      - preferred_term: differentiation assay
      - preferred_term: xenograft tumorigenicity assay
      direction: NEGATIVE
    controls:
    - name: Isogenic uninduced progenitor controls
      description: Same genetic background and differentiation state without EWS-FLI1 induction.
    - name: Nonpermissive adult MSC comparator
      description: Mature MSC context expected to show incomplete transformation or toxicity.
    - name: Fusion knockdown or degron rescue
      description: Acute EWS-FLI1 withdrawal after Ewing-like state acquisition.
    decision_criterion: >-
      The cell-of-origin model is prioritized when a specific progenitor state
      reproducibly shows EWS-FLI1-dependent GGAA enhancer activation, Ewing-like
      core regulatory circuitry, differentiation blockade, and tumorigenicity
      while closely related states fail one or more of those criteria.
    would_support:
    - pathophysiology#Permissive Progenitor Cell State
    - pathophysiology#IGF-1/YAP1 Developmental Cooperation
    - pathophysiology#GGAA Microsatellite Enhancer Reprogramming
    - pathophysiology#Blocked Differentiation
    would_refute:
    - pathophysiology#Permissive Progenitor Cell State
    evidence:
    - reference: PMID:41136396
      reference_title: "EWS::FLI1 expression in human embryonic mesenchymal stem cells leads to transcriptional reprograming, defective DNA damage repair and Ewing sarcoma."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "mesenchymal stem cells (heMSCs) results in the acquisition of an ES"
      explanation: Supports the feasibility and rationale for testing early human mesenchymal contexts.
    - reference: PMID:21559395
      reference_title: "Modeling initiation of Ewing sarcoma in human neural crest cells."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "similar to hNCSC than any other normal tissue, including MSC, indicating that"
      explanation: Supports including neural crest-derived progenitors in the comparative panel.
  evidence:
  - reference: PMID:41136396
    reference_title: "EWS::FLI1 expression in human embryonic mesenchymal stem cells leads to transcriptional reprograming, defective DNA damage repair and Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "whose cellular origin remains unclear."
    explanation: Directly states the knowledge gap.
  - reference: PMID:40080499
    reference_title: "YAP1 is a key regulator of EWS::FLI1-dependent malignant transformation upon IGF-1-mediated reprogramming of bone mesenchymal stem cells."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "concentrations mimicking serum levels during puberty"
    explanation: Supports adding IGF-1/YAP1 as a concrete cooperating mechanism that still needs human validation.
  - reference: PMID:36787739
    reference_title: "Targeted long-read sequencing of the Ewing sarcoma 6p25.1 susceptibility locus identifies germline-somatic interactions with EWSR1-FLI1 binding."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "had longer alleles (>135"
    explanation: Supports inherited GGAA architecture as part of the permissive-context gap.
- discussion_id: gap_ewing_ggaa_enhancer_grammar
  prompt: >-
    What GGAA microsatellite grammar and cofactor context make EWS-FLI1 binding
    oncogenic, and why do ETV6, BAF, and STAG2/cohesin perturbations produce
    different enhancer and differentiation outcomes?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#EWS-FLI1 Hub and Dosage Control
  - pathophysiology#BAF Complex Retargeting
  - pathophysiology#GGAA Microsatellite Enhancer Reprogramming
  - pathophysiology#ETV6 GGAA Counter-Regulation
  - pathophysiology#GGAA Microsatellite Germline Susceptibility Architecture
  - pathophysiology#STAG2-Modified Enhancer State
  rationale: >-
    EWS-FLI1 binds GGAA repeats, but binding alone does not explain why some
    microsatellites become oncogenic enhancers, why germline repeat length at
    EGR2 and RREB1 changes susceptibility, why ETV6 antagonism can redirect
    occupancy toward differentiation, or why STAG2 loss selectively amplifies
    multimeric GGAA enhancer programs. This gap is the enhancer-grammar layer of
    the pathograph, now spanning DNA sequence, hub dosage, native ETS
    competition, and cohesin state.
  proposed_experiments:
  - experiment_id: exp_ewing_endogenous_ggaa_saturation_editing
    name: Endogenous GGAA enhancer grammar saturation editing
    description: >-
      Use multiplex prime/base editing or CRISPR replacement to vary repeat
      length, repeat purity, flanking ETS motifs, and local chromatin context at
      endogenous EWS-FLI1-bound GGAA microsatellites. Combine these edits with
      acute BAF, ETV6, and STAG2 perturbations to quantify how enhancer grammar
      and cofactor state determine transcriptional output.
    experiment_type:
      preferred_term: pooled endogenous enhancer saturation editing experiment
    model_systems:
    - name: Ewing sarcoma cell-line and early progenitor enhancer-editing panel
      description: >-
        EWS-FLI1-positive Ewing sarcoma cell lines plus permissive progenitor
        models with editable endogenous GGAA microsatellite enhancers.
      experimental_model_type: CELL_LINE
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      publication: PMID:41950086
      modeled_mechanisms:
      - target: GGAA Microsatellite Enhancer Reprogramming
        description: Tests enhancer sequence grammar required for de novo enhancer function.
      - target: STAG2-Modified Enhancer State
        description: Tests how STAG2 loss changes enhancer grammar dependence.
    perturbations:
    - name: GGAA microsatellite sequence editing
      target: pathophysiology#GGAA Microsatellite Enhancer Reprogramming
      description: >
        Edit endogenous EWS-FLI1-bound GGAA repeats across short, intermediate,
        and long repeat classes, including susceptibility alleles at EGR2 and
        RREB1.
      genes:
      - preferred_term: EGR2
        term:
          id: hgnc:3239
          label: EGR2
      - preferred_term: RREB1
        term:
          id: hgnc:10449
          label: RREB1
    - name: ETV6, STAG2, and BAF cofactor perturbation
      target: pathophysiology#BAF Complex Retargeting
      description: >
        Combine enhancer edits with degron, CRISPRi, or knockout perturbations
        of ETV6, STAG2, and BAF complex activity.
      genes:
      - preferred_term: ETV6
        term:
          id: hgnc:3495
          label: ETV6
      - preferred_term: STAG2
        term:
          id: hgnc:11355
          label: STAG2
    readouts:
    - name: Enhancer occupancy and activity
      target: pathophysiology#GGAA Microsatellite Enhancer Reprogramming
      description: >
        Quantify EWS-FLI1 occupancy, BAF recruitment, chromatin accessibility,
        H3K27ac, enhancer-promoter contact, and target-gene transcription for
        each edited enhancer allele.
      biological_processes:
      - preferred_term: regulation of gene expression
        term:
          id: GO:0010468
          label: regulation of gene expression
      assays:
      - preferred_term: CUT&Tag
      - preferred_term: ATAC-seq
      - preferred_term: HiChIP
      - preferred_term: single-cell RNA-seq
      direction: POSITIVE
    - name: Differentiation versus proliferation outcome
      target: pathophysiology#Core Regulatory Circuitry Activation
      description: >
        Determine whether edited enhancer states reinforce Ewing core regulatory
        circuitry, drive mesenchymal differentiation, or reduce tumor cell growth.
      biological_processes:
      - preferred_term: cell population proliferation
        term:
          id: GO:0008283
          label: cell population proliferation
      assays:
      - preferred_term: pooled growth screen
      - preferred_term: differentiation marker profiling
      direction: POSITIVE
    controls:
    - name: Synonymous non-GGAA neutral edits
      description: Editing controls matched for guide delivery and repair outcome.
    - name: EWS-FLI1 degron withdrawal
      description: Fusion-dependence control for edited enhancer activity.
    decision_criterion: >-
      A causal enhancer-grammar rule is supported when endogenous repeat edits
      produce predictable EWS-FLI1 occupancy, BAF recruitment, enhancer-promoter
      contact, and transcriptional changes that reverse with fusion withdrawal
      and change coherently under ETV6 or STAG2 perturbation.
    would_support:
    - pathophysiology#GGAA Microsatellite Enhancer Reprogramming
    - pathophysiology#BAF Complex Retargeting
    - pathophysiology#STAG2-Modified Enhancer State
    would_refute:
    - pathophysiology#STAG2-Modified Enhancer State
    evidence:
    - reference: PMID:36658219
      reference_title: "ETV6 dependency in Ewing sarcoma by antagonism of EWS-FLI1-mediated enhancer activation."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "with EWS-FLI1 for binding to select DNA elements enriched for short GGAA repeat"
      explanation: Supports testing ETV6 as an enhancer-grammar modifier.
    - reference: PMID:41950086
      reference_title: "STAG2 loss amplifies EWS-FLI1-driven microsatellite enhancer activity promoting Ewing sarcoma aggressiveness."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "activity at multimeric microsatellite enhancers."
      explanation: Supports testing repeat-length-dependent STAG2 effects.
  evidence:
  - reference: PMID:25453903
    reference_title: "EWS-FLI1 utilizes divergent chromatin remodeling mechanisms to directly activate or repress enhancer elements in Ewing sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "induce chromatin opening and create de novo enhancers that physically interact"
    explanation: Establishes the enhancer phenomenon whose causal sequence rules remain unresolved.
  - reference: PMID:26214589
    reference_title: "Chimeric EWSR1-FLI1 regulates the Ewing sarcoma susceptibility gene EGR2 via a GGAA microsatellite."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "A risk allele connected adjacent GGAA repeats by"
    explanation: Supports germline repeat architecture as a testable enhancer-grammar variable.
  - reference: PMID:36787739
    reference_title: "Targeted long-read sequencing of the Ewing sarcoma 6p25.1 susceptibility locus identifies germline-somatic interactions with EWSR1-FLI1 binding."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "50 microsatellite alleles at 6p25.1 and observed"
    explanation: Supports long-read resolution of germline GGAA alleles as part of the enhancer-grammar gap.
  - reference: PMID:40215343
    reference_title: "(GGAA)(3)-Based TF-PROTACs Enable Targeted Degradation of ETV6 to Inhibit Ewing Sarcoma Growth."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "EWS::FLI1 at short GGAA repeats to restrain"
    explanation: Supports native ETS competition as a mechanistic component of enhancer grammar.
- discussion_id: gap_ewing_chromatin_reversal_screen
  prompt: >-
    Which EWS-FLI1-dependent chromatin-accessibility states are causal tumor
    dependencies rather than passenger signatures, and can an automated
    high-throughput chromatin assay distinguish therapeutically useful chromatin
    reversal from nonspecific cytotoxicity?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#EWS-FLI1 Fusion Oncogene
  - pathophysiology#EWS-FLI1 Hub and Dosage Control
  - pathophysiology#GGAA Microsatellite Enhancer Reprogramming
  - pathophysiology#ETV6 GGAA Counter-Regulation
  - pathophysiology#NuRD/CHD4 Repressive Chromatin Program
  - pathophysiology#Core Regulatory Circuitry Activation
  rationale: >-
    Ian Davis lab work showed that EWS-FLI1 retargets chromatin, creates
    nucleosome-depleted enhancer states, and can be assayed with automated
    high-throughput FAIRE. However, the therapeutic interpretation remains
    unresolved: a compound or degrader that reduces an Ewing chromatin signature
    could act by direct fusion-pathway reversal, by ETV6 or NuRD/HDAC/LSD1
    modifier biology, by reduced EWS-FLI1 expression, or by general toxicity.
    A mechanism-resolved chromatin perturbation screen would convert this
    chromatin phenotype into a decision rule for prioritizing causal nodes and
    cloud-lab-ready follow-up experiments.
  proposed_experiments:
  - experiment_id: exp_ewing_automated_chromatin_reversal_screen
    name: Automated EWS-FLI1 chromatin-reversal perturbation screen
    description: >-
      Run an automated plate-based chromatin-accessibility screen in Ewing
      sarcoma models using HT-FAIRE, ATAC-qPCR, or low-input ATAC-seq readouts
      at sentinel EWS-FLI1 GGAA enhancers, ETV6-competed short GGAA elements,
      and repressed mesenchymal enhancers. Screen annotated epigenetic compounds,
      targeted degraders, kinase/chemical-probe libraries, and EWS-FLI1 or ETV6
      perturbation controls, then triage hits by matched viability, fusion
      expression, enhancer activity, and transcriptional rescue.
    experiment_type:
      preferred_term: automated high-throughput chromatin-accessibility perturbation screen
    model_systems:
    - name: Ewing sarcoma chromatin-accessibility screening panel
      description: >-
        EWS-FLI1-positive Ewing sarcoma cell lines with sentinel GGAA enhancers
        and matched orthogonal chromatin, expression, and viability assays.
      experimental_model_type: CELL_LINE
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      publication: PMID:26929321
      modeled_mechanisms:
      - target: GGAA Microsatellite Enhancer Reprogramming
        description: Measures whether perturbations reverse fusion-dependent nucleosome depletion at GGAA enhancers.
      - target: ETV6 GGAA Counter-Regulation
        description: Tests whether ETV6-directed perturbation produces a separable short-GGAA enhancer state.
      - target: NuRD/CHD4 Repressive Chromatin Program
        description: Tests whether chromatin-repressive modifiers drive rescue of lineage or tumor-suppressive enhancers.
    perturbations:
    - name: Epigenetic compound and degrader library
      target: pathophysiology#GGAA Microsatellite Enhancer Reprogramming
      description: >
        Apply annotated epigenetic inhibitors, targeted degraders, and chemical
        probe libraries with dose and time gradients suitable for automated
        liquid handling.
    - name: EWS-FLI1 and ETV6 perturbation controls
      target: pathophysiology#EWS-FLI1 Fusion Oncogene
      description: >
        Include acute fusion knockdown or degron withdrawal, ETV6 degradation or
        knockdown, and vehicle controls to calibrate chromatin-reversal
        directionality.
      genes:
      - preferred_term: EWSR1
        term:
          id: hgnc:3508
          label: EWSR1
      - preferred_term: FLI1
        term:
          id: hgnc:3749
          label: FLI1
      - preferred_term: ETV6
        term:
          id: hgnc:3495
          label: ETV6
    readouts:
    - name: Sentinel chromatin-accessibility reversal
      target: pathophysiology#GGAA Microsatellite Enhancer Reprogramming
      description: >
        Quantify accessibility at EWS-FLI1-activated GGAA enhancers, ETV6-
        competed short GGAA elements, and fusion-repressed mesenchymal enhancers.
      biological_processes:
      - preferred_term: chromatin remodeling
        term:
          id: GO:0006338
          label: chromatin remodeling
      assays:
      - preferred_term: HT-FAIRE
      - preferred_term: ATAC-qPCR
      - preferred_term: low-input ATAC-seq
      direction: NEGATIVE
    - name: Mechanism-resolved transcriptional rescue
      target: pathophysiology#Core Regulatory Circuitry Activation
      description: >
        Pair chromatin hits with targeted RNA-seq or Perturb-seq to determine
        whether KLF15/TCF4/NKX2-2 circuitry, mesenchymal differentiation genes,
        EWS-FLI1 abundance, or generic stress pathways explain the response.
      biological_processes:
      - preferred_term: regulation of gene expression
        term:
          id: GO:0010468
          label: regulation of gene expression
      assays:
      - preferred_term: targeted RNA-seq
      - preferred_term: Perturb-seq
      - preferred_term: immunoblotting
      direction: NEGATIVE
    - name: Growth and toxicity separation
      target: pathophysiology#Tumor Cell Proliferation and Survival
      description: >
        Measure viability, apoptosis, and clonogenic growth in the same dose and
        time grid to separate mechanism-specific chromatin reversal from
        nonspecific cytotoxicity.
      biological_processes:
      - preferred_term: cell population proliferation
        term:
          id: GO:0008283
          label: cell population proliferation
      assays:
      - preferred_term: viability assay
      - preferred_term: apoptosis assay
      - preferred_term: clonogenic survival assay
      direction: NEGATIVE
    controls:
    - name: EWS-FLI1 knockdown positive control
      description: Calibrates the expected chromatin-accessibility direction for true fusion-pathway reversal.
    - name: Short-exposure viability control
      description: Flags compounds whose chromatin signal is secondary to acute cell loss or global toxicity.
    - name: Non-Ewing sarcoma comparator cells
      description: Tests whether hits reverse a Ewing-specific chromatin state rather than general chromatin accessibility.
    decision_criterion: >-
      A chromatin-reversal hit is prioritized when it reproducibly shifts
      sentinel EWS-FLI1 accessibility and transcription toward the fusion-
      withdrawal state at concentrations and times that precede broad
      cytotoxicity, and when the response maps to a declared mechanism node
      such as ETV6 competition, NuRD/HDAC/LSD1 repression, or EWS-FLI1 dosage.
    would_support:
    - pathophysiology#GGAA Microsatellite Enhancer Reprogramming
    - pathophysiology#ETV6 GGAA Counter-Regulation
    - pathophysiology#NuRD/CHD4 Repressive Chromatin Program
    - pathophysiology#Tumor Cell Proliferation and Survival
    would_refute:
    - pathophysiology#GGAA Microsatellite Enhancer Reprogramming
    - pathophysiology#ETV6 GGAA Counter-Regulation
    evidence:
    - reference: PMID:26929321
      reference_title: "High-throughput small molecule screen identifies inhibitors of aberrant chromatin accessibility."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "high-throughput, automated assay."
      explanation: Supports the feasibility of automated chromatin-accessibility screening in this disease context.
    - reference: PMID:26929321
      reference_title: "High-throughput small molecule screen identifies inhibitors of aberrant chromatin accessibility."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "regions of aberrant nucleosome"
      explanation: Supports using EWS-FLI1-dependent accessibility regions as the primary assay signal.
    - reference: PMID:40215343
      reference_title: "(GGAA)(3)-Based TF-PROTACs Enable Targeted Degradation of ETV6 to Inhibit Ewing Sarcoma Growth."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "EWS::FLI1 at short GGAA repeats to restrain"
      explanation: Supports including ETV6 perturbation as an orthogonal enhancer-state control.
  evidence:
  - reference: PMID:22086061
    reference_title: "Tumor-specific retargeting of an oncogenic transcription factor chimera results in dysregulation of chromatin and transcription."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "EWS-FLI chimera acquired chromatin-altering activity"
    explanation: Establishes the EWS-FLI1 chromatin-altering phenomenon that motivates the knowledge gap.
  - reference: PMID:26929321
    reference_title: "High-throughput small molecule screen identifies inhibitors of aberrant chromatin accessibility."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "does not depend on the a priori selection of a single molecular target"
    explanation: Supports chromatin-signature screening as a target-agnostic route to mechanism discovery.
- discussion_id: gap_ewing_replication_stress_response
  prompt: >-
    Which EWS-FLI1-induced DHX9/R-loop, SLFN11 fork-blocking, BRCA1, STAG2, and
    USP1-survivin states determine whether replication stress causes
    chemosensitivity, PARP/USP1/ATR inhibitor vulnerability, or survival and
    relapse?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#R-loop Resolution and Replication-Fork Vulnerability
  - pathophysiology#Replication Stress and Impaired Homologous Recombination
  - pathophysiology#STAG2-Modified Enhancer State
  - pathophysiology#Tumor Cell Proliferation and Survival
  - treatment#Neoadjuvant Chemotherapy
  rationale: >-
    Ewing sarcoma is sensitive to genotoxic chemotherapy, and EWS-FLI1 creates
    R-loops, replication stress, SLFN11-dependent fork blocking, and
    homologous-recombination defects. However, high-risk and relapsed tumors
    survive therapy, and it is not yet clear which molecular stress-state
    measurements predict response to PARP, ATR, USP1, or chemotherapy
    combinations.
  proposed_experiments:
  - experiment_id: exp_ewing_replication_stress_pharmacodynamic_panel
    name: Replication-stress pharmacodynamic response panel
    description: >-
      Profile matched diagnosis-relapse samples, patient-derived cultures, and
      Ewing sarcoma cell lines under etoposide, doxorubicin, PARP inhibition,
      USP1 inhibition, and combinations. Perturb EWS-FLI1, DHX9, SLFN11, BRCA1,
      USP1, and BIRC5 to separate primary fusion-induced stress, fork blocking,
      and survival adaptation.
    experiment_type:
      preferred_term: perturbation-response pharmacodynamic experiment
    model_systems:
    - name: Matched Ewing sarcoma patient-derived culture and cell-line panel
      description: >-
        Human Ewing sarcoma cultures and cell lines stratified by therapy
        response, STAG2 status, and replication-stress markers.
      experimental_model_type: PRIMARY_CELL_CULTURE
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      publication: PMID:37478161
      modeled_mechanisms:
      - target: R-loop Resolution and Replication-Fork Vulnerability
        description: Measures DHX9/R-loop and SLFN11 fork-blocking states under treatment.
      - target: Replication Stress and Impaired Homologous Recombination
        description: Measures R-loops, replication stress, and DNA repair state under treatment.
    perturbations:
    - name: Genotoxic and targeted stress perturbation
      target: pathophysiology#Replication Stress and Impaired Homologous Recombination
      description: >
        Compare standard genotoxic agents with PARP and USP1 inhibition under
        fusion knockdown or repair/survival gene perturbation.
      genes:
      - preferred_term: DHX9
        term:
          id: hgnc:2750
          label: DHX9
      - preferred_term: SLFN11
        term:
          id: hgnc:26633
          label: SLFN11
      - preferred_term: BRCA1
        term:
          id: hgnc:1100
          label: BRCA1
      - preferred_term: USP1
        term:
          id: hgnc:12607
          label: USP1
      - preferred_term: BIRC5
        term:
          id: hgnc:593
          label: BIRC5
    readouts:
    - name: R-loop, fork-blocking, and homologous-recombination response
      target: pathophysiology#R-loop Resolution and Replication-Fork Vulnerability
      description: >
        Measure R-loop burden, DHX9 occupancy, SLFN11 chromatin recruitment,
        replication fork stress, gamma-H2AX, RAD51 foci, BRCA1 localization, and
        transcription-coupled DNA damage after treatment.
      biological_processes:
      - preferred_term: double-strand break repair via homologous recombination
        term:
          id: GO:0000724
          label: double-strand break repair via homologous recombination
      assays:
      - preferred_term: DRIP-seq
      - preferred_term: DNA fiber assay
      - preferred_term: immunofluorescence DNA repair foci assay
      direction: NEGATIVE
    - name: Cell survival under replication stress
      target: pathophysiology#Tumor Cell Proliferation and Survival
      description: >
        Quantify apoptosis, clonogenic survival, and drug synergy across
        chemotherapy, PARP inhibition, and USP1 inhibition.
      biological_processes:
      - preferred_term: cell population proliferation
        term:
          id: GO:0008283
          label: cell population proliferation
      assays:
      - preferred_term: clonogenic survival assay
      - preferred_term: apoptosis assay
      direction: NEGATIVE
    controls:
    - name: EWS-FLI1 knockdown or degron control
      description: Tests whether replication-stress markers are fusion-dependent.
    - name: Isogenic USP1 or BIRC5 rescue
      description: Separates USP1-survivin survival adaptation from upstream R-loop burden.
    decision_criterion: >-
      A predictive stress-state model is supported when baseline or early
      treatment-induced R-loop/BRCA1/USP1-survivin readouts reproducibly predict
      death, survival, or drug synergy across independent patient-derived models
      and are reversed by the corresponding genetic rescue or withdrawal.
    would_support:
    - pathophysiology#R-loop Resolution and Replication-Fork Vulnerability
    - pathophysiology#Replication Stress and Impaired Homologous Recombination
    - pathophysiology#Tumor Cell Proliferation and Survival
    would_refute:
    - pathophysiology#Replication Stress and Impaired Homologous Recombination
    evidence:
    - reference: PMID:29513652
      reference_title: "EWS-FLI1 increases transcription to cause R-loops and block BRCA1 repair in Ewing sarcoma."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "etoposide, but the underlying molecular basis of this sensitivity is unclear."
      explanation: Supports the unresolved response-mechanism framing.
    - reference: PMID:37478161
      reference_title: "USP1 Expression Driven by EWS::FLI1 Transcription Factor Stabilizes Survivin and Mitigates Replication Stress in Ewing Sarcoma."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "USP1 inhibition sensitizes cells to doxorubicin and etoposide treatment."
      explanation: Supports USP1 as a testable stress-survival target.
    - reference: PMID:40721661
      reference_title: "EWS::FLI1-DHX9 interaction promotes Ewing sarcoma sensitivity to DNA topoisomerase 1 poisons by altering R-loop metabolism."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "sequestering DHX9 helicase, ultimately resulting in"
      explanation: Supports testing DHX9/R-loop state as a predictive pharmacodynamic readout.
    - reference: PMID:25779942
      reference_title: "SLFN11 Is a Transcriptional Target of EWS-FLI1 and a Determinant of Drug Response in Ewing Sarcoma."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "EWS-FLI1 binds near the transcription start site of SLFN11 promoter"
      explanation: Supports testing SLFN11 as an EWS-FLI1-driven predictive biomarker.
  evidence:
  - reference: PMID:37478161
    reference_title: "USP1 Expression Driven by EWS::FLI1 Transcription Factor Stabilizes Survivin and Mitigates Replication Stress in Ewing Sarcoma."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "override activation of apoptosis or cellular senescence in response to increased"
    explanation: Directly states the survival-under-replication-stress knowledge gap.
  - reference: PMID:40721661
    reference_title: "EWS::FLI1-DHX9 interaction promotes Ewing sarcoma sensitivity to DNA topoisomerase 1 poisons by altering R-loop metabolism."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "excessive DHX9 or reduced EWS::FLI1 levels render"
    explanation: Supports unresolved resistance prediction involving DHX9 and fusion dosage.
- discussion_id: gap_ewing_stag2_cohesin_high_risk_mechanism
  prompt: >-
    In STAG2-altered Ewing sarcoma, which causal arm best explains high-risk
    disease: multimeric GGAA enhancer amplification, PRC2/CTCF chromatin
    rewiring, replication-fork repair vulnerability, or a context-specific
    combination of these mechanisms?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#STAG2-Modified Enhancer State
  - pathophysiology#GGAA Microsatellite Enhancer Reprogramming
  - pathophysiology#R-loop Resolution and Replication-Fork Vulnerability
  - pathophysiology#Replication Stress and Impaired Homologous Recombination
  - phenotype#Metastatic Disease
  rationale: >-
    The reviewed literature supports that STAG2 loss reshapes GGAA
    enhancer-promoter contacts and is clinically adverse, but the mechanism is
    not a single clean edge. EWS-FLI1-dependent long-GGAA contacts, EWS-FLI1-
    independent CTCF changes, PRC2 derepression, TP53 co-alteration, and
    replication-fork stress could each contribute differently across cohorts,
    ancestry backgrounds, and treatment states.
  proposed_experiments:
  - experiment_id: exp_ewing_stag2_primary_tumor_chromatin_ddr_atlas
    name: STAG2-stratified primary-tumor chromatin and DDR atlas
    description: >-
      Profile STAG2-positive and STAG2-negative primary and relapse Ewing
      sarcoma specimens with matched WGS, long-read GGAA microsatellite typing,
      RNA-seq, ATAC-seq or CUT&Tag, H3K27ac/H3K27me3, CTCF/cohesin occupancy,
      and DNA-damage response markers. Pair the tumor atlas with isogenic
      STAG2 rescue or knockout in Ewing sarcoma cultures to separate enhancer,
      PRC2/CTCF, and replication-stress arms.
    experiment_type:
      preferred_term: STAG2-stratified multi-omic mechanism atlas
    model_systems:
    - name: STAG2-positive and STAG2-negative Ewing sarcoma tumor cohort
      description: >-
        Banked diagnostic and relapse Ewing sarcoma tumors with STAG2 protein
        status, mutation calls, clinical outcome, and ancestry-aware GGAA repeat
        genotyping.
      experimental_model_type: OTHER
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      publication: PMID:36221002
      modeled_mechanisms:
      - target: STAG2-Modified Enhancer State
        description: Tests whether STAG2 loss produces the same high-risk chromatin state in primary tumors.
      - target: GGAA Microsatellite Enhancer Reprogramming
        description: Measures multimeric GGAA enhancer amplification and enhancer-promoter contact strength.
      - target: Replication Stress and Impaired Homologous Recombination
        description: Measures whether STAG2 loss adds fork and repair stress to the fusion-driven DDR state.
    perturbations:
    - name: STAG2 rescue or knockout
      target: pathophysiology#STAG2-Modified Enhancer State
      description: >
        Restore STAG2 in STAG2-deficient Ewing sarcoma models and remove STAG2
        in matched STAG2-proficient models while stratifying by TP53 status.
      genes:
      - preferred_term: STAG2
        term:
          id: hgnc:11355
          label: STAG2
    readouts:
    - name: Enhancer, PRC2, and CTCF arm partition
      target: pathophysiology#STAG2-Modified Enhancer State
      description: >
        Quantify EWS-FLI1 occupancy at short and long GGAA repeats,
        enhancer-promoter contacts, H3K27ac, H3K27me3, CTCF loops, and
        neurodevelopmental or migratory target-gene expression.
      biological_processes:
      - preferred_term: chromosome organization
        term:
          id: GO:0051276
          label: chromosome organization
      assays:
      - preferred_term: long-read microsatellite genotyping
      - preferred_term: Capture Hi-C
      - preferred_term: ATAC-seq
      - preferred_term: CUT&Tag
      direction: POSITIVE
    - name: Replication-fork and repair-stress response
      target: pathophysiology#Replication Stress and Impaired Homologous Recombination
      description: >
        Measure DNA fiber fork progression, gamma-H2AX, RAD51 foci, PARP/ATR
        inhibitor response, and chemotherapy response by STAG2 state.
      biological_processes:
      - preferred_term: DNA replication
        term:
          id: GO:0006260
          label: DNA replication
      assays:
      - preferred_term: DNA fiber assay
      - preferred_term: immunofluorescence DNA repair foci assay
      - preferred_term: drug-response matrix
      direction: NEGATIVE
    controls:
    - name: STAG2-wild-type matched tumors
      description: Stage-, site-, age-, and ancestry-matched tumors retaining STAG2 expression.
    - name: Isogenic rescue controls
      description: STAG2 restoration or knockout controls that separate STAG2 effects from cell-line background.
    decision_criterion: >-
      The STAG2 high-risk model is strengthened if STAG2-negative primary tumors
      reproduce long-GGAA enhancer amplification and if isogenic rescue reverses
      the predicted enhancer, PRC2/CTCF, or DDR arm. A single dominant arm would
      be prioritized only if it predicts clinical outcome and drug response
      better than the alternatives.
    would_support:
    - pathophysiology#STAG2-Modified Enhancer State
    - pathophysiology#GGAA Microsatellite Enhancer Reprogramming
    - pathophysiology#Replication Stress and Impaired Homologous Recombination
    would_refute:
    - pathophysiology#STAG2-Modified Enhancer State
    evidence:
    - reference: PMID:39487368
      reference_title: "STAG2 loss in Ewing sarcoma alters enhancer-promoter contacts dependent and independent of EWS::FLI1."
      supports: SUPPORT
      evidence_source: IN_VITRO
      snippet: "cohesin-STAG2 facilitates communication between"
      explanation: Supports measuring STAG2-dependent long-GGAA enhancer-promoter contacts.
    - reference: PMID:36221002
      reference_title: "Adverse prognostic impact of the loss of STAG2 protein expression in patients with newly diagnosed localised Ewing sarcoma: A report from the Children's Oncology Group."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "carries a poor prognosis."
      explanation: Supports the need for primary-tumor clinical stratification by STAG2 loss.
  evidence:
  - reference: PMID:39487368
    reference_title: "STAG2 loss in Ewing sarcoma alters enhancer-promoter contacts dependent and independent of EWS::FLI1."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: "Changes in CTCF-dependent chromatin contacts involving"
    explanation: Supports the unresolved CTCF arm of the STAG2 mechanism.
  - reference: PMID:36221002
    reference_title: "Adverse prognostic impact of the loss of STAG2 protein expression in patients with newly diagnosed localised Ewing sarcoma: A report from the Children's Oncology Group."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "carries a poor prognosis."
    explanation: Supports STAG2 protein loss as a clinically meaningful high-risk state.
  - reference: PMID:25223734
    reference_title: "Genomic landscape of Ewing sarcoma defines an aggressive subtype with co-association of STAG2 and TP53 mutations."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "STAG2 mutations and CDKN2A deletions were mutually exclusive"
    explanation: Supports the need to stratify STAG2 effects against other high-risk genomic routes.
disease_term:
  preferred_term: Ewing sarcoma
  term:
    id: MONDO:0012817
    label: Ewing sarcoma

classifications:
  icdo_morphology:
    classification_value: Sarcoma
  harrisons_chapter:
  - classification_value: ONCOLOGY_HEMATOLOGY
📚

References & Deep Research

Deep Research

2
Disorder ▸

Disorder

  • Name: Ewing Sarcoma
  • Category:
  • Existing deep-research providers: falcon
  • Existing evidence reference count in YAML: 5

Key Pathophysiology Nodes

  • EWS-FLI1 Fusion Oncogene
  • Aberrant Transcriptional Regulation
  • Blocked Differentiation
  • Deep research literature mapping

Citation Inventory (for evidence mapping)

  • DOI:10.1158/1541-7786.mcr-20-0679
  • DOI:10.3389/fonc.2024.1388484
Falcon ▸
Disease Pathophysiology Research Report
Edison Scientific Literature 13 citations 2026-01-24T13:40:49.760866

Disease Pathophysiology Research Report

Target Disease - Disease Name: Ewing Sarcoma - MONDO ID: — - Category: Malignant small round cell tumor of bone/soft tissue

Pathophysiology description Ewing sarcoma (EwS) is defined by pathognomonic FET–ETS gene fusions, most commonly EWSR1::FLI1 generated by t(11;22)(q24;q12), with recurrent junction types (EWSR1 exon 7 to FLI1 exon 6 [type I] or exon 5 [type II]) (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). The fusion encodes a potent aberrant transcription factor that couples the low-complexity transactivation domain of EWSR1 to the ETS DNA-binding domain of FLI1; both halves are necessary for oncogenic activity, yet transformation efficiency depends on permissive cellular context (jimenez2024anepigeneticapproacha pages 21-24). EwS tumors are genomically “quiet” by point mutation burden (approximately 0.15–0.45 mutations/Mb) but display recurrent copy-number changes (e.g., gains of 8, 2, 1q; loss of 16q) and focal 9p loss with CDKN2A deletion; recurrent secondary alterations include STAG2 (~20%) and TP53 (5–20%), with adverse impact especially when co-mutated (jimenez2024anepigeneticapproachb pages 21-24, jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24).

At the chromatin level, EWSR1::FLI1 drives extensive enhancer reprogramming. The fusion binds canonical ETS motifs and uniquely occupies tandem GGAA microsatellite “super-enhancers,” creating de novo regulatory elements and activating lineage-inappropriate targets (e.g., NR0B1/DAX1); as summarized, the protein “binds tandem GGAA microsatellite repeats” to amplify transcriptional output beyond wild-type FLI1 (petrescu2024preclinicalmodelsfor pages 3-5). This enhanceropathy couples to transcriptional stress, R-loop formation, and replication stress, which engages ATR pathways and creates vulnerabilities to DNA damage response (DDR) agents such as PARP inhibitors (petrescu2024preclinicalmodelsfor pages 3-5). EWSR1::FLI1 also directly and indirectly remodels metabolic programs. It binds the ATF4 promoter and elevates ATF4, a master regulator of the serine biosynthesis pathway (SSP), while the scaffold protein menin is additionally required to sustain ATF4 and the broader ATF4-dependent transcriptome; inhibiting either EWSR1::FLI1 or menin reduces ATF4 and SSP enzymes (e.g., PHGDH) (jimenez2021ewsfli1andmenin pages 1-3).

Clinically, EwS presents as undifferentiated small round blue cell tumors, typically with strong membranous CD99 expression; outcomes are good for localized disease with dose-compressed chemotherapy but remain poor for metastatic/recurrent disease. A position summary reports five-year event-free survival (EFS) around 87% for localized disease and approximately 38% three-year EFS for recurrent/metastatic disease, with relapse driven by resistant clones (jimenez2024anepigeneticapproach pages 21-24). Trials targeting IGF1R and mTOR have shown limited yet notable activity in subsets, reflecting frequent IGF axis engagement in EwS biology (jimenez2024anepigeneticapproach pages 21-24).

Key concepts and definitions with current understanding - Initiating lesion: Balanced translocation producing EWSR1::FLI1 (or other FET–ETS fusions), often exon 7 of EWSR1 fused to exon 6 (type I) or exon 5 (type II) of FLI1 (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). URL: https://doi.org/ (as cited within 2024 thesis); publication year 2024 (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). - Chromatin enhanceropathy: EWSR1::FLI1 binds canonical ETS sites and GGAA microsatellites to establish de novo enhancers and high-output transcriptional programs (“binds tandem GGAA microsatellite repeats”) (petrescu2024preclinicalmodelsfor pages 3-5). URL: https://doi.org/10.3389/fonc.2024.1388484; publication date Jul 2024 (petrescu2024preclinicalmodelsfor pages 3-5). - Genomic landscape: Low SNV burden (0.15–0.45/Mb), recurrent CNAs (chr8, chr2, 1q gains; 16q loss), and TP53/STAG2 alterations with prognostic interaction (jimenez2024anepigeneticapproachb pages 21-24, jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). Publication year 2024 (jimenez2024anepigeneticapproachb pages 21-24, jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). - Metabolic rewiring: EWSR1::FLI1 and menin converge on ATF4 to upregulate serine biosynthesis; ATF4 is directly activated by EWSR1::FLI1 binding to its promoter (jimenez2021ewsfli1andmenin pages 1-3). URL: https://doi.org/10.1158/1541-7786.mcr-20-0679; publication date Mar 2021 (jimenez2021ewsfli1andmenin pages 1-3). - Diagnostic phenotype: Small round blue cell tumor with strong CD99; fusion is disease-defining (petrescu2024preclinicalmodelsfor pages 3-5, jimenez2024anepigeneticapproacha pages 21-24). URL: https://doi.org/10.3389/fonc.2024.1388484; publication date Jul 2024 (petrescu2024preclinicalmodelsfor pages 3-5).

Recent developments and latest research (2023–2024 priority) - 2024 epigenetics-focused synthesis: Updated compendium of EwS fusion biology, genomic landscape, and epigenetic targets, reiterating dominant EWSR1::FLI1 fusion types, low point-mutation burden, recurrent CNAs, and the need for epigenetic/DDR-targeted strategies (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). Publication year 2024. - 2024 preclinical models review: Emphasizes EWSR1::FLI1 enhancer rewiring at GGAA microsatellites, R-loop–associated genomic instability, and associated sensitivity to DDR targeting, integrating model systems that recapitulate these features (petrescu2024preclinicalmodelsfor pages 3-5). URL: https://doi.org/10.3389/fonc.2024.1388484; Jul 2024.

Current applications and real-world implementations - Molecular diagnosis: Detection of EWSR1::FLI1 (or alternate FET–ETS) fusion is the defining diagnostic test; morphology and CD99 support the diagnosis (petrescu2024preclinicalmodelsfor pages 3-5, jimenez2024anepigeneticapproacha pages 21-24). Jul 2024; 2024. - Systemic therapy: Standard dose-compressed chemotherapy achieves high EFS in localized disease; investigational/adjunct approaches include IGF1R antibodies and mTOR inhibitors, with limited success and need for biomarker-driven selection (jimenez2024anepigeneticapproach pages 21-24). Publication year 2024. - Emerging therapeutic rationale: DDR targeting (e.g., PARP inhibitors) leverages EWSR1::FLI1-induced transcriptional/replication stress and R-loops (petrescu2024preclinicalmodelsfor pages 3-5). Jul 2024.

Expert opinions and analysis from authoritative sources - Fusion-centric disease model: Contemporary synthesis underscores that the EWSR1::FLI1 chimeric transcription factor is the primary oncogenic driver, with cellular context determining permissiveness for transformation; ectopic fusion expression alone “often fails to recapitulate transformation,” arguing for a developmental window/cell-of-origin constraint (jimenez2024anepigeneticapproacha pages 21-24). 2024. - Enhancer rewiring as core pathophysiology: The capacity of EWSR1::FLI1 to create de novo enhancers at GGAA microsatellites is a unifying explanation for widespread transcriptional dysregulation and downstream vulnerabilities (petrescu2024preclinicalmodelsfor pages 3-5). 2024. - Metabolic dependency via ATF4: Menin and EWSR1::FLI1 co-regulate ATF4, sustaining serine biosynthesis; this axis links oncogenic transcription to metabolic plasticity and may yield therapeutic windows (jimenez2021ewsfli1andmenin pages 1-3). 2021.

Relevant statistics and data from recent studies - Mutation burden: ~0.15–0.45 mutations/Mb (jimenez2024anepigeneticapproachb pages 21-24, jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). 2024. - Fusion junction frequencies: EWSR1 exon 7 to FLI1 exon 6 (~60%, type I) and exon 5 (~25%, type II) (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). 2024. - Secondary alterations: STAG2 ~20%; TP53 5–20% (jimenez2024anepigeneticapproachb pages 21-24, jimenez2024anepigeneticapproacha pages 21-24). 2024. - Outcomes: Five-year EFS ~87% for localized disease; ~38% three-year EFS for metastatic/recurrent (jimenez2024anepigeneticapproach pages 21-24). 2024.

Structured knowledge for ontology/annotation - Key molecular players (HGNC): EWSR1 (EWSR1::FLI1 fusion; HGNC:3508), FLI1 (HGNC:3749), TP53 (HGNC:11998), STAG2 (HGNC:11354), CDKN2A (HGNC:1787), ATF4 (HGNC:792), PHGDH (HGNC:8922), MEN1 (menin; HGNC:7010) (jimenez2024anepigeneticapproacha pages 21-24, jimenez2021ewsfli1andmenin pages 1-3, jimenez2024anepigeneticapproach pages 21-24). Where directly supported: EWSR1, FLI1, TP53, STAG2, CDKN2A (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24); ATF4/PHGDH/MEN1 (jimenez2021ewsfli1andmenin pages 1-3). - Biological processes (GO examples, aligned to evidence): - Regulation of transcription by RNA polymerase II; enhancer activation/de novo enhancer formation at GGAA microsatellites (petrescu2024preclinicalmodelsfor pages 3-5). - Response to endoplasmic reticulum stress and amino acid biosynthetic process (serine biosynthesis) via ATF4 (jimenez2021ewsfli1andmenin pages 1-3). - DNA replication stress and DNA repair signaling engagement (linked to R-loops/ATR vulnerability) (petrescu2024preclinicalmodelsfor pages 3-5). - Cellular components: Chromatin, enhancers/super-enhancers (GGAA microsatellite-associated), nucleoplasm; cell membrane (CD99 immunophenotype) (petrescu2024preclinicalmodelsfor pages 3-5). - Cell types (CL terms): Primitive mesenchymal progenitors/neural crest–related progenitors implicated as permissive cells of origin; tumor cells are undifferentiated small round cells (petrescu2024preclinicalmodelsfor pages 3-5, jimenez2021ewsfli1andmenin pages 1-3). 2024; 2021. - Anatomical locations (UBERON): Long bones, pelvis, axial skeleton (general clinical domain, consistent with EwS bone/soft tissue presentation; diagnostic phenotype summarized in review) (petrescu2024preclinicalmodelsfor pages 3-5). - Chemical entities (CHEBI): Not specifically evidenced in the extracted items beyond general references to chemotherapy and targeted agents; IGF1R/mTOR targeted agents noted (jimenez2024anepigeneticapproach pages 21-24).

Detailed sections 1) Core Pathophysiology - Primary mechanisms: Oncogenic EWSR1::FLI1 fusion establishes aberrant transcriptional networks by binding ETS motifs and GGAA microsatellites, remodeling chromatin into de novo super-enhancers and amplifying target gene expression; this produces lineage-inappropriate programs and replication/transcription stress (petrescu2024preclinicalmodelsfor pages 3-5). The limited co-mutation landscape underscores the centrality of the fusion (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). - Dysregulated pathways: EWSR1::FLI1-driven enhancer programs converge on growth and survival signaling; clinically and translationally, the IGF1R/PI3K–AKT–mTOR axis has been repeatedly implicated and targeted (jimenez2024anepigeneticapproach pages 21-24). EWSR1::FLI1 and menin activate ATF4 and the serine biosynthesis pathway, linking oncogenic transcription to metabolic support (jimenez2021ewsfli1andmenin pages 1-3). - Affected processes: Transcriptional regulation, enhancer biogenesis, RNA processing/replication coupling (R-loops), metabolic reprogramming (serine biosynthesis), and DDR pathway engagement (petrescu2024preclinicalmodelsfor pages 3-5, jimenez2021ewsfli1andmenin pages 1-3).

2) Key Molecular Players - Genes/proteins: EWSR1::FLI1 fusion (defining driver); TP53, STAG2, CDKN2A as recurrent alterations (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). ATF4 and PHGDH are upregulated downstream of fusion/menin (jimenez2021ewsfli1andmenin pages 1-3). - Chemical entities/drugs: Historical and ongoing targeting of IGF1R and mTOR in the clinic (jimenez2024anepigeneticapproach pages 21-24). - Cell types: Undifferentiated small round tumor cells; proposed permissive progenitors include mesenchymal and neural crest–related stem/progenitor states (petrescu2024preclinicalmodelsfor pages 3-5, jimenez2021ewsfli1andmenin pages 1-3). - Anatomical locations: Bone and soft tissues; commonly long bones and pelvis (review scope) (petrescu2024preclinicalmodelsfor pages 3-5).

3) Biological Processes (for GO annotation) - Positive regulation of transcription by RNA polymerase II and enhancer assembly at GGAA microsatellites (petrescu2024preclinicalmodelsfor pages 3-5). - Cellular response to stress and amino acid biosynthetic process (serine biosynthesis) via ATF4 (jimenez2021ewsfli1andmenin pages 1-3). - DNA damage response to replication stress/R-loop accumulation (petrescu2024preclinicalmodelsfor pages 3-5).

4) Cellular Components - Chromatin (enhancers/super-enhancers), nucleoplasm; plasma membrane marker CD99 (diagnostic) (petrescu2024preclinicalmodelsfor pages 3-5).

5) Disease Progression - Sequence: Initiation by EWSR1::FLI1 fusion in a developmentally defined, permissive progenitor; establishment of enhancer-driven transcriptional programs; induction of replication/transcription stress and DDR engagement; acquisition of cooperating CNAs or secondary hits (e.g., STAG2, TP53) that may influence progression and therapy response; clinical presentation with rapidly growing bone/soft tissue masses; therapeutic response with high cure rates in localized disease but frequent resistance and relapse in metastatic/recurrent settings (jimenez2024anepigeneticapproacha pages 21-24, petrescu2024preclinicalmodelsfor pages 3-5, jimenez2024anepigeneticapproach pages 21-24).

6) Phenotypic Manifestations - Clinical: Painful bone/soft tissue mass; histology of undifferentiated small round blue cells with strong CD99; aggressive course when metastatic (petrescu2024preclinicalmodelsfor pages 3-5, jimenez2024anepigeneticapproach pages 21-24). - Mechanistic links: Fusion-driven enhanceropathy underlies proliferation/immaturity; DDR stress explains sensitivity to DNA-damaging regimens and rationale for PARP targeting; ATF4/serine pathway supports biosynthetic needs of rapidly proliferating cells (petrescu2024preclinicalmodelsfor pages 3-5, jimenez2021ewsfli1andmenin pages 1-3).

Evidence items with PMIDs/DOIs/URLs and dates - Jiménez MS. An epigenetic approach for Ewing sarcoma patients. 2024. Details: fusion types (type I/II), low mutation burden, recurrent CNAs, STAG2/TP53, clinical outcomes, IGF1R/mTOR targeting (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). Publication year 2024. - Petrescu DI et al. Preclinical models for bone sarcomas. Front Oncol. Jul 2024; emphasizes EWSR1::FLI1 enhancer rewiring at GGAA microsatellites, R-loop/DDR vulnerabilities, CD99 phenotype. DOI: 10.3389/fonc.2024.1388484; URL: https://doi.org/10.3389/fonc.2024.1388484 (petrescu2024preclinicalmodelsfor pages 3-5). - Jiménez JA et al. EWS-FLI1 and menin converge to regulate ATF4 activity. Mol Cancer Res. Mar 2021; shows EWSR1::FLI1 binding at ATF4 promoter, menin dependence, serine biosynthesis upregulation. DOI: 10.1158/1541-7786.mcr-20-0679; URL: https://doi.org/10.1158/1541-7786.mcr-20-0679 (jimenez2021ewsfli1andmenin pages 1-3).

Direct quotes supporting key statements - “binds tandem GGAA microsatellite repeats” (on EWSR1::FLI1 enhancer binding) (petrescu2024preclinicalmodelsfor pages 3-5). - “ectopic expression alone often fails to recapitulate transformation,” emphasizing context dependency (jimenez2024anepigeneticapproacha pages 21-24).

Notes and limitations - Additional emerging mechanisms (e.g., detailed roles of Polycomb/LSD1, ferroptosis control, immune axes such as MIF–CD74, CD99 immunobiology, and liquid biopsy ctDNA measures) are active research areas but were not captured in the extracted evidence set used here; they should be integrated when primary 2023–2024 sources are available for citation.

Gene/protein annotations with ontology terms (examples; evidence-linked) - EWSR1 (HGNC:3508) and FLI1 (HGNC:3749): fusion oncoprotein EWSR1::FLI1; function: transcription factor activity; process: positive regulation of transcription, enhancer activation at GGAA microsatellites (petrescu2024preclinicalmodelsfor pages 3-5, jimenez2024anepigeneticapproacha pages 21-24). - ATF4 (HGNC:792): transcription factor; processes: cellular response to stress; regulation of serine biosynthetic process (jimenez2021ewsfli1andmenin pages 1-3). - PHGDH (HGNC:8922): serine biosynthesis enzyme; process: L-serine biosynthetic process (downstream of ATF4 in EwS) (jimenez2021ewsfli1andmenin pages 1-3). - TP53 (HGNC:11998), STAG2 (HGNC:11354), CDKN2A (HGNC:1787): tumor suppressors/cohesin; processes: DNA damage response, cell cycle regulation; alterations recurrent in EwS (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24).

Phenotype associations (HP terms; evidence-linked narrative) - HP:0009732 (Bone pain) and HP:0100753 (Bone neoplasm) consistent with EwS presentation; undifferentiated small round cell histology and strong CD99 immunostaining (petrescu2024preclinicalmodelsfor pages 3-5). (Note: phenotype terms aligned by clinical convention; narrative support from cited reviews.)

Cell type involvement (CL terms) - CL:0000134 (mesenchymal stem cell) and neural crest–related progenitors as permissive/transformed lineages; tumor cells are undifferentiated small round cells (petrescu2024preclinicalmodelsfor pages 3-5, jimenez2021ewsfli1andmenin pages 1-3).

Anatomical locations (UBERON terms) - UBERON:0001474 (long bone), UBERON:0002348 (pelvis) as common sites for primary EwS (review context) (petrescu2024preclinicalmodelsfor pages 3-5).

Chemical entities (CHEBI) - Agents targeting IGF1R/mTOR pathways have been trialed clinically in EwS; specific compounds not detailed in extracted text (jimenez2024anepigeneticapproach pages 21-24).

Citations - Jiménez MS. An epigenetic approach for Ewing sarcoma patients. 2024 (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24). - Petrescu DI et al. Preclinical models for the study of pediatric solid tumors: focus on bone sarcomas. Front Oncol. Jul 2024. DOI: 10.3389/fonc.2024.1388484. URL: https://doi.org/10.3389/fonc.2024.1388484 (petrescu2024preclinicalmodelsfor pages 3-5). - Jiménez JA et al. EWS-FLI1 and Menin Converge to Regulate ATF4 Activity in Ewing Sarcoma. Mol Cancer Res. Mar 2021. DOI: 10.1158/1541-7786.mcr-20-0679. URL: https://doi.org/10.1158/1541-7786.mcr-20-0679 (jimenez2021ewsfli1andmenin pages 1-3). - Additional overview excerpts on fusion structure/genomic landscape/outcomes from 2024 thesis (jimenez2024anepigeneticapproachb pages 21-24, jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24).

References (context IDs) (jimenez2024anepigeneticapproacha pages 21-24, jimenez2024anepigeneticapproach pages 21-24, petrescu2024preclinicalmodelsfor pages 3-5, jimenez2021ewsfli1andmenin pages 1-3, jimenez2024anepigeneticapproachb pages 21-24)

References

  1. (jimenez2024anepigeneticapproacha pages 21-24): M Sánchez Jiménez. An epigenetic approach for ewing sarcoma patients. Unknown journal, 2024.

  2. (jimenez2024anepigeneticapproach pages 21-24): M Sánchez Jiménez. An epigenetic approach for ewing sarcoma patients. Unknown journal, 2024.

  3. (jimenez2024anepigeneticapproachb pages 21-24): M Sánchez Jiménez. An epigenetic approach for ewing sarcoma patients. Unknown journal, 2024.

  4. (petrescu2024preclinicalmodelsfor pages 3-5): D. I. Petrescu, J. Yustein, Atreyi Dasgupta, Joanna Kitlinska, and Massimo Broggini. Preclinical models for the study of pediatric solid tumors: focus on bone sarcomas. Frontiers in Oncology, Jul 2024. URL: https://doi.org/10.3389/fonc.2024.1388484, doi:10.3389/fonc.2024.1388484. This article has 7 citations and is from a poor quality or predatory journal.

  5. (jimenez2021ewsfli1andmenin pages 1-3): Jennifer A. Jiménez, April A. Apfelbaum, Allegra G. Hawkins, Laurie K. Svoboda, Abhijay Kumar, Ramon Ocadiz Ruiz, Alessandra X. Garcia, Elena Haarer, Zeribe C. Nwosu, Joshua Bradin, Trupta Purohit, Dong Chen, Tomasz Cierpicki, Jolanta Grembecka, Costas A. Lyssiotis, and Elizabeth R. Lawlor. Ews-fli1 and menin converge to regulate atf4 activity in ewing sarcoma. Molecular Cancer Research, 19:1182-1195, Mar 2021. URL: https://doi.org/10.1158/1541-7786.mcr-20-0679, doi:10.1158/1541-7786.mcr-20-0679. This article has 13 citations and is from a peer-reviewed journal.