CHEK2-related Cancer Predisposition

Mendelian MONDO:0700271 Pathograph 18 Show in embeddings browser

CHEK2-related cancer predisposition is an autosomal dominant susceptibility associated with germline pathogenic variants in the checkpoint kinase gene CHEK2. Female breast cancer is the best-established manifestation, with increased contralateral breast and prostate cancer risks and a smaller absolute male breast cancer risk. Penetrance varies with the allele, age, sex, family history and other modifiers. Common lower-risk missense variants, including p.Ile157Thr, require different risk interpretation from truncating variants. CHK2 participates in DNA-damage signaling, but checkpoint defects are context dependent and CHEK2-associated tumors generally lack the BRCA-like homologous-recombination-deficiency profile. Somatic second hits occur in a subset of tumors; neither their presence nor their absence defines every carrier-associated cancer. Clinical management uses individualized surveillance and cancer-specific treatment. CHEK2 does not cause Li-Fraumeni syndrome.

Ask OpenScientist

Ask a research question about CHEK2-related Cancer Predisposition. OpenScientist will conduct autonomous deep research using the Disorder Mechanisms Knowledge Base and PubMed literature (typically 10-30 minutes).

Submitting...

Do not include personal health information in your question. Questions and results are cached in your browser's local storage.

👪

Inheritance

Autosomal dominant HP:0000006

Most individuals have a heterozygous germline pathogenic variant. A transmitting parent may or may not have developed cancer; transmission is 50% for each child of a heterozygote. Rare biallelic genotypes have a broader and variant-dependent cancer phenotype.

Autosomal dominant inheritance

Show evidence (3 references)

PMID:40440438 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Most individuals with CHEK2-related cancer predisposition have a heterozygous pathogenic variant. Rarely, affected individuals have biallelic pathogenic variants."

GeneReviews statement of the inheritance pattern and the rarity of biallelic disease.

PMID:40440438 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The vast majority of individuals with a heterozygous germline CHEK2 pathogenic variant inherited the pathogenic variant from a parent who may or may not have had a cancer diagnosis."

Most variants are inherited, but the source does not establish that most transmitting parents are cancer-free.

PMID:40440438 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The offspring of an individual identified as having a heterozygous germline CHEK2 pathogenic variant have a 50% chance of inheriting the pathogenic variant."

The transmission risk quoted to families in genetic counselling.

Discussions and Knowledge Gaps

Which CHK2-dependent processes mediate human tumor susceptibility?

KNOWLEDGE GAP chek2_oncogenic_route_unknown

Attached to

pathophysiology#Attenuated CHK2 Damage Response Signaling pathophysiology#Somatic CHEK2 Second-Hit Alteration

Checkpoint and apoptotic effects differ across models. Second hits are not universal, and genomic analyses distinguish CHEK2 deficiency from BRCA1/2 deficiency. In 16 breast and non-breast tumors from nine c.1100del homozygotes, no sample reached the study LST threshold for homologous-recombination deficiency; SBS3 contributed to two tumors but was not the dominant pattern. These data constrain a BRCA-like mechanism without excluding all DNA-repair functions.

Show evidence (2 references)

PMID:38848470 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"None of the analyzed cancers presented with an LST count of 15 or more, which is considered the cutoff value for HRD."

Direct genomic analysis of 16 tumors from nine germline c.1100del homozygotes.

PMID:38848470 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"SBS3, the HRD-related mutational signature (17), was observed to some level in 13% (2/16) of CHEK2-deficient cancers"

The minority SBS3 signal prevents an absolute claim that this signature never occurs.

Is CHEK2 a Li-Fraumeni syndrome gene?

CONTROVERSY RESOLVED chek2_not_li_fraumeni

Attached to

disease#

The historical association has been refuted. CHEK2 predisposition should not be assigned TP53-related Li-Fraumeni surveillance solely on that historical claim.

Show evidence (1 reference)

PMID:37490054 REFUTE DIRECT REVIEW SYNTHESIS Other

"a large body of evidence has conclusively shown that variants in CHEK2 are not associated with Li-Fraumeni syndrome"

The ACMG review refutes the historical gene-disease claim.

How should variant-specific risk and other modifiers be combined?

KNOWLEDGE GAP chek2_risk_is_a_distribution

Attached to

disease#

Absolute risk depends on genotype, age, sex, family history and other genetic and non-genetic factors. Population biobanks and cancer clinics sample different risk distributions. Polygenic risk estimates have predominantly European-ancestry validation, limiting transfer to other populations.

Show evidence (3 references)

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Although CHEK2 is considered a moderate penetrance gene, cancer risks may be considered as a continuous variable, which are influenced by family history and other modifiers."

Clinical guidance supports individualized rather than uniform lifetime risk.

PMID:41396600 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Participants in MyCode and UKBB are predominantly of European ancestry. Copy-number variants in CHEK2 were not evaluated due to limited data availability in UKBB."

Population and assay limitations constrain the new genome-first cohort results.

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"the genome-wide association studies used to identify PRS lacked diversity and are predominantly based on individuals of European ancestry."

Ancestry-specific validation limits transferability of polygenic risk models.

Which additional tumor associations warrant clinical action?

KNOWLEDGE GAP chek2_wider_tumour_spectrum

Attached to

disease#

A 2025 genome-first study replicated kidney, bladder and lymphoid leukemia associations in MyCode and UK Biobank. Thyroid association appeared only in MyCode; colorectal findings remain discordant across studies. Bonferroni correction was applied to organ-system groups, not individual cancer types, and absolute risks were not estimated. Association evidence therefore does not establish benefit from enhanced organ-specific screening. Testicular germ-cell tumor evidence is separately represented with its limits.

Show evidence (3 references)

PMID:41396600 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"This work provides substantial evidence from both cohorts of significantly increased risk for kidney cancer, bladder cancer, and chronic lymphocytic leukemia (CLL)."

The primary two-biobank analysis adds replicated associations to the older clinical-review evidence.

PMID:41396600 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"A significant excess of malignant neoplasm of thyroid and other endocrine tumors (C73-C75) was observed in MyCode but not UKBB"

The thyroid association did not replicate across these cohorts.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"To date, there are no recommendations for enhanced surveillance for other cancers."

The March 2026 clinical chapter distinguishes reported associations from actionable surveillance.

What are the penetrance and optimal surveillance of biallelic genotypes?

KNOWLEDGE GAP chek2_biallelic_risk

Attached to

disease#

The 2024 series included 294 individuals, 159 homozygous for p.Ile157Thr. Overall 157 had at least one malignancy or premalignancy, and 55 of those 157 had multiple such tumors. Among affected women, biallelic loss-of-function variants were associated with earlier onset and more multiple tumors than homozygous p.Ile157Thr. Ascertainment and missing follow-up prevent lifetime penetrance estimates. These genotype strata do not establish a uniform recessive developmental syndrome.

Show evidence (2 references)

PMID:38362852 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"In total, 157 individuals (53.4%; 157/294 individuals) developed ≥1 (pre)malignancy."

The denominator includes affected and unaffected individuals and must not be described as 294 null genotypes.

url:https://pure.rug.nl/ws/portalfiles/portal/1081701784/PIIS1098360024000340.pdf SUPPORT DIRECT PRIMARY RESULT Human Clinical

"55 in- dividuals (35%) developed multiple (pre)malignancies"

This institutional PDF is the full text of PMID:38362852, not a separate study. Its primary results report 55 of 157 affected individuals with multiple tumors; the later discussion overstates this as more than half of all participants.

Does CHEK2 genotype independently worsen cancer outcome?

KNOWLEDGE GAP chek2_prognosis_by_context

Attached to

disease#

Earlier c.1100del breast-cancer cohorts reported heterogeneous survival results. A 2025 genome-first analysis found no significant all-cause survival difference between carriers with cancer and controls with cancer, while overall mortality differed only in UK Biobank, mainly after age 75. These endpoints and ascertainment schemes do not directly resolve variant-specific breast-cancer mortality. Prognosis should be interpreted by cancer type, stage, treatment and competing risks.

Show evidence (3 references)

PMID:41396600 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"There was no statistical difference in all-cause mortality among individuals with cancer between case participants in the all-variant group and control participants in both MyCode"

The primary analysis concerns all-cause mortality among people with cancer, not a breast-cancer-specific survival endpoint.

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"There was no significant effect on long-term outcome, compared with more than 3000 wild-type controls."

The practice review describes one negative survival study alongside reports of poorer c.1100del-associated outcomes.

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Nearly all previous studies had found significantly adverse outcomes (measured variously as overall survival, BC-specific survival and incidence of CBC) for CHEK2 c.1100del heterozygotes, with or without the administration of adjuvant chemotherapy and/or hormone therapy."

The ACMG synthesis records adverse findings alongside null studies; the endpoints include survival and contralateral cancer and are not interchangeable.

⚙

Pathophysiology

Germline CHEK2 Loss of Function

Mechanism confidence: Established

Truncating, splice-disrupting and deletion alleles can reduce functional CHK2 dosage or kinase activity. The c.1100del founder frameshift is a well-studied loss-of-function allele. Missense effects range from severe loss to partial, assay-dependent dysfunction; biochemical impairment does not by itself establish clinically actionable penetrance.

CHEK2 hgnc:16627

Genetic context CHEK2 hgnc:16627 variant_origin: GERMLINE functional_impact_category: LOSS_OF_FUNCTION

protein serine/threonine kinase activity GO:0004674 ↓ DECREASED

Experimental models

Recombinant CHK2 p.Ile157Thr biochemical assay OTHER Measures partial missense dysfunction in a defined biochemical system.

Animal models

Chk2 1100delC knock-in mouse Mus musculus perturbs Introduces the founder-equivalent truncating allele.

Chk2-null and Mre11-complex compound-mutant mice Mus musculus perturbs Deletes Chk2 with or without an additional damage-response defect.

Downstream

Attenuated CHK2 Damage Response Signaling Reduced functional CHK2 impairs its contribution to DNA-damage signaling.

Show evidence (2 references)

PMID:33322746 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The first functional analysis revealed that c.1100delC completely abrogates CHK2 kinase activity"

Review synthesis of functional work on the truncating founder allele.

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"there is evidence that the common variant p.(Ile157Thr) adversely affects protein function and is therefore “deleterious;” yet, its penetrance is low and in isolation not at a level of clinical actionability"

Separates functional impairment from cancer penetrance and clinical actionability.

Somatic CHEK2 Second-Hit Alteration

Mechanism confidence: Established

Somatic loss of the remaining CHEK2 allele is observed in some carrier-associated breast tumors. A selected pathology series found biallelic alteration with loss of heterozygosity in 13 of 23 sequenced cancers. This is a tumor observation, not evidence that all carrier tumors are CHEK2-null or that reduced checkpoint signaling directly causes allele loss.

Genetic context CHEK2 hgnc:16627 variant_origin: SOMATIC functional_impact_category: LOSS_OF_FUNCTION

Acquired loss of the remaining allele in a subset of germline-variant-associated breast cancers.

Downstream

Attenuated CHK2 Damage Response Signaling A second hit can further reduce CHK2 signaling in the affected tumor; the degree of functional loss depends on the alleles.

Show evidence (1 reference)

PMID:38091153 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Biallelic CHEK2 alteration with loss of heterozygosity was identified in most BCs (57%, 13/23) by NGS."

The selected tumor series directly documents second-hit events; germline and somatic findings must be distinguished.

Attenuated CHK2 Damage Response Signaling

Mechanism confidence: Provisional

Activated ATM can phosphorylate CHK2, which regulates multiple downstream effectors of arrest and apoptosis. CHEK2 deficiency reduces this signaling contribution without necessarily abolishing p53 activation, S-phase arrest or G2/M arrest. Model, allele, cell type and DNA-damage stimulus determine the observed defect.

DNA damage checkpoint signaling GO:0000077 ↓ DECREASED

Experimental models

Chk2-null mouse fibroblast and thymocyte assays PRIMARY CELL CULTURE Tests the remaining G2/M checkpoint response after Chk2 deletion.

Downstream

Increased CDC25A Abundance Reduced CHK2-dependent regulation of CDC25A turnover is a candidate route to higher protein abundance in the 1100delC model.

Reduced Damage-Induced Apoptosis Loss of CHK2 reduces selected p53-dependent proapoptotic responses; parallel ATM/MRE11 activity modifies severity.

Show evidence (2 references)

PMID:33322746 SUPPORT DIRECT REVIEW SYNTHESIS Other

"ATM phosphorylates CHK2 and other proteins orchestrating DDSB repair and DDR. CHK2 overlaps some ATM targets, amplifies an ATM-triggered signal, and increases the DDR regulation fidelity."

The review places CHK2 within a partially redundant damage-response network.

PMID:18614044 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Inhibition of the G2/M transition following DNA damage (the G2/M checkpoint), which is defective in Nbs1ΔB/ΔB and Mre11ATLD1/ATLD1 cultures, occurred normally in Chk2−/− MEFs 1 hour after IR treatment"

Primary knockout fibroblast assays demonstrate preservation of this checkpoint under the tested conditions.

Increased CDC25A Abundance

Mechanism confidence: Provisional

Cdc25A protein abundance is elevated in heterozygous and more strongly in homozygous Chk2*1100delC mouse embryonic fibroblasts; increased staining is also observed in mammary tumors. The proposed mechanism involves impaired phosphorylation-dependent degradation. This experiment measured abundance, not CDC25A rescue of cancer susceptibility.

Experimental models

Chk2 1100delC mouse embryonic fibroblasts PRIMARY CELL CULTURE Measures increased Cdc25A protein.

Downstream

Model-Specific Genomic Instability Increased CDC25A is proposed to contribute to cell-cycle dysregulation and instability in this knock-in model; causal mediation was not isolated.

Show evidence (1 reference)

PMID:19805189 SUPPORT DIRECT PRIMARY RESULT In Vitro

"the levels of Cdc25A protein in the heterozygous cells are elevated compared with those in the wild-type cells and are even higher in the homozygous mutant cells."

Western blotting of mouse embryonic fibroblasts directly supports genotype-associated abundance changes.

Reduced Damage-Induced Apoptosis

Mechanism confidence: Provisional

Irradiated Chk2-null thymocytes show reduced induction of proapoptotic p53 targets. Additional Mre11 hypomorphism markedly worsens apoptotic defects and produces tumor susceptibility. This supplies a context-dependent tumor-suppression mechanism rather than evidence for universal loss of p53 checkpoints in human CHEK2 carriers.

apoptotic process GO:0006915 ↓ DECREASED

Experimental models

Chk2-null mouse fibroblast and thymocyte assays PRIMARY CELL CULTURE Measures proapoptotic target induction after irradiation.

Downstream

Breast carcinoma Reduced elimination of damaged cells is a candidate contributor to tumor susceptibility; the tissue-specific intervening steps in human breast cancer remain unresolved.

Show evidence (2 references)

PMID:18614044 SUPPORT DIRECT PRIMARY RESULT In Vitro

"Whereas their induction was 30–50% of WT in Chk2−/−, Mre11ATLD1/ATLD1, and Atm−/− single mutants, Bbc3/Puma and Bax induction was similar to p53−/− in Mre11ATLD1/ATLD1 Chk2−/− double mutants"

Quantitative PCR after irradiation distinguishes single-mutant residual responses from the severe double-mutant defect.

PMID:18614044 SUPPORT DIRECT PRIMARY RESULT In Vitro

"The apoptotic defect in Mre11ATLD1/ATLD1 was markedly enhanced by Chk2 deficiency, as thymocytes from Mre11ATLD1/ATLD1 Chk2−/− were as defective as p53−/− thymocytes for IR-induced apoptosis"

The primary thymocyte assay measures the apoptotic endpoint directly in the compound-mutant context.

Model-Specific Genomic Instability

Mechanism confidence: Provisional

Chk2*1100delC knock-in fibroblasts accumulate in S/G2 and show persistent DNA-damage markers. Such allele-specific findings must be separated from homologous-recombination-deficiency signatures in human tumors: CHEK2-deficient human cancers generally lack those signatures, and Chk2-null splenocytes did not show excess chromosomal lesions in another study.

Experimental models

Chk2 1100delC mouse embryonic fibroblasts PRIMARY CELL CULTURE Measures persistent damage and altered cell-cycle distribution.

Downstream

Breast carcinoma Damage persistence may contribute to tumor initiation, but this cellular assay does not establish a universal human breast-cancer route.

Show evidence (2 references)

PMID:17174984 SUPPORT DIRECT PRIMARY RESULT In Vitro

"The mutant cells show signs of spontaneous genomic instability as indicated by polyploidy and an increase in DNA double strand breaks."

The original knock-in study directly measures instability in derived fibroblasts.

PMID:18614044 REFUTE DIRECT PRIMARY RESULT In Vitro

"Chk2−/− splenocytes did not show increased spontaneous or IR induced chromosomal lesions"

This negative result limits generalization from knock-in fibroblasts to every CHEK2-deficient cell.

✶

Histopathology

Invasive ductal carcinoma of no special type

In a selected series of 35 women with 44 invasive breast cancers, 38/44 tumors were IDC-NST. Lobular, mixed ductal/lobular and papillary cancers also occurred. Histology does not diagnose germline CHEK2 predisposition.

Show evidence (1 reference)

PMID:38091153 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"BCs were predominantly invasive ductal carcinomas of no special type (IDC-NST) (86%, 38/44)."

Tumor denominator in a selected pathology series; not carrier penetrance.

Estrogen receptor positivity

ER positivity was present in 41/43 evaluable tumors in the same series; 34/43 were ER-positive/HER2-negative and 7/43 ER-positive/HER2-positive. The selected series included no triple-negative tumors, which does not establish their impossibility in carriers.

Show evidence (1 reference)

PMID:38091153 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Nearly all BCs were ER + (95%, 41/43)"

The primary pathology result documents receptor positivity.

Luminal B immunohistochemical surrogate phenotype

Using immunohistochemical surrogates and a Ki67 cutpoint of 14%, 25/36 tumors were classified as luminal B. These are surrogate classifications from one selected series, not a universal molecular subtype for CHEK2-associated breast cancer.

Show evidence (1 reference)

PMID:38091153 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Using immunohistochemical surrogates for molecular subtyping, most (69%, 25/36) BCs were classified as luminal B"

The assay and denominator qualify the subtype claim.

Sparse tumor-infiltrating lymphocytes

Tumor-infiltrating lymphocytes occupied less than 10% in 34/38 evaluated tumors. The observation does not prove immune suppression as the cause of CHEK2-associated cancer or predict immunotherapy response.

Show evidence (1 reference)

PMID:38091153 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"TILs were sparse (< 10%) in most (89%, 34/38) cases"

The primary series records a microscopic observation.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

●

Phenotypes

Breast 3

Breast carcinoma HP:0003002

Show evidence (2 references)

PMID:40440438 SUPPORT DIRECT REVIEW SYNTHESIS Other

"CHEK2-related cancer predisposition is predominantly characterized by an increased risk of female breast cancer."

GeneReviews identifies the main clinical manifestation.

PMID:38091153 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Four patients had synchronous bilateral BCs (11%, 4/35) and seven had multifocal BC (20%, 7/35)."

The primary clinical series retains distinct patient and tumor denominators.

Context-specific annotations (1)

FEMALE Heterozygotes assessed in clinical risk guidance; allele and family history modify risk

GeneReviews gives an average lifetime breast cancer risk of approximately 20–30%, commonly varying within 15–40%; no single frequency band is assigned across all alleles.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"the average lifetime breast cancer risk for a ... heterozygote ... is approximately 20%-30%"

The March 2026 chapter summarizes approximate lifetime risk, not the frequency within a case series.

Contralateral breast carcinoma HP:0003002

Laterality: BILATERAL

Show evidence (2 references)

PMID:36623243 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Germline CHEK2 PV carriers had a 1.9-fold elevated risk of CBC overall (HR, 1.9; 95% CI, 1.1 to 3.3; P = .03)"

The full-text adjusted analysis supplies the CHEK2-specific estimate.

PMID:36623243 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"the CHEK2 p.Ile157Thr (c.470T>C) variant was not significantly associated with CBC risk"

The primary study does not support extrapolating the truncating-variant estimate to Ile157Thr.

Context-specific annotations (2)

FEMALE Premenopausal women with prior breast cancer and truncating CHEK2 pathogenic variants in CARRIERS

Estimated 13% ten-year cumulative incidence; subset uncertainty and treatment exposure matter.

Show evidence (1 reference)

PMID:36623243 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Among premenopausal women, the 10-year cumulative incidence of CBC was estimated to be 33% for BRCA1, 27% for BRCA2, and 13% for CHEK2 PV carriers with breast cancer"

The primary prospective cohort provides the ten-year premenopausal estimate.

FEMALE Postmenopausal women with prior breast cancer and truncating CHEK2 pathogenic variants in CARRIERS

Estimated 4% ten-year cumulative incidence; this must not be compared with a five-year population risk as if horizons matched.

Show evidence (1 reference)

PMID:36623243 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"The 10-year cumulative incidence of CBC among postmenopausal PV carriers was 12% for BRCA1, 9% for BRCA2, and 4% for CHEK2."

The source supplies a ten-year, menopause-specific estimate.

Male breast carcinoma HP:0003002

Show evidence (2 references)

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"A recent meta-analysis showed an increased risk for MBC for CHEK2 heterozygotes (OR 3.13, 95% CI 1.94–5.07)."

The meta-analysis estimate is relative risk evidence, not absolute penetrance.

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"There have been conflicting findings in male BC (MBC), most likely because many of the studies have been small and in populations where c.1100del is not prevalent."

The same guidance describes limits of the association evidence.

Context-specific annotations (1)

MALE

Sex-specific breast cancer association; absolute risk is substantially lower than in female carriers.

Genitourinary 2

Prostate cancer HP:0012125

Show evidence (2 references)

PMID:40440438 SUPPORT DIRECT REVIEW SYNTHESIS Other

"To a lesser extent there is an association with increased risk of prostate cancer."

Clinical synthesis recognizes the association.

PMID:41396600 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"prostate (OR, 1.62 [95% CI, 1.27-2.07]; OR, 1.78 [95% CI, 1.48-2.16], respectively)"

The 2025 study reports MyCode and UK Biobank estimates.

Testicular neoplasm HP:0010788

Show evidence (3 references)

PMID:30676620 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Unselected men with TGCTs were approximately 4 times more likely to carry germline loss-of-function CHEK2 variants compared with cancer-free individuals from the Exome Aggregation Consortium cohort"

Quantifies the enrichment of loss-of-function CHEK2 variants in testicular germ cell tumour cases.

PMID:30676620 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Individuals with the pathogenic CHEK2 loss-of-function variants developed TGCTs 6 years earlier than individuals with CHEK2 wild-type alleles"

Documents the earlier age at onset in carriers.

PMID:41396600 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"For some rarer cancers (male breast, testicular), the 2 cohorts were likely underpowered"

The newer genome-first analysis cannot confidently settle this rare-tumor association.

🧬

Genetic Associations

CHEK2

Gene: CHEK2 hgnc:16627 relationship_type: CAUSATIVE variant_origin: GERMLINE

Show evidence (3 references)

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"the average lifetime BC risk for a CHEK2 heterozygote is approximately 25%, absolute risks can range from 15% to 40%"

ACMG summarizes the wide distribution of breast cancer risk.

PMID:41396600 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"There were 469 765 individuals in the UKBB cohort and 167 050 individuals in MyCode."

The primary study defines the denominator for its genome-first ascertainment.

PMID:41396600 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Overall, there were 3232 case participants ... in UKBB and 3153 case participants ... in MyCode"

The full results give carrier counts for both biobanks under the same study-specific variant-classification rules.

Variants (4)

NM_007194.4:c.1100del p.(Thr367MetfsTer15) Pathogenic

Northern European founder frameshift that disrupts the kinase domain. ACMG cites an odds ratio of 2.66 (95% CI 2.27–3.11) for female breast cancer. This association does not imply that every carrier develops cancer.

Functional effects

loss of CHK2 kinase activity

Truncation disrupts kinase function; functional dosage and residual protein can vary by tissue and assay.

Show evidence (2 references)

PMID:33322746 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The first functional analysis revealed that c.1100delC completely abrogates CHK2 kinase activity"

Review synthesis of the founder-allele functional experiments.

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"reporting an odds ratio (OR) of 2.66 (95% CI 2.27–3.11)"

The risk estimate concerns c.1100del; the preceding counts in the review refer to carriers, not total study enrollment.

NM_007194.4:c.470T>C p.(Ile157Thr)

Common lower-penetrance FHA-domain missense allele. ACMG reports breast cancer OR 1.30 (95% CI 1.06–1.59), below actionability thresholds when considered alone. Laboratory classifications have varied; functional impairment and clinical actionability are distinct.

Functional effects

partial, assay-dependent impairment of CHK2 function

Purified recombinant protein retained approximately 40–50% of wild-type kinase activity at saturating ATP in a CDC25-peptide assay. This result does not establish equivalent impairment of every substrate in vivo.

Show evidence (2 references)

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"p.(Ile157Thr) (OR 1.30, 95% CI 1.06–1.59; P = .01)"

This is the variant-specific estimate; OR 1.42 for a different rare-missense aggregate must not be assigned to this allele.

PMID:38367672 SUPPORT DIRECT PRIMARY RESULT In Vitro

"At saturating ATP, the CHK2 p.I157T and p.E321A variants presented 40 to 50% of the WT CHK2 enzymatic activity"

The purified-protein CDC25-peptide assay measures residual function, not patient cancer risk.

NM_007194.4:c.1283C>T p.(Ser428Phe)

Common missense allele with lower or uncertain clinical impact in isolation. The ACMG review cites OR 1.26 (95% CI 0.76–2.12), which was not statistically significant in that study; surveillance should reflect the full risk assessment.

Show evidence (1 reference)

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"p.(Ser428Phe) (OR 1.26, 95% CI 0.76–2.12; P = .37)"

The variant-specific confidence interval includes no association.

NM_007194.4:c.349A>G p.(Arg117Gly)

A missense variant with breast cancer risk estimates closer to truncating alleles: OR 2.26 (95% CI 1.29–3.95) and 2.69 (95% CI 1.46–4.94) in studies summarized by ACMG. Not all missense alleles belong in a uniformly low-risk class.

Show evidence (1 reference)

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The study reported an association of p.(Arg117Gly) with BC (OR 2.26, 95% CI 1.29–3.95)."

A variant-specific association distinguishes Arg117Gly from common lower-risk missense alleles.

💊

Medical Actions

Breast cancer surveillance

Action: cancer screening Ontology label: Cancer Screening NCIT:C15406

Annual mammography typically begins at age 40. The March 2026 GeneReviews chapter summarizes US guidance to consider annual MRI at age 30–35 in those with additional risk factors and according to preferences; UK recommendations use individualized CanRisk thresholds. Lower-risk missense variants require a family-history-based assessment. Predicted mortality benefit from MRI comes from modeling, not a randomized CHEK2 screening trial. The models assumed complete screening participation and guideline-concordant cancer therapy and projected false-positive examinations and benign biopsies as well as benefit.

Mechanism Target:

Breast carcinoma — Surveillance does not modify the mechanism; it detects the tumour phenotype earlier.

Show evidence (4 references)

PMID:40440438 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Breast cancer surveillance in females typically includes breast self-exam training and symptom awareness; mammogram every 12 months beginning at age 40 years; breast MRI recommendations vary by location."

Specifies the surveillance protocol.

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"early cancer detection and prevention for CHEK2 heterozygotes should be guided by personalized risk estimates"

Establishes that surveillance intensity is set by personalised risk rather than by carrier status.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"Consider annually from age 30-35 yrs in those w/strong family history, other risk factors"

The full surveillance table gives a qualified US MRI recommendation.

+ 1 more reference

Prostate cancer surveillance

Action: cancer screening Ontology label: Cancer Screening NCIT:C15406

Annual serum PSA may be considered from age 40, particularly with a strong family history of prostate cancer.

Show evidence (1 reference)

PMID:40440438 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Prostate cancer surveillance in males includes serum PSA to be considered annually beginning at age 40 years especially in those with a strong family history of prostate cancer."

Specifies the prostate surveillance recommendation.

Risk-reducing mastectomy

Action: Prophylactic Mastectomy NCIT:C94445

Platform: Surgery

Bilateral or contralateral risk-reducing mastectomy is not routine solely for CHEK2 heterozygosity. Consider personal and family history, age, estimated lifetime or contralateral risk, competing risks and patient preferences. Surveillance remains an option; a moderate relative risk alone does not establish survival benefit from surgery.

Show evidence (2 references)

PMID:40440438 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Breast cancer risk-reducing contralateral mastectomy is generally not recommended but may be considered in some situations."

States that this intervention is not routine, which is the clinically important negative.

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Risk-reducing mastectomy should be guided by personalized risk estimates and shared decision making."

The ACMG resource frames the decision as risk-estimate driven rather than genotype driven.

Cancer-directed treatment

Action: Therapeutic Procedure NCIT:C49236

Treat established cancer according to site, stage, histology and validated tumor biomarkers. CHEK2 carrier status alone does not establish a broadly effective targeted treatment. In a selected breast pathology series, all evaluable neoadjuvant cases showed tumor-size and Ki67 reductions, but only 3 of 14 treated patients achieved pathologic complete response; two complete responders had HER2-positive tumors. This uncontrolled, largely ER-positive series cannot establish universal chemoresistance.

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"there is insufficient evidence to recommend specific cancer treatment based on identification of ... related cancer predisposition. Standard cancer treatments are recommended."

GeneReviews does not identify a broadly effective CHEK2-predisposition-specific treatment.

PMID:38091153 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Although decreased post-treatment tumor size and Ki67 proliferative index reflected treatment effect in all evaluable cases, only three patients in our series achieved pCR."

The primary treatment observations show activity and limited complete responses, not complete lack of chemotherapy sensitivity.

Genetic counseling and cascade testing

Action: Genetic Counseling NCIT:C15240

Offer targeted familial-variant testing to at-risk adult relatives with counseling about variant-specific, incomplete penetrance. Each child of a heterozygote has a 50% transmission risk. A relative who tests negative may retain risk from other family-history factors. Routine predictive testing in childhood is generally not offered because the established management is directed at adult risk.

Show evidence (2 references)

PMID:40440438 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Molecular genetic testing of at-risk female and male adult relatives can identify those family members who also have the familial pathogenic variant and thus may benefit from increased cancer surveillance."

States the cascade testing rationale.

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"Predictive genetic testing for a familial CHEK2 variant is not routinely recommended in childhood."

The ACMG practice resource limits routine predictive testing in minors.

Colorectal screening according to personal and family history

Action: Cancer Screening NCIT:C15406

CHEK2 heterozygosity alone does not currently justify intensified colonoscopy. Use general-population colorectal screening unless personal history, polyps or family history independently indicate more intensive surveillance. This reflects the 2024 NCCN change summarized in the March 2026 GeneReviews chapter, despite discordant epidemiologic association reports.

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"NCCN recommends general population screening for CRC in those w/ ... CHEK2 ... cancer predisposition."

The clinical chapter explicitly states current population screening guidance for CHEK2 predisposition.

DOI:10.6004/jnccn.2024.0061 SUPPORT DIRECT REVIEW SYNTHESIS Other

"de-implementation of colon cancer screening in individuals with CHEK2 pathogenic/likely pathogenic variants"

The guideline update concerns de-implementation of CHEK2-specific intensified screening, not abandonment of ordinary colorectal screening.

Olaparib under tumor-specific indications or trials

Action: Olaparib treatment Ontology label: Pharmacotherapy NCIT:C15986

Agent: olaparib CHEBI:83766

Platform: Small molecule

CHEK2 alteration is not a reliable general predictor of PARP-inhibitor benefit. In TBCRC 048 metastatic breast cancer, no responses were observed with CHEK2 mutations alone. Separately, the US olaparib label includes qualifying CHEK2 alterations among HRR-gene-mutated metastatic castration-resistant prostate cancers after progression on enzalutamide or abiraterone, with approved companion-diagnostic selection. Regulatory eligibility for that specific indication does not establish CHEK2-specific efficacy or imply eligibility for breast cancer solely on CHEK2 status.

Show evidence (4 references)

PMID:33119476 REFUTE DIRECT PRIMARY RESULT Human Clinical

"No responses were observed with ATM or CHEK2 mutations alone."

The phase II breast-cancer trial refutes efficacy inferred from CHEK2 alteration alone in that study population.

url:https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/208558s031lbl.pdf SUPPORT DIRECT REVIEW SYNTHESIS Other

"cancer (mCRPC) who have progressed following prior treatment with enzalutamide or abiraterone."

The FDA label defines the preceding-treatment setting; its biomarker-selection table explicitly lists CHEK2 among eligible HRR genes.

url:https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/208558s031lbl.pdf SUPPORT DIRECT REVIEW SYNTHESIS Other

"Germline or somatic HRR gene-mutated metastatic castration-resistant prostate cancer ATMm, BRCA1m, BRCA2m, BARD1m, BRIP1m, CDK12m, CHEK1m, CHEK2m, FANCLm, PALB2m, RAD51Bm, RAD51Cm, RAD51Dm, RAD54Lm"

The label’s biomarker-selection table explicitly includes CHEK2 for this prostate-cancer indication.

+ 1 more reference

Ovarian risk management

Platform: Surgery

Risk-reducing salpingo-oophorectomy is not recommended solely on the basis of CHEK2 heterozygosity. Any indication should arise from another established risk factor or diagnosis.

Show evidence (1 reference)

PMID:37490054 SUPPORT DIRECT REVIEW SYNTHESIS Other

"There is no evidence for an increased risk for ovarian cancer in CHEK2 heterozygotes."

The ACMG resource does not support CHEK2-heterozygosity-specific ovarian risk reduction.

🔬

Diagnosis

Germline molecular diagnosis

Identify a pathogenic or likely pathogenic germline CHEK2 variant with a validated assay, usually a hereditary cancer multigene panel. A variant of uncertain significance is nondiagnostic. Some historically pathogenic common missense variants have lower penetrance and require variant-specific interpretation.

Show evidence (2 references)

PMID:40440438 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The diagnosis of CHEK2-related cancer predisposition is established in a proband with a heterozygous germline pathogenic variant in CHEK2 identified by molecular genetic testing."

GeneReviews states the germline diagnostic basis.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"uncertain significance ... does not establish or rule out the diagnosis."

A VUS is not a diagnostic or predictive family-test result.

Sequencing and deletion/duplication assessment

Testing should cover small sequence variants and validated copy-number analysis; sequencing alone may miss exon or whole-gene deletions. CHEK2 pseudogene homology can complicate assay design. Exome or genome data do not automatically guarantee equivalent deletion/duplication sensitivity.

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"multiexon, or whole-gene deletions/duplications may not be detected."

GeneReviews notes the limitation of some sequencing methods.

PMID:33322746 SUPPORT DIRECT REVIEW SYNTHESIS Other

"The 3′ portion of the CHEK2 gene comprising exons 10–14 is duplicated with >90% homology in the human genome"

The review identifies a locus-specific technical testing issue.

Constitutional versus acquired variant assessment

A CHEK2 alteration found in tumor or blood is not automatically inherited. Clonal hematopoiesis can produce acquired blood variants, sometimes at apparently heterozygous allele fractions. When the clinical context raises doubt, testing appropriate non-hematopoietic tissue helps distinguish a constitutional variant from an acquired hematopoietic clone.

Show evidence (2 references)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"Variants at ... frequencies in the heterozygous range may also be acquired"

The full chapter explicitly cautions that allele fraction alone does not establish germline origin.

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"further testing of different tissues to determine if a pathogenic variant is ... constitutional ... or somatic should be guided by clinical evaluation"

Clinical interpretation and tissue comparison guide origin assessment.

🔀

Differential Diagnoses

Conditions with similar clinical presentations that must be differentiated from CHEK2-related Cancer Predisposition:

Other hereditary breast cancer predispositions

Overlapping Features BRCA1/2, PALB2, ATM and syndromic predispositions including TP53, PTEN, CDH1 and STK11 can overlap clinically.

Distinguishing Features

The combination of tumor types and ages does not reliably distinguish CHEK2 from other inherited cancer predispositions.
Molecular testing and syndrome-specific features determine the appropriate diagnosis and surveillance.

Show evidence (1 reference)

url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"It is not possible to distinguish ... related cancer predisposition from these other cancer susceptibility syndromes based solely on the constellation of tumors and ages of cancer onset present in the family."

GeneReviews supports molecular differentiation when clinical cancer patterns overlap.

🔬

Clinical Trials

NCT05011383 PHASE_II RECRUITING

Intermittent high-dose testosterone in ATM-, CDK12- or CHEK2-altered prostate cancer. The protocol tests a predictive hypothesis and does not establish CHEK2-specific response.

Show evidence (1 reference)

clinicaltrials:NCT05011383 SUPPORT DIRECT Other

"the genes ATM, CDK12 or CHEK2 predicts for a high likelihood of responding to the use of intermittent high dose testosterone."

The registered protocol supports the intervention and study purpose; it is not an efficacy result.

NCT05033756 PHASE_II ACTIVE_NOT_RECRUITING

COMPRENDO evaluates pembrolizumab plus olaparib in advanced HER2-negative breast cancer. The second cohort includes germline CHEK2 and other moderate-penetrance repair genes. No CHEK2-specific benefit can be inferred from enrollment.

Show evidence (1 reference)

clinicaltrials:NCT05033756 SUPPORT DIRECT Other

"This study will examine the combination of pembrolizumab and olaparib in three populations."

The registered protocol supports the intervention and study purpose; it is not an efficacy result.

NCT02401347 PHASE_II COMPLETED

Talazoparib beyond germline BRCA1/2 in advanced breast or other solid tumors with qualifying pathway alterations. CHEK2 appears among eligible genes in the registry criteria. Completion alone does not demonstrate efficacy in CHEK2 carriers.

Show evidence (1 reference)

clinicaltrials:NCT02401347 SUPPORT DIRECT Other

"The aim of this single-arm phase 2 clinical trial is to evaluate the anti-cancer activity of Talazoparib"

The registered protocol supports the intervention and study purpose; it is not an efficacy result.

NCT03786796 PHASE_II RECRUITING

ORCHID evaluates olaparib in metastatic renal-cell carcinoma with qualifying DNA-repair alterations, including CHEK2, after prior anti-VEGF or immune-checkpoint therapy. This is a basket eligibility criterion, not a germline CHEK2-specific regimen.

Show evidence (1 reference)

clinicaltrials:NCT03786796 SUPPORT DIRECT Other

"participants with metastatic renal cell carcinoma that harbor an inactivating mutation in BAP-1, ATM, BRCA1, BRCA2, PALB2, CHEK2"

The registered protocol supports the intervention and study purpose; it is not an efficacy result.

NCT06033092 PHASE_II COMPLETED

Low-dose tamoxifen and lifestyle interventions in women at increased breast cancer risk, including eligible germline CHEK2 carriers. The primary six-month endpoint is circulating SHBG, a biomarker; it does not directly establish reduced CHEK2-associated cancer incidence.

Show evidence (1 reference)

clinicaltrials:NCT06033092 SUPPORT DIRECT Other

"verify whether Low Dose Tamoxifen (LDT) increases circulating levels of SHBG more than lifestyle intervention"

The registered protocol supports the intervention and study purpose; it is not an efficacy result.

NCT03344965 PHASE_II ACTIVE_NOT_RECRUITING

TBCRC 048 / Olaparib Expanded examines olaparib in metastatic breast cancer with qualifying germline or somatic DNA-repair variants. The published initial cohort found no responses with CHEK2 mutations alone; overall trial results must not be assigned to each gene subgroup.

Show evidence (1 reference)

clinicaltrials:NCT03344965 SUPPORT DIRECT Other

"This study will evaluate whether olaparib is effective in breast cancer patients whose tumor has a mutation in one of the other genes that function with BRCA1 and BRCA2 to repair damaged DNA"

The registered protocol supports the intervention and study purpose; it is not an efficacy result.

🧫

Experimental Models

Chk2 1100delC mouse embryonic fibroblasts PRIMARY_CELL_CULTURE

Fibroblasts from wild-type, heterozygous and homozygous knock-in mice provide protein and cell-cycle readouts. The original 2007 report supplies the instability assays; the 2009 follow-up supplies CDC25A measurements.

Publication

PMID:19805189

Pathograph links

Increased CDC25A Abundance partially recapitulates fidelity: moderate observes: molecular Measures increased Cdc25A protein.

Limitations: Protein abundance is not a rescue test of causal mediation in cancer.

Show evidence (1 reference)

PMID:19805189 SUPPORT DIRECT PRIMARY RESULT In Vitro

"the levels of Cdc25A protein in the heterozygous cells are elevated compared with those in the wild-type cells and are even higher in the homozygous mutant cells."

Western blotting of mouse embryonic fibroblasts directly supports genotype-associated abundance changes.

Model-Specific Genomic Instability partially recapitulates fidelity: moderate observes: cellular Measures persistent damage and altered cell-cycle distribution.

Limitations: Model-specific cellular findings do not establish BRCA-like HRD in human tumors.

Show evidence (1 reference)

PMID:17174984 SUPPORT DIRECT PRIMARY RESULT In Vitro

"The mutant cells show signs of spontaneous genomic instability as indicated by polyploidy and an increase in DNA double strand breaks."

The original knock-in study directly measures instability in derived fibroblasts.

Chk2-null mouse fibroblast and thymocyte assays PRIMARY_CELL_CULTURE

Irradiated fibroblasts and thymocytes distinguish checkpoint preservation from reduced apoptotic signaling and test interaction with Mre11-complex hypomorphism.

Publication

PMID:18614044

Pathograph links

Attenuated CHK2 Damage Response Signaling measures fidelity: moderate observes: cellular Tests the remaining G2/M checkpoint response after Chk2 deletion.

Limitations: G2/M arrest remained intact under these conditions despite other CHK2-dependent defects.

Show evidence (1 reference)

PMID:18614044 SUPPORT DIRECT PRIMARY RESULT In Vitro

Primary knockout fibroblast assays demonstrate preservation of this checkpoint under the tested conditions.

Reduced Damage-Induced Apoptosis partially recapitulates fidelity: moderate observes: cellular Measures proapoptotic target induction after irradiation.

Limitations: The strongest defect occurs in compound-mutant thymocytes, not a human heterozygote.

Show evidence (1 reference)

PMID:18614044 SUPPORT DIRECT PRIMARY RESULT In Vitro

Quantitative PCR after irradiation distinguishes single-mutant residual responses from the severe double-mutant defect.

Recombinant CHK2 p.Ile157Thr biochemical assay OTHER

Purified truncated recombinant CHK2 proteins were tested with a CDC25-derived peptide and varying ATP concentrations. Ile157Thr retained partial activity and had altered conformational stability. Heat-induced amyloid-like aggregation in vitro was not detected as amyloid deposition in the examined thyroid tissues.

Publication

PMID:38367672

Pathograph links

Germline CHEK2 Loss of Function measures fidelity: moderate observes: molecular Measures partial missense dysfunction in a defined biochemical system.

Limitations: A purified, truncated-protein assay cannot quantify cellular function, thyroid-cancer penetrance or clinical actionability.

Show evidence (1 reference)

PMID:38367672 SUPPORT DIRECT PRIMARY RESULT In Vitro

"At saturating ATP, the CHK2 p.I157T and p.E321A variants presented 40 to 50% of the WT CHK2 enzymatic activity"

Direct enzyme assay of residual activity.

Show evidence (1 reference)

PMID:38367672 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"amyloid deposition was undetected in both normal and tumor tissues"

The tissue analysis limits translation of the in-vitro aggregation observation.

🐁

Animal Models

Chk2 1100delC knock-in mouse

Spontaneous tumors were followed for up to 24 months. Homozygotes showed a significant overall increase; the heterozygote comparison was not significant in the pooled-sex analysis. Female-biased effects and varied tumor types limit direct transfer to human breast risk. In a separate DMBA challenge, mammary tumor latency decreased in homozygotes but not heterozygotes; all exposed genotype groups had shortened survival.

Species

Mus musculus

Genotype

Chek2*1100delC heterozygotes and homozygotes; backcrossed at least five generations to FVB

Publication

PMID:19805189

Pathograph links

Germline CHEK2 Loss of Function perturbs fidelity: moderate observes: molecular Introduces the founder-equivalent truncating allele.

Limitations: Species, genetic background, sex and genotype alter tumor outcomes; pooled heterozygote tumor incidence was not significantly elevated.

Show evidence (1 reference)

PMID:19805189 SUPPORT DIRECT PRIMARY RESULT Model Organism

"mice heterozygous and homozygous for Chk2*1100delC and their wild-type counterparts were maintained for up to 2 years"

The germline knock-in comparison tests allele dosage.

Show evidence (1 reference)

PMID:19805189 SUPPORT DIRECT PRIMARY RESULT Model Organism

"The difference between heterozygous and wild-type mice is not statistically significant (P = 0.127) but shows a developing trend by 24 months."

The full-text result qualifies the abstract-level statement of cancer predisposition.

Chk2-null and Mre11-complex compound-mutant mice

Single-mutant mice were not predisposed to malignancy in this experiment, whereas roughly 40% of the compound-mutant cohorts developed malignancy within two years. Distinct effects of null and knock-in alleles caution against treating all model genotypes as interchangeable.

Species

Mus musculus

Genotype

Chk2−/− alone or with Nbs1ΔB/ΔB or Mre11ATLD1/ATLD1

Publication

PMID:18614044

Pathograph links

Germline CHEK2 Loss of Function perturbs fidelity: moderate observes: molecular Deletes Chk2 with or without an additional damage-response defect.

Limitations: Tumor predisposition in compound mutants cannot be attributed to heterozygous CHEK2 loss alone.

Show evidence (1 reference)

PMID:18614044 SUPPORT DIRECT PRIMARY RESULT Model Organism

"we generated Nbs1ΔB/ΔB Chk2−/− and Mre11ATLD1/ATLD1 Chk2−/− mice."

The experimental design separates single and compound genotypes.

Show evidence (1 reference)

PMID:18614044 SUPPORT DIRECT PRIMARY RESULT Model Organism

"roughly 40% of each cohort succumbing to malignancy within 2 years"

The tumor result concerns compound mutants, not isolated Chk2 loss.

{ }

Source YAML

click to show

name: CHEK2-related Cancer Predisposition
creation_date: "2026-09-02T00:00:00Z"
description: >-
  CHEK2-related cancer predisposition is an autosomal dominant susceptibility associated with germline pathogenic variants in the checkpoint kinase gene CHEK2. Female breast cancer is the best-established manifestation, with increased contralateral breast and prostate cancer risks and a smaller absolute male breast cancer risk. Penetrance varies with the allele, age, sex, family history and other modifiers. Common lower-risk missense variants, including p.Ile157Thr, require different risk interpretation from truncating variants. CHK2 participates in DNA-damage signaling, but checkpoint defects are context dependent and CHEK2-associated tumors generally lack the BRCA-like homologous-recombination-deficiency profile. Somatic second hits occur in a subset of tumors; neither their presence nor their absence defines every carrier-associated cancer. Clinical management uses individualized surveillance and cancer-specific treatment. CHEK2 does not cause Li-Fraumeni syndrome.
category: Mendelian
synonyms:
- CHEK2-associated cancer predisposition
- CHEK2 cancer susceptibility
- CHK2 checkpoint kinase deficiency
disease_term:
  preferred_term: CHEK2-related cancer predisposition
  term:
    id: MONDO:0700271
    label: CHEK2-related cancer predisposition
inheritance:
- name: Autosomal dominant
  inheritance_term:
    preferred_term: Autosomal dominant inheritance
    term:
      id: HP:0000006
      label: Autosomal dominant inheritance
  description: >-
    Most individuals have a heterozygous germline pathogenic variant. A transmitting parent may or may not have developed cancer; transmission is 50% for each child of a heterozygote. Rare biallelic genotypes have a broader and variant-dependent cancer phenotype.
  evidence:
  - reference: PMID:40440438
    reference_title: "CHEK2-Related Cancer Predisposition."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Most individuals with CHEK2-related cancer predisposition have a heterozygous pathogenic variant. Rarely, affected individuals have biallelic pathogenic variants."
    explanation: GeneReviews statement of the inheritance pattern and the rarity of biallelic disease.
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
  - reference: PMID:40440438
    reference_title: "CHEK2-Related Cancer Predisposition."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The vast majority of individuals with a heterozygous germline CHEK2 pathogenic variant inherited the pathogenic variant from a parent who may or may not have had a cancer diagnosis."
    explanation: Most variants are inherited, but the source does not establish that most transmitting parents are cancer-free.
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
  - reference: PMID:40440438
    reference_title: "CHEK2-Related Cancer Predisposition."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "The offspring of an individual identified as having a heterozygous germline CHEK2 pathogenic variant have a 50% chance of inheriting the pathogenic variant."
    explanation: The transmission risk quoted to families in genetic counselling.
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
pathophysiology:
- name: Germline CHEK2 Loss of Function
  description: Truncating, splice-disrupting and deletion alleles can reduce functional CHK2 dosage or kinase activity. The c.1100del founder frameshift is a well-studied loss-of-function allele. Missense effects range from severe loss to partial, assay-dependent dysfunction; biochemical impairment does not by itself establish clinically actionable penetrance.
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:33322746
    reference_title: 'CHEK2 Germline Variants in Cancer Predisposition: Stalemate Rather than Checkmate.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: The first functional analysis revealed that c.1100delC completely abrogates CHK2 kinase activity
    explanation: Review synthesis of functional work on the truncating founder allele.
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: there is evidence that the common variant p.(Ile157Thr) adversely affects protein function and is therefore “deleterious;” yet, its penetrance is low and in isolation not at a level of clinical actionability
    explanation: Separates functional impairment from cancer penetrance and clinical actionability.
  gene:
    preferred_term: CHEK2
    term:
      id: hgnc:16627
      label: CHEK2
  molecular_functions:
  - preferred_term: protein serine/threonine kinase activity
    term:
      id: GO:0004674
      label: protein serine/threonine kinase activity
    modifier: DECREASED
  genetic_context:
    gene:
      preferred_term: CHEK2
      term:
        id: hgnc:16627
        label: CHEK2
    variant_origin: GERMLINE
    functional_impact_category: LOSS_OF_FUNCTION
  downstream:
  - target: Attenuated CHK2 Damage Response Signaling
    description: Reduced functional CHK2 impairs its contribution to DNA-damage signaling.
    causal_link_type: DIRECT
- name: Somatic CHEK2 Second-Hit Alteration
  description: Somatic loss of the remaining CHEK2 allele is observed in some carrier-associated breast tumors. A selected pathology series found biallelic alteration with loss of heterozygosity in 13 of 23 sequenced cancers. This is a tumor observation, not evidence that all carrier tumors are CHEK2-null or that reduced checkpoint signaling directly causes allele loss.
  biological_scale: MOLECULAR
  mechanism_confidence: ESTABLISHED
  evidence:
  - reference: PMID:38091153
    reference_title: Clinicopathologic and genetic analysis of invasive breast carcinomas in women with germline CHEK2 variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Biallelic CHEK2 alteration with loss of heterozygosity was identified in most BCs (57%, 13/23) by NGS.
    explanation: The selected tumor series directly documents second-hit events; germline and somatic findings must be distinguished.
  genetic_context:
    gene:
      preferred_term: CHEK2
      term:
        id: hgnc:16627
        label: CHEK2
    variant_origin: SOMATIC
    functional_impact_category: LOSS_OF_FUNCTION
    description: Acquired loss of the remaining allele in a subset of germline-variant-associated breast cancers.
  downstream:
  - target: Attenuated CHK2 Damage Response Signaling
    description: A second hit can further reduce CHK2 signaling in the affected tumor; the degree of functional loss depends on the alleles.
    causal_link_type: DIRECT
- name: Attenuated CHK2 Damage Response Signaling
  description: Activated ATM can phosphorylate CHK2, which regulates multiple downstream effectors of arrest and apoptosis. CHEK2 deficiency reduces this signaling contribution without necessarily abolishing p53 activation, S-phase arrest or G2/M arrest. Model, allele, cell type and DNA-damage stimulus determine the observed defect.
  biological_scale: MOLECULAR
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:33322746
    reference_title: 'CHEK2 Germline Variants in Cancer Predisposition: Stalemate Rather than Checkmate.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: ATM phosphorylates CHK2 and other proteins orchestrating DDSB repair and DDR. CHK2 overlaps some ATM targets, amplifies an ATM-triggered signal, and increases the DDR regulation fidelity.
    explanation: The review places CHK2 within a partially redundant damage-response network.
  - reference: PMID:18614044
    reference_title: Chk2 suppresses the oncogenic potential of DNA replication-associated DNA damage.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Inhibition of the G2/M transition following DNA damage (the G2/M checkpoint), which is defective in Nbs1ΔB/ΔB and Mre11ATLD1/ATLD1 cultures, occurred normally in Chk2−/− MEFs 1 hour after IR treatment
    explanation: Primary knockout fibroblast assays demonstrate preservation of this checkpoint under the tested conditions.
  biological_processes:
  - preferred_term: DNA damage checkpoint signaling
    term:
      id: GO:0000077
      label: DNA damage checkpoint signaling
    modifier: DECREASED
  downstream:
  - target: Increased CDC25A Abundance
    description: Reduced CHK2-dependent regulation of CDC25A turnover is a candidate route to higher protein abundance in the 1100delC model.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Reduced phosphorylation-dependent CDC25A degradation
  - target: Reduced Damage-Induced Apoptosis
    description: Loss of CHK2 reduces selected p53-dependent proapoptotic responses; parallel ATM/MRE11 activity modifies severity.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - Reduced induction of proapoptotic p53 targets
- name: Increased CDC25A Abundance
  description: Cdc25A protein abundance is elevated in heterozygous and more strongly in homozygous Chk2*1100delC mouse embryonic fibroblasts; increased staining is also observed in mammary tumors. The proposed mechanism involves impaired phosphorylation-dependent degradation. This experiment measured abundance, not CDC25A rescue of cancer susceptibility.
  biological_scale: MOLECULAR
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:19805189
    reference_title: Mice with the CHEK2*1100delC SNP are predisposed to cancer with a strong gender bias.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: the levels of Cdc25A protein in the heterozygous cells are elevated compared with those in the wild-type cells and are even higher in the homozygous mutant cells.
    explanation: Western blotting of mouse embryonic fibroblasts directly supports genotype-associated abundance changes.
  downstream:
  - target: Model-Specific Genomic Instability
    description: Increased CDC25A is proposed to contribute to cell-cycle dysregulation and instability in this knock-in model; causal mediation was not isolated.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
- name: Reduced Damage-Induced Apoptosis
  description: Irradiated Chk2-null thymocytes show reduced induction of proapoptotic p53 targets. Additional Mre11 hypomorphism markedly worsens apoptotic defects and produces tumor susceptibility. This supplies a context-dependent tumor-suppression mechanism rather than evidence for universal loss of p53 checkpoints in human CHEK2 carriers.
  biological_scale: CELLULAR
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:18614044
    reference_title: Chk2 suppresses the oncogenic potential of DNA replication-associated DNA damage.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Whereas their induction was 30–50% of WT in Chk2−/−, Mre11ATLD1/ATLD1, and Atm−/− single mutants, Bbc3/Puma and Bax induction was similar to p53−/− in Mre11ATLD1/ATLD1 Chk2−/− double mutants
    explanation: Quantitative PCR after irradiation distinguishes single-mutant residual responses from the severe double-mutant defect.
  - reference: PMID:18614044
    reference_title: Chk2 suppresses the oncogenic potential of DNA replication-associated DNA damage.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: The apoptotic defect in Mre11ATLD1/ATLD1 was markedly enhanced by Chk2 deficiency, as thymocytes from Mre11ATLD1/ATLD1 Chk2−/− were as defective as p53−/− thymocytes for IR-induced apoptosis
    explanation: The primary thymocyte assay measures the apoptotic endpoint directly in the compound-mutant context.
  biological_processes:
  - preferred_term: apoptotic process
    term:
      id: GO:0006915
      label: apoptotic process
    modifier: DECREASED
  downstream:
  - target: Breast carcinoma
    description: Reduced elimination of damaged cells is a candidate contributor to tumor susceptibility; the tissue-specific intervening steps in human breast cancer remain unresolved.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
- name: Model-Specific Genomic Instability
  description: 'Chk2*1100delC knock-in fibroblasts accumulate in S/G2 and show persistent DNA-damage markers. Such allele-specific findings must be separated from homologous-recombination-deficiency signatures in human tumors: CHEK2-deficient human cancers generally lack those signatures, and Chk2-null splenocytes did not show excess chromosomal lesions in another study.'
  biological_scale: CELLULAR
  mechanism_confidence: PROVISIONAL
  evidence:
  - reference: PMID:17174984
    reference_title: The breast cancer susceptibility allele CHEK2*1100delC promotes genomic instability in a knock-in mouse model.
    supports: SUPPORT
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: The mutant cells show signs of spontaneous genomic instability as indicated by polyploidy and an increase in DNA double strand breaks.
    explanation: The original knock-in study directly measures instability in derived fibroblasts.
  - reference: PMID:18614044
    reference_title: Chk2 suppresses the oncogenic potential of DNA replication-associated DNA damage.
    supports: REFUTE
    evidence_source: IN_VITRO
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Chk2−/− splenocytes did not show increased spontaneous or IR induced chromosomal lesions
    explanation: This negative result limits generalization from knock-in fibroblasts to every CHEK2-deficient cell.
  downstream:
  - target: Breast carcinoma
    description: Damage persistence may contribute to tumor initiation, but this cellular assay does not establish a universal human breast-cancer route.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
discussions:
- discussion_id: chek2_oncogenic_route_unknown
  kind: KNOWLEDGE_GAP
  attaches_to:
  - pathophysiology#Attenuated CHK2 Damage Response Signaling
  - pathophysiology#Somatic CHEK2 Second-Hit Alteration
  prompt: Which CHK2-dependent processes mediate human tumor susceptibility?
  rationale: Checkpoint and apoptotic effects differ across models. Second hits are not universal, and genomic analyses distinguish CHEK2 deficiency from BRCA1/2 deficiency. In 16 breast and non-breast tumors from nine c.1100del homozygotes, no sample reached the study LST threshold for homologous-recombination deficiency; SBS3 contributed to two tumors but was not the dominant pattern. These data constrain a BRCA-like mechanism without excluding all DNA-repair functions.
  evidence:
  - reference: PMID:38848470
    reference_title: The genomic landscape of breast and non-breast cancers from individuals with germline CHEK2 deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: None of the analyzed cancers presented with an LST count of 15 or more, which is considered the cutoff value for HRD.
    explanation: Direct genomic analysis of 16 tumors from nine germline c.1100del homozygotes.
  - reference: PMID:38848470
    reference_title: The genomic landscape of breast and non-breast cancers from individuals with germline CHEK2 deficiency.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: SBS3, the HRD-related mutational signature (17), was observed to some level in 13% (2/16) of CHEK2-deficient cancers
    explanation: The minority SBS3 signal prevents an absolute claim that this signature never occurs.
- discussion_id: chek2_not_li_fraumeni
  kind: CONTROVERSY
  status: RESOLVED
  attaches_to:
  - disease#
  prompt: Is CHEK2 a Li-Fraumeni syndrome gene?
  rationale: The historical association has been refuted. CHEK2 predisposition should not be assigned TP53-related Li-Fraumeni surveillance solely on that historical claim.
  evidence:
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: REFUTE
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: a large body of evidence has conclusively shown that variants in CHEK2 are not associated with Li-Fraumeni syndrome
    explanation: The ACMG review refutes the historical gene-disease claim.
- discussion_id: chek2_risk_is_a_distribution
  kind: KNOWLEDGE_GAP
  attaches_to:
  - disease#
  prompt: How should variant-specific risk and other modifiers be combined?
  rationale: Absolute risk depends on genotype, age, sex, family history and other genetic and non-genetic factors. Population biobanks and cancer clinics sample different risk distributions. Polygenic risk estimates have predominantly European-ancestry validation, limiting transfer to other populations.
  evidence:
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Although CHEK2 is considered a moderate penetrance gene, cancer risks may be considered as a continuous variable, which are influenced by family history and other modifiers.
    explanation: Clinical guidance supports individualized rather than uniform lifetime risk.
  - reference: PMID:41396600
    reference_title: Genomic Ascertainment of CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Participants in MyCode and UKBB are predominantly of European ancestry. Copy-number variants in CHEK2 were not evaluated due to limited data availability in UKBB.
    explanation: Population and assay limitations constrain the new genome-first cohort results.
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: the genome-wide association studies used to identify PRS lacked diversity and are predominantly based on individuals of European ancestry.
    explanation: Ancestry-specific validation limits transferability of polygenic risk models.
- discussion_id: chek2_wider_tumour_spectrum
  kind: KNOWLEDGE_GAP
  attaches_to:
  - disease#
  prompt: Which additional tumor associations warrant clinical action?
  rationale: A 2025 genome-first study replicated kidney, bladder and lymphoid leukemia associations in MyCode and UK Biobank. Thyroid association appeared only in MyCode; colorectal findings remain discordant across studies. Bonferroni correction was applied to organ-system groups, not individual cancer types, and absolute risks were not estimated. Association evidence therefore does not establish benefit from enhanced organ-specific screening. Testicular germ-cell tumor evidence is separately represented with its limits.
  evidence:
  - reference: PMID:41396600
    reference_title: Genomic Ascertainment of CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: This work provides substantial evidence from both cohorts of significantly increased risk for kidney cancer, bladder cancer, and chronic lymphocytic leukemia (CLL).
    explanation: The primary two-biobank analysis adds replicated associations to the older clinical-review evidence.
  - reference: PMID:41396600
    reference_title: Genomic Ascertainment of CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: A significant excess of malignant neoplasm of thyroid and other endocrine tumors (C73-C75) was observed in MyCode but not UKBB
    explanation: The thyroid association did not replicate across these cohorts.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
    reference_title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: To date, there are no recommendations for enhanced surveillance for other cancers.
    explanation: The March 2026 clinical chapter distinguishes reported associations from actionable surveillance.
- discussion_id: chek2_biallelic_risk
  kind: KNOWLEDGE_GAP
  attaches_to:
  - disease#
  prompt: What are the penetrance and optimal surveillance of biallelic genotypes?
  rationale: The 2024 series included 294 individuals, 159 homozygous for p.Ile157Thr. Overall 157 had at least one malignancy or premalignancy, and 55 of those 157 had multiple such tumors. Among affected women, biallelic loss-of-function variants were associated with earlier onset and more multiple tumors than homozygous p.Ile157Thr. Ascertainment and missing follow-up prevent lifetime penetrance estimates. These genotype strata do not establish a uniform recessive developmental syndrome.
  evidence:
  - reference: PMID:38362852
    reference_title: The heterogeneous cancer phenotype of individuals with biallelic germline pathogenic variants in CHEK2.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: In total, 157 individuals (53.4%; 157/294 individuals) developed ≥1 (pre)malignancy.
    explanation: The denominator includes affected and unaffected individuals and must not be described as 294 null genotypes.
  - reference: url:https://pure.rug.nl/ws/portalfiles/portal/1081701784/PIIS1098360024000340.pdf
    reference_title: https://pure.rug.nl/ws/portalfiles/portal/1081701784/PIIS1098360024000340.pdf
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: 55 in- dividuals (35%) developed multiple (pre)malignancies
    explanation: This institutional PDF is the full text of PMID:38362852, not a separate study. Its primary results report 55 of 157 affected individuals with multiple tumors; the later discussion overstates this as more than half of all participants.
- discussion_id: chek2_prognosis_by_context
  kind: KNOWLEDGE_GAP
  attaches_to:
  - disease#
  prompt: Does CHEK2 genotype independently worsen cancer outcome?
  rationale: Earlier c.1100del breast-cancer cohorts reported heterogeneous survival results. A 2025 genome-first analysis found no significant all-cause survival difference between carriers with cancer and controls with cancer, while overall mortality differed only in UK Biobank, mainly after age 75. These endpoints and ascertainment schemes do not directly resolve variant-specific breast-cancer mortality. Prognosis should be interpreted by cancer type, stage, treatment and competing risks.
  evidence:
  - reference: PMID:41396600
    reference_title: Genomic Ascertainment of CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: There was no statistical difference in all-cause mortality among individuals with cancer between case participants in the all-variant group and control participants in both MyCode
    explanation: The primary analysis concerns all-cause mortality among people with cancer, not a breast-cancer-specific survival endpoint.
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: There was no significant effect on long-term outcome, compared with more than 3000 wild-type controls.
    explanation: The practice review describes one negative survival study alongside reports of poorer c.1100del-associated outcomes.
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Nearly all previous studies had found significantly adverse outcomes (measured variously as overall survival, BC-specific survival and incidence of CBC) for CHEK2 c.1100del heterozygotes, with or without the administration of adjuvant chemotherapy and/or hormone therapy.
    explanation: The ACMG synthesis records adverse findings alongside null studies; the endpoints include survival and contralateral cancer and are not interchangeable.
phenotypes:
- category: Neoplastic
  name: Breast carcinoma
  description: >-
    Female breast cancer is the principal manifestation. Typical lifetime risk estimates are approximately 20–30%, with substantial variation by allele and modifying factors. Many tumors are estrogen-receptor positive, but this is not a defining histology. A selected series of 35 women reported median diagnosis at 45 years (range 25–75), multifocal tumors in 7/35 and synchronous bilateral tumors in 4/35; those figures are not population penetrance estimates.
  phenotype_term:
    preferred_term: Breast carcinoma
    term:
      id: HP:0003002
      label: Breast carcinoma
  evidence:
  - reference: PMID:40440438
    reference_title: CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: CHEK2-related cancer predisposition is predominantly characterized by an increased risk of female breast cancer.
    explanation: GeneReviews identifies the main clinical manifestation.
  - reference: PMID:38091153
    reference_title: Clinicopathologic and genetic analysis of invasive breast carcinomas in women with germline CHEK2 variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Four patients had synchronous bilateral BCs (11%, 4/35) and seven had multifocal BC (20%, 7/35).
    explanation: The primary clinical series retains distinct patient and tumor denominators.
  phenotype_contexts:
  - sex: FEMALE
    population: Heterozygotes assessed in clinical risk guidance; allele and family history modify risk
    notes: GeneReviews gives an average lifetime breast cancer risk of approximately 20–30%, commonly varying within 15–40%; no single frequency band is assigned across all alleles.
    evidence:
    - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
      reference_title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: DIRECT
      snippet: the average lifetime breast cancer risk for a ... heterozygote ... is approximately 20%-30%
      explanation: The March 2026 chapter summarizes approximate lifetime risk, not the frequency within a case series.
- category: Neoplastic
  name: Contralateral breast carcinoma
  description: >-
    After a first breast cancer, carriers of CHEK2 truncating pathogenic variants have an elevated risk of a metachronous contralateral primary. CARRIERS estimated ten-year cumulative incidence of 13% in premenopausal and 4% in postmenopausal carriers. The primary analysis excluded missense and low-penetrance variants; p.Ile157Thr alone was not significantly associated with contralateral risk. The cohort excluded synchronous bilateral disease and adjusted for endocrine therapy and other covariates.
  phenotype_term:
    preferred_term: Contralateral breast carcinoma
    term:
      id: HP:0003002
      label: Breast carcinoma
    laterality: BILATERAL
    description: Metachronous cancers in the two breasts; this is a second primary rather than metastasis.
  evidence:
  - reference: PMID:36623243
    reference_title: Contralateral Breast Cancer Risk Among Carriers of Germline Pathogenic Variants in ATM, BRCA1, BRCA2, CHEK2, and PALB2.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Germline CHEK2 PV carriers had a 1.9-fold elevated risk of CBC overall (HR, 1.9; 95% CI, 1.1 to 3.3; P = .03)
    explanation: The full-text adjusted analysis supplies the CHEK2-specific estimate.
  - reference: PMID:36623243
    reference_title: Contralateral Breast Cancer Risk Among Carriers of Germline Pathogenic Variants in ATM, BRCA1, BRCA2, CHEK2, and PALB2.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: the CHEK2 p.Ile157Thr (c.470T>C) variant was not significantly associated with CBC risk
    explanation: The primary study does not support extrapolating the truncating-variant estimate to Ile157Thr.
  phenotype_contexts:
  - sex: FEMALE
    population: Premenopausal women with prior breast cancer and truncating CHEK2 pathogenic variants in CARRIERS
    notes: Estimated 13% ten-year cumulative incidence; subset uncertainty and treatment exposure matter.
    evidence:
    - reference: PMID:36623243
      reference_title: Contralateral Breast Cancer Risk Among Carriers of Germline Pathogenic Variants in ATM, BRCA1, BRCA2, CHEK2, and PALB2.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Among premenopausal women, the 10-year cumulative incidence of CBC was estimated to be 33% for BRCA1, 27% for BRCA2, and 13% for CHEK2 PV carriers with breast cancer
      explanation: The primary prospective cohort provides the ten-year premenopausal estimate.
  - sex: FEMALE
    population: Postmenopausal women with prior breast cancer and truncating CHEK2 pathogenic variants in CARRIERS
    notes: Estimated 4% ten-year cumulative incidence; this must not be compared with a five-year population risk as if horizons matched.
    evidence:
    - reference: PMID:36623243
      reference_title: Contralateral Breast Cancer Risk Among Carriers of Germline Pathogenic Variants in ATM, BRCA1, BRCA2, CHEK2, and PALB2.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: The 10-year cumulative incidence of CBC among postmenopausal PV carriers was 12% for BRCA1, 9% for BRCA2, and 4% for CHEK2.
      explanation: The source supplies a ten-year, menopause-specific estimate.
- category: Neoplastic
  name: Prostate cancer
  description: >-
    Prostate cancer risk is increased, but absolute lifetime penetrance remains uncertain. Genome-first estimates were OR 1.62 in MyCode and 1.78 in UK Biobank; these are association estimates from predominantly European-ancestry cohorts, not the probability that an individual carrier develops cancer.
  phenotype_term:
    preferred_term: Prostate cancer
    term:
      id: HP:0012125
      label: Prostate cancer
  evidence:
  - reference: PMID:40440438
    reference_title: CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: To a lesser extent there is an association with increased risk of prostate cancer.
    explanation: Clinical synthesis recognizes the association.
  - reference: PMID:41396600
    reference_title: Genomic Ascertainment of CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: prostate (OR, 1.62 [95% CI, 1.27-2.07]; OR, 1.78 [95% CI, 1.48-2.16], respectively)
    explanation: The 2025 study reports MyCode and UK Biobank estimates.
- category: Neoplastic
  name: Testicular neoplasm
  description: >-
    A 2019 case-control study reported enrichment of germline loss-of-function CHEK2 variants in testicular germ-cell tumors and diagnosis approximately six years earlier among carriers. This is a reported susceptibility association with less established clinical actionability than female breast cancer. The 2025 biobank analysis was likely underpowered for this rare cancer; it does not establish either confirmation or refutation.
  phenotype_term:
    preferred_term: Testicular neoplasm
    term:
      id: HP:0010788
      label: Testicular neoplasm
  evidence:
  - reference: PMID:30676620
    reference_title: "Association of Inherited Pathogenic Variants in Checkpoint Kinase 2 (CHEK2) With Susceptibility to Testicular Germ Cell Tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Unselected men with TGCTs were approximately 4 times more likely to carry germline loss-of-function CHEK2 variants compared with cancer-free individuals from the Exome Aggregation Consortium cohort"
    explanation: Quantifies the enrichment of loss-of-function CHEK2 variants in testicular germ cell tumour cases.
    quote_role: PRIMARY_RESULT
    directness: DIRECT
  - reference: PMID:30676620
    reference_title: "Association of Inherited Pathogenic Variants in Checkpoint Kinase 2 (CHEK2) With Susceptibility to Testicular Germ Cell Tumors."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Individuals with the pathogenic CHEK2 loss-of-function variants developed TGCTs 6 years earlier than individuals with CHEK2 wild-type alleles"
    explanation: Documents the earlier age at onset in carriers.
    quote_role: PRIMARY_RESULT
    directness: DIRECT
  - reference: PMID:41396600
    reference_title: Genomic Ascertainment of CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: For some rarer cancers (male breast, testicular), the 2 cohorts were likely underpowered
    explanation: The newer genome-first analysis cannot confidently settle this rare-tumor association.
- category: Neoplastic
  name: Male breast carcinoma
  description: >-
    Male breast cancer is uncommon in absolute terms. The 2023 ACMG review summarizes a meta-analysis OR of 3.13 (95% CI 1.94–5.07), while also emphasizing inconsistent studies and insufficient evidence in its broader-cancer summary. The March 2026 GeneReviews chapter recognizes an increased male breast cancer risk. A historical tenfold founder-allele estimate should not be generalized to all CHEK2 variants.
  phenotype_term:
    preferred_term: Breast carcinoma
    term:
      id: HP:0003002
      label: Breast carcinoma
  evidence:
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: A recent meta-analysis showed an increased risk for MBC for CHEK2 heterozygotes (OR 3.13, 95% CI 1.94–5.07).
    explanation: The meta-analysis estimate is relative risk evidence, not absolute penetrance.
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: There have been conflicting findings in male BC (MBC), most likely because many of the studies have been small and in populations where c.1100del is not prevalent.
    explanation: The same guidance describes limits of the association evidence.
  phenotype_contexts:
  - sex: MALE
    notes: Sex-specific breast cancer association; absolute risk is substantially lower than in female carriers.
genetic:
- name: CHEK2
  variant_origin: GERMLINE
  gene_term:
    preferred_term: CHEK2
    term:
      id: hgnc:16627
      label: CHEK2
  relationship_type: CAUSATIVE
  notes: The gene-level association establishes an inherited predisposition, not uniform penetrance for every variant. Truncating alleles and some missense alleles confer moderate risk; p.Ile157Thr, p.Ser428Phe and p.Thr476Met have lower or uncertain actionable risk in isolation. Allele frequencies vary by ancestry and founder population. In a 2025 genome-first analysis, 3,153 of 167,050 MyCode adults and 3,232 of 469,765 UK Biobank participants met the study pathogenic/likely pathogenic variant definition, which included common lower-risk missense variants and excluded copy-number variants; these are cohort-specific carrier proportions, not disease prevalence.
  evidence:
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: the average lifetime BC risk for a CHEK2 heterozygote is approximately 25%, absolute risks can range from 15% to 40%
    explanation: ACMG summarizes the wide distribution of breast cancer risk.
  - reference: PMID:41396600
    reference_title: Genomic Ascertainment of CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: There were 469 765 individuals in the UKBB cohort and 167 050 individuals in MyCode.
    explanation: The primary study defines the denominator for its genome-first ascertainment.
  - reference: PMID:41396600
    reference_title: Genomic Ascertainment of CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Overall, there were 3232 case participants ... in UKBB and 3153 case participants ... in MyCode
    explanation: The full results give carrier counts for both biobanks under the same study-specific variant-classification rules.
  variants:
  - name: NM_007194.4:c.1100del p.(Thr367MetfsTer15)
    clinical_significance: PATHOGENIC
    description: Northern European founder frameshift that disrupts the kinase domain. ACMG cites an odds ratio of 2.66 (95% CI 2.27–3.11) for female breast cancer. This association does not imply that every carrier develops cancer.
    functional_effects:
    - function: loss of CHK2 kinase activity
      description: Truncation disrupts kinase function; functional dosage and residual protein can vary by tissue and assay.
    evidence:
    - reference: PMID:33322746
      reference_title: 'CHEK2 Germline Variants in Cancer Predisposition: Stalemate Rather than Checkmate.'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: DIRECT
      snippet: The first functional analysis revealed that c.1100delC completely abrogates CHK2 kinase activity
      explanation: Review synthesis of the founder-allele functional experiments.
    - reference: PMID:37490054
      reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: DIRECT
      snippet: reporting an odds ratio (OR) of 2.66 (95% CI 2.27–3.11)
      explanation: The risk estimate concerns c.1100del; the preceding counts in the review refer to carriers, not total study enrollment.
  - name: NM_007194.4:c.470T>C p.(Ile157Thr)
    description: Common lower-penetrance FHA-domain missense allele. ACMG reports breast cancer OR 1.30 (95% CI 1.06–1.59), below actionability thresholds when considered alone. Laboratory classifications have varied; functional impairment and clinical actionability are distinct.
    functional_effects:
    - function: partial, assay-dependent impairment of CHK2 function
      description: Purified recombinant protein retained approximately 40–50% of wild-type kinase activity at saturating ATP in a CDC25-peptide assay. This result does not establish equivalent impairment of every substrate in vivo.
    evidence:
    - reference: PMID:37490054
      reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: DIRECT
      snippet: p.(Ile157Thr) (OR 1.30, 95% CI 1.06–1.59; P = .01)
      explanation: This is the variant-specific estimate; OR 1.42 for a different rare-missense aggregate must not be assigned to this allele.
    - reference: PMID:38367672
      reference_title: CHEK2 germline variants identified in familial nonmedullary thyroid cancer lead to impaired protein structure and function.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: At saturating ATP, the CHK2 p.I157T and p.E321A variants presented 40 to 50% of the WT CHK2 enzymatic activity
      explanation: The purified-protein CDC25-peptide assay measures residual function, not patient cancer risk.
  - name: NM_007194.4:c.1283C>T p.(Ser428Phe)
    description: Common missense allele with lower or uncertain clinical impact in isolation. The ACMG review cites OR 1.26 (95% CI 0.76–2.12), which was not statistically significant in that study; surveillance should reflect the full risk assessment.
    evidence:
    - reference: PMID:37490054
      reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: DIRECT
      snippet: p.(Ser428Phe) (OR 1.26, 95% CI 0.76–2.12; P = .37)
      explanation: The variant-specific confidence interval includes no association.
  - name: NM_007194.4:c.349A>G p.(Arg117Gly)
    description: 'A missense variant with breast cancer risk estimates closer to truncating alleles: OR 2.26 (95% CI 1.29–3.95) and 2.69 (95% CI 1.46–4.94) in studies summarized by ACMG. Not all missense alleles belong in a uniformly low-risk class.'
    evidence:
    - reference: PMID:37490054
      reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
      supports: SUPPORT
      evidence_source: OTHER
      quote_role: REVIEW_SYNTHESIS
      directness: DIRECT
      snippet: The study reported an association of p.(Arg117Gly) with BC (OR 2.26, 95% CI 1.29–3.95).
      explanation: A variant-specific association distinguishes Arg117Gly from common lower-risk missense alleles.
diagnosis:
- name: Germline molecular diagnosis
  description: Identify a pathogenic or likely pathogenic germline CHEK2 variant with a validated assay, usually a hereditary cancer multigene panel. A variant of uncertain significance is nondiagnostic. Some historically pathogenic common missense variants have lower penetrance and require variant-specific interpretation.
  evidence:
  - reference: PMID:40440438
    reference_title: CHEK2-Related Cancer Predisposition.
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: The diagnosis of CHEK2-related cancer predisposition is established in a proband with a heterozygous germline pathogenic variant in CHEK2 identified by molecular genetic testing.
    explanation: GeneReviews states the germline diagnostic basis.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
    reference_title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: uncertain significance ... does not establish or rule out the diagnosis.
    explanation: A VUS is not a diagnostic or predictive family-test result.
- name: Sequencing and deletion/duplication assessment
  description: Testing should cover small sequence variants and validated copy-number analysis; sequencing alone may miss exon or whole-gene deletions. CHEK2 pseudogene homology can complicate assay design. Exome or genome data do not automatically guarantee equivalent deletion/duplication sensitivity.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
    reference_title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: multiexon, or whole-gene deletions/duplications may not be detected.
    explanation: GeneReviews notes the limitation of some sequencing methods.
  - reference: PMID:33322746
    reference_title: 'CHEK2 Germline Variants in Cancer Predisposition: Stalemate Rather than Checkmate.'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: The 3′ portion of the CHEK2 gene comprising exons 10–14 is duplicated with >90% homology in the human genome
    explanation: The review identifies a locus-specific technical testing issue.
- name: Constitutional versus acquired variant assessment
  description: A CHEK2 alteration found in tumor or blood is not automatically inherited. Clonal hematopoiesis can produce acquired blood variants, sometimes at apparently heterozygous allele fractions. When the clinical context raises doubt, testing appropriate non-hematopoietic tissue helps distinguish a constitutional variant from an acquired hematopoietic clone.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
    reference_title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Variants at ... frequencies in the heterozygous range may also be acquired
    explanation: The full chapter explicitly cautions that allele fraction alone does not establish germline origin.
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
    reference_title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: further testing of different tissues to determine if a pathogenic variant is ... constitutional ... or somatic should be guided by clinical evaluation
    explanation: Clinical interpretation and tissue comparison guide origin assessment.
treatments:
- name: Breast cancer surveillance
  description: >-
    Annual mammography typically begins at age 40. The March 2026 GeneReviews chapter summarizes US guidance to consider annual MRI at age 30–35 in those with additional risk factors and according to preferences; UK recommendations use individualized CanRisk thresholds. Lower-risk missense variants require a family-history-based assessment. Predicted mortality benefit from MRI comes from modeling, not a randomized CHEK2 screening trial. The models assumed complete screening participation and guideline-concordant cancer therapy and projected false-positive examinations and benign biopsies as well as benefit.
  treatment_term:
    preferred_term: cancer screening
    term:
      id: NCIT:C15406
      label: Cancer Screening
  evidence:
  - reference: PMID:40440438
    reference_title: "CHEK2-Related Cancer Predisposition."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Breast cancer surveillance in females typically includes breast self-exam training and symptom awareness; mammogram every 12 months beginning at age 40 years; breast MRI recommendations vary by location."
    explanation: Specifies the surveillance protocol.
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
  - reference: PMID:37490054
    reference_title: "Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "early cancer detection and prevention for CHEK2 heterozygotes should be guided by personalized risk estimates"
    explanation: Establishes that surveillance intensity is set by personalised risk rather than by carrier status.
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
    reference_title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Consider annually from age 30-35 yrs in those w/strong family history, other risk factors
    explanation: The full surveillance table gives a qualified US MRI recommendation.
  - reference: PMID:35175286
    reference_title: 'Breast Cancer Screening Strategies for Women With ATM, CHEK2, and PALB2 Pathogenic Variants: A Comparative Modeling Analysis.'
    supports: SUPPORT
    evidence_source: COMPUTATIONAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: annual MRI screening starting at 30 to 35 years followed by annual MRI and mammography at 40 years may reduce breast cancer mortality by more than 50%
    explanation: Two microsimulation models projected benefit separately for ATM, CHEK2 and PALB2 risk groups. The quoted conclusion summarizes the three groups; this is not an observed clinical trial result.
  target_mechanisms:
  - target: Breast carcinoma
    description: >-
      Surveillance does not modify the mechanism; it detects the tumour phenotype
      earlier.
- name: Prostate cancer surveillance
  description: >-
    Annual serum PSA may be considered from age 40, particularly with a strong family
    history of prostate cancer.
  treatment_term:
    preferred_term: cancer screening
    term:
      id: NCIT:C15406
      label: Cancer Screening
  evidence:
  - reference: PMID:40440438
    reference_title: "CHEK2-Related Cancer Predisposition."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Prostate cancer surveillance in males includes serum PSA to be considered annually beginning at age 40 years especially in those with a strong family history of prostate cancer."
    explanation: Specifies the prostate surveillance recommendation.
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
- name: Risk-reducing mastectomy
  description: >-
    Bilateral or contralateral risk-reducing mastectomy is not routine solely for CHEK2 heterozygosity. Consider personal and family history, age, estimated lifetime or contralateral risk, competing risks and patient preferences. Surveillance remains an option; a moderate relative risk alone does not establish survival benefit from surgery.
  therapeutic_modality: SURGERY
  treatment_term:
    preferred_term: Prophylactic Mastectomy
    term:
      id: NCIT:C94445
      label: Prophylactic Mastectomy
  evidence:
  - reference: PMID:40440438
    reference_title: "CHEK2-Related Cancer Predisposition."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Breast cancer risk-reducing contralateral mastectomy is generally not recommended but may be considered in some situations."
    explanation: States that this intervention is not routine, which is the clinically important negative.
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
  - reference: PMID:37490054
    reference_title: "Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG)."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Risk-reducing mastectomy should be guided by personalized risk estimates and shared decision making."
    explanation: The ACMG resource frames the decision as risk-estimate driven rather than genotype driven.
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
- name: Cancer-directed treatment
  description: >-
    Treat established cancer according to site, stage, histology and validated tumor biomarkers. CHEK2 carrier status alone does not establish a broadly effective targeted treatment. In a selected breast pathology series, all evaluable neoadjuvant cases showed tumor-size and Ki67 reductions, but only 3 of 14 treated patients achieved pathologic complete response; two complete responders had HER2-positive tumors. This uncontrolled, largely ER-positive series cannot establish universal chemoresistance.
  treatment_term:
    preferred_term: Therapeutic Procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
    reference_title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: there is insufficient evidence to recommend specific cancer treatment based on identification of ... related cancer predisposition. Standard cancer treatments are recommended.
    explanation: GeneReviews does not identify a broadly effective CHEK2-predisposition-specific treatment.
  - reference: PMID:38091153
    reference_title: Clinicopathologic and genetic analysis of invasive breast carcinomas in women with germline CHEK2 variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Although decreased post-treatment tumor size and Ki67 proliferative index reflected treatment effect in all evaluable cases, only three patients in our series achieved pCR.
    explanation: The primary treatment observations show activity and limited complete responses, not complete lack of chemotherapy sensitivity.
- name: Genetic counseling and cascade testing
  description: >-
    Offer targeted familial-variant testing to at-risk adult relatives with counseling about variant-specific, incomplete penetrance. Each child of a heterozygote has a 50% transmission risk. A relative who tests negative may retain risk from other family-history factors. Routine predictive testing in childhood is generally not offered because the established management is directed at adult risk.
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:40440438
    reference_title: "CHEK2-Related Cancer Predisposition."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Molecular genetic testing of at-risk female and male adult relatives can identify those family members who also have the familial pathogenic variant and thus may benefit from increased cancer surveillance."
    explanation: States the cascade testing rationale.

    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Predictive genetic testing for a familial CHEK2 variant is not routinely recommended in childhood.
    explanation: The ACMG practice resource limits routine predictive testing in minors.
- name: Colorectal screening according to personal and family history
  description: CHEK2 heterozygosity alone does not currently justify intensified colonoscopy. Use general-population colorectal screening unless personal history, polyps or family history independently indicate more intensive surveillance. This reflects the 2024 NCCN change summarized in the March 2026 GeneReviews chapter, despite discordant epidemiologic association reports.
  treatment_term:
    preferred_term: Cancer Screening
    term:
      id: NCIT:C15406
      label: Cancer Screening
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
    reference_title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: NCCN recommends general population screening for CRC in those w/ ... CHEK2 ... cancer predisposition.
    explanation: The clinical chapter explicitly states current population screening guidance for CHEK2 predisposition.
  - reference: DOI:10.6004/jnccn.2024.0061
    reference_title: 'Genetic/Familial High-Risk Assessment: Colorectal, Endometrial, and Gastric, Version 3.2024, NCCN Clinical Practice Guidelines In Oncology'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: de-implementation of colon cancer screening in individuals with CHEK2 pathogenic/likely pathogenic variants
    explanation: The guideline update concerns de-implementation of CHEK2-specific intensified screening, not abandonment of ordinary colorectal screening.
- name: Olaparib under tumor-specific indications or trials
  description: CHEK2 alteration is not a reliable general predictor of PARP-inhibitor benefit. In TBCRC 048 metastatic breast cancer, no responses were observed with CHEK2 mutations alone. Separately, the US olaparib label includes qualifying CHEK2 alterations among HRR-gene-mutated metastatic castration-resistant prostate cancers after progression on enzalutamide or abiraterone, with approved companion-diagnostic selection. Regulatory eligibility for that specific indication does not establish CHEK2-specific efficacy or imply eligibility for breast cancer solely on CHEK2 status.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Olaparib treatment
    therapeutic_agent:
    - preferred_term: olaparib
      term:
        id: CHEBI:83766
        label: olaparib
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: PMID:33119476
    reference_title: 'TBCRC 048: Phase II Study of Olaparib for Metastatic Breast Cancer and Mutations in Homologous Recombination-Related Genes.'
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: No responses were observed with ATM or CHEK2 mutations alone.
    explanation: The phase II breast-cancer trial refutes efficacy inferred from CHEK2 alteration alone in that study population.
  - reference: url:https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/208558s031lbl.pdf
    reference_title: https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/208558s031lbl.pdf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: cancer (mCRPC) who have progressed following prior treatment with enzalutamide or abiraterone.
    explanation: The FDA label defines the preceding-treatment setting; its biomarker-selection table explicitly lists CHEK2 among eligible HRR genes.
  - reference: url:https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/208558s031lbl.pdf
    reference_title: https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/208558s031lbl.pdf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Germline or somatic HRR gene-mutated metastatic castration-resistant prostate cancer ATMm, BRCA1m, BRCA2m, BARD1m, BRIP1m, CDK12m, CHEK1m, CHEK2m, FANCLm, PALB2m, RAD51Bm, RAD51Cm, RAD51Dm, RAD54Lm
    explanation: The label’s biomarker-selection table explicitly includes CHEK2 for this prostate-cancer indication.
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: Those treated with olaparib (n = 7) had a numerically longer median progression-free survival compared with the control arm (n = 5; 5.59 months vs 3.35 months), but this was not statistically significant.
    explanation: The ACMG review summarizes the very small CHEK2-only PROfound subgroup; the comparison does not establish gene-specific benefit.
- name: Ovarian risk management
  description: Risk-reducing salpingo-oophorectomy is not recommended solely on the basis of CHEK2 heterozygosity. Any indication should arise from another established risk factor or diagnosis.
  therapeutic_modality: SURGERY
  evidence:
  - reference: PMID:37490054
    reference_title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: There is no evidence for an increased risk for ovarian cancer in CHEK2 heterozygotes.
    explanation: The ACMG resource does not support CHEK2-heterozygosity-specific ovarian risk reduction.
references:
- reference: PMID:40440438
  title: CHEK2-Related Cancer Predisposition.
  tags:
  - GeneReviews
- reference: PMID:33322746
  title: 'CHEK2 Germline Variants in Cancer Predisposition: Stalemate Rather than Checkmate.'
- reference: PMID:37490054
  title: 'Management of individuals with germline pathogenic/likely pathogenic variants in CHEK2: A clinical practice resource of the American College of Medical Genetics and Genomics (ACMG).'
- reference: PMID:38091153
  title: Clinicopathologic and genetic analysis of invasive breast carcinomas in women with germline CHEK2 variants.
- reference: PMID:18614044
  title: Chk2 suppresses the oncogenic potential of DNA replication-associated DNA damage.
- reference: PMID:19805189
  title: Mice with the CHEK2*1100delC SNP are predisposed to cancer with a strong gender bias.
- reference: PMID:38848470
  title: The genomic landscape of breast and non-breast cancers from individuals with germline CHEK2 deficiency.
- reference: PMID:41396600
  title: Genomic Ascertainment of CHEK2-Related Cancer Predisposition.
- reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
  title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
  tags:
  - GeneReviews
- reference: PMID:38362852
  title: The heterogeneous cancer phenotype of individuals with biallelic germline pathogenic variants in CHEK2.
- reference: url:https://pure.rug.nl/ws/portalfiles/portal/1081701784/PIIS1098360024000340.pdf
  title: https://pure.rug.nl/ws/portalfiles/portal/1081701784/PIIS1098360024000340.pdf
- reference: PMID:36623243
  title: Contralateral Breast Cancer Risk Among Carriers of Germline Pathogenic Variants in ATM, BRCA1, BRCA2, CHEK2, and PALB2.
- reference: PMID:30676620
  title: Association of Inherited Pathogenic Variants in Checkpoint Kinase 2 (CHEK2) With Susceptibility to Testicular Germ Cell Tumors.
- reference: PMID:38367672
  title: CHEK2 germline variants identified in familial nonmedullary thyroid cancer lead to impaired protein structure and function.
- reference: DOI:10.6004/jnccn.2024.0061
  title: 'Genetic/Familial High-Risk Assessment: Colorectal, Endometrial, and Gastric, Version 3.2024, NCCN Clinical Practice Guidelines In Oncology'
- reference: PMID:33119476
  title: 'TBCRC 048: Phase II Study of Olaparib for Metastatic Breast Cancer and Mutations in Homologous Recombination-Related Genes.'
- reference: url:https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/208558s031lbl.pdf
  title: https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/208558s031lbl.pdf
- reference: clinicaltrials:NCT05011383
  title: High-dose Testosterone in Men With Metastatic Castration-resistant Prostate Cancer and ATM or CDK12 Deficiency
- reference: clinicaltrials:NCT05033756
  title: A Phase II Open-Label Study for the Comprehensive Analysis of Predictors of the Treatment With Pembrolizumab and Olaparib in Patients With Unresectable or Metastatic HER2 Negative Breast Cancer and a Deleterious Germline Mutation in BRCA1/2, ATM, BARD1, CHEK2, FANCC, PALB2, RAD51C, RAD51D, SLX4, XRCC2 or a Homologous Recombination Deficiency
- reference: clinicaltrials:NCT02401347
  title: A Phase II Clinical Trial of the PARP Inhibitor Talazoparib in BRCA1 and BRCA2 Wild Type Patients With Advanced Triple Negative Breast Cancer and Homologous Recombination Deficiency or Advanced HER2 Negative Breast Cancer or Other Solid Tumors With a Mutation in Homologous Recombination Pathway Genes
- reference: clinicaltrials:NCT03786796
  title: Phase II Study of Olaparib in Metastatic Renal Cell Carcinoma Patients Harboring a BAP-1 or Other DNA Repair Gene Mutations (ORCHID)
- reference: clinicaltrials:NCT06033092
  title: 'Low Dose TamOxifen and LifestylE Changes for bReast cANcer prevenTion: a Randomized Phase II Biomarker Trial in Subjects at Increased Risk'
- reference: clinicaltrials:NCT03344965
  title: A Phase 2 Study of Olaparib Monotherapy in Metastatic Breast Cancer Patients With Germline or Somatic Mutations in DNA Repair Genes (Olaparib Expanded)
- reference: PMID:35175286
  title: 'Breast Cancer Screening Strategies for Women With ATM, CHEK2, and PALB2 Pathogenic Variants: A Comparative Modeling Analysis.'
- reference: PMID:17174984
  title: The breast cancer susceptibility allele CHEK2*1100delC promotes genomic instability in a knock-in mouse model.
histopathology:
- name: Invasive ductal carcinoma of no special type
  finding_term:
    preferred_term: Invasive Breast Carcinoma of No Special Type
    term:
      id: NCIT:C4194
      label: Invasive Breast Carcinoma of No Special Type
  description: In a selected series of 35 women with 44 invasive breast cancers, 38/44 tumors were IDC-NST. Lobular, mixed ductal/lobular and papillary cancers also occurred. Histology does not diagnose germline CHEK2 predisposition.
  diagnostic: false
  evidence:
  - reference: PMID:38091153
    reference_title: Clinicopathologic and genetic analysis of invasive breast carcinomas in women with germline CHEK2 variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: BCs were predominantly invasive ductal carcinomas of no special type (IDC-NST) (86%, 38/44).
    explanation: Tumor denominator in a selected pathology series; not carrier penetrance.
- name: Estrogen receptor positivity
  finding_term:
    preferred_term: Estrogen Receptor Positive by Immunohistochemistry
    term:
      id: NCIT:C141465
      label: Estrogen Receptor Positive by Immunohistochemistry
  description: ER positivity was present in 41/43 evaluable tumors in the same series; 34/43 were ER-positive/HER2-negative and 7/43 ER-positive/HER2-positive. The selected series included no triple-negative tumors, which does not establish their impossibility in carriers.
  diagnostic: false
  evidence:
  - reference: PMID:38091153
    reference_title: Clinicopathologic and genetic analysis of invasive breast carcinomas in women with germline CHEK2 variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Nearly all BCs were ER + (95%, 41/43)
    explanation: The primary pathology result documents receptor positivity.
- name: Luminal B immunohistochemical surrogate phenotype
  finding_term:
    preferred_term: Luminal B Breast Carcinoma
    term:
      id: NCIT:C53555
      label: Luminal B Breast Carcinoma
  description: Using immunohistochemical surrogates and a Ki67 cutpoint of 14%, 25/36 tumors were classified as luminal B. These are surrogate classifications from one selected series, not a universal molecular subtype for CHEK2-associated breast cancer.
  diagnostic: false
  evidence:
  - reference: PMID:38091153
    reference_title: Clinicopathologic and genetic analysis of invasive breast carcinomas in women with germline CHEK2 variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: Using immunohistochemical surrogates for molecular subtyping, most (69%, 25/36) BCs were classified as luminal B
    explanation: The assay and denominator qualify the subtype claim.
- name: Sparse tumor-infiltrating lymphocytes
  description: Tumor-infiltrating lymphocytes occupied less than 10% in 34/38 evaluated tumors. The observation does not prove immune suppression as the cause of CHEK2-associated cancer or predict immunotherapy response.
  diagnostic: false
  evidence:
  - reference: PMID:38091153
    reference_title: Clinicopathologic and genetic analysis of invasive breast carcinomas in women with germline CHEK2 variants.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: TILs were sparse (< 10%) in most (89%, 34/38) cases
    explanation: The primary series records a microscopic observation.
differential_diagnoses:
- name: Other hereditary breast cancer predispositions
  description: BRCA1/2, PALB2, ATM and syndromic predispositions including TP53, PTEN, CDH1 and STK11 can overlap clinically.
  distinguishing_features:
  - The combination of tumor types and ages does not reliably distinguish CHEK2 from other inherited cancer predispositions.
  - Molecular testing and syndrome-specific features determine the appropriate diagnosis and surveillance.
  evidence:
  - reference: url:https://www.ncbi.nlm.nih.gov/sites/books/NBK615090/
    reference_title: CHEK2-Related Cancer Predisposition - GeneReviews® - NCBI Bookshelf
    supports: SUPPORT
    evidence_source: OTHER
    quote_role: REVIEW_SYNTHESIS
    directness: DIRECT
    snippet: It is not possible to distinguish ... related cancer predisposition from these other cancer susceptibility syndromes based solely on the constellation of tumors and ages of cancer onset present in the family.
    explanation: GeneReviews supports molecular differentiation when clinical cancer patterns overlap.
clinical_trials:
- name: NCT05011383
  description: Intermittent high-dose testosterone in ATM-, CDK12- or CHEK2-altered prostate cancer. The protocol tests a predictive hypothesis and does not establish CHEK2-specific response.
  phase: PHASE_II
  status: RECRUITING
  notes: Registry checked 2026-10-01; last posted update 2026-09-17; enrollment 51 (estimated). The cached summary supports the study purpose; status and eligibility were checked against the current registry record.
  evidence:
  - reference: clinicaltrials:NCT05011383
    reference_title: High-dose Testosterone in Men With Metastatic Castration-resistant Prostate Cancer and ATM or CDK12 Deficiency
    supports: SUPPORT
    evidence_source: OTHER
    directness: DIRECT
    snippet: the genes ATM, CDK12 or CHEK2 predicts for a high likelihood of responding to the use of intermittent high dose testosterone.
    explanation: The registered protocol supports the intervention and study purpose; it is not an efficacy result.
- name: NCT05033756
  description: COMPRENDO evaluates pembrolizumab plus olaparib in advanced HER2-negative breast cancer. The second cohort includes germline CHEK2 and other moderate-penetrance repair genes. No CHEK2-specific benefit can be inferred from enrollment.
  phase: PHASE_II
  status: ACTIVE_NOT_RECRUITING
  notes: Registry checked 2026-10-01; last posted update 2024-05-07; enrollment 11 (actual). The cached summary supports the study purpose; status and eligibility were checked against the current registry record.
  evidence:
  - reference: clinicaltrials:NCT05033756
    reference_title: A Phase II Open-Label Study for the Comprehensive Analysis of Predictors of the Treatment With Pembrolizumab and Olaparib in Patients With Unresectable or Metastatic HER2 Negative Breast Cancer and a Deleterious Germline Mutation in BRCA1/2, ATM, BARD1, CHEK2, FANCC, PALB2, RAD51C, RAD51D, SLX4, XRCC2 or a Homologous Recombination Deficiency
    supports: SUPPORT
    evidence_source: OTHER
    directness: DIRECT
    snippet: This study will examine the combination of pembrolizumab and olaparib in three populations.
    explanation: The registered protocol supports the intervention and study purpose; it is not an efficacy result.
- name: NCT02401347
  description: Talazoparib beyond germline BRCA1/2 in advanced breast or other solid tumors with qualifying pathway alterations. CHEK2 appears among eligible genes in the registry criteria. Completion alone does not demonstrate efficacy in CHEK2 carriers.
  phase: PHASE_II
  status: COMPLETED
  notes: Registry checked 2026-10-01; last posted update 2023-02-21; enrollment 21 (actual). The cached summary supports the study purpose; status and eligibility were checked against the current registry record.
  evidence:
  - reference: clinicaltrials:NCT02401347
    reference_title: A Phase II Clinical Trial of the PARP Inhibitor Talazoparib in BRCA1 and BRCA2 Wild Type Patients With Advanced Triple Negative Breast Cancer and Homologous Recombination Deficiency or Advanced HER2 Negative Breast Cancer or Other Solid Tumors With a Mutation in Homologous Recombination Pathway Genes
    supports: SUPPORT
    evidence_source: OTHER
    directness: DIRECT
    snippet: The aim of this single-arm phase 2 clinical trial is to evaluate the anti-cancer activity of Talazoparib
    explanation: The registered protocol supports the intervention and study purpose; it is not an efficacy result.
- name: NCT03786796
  description: ORCHID evaluates olaparib in metastatic renal-cell carcinoma with qualifying DNA-repair alterations, including CHEK2, after prior anti-VEGF or immune-checkpoint therapy. This is a basket eligibility criterion, not a germline CHEK2-specific regimen.
  phase: PHASE_II
  status: RECRUITING
  notes: Registry checked 2026-10-01; last posted update 2026-03-30; enrollment 20 (estimated). The cached summary supports the study purpose; status and eligibility were checked against the current registry record.
  evidence:
  - reference: clinicaltrials:NCT03786796
    reference_title: Phase II Study of Olaparib in Metastatic Renal Cell Carcinoma Patients Harboring a BAP-1 or Other DNA Repair Gene Mutations (ORCHID)
    supports: SUPPORT
    evidence_source: OTHER
    directness: DIRECT
    snippet: participants with metastatic renal cell carcinoma that harbor an inactivating mutation in BAP-1, ATM, BRCA1, BRCA2, PALB2, CHEK2
    explanation: The registered protocol supports the intervention and study purpose; it is not an efficacy result.
- name: NCT06033092
  description: Low-dose tamoxifen and lifestyle interventions in women at increased breast cancer risk, including eligible germline CHEK2 carriers. The primary six-month endpoint is circulating SHBG, a biomarker; it does not directly establish reduced CHEK2-associated cancer incidence.
  phase: PHASE_II
  status: COMPLETED
  notes: Registry checked 2026-10-01; last posted update 2026-09-11; enrollment 110 (actual). The cached summary supports the study purpose; status and eligibility were checked against the current registry record.
  evidence:
  - reference: clinicaltrials:NCT06033092
    reference_title: 'Low Dose TamOxifen and LifestylE Changes for bReast cANcer prevenTion: a Randomized Phase II Biomarker Trial in Subjects at Increased Risk'
    supports: SUPPORT
    evidence_source: OTHER
    directness: DIRECT
    snippet: verify whether Low Dose Tamoxifen (LDT) increases circulating levels of SHBG more than lifestyle intervention
    explanation: The registered protocol supports the intervention and study purpose; it is not an efficacy result.
- name: NCT03344965
  description: TBCRC 048 / Olaparib Expanded examines olaparib in metastatic breast cancer with qualifying germline or somatic DNA-repair variants. The published initial cohort found no responses with CHEK2 mutations alone; overall trial results must not be assigned to each gene subgroup.
  phase: PHASE_II
  status: ACTIVE_NOT_RECRUITING
  notes: Registry checked 2026-10-01; last posted update 2026-01-05; enrollment 114 (estimated). The cached summary supports the study purpose; status and eligibility were checked against the current registry record.
  evidence:
  - reference: clinicaltrials:NCT03344965
    reference_title: A Phase 2 Study of Olaparib Monotherapy in Metastatic Breast Cancer Patients With Germline or Somatic Mutations in DNA Repair Genes (Olaparib Expanded)
    supports: SUPPORT
    evidence_source: OTHER
    directness: DIRECT
    snippet: This study will evaluate whether olaparib is effective in breast cancer patients whose tumor has a mutation in one of the other genes that function with BRCA1 and BRCA2 to repair damaged DNA
    explanation: The registered protocol supports the intervention and study purpose; it is not an efficacy result.
animal_models:
- name: Chk2 1100delC knock-in mouse
  species: Mus musculus
  genotype: Chek2*1100delC heterozygotes and homozygotes; backcrossed at least five generations to FVB
  publication: PMID:19805189
  description: Spontaneous tumors were followed for up to 24 months. Homozygotes showed a significant overall increase; the heterozygote comparison was not significant in the pooled-sex analysis. Female-biased effects and varied tumor types limit direct transfer to human breast risk. In a separate DMBA challenge, mammary tumor latency decreased in homozygotes but not heterozygotes; all exposed genotype groups had shortened survival.
  evidence:
  - reference: PMID:19805189
    reference_title: Mice with the CHEK2*1100delC SNP are predisposed to cancer with a strong gender bias.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: The difference between heterozygous and wild-type mice is not statistically significant (P = 0.127) but shows a developing trend by 24 months.
    explanation: The full-text result qualifies the abstract-level statement of cancer predisposition.
  modeled_mechanisms:
  - target: Germline CHEK2 Loss of Function
    description: Introduces the founder-equivalent truncating allele.
    evidence:
    - reference: PMID:19805189
      reference_title: Mice with the CHEK2*1100delC SNP are predisposed to cancer with a strong gender bias.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: mice heterozygous and homozygous for Chk2*1100delC and their wild-type counterparts were maintained for up to 2 years
      explanation: The germline knock-in comparison tests allele dosage.
    relationship: PERTURBS
    model_scale: MOLECULAR
    limitations: Species, genetic background, sex and genotype alter tumor outcomes; pooled heterozygote tumor incidence was not significantly elevated.
    fidelity: MODERATE
- name: Chk2-null and Mre11-complex compound-mutant mice
  species: Mus musculus
  genotype: Chk2−/− alone or with Nbs1ΔB/ΔB or Mre11ATLD1/ATLD1
  publication: PMID:18614044
  description: Single-mutant mice were not predisposed to malignancy in this experiment, whereas roughly 40% of the compound-mutant cohorts developed malignancy within two years. Distinct effects of null and knock-in alleles caution against treating all model genotypes as interchangeable.
  evidence:
  - reference: PMID:18614044
    reference_title: Chk2 suppresses the oncogenic potential of DNA replication-associated DNA damage.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: roughly 40% of each cohort succumbing to malignancy within 2 years
    explanation: The tumor result concerns compound mutants, not isolated Chk2 loss.
  modeled_mechanisms:
  - target: Germline CHEK2 Loss of Function
    description: Deletes Chk2 with or without an additional damage-response defect.
    evidence:
    - reference: PMID:18614044
      reference_title: Chk2 suppresses the oncogenic potential of DNA replication-associated DNA damage.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: we generated Nbs1ΔB/ΔB Chk2−/− and Mre11ATLD1/ATLD1 Chk2−/− mice.
      explanation: The experimental design separates single and compound genotypes.
    relationship: PERTURBS
    model_scale: MOLECULAR
    limitations: Tumor predisposition in compound mutants cannot be attributed to heterozygous CHEK2 loss alone.
    fidelity: MODERATE
experimental_models:
- name: Chk2 1100delC mouse embryonic fibroblasts
  experimental_model_type: PRIMARY_CELL_CULTURE
  publication: PMID:19805189
  description: Fibroblasts from wild-type, heterozygous and homozygous knock-in mice provide protein and cell-cycle readouts. The original 2007 report supplies the instability assays; the 2009 follow-up supplies CDC25A measurements.
  modeled_mechanisms:
  - target: Increased CDC25A Abundance
    description: Measures increased Cdc25A protein.
    evidence:
    - reference: PMID:19805189
      reference_title: Mice with the CHEK2*1100delC SNP are predisposed to cancer with a strong gender bias.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: the levels of Cdc25A protein in the heterozygous cells are elevated compared with those in the wild-type cells and are even higher in the homozygous mutant cells.
      explanation: Western blotting of mouse embryonic fibroblasts directly supports genotype-associated abundance changes.
    relationship: PARTIALLY_RECAPITULATES
    model_scale: MOLECULAR
    limitations: Protein abundance is not a rescue test of causal mediation in cancer.
    fidelity: MODERATE
  - target: Model-Specific Genomic Instability
    description: Measures persistent damage and altered cell-cycle distribution.
    evidence:
    - reference: PMID:17174984
      reference_title: The breast cancer susceptibility allele CHEK2*1100delC promotes genomic instability in a knock-in mouse model.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: The mutant cells show signs of spontaneous genomic instability as indicated by polyploidy and an increase in DNA double strand breaks.
      explanation: The original knock-in study directly measures instability in derived fibroblasts.
    relationship: PARTIALLY_RECAPITULATES
    model_scale: CELLULAR
    limitations: Model-specific cellular findings do not establish BRCA-like HRD in human tumors.
    fidelity: MODERATE
- name: Chk2-null mouse fibroblast and thymocyte assays
  experimental_model_type: PRIMARY_CELL_CULTURE
  publication: PMID:18614044
  description: Irradiated fibroblasts and thymocytes distinguish checkpoint preservation from reduced apoptotic signaling and test interaction with Mre11-complex hypomorphism.
  modeled_mechanisms:
  - target: Attenuated CHK2 Damage Response Signaling
    description: Tests the remaining G2/M checkpoint response after Chk2 deletion.
    evidence:
    - reference: PMID:18614044
      reference_title: Chk2 suppresses the oncogenic potential of DNA replication-associated DNA damage.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Inhibition of the G2/M transition following DNA damage (the G2/M checkpoint), which is defective in Nbs1ΔB/ΔB and Mre11ATLD1/ATLD1 cultures, occurred normally in Chk2−/− MEFs 1 hour after IR treatment
      explanation: Primary knockout fibroblast assays demonstrate preservation of this checkpoint under the tested conditions.
    relationship: MEASURES
    model_scale: CELLULAR
    limitations: G2/M arrest remained intact under these conditions despite other CHK2-dependent defects.
    fidelity: MODERATE
  - target: Reduced Damage-Induced Apoptosis
    description: Measures proapoptotic target induction after irradiation.
    evidence:
    - reference: PMID:18614044
      reference_title: Chk2 suppresses the oncogenic potential of DNA replication-associated DNA damage.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: Whereas their induction was 30–50% of WT in Chk2−/−, Mre11ATLD1/ATLD1, and Atm−/− single mutants, Bbc3/Puma and Bax induction was similar to p53−/− in Mre11ATLD1/ATLD1 Chk2−/− double mutants
      explanation: Quantitative PCR after irradiation distinguishes single-mutant residual responses from the severe double-mutant defect.
    relationship: PARTIALLY_RECAPITULATES
    model_scale: CELLULAR
    limitations: The strongest defect occurs in compound-mutant thymocytes, not a human heterozygote.
    fidelity: MODERATE
- name: Recombinant CHK2 p.Ile157Thr biochemical assay
  experimental_model_type: OTHER
  publication: PMID:38367672
  description: Purified truncated recombinant CHK2 proteins were tested with a CDC25-derived peptide and varying ATP concentrations. Ile157Thr retained partial activity and had altered conformational stability. Heat-induced amyloid-like aggregation in vitro was not detected as amyloid deposition in the examined thyroid tissues.
  modeled_mechanisms:
  - target: Germline CHEK2 Loss of Function
    description: Measures partial missense dysfunction in a defined biochemical system.
    evidence:
    - reference: PMID:38367672
      reference_title: CHEK2 germline variants identified in familial nonmedullary thyroid cancer lead to impaired protein structure and function.
      supports: SUPPORT
      evidence_source: IN_VITRO
      quote_role: PRIMARY_RESULT
      directness: DIRECT
      snippet: At saturating ATP, the CHK2 p.I157T and p.E321A variants presented 40 to 50% of the WT CHK2 enzymatic activity
      explanation: Direct enzyme assay of residual activity.
    relationship: MEASURES
    model_scale: MOLECULAR
    limitations: A purified, truncated-protein assay cannot quantify cellular function, thyroid-cancer penetrance or clinical actionability.
    fidelity: MODERATE
  evidence:
  - reference: PMID:38367672
    reference_title: CHEK2 germline variants identified in familial nonmedullary thyroid cancer lead to impaired protein structure and function.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    quote_role: PRIMARY_RESULT
    directness: DIRECT
    snippet: amyloid deposition was undetected in both normal and tumor tissues
    explanation: The tissue analysis limits translation of the in-vitro aggregation observation.

📚