This is a mechanism module, not a specific disease. Disorder entries reference individual nodes via conforms_to (for example, "rtk_grb2_signaling_adaptation#GRB2 Adaptor Hub"). The module is intended for RTK-driven cancers and signaling disorders where EGFR, ERBB2/HER2, FGFR, MET, KIT, ROS1, or related receptors converge on GRB2-mediated effector signaling. It also provides a bridge to DNA-damage and immunotherapy hypotheses when tumor-specific evidence supports GRB2-dependent replication fork protection or PARP-inhibitor/STING coupling.
Canonical RTK-GRB2 Effector Signaling Model
canonical_rtk_grb2_effector_model
CANONICAL
Evidence: 1
Evidence balance
1 support
Activated receptor tyrosine kinases recruit GRB2-containing adaptor complexes that connect receptor phosphorylation to RAS-MAPK and PI3K-AKT signaling outputs.
GRB2 Replication-Fork Protection Model
grb2_replication_fork_protection_model
EMERGING
Evidence: 1
Evidence balance
1 support
GRB2 also functions in the nucleus to stabilize RAD51 at stalled replication forks, suppressing fork degradation, cytosolic DNA release, and innate immune activation under replication stress or PARP inhibition.
Which tumor states switch GRB2 from a cytoplasmic RTK adaptor role into a nuclear RAD51 replication-fork protection role, and does that switch predict combined PARP-inhibitor and immunotherapy response?
KNOWLEDGE GAP
OPEN
gap_grb2_cytoplasmic_nuclear_switch
Attached to:
GRB2 Adaptor Hub
GRB2-Mediated Replication Fork Protection
The module now captures both GRB2 signaling and DNA-repair functions, but disease entries will need tumor-specific evidence to decide whether these are parallel functions, sequential stress states, or distinct patient subtypes.
Proposed experiments:
Isogenic GRB2 RTK-DDR state-switch perturbation assay
Activated RTK Phosphotyrosine Docking
trigger
Ligand binding, mutation, amplification, fusion, or autocrine stimulation activates an RTK, promoting receptor dimerization and tyrosine phosphorylation. The phosphorylated receptor tail creates docking sites for adaptor proteins and cytoplasmic substrates.
Downstream
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GRB2 Adaptor Hub
Activated RTKs recruit GRB2-containing adaptor complexes at phosphotyrosine docking sites.
Show evidence (1 reference)
"This activates the kinases, which then bind adaptor proteins and phosphorylate cytoplasmic substrates, triggering downstream signalling cascades that control cell growth and differentiation202122."
Supports the receptor activation and adaptor-docking trigger that starts the GRB2 signaling cascade.
GRB2 Adaptor Hub
central effector
GRB2 is the adaptor control point that links phosphorylated receptors and scaffold proteins to downstream signaling complexes. In cytoplasmic RTK signaling it recruits effector complexes that activate RAS-MAPK and PI3K-AKT pathways; in stressed tumor cells, GRB2 can also participate in nuclear DNA repair and replication-fork protection.
Downstream
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RAS-MAPK and PI3K-AKT Proliferation Output
Cytoplasmic GRB2 adaptor complexes activate canonical RAS-MAPK and PI3K-AKT proliferative and survival signaling.
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GRB2-Mediated Replication Fork Protection
Nuclear GRB2 stabilizes RAD51 at stalled replication forks under replication stress.
Show evidence (2 references)
"Signaling by FGFR4 and other fibroblast growth factor receptors involves tyrosine phosphorylation of the receptor carboxyl terminus along with other substrates, such as FRS2, recruitment of the GRB2 adaptor, and activation of the downstream RAS and phosphoinositide 3-kinase pathways."
Directly supports GRB2 recruitment as the adaptor step between RTKs and RAS/PI3K effector signaling.
"Growth factor receptor-bound protein 2 (GRB2) is a cytoplasmic adapter for tyrosine kinase signaling and a nuclear adapter for homology-directed-DNA repair."
Supports GRB2 as a dual-function hub spanning cytoplasmic RTK signaling and nuclear DNA repair.
RAS-MAPK and PI3K-AKT Proliferation Output
effector
GRB2-dependent adaptor signaling propagates through RAS-MAPK and PI3K-AKT pathways, increasing cell-cycle progression, proliferation, and survival. In tumors, this output can create oncogene addiction as well as adaptive bypass routes after targeted therapy.
Downstream
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GRB2 Loss PARPi-STING Vulnerability
Proliferative RTK contexts can impose replication stress, making the nuclear GRB2 fork-protection branch therapeutically relevant.
Show evidence (1 reference)
"Overall, these findings in RMSp and RMSn indicate that the FGFR4 pathway is commonly activated in RMS. Though the clinical significance of these findings is not yet known, the FGFR4 signaling pathway provides an important new set of therapeutic targets relevant to a large number of RMSp and RMSn cases."
Establishes RTK-GRB2 effector signaling as a clinically relevant therapeutic target architecture in RTK-driven cancer contexts.
GRB2 Loss PARPi-STING Vulnerability
therapeutic vulnerability
GRB2 depletion or functional loss under PARP inhibition releases stalled fork-derived DNA fragments into the cytoplasm, activating cGAS-STING and pro-inflammatory cytokine production. This creates a potential therapeutic vulnerability for combining GRB2 targeting, PARP inhibition, and immunotherapy in selected tumors.
Show evidence (2 references)
"In GRB2-depleted cells, PARP inhibitor (PARPi) treatment releases DNA fragments from stalled forks into the cytoplasm that activate the cGAS-STING pathway to trigger pro-inflammatory cytokine production."
Directly supports the therapeutic-vulnerability node linking GRB2 loss, PARP inhibition, cytosolic DNA, and innate immune activation.
"Moreover in a syngeneic mouse metastatic ovarian cancer model, GRB2 depletion in the context of PARPi treatment reduced tumor burden and enabled high survival consistent with immune suppression of cancer growth."
Mouse-model evidence supports the in vivo therapeutic implication of GRB2 depletion combined with PARP inhibition.