This is a mechanism module, not a specific disease. Disorder entries reference individual nodes via conforms_to (e.g., "evading_growth_suppressors#Loss of Cell-Cycle Checkpoint Control"). The module defines the expected pathophysiology structure; conforming nodes in disorder files should include the corresponding biological processes and causal edges, specialized to their tumor context. Key tumor-specific substitutions: retinoblastoma uses biallelic RB1 inactivation (the two-hit paradigm); Li-Fraumeni uses germline TP53 loss; many sporadic cancers use CDKN2A (p16INK4A) deletion or MDM2 amplification. The senescence arm of tumor suppression is elaborated in senescence_tumor_suppression. Key conformance target: "evading_growth_suppressors#Loss of Cell-Cycle Checkpoint Control".
Tumor Suppressor Inactivation
trigger
A genetic or epigenetic lesion inactivates an RB- or p53-axis tumor suppressor. Routes include biallelic loss of RB1, deletion or silencing of CDKN2A (encoding p16INK4A and p14ARF), amplification of cyclin D/CDK4-6 that hyperphosphorylates RB, loss-of-function mutation of TP53 (the most frequently mutated gene in human cancer), or amplification of the p53 antagonists MDM2/MDM4. Each route disables a node that normally enforces antiproliferative control.
Downstream
-
Loss of Cell-Cycle Checkpoint Control
Inactivation of the RB or p53 axis removes the brakes that gate cell-cycle progression and stress responses.
Show evidence (1 reference)
"The importance of p53 in tumour suppression is unequivocal, as shown by its inactivation in more than half of all sporadic human cancers"
Review establishing that p53 tumor-suppressor inactivation is a near-universal event in human cancer, supporting tumor-suppressor inactivation as the trigger of this module. Evidence source is OTHER because this is a review article.
Loss of Cell-Cycle Checkpoint Control
central effector
With the RB and/or p53 circuits disabled, the cell loses the antiproliferative checkpoints that normally halt division. RB-pathway loss permits unrestrained G1/S transit regardless of antigrowth signals; p53-pathway loss abolishes the stress-induced cell-cycle arrest, senescence, and apoptosis that would otherwise eliminate incipient tumor cells. This is the conserved central node disorder-specific lesions converge upon.
Downstream
-
Loss of Contact Inhibition
Disabled tumor-suppressor circuits also relax density-dependent restraints on proliferation.
-
Unrestrained Proliferation
Removal of antiproliferative checkpoints permits continued division of cells that should have arrested or died.
Show evidence (2 references)
"p53 is a crucial tumour suppressor that responds to diverse stress signals by orchestrating specific cellular responses, including transient cell cycle arrest, cellular senescence and apoptosis, which are all processes associated with tumour suppression."
Defines the antiproliferative checkpoint responses (arrest, senescence, apoptosis) whose loss is the central effector of this module. Evidence source is OTHER because this is a review article.
"They include sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis."
Hanahan & Weinberg list evading growth suppressors as a core hallmark capability modeled here. Evidence source is OTHER because this is a review article.
Unrestrained Proliferation
consequence
The combined loss of cell-cycle-checkpoint control and contact inhibition yields unrestrained proliferation: cells divide despite antigrowth signals, high density, and intracellular stress that would normally trigger arrest or death. This is the defining phenotype of the evading-growth-suppressors hallmark.
Used by disorders
Ependymoma
as Uncontrolled Tumor Cell Proliferation