Retinoblastoma–E2F pathway (RB–E2F pathway)

The **Retinoblastoma–E2F pathway** (RB–E2F pathway) is a central molecular axis that regulates cell cycle progression, particularly the transition from the G1 to S phase. This pathway centers on interactions between the retinoblastoma (RB) family of tumor suppressor proteins (RB1, p107/RBL1, p130/RBL2) and the E2F family of transcription factors. In its non-phosphorylated state, RB binds to E2F transcription factors, repressing the transcription of genes necessary for DNA synthesis and S-phase entry[3][5][8]. When RB is phosphorylated by cyclin-dependent kinases (notably CDK4 and CDK6 complexed with cyclin D1), it releases E2F, which activates transcription of genes required for cell cycle progression[3][5][6]. The RB–E2F pathway is physiologically regulated but is commonly dysregulated in human cancers, resulting in uncontrolled cell proliferation and evasion of cell cycle checkpoints[1][5][6]. The pathway is therapeutically targeted by CDK4/6 inhibitors, and the status of its components (especially RB and E2F activity) is an important biomarker for prognosis and patient stratification in cancer therapy[2][4][6]. Disruption of this pathway contributes to tumorigenesis, altered response to therapy, and provides opportunities for targeted treatment strategies.

Other names

RB–E2F signalingRB pathwayE2F pathwayRetinoblastoma pathwayE2F–RB pathway

Inhibitors of cyclin-dependent kinases (CDK4/6) prevent phosphorylation of RB, maintaining RB's repressive effect on E2F and halting cell cycle progression at G1/S[6]. - Oncolytic viruses selectively replicate in cells with deregulated E2F activity due to dysfunctional RB, leading to targeted cell death[6].