Retinoblastoma-E2F pathway (Rb-E2F pathway)

The Retinoblastoma-E2F (Rb-E2F) pathway is a fundamental regulatory axis that governs the transition of cells from the G1 phase to the S phase of the cell cycle (Giacinti & Giordano, 2006, Oncogene). Under normal physiological conditions, the Retinoblastoma protein (Rb) acts as a tumor suppressor by binding to and inhibiting E2F transcription factors, which prevents the expression of genes required for DNA replication (Dick & Rubin, 2013, Nature Reviews Molecular Cell Biology). This repression is relieved when Cyclin-dependent kinases 4 and 6 (CDK4/6) phosphorylate Rb in response to mitogenic signals, causing it to release E2F and initiate the cell cycle (Sherr, 1996, Science). In many cancers, this pathway is "defective" due to mutations in the RB1 gene, loss of the p16INK4a inhibitor, or amplification of Cyclin D1, leading to constitutive E2F activity and uncontrolled cell proliferation (O'Leary et al., 2016, Nature Reviews Clinical Oncology). Therapeutic strategies targeting this pathway primarily involve CDK4/6 inhibitors, such as Palbociclib, which restore Rb-mediated repression to induce cell cycle arrest. Additionally, tumor cells with a defective Rb-E2F pathway are specifically targeted by certain oncolytic viruses that exploit the lack of cell cycle control to replicate selectively within malignant cells (Vanderweil et al., 2022, Frontiers in Oncology).

Other names

Rb-E2F axisRetinoblastoma signaling pathwayp16-CDK4/6-Rb-E2F pathwayRB-E2F regulatory axis

Inhibition of CDK4/6 to prevent the phosphorylation of the Retinoblastoma protein (Rb), thereby maintaining Rb-mediated repression of E2F transcription factors and inducing G1 cell cycle arrest.