Retinoblastoma protein (RB or pRb)

The **retinoblastoma protein (RB; pRb)** is a central tumor suppressor encoded by the RB1 gene on chromosome 13q14. It is a crucial inhibitor of cell cycle progression at the G1/S checkpoint through binding and inhibition of E2F transcription factors. Its functional inactivation—by mutation, deletion, or hyperphosphorylation—leads to unchecked cell proliferation and is a hallmark of many human cancers, including retinoblastoma, breast cancer, and lung cancer[1][2][3][4][6]. The "RB pathway" commonly refers to the network of cell cycle regulatory proteins involving cyclin D, CDK4/6, INK4 family inhibitors, and E2F transcription factors; collective deficiencies in this pathway promote tumorigenesis, and such deficiencies guide patient selection for CDK4/6 inhibitors and other therapies.

Other names

RBpRbRB pathwayRB1 (gene)Retinoblastoma susceptibility protein

CDK4/6 inhibitors: maintain RB in its active, hypophosphorylated, functional tumor suppressor state, thereby arresting cell cycle in G1; Epigenetic drugs: reactivate silenced RB pathway components (e.g., via demethylation/reactivation of p16INK4A)