Cyclin-dependent kinase 6–cyclin D1 complex (CDK6–cyclin D1)

The **cyclin-dependent kinase 6–cyclin D1 complex (CDK6–cyclin D1)** is a critical regulator of the cell cycle, particularly the G1/S phase transition. **CDK6** is a serine/threonine protein kinase activated by binding to **cyclin D1**; together, this complex phosphorylates key substrates such as the retinoblastoma protein (RB1), driving cell proliferation by releasing E2F transcription factors that promote G1-to-S phase progression[1][2][3][5]. Cyclin D1 has additional roles in DNA damage response and repair, both in complex with CDK6 and independently[1]. Dysregulation or overactivation of the CDK6–cyclin D1 complex is strongly implicated in oncogenesis, especially in breast cancer and certain lymphomas, making it an important therapeutic target[1][3]. Selective inhibitors—including palbociclib, ribociclib, and abemaciclib—block the kinase activity of this complex to halt tumor cell cycle progression[3]. Elevated levels of cyclin D1 or CDK6, or increased phosphorylation of RB1, may serve as biomarkers for response to CDK4/6 inhibitor therapy. Notable safety concerns with inhibitors targeting this complex include cytopenias, gastrointestinal adverse events, and potential toxicities in rapidly dividing normal cells[3].

Other names

CDK6/cyclin D1CDK6–CCND1 complexCell division protein kinase 6 with cyclin D1

Inhibition of kinase activity to prevent phosphorylation of the retinoblastoma protein (pRB), thereby blocking cell cycle progression from G1 to S phase