Cyclin D1 protein (Cyclin D1)

Cyclin D1 is a regulatory subunit belonging to the highly conserved cyclin family. It forms complexes with cyclin-dependent kinases 4 and 6 (CDK4/6), which are essential for driving the transition from G1 to S phase during the eukaryotic cell cycle. The Cyclin D–CDK4/6 holoenzyme phosphorylates members of the retinoblastoma tumor suppressor family—including pRb—leading to their functional inhibition and allowing progression through the restriction point into DNA synthesis. Dysregulation—through gene amplification or overexpression—of Cyclin D1 is frequently observed in various human cancers such as breast carcinoma and mantle cell lymphoma; it plays a pivotal role in oncogenesis by promoting uncontrolled cellular proliferation. Beyond its canonical role as a CDK regulator, Cyclin D1 also modulates transcription factor activity and influences processes like metabolism and migration. Clinically relevant drugs such as palbociclib inhibit this pathway by targeting associated kinases. Immunohistochemical detection serves as a diagnostic biomarker for certain lymphomas.

Other names

CCND1G1/S-specific cyclin-D1BCL1 (historical, in context of chromosomal translocation)PRAD1 (parathyroid adenomatosis 1)

Inhibition of CDK4/6 activity to block phosphorylation/inactivation of retinoblastoma protein and arrest cell cycle at G1 phase