CDK4CDK6

CDK4CDK6 refers to a complex formed by cyclin-dependent kinase 4 (CDK4) and cyclin D6 (CCND6). This complex is a key regulator of the cell cycle, specifically the transition from the G1 phase to the S phase, which is crucial for DNA replication and cell division. CDK4 and CDK6 are members of the cyclin-dependent kinase family, a group of enzymes essential for controlling cell proliferation. They partner with D-type cyclins, including CCND1, CCND2, and CCND3, to form active holoenzymes. While CCND6 is less commonly studied in this context than other D-type cyclins, the formation of CDK4/CCND6 complexes contributes to the overall regulation of cell cycle progression. When activated, the CDK4/CCND6 complex phosphorylates the retinoblastoma protein (Rb). This phosphorylation event releases transcription factors that promote the expression of genes required for DNA synthesis, thereby driving the cell into the S phase. Dysregulation of CDK4/CDK6 activity, often due to overexpression of D-type cyclins or mutations in CDK inhibitors, is frequently observed in various cancers. This aberrant activation can lead to uncontrolled cell proliferation and tumor development. Consequently, CDK4 and CDK6 have become significant targets for cancer therapy, with several inhibitors developed and approved for treating certain types of breast cancer. These inhibitors work by blocking the kinase activity of the CDK4/CDK6 complex, thereby halting the cell cycle in the G1 phase and preventing cancer cell proliferation.