CDK6 (Cyclin-Dependent Kinase 6): CDK6 is a protein that, when combined with D-type cyclins, plays a key role in regulating the cell cycle, especially the transition from the G1 to S phase. It is essential for cell proliferation and differentiation. Dysregulation of CDK6 has been associated with various cancers, making it an important target for cancer therapies, particularly in tumors with CDK6 overexpression or abnormal activity.