Cyclin-dependent kinase 4 (CDK4) is a gene that encodes a protein that is a member of the serine/threonine kinase family. The protein functions in the progression of the cell cycle at from G1 to S phase and the activation of RB1. Missense and silent mutations are observed in cancers such as endometrial cancer, intestinal cancer, and skin cancer.

CDK4 is altered in 2.39% of all cancers with sarcoma, non-small cell lung carcinoma, malignant glioma, breast carcinoma, and melanoma having the greatest prevalence of alterations

Amplification of the chromosomal region that includes CDK4 is commonly seen in gliomas and several subgroups of sarcomas, and may also occur in other tumors such a malignant melanomas.