CDK4 and cancer: Cyclin D1 is a key protein to regulate the cell cycle which promote G1 phase into S phase by binding with CDK4 or CDK6, then phosphorylates and inactivates pRb proteins to regulate nuclear DNA synthesis and mitochondrial biogenesis 4, 5, and frequently overexpressed in many human cancer, such as breast cancer 6, pancreatic cancer 7, colorectal carcinoma 8, lung cancer 9, 10.