The cell cycle events are well coordinated resulting in proper DNA replication, leading to healthy daughter cells. The cell cycle is a frequent target of genetic alterations in cancer because of its central role in the control of cell growth and proliferation. The central players in the cell cycle machinery are Cyclin-Dependent Kinases (CDKs). CDKs are a family of heterodimeric serine/threonine kinases consisting of a catalytic CDK and an activating cyclin subunit. In mammals, there are different CDKs controlling different stages of the cell cycle and play the role of switch on/off on the cell cycle process. When on, the cell passes through the stage that the particular CDK controls, while when off, the cell cycle stops when it reaches th...