CDK6 and cancer: P16 (ink4a) is a cell cycle inhibitor that binds to cdk4 and cdk6 that inhibits pRb phosphorylation and inactivation (50).The down regulation of p16 (ink4a) is linked to the pathogenesis of cancers in various organs (51, 52).Yet, overexpression of p16 (ink4a) is usually found in premalignant cervical lesions and cancers (53).