CIB1 and cancer: p21 is a member of the cip/kip family of CDK inhibitors.56CDKN1A/p21 and other cell cycle control genes have previously been identified to be targets of EZH2/H3K27me3 in other cancers, including breast, prostate, endometrial, melanoma and non-Hodgkin's lymphoma.26 p21 is known to be a major target for transactivation by the tumour-suppressor gene p53 and is required for p53-dependent G1 and G2 arrest.57, 58 It has also previously been demonstrated to act independently of p53, as a tumour-suppressor gene in its own right,56 as is demonstrated by our results.