CDKN2A and neoplasm: Tumor cells retaining wild-type p53 can attenuate its function by deregulating genes involved in p53 regulation such as MDM2 and ARF (CDKN2A), or the DNA damage kinases ATM, ATR, DNA-PKcs (PRKDC), CHK1 (CHEK1), and CHK2 (CHEK2).