TP53 and cancer: WIP1 (PPM1D) is a type 2C Ser/Thr phosphatase (PP2Cδ) with oncogenic activities that exhibits amplification and overexpression in human cancers.26 WIP1 has multiple substrates, including p38, p53, MDM2, and DNA damage response mediators (ATM, Chk1, and Chk2).