PPM1D and acute myeloid leukemia: During our initial characterization of WIP1 inhibitor’s cellular activity [33], we noted that sensitive cell lines fell within two broad categories: (i) hematological malignancies with a high frequency of wild-type TP53 but normal PPM1D copy number and expression, exemplified by AML, and (ii) those derived from solid tumors with both wild-type TP53 and aberrantly high WIP1 levels.