PPM1D and medulloblastoma: Wip1 overexpression could negatively affect tumor characteristics in p53-positive cancers, such as breast cancer, neuroblastoma, medulloblastoma, ovarian clear cell tumor, gastric carcinoma, pancreatic adenocarcinoma and chronic lymphocytic leukemia.11, 12 Moreover, Wip1-deficient mice have shown a tumor-resistant phenotype strictly dependent on the presence of wild-type p53.13, 14 Wip1 overexpression induces opposite effects depending on the p53 status of the cell.