KRAS and medulloblastoma: TP53 deficiency is related to high incidences of human malignancies including lymphomas, soft-tissue carcinomas, or even Li-Fraumeni syndrome; therefore, TP53 KO mice have been used as a genetic background model for specific cancers, including glioma, ovarian cancer, medulloblastoma, and lung cancer by modulating genes of interest such as KRAS, NF1, or MYC [27–30].