Generating p53−/− sarcomatous tumors is also germane, as the MDM2-p53 pathway is one of the most frequently mutated pathways in STS, with deep deletions of p53 being common in leiomyosarcoma, undifferentiated pleomorphic sarcoma, and myxofibrosarcoma9. Here, TP53 is linked to undifferentiated pleomorphic sarcoma.