RB1 and undifferentiated pleomorphic sarcoma: However, conversely to what reported in myxofibrosarcoma (MFS) and undifferentiated pleomorphic sarcoma (UPS)17, in our cancer context the effects of SKP2 inhibition appear to be, at least in part, unrelated to the mutational status of p53 and pRb since similar functional effects were seen in both p53-mutated and p53 wild-type FN-RMS cells and PDX.