RB1 and sarcoma: We have previously developed and characterized sarcoma models using human bone marrow MSCs (BM-MSCs) sequentially mutated with up to 6 oncogenic events [(1) hTERT overexpression; (2 & 3) P53 and Rb inactivation using E6 and E7 antigens of the HPV-16; (4) inactivation of PPA2 phosphatase with SV40 small T antigen (4 hits combination; MSC-4H); (5) expression of oncogenic H-RASv−12 (5 hits combination; MSC-5H); and (6) the expression of FUS-CHOP (FC)] (Table S1)38, 39, 40.