MDC1 and osteosarcoma: Furthermore, ATRX is usually mutated in 30% of osteosarcomas and is in fact considered to be one of the main drivers in osteosarcoma development, along with the following genes: TP53, RB1, BRCA2, BAP1, RET, MUTYH, ATM, PTEN, WRN, RECQL4, FANCA, NUMA1, and MDC1 [20,21].