EWSR1 and Ewing sarcoma: One study, examining Ewing Sarcoma initiation in pediatric MSCs, identified miR-145 as an EWS/Fli1-repressed miR, and miR-145 repression, in turn, as a means to augment expression of EWS/Fli1 itself, as well as expression of the stemness-associated transcription factor Sox2 (Riggi et al., 2010).