EWSR1 and Ewing sarcoma: Both EWS‐FLI1 and EWS‐ERG fusion proteins work as oncogenic transcriptional factors, and the knockdown of EWS‐FLI1 in Ewing's sarcoma cell lines showed inhibitory effects on the cell proliferation, anchorage‐independent growth, and tumor growth in vivo in a xenograft mouse model.5, 6