EWSR1 and Ewing sarcoma: Published data has shown that EWS-FLI1 low cells typically represent only a minority of the cells within Ewing tumors (1–2% [14]) and we have now shown that EWS-FLI1 low cells can upregulate PD-L1 and PD-L2 expression and undergo enhanced T-cell mediated tumor cell apoptosis in response to blocking PD-1.