EWSR1 and Ewing sarcoma: We chose the cell line A673 as a model to analyze the effect of EWSR1–FLI1 gene inactivation in Ewing sarcoma cells, since this cell line is probably the Ewing sarcoma cell line more broadly used to study Ewing sarcoma pathogenesis, particularly with regard to the mechanism of EWSR1–FLI1-mediated oncogenesis.