CD44 and Ewing sarcoma: By using the extensively studied A673/TR/shEF cell line [8], we showed that CD44 was dramatically upregulated upon EWSR1::FLI1 downregulation (that is, in the EWSR1::FLI1low phenotype), suggesting that CD44 is repressed by EWSR1::FLI1 in EWSR1::FLI1high Ewing sarcoma cells.