EWSR1 and Ewing sarcoma: Thus, the regulation of cyclin D1 expression in Ewing sarcoma cells results from the mutually exclusive binding of two different complexes to the CCND1 promoter: one composed by EWS-FLI1 and DHX9, promoting cyclin D1 expression, and a repressive complex formed by Sam68, DHX9, and pncCCND1_B [19,22].