FLI1 and Ewing sarcoma: The EWSR1-FLI1 fusion gene is thought to function as a regulator of the expression of insulin-like growth factor 1 (IGF1), and overexpression of IGF1 receptor (IGF1R) is observed in Ewing sarcoma cells [79]; the IGF1R pathway could thus be a target in Ewing sarcoma cases.