FLI1 and Ewing sarcoma: It has also been shown that EWS-FLI1, the genetic hallmark of Ewing sarcoma, is only capable of transformation in the presence of IGF-1R [43] and, more recently, that this fusion product directly affects IGF-1R signalling either by downregulating IGFBP3 [17], increasing IGF1 promoter, or both [44].