EWSR1 and Ewing sarcoma: We therefore characterized the status of various molecules important in the IGF signaling pathway in four Ewing's sarcoma cell lines, investigated their response to the anti-IGF-1R antibody R1507, and explored the relationship between the EWS/FLI-1 fusion protein and the IGF machinery, including signaling molecules downstream of the IGF-1R in Ewing's sarcoma.