IGF1 and Ewing sarcoma: In contrast to other tumors in which the effect of IGF2BP3 on the IGF system is primarily mediated by IGF2 mRNA regulation (4, 20), in ES, IGF2BP3 mainly affects IGF1R. The expression of IGF1R and IGF2BP3 are correlated in clinical ES samples, while in experimental models, although the small number of independent experiments suggests caution in the interpretation of the data, we demonstrated that IGF2BP3 can bind to and stabilize IGF1R mRNA, favoring the expression of the receptor and its functions.