HIF1A and Ewing sarcoma: Thus, hypoxia enhances the expression and the transcriptional function of the fusion protein EWS/FLI1 in a HIF-1α dependent-manner in Ewing sarcoma cells and consequently increases their invasiveness [154], HIF-1α is also able to promote osteosarcoma cell proliferation and migration through activation of several signaling pathway including Akt and STAT3 signaling pathways [155,156].