EDN1 and chondrosarcoma: VEGF, FGF2, endothelin-1 (ET-1) and hypoxia-inducible factor-1α (HIF-1α) expression and mitogen activated protein kinase (MAPK) signaling are significantly enhanced in G2 and G3 conventional chondrosarcomas compared to G1 chondrosarcomas [65,68,69,70,71,72].