Interestingly, in contrast to classical chemotherapy, the dual SphK1 and S1P1 inhibitor FTY720 remarkably reduced cell proliferation to the same extent in normoxic and hypoxic conditions in all osteosarcoma cell lines, suggesting that efficacy of FTY720 was related to its anti-HIF-1α effect. This evidence concerns the gene SPHK1 and osteosarcoma.