SPHK1 and gastric cancer: Ectopic expression of SphK1 in MGC-803 cells markedly enhanced their resistance to apoptosis induced by UV irradiation, a commonly used model to study radiotherapy, whereas suppressing SphK1 expression with shRNAs markedly abrogated the ability of MGC-803 cells to resist UV-induced cell death, suggesting that SphK1 contributes to sustaining the unwanted survival of gastric cancer cells under radiotherapy.