SPHK2 and ovarian cancer: Dai et al. [42] showed that SPHK1, but not SPHK2, expression was correlated with microvascular density (MVD) of ovarian cancer cells and that the angiogenic factor secretion by ovarian cancer cells could be attenuated by SPHK1, but not SPHK2 inhibition and subsequently restored upon addition of S1P.