SPHK1 and cancer: This hypothesis appears to be generally accurate on the basis of current evidence, but may need to be reconsidered in terms of how ceramide metabolism (including its conversion to S1P) fits into the broader context of lipid metabolism; and in light of recent data showing firstly that different ceramide variants appear to have very different roles in cell survival, autophagy, and metastasis, partly dependent on their cellular localisation [13]; and secondly that the most potent and selective SPHK1 inhibitors don’t affect cancer cell survival [14,15,16].