MBTPS1 and neoplasm: As such, they control cell fate by regulating the relative amounts of pro-apoptotic Cer and Sph to pro-survival S1P.6 S1P acts extracellularly as a ligand to S1P receptors, leading to increased tumor cell migration and proliferation.7,8 Thus, blocking SK with a specific inhibitor would not only decrease the levels of S1P and hence tumor migration, but also lead to an increase in Cer and Sph, thereby inducing cell death.