SPHK1 and mesothelioma: In the present study, we also observed formation of intracellular S1P, the product generated by SphK1 activity under basal conditions; however, the ability to generate intracellular S1P when challenged with its substrate sphingosine was much higher in mesothelioma cell lines (>3X) compared to Met5A control cells (Fig. 2) that can be attributed to the significant amounts of SphK1 expressed (Fig. 1).