SPHK1 and prostate carcinoma: In pCan1 and pCan2 primary prostate cancer cells SKI-178-induced SphK inhibition (Fig. 5K), viability (CCK-8 OD) reduction (Fig. 5L), cell death (Trypan blue staining assays, Fig. 5M) and apoptosis (TUNEL-positive nuclei ratio increase, Fig. 5N) were significantly more potent than the same concentration of PF-543 and ABC294640.