SPHK1 and melanoma: Consistent with our observations, the suppression of SPHK1 in melanoma cell lines in vitro, either by treatment with PF543 (Fig. 4c–e) or with an SPHK1-targeting short interfering RNA (siRNA; Fig. 4f and Supplementary Fig. 7a, b), produced reductions in the MTA3 and c-Myc expression levels.