RRM2 and neoplasm: ABC294640, which prevents S1P signaling by selectively inhibiting SPHK2, has been shown to prevent tumor growth via downstream mechanisms involving the inhibition of dihydroceramide desaturase in prostate cancer cells [177], suppression of c-Myc and ribonucleoside-diphosphate reductase subunit M2 (RRM2) in pancreatic cancer cells [178], and the inhibition of telomerase stability in lung cancer cell lines [107].