SPHK1 and cancer: Although AC, SPHK, and the ceramide-sphingosine-S1-P axis are important targets for regulating cancer cell growth [5,18,19,21,33,112,113,114,115,116,117,118], and their dysregulation in cancer makes for exciting research [119], herein we will focus on GCS, the enzyme catalyzing glycosylation of ceramide [120,121,122], and its role in chemotherapy resistance.