SMPD1 and malignant colon neoplasm: In this context, it is perhaps interesting that we have previously observed that induction of apoptosis in differentiating colon cancer cells is associated with up-regulation of CERS5 (which contributes primarily to Cer 16:0 production) and down-regulation of CERS2 (which contributes to Cer 24:1 production), as well as with deregulation of expression of other SL metabolism enzymes, namely with induction of sphingomyelin phosphodiesterase 1 (SMPD1) and down-regulation of dihydroceramide desaturase 2 (DEGS2) [15].