TARGETING ENZYMES OF SPHINGOLIPID METABOLISM IN TREATMENT OF COLORECTAL CANCER

Abstract

Alterations in sphingolipid (SL) metabolism can contribute to cancer progression as well as chemotherapy resistance. Thus, the enzymes of SL metabolism are exploitable targets for the development of novel therapeutics. Colorectal cancer (CRC) cells characteristically have elevated levels of glucosylceramide synthase (GCS), acid ceramidase (AC), and sphingosine kinase 1 (SPHK1) enzymes that can contribute to cancer cell growth. For this reason, we were interested in determining the impact of inhibitors of SL enzymes on human CRC cell viability. The effects of our pharmacological inhibitors on CRC cell growth were investigated using a standard 96-well viability assay. Potency was gauged by evaluating inhibitor IC50 values (the half-maximal inhibitory concentration, meaning the dose required to kill 50% of the cells). The human CRC cell lines, LoVo and HT-29, were employed in all experiments. GCS inhibitors used were PPMP, Eliglustat, and PDMP. AC inhibitors included DM-102 and SACLAC, whereas the SPHK1 inhibitors tested were FTY-720, SK1-I, and PF-543. The most promising results were obtained in experiments using the HT-29 cell line. In HT-29 cells, FTY-720 was the most potent SPHK1 inhibitor, with an IC50 value of 7.0 µM. GCS was another enzyme that was effectively suppressed, in this instance by introduction of PPMP (IC50 = 3.5 µM). Finally, of the two AC inhibitors, SACLAC demonstrated the highest potency (IC50 = 9.5 µM). Of the enzymes assessed, our results suggest that pharmacological inhibition of GCS is the most promising strategy for inhibition of CRC cell growth.