Specific alterations of sphingolipid metabolism identified in EpCAM-positive cells isolated from human colon tumors

Metabolic reprogramming leading to alterations in lipid metabolism and lipid-mediated signaling may contribute to colorectal cancer (CRC) development and progression. We hypothesized that a detailed description of changes in sphingolipidome of specific cellular subpopulation residing in colon cancer tissue may help to discriminate between normal and transformed colon epithelial cells. Using HPLC-mass spectrometry, we analyzed the EpCAM-positive cells isolated from tumor and adjacent non-tumor tissues of colon cancer patients, aiming to identify potential lipid biomarkers specific for CRC. We then employed RT-qPCR-based methodology in order to analyze expression of SL metabolism-related genes in the isolated EpCAM-positive tumor cells and/or in unseparated colon tumor tissues. We observed significant changes in sphingolipid (SL) species in the EpCAM-positive tumor cells, with the accumulation of lactosylceramide (LacCer) being the most prominent. B4GALT5 and B4GALT6 genes were identified as two potential gene candidates contributing to LacCer accumulation. We further identified additional genes of SL and fatty acid metabolism (e.g. SPHK1, GBA2, NEU3, GLA, FASN, PLA2G10), which were significantly altered in colon tumor tissue. The present results indicate that the EpCAM-positive cells are a major contributor to LacCer accumulation in CRC tissue, and may help to identify novel CRC-specific lipid/gene biomarkers.