Abstract 2387: The impact of beta 1,6-GlcNAc branched N -glycan synthesis on hexosamine pathway and UDP-GlcNAc demands in colorectal cancer cells

Metabolic changes are commonly seen in cancer. Tumor cells present a high rate of glucose and glutamine uptake and part of these nutrients supplies the hexosamine biosynthesis pathway (HBP), whose exacerbation has been related to solid tumors progression, including colorectal cancer. Uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), the end product of HBP, serves as the donor for several enzymes involved in glycan biosynthesis. Aberrant glycosylation is known to affect cellular and molecular mechanisms related to the malignant phenotype. Beta 1,6-GlcNAc branches on N-glycans (products of the MGAT5 enzyme) are associated with greater stability of transmembrane glycoproteins, as glutamine and glucose transporters, and growth factor receptors. Furthermore, changes in the availability of UDP-GlcNAc can affect the levels of hyaluronic acid (HA) and O-GlcNAc-modified proteins. The interplay between different direct demands for UDP-GlcNAc is not well understood and may help to better understand tumor metabolism. Therefore, we intend to evaluate in colorectal cancer cells how changes in levels of branched beta1,6-GlcNAc N-glycans can affect both the hexosamine pathway and the different processes which demand UDP-GlcNAc (such as O-GlcNAcylation and hyaluronic acid synthesis). For this, two experimental strategies were performed. The first focused on the inhibition of complex N-glycans using swainsonine, and the second focused on the MGAT5 inactivation using CRISPR-Cas9. The levels of UDP-GlcNAc were also manipulated using DON, an inhibitor of the GFAT enzyme. Initially, it was found that both the pharmacological inhibition of complex N-glycan biosynthesis and the specific inactivation of MGAT5 lead to significantly reduced levels of hexosamine pathway intermediates, activated monosaccharides, and proteins modified by O-GlcNAc. Furthermore, it was also observed that MGAT5 inactivation enhances the expression of genes encoding HA synthases (HAS2 and HAS3). Upon detection of metabolites by LC-MS, a multivariate analysis was performed using the statistical method of Partial Least-Squares Discriminant Analysis (PLS-DA), and it was observed that KO MGAT5 cells formed a metabolically distinct population from MOCK cells. Interestingly, after pharmacological inhibition of GFAT, an increase in the levels of beta 1,6-GlcNAc branched N-glycans and a reduction in O-GlcNAcylation were observed. Treatment with DON was also able to reduce HAS2 expression however an increased i