PO-465 N-glycans of pseudomyxoma peritonei present highly increased fucosylation and multifucosylation correlates with high-grade morphology

Introduction Pseudomyxoma peritonei (PMP) is a fatal clinical syndrome, where most often appendix-originating mucinous adenocarcinoma cells grow in the peritoneal cavity filling it with mucinous ascites. KRAS mutations are found in nearly all PMPs and GNAS mutations in over half of the cases, but other common driver mutations are infrequent. As glycosylation alterations can also contribute to carcinogenesis, our aim was to compare the N-linked glycan profiles of PMP tissue specimens to those of normal appendices. Material and methods N-glycans were detached from formalin-fixed, paraffin-embedded tissue specimens of 8 normal appendices and 8 low-grade and 8 high-grade PMPs, and analysed by mass spectrometry. The expression levels of glycosylation-related genes were further analysed from PMP microarray data, and the expression of fucosylation-related enzymes and fucosylated glycans was localised by immunohistochemistry and lectin histochemistry. Finally, cell culture experiments were used to study the relationship between fucosylation and mucin expression. Results and discussions The N-glycan profiles, especially those of neutral glycans, clearly differed between PMPs and normal control samples. The most prominent alteration in PMP was highly increased fucosylation and multifucosylation further showed correlation with the proportion of high-grade morphology in the sample. From microarray data we could demonstrate upregulated mRNA expression of four fucosylation-related enzymes (FUT8, GMDS, GMPPA, and TSTA3) in PMP specimens, and by immunohistochemistry we localised these enzymes into PMP cells. Finally, by using colon carcinoma cell line HCT116 with inherently defective fucosylation, we demonstrated that restoration of fucosylation enhanced GNAS mutation-induced upregulation of MUC2 expression. Conclusion PMPs show highly increased N-glycan fucosylation as compared to normal appendices, and this glycosylation alteration may be linked to the characteristic mucin overexpression of the disease. Most importantly, multifucosylation correlates with the proportion of high-grade morphology in the specimen and this glycan class may thus provide structures bearing prognostic potential.