Defective Intestinal Mucin-Type O-Glycosylation Causes Spontaneous Colitis-Associated Cancer in Mice

Background & Aims Core 1– and core 3–derived mucin-type O-linked oligosaccharides (O-glycans) are major components of the colonic mucus layer. Defective forms of colonic O-glycans, such as Tn antigen, frequently are observed in patients with ulcerative colitis and colorectal cancer, but it is not clear if they contribute to pathogenesis. We investigated whether and how impaired O-glycosylation contributes to the development of colitis-associated colorectal cancer using mice lacking intestinal core 1– and core 3–derived O -glycans. Methods We generated mice that lack the core 1– and core 3–derived intestinal O-glycans (DKO mice) and analyzed them, along with mice that lack the intestinal epithelial core 1 O-glycans (IEC C1galt1 - /- mice) or mice that lack core 3 O-glycans (C3 Gnt-/- mice). Intestinal tissues were collected at different time points and analyzed for levels of mucin and Tn antigen, development of colitis, and tumor formation using imaging, quantitative polymerase chain reaction, immunoblot, and enzyme-linked immunosorbent assay techniques. We also used cellular and genetic approaches, as well as intestinal microbiota depletion, to identify inflammatory mediators and pathways that contribute to disease in DKO and wild-type littermates (controls). Results Intestinal tissues from DKO mice contained higher levels of Tn antigen and had more severe spontaneous chronic colitis than tissues from intestinal epithelial cell (IEC) C1galt1 - /- mice, whereas spontaneous colitis was absent in C3GnT - /- and control mice. IEC C1galt1 - /- mice and DKO mice developed spontaneous colorectal tumors, although the onset of tumors in the DKO mice occurred earlier (age, 8–9 mo) than that in IEC C1galt1 -/- mice (approximately age 12 months). Antibiotic depletion of the microbiota did not cause loss of Tn antigen but did reduce the development of colitis and cancer formation in DKO mice. Colon tissues from DKO mice, but not control mice, contained active forms of caspase 1 and increased caspase 11, which were reduced after antibiotic administration. Supernatants from colon tissues of DKO mice contained increased levels of interleukin-1β and interleukin-18, compared with those from control mice. Disruption of the caspase 1 and caspase 11 genes in DKO mice (DKO/ Casp 1/11 - /- mice) decreased the development of colitis, characterized by reduced colonic thickening, hyperplasia, and inflammatory infiltrate, compared with DKO mice. Conclusions Impaired expression of O-