Bergstrom K.,Oklahoma Medical Research Foundation |
Liu X.,Central South University |
Zhao Y.,Oklahoma Medical Research Foundation |
Zhao Y.,Soochow University of China |
And 23 more authors.
Gastroenterology | Year: 2016
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 the Thomsen-nouveau (Tn) antigen, frequently are observed in patients with ulcerative colitis and colorectal cancer, but it is not clear if they contribute to their 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 core 1– and core 3–derived intestinal O-glycans (DKO mice) and analyzed them, along with mice that singly lack intestinal epithelial core 1 O-glycans (IEC C1galt1-/- mice) or core 3 O-glycans (C3Gnt-/- 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 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 months) than that in IEC C1galt1-/- mice (15 months old). 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/Casp1/11-/- mice) decreased the development of colitis and cancer, characterized by reduced colonic thickening, hyperplasia, inflammatory infiltrate, and tumors compared with DKO mice. Conclusions Impaired expression of O-glycans causes colonic mucus barrier breach and subsequent microbiota-mediated activation of caspase 1–dependent inflammasomes in colonic epithelial cells of mice. These processes could contribute to colitis-associated colon cancer in humans. © 2016 AGA Institute
Wang X.,The University of Oklahoma Health Sciences Center |
Huycke M.M.,The University of Oklahoma Health Sciences Center |
Huycke M.M.,The Muchmore Laboratories for Infectious Diseases Research
Gut Microbes | Year: 2015
For years the human microbiota has been implicated in the etiology of colorectal cancer (CRC). However, identifying the molecular mechanisms for how aneuploidy and chromosomal instability (CIN) arise in sporadic and colitisassociated CRC has been difficult. In this Addendum we review recent work from our laboratory that explore mechanisms by which intestinal commensals polarize colon macrophages to an M1 phenotype to generate a bystander effect (BSE) that leads to mutations, spindle malfunction, cell cycle arrest, tetraploidy, and aneuploidy in epithelial cells. BSE represents the application of a phenomenon initially described in the radiation biology field. The result of commensal-driven BSE on colon epithelial cells is aneuploidy, chromosomal instability (CIN), expression of stem cell and tumor stem cell markers and, ultimately, malignant transformation. Our findings provide a conceptual framework for integrating the microbiota with aging, cyclooxygenase (COX)-2, and inflammation as risk factors for CRC. © 2015 Taylor & Francis Group, LLC.
PubMed | The Muchmore Laboratories for Infectious Diseases Research
Type: Journal Article | Journal: Cancer research | Year: 2012
Macrophage-induced bystander effects have been implicated as an important mediator of chromosomal instability and colon cancer triggered by Enterococcus faecalis, a human intestinal commensal bacteria. There is little understanding about how inflammatory cytokines mediate bystander effects, but questions in this area are important because of the pivotal contributions made by inflammatory processes to cancer initiation and progression. Here, we report that the central proinflammatory cytokine TNF- acts as a diffusible mediator of the bystander effects induced by macrophages, an effect caused by a proliferation of macrophages that trigger epithelial cell production of Netrin-1, a neuronal guidance molecule. TNF--mediated bystander assays used a murine coculture system of primary colonic epithelial cells and E. faecalis-infected macrophages (in vitro), with an interleukin 10 (IL-10)-deficient mouse model of colon cancer that involves long-term colonization with E. faecalis (in vivo). In cell cocultures, we observed increased expression of the TNF- receptor Tnfrsf1b and Netrin-1. These effects were blocked by anti-TNF- antibody or by pretreatment with an inhibitor of NF-B signaling. RNAi-mediated attenuation of Tnfrsf1b decreased TNF--induced netrin-1 production and augmented epithelial cell apoptosis in culture. Extending these observations, colon biopsies from E. faecalis-colonized IL-10(-/-) mice exhibited crypt hyperplasia and increased staining for macrophages, TNF-, netrin-1, NF-B, Tnfrsf1b, and the proliferation marker proliferating cell nuclear antigen while also displaying a reduction in epithelial cell apoptosis. Together, our results define a pathway for macrophage-induced bystander effects in which TNF- triggers TNFRSF1b receptor signaling leading to increased production of Netrin-1, crypt hyperplasia, and decreased epithelial cell apoptosis. In elucidating an important commensal-associated proinflammatory mechanism in the intestinal microenvironment, our work highlights the role of Netrin-1 and a specific TNF- receptor as candidate targets to prevent or treat colorectal cancer.