Microbiota-Immune Interactions in Ulcerative Colitis and Colitis Associated Cancer and Emerging Microbiota-Based Therapies.

Ulcerative colitis (UC) is a chronic autoimmune disorder affecting the colonic mucosa. UC is a subtype of inflammatory bowel disease along with Crohn's disease and presents with varying extraintestinal manifestations. No single etiology for UC has been found, but a combination of genetic and environmental factors is suspected. Research has focused on the role of intestinal dysbiosis in the pathogenesis of UC, including the effects of dysbiosis on the integrity of the colonic mucosal barrier, priming and regulation of the host immune system, chronic inflammation, and progression to tumorigenesis. Characterization of key microbial taxa and their implications in the pathogenesis of UC and colitis-associated cancer (CAC) may present opportunities for modulating intestinal inflammation through microbial-targeted therapies. In this review, we discuss the microbiota-immune crosstalk in UC and CAC, as well as the evolution of microbiota-based therapies.

Clostridium butyricum modulates gut microbiota and reduces colitis associated colon cancer in mice.

We investigate the effects of Clostridium butyricum(CB) on gut microbiota and colitis associated colon cancer(CAC) in mice.6-8 weeks old C57BL/6 mice were randomly divided into control, azoxymethane (AOM) + dextran sodium sulphate (DSS) and AOM + DSS + CB groups. Mice in the latter two groups received an intraperitoneal injection of AOM (12.5 mg/kg), followed by three cycles of DSS diluted in water (2.5% w/v). Mice in treatment group received CB (2 × 108 CFU in 200 ul normal saline) by gavage administration three times one week. Microbiota composition was assessed by 16S rRNA high-throughput sequencing. Colon samples were collected to examine severity of colitis and tumorigenesis. Cytokines including TNF-a, IL-6 and Cyclo-oxygenase-2 (COX-2) were detected by RT-qPCR. Expression of Bcl-2, Bax and the state of components of NF-κB signaling pathway were detected by western blot. The results revealed that CB regulated structure of intestinal flora and changed the microbial composition; decreased Firmicutes/ Bacteroidetes ratio in phylum level and increased the relative abundance of probiotics; decreased colitis, decreased incidence and size of colorectal cancer(CRC) and increased apoptosis of tumor cells; decreased cytokines including TNF-a and IL-6; decreased level of COX-2; decreased phosphorylation of NF-κB; decreased level of Bcl-2 and increased expression of Bax. In conclusion, CB could regulate structure and composition of gut microbiota and reduces colitis associated colon cancer in mice, the mechanism may be inhibiting NF-κB pathway and promoting apoptosis.