<b>Objective:</b> Inflammatory bowel disease (IBD) is generally considered as a major risk factor in the progression of colitis-associated colorectal cancer (CAC). Previous studies have indicated that the composition of gut microflora may be involved in CAC induction and progress. <i>Bacteroides fragilis</i> (<i>BF</i>) is a Gram-negative anaerobe belonging to colonic symbiotic bacteria of the host. This study was aimed to investigate the protective role of <i>BF</i> in a colorectal cancer (CRC) model induced by azoxymethane (AOM) and dextran sulfate sodium (DSS) in germ-free (GF) mice. <b>Materials and methods:</b> Total 22 GF mice were divided into two groups: GF and BF group. Half of the GF mice were colonized with <i>BF</i> for 28 days before CRC induction by AOM/DSS. <b>Results:</b><i>BF</i> colonization increased animal survival (100%). Cecum weight and cecum/body weight ratio significantly decreased in BF/AOM/DSS group. Interestingly, there was a significant decrease in tumor number and tumor incidence in the BF/AOM/DSS group as compared to the GF/AOM/DSS group. The adenocarcinoma/adenoma incidence and histologic score were also decreased in the BF/AOM/DSS group. In addition, immunohistochemistry staining found decreased numbers of cell proliferation (PCNA) and inflammatory cell (granulocytes) infiltration in the colon mucosa of the BF group. The β-catenin staining in the BF/AOM/DSS group had fewer and weaker positive signal expressions. Taking together, the <i>BF</i> colonization significantly ameliorated AOM/DSS-induced CRC by suppressing the activity of cell proliferation-related molecules and reducing the number of inflammatory cells. <b>Conclusions:</b> Symbiotic <i>BF</i> may play a pivotal role in maintaining the gastrointestinal immunophysiologic balance and regulating anti-tumorigenesis responses.
|發行者||Taylor & Francis|