Altered intestinal microbiota associated with the development of colorectal cancer

The gut microbiota play a role in the development and progression of colorectal cancer (CRC). As most CRC develops from polyps, we assessed alterations in gut microbiota in patients with polyps and CRC to learn more about the early events of carcinogenesis. A total of 28 subjects were enrolled in this study: nine had CRC (CRC group), five had polyps (polyp group) and 14 had normal colons (normal group). The microbiome of the mucosal-luminal interface from each subject was sampled and analysed using 16S rRNA gene amplicon sequencing. The microbial composition of the mucosal lumen was different among the groups, and the presence of specific bacteria may serve as a potential biomarker for colorectal carcinogenesis. A gradual increase in the proportion of Fusobacteria was detected from the normal to polyp to CRC groups, whereas Clostridium perfringens was higher in the normal group than that observed in the polyp and CRC groups. We identified a significant reduction in Eubacterium, which belongs to the butyrate-producing genera of bacteria, in the gut microbiota of CRC patients. Furthermore, a significant increase in Devosia was also observed in the CRC group. Different levels of gut microflora diversities in healthy, polyp and CRC samples were identified. In addition to Fusobacterium, the observed abundance of bacterial species belonging to Eubacterium, Devosia and Clostridium may also be promising biomarkers for the early detection of CRC.