Chronic intestinal inflammation has also been associated with the development of colorectal cancer (CRC) and the increased involvement of Bacteroides fragilis and Streptococcus bovis, activating immune cells to release pro-mitogenic and pro-angiogenic cytokines such as Interleukin-17 (IL-17) and the synthesis by the gut microbiota of metabolites involved in carcinogenesis such as secondary transformations of bile salts, desulphurization of bile acids, synthesis of aromatic amines by azoreductase and nitroreductase, formation of reactive oxygen species [19]. This evidence concerns the gene IL17A and colorectal cancer.