IL17A and colorectal carcinoma: The study found that the colonic commensal bacteria Bacteroides fragilis [100], which is closely related to mucosal colonisation, is associated with acute diarrheal disease, inflammatory bowel disease and CRC [101–103], In particular, high levels of Bacteroides fragiles toxin genes (BFT) have been found in advanced CRC [104], and this toxin can stimulate the production of interleukin 17 (IL-17), a proinflammatory cytokine, and thus induce inflammation.