ARAF and colorectal cancer: For instance, the CagA toxin, VacA toxin, and type IV secretion system encoded in the Helicobacter pylori pathogenicity island (50, 51) or the colibactin synthase genes encoded in the E. coli polyketide synthase (pks) genotoxic island (52, –, 54) are key to the progression of gastric cancer and colorectal cancer, respectively.