In this study, we determined the prevalence of E. coli harboring the pks and cnf1 genes in CRC patients and investigated the tumorigenic properties of E. coli strain 21F8 isolated from a human colon cancer biopsy and producing both colibactin and CNF1 in comparison with those of isogenic mutants using human intestinal epithelial HT-29 cells and an ApcMin/+ mouse model of CRC. The gene discussed is ARAF; the disease is colorectal carcinoma.