Using the AOM-DSS model, we have previously described that mice deficient in toll-like receptor 4 (TLR4), a pathogen recognition receptor specific for gram-negative bacteria, are resistant to the development of colitis-associated tumors due to decreased expression levels of mucosal cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), and amphiregulin (AR), a ligand of the epidermal growth factor receptor (EGFR). This evidence concerns the gene PTGS2 and colitis.