PTGS2 and Familial adenomatous polyposis: COX-2 inhibitors are stated to have no effect on gastric mucosal prostaglandin synthesis, to cause no acute injury, and to no chronic ulceration compared to placebo; at the same time, they were demonstrated as chemopreventive in clinical trials [153,154,155,156,157], particularly in patients with familial adenomatous polyposis (FAP) [157].