Cyclooxygenase-2 (COX-2) in Carcinogenesis and Selective COX-2 Inhibitors for Chemoprevention in Gastrointestinal Cancers

Abstract

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been reported to have a property to inhibit tumor development in some cancers while it shows various side effects such as gastrointestinal bleeding and renal disorder. Selective cyclooxygenase (COX)-2 inhibitors (coxibs) were originally developed as one of anti-inflammatory drugs to avoid side effect of NSAIDs. Fortunately, the coxibs was also proved to have an inhibiting effect on tumorigenesis by many experimental studies using cell lines and animal models like NSAIDs. Since a randomized study for polyp chemoprevention by celecoxib in familial adenomatous polyposis (FAP) patients demonstrated a significant reduction in the number of colorectal polyps, the clinical use of celecoxib was approved for FAP patients. Three large trials using celecoxib (the Adenoma Prevention with Celebrex and the Prevention of Spontaneous Adenomatopus Polyps) or refecoxib (the Adenomatous Polyp Prevention on Vioxx) for the recurrence of colorectal polyps in patients with a history of colorectal adenoma polypectomized confirmed chemopreventive effects on colorectal adenoma but two of three trails alerted us a hazard of cardiovascular (CV) events. Thereafter, some coxibs were withdrawn from the market because they showed to increase risk of serious CV events including heart attacks and strokes. But recent reports concluded that a merit of the reduction in gastrointestinal events by coxibs exceeded a demerit of the increase in serious CV events. In this review, a role of COX-2 in carcinogenesis of gastrointestinal tract and a future of coxibs for chemoprevention are discussed.