Targeting cyclooxygenase-2 for prevention and therapy of colorectal cancer.

Cyclooxygenase-2 (COX-2) is an inducible enzyme that regulates prostaglandin synthesis and is overexpressed at sites of inflammation and in several epithelial cancers. A causal link for COX-2 in epithelial tumorigenesis was shown in genetically manipulated animal models of colon and breast carcinoma. Studies have elucidated the regulation of COX-2 expression and have identified EP receptors through which prostanoids exert their biological effects. Mechanistic studies indicated that COX-2 is involved in apoptosis resistance, angiogenesis, and tumor cell invasiveness, which appear to contribute to its effects in tumorigenesis. Furthermore, forced COX-2 expression has been shown to suppress apoptosis by modulating the level of death receptor 5 (DR5) and this effect was reversed by a COX inhibitor. COX enzymes are targets for cancer prevention as shown by the observation that nonselective COX and selective COX-2 inhibitors have been reported to effectively prevent experimental colon cancer and can regress colorectal polyps in patients with familial adenomatous polyposis. This review will focus on the role of COX-2 as a target for the prevention and treatment of human colorectal cancer.