Targeting cyclooxygenase‐2 for prevention and therapy of colorectal cancer

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Abstract
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.