COX-2 inhibition as a tool to treat and prevent colorectal cancer

The cyclooxygenase-2 (COX-2) enzyme has a fundamental role in the carcinogenesis of colorectal cancer. The anticarcinogenic mechanisms of NSAIDs are not completely understood and appear to be only partially dependent on inhibition tumoral COX-2. Moreover, the mechanisms of NSAIDs depend on the concentration. In experimental setting, at low levels NSAIDs downregulate the COX-2 gene in colorectal cancer cells, whereas at clinical relevant concentrations the production of prostaglandin E2 by enzymatic activity of COX-2 is diminished resulting in inhibition of the tumor angiogenesis. At higher levels NSAIDs and especially some selective COX-2 inhibitors are capable of COX-2 independent effects, such as apoptosis induction of tumor cells. In animal models, NSAIDs administration results in inhibition of angiogenesis and proliferation, induction apoptosis and prevention of metastasis. In clinical setting, NSAIDs and selective COX-2 inhibitors have the capacity to prevent the development of colorectal adenomas. We have summarized data regarding the role of COX-2 in CRC and discuss the multiple targets of NSAIDs in their anticarcinogenic action. However, the translation of these anticarcinogenic effects of NSAIDs to its clinical application as adjuvant therapy in CRC is hampered by a lack of randomized clinical trials with long-term follow-up.