[COX-2 inhibitor and colon cancer]

It is suggested that nonsteroidal antiinflammatory inhibitors alter the biology of colorectal carcinogenesis. Cyclooxygenase-2, one of target molecules of these drugs, is reported to be upregulated in cancer tissues. Cultured cells which were derived from intestinal epithelium and programmed to express COX-2 showed several phenotypic changes in favor of carcinogenesis, including resistance to apoptosis and enhancement of cell proliferation, angiogenesis, and invasion. Tumor growth implanted in COX-2 null mice was significantly attenuated, but not in COX-1 null or wild type mice, suggesting that COX-2 in stroma also has an important role in tumor growth. Moreover, PGE2, one of COX-2 metabolites, reversed these antitumor effects, indicating that inhibition of PGE2 production has a pivotal role in tumor suppression. However, NSAIDs show antitumor effects in cancer cells lacking COX-1 or COX-2 expression, and some derivatives lacking the ability to suppress COX activity show antitumor effects. These results suggest that COX independent pathway might be involved in antitumor effects of NSAIDs. For the development of novel and effective therapies, it is required to elucidate mechanisms underlying antitumor effects of NSAIDs.