[An overview on chemoprevention of colorectal cancer]

Chemoprevention of colorectal cancer has been extensively investigated in animal models and in high-risk human populations with inherited or acquired genetic changes, using anticarcinogenic agents from natural and synthetic sources. To understand active agents using a short-term assay, reliable intermediate biomarkers other than cancer are required as end-points. Endoscopically detectable aberrant crypt foci and adenomas are useful biomarkers in human intervention trials. Indomethacin and other nonsteroidal antiinflammatory drugs (NSAIDs) inhibit carcinogen-induced colon cancer development in rats. It was reported that a number of colorectal polyps in familial adenomatous polyposis patients regress after several months of sulindac treatment. Epidemiological studies have shown that regular use of aspirin and other NSAIDs reduces the risk of colorectal cancers and adenomas. In addition, ursodeoxycholic acid and alpha-difluoromethylornithine, a selective inhibitor of ornithine decarboxylase, have been employed in human intervention trials. Vegetable antioxidants such as carotenoids and flavonoids, omega-3 fatty acids, lactic acid bacteria, and indigestible oligosaccharides may also be promising chemopreventive agents.