The UV mouse skin model and B[a]P mouse skin-paint model of carcinogenesis are both mediated by the production of reactive oxygen species associated with subcutaneous acute and chronic inflammation.. With this documented information, phenyl propanoids and certain flavonoids, including the catechins (such as EGCG) are being tested as antiinflammatory and antioxidant chemopreventives. Since inflammation is known to be carcinogenesis-enhancing, and since subepithelial inflammation is present particularly in those organ epithelia that directly contact the environment, viz, skin, lung, colon, and bladder, the testing of polyphenolic antiinflammatory/ antioxidant agents for their chemopreventive efficacy is being done. Published studies exist describing the chemoprevention of carcinogen- induced tumors in mice and rats by the phenylpropanoids and many of the flavonoids, including the hydrolyzable and condensed tannins, e.g., ellagic acid and epigallocatechin gallate. Testing a candidate chemopreventive agent for its ability to produce regression of established preinvasive (intraepithelial) neoplasia is closely analogous to chemoprevention testing in humans, where cohorts possess intraepithelial neoplasia of a given organ epithelium and candidate chemopreventive agents are being tested for their ability to produce regression of the intraepithelial neoplastic lesion(s).
