There are about 50 million cigarette smokers in the U.S. and at least another 10 million users of smokeless tobacco. There are 12 million problem drinkers and additional 40 million heavy drinkers. Problem and heavy drinkers are generally heavy smokers. Cancer risk is exacerbated by a combination of drinking and tobacco use. Since ethanol by itself is not a carcinogen, the increase in cancer incidence must be due to ethanol enhancing the effect of carcinogens in tobacco. Based on findings of our recent studies, this research proposal will develop an animal model to study the interaction of the two factors. Since our studies show that ethanol enhances chemically-induced esophageal tumors only when it is used as a tumor promoter, ethanol in these experiments will be administered only after initiator exposure has been completed. Two potent tobacco specific nitrosamines, N-nitrosonornicotine and 2-(methylnitrosamino)-1-(3-pyridyl)- 1-butanone will be used to initiate carcinogenesis. The study will focus on the oral cavity and esophagus since the combined effects of tobacco and alcohol are most apparent at these sites. The animal model will be developed in two phases. First a pilot study will be done to determine the optimal dose(s) and duration of carcinogen to be used in the second phase which will study the contribution of ethanol as a promoter. Studies on exfoliated human oral mucosal cells will also be performed to test whether the extent of DNA damages and repair inhibition can be used as a marker for increased carcinogenesis risk associated with tobacco and ethanol. Biochemical studies included will investigate the molecular mechanisms involved such as DNA strand breaks, persistence of the putative promutagenic lesion 06methylguanine and levels of methyltransferase repair enzyme. Comparisons will be made between tobacco users, drinkers and smokers and their controls. The extent of DNA damage could be potential intermediate marker for chemoprevention studies to screen for agents that may reverse such injury. The results of the above studies will be useful in designing strategies aimed at reducing cancer risk due to tobacco and alcohol use.
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