Detection of DNA Adducts in Human Oral Tissue: Correlation of Adduct Levels with Tobacco Smoking and Differential Enhancement of Adducts Using the Butanol Extraction and Nuclease PI Versions of 32PPostlabeling1

Samples of clinically normal oral tissue were obtained from patients undergoing surgery for intraoral squamous cell carcinoma. DNA was extracted from samples obtained from 20 tobacco smokers, four exsmokers, and nine nonsmokers and analyzed for the presence of aromatic DNA adducts using two distinct modifications of the '-I* postlabeling assay. ' V postlabeling following butano! extraction enhancement revealed a much wider range and substantially higher levels of DNA adducts than obtained following nuclease PI enrichment. Adduct levels in smokers, exsmokers, and nonsmokers were 1133 ±354, 785 ±251, and 660 ±317 amol/ug of DNA i SI)i, respectively. The elevation of adduci levels in smokers com pared with either nonsmokers or nonand exsmokers combined is statis tically significant (P < 0.005). These observations are consistent with epidemiolÃ3gica! evidence linking tobacco smoking with oral cancer. The differential enhancement of DNA adducts with the two '-!' postlabeling protocols indicate that aromatic amines and nitroaromatics may be im portant sources of the DNA adducts detected in human oral tissue.