Influence of cigarette smoking on the levels of DNA adducts in human bronchial epithelium and white blood cells

Abstract

The presence of carcinogen‐DNA adducts in human tissues is evidence of exposure to carcinogens and may be an indicator of cancer risk. DNA was isolated from non‐tumorous bronchial tissue of 37 cigarette smokers, 8 former smokers and 8 non‐smokers and analyzed for the presence of aromatic and/or hydrophobic DNA adducts in the ³²P‐post‐labelling assay. Adducts were detected as bands of radioactive material when 5′‐³²P‐labelled deoxyribonucleoside 3′, 5′‐bisphosphates were chromatographed on polyethyleneimine‐cellulose tic plates, and the patterns indicated the formation of adducts by a large number of compounds. Adduct levels detected in DNA from non‐smokers, former smokers and current smokers were 3.45 ± 1.62, 3.93 ± 1.92 and 5.53 ± 2.13 adducts/10⁸ nucleotides, respectively. The differences in adduct levels be tween smokers and former and non‐smokers were statistically significant (p < 0.01); and among the smokers, significant correlations were found between adduct levels and both daily cigarette consumption and total cigarette consumption (daily consumption × number of years smoked). DNA was also isolated from the peripheral‐blood leukocytes of 31 heavy smokers (>20 cigarettes/day) and 20 non‐smokers and analyzed by ³²P‐post‐labelling. Adduct levels in the smokers' samples were not significantly different from levels in the nonsmokers' samples (2.53 ± 1.31 and 2.12 ± 1.44 adducts/10⁸ nucleotides, respectively). Thus, evidence for carcinogen exposure was found in human bronchial epithelium, a target tissue for tobacco‐induced tumour formation, but not in peripheral‐blood cells, indicating possible limitations in the use of the latter as a surrogate, non‐target tissue source of DNA for monitoring human exposure to inhaled carcinogens.