Exposure to a wide variety of carcinogens leads to the formation of DNA adducts. Measurement of DNA adduct content in cells provides direct evidence for exposure and damage. Analysis of these so-called molecular markers are becoming an accepted tool for assessing human health risk. Our long term objective is the correlation between the presence of DNA adducts and carcinogenesis in target tissues. We are investigating DNA adducts of aromatic amines, a class of compounds found in cigarette smoke and protein-containing foods. Epidemiological studies have established the carcinogenicity of certain aromatic amines such as 4- aminobiphenyl (ABP), 2-naphthylamine and 2-amino-3-methylimidazo[4,5- f]quinoline (IQ) in both humans and animals. These compounds can be converted to electrophilic intermediates containing nitrene and nitrenium ion functional groups. These species are known to attack predominantly the C8 position of guanine residues. Pancreatic, lung or colon cancerous tissues contain DNA adducts of one or more of these compounds as well as the enzymes capable of activating them. Improved methods for detection and characterization of DNA adducts are important toward our goal of establishing their direct relationship to cancer. Capillary separation methods (HPLC and capillary electrophoresis) coupled to electrospray ionization/tandem mass spectrometry will be used to analyze human lung and pancreatic tissues from smokers in order to assess the role of ABP in human carcinogenesis. Tissues from animal models exposed to aromatic amines will be used as surrogates in developing the methodology. Comparisons will be made to 32P- post- labeling, currently the most widely used method of adduct analyses. However, this methodology does not provide direct structural information or sequence preferences of the adduct. To address these important issues, CE-MS will be used to characterize oligonucleotide adducts in order to determine sequence recognition patterns of carcinogens. It is expected that this program will lead to the establishment of a rigorous mass spectrometric methodology for the study of DNA adducts and the use of biomarkers for risk assessment.
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