A pilot project in molecular cancer epidemiology: determination of benzo[a]pyrene -- DNA adducts in animal and human tissues by immunoassays

A highly-sensitive immunoassay utilizing antiserum specificfor benzo[a]pyrene covalently bound to DNA has been employedto probe for adducts in the DNA of animal and human tissuesand peripheral blood mononuclear cells. By enzyme-linked immunosorbentassay (ELISA) a dose-related increase in levels of benzo[a]pyrene—DNAadducts was observed in DNA from lung tissue of mice and rabbitsinjected i.p. with benzo[a]pyrene. Quantitation with ELISA wasconfirmed by i.p. injection of [³H]benzo[a]pyrene and determinationof adduct levels in lung DNA by radioactivity. Thus, the ELISAassay was determined to be quantitative for benzo[a]pyrene—DNAadducts in vivo, and the lower limit of detectability establishedat 0.08–0.10 fmol/µg DNA. At this level of sensitivityno significant differences were observed between DNA from peripheralblood mononuclear cells of dogs on smoke inhalation machinesand controls. In an attempt to probe for benzo[a]pyrene—DNAadducts in human subjects resulting from chronic environmentalexposure, lung tissue, lung tumor and blood samples were obtainedfrom patients hospitalized for lung cancer and other diseases.A detailed history of exposure to environmental sources of benzo[a]pyreneand to factors known to influence polycyclic aromatic hydrocarbonmetabolism was attempted for 15 patients. DNA was extractedfrom the lung tissue of 27 patients and blood cells of severalindividuals and assayed by ELISA; 5 patients appeared to havelow but measurable levels of benzo[a]pyrene—DNA adductsas determined by ELISA. All of these patients were in the lungcancer group. However, the number of subjects was too smallto draw conclusions relating exposure history to the occurrenceof hydrocarbon—DNA adducts. These preliminary resultsshould encourage further studies on the utilization of immunoassaysfor carcinogen—DNA adducts as a potential tool in epidemiologicalstudies attempting to relate biologically-effective dose ofcarcinogen to human cancer risk.