Use of human peripheral blood lymphocytes to measure DNA binding capacity of chemical carcinogens

Abstract

Although animal models have been used successfully to study metabolic activation and binding of carcinogens to DNA, only limited studies have been done in human systems. To circumvent the problems associated with the inaccessibility of human tissues and a lack of sensitive methods to detect DNA damage, we have investigated the capability of human peripheral blood lymphocytes in vitro to metabolize carcinogens to their DNA binding species by a 32P-labeled adduct assay. Freshly isolated lymphocytes were exposed at 37 degrees C for 18 hr to 4-aminobiphenyl, 2-aminofluorene, 2-anthramine, 2-acetylaminophenanthrene, benzidine, 1-nitropyrene, 1,2-benzanthracene, triphenylene, 7,12-dimethylbenz[a]anthracene, or benzo[a]pyrene at 30 microM each, compounds that are shown or suspected to be carcinogenic in experimental animals. Anthracene, pyrene, and perylene were included as noncarcinogenic controls. Our data indicate that all test carcinogens formed readily measurable levels of DNA adducts. Analysis of exposed DNAs by 32P-labeling after digestion and adduct enrichment showed exclusively or predominantly one major adduct for all test carcinogens, except for 2-anthramine, triphenylene, and 7,12-dimethylbenz[a]anthracene, which showed two or three adducts, in the range of 8-1500 amol/micrograms of DNA. No DNA binding was detected for the noncarcinogens. From 12 lymphocyte specimens studied thus far, significant interindividual variations were observed for 2-aminofluorene (62-fold), 7,12-dimethylbenz[a]anthracene (10-fold), benzidine (19-fold) and benzo[a]pyrene (18-fold) in their capacity to bind to the lymphocyte DNA. The lymphocyte system in combination with the 32P-adduct assay may prove to be an ultrasensitive means to determine interindividual variations in the ability to biotransform carcinogens.