The long-term aims of this research are to improve knowledge of the mechanisms of action of carcinogenic polycyclic hydrocarbons and to provide better means both for monitoring human exposure to these compounds and for evaluating the risks of that exposure. The proposed research will concentrate on five main aspects of polycyclic hydrocarbon carcinogenesis: (i) examination of the specificity of the interaction of diol-epoxides and triol-epoxides, candidate ultimate carcinogens, with proto-oncogene DNA sequences implicated in the process of malignant transformation; (ii) comparison of the metabolism and DNA adduct forming ability of active and inactive dibenztetracenes, in order to identify differences that might account for their respective activities; (iii) examination of the DNA adducts formed by complex mixtures of polycyclic aromatic hydrocarbons in order to identifY their potential genotoxic activity and to identify which components of the mixtures may be responsible for their biological activity; (iv) development of a simple procedure which, when applied to the analysis of adducts formed by complex mixtures in animal and human tissues, will facilitate a more rapid determination of the overall level of DNA adduct formation; and (v) study of the persistence of hydrocarbon-DNA adducts in rodent skin from different species in order to investigate the basis for differences in tissue and species susceptibility to carcinogenesis by polycyclic hydrocarbons. The methods to be used include in vitro metabolism by rat liver microsomal fractions, treatment of skin in vivo and of keratinocytes in vitro and mutagenicity in V79 cells. Metabolites will be synthesized by chemical-oxidation and characterized by uv and mass spectrometry. DNA adducts will be detected and quantitated using 32p-postlabelling analysis, a procedure already well established in this laboratory. High pressure liquid chromatography will assist in the metabolic studies and will be incorporated into the 32p-postlabelling assay. Proto-oncogene activation will be investigated in the NIH 3T3 cell transfection system and the sites of DNA modification by hydrocarbons and the nature of the mutations will be determined using gene amplification, oligonucleotide hybridization and DNA sequencing techniques. Since some complex mixtures of polycyclic hydrocarbons are known to cause tumours in man, improved knowledge of their biological significance and mode of action will be central to attempts to reduce the incidence of some forms of human cancer.
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