The metabolism of benzo(a)pyrene (B(a)P) and other polynuclear aromatic hydrocarbon carcinogens to highly reactive diol epoxide derivatives is thought to be an important step in the process of carcinogenesis. Diol epoxides bind covalently to DNA both in vitro and in vivo, forming adducts which differ in chemical structure and in their conformation in native DNA. As a result of these differences in structure, different adducts have varying biological effects. The relationship between DNA adduct conformation and biological effects will be studied in a strain of Chinese hamster ovary cells (CHO) in which mutation at two genetic loci and expression of a transfected viral gene (thymidine kinase) can be measured. Using a series of diol epoxides derived from B(a)P, which span the range of known DNA adduct conformations, the rates of formation and removal of DNA adducts in CHO cells will be determined and related to four biological endpoints: cytotoxicity, mutation at the hprt locus, mutation at the oua locus, and expression of an exogenous gene modified in vitro with the diol epoxides and transfected into the cells. These experiments will be carried out in DNA repair-proficient CHO cells and in several recently derived, mutant cell lines which are deficient in repair of DNA damage. This will allow the determination of biological potencies on a per adduct formed basis and the comparison of rates of repair of different DNA-adducts and the effectiveness of the repair system in ameliorating biological damage. The combined use of cells which differ only in their ability to repair DNA-damage and of the DNA-mediated gene transfer assay system will allow the separation of effects due to DNA damage from those due to covalent binding to other classes of macromolecules.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES003602-02
Application #
3251045
Study Section
Chemical Pathology Study Section (CPA)
Project Start
1984-08-01
Project End
1987-07-31
Budget Start
1985-08-01
Budget End
1986-07-31
Support Year
2
Fiscal Year
1985
Total Cost
Indirect Cost
Name
University of Texas MD Anderson Cancer Center
Department
Type
Organized Research Units
DUNS #
001910777
City
Houston
State
TX
Country
United States
Zip Code
77030
MacLeod, M C; Evans, F E; Lay, J et al. (1994) Identification of a novel, N7-deoxyguanosine adduct as the major DNA adduct formed by a non-bay-region diol epoxide of benzo[a]pyrene with low mutagenic potential. Biochemistry 33:2977-87
MacLeod, M C (1993) Identification of a DNA structural motif that includes the binding sites for Sp1, p53 and GA-binding protein. Nucleic Acids Res 21:1439-47
Zhao, R; Liu, T M; Kim, S K et al. (1992) Identification and quantitative detection of isomeric benzo[a]pyrene diolepoxide--DNA adducts by low-temperature conventional fluorescence methods. Carcinogenesis 13:1817-24
MacLeod, M C; Daylong, A; Adair, G et al. (1991) Differences in the rate of DNA adduct removal and the efficiency of mutagenesis for two benzo[a]pyrene diol epoxides in CHO cells. Mutat Res 261:267-79
MacLeod, M C; Adair, G; Daylong, A et al. (1991) Low absolute mutagenic efficiency but high cytotoxicity of a non-bay region diol epoxide derived from benzo[a]pyrene. Mutat Res 261:281-93
MacLeod, M C; Stewart, E; Daylong, A et al. (1991) Reaction of a chemotherapeutic agent, 6-mercaptopurine, with a direct-acting, electrophilic carcinogen, benzo[a]pyrene-7,8-diol 9,10-epoxide. Chem Res Toxicol 4:453-62
MacLeod, M C; Humphrey, R M; Bickerstaff, T et al. (1990) Inhibition by 6-mercaptopurine of the binding of a benzo(a)pyrene diol-epoxide to DNA in Chinese hamster ovary cells. Cancer Res 50:4355-9
MacLeod, M C; Adair, G; Humphrey, R M (1988) Differential efficiency of mutagenesis at three genetic loci in CHO cells by a benzo[a]pyrene diol epoxide. Mutat Res 199:243-54
MacLeod, M C; Adair, G; Dickson-Black, D et al. (1987) Stabilization of a reactive, electrophilic carcinogen, benzo[a]pyrene diol epoxide, by mammalian cells. Chem Biol Interact 63:279-89