Epidemiological evidence suggests that aflatoxin B1 (AFB1), a potent animal hepatotoxin and hepatocarcinogen may be an etiologic agent in the induction of primary liver cancer in humans. It undergoes activation via epoxidation and the interaction of its epoxide with DNA is believed to be responsible for its initiation of carcinogenesis. There is a wide different in carcinogenicity of AFB1 between rats and hamsters and AFB1-DNA binding in vivo and in vitro. Recent work with hepatosubcellular fractions and isolated hepatocytes of these two species from my laboratory has shown that the binding of DNA with AFB1 is strongly modulated by a competitive detoxication reaction with reduced glutathione (GSH), catalyzed by one or more of the cytosolic GSH S-transferases. The purpose of this study is to explore and delineate further a possible role of GSH and its S-transferases in AFB1 carcinogenesis.
The specific aims of this project are to extend and amplify our current studies by (1) investigating whether one or more of the known specific cytosolic GSH S-transferases are responsible for conversion of AFB1-epoxide to the AFB1-GSH conjugate. These studies would entail purification of various GSH S-transferases from rat and hamster livers, and examining their catalytic and kinetic properties in a reconstituted system using either microsome-mediated AFB1-epoxide or synthetic AFB1-epoxide as a substrate (2) investigate the kinetics of hepatic AFB1-DNA binding in rats and hamsters over a wide range of AFB1 dose and by modulation of GSH and its transferases. Pretreatment of animals with buthionine sulfoximine (BSO) will lower hepatic GSH levels and administration of phenobarbital (PB) will increase GSH S-transferases activities and (3) investigate the biological significance of GSH and its S-transferases in modulation of hepatic AFB1-DNA binding and hepatocarcinogenesis by examining production of a population of single GSH S-transferase placental form positive hepatocytes and of preneoplastic enzyme altered foci of hepatocytes as well as ultimate hepatocarcinomas in rats and hamsters in which GSH is reduced by pretreatment with BSO before the administration of AFB1. In similar experiments the effect of increased GSH S-transferases will be examined by administration of PB with and without BSO treatment. The long term objectives of this program are aimed at understanding the molecular mechanisms in AFB1 carcinogenesis.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA031641-08
Application #
3169744
Study Section
Metabolic Pathology Study Section (MEP)
Project Start
1982-01-01
Project End
1995-11-30
Budget Start
1992-01-01
Budget End
1992-12-31
Support Year
8
Fiscal Year
1992
Total Cost
Indirect Cost
Name
Temple University
Department
Type
Schools of Medicine
DUNS #
City
Philadelphia
State
PA
Country
United States
Zip Code
19122
Kimura, Masatomo; Lehmann, Kiyoko; Gopalan-Kriczky, Prathima et al. (2004) Effect of diet on aflatoxin B1-DNA binding and aflatoxin B1-induced glutathione S-transferase placental form positive hepatic foci in the rat. Exp Mol Med 36:351-7
Hiruma, S; Gopalan-Kriczky, P; Qin, G et al. (2001) Differential effects of acetaminophen pretreatment on hepatic aflatoxin B(1)-DNA binding, cellular proliferation, and aflatoxin B1-induced hepatic foci in rats and hamsters. Cancer Lett 170:117-24
Qin, G; Ning, Y; Su, J et al. (1998) Enhancement of aflatoxin B1-induced enzyme altered hepatic foci in rats by treatment with carbon tetrachloride. Exp Mol Med 30:186-91
Hiruma, S; Kimura, M; Lehmann, K et al. (1997) Potentiation of aflatoxin B1-induced hepatocarcinogenesis in the rat by pretreatment with buthionine sulfoximine. Cancer Lett 113:103-9
Hiruma, S; Qin, G Z; Gopalan-Kriczky, P et al. (1996) Effect of cell proliferation on initiation of aflatoxin B1-induced enzyme altered hepatic foci in rats and hamsters. Carcinogenesis 17:2495-9
Gopalan-Kriczky, P; Hiruma, S; Lotlikar, P D (1994) Effect of glutathione levels on aflatoxin B1-DNA binding in livers and kidneys of male rats and hamsters pretreated with buthionine sulfoximine and dimethylmaleate. Cancer Lett 76:25-30
Gopalan-Kriczky, P; Jensen, D E; Lotlikar, D (1994) Conjugation of microsome generated and synthetic aflatoxin B1-8,9 epoxide and styrene oxide to glutathione by purified glutathione S-transferases from hamster and mouse livers. Cancer Lett 86:83-90
Gopalan, P; Tsuji, K; Lehmann, K et al. (1993) Modulation of aflatoxin B1-induced glutathione S-transferase placental form positive hepatic foci by pretreatment of rats with phenobarbital and buthionine sulfoximine. Carcinogenesis 14:1469-70
Tsuji, K; Gopalan, P; Lehmann, K et al. (1992) Species and sex differences of aflatoxin B1-induced glutathione S-transferase placental form in single hepatocytes. Cancer Lett 66:249-54
Gopalan, P; Jensen, D E; Lotlikar, P D (1992) Glutathione conjugation of microsome-mediated and synthetic aflatoxin B1-8,9-oxide by purified glutathione S-transferases from rats. Cancer Lett 64:225-33

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