Overexpression of Stably Transfected Human Glutathione S-Transferase P1–1 Protects against DNA Damage by Benzo[a]pyrene Diol-Epoxide in Human T47D Cells

Publisher Website
Google Scholar
Abstract
The (+)-anti enantiomer of benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE) is a potent mutagenic and carcinogenic metabolite of benzo[a]pyrene (BP), and a major fraction is conjugated with glutathione in vivo. The chemopreventive role of glutathione S-transferases (GSTs) in protecting against covalent modification of DNA and other cellular macromolecules by BPDE was modeled in human T47D and MCF-7 cell lines previously stably transfected with human GSTπ1 (hGSTP1). Cells were exposed to [3H]BPDE (30–600 nm). Dose-response experiments indicated that the high level of expression of hGSTP1–1 in the T47Dπ cell line (4411 ± 183 milliunits/mg of cytosolic protein, using 1-Cl-2,4-dinitrobenzene as substrate), resulted in 70–90% reduction in the covalent 3H-adduct formation in DNA or RNA isolated from the GSTP1-transfected T47Dπ cell line. The lower level of hGSTP1–1 expression in the transfected MCF-7 cell line (91 milliunits/mg) provided only marginal protection against [3H]BPDE adduct formation and did not affect sensitivity to BPDE-induced cytotoxicity. Protection against BPDE-induced cytotoxicity was observed only in the T47Dπ cell line, which had an IC50 value 5.8-fold greater than that of the T47Dneo control cell line. Measurement of glutathione conjugates of BPDE indicated that the total conjugation was 5-fold higher in the GSTπ-transfected T47D line, most of which was exported into the culture medium over the 20-min exposure period. These results indicate that hGSTP1–1 protects effectively against DNA and RNA modification by BPDE, but moderate to high level expression may be required for strong protection against BPDE-induced genotoxicity and cytotoxicity.

This publication has 31 references indexed in Scilit: