Tumor resistance to the 2-chloroethylnitrosoureas still constitutes a formidable problem limiting the successful therapy of human malignant brain tumors with these agents. Our efforts over the past few years with human malignant glioma cell lines variably resistant to CENUs, have demonstrated that brain tumor CENU-resistance is associated with elevation of cellular glutathione (GSH) and over-expression of glutathione-S-transferases (GSTs). However, little is known about the exact nature of the GSTs present in CENU-resistant brain tumors, or about the level of transcription and/or amplification of GST genes in these cells. The goal of this proposal is to undertake the purification and characterization of GSTs from CENU-resistant human malignant astrocytoma cell lines and from primary biopsies of both adult and pediatric brain tumor patients. We will characterize these GSTs biochemically and functionally and determine their potential role in brain tumor CENU-resistance by establishing their ability to catalyze both the direct inactivation of CENUs and the quenching of CENU-induced DNA crosslink precursors by GSH, two processes that can result in cellular CENU-resistance. Using antibodies raised against the purified GSTs and against other known GSTs, as well as, cDNAs specific for the basic, near- neutral and acidic GSTs, we will determine the type and molecular expression of specific glutathione-S-transferases in brain tumors. We will also determine the level of transcription and/or amplification of specific GST subunit genes. The in vitro CENU-resistance of the cell lines and the response to therapy of patients treated with a CENU regimen will be correlated with the type and molecular expression of the specific GSTs in the rumors. The blood-brain-barrier poses a significant limitation to the delivery of water soluble agents to the brain and to brain tumors. Consequently, we propose to synthesize lipophilic analogues of a known GST inhibitor, ethacrynic acid, determine their ability to inhibit GSTs in CENU-resistant brain tumors, and determine the extent to which pretreatment of tumor cells with these lipophilic, brain-permeable GST inhibitors will reverse the CENU-resistance of the tumors. The results of this tightly- focused research will provide very important information on the specific types and role of GSTs mediating CENU-resistance of human malignant brain tumors and provide the basis for future attempts to circumvent this resistance clinically.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA055835-03
Application #
2096941
Study Section
Experimental Therapeutics Subcommittee 1 (ET)
Project Start
1992-05-01
Project End
1996-04-30
Budget Start
1994-05-01
Budget End
1996-04-30
Support Year
3
Fiscal Year
1994
Total Cost
Indirect Cost
Name
University of Texas MD Anderson Cancer Center
Department
Pediatrics
Type
Other Domestic Higher Education
DUNS #
001910777
City
Houston
State
TX
Country
United States
Zip Code
77030
Antoun, G; Baylin, S B; Ali-Osman, F (2000) DNA methyltransferase levels and altered CpG methylation in the total genome and in the GSTP1 gene in human glioma cells transfected with sense and antisense DNA methyltransferase cDNA. J Cell Biochem 77:372-81
Keller, C; Ali-Osman, F (1998) Translational inhibition of messenger RNA of the human pi class glutathione S-transferase by antisense oligodeoxyribonucleotides. Chem Biol Interact 111-112:307-23
Lo, H W; Ali-Osman, F (1998) Structure of the human allelic glutathione S-transferase-pi gene variant, hGSTP1 C, cloned from a glioblastoma multiforme cell line. Chem Biol Interact 111-112:91-102
Lo, H W; Ali-Osman, F (1997) Genomic cloning of hGSTP1*C, an allelic human Pi class glutathione S-transferase gene variant and functional characterization of its retinoic acid response elements. J Biol Chem 272:32743-9
Brandt, T Y; Ali-Osman, F (1997) Detection of DNA damage in transcriptionally active genes by RT-PCR and assessment of repair of cisplatin-induced damage in the glutathione S-transferase-pi gene in human glioblastoma cells. Toxicol Appl Pharmacol 143:22-9
Ali-Osman, F; Brunner, J M; Kutluk, T M et al. (1997) Prognostic significance of glutathione S-transferase pi expression and subcellular localization in human gliomas. Clin Cancer Res 3:2253-61
Ali-Osman, F; Akande, O; Antoun, G et al. (1997) Molecular cloning, characterization, and expression in Escherichia coli of full-length cDNAs of three human glutathione S-transferase Pi gene variants. Evidence for differential catalytic activity of the encoded proteins. J Biol Chem 272:10004-12
Ali-Osman, F; Antoun, G; Wang, H et al. (1996) Buthionine sulfoximine induction of gamma-L-glutamyl-L-cysteine synthetase gene expression, kinetics of glutathione depletion and resynthesis, and modulation of carmustine-induced DNA-DNA cross-linking and cytotoxicity in human glioma cells. Mol Pharmacol 49:1012-20
Ali-Osman, F; Rairkar, A; Young, P (1995) Formation and repair of 1,3-bis-(2-chloroethyl)-1-nitrosourea and cisplatin induced total genomic DNA interstrand crosslinks in human glioma cells. Cancer Biochem Biophys 14:231-41