Abstract
γ-l-glutamyl-l-cysteinylglycine (GSH) has been shown to inactivate 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and quench DNA cross-link precursors of BCNU. Because of the central role of 2-chloroethylnitrosoureas in brain tumor chemotherapy, we investigated the intracellular GSH content and the expression of specific glutathione-S-transferases (GSTs) in three human malignant astrocytoma cell lines (UWR1, UWR2, and UWR3) of varying BCNU resistance to determine the interrelationship of these parameters with brain tumor BCNU resistance. GSH was assayed by ion-exchange high performance liquid chromatography after derivatization with 1-fluoro-2,4 dinitrobenzene. Both bulk and specific GST (acid, near-neutral, and basic) activities were examined using substrates that show high specificities to the different GSTs. Western blot analyses with antisera against GST-α, -µ, and -π subunits were also performed on partially purified GST from the cells of each cell line. The results showed GSH content of 91, 46.5, and 28.3 nmol GSH/mg protein for UWR1, UWR2, and UWR3, respectively. Bulk GST activity (with 1-chloro-2,4-dinitrobenzene as substrate) also correlated with increasing BCNU resistance. Of the three GST classes examined by both substrate specificities and Western blotting, only the expression of the acidic form, GST-π, correlated significantly with the rank order of BCNU resistance of the cell lines. GST-µ and -α were present in only trace amounts in all three cell lines.
Footnotes
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↵1 Supported by National Institutes of Health, National Cancer Institute, Grant CA46410.
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↵2 To whom requests for reprints should be addressed, at Department of Experimental Pediatrics, Section of Experimental Therapeutics, University of Texas, Box 87, M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, Texas 77030.
- Received March 13, 1990.
- Accepted July 23, 1990.
- ©1990 American Association for Cancer Research.
Volume 50, Issue 21
