gms | German Medical Science

Objective: Glutathione S-transferases (GSTs) play an important role in multidrug resistance. The diazeniumdiolate JS-K generates nitric oxide (NO) after enzymatic activation by GST-alpha and has a dose-dependent antiproliferative effect in U87 glioma cells, and induces sensitization to imatinib (Glivec^®) in vitro. The objective of this study was to investigate this effect in primary glioblastoma (GBM) cultures from resection material and to correlate it to the expression of GST and PDGFR isoenzymes in these cells.

Methods: U87 cells and primary glioblastoma cells from 4 patients (LT, TG, PJ, PM) were incubated with JS-K (1-30µM) or with imatinib (0.1-50µM) for 24h. Cell viability was assessed by MTT assay after 24, 48, and 72 hours. Expression of GST-alpha, GST-pi, PDGFR-alpha and PDGFR-beta was assessed by immunocytochemistry. The data was analyzed statistically using ANOVA.

Results: JS-K had a dose-dependent cytotoxic effect in all cells with an IC50 between 8 and 15µM. Only high doses of imatinib (>30µM) caused cell death in U87 and TG GBM cells, but most cells were completely resistant to imatinib. While imatinib and JS-K showed a significant increase in cytotoxicity compared to JS-K alone (p<0.0001) in U87 cells, this chemosensitizing effect could not be reproduced in the other GBM cell lines. All glioma cell lines showed a strong GST-alpha and GST-pi expression. PDFGR-alpha and -beta were only weakly positive in U87 cells and in 1/4 of the primary glioblastomas, which might account for the lacking response to imatinib.

Conclusions: The NO-donor JS-K induces a reproducible antiproliferative effect in U87 gliomas and primary GBM cultures from resection material. The response to JS-K correlates with the degree of GST-expression which makes it a good candidate for use in gliomas which overexpress GST.