Modulation of mitomycin C resistance by glutathione transferase inhibitor ethacrynic acid

Shivendra V. Singh, Bing H. Xu, Ashok K. Maurya, A. Mohsin Mian

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

This study was undertaken to elucidate the mechanism(s) of cross-resistance (4.9-fold) to mitomycin C(MMC) in a multi-drug-resistant cell line, P388/R-84. Intracellular accumulation of MMC by sensitive (P388/S) and P388/R-84 cells was comparable. Despite a 32% reduction in NADPH cytochrome P-450 reductase activity (responsible for MMC activation) in P388/R-84 cells, the rate of MMC bio-reduction by sensitive and resistant cells was similar. These results suggested that MMC resistance in P388/R-84 cell line must depend on factors other than impaired drug accumulation or bio-activation. Recent studies suggest that glutathione transferase (GST) dependent drug detoxification also contributes to cellular resistance of a variety of alkylating agents. Even though overexpression of GST have been noted in some MMC resistant tumor cells, it is not known if its level affects sensitivity to MMC. We have, therefore, determined the effect of ethacrynic acid (an inhibitor of GST activity) treatment on MMC cytotoxicity in P388/R-84 cells, which have about 2-fold higher GST activity than P388/S cells. The IC50 value for the inhibition of GST activity in vitro by ethacrynic acid (EA) was 16.5 μM (5 μg/ml). A depletion in intracellular GSH was also observed by treating P388/R-84 cells with EA alone or in combination with MMC. A non-toxic concentration of EA (1 μg/ml); 3.3 μM) increased MMC cytotoxicity by 36% in P388/R-84 cells. MMC cytotoxicity was increased 2-fold by EA treatment in glutathione (GSH)-depleted P388/R-84 cells. These results suggest that GST mediated drug inactivation may represent another important mechanism of MMC resistance.

Original languageEnglish
Pages (from-to)257-263
Number of pages7
JournalBBA - Molecular Cell Research
Volume1137
Issue number3
DOIs
StatePublished - Nov 17 1992
Externally publishedYes

Fingerprint

Ethacrynic Acid
Mitomycin
Glutathione Transferase
Pharmaceutical Preparations
Cell Line
NADPH-Ferrihemoprotein Reductase
Alkylating Agents
Inhibitory Concentration 50
Glutathione

Keywords

  • Detoxification
  • Glutathione
  • Glutathione transferase
  • Mitomycin C
  • Resistance

ASJC Scopus subject areas

  • Biophysics
  • Cell Biology
  • Molecular Biology

Cite this

Modulation of mitomycin C resistance by glutathione transferase inhibitor ethacrynic acid. / Singh, Shivendra V.; Xu, Bing H.; Maurya, Ashok K.; Mohsin Mian, A.

In: BBA - Molecular Cell Research, Vol. 1137, No. 3, 17.11.1992, p. 257-263.

Research output: Contribution to journalArticle

Singh, Shivendra V. ; Xu, Bing H. ; Maurya, Ashok K. ; Mohsin Mian, A. / Modulation of mitomycin C resistance by glutathione transferase inhibitor ethacrynic acid. In: BBA - Molecular Cell Research. 1992 ; Vol. 1137, No. 3. pp. 257-263.
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abstract = "This study was undertaken to elucidate the mechanism(s) of cross-resistance (4.9-fold) to mitomycin C(MMC) in a multi-drug-resistant cell line, P388/R-84. Intracellular accumulation of MMC by sensitive (P388/S) and P388/R-84 cells was comparable. Despite a 32{\%} reduction in NADPH cytochrome P-450 reductase activity (responsible for MMC activation) in P388/R-84 cells, the rate of MMC bio-reduction by sensitive and resistant cells was similar. These results suggested that MMC resistance in P388/R-84 cell line must depend on factors other than impaired drug accumulation or bio-activation. Recent studies suggest that glutathione transferase (GST) dependent drug detoxification also contributes to cellular resistance of a variety of alkylating agents. Even though overexpression of GST have been noted in some MMC resistant tumor cells, it is not known if its level affects sensitivity to MMC. We have, therefore, determined the effect of ethacrynic acid (an inhibitor of GST activity) treatment on MMC cytotoxicity in P388/R-84 cells, which have about 2-fold higher GST activity than P388/S cells. The IC50 value for the inhibition of GST activity in vitro by ethacrynic acid (EA) was 16.5 μM (5 μg/ml). A depletion in intracellular GSH was also observed by treating P388/R-84 cells with EA alone or in combination with MMC. A non-toxic concentration of EA (1 μg/ml); 3.3 μM) increased MMC cytotoxicity by 36{\%} in P388/R-84 cells. MMC cytotoxicity was increased 2-fold by EA treatment in glutathione (GSH)-depleted P388/R-84 cells. These results suggest that GST mediated drug inactivation may represent another important mechanism of MMC resistance.",
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