Sensitization of human melanoma cells to the cytotoxic effect of melphalan by the glutathione transferase inhibitor ethacrynic acid

Glutathione transferases are enzymes implied in the resistance of tumor cells to bifunctional alkylating cytostatic drugs. We have investigated the effect of the glutathione transferase inhibitor by ethacrynic acid on the cytotoxicity of melphalan to a human melanoma cell line (RPMI 8322) with a hig...

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Bibliographic Details
Published in:Cancer research (Chicago, Ill.) Ill.), 1991, Vol.51 (1), p.94-98
Main Authors: HANSSON, J, BERHANE, K, CASTRO, V. M, JUNGNELIUS, U, MANNERVIK, B, RINGBORG, U
Format: Article
Language:English
Subjects:
Antineoplastic agents
Biological and medical sciences
Cell Survival - drug effects
Cross-Linking Reagents
Dose-Response Relationship, Drug
Drug Synergism
ethacrynic acid
Ethacrynic Acid - pharmacology
General aspects
glutathione transferase
Glutathione Transferase - antagonists & inhibitors
Humans
In Vitro Techniques
Isoenzymes - antagonists & inhibitors
Medical sciences
Melanoma - drug therapy
Melanoma - pathology
Melphalan - pharmacology
Pharmacology. Drug treatments
Tumor Cells, Cultured
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Summary:Glutathione transferases are enzymes implied in the resistance of tumor cells to bifunctional alkylating cytostatic drugs. We have investigated the effect of the glutathione transferase inhibitor by ethacrynic acid on the cytotoxicity of melphalan to a human melanoma cell line (RPMI 8322) with a high level of glutathione transferase activity. Using 1-chloro-2,4-dinitrobenzene as substrate, ethacrynic acid was shown to inhibit the activity of purified human glutathione transferases, with 50% inhibition values of 1, 10, and 15 microM for transferase mu (class mu), transferase epsilon (class alpha) and transferase pi (class pi), respectively, all of which occur in RPMI 8322 cells. Ethacrynic acid at a concentration of 20 microM, which by itself was noncytotoxic, increased the cytotoxicity of melphalan to RPMI 8322 human melanoma cells approximately 2-fold. The induction of DNA interstrand cross-links by 40 microM melphalan was increased 1.4-fold by 30 microM ethacrynic acid. These results indicate that a potentiation of the cytotoxic effect of bifunctional alkylating agents can be achieved by inhibition of glutathione transferase and that the enhanced cytotoxicity may be caused at least in part by increased formation of drug-DNA adducts.
ISSN:0008-5472
1538-7445