MODULATION OF MITOMYCIN-C RESISTANCE BY GLUTATHIONE TRANSFERASE INHIBITOR ETHACRYNIC-ACID
MODULATION OF MITOMYCIN-C RESISTANCE BY GLUTATHIONE TRANSFERASE INHIBITOR ETHACRYNIC-ACID
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DOI：
10.1016/0167-4889(92)90145-2
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发表时间：
1992-11-17
期刊：
影响因子：
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通讯作者：
MIAN, AM
中科院分区：
文献类型：
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作者：
SINGH, SV;XU, BH;MIAN, AM
本研究旨在阐明多药耐药细胞系P388/R-84对丝裂霉素C（MMC）交叉耐药（4.9倍）的机制。敏感细胞（P388/S）和P388/R-84细胞的MMC细胞内蓄积相当。尽管P388/R-84细胞中NADPH细胞色素P-450还原酶活性（负责MMC激活）降低了32%，但敏感细胞和耐药细胞的MMC生物还原率相似。这些结果表明，MMC耐药P388/R-84细胞系必须依赖于其他因素，而不是受损的药物积累或生物激活。最近的研究表明，谷胱甘肽转移酶（GST）依赖的药物解毒也有助于细胞耐药性的各种烷化剂。尽管在一些MMC耐药肿瘤细胞中已经注意到GST的过表达，但尚不清楚其水平是否影响对MMC的敏感性。因此，我们已经确定了依他尼酸（GST活性抑制剂）处理对MMC细胞毒性的影响，P388/R-84细胞的GST活性比P388/S细胞高约2倍。依他尼酸（EA）体外抑制GST活性的IC 50值为16.5 μ M（5 μ g/ml）。用EA单独或与MMC联合处理P388/R-84细胞也观察到细胞内GSH的耗竭。在P388/R-84细胞中，无毒浓度的EA（1 μ g/ml; 3.3 μ M）使MMC的细胞毒性增加了36%。MMC的细胞毒性增加2倍，EA处理谷胱甘肽（GSH）耗尽的P388/R-84细胞。这些结果表明，GST介导的药物失活可能是MMC耐药的另一个重要机制。
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 has 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 muM (5 mug/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 mug/ml; 3.3 muM) 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.