Co-expression of gamma-glutamylcysteine synthetase sub-units in response to cisplatin and doxorubicin in human cancer cells.
Glutathione (gamma-glutamylcysteinyl glycine, GSH) is believed to be important in the acquisition of resistance to anti-cancer drugs such as cisplatin (CDDP) and doxorubicin (DOX). gamma-Glutamylcysteine synthetase (gamma-GCS) is a key enzyme for maintaining intracellular GSH levels; it is composed of a catalytic heavy (gamma-GCSh) and a regulatory light (gamma-GCSl) sub-unit. In the present study, the expression of gamma-GCS sub-units was examined in human cancer cell lines. The levels of GSH, the expression of gamma-GCSh and gamma-GCSl mRNAs and proteins in human cancer cells were higher in CDDP-resistant cells and DOX-resistant cells than in the drug-sensitive cells. Treatment of CDDP/DOX-resistant human colonic-cancer cells (HCT8DDP) with CDDP and DOX caused simultaneous induction of the expression of gamma-GCSh and gamma-GCSl mRNAs. The transcriptional regulation of gamma-GCS was studied and it was observed that the DNA-binding activity of activator protein 1 (AP-1) is induced by CDDP and DOX using an electrophoretic mobility shift assay. We constructed chimeric genes containing various regions of the gamma-GCSh-promoter gene and the coding region for luciferase. The HCT8DDP cells transiently transfected with a plasmid containing an AP-1 site of the gamma-GCSh-promoter-luciferase construct showed increased luciferase activity when treated with CDDP and DOX. These results suggest that stimulation of the expression of gamma-GCSh by CDDP and DOX is mediated by AP-1, which relates to the resistance of cancer cells to the drug.
Department of Biochemistry and Molecular Biology in Disease, Atomic Bomb Disease Institute, Nagasaki University School of Medicine, Nagasaki City, Japan.
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Iida
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Mori
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Mori
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Goto
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Urata
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Oka
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Kohno
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Kondo
D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D002945:Cisplatin / Q000008:administration & dosage; D004317:Doxorubicin / Q000008:administration & dosage; D004790:Enzyme Induction; D005721:Glutamate-Cysteine Ligase / Q000096:biosynthesis* / Q000737:chemistry; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D010446:Peptide Fragments / Q000096:biosynthesis*; D011401:Promoter Regions, Genetic; D018808:Transcription Factor AP-1 / Q000502:physiology; D014407:Tumor Cells, Cultured
D010446:Peptide Fragments; D018808:Transcription Factor AP-1; D004317:Doxorubicin; D008156:Luciferases; D005721:Glutamate-Cysteine Ligase; D002945:Cisplatin