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.
Iida
T
T
Department of Biochemistry and Molecular Biology in Disease, Atomic Bomb Disease Institute, Nagasaki University School of Medicine, Nagasaki City, Japan.
Mori
E
E
Mori
K
K
Goto
S
S
Urata
Y
Y
Oka
M
M
Kohno
S
S
Kondo
T
T
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