Premium
Co‐expression of gamma‐glutamylcysteine synthetase sub‐units in response to cisplatin and doxorubicin in human cancer cells
Author(s) -
Iida Tetsuya,
Mori Eri,
Mori Katsuharu,
Goto Shinji,
Urata Yoshishige,
Oka Mikio,
Kohno Shigeru,
Kondo Takahito
Publication year - 1999
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/(sici)1097-0215(19990730)82:3<405::aid-ijc14>3.0.co;2-m
Subject(s) - microbiology and biotechnology , luciferase , cisplatin , cancer cell , transfection , doxorubicin , biology , glutathione , cell culture , gene expression , cancer research , chemistry , cancer , enzyme , gene , biochemistry , chemotherapy , genetics
Glutathione (γ‐glutamylcysteinyl glycine, GSH) is believed to be important in the acquisition of resistance to anti‐cancer drugs such as cisplatin (CDDP) and doxorubicin (DOX). γ‐Glutamylcysteine synthetase (γ‐GCS) is a key enzyme for maintaining intracellular GSH levels; it is composed of a catalytic heavy (γ‐GCSh) and a regulatory light (γ‐GCSl) sub‐unit. In the present study, the expression of γ‐GCS sub‐units was examined in human cancer cell lines. The levels of GSH, the expression of γ‐GCSh and γ‐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 γ‐GCSh and γ‐GCSl mRNAs. The transcriptional regulation of γ‐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 γ‐GCSh‐promoter gene and the coding region for luciferase. The HCT8DDP cells transiently transfected with a plasmid containing an AP‐1 site of the γ‐GCSh‐promoter‐luciferase construct showed increased luciferase activity when treated with CDDP and DOX. These results suggest that stimulation of the expression of γ‐GCSh by CDDP and DOX is mediated by AP‐1, which relates to the resistance of cancer cells to the drug. Int. J. Cancer 82:405–411, 1999. © 1999 Wiley‐Liss, Inc.