TY - JOUR
T1 - Enhanced γ-glutamylcysteine synthetase activity decreases drug-induced oxidative stress levels and cytotoxicity
AU - Das, Gokul C.
AU - Bacsi, Attila
AU - Shrivastav, Meena
AU - Hazra, Tapas K.
AU - Boldogh, Istvan
PY - 2006/9
Y1 - 2006/9
N2 - Multidrug resistance of cancer cells can be intrinsic or acquired and occurs due to various reasons, including increased repair of genotoxic damage, an enhanced ability to remove/detoxify chemical agents, or reactive oxygen species (ROS), and repression of apoptosis. Human A2780/100 ovarian carcinoma cells exhibit resistance to DNA cross-linking agents, chlorambucil (Cbl), cisplatin (Cpl), melphalan (Mel), and ionizing radiation (IR) compared to the parental cell line, A2780. In the present study, we show that when A2780/100 and A2780 cells were treated with Cbl, GSH was extruded via methionine or cystathionine-inhibitable transporters of intact plasma membrane. GSH loss was followed by a rapid increase in ROS levels. The resistant, but not drug-sensitive cells normalized the intracellular GSH concentration along with ROS levels within 4-6 h after Cbl addition, and survived drug treatment. Normalization of GSH and ROS levels in A2780/100 cells correlated well with elevated γ-glutamylcysteine synthetase (γ-GCS) activity (10 ± 1.8-fold over A2780 cells). Ectopic overexpression of the γ-GCS heavy subunit in drug-sensitive cells nearly restored GSH and ROS to pre-treatment levels consequently increased cellular resistance to genotoxic agents (Cbl, Cpl, and IR), while overexpression of γ-GCS light subunit had no such effects. Thus, in our model system, drug-resistant cells have the inherent ability to maintain increased γ-GCS activity, reestablish physiological GSH, and cellular redox state and maintain increased cellular resistance to DNA cross-linking agents and IR.
AB - Multidrug resistance of cancer cells can be intrinsic or acquired and occurs due to various reasons, including increased repair of genotoxic damage, an enhanced ability to remove/detoxify chemical agents, or reactive oxygen species (ROS), and repression of apoptosis. Human A2780/100 ovarian carcinoma cells exhibit resistance to DNA cross-linking agents, chlorambucil (Cbl), cisplatin (Cpl), melphalan (Mel), and ionizing radiation (IR) compared to the parental cell line, A2780. In the present study, we show that when A2780/100 and A2780 cells were treated with Cbl, GSH was extruded via methionine or cystathionine-inhibitable transporters of intact plasma membrane. GSH loss was followed by a rapid increase in ROS levels. The resistant, but not drug-sensitive cells normalized the intracellular GSH concentration along with ROS levels within 4-6 h after Cbl addition, and survived drug treatment. Normalization of GSH and ROS levels in A2780/100 cells correlated well with elevated γ-glutamylcysteine synthetase (γ-GCS) activity (10 ± 1.8-fold over A2780 cells). Ectopic overexpression of the γ-GCS heavy subunit in drug-sensitive cells nearly restored GSH and ROS to pre-treatment levels consequently increased cellular resistance to genotoxic agents (Cbl, Cpl, and IR), while overexpression of γ-GCS light subunit had no such effects. Thus, in our model system, drug-resistant cells have the inherent ability to maintain increased γ-GCS activity, reestablish physiological GSH, and cellular redox state and maintain increased cellular resistance to DNA cross-linking agents and IR.
KW - Drug resistance
KW - ROS
KW - γ-glutamylcysteine synthetase
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U2 - 10.1002/mc.20184
DO - 10.1002/mc.20184
M3 - Article
C2 - 16491484
AN - SCOPUS:33748809210
SN - 0899-1987
VL - 45
SP - 635
EP - 647
JO - Molecular Carcinogenesis
JF - Molecular Carcinogenesis
IS - 9
ER -