Quantitative Analysis of Glutathione S-Transferase in Human Brain Tumors, C6 Rat Glioma Cells, and Drug Resistant C6 Cells

Abstract

Cellular detoxification of exogenous toxins, antibiotics, carcinogens, and anticancer agents involves detoxifying enzymes, such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase. Glutathione S-transferases (GST; enzymal code (EC) 2.5.1.18) compromise a group of abundant and widely distributed catalytic and binding proteins that facilitate the conjugation of glutathione (GSH) with the electrophilic center of a large spectrum of hydrophobic molecules. Multiple GST isozymes in mammalian tissues arise from dimeric combinations of a number of distinct subunits grouped into three major classes, α, µ, and π [1], GST, a π-class enzyme, has been found overexpressed in human malignant tumor tissues [2], suggesting that it may be a good tumor marker. GST is also reported to be elevated in an Adriamycin-induced multidrug resistant human breast cancer cell line (MCF-7) [3] as well as in some alkylating agent resistant cell lines [4]. Despite these reports indicating GST to possibly have a critical role in carcinogenesis and anticancer drug resistance, little is known of the role of GST in brain tumors. We report the GST activities of human brain tumors, C6 rat glioma cells, and drug resistant cells.