Localization of the placental form of glutathione S-transferase messenger ribonucleic acid in human glioma cell lines.

Localization of the placental form of glutathione S-transferase (GST-pi) messenger ribonucleic acid (mRNA) in three human glioma cell lines (A172, T98G, and Tc77) was studied by in situ hybridization with digoxigenin-labeled GST-pi complementary DNA followed by immunocytochemistry with antidigoxigenin antibody. A172 glioma cells showed hardly any GST-pi mRNA. GST-pi mRNA was recognized in the cytoplasm of T98G and Tc77 glioma cells. Tc77 cells especially had a strong expression of GST-pi mRNA. GST activity and the expression of GST-pi protein were also investigated for these cell lines. Cytosolic GST activity was determined with 1-chloro-2,4-dinitrobenzene as substrate, and the results were as follows: A172, 24.3 +/- 2.0; T98G, 60.8 +/- 4.9; Tc77, 84.0 +/- 1.7 (mean +/- standard deviation, in nanomoles per minute per milligram of protein). The expression level of GST-pi protein analyzed by Western blotting with anti-GST-pi antibody as a primary antibody was compatible with the results of both in situ hybridization of GST-pi mRNA and GST activity. A172 cells possessing the lowest GST activity showed a weak expression of both GST-pi mRNA and protein. Tc77 cells with the highest GST activity had the strongest expression of GST-pi mRNA and protein in three cell lines. The GST-pi expression of T98G cells was moderate. These findings indicate that some human glioma cells have GST-pi expression and that GST-pi in glioma cells is the major isozyme of GSTs for the significant activity of glutathione conjugation.