Elevation of glutathione transferase activity in human lung tumor.

Glutathione transferase activity in the cytosolic fractions of human lung tumors was found to be significantly higher than that present in the corresponding non-tumor cytosolic fractions. The relative activities of 'cationic', 'near-neutral' and 'acidic' glutathione transferases of both tumor and non-tumor cytosols were estimated after isoelectric focusing. More than 90% of activity in both tumor and non-tumor cytosols was found to be associated with the 'acidic' (pI 4.6) activity peak. In the chromatogram of tumor tissues the activity associated with the 'acidic' peak was found to be increased in comparison with non-tumor tissues. When the protein fractions associated with the 'acidic' peak of both tumor and non-tumor tissues were tested against the antibodies raised against human placenta transferase (transferase pi) a continuous precipitin line was obtained. An increased amount of immunoreactive glutathione transferase was also found in tumor cytosols as compared with non-tumor cytosols. Thus, our studies indicate that the predominant glutathione transferase of human lung appears to be electrophoretically and immunologically very similar or identical to transferase pi and that the elevation of transferase activity measured in the lung tumor cytosols was mainly due to increased quantity of this isoenzyme.