ISOENZYME-SPECIFIC QUANTITATIVE IMMUNOASSAYS FOR CYTOSOLIC GLUTATHIONE TRANSFERASES AND MEASUREMENT OF THE ENZYMES IN BLOOD-PLASMA FROM CANCER-PATIENTS AND IN TUMOR-CELL LINES

Enzyme-linked immunoassays (ELISAs) based on the double-antibody sandw ich technique have been developed for the quantitative analysis of the major human cytosolic class Pi, Mu and Alpha glutathione transferases (GSTs). The procedures were optimized with respect to antibody concen tration for coating of plates as well as other parameters in order to achieve high sensitivity and accuracy. No cross-reactivity was detecte d between members of the three different classes of GSTs or among the Mu class GSTs M2-2, M3-3 and M4-4 with the ELISA for GST M1-1. The ELI SAs have been applied to establish the cytosolic GST profiles of 10 ce ll lines and to monitor the plasma GST levels in cancer patients. The results revealed that the class Pi GST was the dominant isoenzyme in s ix (LS 174T, HCT-8, Hu 549 Pat, K-562, U-937 and Hu 549) out of nine t umor cell lines and immortalized hepatocytes (Chang Liver). The isoenz ymes A1-1 and M1-1 were determined to be the major GST components in H ep G2 and HeLa cells, respectively. In a clinical study, the majority of the patients with urinary bladder cancer were found to have increas ed plasma levels of both GST A1-1 and GST P1-1 (10/15), while patients with renal cancer frequently showed increases only in GST P1-1 (5/8). The results demonstrate that the ELISAs are suitable for analyzing GS T phenotypes in both normal and tumor cells and in monitoring plasma l evels of GSTs in cancer patients.