In the present study we have compared the levels of
glutathione (GSH) S-
transferase, GSH
peroxidase and GSH
reductase in human
breast tumors and adjacent normal tissues obtained from the same individuals. We have also quantitated GST pi type
antigen in these samples by western blotting. GST pi activity towards
1-chloro-2,4-dinitrobenzene was found to be elevated in
tumors from three out of six patients (patient nos. 2, 4 and 5), whereas this activity was suppressed in
tumor from patient no. 1. Results of Western blotting using
antibodies raised against GST pi of human placenta were in agreement with the GST activity data. GSH
peroxidase activity with
cumene hydroperoxide as substrate was found to be elevated in four
tumor samples (patient nos. 2, 4, 5, and 6) but suppressed in
tumor from patient no. 1. On the other hand, GSH
reductase activity was elevated in three samples (patients nos. 2, 4 and 5) and downregulated in the remaining three samples (patients nos. 1, 3 and 6). These results indicate that GSH-related
enzymes are differentially altered in human
breast tumors and GST pi type
isoenzyme(s), unlike certain other human
carcinomas such as colonic, are not uniformly elevated in human
breast tumors.