Activity of enzymes of glutathione metabolism and regulation by cAMP in human tumors

: Tumors were studied in 38 patients, tissues located far away from tumor being used as control. Breast and stomach tumors revealed relatively high levels of glutathione reductase, glutathione-S-transferase (I) and, particularly, gamma-glutamyl transferase (II). The said changes were not observed in colorectal tumors. Gamma-glutamyl transferase (II) may be used as a marker for breast and stomach malignancies in man but it is not a universal and absolutely specific marker for all tumors. The activity of glutathione peroxidase (III) either did not change or decreased. The activating effect of cAMP on III and I remained generally unchanged in all tumors studied.