HIGH-RATES OF THIOREDOXIN SECRETION CORRELATE WITH GROWTH ARREST IN HEPATOMA-CELLS

Thioredoxin (TRX), a disulfide-reducing intracellular dithiol enzyme, is synthesized by both normal liver cells and the hepatocarcinoma cell Line HepG2. Only the former, however, secrete abundant TRX extracellu larly. When cultured in mild reducing conditions, HepG2 cells but not normal hepatocytes increase the rate of TRY secretion and undergo grow th inhibition accompanied by morphological changes. Also, recombinant TRX inhibits proliferation of HepG2 cells. In contrast, exogenous thio ls and TRX stimulate proliferation of a B-cell lymphoma line, indicati ng that different cell. types respond differently to variations in the extracellular redox potential.