MECHANISM OF APOPTOTIC CELL-DEATH OF HUMAN GASTRIC-CARCINOMA CELLS MEDIATED BY TRANSFORMING-GROWTH-FACTOR-BETA

Human gastric carcinoma cell line HSC-39 has been shown to undergo apo ptotic cell death in response to treatment with transforming growth fa ctor beta(1) (TGF-beta(1)). To understand better the cell death mechan ism in this TGF-beta(1)-mediated apoptosis, we investigated the effect of the expression of TGF-beta-stimulated clone 22 (TSC-22) on cell de ath events. TGF-beta(1) induced TSC-22 gene expression in HSC-39 cells only when the cells had previously been adapted to the serum-free cul ture conditions required to undergo TGF-beta(1)-mediated apoptosis. HS C-39 cells transfected with a TSC-22 expression vector showed a signif icant decrease in cell viability compared with those transfected with: a control vector. The cellular events characteristic of apoptosis, ch romatin condensation and DNA fragmentation were observed only in cells transfected with a TSC-22 expression vector. On immune-staining of th e transfected cells, almost every cell that expressed TSC-22 tagged wi th influenza virus haemagglutinin exhibited the morphology of an apopt otic cell. Partial protection from the cell death effect of TGF-beta(1 ) on HSC-39 cells was observed when cells were treated with acetyl-L-a spartyl-L-glutamyl-L-valyl-L-aspart-l-al (Ac-DEVD-CHO, an inhibitor sp ecific for CPP32-type protease). Protection against eel death by the t ransfection of a TSC-22 expression vector was also offered by Ac-DEVD- CHO addition. These results suggest that TSC-22 elicits the apoptotic cell death of human gastric carcinoma cells through the activation of CPP32-like protease and mediates the TGF-beta(1) signalling pathway to apoptosis.