Effects of antisense epidermal growth factor receptor (EGFR) sequence on apoptotic cell death were examined in a human hepatoma cell line BEL-7404 cells. In the cells of JX-1, a sub clone of BEL-7404 stably transfected with antisense EGFR vector (Cell Research, 3:75, 1993), an enhanced rate (9.5%) of spontaneous apoptosis was detected by flow cytometry, whereas the rates of spontaneous apoptosis in JX-0 cells, a sub-clone of BEL-7404 transfected by control vector, and the parellt BEL-7404 cells were almost equal and about 1.7%. Serum-starvation for 72 h increased the rate of apoptosis of JX-1cells up to 33.7%, while JX-0 and BEL-7404 cells, under the same condition, produced less than 5% of apoptotic cells. Observation with electron microscope demonstrated that condensation and fragmentation of chromatin and formation of apoptotic bodies of ten occurred in JX-1 cells, especially during serumstarvation. These results, combined with the data of DNA fragmentation Elisa test, suggested that antisense EGFR sequence enhances apoptosis in the human hepatoma cells.Comparison of intracellular Ca2+ level and the responsiveness of JX-1 cells to the induced action of EGF and tharpsigargin (TG) treatment with that of control JX-0cells indicated that antisense EGFR might interrupt the EGF/EGFR signaling pathway resulting in the decreass of intracellular Ca2+ pool content as well as the responsiveness of these cells to the extracellular signals. These findings suggest that antisense EGFR either directly or indirectly reglllates Ca2+ storage in endoplasmic reticulum,thereby enhances apoptosis in the hnman hepatoma cells. Effects of antisense epidermal growth factor receptor (EGFR) sequence on apoptotic cell death were examined in a human hepatoma cell line BEL-7404 cells. In the cells of JX-1, a sub clone of BEL-7404 stably transfected with antisense EGFR vector Cell Research, 3:75, 1993), an enhanced rate (9.5%) of spontaneous apoptosis was detected by flow cytometry, while the rates of spontaneous apoptosis in JX-0 cells, a sub-clone of BEL- 7404 transfected by control vector , and the parellt BEL-7404 cells were almost equal and about 1.7%. Serum-starvation for 72 h increased the rate of apoptosis of JX-1 cells up to 33.7% while JX-0 and BEL- 7404 cells, under the same condition , with less than 5% of apoptotic cells. Observation with electron microscope demonstrated that condensation and fragmentation of chromatin and formation of apoptotic bodies of ten occurred in JX-1 cells, especially during serum starvation. These results, combined with the data of DNA fragmentation Elisa test, suggested tha t antisense EGFR sequence enhances apoptosis in the human hepatoma cells. Comparison of intracellular Ca2 + level and the responsiveness of JX-1 cells to the induced action of EGF and tharpsigargin (TG) treatment with that of control JX-0 cells indicating that antisense EGFR might interrupt the EGF / EGFR signaling pathway resulting in the decrement of intracellular Ca2 + pool content as well as the responsiveness of these cells to the extracellular signals. These findings suggest that antisense EGFR either directly or indirectly reglllates Ca2 + storage in endoplasmic reticulum, thereby enhancings apoptosis in the hnman hepatoma cells.