Fig. 2. Synergistic apoptotic cell death caused by treatment with ISO and/or TRAIL. HEK 293 cells were treated with ISO (100 µM) and/or TRAIL (100 ng/mL) for 24 hours. (A and B) Apoptotic cell death of HEK 293 cells treated with ISO and/or TRAIL. The percentage of apoptotic cells was determined by FITC-annexin-V/PI staining. (C) Caspase-3 activation by ISO and TRAIL treatment. Caspase-3 activation and PARP cleavage were observed in HEK 293 cells treated with ISO and TRAIL. (D) The band intensities of cleaved cas-3 and PARP were analyzed by densitometry. GAPDH was used as the housekeeping gene. Standard error was determined on the basis of three independent experiments; ^*p<0.05. ISO: isoproterenol, TRAIL: tumor necrosis factor-related apoptosis-inducing ligand, HEK: human embryonic kidney, FITC: fluorescein isothiocynate, PI: propidium iodide, PARP: polymerase, GAPDH: glyceraldehydes-3-phosphate dehydrogenase.