FIG. 1.

Synergistic apoptotic response following combined treatment with etoposide and TRAIL. (A) HEK293 cells were treated with 100 μM etoposide, 200 ng of sTRAIL per ml, or both for 16 h. Untreated cells were designated the control. Cells were visualized by digital confocal microscopy by using a ×40 water objective for each treatment tested. (B) HEK293, T47D, ZR-75-1, and MDA-MD-468 cells were treated with 100 μM etoposide, 200 ng of sTRAIL per ml, or both for 16 h, and the percentage of apoptotic cells was determined. The cells were stained with acridine orange and counted by using a fluorescence microscope to quantitate condensed DNA. Cells having condensed DNA were scored as apoptotic (a total of 250 cells for each treatment were scored). All experiments were repeated three times. Error bars represent the standard deviations for three independent experiments.