zVAD-fmk does not totally abrogate FasL-triggered apoptosis in HeLa cells expressing caspase-10 at low level.

<p><b>A, B</b>, Casp10+ and Casp10- HeLa cells were incubated in the presence or absence of 40 µM zVAD-fmk for 1 hour and further incubated for 16 hours with or without 1 µg/mL FasL as indicated. Cells were labelled with Syto13 and propidium iodide before fluorescence microscopy examination (A). Of note, less than 5% of the cells were stained by propidium iodide under all conditions indicating that FasL-induced necrosis was marginal in HeLa cells. Percentages of cell death (i.e., cells exhibiting nuclear fragmentation and/or condensation) were determined by analysing at least 500 cells for each condition. Values are means ±SEM of three independent experiments (n.s.: not significant; **p<0.01.) (B). C, Casp10+ and Casp10- HeLa cells were incubated in the presence or absence of 40 µM zVAD-fmk for 1 hour and further incubated for 8 hours with or without 1 µg/mL FasL as indicated. Western blot analysis was performed using the indicated antibodies. (*: EGFP-tagged pro-caspase-10, **: EGFP-tagged small catalytic caspase-10 subunit).