Etoposide triggers caspase-3-dependent apoptosis in SK-N-AS cells. A, cells
were treated with 50 μM etoposide for 48 h and harvested. The cytosolic
fractions were obtained by a digitonin-based subcellular fractionation
procedure. One hundred micrograms of cytosolic (Cy) and mitochondrial protein
fractions (Mi) was analyzed by SDS-polyacrylamide gel electrophoresis, and
cytochrome c and β-actin levels were determined by
immunoblotting. B, immunoblot analysis of caspase-9 and β-actin in cell
lysates treated with 50 μM etoposide for 48 h. C, immunoblot analysis of
caspase-3 and β-actin in cell lysates treated with 50 μM etoposide
with or without 20 μM caspase-9 inhibitor (z-LEHD-fmk) for 48 h. D,
immunoblot analysis of PKCδ and β-actin in cell lysates treated
with 50 μM etoposide with or without 20 μM caspase-3 inhibitor
(z-DEVD-fmk) for 48 h. E, immunoblot analysis of caspase-3 and β-actin in
cell lysates treated with or without 2 μM rottlerin, 50 μM etoposide, or
2 μM rottlerin and 50 μM etoposide for 48 h. F, cells were treated with
50 μM etoposide with or without 20 μM caspase-3 inhibitor (z-DEVD-fmk)
for 48 h, and the percentage of apoptotic cells was quantified by counting
fragmented nuclei stained with Hoechst 33342 among 200 cells. Shown are
representative apoptosis rates from three independent counts.