Etoposide sensitizes RCC cells for cytochrome c -release by ABT-737 from mitochondria.(A), (B), RCC-26A cells were cultured in complete medium (untreated) or treated with 200 μM etoposide or 1 mM 5-FU for 24 h. Cells were permeabilized with 200 μg/ml digitonin in the presence of solvent (DMSO, control), a peptide encompassing the Bim BH3-domain (100 μM) or ABT-737 (concentrations as shown, 50 μM in A). Reactions were separated into supernatants and insoluble pellets and fractions were analyzed by Western blotting for cytochrome c. Membranes were re-probed with a Bak-specific antibody as mitochondrial marker. P, pellet fractions, containing cytochrome c retained by mitochondria. S, supernatant fractions, containing released cytochrome c.