For the activation of caspase-6, cells were stressed with 50 nM staurosporine for 0-6 h and harvested by trypsinization. Cell pellets were lysed in 50 mM Tris pH 8, 150 mM NaCl and 1% Igepal with 4.2 mM Pefabloc and 'Complete' protease inhibitor cocktail (Roche) on ice, and protein concentrations were determined in the cleared lysates after centrifugation.