Effect of the inhibition of caspase-2 expression on the activation of caspase-8, -9, -3 and -7 in SK-BR-3 and MCF-7 cells after paclitaxel and SB-T-1216 treatment. A specific caspase-2 siRNA (C2 siRNA) was used. Control cells were incubated without taxane and siRNAs. Effects of nonsense siRNA as well as caspase-2 siRNA without taxane treatment are also shown. After 24 h (SK-BR-3) or 48 h (MCF-7) of incubation with tested taxane (100 nM for SK-BR-3 cells and 300 nM for MCF-7 cells), levels of cleaved caspases were determined using western blot analysis and relevant antibodies (see “Materials and Methods”). Actin levels were used to confirm equal protein loading. The data shown were obtained in one representative experiment of two independent experiments.