Mcl-1 siRNA-induced sensitization to MG132-mediated apoptosis. DLD1 cells were pretreated with control siRNA or Mcl-1 siRNA for 24 h and then treated with 1 μM MG132 for another 24 h. DMSO was used as the mock control. (A) The distribution of DLD1 cells in apoptosis measured by measured by annexin-V and propidium iodide staining using flow cytometry. Representative dot plots from one experiment of three independent experiments are shown. (B) Apoptosis percentage of DLD1 cells. The value represents means ± SD of a triplicate assay. * P < 0.01 compared with control siRNA+MG132. (C) Mcl-1 siRNA enhanced MG132-induced protein cleavages for caspases-9, caspase-3 and poly (ADP-ribose) polymerase (PARP). The data presented were from one of two independent experiments with similar results.