Effects of MCL-1–specific siRNA on neoplastic mast cells. Effects of MCL-1-siRNA on MCL-1 protein expression (A, C) and cell viability (B, D) in HMC-1.1 cells (A-B) and HMC-1.2 cells (C-D). Cells were left untransfected (Control) or were transfected with an MCL-1–specific siRNA (MCL-1-siRNA; 200 nM) or a luciferase-specific (control) siRNA (luc-siRNA; 200 nM). MCL-1 protein expression (A, C) was determined after 12 hours by Western blotting using a polyclonal anti–MCL-1 antibody. Equal loading was confirmed by probing for β-actin. Cell viability was analyzed by recording the percentage of apoptotic cells. Results represent the mean ± SD from 3 independent experiments in each set of experiments (C-D).