Loss of Mcl-1 or A1 sensitizes RCC cells to apoptosis induced by ABT-737.Cells from RCC cell lines 21, 26A and 30 were transfected with 20 nM of a control siRNA or with siRNA specific for Mcl-1 (A) or A1 (siRNA 441) (B). 48 h later, cells were treated with 5 μM ABT-737 for 24 h and cell death was measured by propidium iodide staining. In some samples 100 μM zVAD-fmk was added 1 h prior to treatment with ABT-737. (C), RCC cell line 26A stably expressing Luciferase (control) or Mcl-1-specific shRNA were treated with 1 μM and 5 μM ABT-737 for 24 h and cell death was measured by propidium iodide staining. (D), Cells from RCC-26A shLuciferase and shMcl-1 were transfected with control siRNA or A1-specific siRNA (siRNA 441). 24 h post transfection cells were treated with 0.2 μM and 1 μM ABT-737 and stained with propidium iodide 24 h later. Data are mean/SEM of three independent experiments (* P < 0.04, control siRNA versus Mcl-1 siRNA and A1 siRNA; shLuciferase versus shMcl-1).