Noxa reduction by RNAi specifically prevents apoptosis induction by proteasome inhibitors. Ramos Burkitt lymphoma cells were retrovirally transduced with 2 RNAi constructs targeting Noxa (N7 or N8) or GFP control. (A) Western blot demonstrating reduced Noxa expression in Ramos-N7 and-N8. Equal protein loading is shown by reprobing for β-actin. (B) Mock-, N7-, and N8-transduced Ramos FSA cells were cultured 24 hours in the presence of indicated concentration of bortezomib. Viability was assessed by annexin V/MitoTracker staining and FACS analysis. Data represent mean ± SD from 3 independent experiments. (C) Cells were incubated for 24 hours in medium containing 100 μM fludarabine (fluda), 0.25 μM staurosporine (stauro), or 5 μg/mL α-CD95, and analyzed as in panel B.