Bcl-2 and Bcl-x_L overexpression but not FADD deficiency blocks proteasome inhibitor-induced apoptosis. (A) WT (▪) and FADD-deficient Jurkat cells (□) were exposed for 24 hours to 1 μg/mL FasL or to 25 μg/mL etoposide (etopo). Thereafter, cells were harvested, and dead cells were quantified by flow cytometry after staining with propidium iodide. (B) WT (, , ) and FADD-deficient Jurkat cells (, , ) were exposed for 24 hours to 0.4 μM epoxomicin (, ), 0.5 μM MG132 (, ), or 5 μM lactacystin (, ). Cell death was determined by flow cytometry analysis of propidium iodide-stained cells. (C-D) Bcl-2 (C)/Bcl-xL (D)-overexpressing Jurkat cells (, , ) and respective vector control cells (vec; , , ) were stimulated for 24 hours with 0.4 μM epoxomicin (, ), 0.5 μM MG132 (, ), or 5 μM lactacystin (, ). Cell death was determined by flow cytometry analysis of propidium iodide-stained cells. Results are presented as means of duplicates.