(A) HEK-293T cells were co-transfected with DR4 and/or MEX expression plasmids in the presence of pEF-BOS-β-gal. After 24 h of transfection, the cells were fixed and stained for β-gal activity. Arrows show round-up apoptotic cells with membrane blebbing. (B) and (C) HEK-293T cells were co-transfected with control vector, DR3, DR4, BimEL, or Fas expression plasmids and wild-type MEX (WT), MEX mutant with replacement of critical cysteine residue in the SWIM domain (C66S), IKKβ K44A (IKK mt), caspase-8-C377S (Casp8 mt), caspase-9-C287S (Casp9mt), or vector control in the presence of pEF-BOS-β-gal. The cells transfected with Fas were treated with 1 μg/ml trimerized Fas ligand (C). As an additional control, cells transfected with wild-type MEX or vector control were treated with 0.1 μg/ml adriamycin (Ad). After 24 h of transfection, the percentage of apoptotic cells±S.D. was calculated in triplicate cultures.