Sensitization of SW948-TR cells to rhTRAIL, agonistic DR4 and DR5 antibodies by MG-132. A: Apoptosis assay in SW948-TR after 17 h of incubation with MG-132 in combination with rhTRAIL, agonistic DR4 or DR5 antibody. B: The effect of MG-132 on DR4 (left figure) and DR5 (right figure) membrane expression as determined by flow cytometry. Receptor expression was detected as the average antigenic density of the whole cell population and resulted in a peak shift to the right. (1 = control; 2 = basal DR4 or DR5 membrane expression level; 3 = DR4 or DR5 expression after exposure to 10 μM MG-132 for 17 h). C: Western blot analysis of caspase 8 activation in SW948-TR after 17 h incubation with 1 μM MG-132 in combination with rhTRAIL (0.1 μg/ml), agonistic DR4 or DR5 antibody (50 nM).