Combined treatment with adaphostin (AD) and proteosome inhibitors other than MG-132 (eg, bortezomib and ALLN) interact synergistically to induce cell death in Jurkat and U937 cells. Jurkat and U937 cells were exposed to the indicated drugs alone and in combination for 24 hours, after which the extent of apoptotic cells was determined by flow cytometric analysis after annexin V/PI staining as described in “Materials and methods.” Values represent the means plus or minus SD for 3 separate experiments performed in triplicate. Drug concentrations were as follows: Jurkat: AD, 400 nM; bortezomib, 4.0 nM; ALLN, 4.0 μM; U937: AD, 750 nM; bortezomib, 4.0 nM, ALLN, 4.0 μM.