Samples cultured with different concentrations of bortezomib with or without Z-VAD-FMK were acquired with a calibrated number of Trucount Tubes with fluorescent beads in order to calculate the absolute count of annexin V–PE–positive and/or 7-AAD–positive cells. The following equation was used: (number of events contained in annexin V–PE plus 7-AAD–negative region/number of events in absolute count bead region) × (number of beads per test/test volume). The numbers specified in the figures represent the number of beads in each test and the number of events in the annexin V–PE–positive and/or 7-AAD–positive region. The absolute number of annexin V–PE–positive and/or 7-AAD–positive events, which correspond to apoptotic cells, decreased a mean of 11%, 29%, and 49% in the presence of the pancaspase inhibitor after exposure to concentrations of 10, 100, and 1000 nM bortezomib, respectively (P < .05 for 100 and 1000 nM). Similar values were observed when only annexin V–PE–positive cells were analyzed.