Coadministration of pan-AKIs and TRAIL activates the caspase cascade in MM. (A) HMCLs were treated with pan-AKIs for 3 hours and then incubated with TRAIL (2.4 ng/mL in RPMI 8226 and OPM-2, 9.6 ng/mL in RPMI 8226/R5 and U266, 300 ng/mL in JJN3) for 24 hours, after which cells were lysed and subjected to western blot analysis to monitor the expression of PARP, cleaved-PARP, cleaved caspase-8, Bid, truncated Bid (t-Bid), cleaved caspase-9, and cleaved caspase-3; blots were subsequently reprobed for actin expression to ensure equivalent loading and transfer of proteins. (B) HMCLs were cultured with pan-AKIs and TRAIL at the doses indicated in A in the presence or absence of 30 μM caspase inhibitors for 24 hours, after which the percentage of apoptotic cells was determined by the annexin-V method. Data represent means ± SD of 3 independent experiments (*P < .05; **P < .005 vs pan-AKIs/TRAIL Z-FA-FMK; Dunnet test).