KPT-9274 triggers apoptotic cell death in myeloma cells. (A) OPM2 cells were cultured in the absence or presence of KPT-9274, and apoptotic cell death was assessed by flow cytometric analysis following AnnexinV and PI staining. The percent of AnnexinV⁺/PI⁻ (early apoptosis) and AnnexinV⁺/PI⁺ (late apoptosis) cells are shown in the graphs. (B) Whole cell lysate from OPM2 cells treated with several concentrations of KPT-9274 for 48 hours was subjected to WB analysis and probed with antibodies against caspases-3, -8, -9, poly-ADP ribose polymerase, with β-actin as loading control. (C-D) Indicated caspase activities were evaluated in OPM2 cells (C) and CD138⁺ cells from 4 MM patients (D) after KPT-9274 treatment (0.5 µM) for 48 and/or 72 hours using luminescence assay. (E) OPM2 cells were cultured in the presence or absence of zVAD-fmk (100 µM) with or without KPT-9274 for 48 hours. Apoptosis was evaluated by flow cytometric analysis following Annexin V and PI staining. The percent of AnnexinV⁺ cells is shown in the graph.