MEK/ERK pathway deregulation mediates KPT-9274–induced MM cell death. (A) Whole cell lysates from OPM2 cells treated with several concentrations of KPT-9274 for 48 hours were subjected to WB analysis and probed with indicated antibodies. (B) MM1S, KMS11, OPM2, and U266 cells were electroporated with control or NF-κB luciferase reporter plasmid and pRL-TK to normalize for different transfection efficiencies; following electroporation, cells were treated with vehicle or 2 doses of KPT-9274. Forty-eight hours later, luminescence was measured using the Dual Luciferase assay kit and the Glo-Max microplate luminometer. Results are expressed as percentage of Firefly/Renilla ratio of control-transfected cells. (C) H929, KMS11, and U266 cells were electroporated with control or serum response element (SRE) reporter vector. Dual Luciferase assay was performed after 48 hours of incubation with or without KPT-9274. Results are expressed as percentage of Firefly/Renilla ratio of control-transfected cells. (D) Relative mRNA expression of differentially expressed genes after KPT-9274 treatment in OPM2 and KMS11 cell lines compared with untreated cells. (E) Nuclear extracts from KPT-9274–treated OPM2 cells were analyzed for transcription factor activation using a transcription factor profiling array. Relative fold changes from control are plotted. (F) OPM2 cells were treated with different concentrations of KPT-9274 in combination with either U0126 (10 µM) or LY29004 (10 µM) or Rapamycin (10 µM) for 48 hours. Cell viability was assessed by CTG uptake and presented as percent compared with control cells.