TAK-243 reduces cell viability and induces apoptosis. (A) A panel of myeloma cell lines was exposed to either vehicle (dimethyl sulfoxide [DMSO]) or TAK-243 at the indicated nanomolar concentrations, and viability was then determined and plotted. (B) Apoptosis was evaluated after exposure to TAK-243 in MM1.S cells by staining with Annexin V and TO-PRO-3, with bortezomib (BTZ) at 10 nM as a positive control, and in the presence of TAK-243 with the pan-caspase inhibitor Z-VAD-FMK. (C) Activation of caspases-8, -9, and -3 was determined after TAK-243 exposure using fluorogenic substrates, and normalized to the vehicle control, which was arbitrarily set at 1.0. Data represent 3 independent experiments, each performed in triplicate, and are presented as the mean plus or minus SD; *P < .05 compared with the respective controls in this and panels of later figures. (D) Cleavage of caspase-7 was verified by western blotting of MM1.S cell extracts after exposure to the indicated agents. Cl. Caspase, cleaved caspase.