Pharmacological inhibition of IDH2 enhances sensitivity to CFZ in MM cell lines. (A) KMM-1^PIR and (B) U266^PIR cells were treated with 2.5 nM CFZ in combination or not with 10 μM AGI-6780. Cell viability was measured by TMRM staining-flow cytometry 96 hours posttreatment. Data are the means ± SD of 4 independent experiments. (C) U266^PIR50 cells were treated with 75 nM CFZ in combination or not with 10 μM AGI-6780. Cell viability was measured by TMRM staining-flow cytometry 72 hours posttreatment. Data are the means ± SD of 4 independent experiments. (D) Eight MM cell lines and the K-562 cell line were treated with CFZ (1.67 nM CFZ for KMS-18; 2.5 nM for RPMI-8226, KMS-27, SK-MM-1, and CMA-03; 5 nM for KMM-1, U266, and NCI-H929 cell lines) in combination or not with 5 μM AGI-6780 (2.5 μM for RPMI-8226). Treatment was performed every 48 hours for AGI-6780, but only at day 0 for CFZ. Cell viability was measured by TMRM staining-flow cytometry 8 days posttreatment. Data are the means ± SD of 3 independent experiments (*P < .05; **P < .01; ***P < .001; #P ≥ .05). (E) Western blot of KMM-1 and NCI-H929 cells, UT, treated with DMSO, AGI-6780 (KMM-1: 5 μM; NCI-H929: 10 μM), CFZ (KMM-1: 5 nM; NCI-H929: 2.5 nM), or a combination of the 2 drugs. Cell lysates were immunoblotted using the indicated antibodies 24 hours posttreatment. Vinculin protein expression was included for protein loading normalization. (F-G) Cell viability of the experiment described previously was measured by TMRM staining-flow cytometry 24 and 72 hpt, respectively. Cl., cleaved; hpt, hours posttreatment; UT, untreated.