Targeting the MPC complex exacerbates BTZ-induced apoptosis of MM cells. (A) JJN3 and U266 cells were treated with BTZ (4 nM) for 48 hours, followed by an assessment of cell viability via PI staining (n = 5). Significance was determined using one-way ANOVA followed by a Dunnett test. ∗P ≤ .05; ∗∗P ≤ .005; ∗∗∗P ≤ .005. (B) Representative flow cytometry analysis of JJN3 and U266 cells treated with either DMSO or BTZ (4 nM) for 48 hours and stained with annexin-V/PI. (C) Representation of the annexin-V/PI analysis displayed in panel B for both JJN3 (n = 8) and U266 cells (n = 9). Significance was determined using two-way ANOVA followed by a Dunnett test. ∗P ≤ .05; ∗∗∗P < .0001. (D) Similar to panel C, except that BTZ was replaced by CFZ (4 nM) for both JJN3 (n = 5) and U266 cells (n = 5). Significance was determined using two-way ANOVA followed by a Dunnett test. ∗P ≤ .0005. (E) Schematic representing UK-5099 inhibiting pyruvate entry into the mitochondrial matrix via MPC1 and MPC2. (F) JJN3 (n = 4), U266 (n = 5), RPMI-8266 (n = 3), KMS-12-BM (n = 3), and 5TGM1 cells (n = 5) were treated with BTZ (3 nM) and UK-5099 (10 μM) for 48 hours, followed by an assessment of cell viability via PI. Significance was determined using two-way ANOVA followed by a Dunnett test. ∗P ≤ .05; ∗∗P ≤ .005. (G) Representative flow cytometry analysis of JJN3 and U266 cells treated with either BTZ (3 nM) and UK-5099 (10 μM) for 48 hours and stained with annexin-V/PI. (H) Representation of the annexin-V/PI analysis displayed in panel G for both JJN3 (n = 5) and U266 cells (n = 6). Significance was determined using two-way ANOVA followed by a Dunnett test. ∗P ≤ .05; ∗∗P ≤ .005.