Figure 1.
t(4;14)-positive MM is vulnerable to class II FINs. (A) Relative expression levels of ACSL4 in t(4;14)-positive and t(4;14)-negative MM cell lines from the cancer cell line encyclopedia data set. (B) Sensitivity to RSL3 in t(4;14)-positive or -negative MM cell lines mined from the cancer therapeutics response portal version 2 database. Higher area above the drug dose-response curve % values indicate greater drug sensitivity (unpaired, 2-tailed Wilcoxon rank-sum test comparing t(4;14)-positive and -negative MM cell lines). (C) Relative cell viability of t(4;14)-positive NCI-H929, OPM-2, and KMS-11 cell lines and t(4;14)-negative U-266, MM.1S, and RPMI8226 cell lines treated with RSL3 at the indicated concentrations for 24 hours. The half-maximal inhibitory concentration (IC50) of the MM cells was calculated using GraphPad 8.0 software and is shown in the right of figure. (D) Violin plots of the relative cell viability in t(4;14)-positive NCI-H929, OPM-2, and KMS-11 cell lines and t(4;14)-negative U-266, MM.1S, and RPMI8226 cell lines treated with 1 μM RSL3 for 24 hours. (E) Relative cell viability of primary cells from patients with t(4;14)-positive MM (n = 4) and t(4;14)-negative MM (n = 4) treated with 0.5 μM RSL3. (F) Relative cell viability of t(4;14)-positive NCI-H929 and OPM-2 cells pretreated with the apoptosis inhibitor 10 μM Z-VAD-FMK (Z-VAD), the necrosis inhibitor 1 μM necrosulfonamide (NAS), the autophagy inhibitor 500 μM 3-methyladenine (3-MA), or ferroptosis inhibitors including 0.1 μM liproxstatin-1 (Lip-1), 1 μM ferrostatin-1 (Fer-1), and 10 μM deferoxamine mesylate (DFOM) for 2 hours and then treated with 0.2 μM RSL3 for 24 hours. (G-H) Lipid ROS levels of t(4;14)-positive NCI-H929 and OPM-2 cells and t(4;14)-negative U-266 cells treated with solvent (dimethylsulfoxide [DMSO]), 0.2 μM RSL3 (D0.2), or 0.5 μM RSL3 (D0.5) for 6 hours. (I) Relative PTGS2 mRNA levels of t(4;14)-positive NCI-H929 and OPM-2 cells and t(4;14)-negative U-266 cells treated with solvent (DMSO) and 0.5 μM RSL3 (RSL3) for 24 hours. (J) The relative malondialdehyde (MDA) concentrations of t(4;14)-positive NCI-H929 and OPM-2 cells and t(4;14)-negative U-266 cells treated with solvent (DMSO), 0.2 μM RSL3 (D0.2), or 0.5 μM RSL3 (D0.5) for 24 hours. (K) Electron microscopy images of t(4;14)-positive NCI-H929 and t(4;14)-negative U-266 cells treated with or without 0.5 μM RSL3 for 24 hours. The black arrowhead indicates mitochondria, which show membrane rupture and reduced cristae in t(4;14)-positive MM and relatively intact mitochondrial structure in t(4;14)-negative MM following RSL3 treatment. The levels of shrunken or ruptured mitochondria were analyzed using ImageJ software. The left scale bar: 1 μm. The right scale bar: 0.5 μm. ns, not significant; P > .05, ∗ P <0 .05, ∗∗ P < .01, and ∗∗∗ P < .001.

t(4;14)-positive MM is vulnerable to class II FINs. (A) Relative expression levels of ACSL4 in t(4;14)-positive and t(4;14)-negative MM cell lines from the cancer cell line encyclopedia data set. (B) Sensitivity to RSL3 in t(4;14)-positive or -negative MM cell lines mined from the cancer therapeutics response portal version 2 database. Higher area above the drug dose-response curve % values indicate greater drug sensitivity (unpaired, 2-tailed Wilcoxon rank-sum test comparing t(4;14)-positive and -negative MM cell lines). (C) Relative cell viability of t(4;14)-positive NCI-H929, OPM-2, and KMS-11 cell lines and t(4;14)-negative U-266, MM.1S, and RPMI8226 cell lines treated with RSL3 at the indicated concentrations for 24 hours. The half-maximal inhibitory concentration (IC50) of the MM cells was calculated using GraphPad 8.0 software and is shown in the right of figure. (D) Violin plots of the relative cell viability in t(4;14)-positive NCI-H929, OPM-2, and KMS-11 cell lines and t(4;14)-negative U-266, MM.1S, and RPMI8226 cell lines treated with 1 μM RSL3 for 24 hours. (E) Relative cell viability of primary cells from patients with t(4;14)-positive MM (n = 4) and t(4;14)-negative MM (n = 4) treated with 0.5 μM RSL3. (F) Relative cell viability of t(4;14)-positive NCI-H929 and OPM-2 cells pretreated with the apoptosis inhibitor 10 μM Z-VAD-FMK (Z-VAD), the necrosis inhibitor 1 μM necrosulfonamide (NAS), the autophagy inhibitor 500 μM 3-methyladenine (3-MA), or ferroptosis inhibitors including 0.1 μM liproxstatin-1 (Lip-1), 1 μM ferrostatin-1 (Fer-1), and 10 μM deferoxamine mesylate (DFOM) for 2 hours and then treated with 0.2 μM RSL3 for 24 hours. (G-H) Lipid ROS levels of t(4;14)-positive NCI-H929 and OPM-2 cells and t(4;14)-negative U-266 cells treated with solvent (dimethylsulfoxide [DMSO]), 0.2 μM RSL3 (D0.2), or 0.5 μM RSL3 (D0.5) for 6 hours. (I) Relative PTGS2 mRNA levels of t(4;14)-positive NCI-H929 and OPM-2 cells and t(4;14)-negative U-266 cells treated with solvent (DMSO) and 0.5 μM RSL3 (RSL3) for 24 hours. (J) The relative malondialdehyde (MDA) concentrations of t(4;14)-positive NCI-H929 and OPM-2 cells and t(4;14)-negative U-266 cells treated with solvent (DMSO), 0.2 μM RSL3 (D0.2), or 0.5 μM RSL3 (D0.5) for 24 hours. (K) Electron microscopy images of t(4;14)-positive NCI-H929 and t(4;14)-negative U-266 cells treated with or without 0.5 μM RSL3 for 24 hours. The black arrowhead indicates mitochondria, which show membrane rupture and reduced cristae in t(4;14)-positive MM and relatively intact mitochondrial structure in t(4;14)-negative MM following RSL3 treatment. The levels of shrunken or ruptured mitochondria were analyzed using ImageJ software. The left scale bar: 1 μm. The right scale bar: 0.5 μm. ns, not significant; P > .05, ∗ P <0 .05, ∗∗ P < .01, and ∗∗∗ P < .001.

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