Lomitapide enhances cytotoxic effects of temozolomide in chemotherapy-resistant glioblastoma
Alyona Ivanova, Taylor M. Wilson, Kimia Ghannad-Zadeh, Esmond Tse, Robert Flick, Megan Wu, Sunit Das
Alyona Ivanova, Taylor M. Wilson, Kimia Ghannad-Zadeh, Esmond Tse, Robert Flick, Megan Wu, Sunit Das
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Research Article Cell biology Oncology

Lomitapide enhances cytotoxic effects of temozolomide in chemotherapy-resistant glioblastoma

Abstract

More than a third of patients with glioblastoma experience tumor progression during adjuvant therapy. In this study, we performed a high-throughput drug repurposing screen of FDA-approved agents capable of crossing the blood-brain barrier in order to find agents to counteract acquired or inherent glioma cell resistance to temozolomide-associated cytotoxicity. We identified the cholesterol processing inhibitor, lomitapide, as a potential chemosensitizer in glioblastoma. In vitro treatment of temozolomide-resistant glioblastoma cells with lomitapide resulted in decreased intracellular ubiquinone levels and sensitized cells to temozolomide-induced ferroptosis. Concomitant treatment with lomitapide and temozolomide (TMZ) prolonged survival and delayed tumor recurrence in a mouse glioblastoma model, compared with treatment xwith TMZ alone. Our data identified lomitapide as a potential adjunct for treatment of temozolomide-resistant glioblastoma.

Authors

Alyona Ivanova, Taylor M. Wilson, Kimia Ghannad-Zadeh, Esmond Tse, Robert Flick, Megan Wu, Sunit Das

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Figure 7

Lomitapide treatment primes glioma cells for ferroptosis.

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Lomitapide treatment primes glioma cells for ferroptosis. (A) Mevalonate...
(A) Mevalonate pathway inhibition by lomitapide depletes the levels of key antioxidant — CoQ10 — contributing to ROS accumulation. Lomitapide treatment causes overexpression of DMT1, which promotes increase in lipid peroxide levels through fenton reaction. In an adaptive response, GPX4 activity rises to prevent oxidative damage. GPX4 reduces lipid hydroperoxides (PUFA-OOH) to alcohols (PUFA-OH) and then supplements its active site residues through GSH synthesized from cys pumped by system xCT. Expression of glutamate-cystine antiporter is controlled by KEAP1, a critical defense against ferroptosis. Lomitapide primes the cells for ferroptosis. (B) Relative CoQ10 concentration in CTL- and TR-U251 cells following 24- and 48-hour lomitapide treatment (2 μM). (C) Cellular ROS production in CTL-U251, TR-U251, HEK293, and NHA cells treated with 2 μM lomitapide for 24 and 48 hours. (D) Flow cytometry analysis of membrane lipid peroxidation on U251 cells treated with 2 μM lomitapide for 24 and 48 hours. (See Supplemental Figure 3). (E) Relative GPX4 activity in cells treated with 2 μM lomitapide for 24 and 48 hours. Untargeted LC-MS results showing GSH/GSSG ratio (F), relative concentrations of oxidative stress (G); ferroptosis markers (H); D-glutamate (I) in CTL-U251 and TR-U251 cells treated with 2 μM lomitapide for 72 hours. The data is normalized to untreated control. The data are represented as individual measurements with mean ± SD. One-way ANOVA, followed by post hoc Tukey’s HSD test, used for multiple group comparisons. Cys, cystine; GPX4, Glutathione peroxidase 4; GSH, glutathione; GR, glutathione reductase; xCT, system xCT (glutamate-cystine antiporter); GSSG, glutathione disulfide; NADPH, reduced nicotinamide adenine dinucleotide phosphate; NADP+, nicotinamide adenine dinucleotide phosphate; KEAP1, Kelch-like ECH-associated protein 1; DMT1, divalent metal transporter 1; IPP, isopentenyl diphosphate; PUFA-OOH, polyunsaturated fatty acid hydroperoxide; PUFA-OH, polyunsaturated fatty acid alcohol; HMGCR, 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase; MDA, malondialdehyde; HA, hydroxy acrylic acid; CSSC, cysteine glutathione disulfide; H-γ-Glu-Cys-OH, γ-L-Glutamyl-L-cysteine; NAC, N-Acetyl-L-cysteine; NT, no treatment; Lo, 2 μM lomitapide. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.