Dual inhibition of CPT1A and G6PD suppresses glioblastoma tumorspheres.

PURPOSE: Limited treatment options are currently available for glioblastoma (GBM), an extremely lethal type of brain cancer. For a variety of tumor types, bioenergetic deprivation through inhibition of cancer-specific metabolic pathways has proven to be an effective therapeutic strategy. Here, we evaluated the therapeutic effects and underlying mechanisms of dual inhibition of carnitine palmitoyltransferase 1A (CPT1A) and glucose-6-phosphate dehydrogenase (G6PD) critical for fatty acid oxidation (FAO) and the pentose phosphate pathway (PPP), respectively, against GBM tumorspheres (TSs). METHODS: Therapeutic efficacy against GBM TSs was determined by assessing cell viability, neurosphere formation, and 3D invasion. Liquid chromatography-mass spectrometry (LC-MS) and RNA sequencing were employed for metabolite and gene expression profiling, respectively. Anticancer efficacy in vivo was examined using an orthotopic xenograft model. RESULTS: CPT1A and G6PD were highly expressed in GBM tumor tissues. Notably, siRNA-mediated knockdown of both genes led to reduced viability, ATP levels, and expression of genes associated with stemness and invasiveness. Similar results were obtained upon combined treatment with etomoxir and dehydroepiandrosterone (DHEA). Transcriptome analyses further confirmed these results. Data from LC-MS analysis showed that this treatment regimen induced a considerable reduction in the levels of metabolites associated with the TCA cycle and PPP. Additionally, the combination of etomoxir and DHEA inhibited tumor growth and extended survival in orthotopic xenograft model mice. CONCLUSION: Our collective findings support the utility of dual suppression of CPT1A and G6PD with selective inhibitors, etomoxir and DHEA, as an efficacious therapeutic approach for GBM.

Etomoxir, a carnitine palmitoyltransferase 1 inhibitor, combined with temozolomide reduces stemness and invasiveness in patient-derived glioblastoma tumorspheres.

INTRODUCTION: The importance of fatty acid oxidation (FAO) in the bioenergetics of glioblastoma (GBM) is being realized. Etomoxir (ETO), a carnitine palmitoyltransferase 1 (CPT1) inhibitor exerts cytotoxic effects in GBM, which involve interrupting the FAO pathway. We hypothesized that FAO inhibition could affect the outcomes of current standard temozolomide (TMZ) chemotherapy against GBM. METHODS: The FAO-related gene expression was compared between GBM and the tumor-free cortex. Using four different GBM tumorspheres (TSs), the effects of ETO and/or TMZ was analyzed on cell viability, tricarboxylate (TCA) cycle intermediates and adenosine triphosphate (ATP) production to assess metabolic changes. Alterations in tumor stemness, invasiveness, and associated transcriptional changes were also measured. Mouse orthotopic xenograft model was used to elucidate the combinatory effect of TMZ and ETO. RESULTS: GBM tissues exhibited overexpression of FAO-related genes, especially CPT1A, compared to the tumor-free cortex. The combined use of ETO and TMZ further inhibited TCA cycle and ATP production than single uses. This combination treatment showed superior suppression effects compared to treatment with individual agents on the viability, stemness, and invasiveness of GBM TSs, as well as better downregulation of FAO-related gene expression. The results of in vivo study showed prolonged survival outcomes in the combination treatment group. CONCLUSION: ETO, an FAO inhibitor, causes a lethal energy reduction in the GBM TSs. When used in combination with TMZ, ETO effectively reduces GBM cell stemness and invasiveness and further improves survival. These results suggest a potential novel treatment option for GBM.

Combinatorial Therapeutic Effect of Inhibitors of Aldehyde Dehydrogenase and Mitochondrial Complex I, and the Chemotherapeutic Drug, Temozolomide against Glioblastoma Tumorspheres.

Resident cancer cells with stem cell-like features induce drug tolerance, facilitating survival of glioblastoma (GBM). We previously showed that strategies targeting tumor bioenergetics present a novel emerging avenue for treatment of GBM. The objective of this study was to enhance the therapeutic effects of dual inhibition of tumor bioenergetics by combination of gossypol, an aldehyde dehydrogenase inhibitor, and phenformin, a biguanide compound that depletes oxidative phosphorylation, with the chemotherapeutic drug, temozolomide (TMZ), to block proliferation, stemness, and invasiveness of GBM tumorspheres (TSs). Combination therapy with gossypol, phenformin, and TMZ induced a significant reduction in ATP levels, cell viability, stemness, and invasiveness compared to TMZ monotherapy and dual therapy with gossypol and phenformin. Analysis of differentially expressed genes revealed up-regulation of genes involved in programmed cell death, autophagy, and protein metabolism and down-regulation of those associated with cell metabolism, cycle, and adhesion. Combination of TMZ with dual inhibitors of tumor bioenergetics may, therefore, present an effective strategy against GBM by enhancing therapeutic effects through multiple mechanisms of action.