Targeting mitochondrial energetics reverses panobinostat- and marizomib-induced resistance in pediatric and adult high-grade gliomas

by Selleckchem | Jun 12 2023

In previous studies, we demonstrated that panobinostat, a histone deacetylase inhibitor, and bortezomib, a proteasomal inhibitor, displayed synergistic therapeutic activity against pediatric and adult high-grade gliomas. Despite the remarkable initial response to this combination, resistance emerged. Here, in this study, we aimed to investigate the molecular mechanisms underlying the anticancer effects of panobinostat and marizomib, a brain-penetrant proteasomal inhibitor, and the potential for exploitable vulnerabilities associated with acquired resistance. RNA sequencing followed by gene set enrichment analysis (GSEA) was employed to compare the molecular signatures enriched in resistant compared with drug-naïve cells. The levels of adenosine 5'-triphosphate (ATP), nicotinamide adenine dinucleotide (NAD)+ content, hexokinase activity, and tricarboxylic acid (TCA) cycle metabolites required for oxidative phosphorylation to meet their bioenergetic needs were analyzed. Here, we report that panobinostat and marizomib significantly depleted ATP and NAD+ content, increased mitochondrial permeability and reactive oxygen species generation, and promoted apoptosis in pediatric and adult glioma cell lines at initial treatment. However, resistant cells exhibited increased levels of TCA cycle metabolites, which required for oxidative phosphorylation to meet their bioenergetic needs. Therefore, we targeted glycolysis and the electron transport chain (ETC) with small molecule inhibitors, which displayed substantial efficacy, suggesting that resistant cell survival is dependent on glycolytic and ETC complexes. To verify these observations in vivo, lonidamine, an inhibitor of glycolysis and mitochondrial function, was chosen. We produced two diffuse intrinsic pontine glioma (DIPG) models, and lonidamine treatment significantly increased median survival in both models, with particularly dramatic effects in panobinostat- and marizomib-resistant cells. These data provide new insights into mechanisms of treatment resistance in gliomas.

Comments:

In this study, the researchers investigated the molecular mechanisms underlying the therapeutic effects of panobinostat, a histone deacetylase inhibitor, and marizomib, a brain-penetrant proteasomal inhibitor, against high-grade gliomas in both pediatric and adult patients. They aimed to understand the development of resistance to this drug combination and identify potential vulnerabilities that could be exploited to overcome resistance.

To study the molecular signatures associated with acquired drug resistance, the researchers performed RNA sequencing followed by gene set enrichment analysis (GSEA) comparing resistant cells with drug-naïve cells. They found that resistant cells displayed distinct molecular signatures compared to the drug-naïve cells.

Furthermore, the researchers analyzed the levels of adenosine 5'-triphosphate (ATP) and nicotinamide adenine dinucleotide (NAD+) content, as well as the activity of hexokinase and metabolites involved in the tricarboxylic acid (TCA) cycle required for oxidative phosphorylation. They discovered that panobinostat and marizomib treatment significantly depleted ATP and NAD+ content, increased mitochondrial permeability, reactive oxygen species (ROS) generation, and induced apoptosis in glioma cell lines during initial treatment.

However, the resistant cells exhibited increased levels of TCA cycle metabolites, indicating their dependence on oxidative phosphorylation for bioenergetic needs. To target the metabolic alterations in resistant cells, the researchers used small molecule inhibitors to disrupt glycolysis and the electron transport chain (ETC). These inhibitors showed significant efficacy, suggesting that resistant cell survival is reliant on glycolysis and ETC complexes.

To validate their findings in an in vivo model, the researchers used lonidamine, an inhibitor of glycolysis and mitochondrial function. They generated two models of diffuse intrinsic pontine glioma (DIPG) and treated them with lonidamine. The treatment with lonidamine significantly increased median survival in both models, with particularly remarkable effects observed in panobinostat- and marizomib-resistant cells.

Overall, this study provides new insights into the mechanisms of treatment resistance in gliomas. The findings suggest that targeting glycolysis and mitochondrial function could be a potential strategy to overcome resistance to panobinostat and marizomib combination therapy in high-grade gliomas.