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      mTOR inhibition downregulates glucose-6-phosphate dehydrogenase and induces ROS-dependent death in T-cell acute lymphoblastic leukemia cells

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          Abstract

          mTOR activation is a hallmark of T-cell acute lymphoblastic leukemia (T-ALL) and is associated with resistance to glucocorticoid (GC)-based chemotherapy. We previously showed that altering redox homeostasis primes T-ALL cells to GC-induced apoptosis. Here we investigated the connection between the mTOR pathway and redox homeostasis using pharmacological inhibitors and gene silencing.

          In vitro studies performed on T-ALL cell lines and CG-resistant patient-derived T-ALL xenograft (PDX) cells showed that the mTOR inhibitor everolimus increased reactive oxygen species (ROS) levels, augmented lipid peroxidation, and activated the ROS-controlled transcription factor NRF2. These effects were accompanied by a decrease in the levels of NADPH and of glucose-6-phosphate dehydrogenase (G6PD), the rate-limiting enzyme of the pentose phosphate pathway (PPP), which is a major source of cytosolic NADPH needed for maintaining the cellular ROS-scavenging capacity. The mTOR inhibitor everolimus induced mitochondrial inner membrane depolarization and dose-dependent apoptosis of T-ALL cells, but did not kill normal T-cells. Importantly, the combination of everolimus and the GC dexamethasone had a synergistic effect on killing T-ALL cells. The effects of mTOR inhibition were blunted by ROS scavengers and phenocopied by siRNA-mediated G6PD silencing. In vivo studies of NOD/SCID mice inoculated with refractory T-ALL PDX demonstrated that everolimus overcame dexamethasone resistance in conditions of high tumor burden that mimicked the clinical setting of acute leukemia.

          These findings provide insight into the crosstalk between mTOR and ROS homeostasis in T-ALL cells and furnish mechanistic evidence to support the combination of glucocorticoids with mTOR inhibitors as a therapeutic avenue for treating refractory T-ALL.

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          Moderated estimation of fold change and dispersion for RNA-seq data with DESeq2

          In comparative high-throughput sequencing assays, a fundamental task is the analysis of count data, such as read counts per gene in RNA-seq, for evidence of systematic changes across experimental conditions. Small replicate numbers, discreteness, large dynamic range and the presence of outliers require a suitable statistical approach. We present DESeq2, a method for differential analysis of count data, using shrinkage estimation for dispersions and fold changes to improve stability and interpretability of estimates. This enables a more quantitative analysis focused on the strength rather than the mere presence of differential expression. The DESeq2 package is available at http://www.bioconductor.org/packages/release/bioc/html/DESeq2.html. Electronic supplementary material The online version of this article (doi:10.1186/s13059-014-0550-8) contains supplementary material, which is available to authorized users.
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            Gene set enrichment analysis: A knowledge-based approach for interpreting genome-wide expression profiles

            Although genomewide RNA expression analysis has become a routine tool in biomedical research, extracting biological insight from such information remains a major challenge. Here, we describe a powerful analytical method called Gene Set Enrichment Analysis (GSEA) for interpreting gene expression data. The method derives its power by focusing on gene sets, that is, groups of genes that share common biological function, chromosomal location, or regulation. We demonstrate how GSEA yields insights into several cancer-related data sets, including leukemia and lung cancer. Notably, where single-gene analysis finds little similarity between two independent studies of patient survival in lung cancer, GSEA reveals many biological pathways in common. The GSEA method is embodied in a freely available software package, together with an initial database of 1,325 biologically defined gene sets.
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              mTOR signaling in growth control and disease.

              The mechanistic target of rapamycin (mTOR) signaling pathway senses and integrates a variety of environmental cues to regulate organismal growth and homeostasis. The pathway regulates many major cellular processes and is implicated in an increasing number of pathological conditions, including cancer, obesity, type 2 diabetes, and neurodegeneration. Here, we review recent advances in our understanding of the mTOR pathway and its role in health, disease, and aging. We further discuss pharmacological approaches to treat human pathologies linked to mTOR deregulation. Copyright © 2012 Elsevier Inc. All rights reserved.
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                Author and article information

                Contributors
                Journal
                Redox Biol
                Redox Biol
                Redox Biology
                Elsevier
                2213-2317
                24 February 2022
                May 2022
                24 February 2022
                : 51
                : 102268
                Affiliations
                [a ]Veneto Institute of Oncology IOV – IRCCS, Padova, Italy
                [b ]Department of Surgery, Oncology, and Gastroenterology, University of Padova, Padova, Italy
                [c ]Istituto Tecnico Industriale Statale “Alessandro Rossi”, Vicenza, Italy
                [d ]Pediatric Hemato Oncology, Maternal and Child Health Department, University of Padova, Padova, Italy
                [e ]Italian Institute for Genomic Medicine, Turin, Italy
                [f ]Department of Biomedical Sciences, University of Padova, Padova, Italy
                Author notes
                []Corresponding author. postal address: Oncology and Immunology Section, Department of Surgery, Oncology and Gastroenterology, University of Padova, Via Gattamelata 64, 35128 Padova, Italy. v.ciminale@ 123456unipd.it
                [1]

                Deceased.

                Article
                S2213-2317(22)00040-4 102268
                10.1016/j.redox.2022.102268
                8899410
                35248829
                9357f9c7-c65e-4576-b0a1-a8a696ac640f
                © 2022 The Authors

                This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

                History
                : 28 January 2022
                : 11 February 2022
                Categories
                Research Paper

                t-all,mtor,g6pd,ros
                t-all, mtor, g6pd, ros

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