Glioblastoma Metabolism Research Articles

Dual-targeting of aberrant glucose metabolism in glioblastoma.

BackgroundGlioblastoma (GBM) is the most common and malignant primary brain tumor. In contrast to some other tumor types, aberrant glucose metabolism is an important component of GBM growth and chemoresistance. Recent studies of human orthotopic GBM in mice and in situ demonstrated GBM cells rely on both glycolysis and mitochondrial oxidation for glucose catabolism. These observations suggest that the homeostasis of energy metabolism of GBM cells might be further disturbed by dual-inhibition of glucose metabolism. The present study aimed to evaluate the efficacy and the mechanisms of dual-targeting therapy in GBM cells.MethodsRepresentative GBM cells (immortalized GBM cell lines and patient-derived GBM cells) and non-cancerous cells were treated with 4-(N-(S-penicillaminylacetyl)amino) phenylarsonous acid (PENAO), an in-house designed novel arsenic-based mitochondrial toxin, in combination with dichloroacetate (DCA), a pyruvate dehydrogenase kinase inhibitor. The efficacy of this combinatorial therapy was evaluated by MTS assay, clonogenic surviving assay and apoptotic assays. The underlying mechanisms of this dual-targeting treatment were unraveled by using mitochondrial membrane potential measurements, cytosol/mitochondrial ROS detection, western blotting, extracellular flux assay and mass spectrometry.ResultsAs monotherapies, both PENAO and DCA induced proliferation arrest in a panel of GBM cell lines and primary isolates. PENAO inhibited oxygen consumption, induced oxidative stress and depolarized mitochondrial membrane potential, which in turn activated mitochondria-mediated apoptosis. By combining DCA with PENAO, the two drugs worked synergistically to inhibit cell proliferation (but had no significant effect on non-cancerous cells), impair the clonogenicity, and induce mitochondria-mediated apoptosis. An oxidative stress of mitochondrial origin takes a prominent place in the mechanism by which the combination of PENAO and DCA induces cell death. Additionally, PENAO-induced oxidative damage was enhanced by DCA through glycolytic inhibition which in turn diminished acid production induced by PENAO. Moreover, DCA treatment also led to an alteration in the multidrug resistance (MDR) phenotype of GBM cells, thereby leading to an increased cytosolic accumulation of PENAO.ConclusionsThe findings of this study shed a new light with respect to the dual-targeting of glucose metabolism in GBM cells and the innovative combination of PENAO and DCA shows promise in expanding GBM therapies.

MTOR Complex 2 Controls Glycolytic Metabolism in Glioblastoma through FoxO Acetylation and Upregulation of c-Myc

Aerobic glycolysis (the Warburg effect) is a core hallmark of cancer, but the molecular mechanisms underlying it remain unclear. Here, we identify an unexpected central role for mTORC2 in cancer metabolic reprogramming where it controls glycolytic metabolism by ultimately regulating the cellular level of c-Myc. We show that mTORC2 promotes inactivating phosphorylation of class IIa histone deacetylases, which leads to the acetylation of FoxO1 and FoxO3, and this in turn releases c-Myc from a suppressive miR-34c-dependent network. These central features of activated mTORC2 signaling, acetylated FoxO, and c-Myc levels are highly intercorrelated in clinical samples and with shorter survival of GBM patients. These results identify a specific, Akt-independent role for mTORC2 in regulating glycolytic metabolism in cancer.

Glioblastoma, a Brief Review of History, Molecular Genetics, Animal Models and Novel Therapeutic Strategies

Glioblastoma (GBM) is the most common and lethal primary brain tumor. Over the past few years tremendous genomic and proteomic characterization along with robust animal models of GBM have provided invaluable data that show that "GBM", although histologically indistinguishable from one another, are comprised of molecularly heterogenous diseases. In addition, robust pre-clinical models and a better understanding of the core pathways disrupted in GBM are providing a renewed optimism for novel strategies targeting these devastating tumors. Here, we summarize a brief history of the disease, our current molecular knowledge, lessons from animal models and emerging concepts of angiogenesis, invasion, and metabolism in GBM that may lend themselves to therapeutic targeting.

Abstract LB-159: Using proton MRSI to predict response of Vorinostat treatment in recurrent GBM

Abstract A major impediment to the development of new therapies for glioblastoma is a lack of biomarkers indicating response. The current standard for assessing tumor progression relies on changes in size of the enhancing components of the tumor on standard MRI. While this was adequate when patients were treated with radiation alone, the addition of temozolomide has significantly increased the incidence of “pseudoprogression” while use of anti-angiogenic agents (e.g. cediranib) has increased the incidence of “pseudoresponse” complicating the interpretation of standard imaging. Tissue biopsy following treatment can assess tumor viability but this is invasive and impractical. Also, many newer agents do not produce a traditional tumor “response”. Epigenetic modifications are now recognized as a frequent development in the early phases of tumorigenesis, playing a central role in tumor development. Epigenetic alterations differ significantly from genetic modifications in that they may be readily revertible by ‘‘epigenetic drugs’’ such as inhibitors of histone deacetylases (HDAC). HDACs As a promising new modality for cancer therapy the first generation of HDAC inhibitors (HDACi) are currently being tested in phase I/II clinical trials. Glioblastomas benefit from therapy with HDACi, such as vorinostat, or SAHA, demonstrating tumor redifferentiation/cytostasis rather than tumor size reduction. This limits the utility of traditional imaging methods such as MRI. Magnetic resonance spectroscopic imaging (MRSI) quantitates amino acids and other metabolic substances in tumor and normal brain, allowing characterization of metabolic processes in live tissue. Our preclinical MRSI results show that after only three days of treatment with SAHA, elevated alanine and lactate levels and reduced myo-inositol (MI), N-acetyl aspartate (NAA), and creatine levels in gliomas return toward normal brain levels. In our patient study of SAHA and temozolomide in recurrent GBMs, MRSI showed normalization (or restoration) of glioblastoma metabolism toward normal brain tissue-like metabolism following only 7 days of SAHA treatment in 50% of enrolled patients (metabolic responders). In contrast, MRSI showed no changes at day 7 in the other 50% of enrolled GBM patients (non-metabolic responders, p < 0.001). These results provide an exciting insight of the mechanisms by which HDACi exert their effect on glioblastomas. The increased biosynthetic needs of tumor cells demand a reprogramming of cellular metabolism. This creates increased energy demands and makes tumor cells more vulnerable to interventions targeting their metabolism. The mechanism by which HDACi induces redifferentiation/cytostasis in tumors may be by targeting tumor metabolism. The changes, as measured by MRSI, may serve as novel early predictors of response to HDACi-containing combination therapy in glioblastomas. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-159. doi:1538-7445.AM2012-LB-159

Abstract 2304: 2-DG inhibits of N-glycosylation in glioblastoma-derived cancer stem cells

Abstract Cancer stem cells (CSCs) are capable of unlimited self-renewal and multi-lineage differentiation. We have shown that 2-deoxy-D-glucose (2-DG), a known inhibitor of glycolysis, that is also a 2-deoxy-D-mannose can inhibits the growth of glioma-derived stem cells (GSC11) under normoxic conditions, and we hypothesize that 2-DG can affect D-glucose and D-mannose metabolism in glioblastoma derived cancer stem. Our studies showed that 2-DG affects formation of N-glycans by replacing D-mannose in glycosylation processes. We have synthesized 2-DG, D-glucose, and D-mannose labeled with deuterium at C-2 and C-6 and treated GSC11 cells with these monosaccharides to measure their effects on global N-glycan formation. Our results demonstrated that deuterium labeled 2-DG was incorporated into the N-glycans leading to the termination of the extension of oligosaccharide chain. Comparative glycomic analysis of control, 2-DG-treated, and D-mannose-rescued GSC11cells revealed a distinct modulation of the N-glycan profile. The levels of all types of N-glycans were decreased (by ∼4-fold) in 2-DG-treated GSC11 cells compared with control cells. In contrast, N-glycan synthesis in GSC11 cells could be rescued to almost “normal control” levels by adding exogenous D-mannose. D-Mannose rescue of 2-DG-treated GSC11 cells drastically reduced the incorporation of 2-DG into the N-glycans. These results indicate that 2-DG can interfere with biochemical transformations of D-mannose and that such interference might contribute to the overall antitumor effects of 2-DG. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2304. doi:10.1158/1538-7445.AM2011-2304

High glycolysis in gliomas despite low hexokinase transcription and activity correlated to chromosome 10 loss.

Loss of chromosome 10 was observed in 10 out of 12 xenografted glioblastomas studied. Chromosome 10 carries the gene coding the hexokinase type 1 isoenzyme (HK-I), which catalyses the first step of glycolysis, which is essential in brain tissue and glioblastomas. We investigated the relationships between the relative chromosome 10 number, the amount of HK-I mRNA, HK-I activity and its intracellular distribution, and glycolysis-related parameters such as the lactate-pyruvate ratio, lactate dehydrogenase (LDH) and ATP contents. Individual tumour HK-I mRNA amounts were 23-65% lower than that of normal human brain and reflected the relative decrease of chromosome 10 number (alpha < 0.01). Total HK activities of individual glioblastomas varied considerably but were constantly (a mean of seven times) lower than that of normal brain tissue. The mitochondria-bound HK-I fraction of individual tumours was generally over 50%, compared with that of normal brain tissue. As shown by lactate - pyruvate ratios, in all the gliomas, glycolysis was elevated to an average of 3-fold that measured in normal brain. An elevated ATP content was also constantly noted. Adaptation of glioblastoma metabolism to the chromosome 10 loss and to the HK-I transcription unit emphasises the critical role of glycolysis in their survival. We hypothesise that HK-I, the enzyme responsible for initiating glycolysis necessary for brain function, may approach its lowest limit in gliomas, thereby opening therapeutic access to pharmacological anti-metabolites affecting energy metabolism and tumour growth.

Effect of norepinephrine on glucose metabolism in glioblastoma and neuroblastoma cells in cell culture.

The addition of norepinephrine to cultured glioblastoma cells results in an inhibition of uptake of radioactivity from D-[2-(3)H]glucose, D-[1-(14)C]glucose, D-[2-(14)C]glucose, and D-[6-(14)C]glucose. In addition, if the glioblastoma cells are previously labeled with these substrates, norepinephrine causes an increase in the release of radioactivity. These effects were not observed with cultured neuroblastoma cells. It is suggested that the breakdown of glycogen is activated by norepinephrine as a result of an increase in 3':5'-cyclic AMP.