Study Of Cancer Metabolism Research Articles

Cancer Metabolism Historical Perspectives: A Chronicle of Controversies and Consensus.

A century ago, Otto Warburg's work sparked the field of cancer metabolism, which has since taken a tortuous path. As evidence accumulated over the decades, consensus views of causes of cancer emerged, whereby genetic and epigenetic oncogenic drivers promoted immune evasion and induced new blood vessels and neoplastic metabolism to support tumor growth. Neoplastic cells abandon social cues of intercellular cooperation, escape tissue confinement, metastasize, and ultimately kill the host. Herein, key milestones in the study of cancer metabolism are chronicled with an emphasis on carbohydrate metabolism. The field began with a cancer cell-autonomous view that has been refined by a richer understanding of solid cancers as growing, immune-suppressive, complex organs comprising different cell types that are nourished by a variety of nutrients and variable amounts of oxygen through abnormal neovasculatures. Based on foundational historical studies, our current understanding of cancer metabolism offers a hopeful outlook for targeting metabolism to enhance cancer therapy.

P5C as an Interface of Proline Interconvertible Amino Acids and Its Role in Regulation of Cell Survival and Apoptosis.

Studies of cancer metabolism have focused on the production of energy and the interconversion of carbons between cell cycles. More recently, amino acid metabolism, especially non-essential amino acids (NEAAs), has been investigated, underlining their regulatory role. One of the important mediators in energy production and interconversion of carbons in the cell is Δ1-pyrroline-5-carboxylate (P5C)—the physiological intracellular intermediate of the interconversion of proline, ornithine, and glutamate. As a central component of these conversions, it links the tricarboxylic acid cycle (TCA), urea cycle (UC), and proline cycle (PC). P5C has a cyclic structure containing a tertiary nitrogen atom (N) and is in tautomeric equilibrium with the open-chain form of L-glutamate-γ-semialdehyde (GSAL). P5C is produced by P5C synthase (P5CS) from glutamate, and ornithine via ornithine δ-amino acid transferase (δOAT). It can also be converted to glutamate by P5C dehydrogenase (P5CDH). P5C is both a direct precursor of proline and a product of its degradation. The conversion of P5C to proline is catalyzed by P5C reductase (PYCR), while proline to P5C by proline dehydrogenase/oxidase (PRODH/POX). P5C-proline-P5C interconversion forms a functional redox couple. Their transformations are accompanied by the transfer of a reducing-oxidizing potential, that affect the NADP+/NADPH ratio and a wide variety of processes, e.g., the synthesis of phosphoribosyl pyrophosphate (PRPP), and purine ribonucleotides, which are crucial for DNA synthesis. This review focuses on the metabolism of P5C in the cell as an interconversion mediator of proline, glutamate, and ornithine and its role in the regulation of survival and death with particular emphasis on the metabolic context.

From Metabolism to Genetics and Vice Versa: The Rising Role of Oncometabolites in Cancer Development and Therapy.

Over the last decades, the study of cancer metabolism has returned to the forefront of cancer research and challenged the role of genetics in the understanding of cancer development. One of the major impulses of this new trend came from the discovery of oncometabolites, metabolic intermediates whose abnormal cellular accumulation triggers oncogenic signalling and tumorigenesis. These findings have led to reconsideration and support for the long-forgotten hypothesis of Warburg of altered metabolism as oncogenic driver of cancer and started a novel paradigm whereby mitochondrial metabolites play a pivotal role in malignant transformation. In this review, we describe the evolution of the cancer metabolism research from a historical perspective up to the oncometabolites discovery that spawned the new vision of cancer as a metabolic disease. The oncometabolites’ mechanisms of cellular transformation and their contribution to the development of new targeted cancer therapies together with their drawbacks are further reviewed and discussed.

Bridging the Metabolic Parallels Between Neurological Diseases and Cancer.

Despite the many recent breakthroughs in cancer research, oncology has traditionally been seen as a distinct field from other diseases. Recently, more attention has been paid to repurposing established therapeutic strategies and targets of other diseases towards cancer treatment, with some of these attempts generating promising outcomes [1, 2]. Recent studies using advanced metabolomics technologies [3] have shown evidence of close metabolic similarities between cancer and neurological diseases. These studies have unveiled several metabolic characteristics shared by these two categories of diseases, including metabolism of glutamine, gamma-aminobutyric acid (GABA), and N-acetyl-aspartyl-glutamate (NAAG) [4-6]. The striking metabolic overlap between cancer and neurological diseases sheds light on novel therapeutic strategies for cancer treatment. For example, 2-(phosphonomethyl) pentanedioic acid (2-PMPA), one of the glutamate carboxypeptidase II (GCP II) inhibitors that prevent the conversion of NAAG to glutamate, has been shown to suppress cancer growth [6, 7]. These promising results have led to an increased interest in integrating this metabolic overlap between cancer and neurological diseases into the study of cancer metabolism. The advantages of studying this metabolic overlap include not only drug repurposing but also translating existing knowledge from neurological diseases to the field of cancer research. This chapter discusses the specific overlapping metabolic features between cancer and neurological diseases, focusing on glutamine, GABA, and NAAG metabolisms. Understanding the interconnections between cancer and neurological diseases will guide researchers and clinicians to find more effective cancer treatments.

Abstract IA24: Imaging cancer metabolism in patients: Beyond FDG PET

Abstract Molecular imaging is a tool that can visualize and quantify biological processes at the molecular and cellular levels in living systems1, and it is therefore ideally suited to the study of cancer metabolism in patients2. In the clinic, molecular imaging of cancer metabolism has been most widely exploited using the elevated rate of glycolysis observed in most tumors as a target for cancer detection and staging using positron emission tomography (PET) and the glucose analog 18F-fluordeoxyglucose (FDG)3. FDG PET, now combined with anatomic imaging in the form of PET/CT, has become an important tool for cancer detection, staging, and response assessment, widely used in oncologic clinical practices around the world. Clinical use of FDG PET has increased our appreciation of aberrant glycolysis as a feature of more aggressive, less differentiated tumors4. At the same time, the variability of tumor FDG uptake seen in clinical imaging has highlighted some of the limitations of imaging tumor glycolysis and has spurred the development of new imaging probes and novel imaging modalities designed to image other facets of cancer energy metabolism. In addition, the use of therapeutics that are targeted to and/or influenced by cancer metabolic phenotype5 drive applications of cancer metabolic imaging to clinical challenges beyond detection that include predicting and monitoring response to targeted therapy6. This talk will briefly review the underpinnings of the current use of FDG PET/CT for cancer staging and response evaluation. The talk will beyond FDG PET and discuss alternative PET probes targeted to other metabolic substrates such as amino acids, lipids, and TCA intermediates7, as well as new instrumentation that offers unique capabilities for imaging whole-body cancer metabolism imaging8. The talk will also highlight other methods for imaging cancer metabolism in patients, especially hyperpolarized 13C-labeled metabolic substrates such as pyruvate9. Unique features and advantages of each modality will be highlighted, as will approaches to image analysis common across modalities, including quantitative imaging and kinetic analysis. Finally, the talk will emphasize benefit of multi-modality imaging as an approach to fully characterize cancer metabolism, using glutaminolysis imaging as an example of active investigation. Supported in part by Komen SAC130060, NIH P30-CA016520, and NIH R01-CA211337.

Metabolomic studies of amino acid analysis in Saccharomyces cells exposed to selenium and gamma irradiation

Metabolomic studies are essential to identify and quantify key metabolites in biological systems. Analysis of amino acids (AA) is very important in target metabolomics studies. Chromatographic methods are used to support metabolite determinations. Therefore, this work presents analysis of 17 AA in Saccharomyces cerevisiae cells (a useful model in the study of cancer metabolism) exposed to sodium selenite and gamma radiation. An improved GC/MS method using propyl chloroformate/propanol as derivatizing reagent was applied to AA determinations. The method exhibited good linearity in the range of 0.08–600.00 mg L−1; limits of determination from 0.04 to 1.60 mg L−1; limits of quantification from 0.08 to 2.76 mg L−1; repeatability ranging from 1.9 to 11.4 %; and precision ranging from 2.8 to 13.8 %. The correlations between selenite/gamma radiation with AA profile was investigated to establish candidates for cancer biomarkers. The analyses of yeast cultures found high concentrations of amino acids, such as Alanine, Serine, Glutamate, and Lysine, which might be associated with the development of metabolic adaptations of cancer based on its high demand for biomass and energy, found both in this model and neoplastic cells.

Active pyruvate dehydrogenase and impaired gluconeogenesis in orthotopic hepatomas of rats

BackgroundTherapies targeting altered activity of pyruvate dehydrogenase (PDH) and pyruvate carboxylase (PC) have been proposed for hepatomas. However, the activities of these pathways in hepatomas in vivo have not been distinguished. Here we examined pyruvate entry into the tricarboxylic acid (TCA) cycle through PDH versus PC in vivo using hepatoma-bearing rats. MethodsHepatoma-bearing rats were generated by intrahepatic injection of H4IIE cells. Metabolism of 13C-labeled glycerol, a physiological substrate for both gluconeogenesis and energy production, was measured with 13C NMR analysis. The concentration of key metabolites and the expression of relevant enzymes were measured in hepatoma, surrounding liver, and normal liver. ResultsIn orthotopic hepatomas, pyruvate entry into the TCA cycle occurred exclusively through PDH and the excess PDH activity compared to normal liver was attributed to downregulated pyruvate dehydrogenase kinase (PDK) 2/4. However, pyruvate carboxylation via PC and gluconeogenesis were minimal, which was linked to downregulated forkhead box O1 (FoxO1) by Akt activity. In contrast to many studies of cancer metabolism, lactate production in hepatomas was not increased which corresponded to reduced expression of lactate dehydrogenase. The production of serine and glycine in hepatomas was enhanced, but glycine decarboxylase was downregulated. ConclusionsThe combination of [U-13C3]glycerol and NMR analysis enabled investigation of multiple biochemical processes in hepatomas and surrounding liver. We demonstrated active PDH and other related metabolic alterations in orthotopic hepatomas that differed substantially not only from the host organ but also from many earlier studies with cancer cells.

Oncometabolites in renal cancer.

The study of cancer metabolism has evolved vastly beyond the remit of tumour proliferation and survival with the identification of the role of 'oncometabolites' in tumorigenesis. Simply defined, oncometabolites are conventional metabolites that, when aberrantly accumulated, have pro-oncogenic functions. Their discovery has led researchers to revisit the Warburg hypothesis, first postulated in the 1950s, of aberrant metabolism as an aetiological determinant of cancer. As such, the identification of oncometabolites and their utilization in diagnostics and prognostics, as novel therapeutic targets and as biomarkers of disease, are areas of considerable interest in oncology. To date, fumarate, succinate, L-2-hydroxyglutarate (L-2-HG) and D-2-hydroxyglutarate (D-2-HG) have been characterized as bona fide oncometabolites. Extensive metabolic reprogramming occurs during tumour initiation and progression in renal cell carcinoma (RCC) and three oncometabolites - fumarate, succinate and L-2-HG - have been implicated in this disease process. All of these oncometabolites inhibit a superfamily of enzymes known as α-ketoglutarate-dependent dioxygenases, leading to epigenetic dysregulation and induction of pseudohypoxic phenotypes, and also have specific pro-oncogenic capabilities. Oncometabolites could potentially be exploited for the development of novel targeted therapies and as biomarkers of disease.

Epigenetic Factors and Mitochondrial Biology in Yeast: A New Paradigm for the Study of Cancer Metabolism?

Bidirectional cross-talk between nuclear and mitochondrial DNA is fundamental for cell homeostasis. Epigenetic mechanisms regulate the inter-organelle communication between nucleus and mitochondria. Recent research highlights not only the retrograde activation of nuclear gene transcription in case of mitochondria dysfunction, but also the role of post-translational modifications of mitochondrial proteins in respiratory metabolism. Here we discuss some aspects and novel findings in Saccharomyces cerevisiae. In yeast, KAT-Gcn5 and DUB-Ubp8 have a role in respiration and are localized, as single proteins, into mitochondria. These findings, beside the canonical and widely known nuclear activity of SAGA complex in chromatin regulation, provide novel clues on promising aspects linking evolutionary conserved epigenetic factors to the re-programmed metabolism of cancer cells.

Application of in vivo MR methods in the study of breast cancer metabolism.

In the last two decades, various in vivo MR methodologies have been evaluated for their potential in the study of cancer metabolism. During malignant transformation, metabolic alterations occur, leading to morphological and functional changes. Among various MR methods, in vivo MRS has been extensively used in breast cancer to study the metabolism of cells, tissues or whole organs. It provides biochemical information at the metabolite level. Altered choline, phospholipid and energy metabolism has been documented using proton (1 H), phosphorus (31 P) and carbon (13 C) isotopes. Increased levels of choline-containing compounds, phosphomonoesters and phosphodiesters in breast cancer, which are indicative of altered choline and phospholipid metabolism, have been reported using in vivo, in vitro and ex vivo NMR studies. These changes are reversed on successful therapy, which depends on the treatment regimen given. Monitoring the various tumor intermediary metabolic pathways using nuclear spin hyperpolarization of 13 C-labeled substrates by dynamic nuclear polarization has also been recently reported. Furthermore, the utility of various methods such as diffusion, dynamic contrast and perfusion MRI have also been evaluated to study breast tumor metabolism. Parameters such as tumor volume, apparent diffusion coefficient, volume transfer coefficient and extracellular volume ratio are estimated. These parameters provide information on the changes in tumor microstructure, microenvironment, abnormal vasculature, permeability and grade of the tumor. Such changes seen during cancer progression are due to alterations in the tumor metabolism, leading to changes in cell architecture. Due to architectural changes, the tissue mechanical properties are altered; this can be studied using magnetic resonance elastography, which measures the elastic properties of tissues. Moreover, these structural MRI methods can be used to investigate the effect of therapy-induced changes in tumor characteristics. This review discusses the potential of various in vivo MR methodologies in the study of breast cancer metabolism.

Breast Tissue Metabolism by Magnetic Resonance Spectroscopy.

Metabolic alterations are known to occur with oncogenesis and tumor progression. During malignant transformation, the metabolism of cells and tissues is altered. Cancer metabolism can be studied using advanced technologies that detect both metabolites and metabolic activities. Identification, characterization, and quantification of metabolites (metabolomics) are important for metabolic analysis and are usually done by nuclear magnetic resonance (NMR) or by mass spectrometry. In contrast to the magnetic resonance imaging that is used to monitor the tumor morphology during progression of the disease and during therapy, in vivo NMR spectroscopy is used to study and monitor tumor metabolism of cells/tissues by detection of various biochemicals or metabolites involved in various metabolic pathways. Several in vivo, in vitro and ex vivo NMR studies using 1H and 31P magnetic resonance spectroscopy (MRS) nuclei have documented increased levels of total choline containing compounds, phosphomonoesters and phosphodiesters in human breast cancer tissues, which is indicative of altered choline and phospholipid metabolism. These levels get reversed with successful treatment. Another method that increases the sensitivity of substrate detection by using nuclear spin hyperpolarization of 13C-lableled substrates by dynamic nuclear polarization has revived a great interest in the study of cancer metabolism. This review discusses breast tissue metabolism studied by various NMR/MRS methods.

The current state of cancer metabolism

This Foreword introduces the nine Review articles in our Focus on Tumour Metabolism and discusses the main areas of tumour metabolism for further research. The study of cancer metabolism has grown exponentially over the past decade. Although the initial observations by Otto Warburg and his contemporaries during the early twentieth century strongly suggested that core cellular metabolism was altered during the process of malignant transformation, the oncogene revolution and the rise of genetic technology in the latter half of the century shifted the focus of research in cancer biology towards the specific mutations and alterations in signalling pathways responsible for tumorigenesis. However, discoveries during the past two decades, and the successful clinical implementation of imaging approaches based on the metabolic phenotype of some tumours have once again highlighted that changes to metabolic processes are required for cells to escape from their defined roles as integrated parts of a tissue and organ system, and become an independent clone of cells that manifests itself as malignant disease.

Metabolic requirements for cancer cell proliferation

BackgroundThe study of cancer metabolism has been largely dedicated to exploring the hypothesis that oncogenic transformation rewires cellular metabolism to sustain elevated rates of growth and division. Intense examination of tumors and cancer cell lines has confirmed that many cancer-associated metabolic phenotypes allow robust growth and survival; however, little attention has been given to explicitly identifying the biochemical requirements for cell proliferation in a rigorous manner in the context of cancer metabolism.ResultsUsing a well-studied hybridoma line as a model, we comprehensively and quantitatively enumerate the metabolic requirements for generating new biomass in mammalian cells; this indicated a large biosynthetic requirement for ATP, NADPH, NAD+, acetyl-CoA, and amino acids. Extension of this approach to serine/glycine and glutamine metabolic pathways suggested lower limits on serine and glycine catabolism to supply one-carbon unit synthesis and significant availability of glutamine-derived carbon for biosynthesis resulting from nitrogen demands alone, respectively. We integrated our biomass composition results into a flux balance analysis model, placing upper bounds on mitochondrial NADH oxidation to simulate metformin treatment; these simulations reproduced several empirically observed metabolic phenotypes, including increased reductive isocitrate dehydrogenase flux.ConclusionsOur analysis clarifies the differential needs for central carbon metabolism precursors, glutamine-derived nitrogen, and cofactors such as ATP, NADPH, and NAD+, while also providing justification for various extracellular nutrient uptake behaviors observed in tumors. Collectively, these results demonstrate how stoichiometric considerations alone can successfully predict empirically observed phenotypes and provide insight into biochemical dynamics that underlie responses to metabolic perturbations.Electronic supplementary materialThe online version of this article (doi:10.1186/s40170-016-0156-6) contains supplementary material, which is available to authorized users.

Changing perspective on oncometabolites: from metabolic signature of cancer to tumorigenic and immunosuppressive agents.

During tumorigenesis, the shift from oxidative phosphorylation to glycolysis in ATP production accounts for the dramatic change in the cellular metabolism and represents one of the major steps leading to tumour formation. The so-called Warburg effect is currently considered something more than a mere modification in the cellular metabolism. The paradox that during cancer cell proliferation the increase in energy need is supplied by glycolysis can be only explained by taking into account the many roles that intermediates of glycolysis or TCA cycle play in cellular physiology, besides energy production. Recent studies have shown that metabolic intermediates induce changes in chromatin structure or drive neo-angiogenesis. In this review, we present some of the latest findings in the study of cancer metabolism with particular attention to how tumour metabolism and its microenvironment can favour tumour growth and aggressiveness, by hijacking and dampening the anti-tumoral immune response.

Abstract B10: Noninvasive pharmacodynamic markers of the dual mTORC1/2 inhibitor AZD2014 in combination with paclitaxel, in cisplatin-resistant ovarian carcinoma xenografts

Abstract Background: The PI3K/AKT/mTOR pathway is known to regulate glucose metabolism, proliferation and apoptosis, hence the inhibition of mTOR is expected have impact on these important mechanisms of tumor growth and survival. Studies of cancer metabolism following mTOR inhibition reported to date have only been carried out on allosteric mTOR inhibitors which selectively inhibit the activity of mTORC1. The metabolic changes associated with dual mTORC1 and 2 inhibitions remain unknown. AZD2014 is a dual mTORC1/2 inhibitor. The aims of this study are to (i) examine the effects on tumor metabolism following mTORC1/2 inhibition alone and in combination with paclitaxel, (ii) to develop a non-invasive pharmacodynamic (PD) biomarker for tumor response. Methods: We investigated the effects of AZD2014 alone (A: 50mg/kg/3 days/week po), paclitaxel alone (P: 20mg/kg/1 day/week ip) and the combination of AZD2014 and paclitaxel (A+P: same doses) on tumor growth, signal transduction (pSer473-AKT, pSer240/244-S6) and apoptosis (cleaved PARP) in a cisplatin resistant ovarian (A2780CisR) carcinoma xenograft model following 2 weeks of treatment. Metabolic profiles of A2780CisR tumor extracts after 2 weeks of treatment were also measured by high resolution in vitro 1H- and 31P-MRS. In order to develop early non-invasive PD markers of tumor response, in vivo 1H-MRS before and after 3 days of treatment were also performed. Results: Growth and molecular response- Following two weeks of treatment, tumor volumes of the A2780CisR xenografts increased by 280±100% in A+P (p<0.05; compared to vehicle-controls (V)), 420±160% in A (not significant compared to V (ns)), 730±180% in P (ns) and 560±20% in V. Reduced pSer473-AKT and pSer240/244-S6 protein levels and increased cleaved-PARP expression were observed in A- and A+P-treated xenografts consistent with mTORC1/2 inhibition and induction of apoptosis, respectively. In vitro 1H- and 31P-MRS of tumor extracts- Similar significant increases in branched-chain amino acids (p<0.03), glutamine (p<0.002), tyrosine (p<0.0001), phenylalanine (p<0.02) and glucose (p<0.03) were found in A- and A+P-treated tumors when compared with V. Significant decreases in phosphocholine (PC, p<0.002), glycero-phosphocholine (GPC, p<0.002), phosphoethanolamine (PE, p<0.02) and ATP (p<0.003), together with reduced expression of choline kinase, were only seen in A+P-treated tumors. An increase in threonine (p<0.03) was only observed in P- and A+P-treated tumors compared with V. In vivo 1H-MRS- The reduction in phospholipid metabolites (PC, GPC and PE) following A+P treatment was confirmed in vivo with a significant decrease in the ratio of total choline/water signal (p=0.04) observed at the early time-point of 3 days of treatment. Conclusions: A+P is effective in preclinical ovarian tumors, with additive growth inhibition and increased apoptosis. Very few metabolic changes were observed in P-treated tumors compared with V. The non-phospholipid changes in the metabolic profiles of A- and A+P-treated tumors are consistent with previous findings where similar metabolic profiles were found following mTOR inhibition (1). A+P treatment also caused decreases in PC (associated with reduced choline kinase expression) and other choline-related metabolites and these phospholipid changes may have potential as surrogate non-invasive markers for determining tumor response following AZD2014 and paclitaxel combination treatment. (1) Lin et al. Cell Symposia: Angiogenesis, Metabolic Regulation, and Cancer Biology in association with VIB, Belgium 2012. This work is supported by the CR-UK and EPSRC Cancer Imaging Centre in association with the MRC and Department of Health (England) grants C1060/A10334 and C1060/A16464, NHS funding to the NIHR Biomedical Research Centre. MOL is an NIHR Senior Investigator. Citation Format: Anne-Christine LF Wong Te-Fong, Efthymia Papaevangelou, Martin O. Leach, Udai Banerji, Yuen-Li Chung. Noninvasive pharmacodynamic markers of the dual mTORC1/2 inhibitor AZD2014 in combination with paclitaxel, in cisplatin-resistant ovarian carcinoma xenografts. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr B10.

Lipid Synthesis Is a Metabolic Liability of Non-Small Cell Lung Cancer.

The renaissance in the study of cancer metabolism has refocused efforts to identify and target metabolic dependencies of tumors as an approach for cancer therapy. One of the unique metabolic requirements that cancer cells possess to sustain their biosynthetic growth demands is altered fatty acid metabolism, in particular the synthesis of de novo fatty acids that are required as cellular building blocks to support cell division. Enhanced fatty acid synthesis that is observed in many tumor types has been postulated to open a therapeutic window for cancer therapy and, correspondingly, efforts to pharmacologically inhibit key enzymes of fatty acid synthesis are being pursued. However, despite these efforts, whether inhibition of fatty acid synthesis stunts tumor growth in vivo has been poorly understood. In this review, we focus on the recent evidence that pharmacologic inhibition of acetyl-CoA carboxylase, the enzyme that regulates the rate-limiting step of de novo fatty acid synthesis, exposes a metabolic liability of non-small cell lung cancer and represses tumor growth in preclinical models.

Identification of CKMT1B As a New Target in EVI1-Positive AML

Recent investigations into the relationship between cancer and cellular metabolism have revealed the strong dependency of different cancers on a diverse array of metabolic pathways. For instance, a variety of cancers depend on the PI3K/AKT pathway for a wide range of glucose-related mechanisms, including AKT-mediated membrane translocation of glucose transporters, activation of the glycolytic enzymes hexokinase and phosphofructokinase, and up-regulation of de novo fatty acid synthesis. A major area of therapeutic and biological interest in the study of cancer metabolism is the process by which these metabolic pathways become deregulated in the first place en route to, or as a result of, the development of cancer. The deregulation of metabolic pathways can occur through alterations in the cellular landscape brought about by mutations in metabolic enzymes (e.g., IDH1/IDH2 and SDH), aberrant expression of transcription factors, such as the proto-oncogene MYC, or the loss of tumor suppressors, such as p53.Through gene expression and metabolic profiling analyses, we found that the transcription factor EVI-1, whose overexpression in acute and chronic myeloid leukemia (AML and CML) is correlated with poor patient outcome, induced key metabolic perturbations in hematopoietic progenitor cells. These result in a decrease of the mitochondrial oxygen consumption rate, a blockade of the de novo purine and pyrimidine synthesis, and an increase in glycolysis. Using a library of pooled shRNAs targeting genes involved in each of these pathways, we then established a direct link between EVI-1 expression and the development of a heretofore undescribed cellular dependency on the overexpression of the ATP-buffering mitochondrial creatine kinase protein CKMT1B. We showed that EVI-1 directly promotes CKMT1B expression through repression of the master regulator of myeloid differentiation RUNX1. Alteration of the CKMT1B-dependent pathway, either with shRNA or with the small molecule cyclocreatine, impairs production of intracellular phospho-creatine, which in turn alters cell viability specifically in EVI-1-positive (n = 8) versus EVI-1-negative AML cell lines (n = 8), and in EVI-1-positive (n = 5) versus EVI-1-negative (n = 17) primary AML blasts. This decrease in cell viability is associated with the activation of an erythroid differentiation program concomitant with a downregulation of the immature lineage marker c-KIT, both induced by GSK3A/B inhibition. Overexpression of a constitutively activated form of GSK3B (S9A) or GSK3A (S21A) impairs the cell differentiation induced by CKMT1B inhibition. Finally, suppression of CKMT1B alleviates leukemic burden in vivo in two AML mouse models: i) an orthotopic model of transplanted human EVI1-positive AML cells and ii) a syngeneic model of transplanted murine NrasG12D + Evi1 AML cells.This new interplay between EVI-1 and the creatine pathway uncovers CKMT1B as a new target of interest in EVI-1-positive AML, a high-risk subtype of AML for which current treatment regimens remain inadequate. DisclosuresDeAngelo:Novartis: Consultancy; Ariad: Consultancy; Bristol Myers Squibb: Consultancy; Pfizer: Consultancy; Amgen: Consultancy; Incyte: Consultancy; Agios: Consultancy; Celgene: Consultancy. Stone:Celgene: Consultancy; Agios: Consultancy; Karyopharm: Consultancy; Sunesis: Consultancy, Other: DSMB for clinical trial; Novartis: Research Funding; Celator: Consultancy; Merck: Consultancy; Roche/Genetech: Consultancy; Abbvie: Consultancy; Amgen: Consultancy; Pfizer: Consultancy; AROG: Consultancy; Juno: Consultancy. Stegmaier:Novartis Pharmaceuticals: Consultancy.

Hyperpolarized C-13 studies of cancer metabolism in animal models. Hype or real?

The Warburg effect [1–3] is the tendency of many cancer types to metabolize glucose into lactate via glycolysis rather than oxidation in the TCA cycle. While fermentative glycolysis is highly inefficient in terms of ATP production (indeed, it yields only about 1/9 of the ATP that would be produced by the TCA cycle), it may confer a survival advantage on cancer cells, for instance by providing a source of carbon to support rapid proliferation [4]. The Warburg effect, and cancer metabolism more generally, may provide opportunities for novel therapeutic strategies that target specific metabolic pathways that cancer cells rely upon for survival and proliferation. Recently, there have been reports that indicate that cancer cells can survive on glutamine as a carbon source, even when glucose is removed from their growth medium [5,6]. Imaging tools for the study of metabolism include PET and MR spectroscopic imaging. Metabolic studies with PET make use of metabolites that have been isotopically labeled with e emitters such as C or N, or, alternatively, where one or more protons have been substituted with F. Over the past several decades F-18 PET using fluoro-deoxyglucose as the radiotracer has been widely adopted in oncological imaging. There have other radiotracers that have shown promise for imaging different metabolic alterations in tumors [7]. The advantages of PET include its high sensitivity (some metabolites can be detected at picomolar concentrations) and the relatively long half-lives of the radiotracers (10 minutes for N, 20 minutes for C, and 110 minutes for F). The disadvantages of PET include limitations on spatial resolution imposed by positron ranging (the highest achievable resolution is on the order of a few millimeters) and the inability of PET to distinguish between signal arising from the injected radiotracer and its metabolites. For the shorter-lived isotopes like C-11, there is the need for both a cyclotron and chemistry facilities for rapid synthesis of desired radiolabeled compounds.

Flicking the Warburg Switch—Tyrosine Phosphorylation of Pyruvate Dehydrogenase Kinase Regulates Mitochondrial Activity in Cancer Cells

In this issue of Molecular Cell, Hitosugi et al. (2011) show that the switch from oxidative phosphorylation to glycolysis in cancer cells is regulated by tyrosine phosphorylation of PDHK1.