70 genes selected for validation.

Here, we explore the manipulation of immune cell metabolism as a strategy in target discovery and drug development for immune-mediated diseases. Comparing exploitation of metabolic pathways to kill tumor cells for cancer treatment with the reprogramming of immune cells to treat autoimmune diseases highlights differences that confer several advantages to the latter (including a more favorable therapeutic index and greater target stability). We discuss technological capabilities and gaps, including the challenge of relating in vitro observations to in vivo biology. Finally, we conclude by identifying future opportunities that will move the field forward and accelerate drug discovery.

Metabolism has been shown to integrate with epigenetics and transcription to modulate cell fate and function. Beyond meeting the bioenergetic and biosynthetic demands of T-cell differentiation, whether metabolism might control T-cell fate by an epigenetic mechanism is unclear. Here, through the discovery and mechanistic characterization of a small molecule, (aminooxy)acetic acid, that reprograms the differentiation of T helper 17 (TH17) cells towards induced regulatory T (iTreg) cells, we show that increased transamination, mainly catalysed by GOT1, leads to increased levels of 2-hydroxyglutarate in differentiating TH17 cells. The accumulation of 2-hydroxyglutarate resulted in hypermethylation of the Foxp3 gene locus and inhibited Foxp3 transcription, which is essential for fate determination towards TH17 cells. Inhibition of the conversion of glutamate to α-ketoglutaric acid prevented the production of 2-hydroxyglutarate, reduced methylation of the Foxp3 gene locus, and increased Foxp3 expression. This consequently blocked the differentiation of TH17 cells by antagonizing the function of transcription factor RORγt and promoted polarization into iTreg cells. Selective inhibition of GOT1 with (aminooxy)acetic acid ameliorated experimental autoimmune encephalomyelitis in a therapeutic mouse model by regulating the balance between TH17 and iTreg cells. Targeting a glutamate-dependent metabolic pathway thus represents a new strategy for developing therapeutic agents against TH17-mediated autoimmune diseases.

Novel techniques for high-throughput steady-state metabolomic profiling yield information about changes of nearly thousands of metabolites. Such metabolomic profiles, when analyzed together with transcriptional profiles, can reveal novel insights about underlying biological processes. While a number of conceptual approaches have been developed for data integration, easily accessible tools for integrated analysis of mammalian steady-state metabolomic and transcriptional data are lacking. Here we present GAM ('genes and metabolites'): a web-service for integrated network analysis of transcriptional and steady-state metabolomic data focused on identification of the most changing metabolic subnetworks between two conditions of interest. In the web-service, we have pre-assembled metabolic networks for humans, mice, Arabidopsis and yeast and adapted exact solvers for an optimal subgraph search to work in the context of these metabolic networks. The output is the most regulated metabolic subnetwork of size controlled by false discovery rate parameters. The subnetworks are then visualized online and also can be downloaded in Cytoscape format for subsequent processing. The web-service is available at: https://artyomovlab.wustl.edu/shiny/gam/.

Genome scale data on biological systems has increasingly become available by sequencing of DNA and RNA, and by mass spectrometric quantification of proteins and metabolites. The cellular components from which these -omics regimes are derived act as one integrated system in vivo; thus, there is a natural instinct to integrate -omics data types. Statistical analyses, the use of previous knowledge in the form of networks, and the use of time-resolved measurements are three key design elements for life scientists to consider in planning integrated -omics studies. These design elements are reviewed in the context of multiple recent systems biology studies that leverage data from different types of -omics analyses. While most of these studies rely on well-established model organisms, the concepts for integrating -omics data that were developed in these studies can help to enable systems research in the field of cancer biology.

Macrophage polarization involves a coordinated metabolic and transcriptional rewiring that is only partially understood. By using an integrated high-throughput transcriptional-metabolic profiling and analysis pipeline, we characterized systemic changes during murine macrophage M1 and M2 polarization. M2 polarization was found to activate glutamine catabolism and UDP-GlcNAc-associated modules. Correspondingly, glutamine deprivation or inhibition of N-glycosylation decreased M2 polarization and production of chemokine CCL22. In M1 macrophages, we identified a metabolic break at Idh, the enzyme that converts isocitrate to alpha-ketoglutarate, providing mechanistic explanation for TCA cycle fragmentation. 13C-tracer studies suggested the presence of an active variant of the aspartate-arginosuccinate shunt that compensated for this break. Consistently, inhibition of aspartate-aminotransferase, a key enzyme of the shunt, inhibited nitric oxide and interleukin-6 production in M1 macrophages, while promoting mitochondrial respiration. This systems approach provides a highly integrated picture of the physiological modules supporting macrophage polarization, identifying potential pharmacologic control points for both macrophage phenotypes.

Abstract The LKB1/STK11 tumor suppressor encodes a serine/threonine kinase, which coordinates cell growth, polarity, motility, and metabolism. In non–small cell lung carcinoma, LKB1 is somatically inactivated in 25% to 30% of cases, often concurrently with activating KRAS mutations. Here, we used an integrative approach to define novel therapeutic targets in KRAS-driven LKB1-mutant lung cancers. High-throughput RNA interference screens in lung cancer cell lines from genetically engineered mouse models driven by activated KRAS with or without coincident Lkb1 deletion led to the identification of Dtymk, encoding deoxythymidylate kinase (DTYMK), which catalyzes dTTP biosynthesis, as synthetically lethal with Lkb1 deficiency in mouse and human lung cancer lines. Global metabolite profiling showed that Lkb1-null cells had a striking decrease in multiple nucleotide metabolites as compared with the Lkb1–wild-type cells. Thus, LKB1-mutant lung cancers have deficits in nucleotide metabolism that confer hypersensitivity to DTYMK inhibition, suggesting that DTYMK is a potential therapeutic target in this aggressive subset of tumors. Significance: Using cell lines derived from the lung cancers occurring in genetically engineered mice, we conducted an integrative genome-wide short hairpin RNA and metabolite screen to identify DTYMK as a potential therapeutic target in Kras/Lkb1–mutant lung cancer. We believe that DTYMK is tractable for the development of novel therapeutics, and show an integrative approach to target identification that reduces false-positive candidates and should have broad applicability for the development of targeted therapeutics. Cancer Discov; 3(8); 870–9. ©2013 AACR. See related commentary by Marcus and Khuri, p. 843 This article is highlighted in the In This Issue feature, p. 826

Proliferating tumor cells use aerobic glycolysis to support their high metabolic demands. Paradoxically, increased glycolysis is often accompanied by expression of the lower activity PKM2 isoform, effectively constraining lower glycolysis. Here, we report the discovery of PKM2 activators with a unique allosteric binding mode. Characterization of how these compounds impact cancer cells revealed an unanticipated link between glucose and amino acid metabolism. PKM2 activation resulted in a metabolic rewiring of cancer cells manifested by a profound dependency on the nonessential amino acid serine for continued cell proliferation. Induction of serine auxotrophy by PKM2 activation was accompanied by reduced carbon flow into the serine biosynthetic pathway and increased expression of high affinity serine transporters. These data support the hypothesis that PKM2 expression confers metabolic flexibility to cancer cells that allows adaptation to nutrient stress.

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Cancer cells must satisfy the metabolic demands of rapid cell growth within a continually changing microenvironment. We demonstrated that the dynamic posttranslational modification of proteins by O-linked β-N-acetylglucosamine (O-GlcNAcylation) is a key metabolic regulator of glucose metabolism. O-GlcNAcylation was induced at serine 529 of phosphofructokinase 1 (PFK1) in response to hypoxia. Glycosylation inhibited PFK1 activity and redirected glucose flux through the pentose phosphate pathway, thereby conferring a selective growth advantage on cancer cells. Blocking glycosylation of PFK1 at serine 529 reduced cancer cell proliferation in vitro and impaired tumor formation in vivo. These studies reveal a previously uncharacterized mechanism for the regulation of metabolic pathways in cancer and a possible target for therapeutic intervention.

Mutations of the isocitrate dehydrogenase 1 and 2 genes (IDH1 and IDH2) are commonly found in primary brain cancers. We previously reported that a novel enzymatic activity of these mutations results in the production of the putative oncometabolite, R(−)-2-hydroxyglutarate (2-HG). Here we investigated the ability of magnetic resonance spectroscopy (MRS) to detect 2-HG production in order to non-invasively identify patients with IDH1 mutant brain tumors. Patients with intrinsic glial brain tumors (n = 27) underwent structural and spectroscopic magnetic resonance imaging prior to surgery. 2-HG levels from MRS data were quantified using LC-Model software, based upon a simulated spectrum obtained from a GAMMA library added to the existing prior knowledge database. The resected tumors were then analyzed for IDH1 mutational status by genomic DNA sequencing, Ki-67 proliferation index by immunohistochemistry, and concentrations of 2-HG and other metabolites by liquid chromatography–mass spectrometry (LC–MS). MRS detected elevated 2-HG levels in gliomas with IDH1 mutations compared to those with wild-type IDH1 (P = 0.003). The 2-HG levels measured in vivo with MRS were significantly correlated with those measured ex vivo from the corresponding tumor samples using LC–MS (r 2 = 0.56; P = 0.0001). Compared with wild-type tumors, those with IDH1 mutations had elevated choline (P = 0.01) and decreased glutathione (P = 0.03) on MRS. Among the IDH1 mutated gliomas, quantitative 2-HG values were correlated with the Ki-67 proliferation index of the tumors (r 2 = 0.59; P = 0.026). In conclusion, water-suppressed proton (1H) MRS provides a non-invasive measure of 2-HG in gliomas, and may serve as a potential biomarker for patients with IDH1 mutant brain tumors. In addition to 2-HG, alterations in several other metabolites measured by MRS correlate with IDH1 mutation status.

Abstract It is well recognized that proliferating tumor cells invariably utilize aerobic glycolysis to support their high metabolic demands. Recent studies have further elucidated the paradoxical observation that this increase in glycolysis in proliferating tumor cells is often coupled with a molecular switch from the constitutively high activity PKM1 isoform to the modulated lower activity PKM2 isoform1,2, effectively constraining lower glycolysis at the last pyruvate kinase step. Here, we report an unanticipated link between glucose metabolism and amino-acid metabolic pathways in cancer cells. We characterized the biochemical and cellular effects of a small-molecule allosteric activator of the M2 isoform of pyruvate kinase (AGX-257) in various cancer cell types. We demonstrate that activation of PKM2 results in a metabolic rewiring of specific cancer cells that results in a profound dependency on the presence of the normally non-essential amino acid serine for continued cell proliferation. The induced serine auxotrophy by PKM2 activation is concomitant with reduced flux through the endogenous serine biosynthetic pathway and increased levels of high affinity serine transporters. PKM2 activators, possibly in combination with agents that modulate the cellular and extracellular serine pools, could form the basis for a new approach toward developing therapy for treating cancer. References: 1 Christofk, H. R. et al. The M2 splice isoform of pyruvate kinase is important for cancer metabolism and tumour growth. Nature 452, 230-233 (2008). 2 Clower, C. V. et al. The alternative splicing repressors hnRNP A1/A2 and PTB influence pyruvate kinase isoform expression and cell metabolism. Proc Natl Acad Sci U S A 107, 1894-1899 (2010). 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 1002. doi:1538-7445.AM2012-1002

Cancer cells adapt their metabolic processes to drive macromolecular biosynthesis for rapid cell growth and proliferation (1,2). RNAi-based loss of function screening has proven powerful for the identification of novel and interesting cancer targets, and recent studies have used this technology in vivo to identify novel tumor suppressor genes (3). Here, we developed a method for identifying novel cancer targets via negative selection RNAi screening in solid tumours. Using this method, we screened a set of metabolic genes associated with aggressive breast cancer and stemness to identify those required for in vivo tumourigenesis. Among the genes identified, phosphoglycerate Correspondence and requests for materials should be addressed to D.M.S. (sabatini@wi.mit.edu). Supplementary Information is linked to the online version of the paper at www.nature.com/nature. Author Contributions R.L.P. and D.M.S. conceived the project and designed the experiments. R.L.P performed the screening, knockdown, cell proliferation and tumour formation experiments. K.B., Y.D.S., F.G.B., M.E.P., P.P.S., K.O., Z-Y.T., N.Y.K. and W.W.C assisted with experiments. E.F.B. collected breast cancer patient samples and scored PHGDH IHC. D.K. performed and M.MK. assisted with interpretation of PHGDH IHC. K.M., S.S., H-K.W., A.K.J. and E.D. performed metabolite profiling and flux experiments. N.S., J.B. and L.A.G. assisted with amplification data. G.S.C and D.E.R. assisted with screening technology. B.Y. and A.M.C. provided bioinformatic support. R.L.P wrote and D.M.S. edited the manuscript. Author Information Reprints and permissions information is available at www.nature.com/reprints. The authors declare competing financial interests: details accompany the full-text HTML version of the paper at www.nature.com/nature. NIH Public Access Author Manuscript Nature. Author manuscript; available in PMC 2012 May 16. Published in final edited form as: Nature. ; 476(7360): 346–350. doi:10.1038/nature10350. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript dehydrogenase (PHGDH) is in a genomic region of recurrent copy number gain in breast cancer and PHGDH protein levels are elevated in 70% of ER-negative breast cancers. PHGDH catalyzes the first step in the serine biosynthesis pathway, and breast cancer cells with high PHGDH expression have elevations in serine synthesis flux. Suppression of PHGDH in cell lines with elevated PHGDH expression, but not those without, causes a strong decrease in cell proliferation and a reduction in serine synthesis. We find that PHGDH suppression does not affect intracellular serine levels, but causes a drop in the levels of alpha-ketoglutarate, another output of the pathway and a TCA cycle intermediate. In cells with high PHGDH expression, the serine synthesis pathway contributes approximately 50% of the total anaplerotic flux of glutamine into the TCA cycle. These results reveal that certain breast cancers are dependent upon increased serine pathway flux caused by PHGDH over-expression and demonstrate the utility of in vivo negative selection RNAi screens for finding potential anticancer targets. As a starting point for identifying metabolic genes required for tumourigenesis, we crossreferenced maps of metabolic pathways with the KEGG database to compile a comprehensive list of 2,752 genes encoding all known human metabolic enzymes and transporters (Supplementary Table 1). Public oncogenomic data were analyzed to score genes based on three properties: (i) higher expression in tumours versus normal tissues, (ii) high expression in aggressive breast cancer, or (iii) association with the stem cell state (Fig. 1a). Genes scoring in two of these three categories as well as those at the top of each category were selected to define a high priority set of 133 metabolic enzyme and transporter genes (Supplementary Table 2). We assembled lentiviral shRNA vectors targeting these genes (median 5 shRNAs per gene) and used them to generate two libraries of shRNAexpressing lentiviruses, one containing 235 distinct shRNAs (targeting transporters and control genes) and the other 516 distinct shRNAs (targeting metabolic enzymes and control genes) (4). To identify genes that may be essential for tumourigenesis, the libraries were screened for shRNAs that become depleted during breast tumour formation in mice. Human MCF10DCIS.COM cells (5) were chosen for the screens because, of several breast cancer lines examined, these were capable of forming tumours upon injection of the fewest number of cells. 1.5 million MCF10DCIS.COM cells were infected with each library so that each cell carried one viral integrant, and ~500–1000 cells per shRNA (100,000–1 million cells total) were injected into mouse mammary fat pads at two sites per animal (Supplementary Discussion). Twenty-eight days later orthotopic tumours were harvested and massively parallel DNA sequencing was used to determine the abundance of each shRNA in genomic DNA from tumours and initially injected cells (Fig. 1b). shRNA abundances correlated well between replicate tumours (Fig. 1c) and 5 or 12 tumours per library were analyzed to identify shRNAs that became significantly depleted during tumour formation. Sixteen genes were designated hits in the screen, with at least 75% of the shRNAs targeting these genes scoring (Fig. 1d and Supplementary Table 3). Several genes previously shown to have important roles in cancer emerged as hits, including the mitochondrial ATP transporter VDAC1; the lactic acid transporter SLC16A3; and the nucleotide synthesis genes GMPS and CTPS. The hit list also includes genes involved in the control of oxidative stress (SOD2, GLS2, SEPHS1), the pentose phosphate pathway (TALDO1) glycolysis (GAPDH, TPI1), and in the proline (PYCR1) and serine (PHGDH) biosynthetic pathways. An analogous pooled screen carried out in MCF10DCIS.com cells grown in culture rather than in tumor xenografts revealed that of 20 genes that scored in the in vitro screen, 10 also scored in the in vivo screen (Supplementary Fig. 2a, Supplementary Table 3 and Supplementary Discussion). Interestingly, AK2, which encodes an adenylate Possemato et al. Page 2 Nature. Author manuscript; available in PMC 2012 May 16. N IH PA Athor M anscript N IH PA Athor M anscript N IH PA Athor M anscript kinase that generates ADP from ATP and AMP, was required for in vitro but not in vivo growth (Supplementary Fig. 2b). For five hit genes (PHGDH, GMPS, SLC16A3, PYCR1, and VDAC1), two scoring shRNAs were tested for their effects on tumour formation. Each of these shRNAs suppressed expression of their targets in MCF10DCIS.com cells and reduced tumor forming capacity. (Fig. 1e, Supplementary Fig. 2c). For reasons discussed below, PHGDH was of particular interest, and the three shRNAs that scored in the in vivo screen also decreased PHGDH protein expression and two shRNAs of differing knockdown efficacies inhibited tumour growth consistent with their capacity to suppress PHGDH expression (Fig. 1e). Moreover, tumours derived from cells that in culture had confirmed reductions in PHGDH levels had, in immunohistochemical (Supplementary Fig. 3a) and immunoblotting assays (Supplementary Fig. 3b), PHGDH staining or levels similar to control tumours, suggesting that tumourigenesis selected for cells that lost shRNA-mediated PHGDH suppression. To prioritize genes for follow up studies we consulted a recently available analysis of copy number alteration across cancer genomes (6). Indeed, PHGDH exists in a region of chromosome 1p commonly amplified in breast cancer and melanoma (Fig. 2a), as well as in several other cancer types (not shown). In total, 18% of patient derived breast cancer cell lines and 6% of primary tumours have amplifications in PHGDH. In the datasets examined, none of the other hit genes are in genomic regions of focal and recurrent copy number gain. Our meta analysis for genes associated with aggressive breast cancer is corroborated by a previous study which found elevated PHGDH mRNA levels in breast cancers that are ERnegative, of the basal type, and associated with poor 5-year survival (7). We confirmed these associations in distinct gene expression datasets (Fig. 2b) and additionally found that PHGDH is elevated in ER-negative breast cancer relative to normal breast tissue (Fig. 2b). Of all the genes identified as hits in our screen, PHGDH has the most significantly elevated expression in ER-negative breast cancer (Supplementary Fig. 4). Moreover, by analyzing 82 human breast tumour samples with an immunohistochemical assay for PHGDH, we found that PHGDH protein levels correlate significantly with ER-negative status (Fig. 2c). In total, compared to ER-positive breast tumours, ~68% and ~70% of ER-negative breast tumours have elevations of PHGDH at the mRNA and protein levels, respectively (Fig. 2b, 2c and Supplementary Methods). ER-negative breast cancer comprises approximately 20–25% of all breast cancer cases, but as many as 50% of all breast cancer deaths within 5 years of diagnosis (8), underscoring the importance of identifying additional drug targets for this class of breast cancer. Across a set of breast cancer lines, four lines with PHGDH amplifications had 8–12 fold higher PHGDH protein expression compared to non-transformed MCF10A and ER-positive MCF7 cell lines, which do not have PHGDH amplifications (Fig. 2d). Mechanisms other than gene copy number increases must also exist for boosting PHGDH expression because PHGDH protein levels were also elevated in two ER-negative cell lines (MT3, Hs578T) lacking the PHGDH amplification (Fig. 2e). This is consistent with the finding that PHGDH expression is upregulated at the mRNA and protein level in a higher fraction of ER-negative breast cancers than the fraction exhibiting amplification at the DNA level. Interestingly, PHGDH is also expressed 4-fold more in the MCF10DCIS.COM cells used in the in vivo screen than in two parent

An in vivo RNAi screen of metabolic enzymes and transporters is used to identify, among other genes, phosphoglycerate dehydrogenase (PHGDH) as a gene required for breast tumour growth. PHGDH resides in a region of chromosome 1p that is often amplified in breast cancers, leading to PHGDH overexpression. Elevated levels of PHGDH cause increased metabolic flux through the serine synthesis pathway, which in turn contributes significantly to the flux of glutamine to α-ketoglutarate through the tricarboxylic acid cycle. These observations suggest that targeting PHGDH or the serine biosynthesis pathway in general might be of therapeutic value in the subset of breast cancers with high PHGDH expression. Cancer cells adapt their metabolic processes to drive macromolecular biosynthesis for rapid cell growth and proliferation1,2. RNA interference (RNAi)-based loss-of-function screening has proven powerful for the identification of new and interesting cancer targets, and recent studies have used this technology in vivo to identify novel tumour suppressor genes3. Here we developed a method for identifying novel cancer targets via negative-selection RNAi screening using a human breast cancer xenograft model at an orthotopic site in the mouse. Using this method, we screened a set of metabolic genes associated with aggressive breast cancer and stemness to identify those required for in vivo tumorigenesis. Among the genes identified, phosphoglycerate dehydrogenase (PHGDH) is in a genomic region of recurrent copy number gain in breast cancer and PHGDH protein levels are elevated in 70% of oestrogen receptor (ER)-negative breast cancers. PHGDH catalyses the first step in the serine biosynthesis pathway, and breast cancer cells with high PHGDH expression have increased serine synthesis flux. Suppression of PHGDH in cell lines with elevated PHGDH expression, but not in those without, causes a strong decrease in cell proliferation and a reduction in serine synthesis. We find that PHGDH suppression does not affect intracellular serine levels, but causes a drop in the levels of α-ketoglutarate, another output of the pathway and a tricarboxylic acid (TCA) cycle intermediate. In cells with high PHGDH expression, the serine synthesis pathway contributes approximately 50% of the total anaplerotic flux of glutamine into the TCA cycle. These results reveal that certain breast cancers are dependent upon increased serine pathway flux caused by PHGDH overexpression and demonstrate the utility of in vivo negative-selection RNAi screens for finding potential anticancer targets.

Mutations in the enzyme cytosolic isocitrate dehydrogenase 1 (IDH1) are a common feature of a major subset of primary human brain cancers. These mutations occur at a single amino acid residue of the IDH1 active site, resulting in loss of the enzyme’s ability to catalyse conversion of isocitrate to α-ketoglutarate. However, only a single copy of the gene is mutated in tumours, raising the possibility that the mutations do not result in a simple loss of function. Here we show that cancer-associated IDH1 mutations result in a new ability of the enzyme to catalyse the NADPH-dependent reduction of α-ketoglutarate to R(-)-2-hydroxyglutarate (2HG). Structural studies demonstrate that when arginine 132 is mutated to histidine, residues in the active site are shifted to produce structural changes consistent with reduced oxidative decarboxylation of isocitrate and acquisition of the ability to convert α-ketoglutarate to 2HG. Excess accumulation of 2HG has been shown to lead to an elevated risk of malignant brain tumours in patients with inborn errors of 2HG metabolism. Similarly, in human malignant gliomas harbouring IDH1 mutations, we find markedly elevated levels of 2HG. These data demonstrate that the IDH1 mutations result in production of the onco-metabolite 2HG, and indicate that the excess 2HG which accumulates in vivo contributes to the formation and malignant progression of gliomas. A high percentage of human glioblastomas has been found to harbour mutations in the metabolic enzyme cytosolic isocitrate dehydrogenase 1 (IDH1). The predominant R132H mutation is now shown to act as a gain-of-function mutation, enabling IDH1 to convert α-ketoglutarate to 2-hydroxyglutarate (2-HG). Human glioblastoma samples with IDH1 mutations indeed contain elevated levels of 2-HG. Future work will be directed at understanding the mechanisms by which 2-HG can contribute to tumorigenesis. Mutations in the enzyme cytosolic isocitrate dehydrogenase 1 (IDH1) are commonly found in glioblastomas, a major subset of primary human brain cancers. However, only a single copy of the gene is mutated, suggesting that the mutation does not result in a simple loss of function. Here, IDH1 mutations are shown to act in a gain-of-function manner, resulting in a new ability of the enzyme to catalyse α-ketoglutarate to R(-)-2-hydroxyglutarate, an onco-metabolite.

Mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2), are present in most gliomas and secondary glioblastomas, but are rare in other neoplasms. IDH1/2 mutations are heterozygous, and affect a single arginine residue. Recently, IDH1 mutations were identified in 8% of acute myelogenous leukemia (AML) patients. A glioma study revealed that IDH1 mutations cause a gain-of-function, resulting in the production and accumulation of 2-hydroxyglutarate (2-HG). Genotyping of 145 AML biopsies identified 11 IDH1 R132 mutant samples. Liquid chromatography-mass spectrometry metabolite screening revealed increased 2-HG levels in IDH1 R132 mutant cells and sera, and uncovered two IDH2 R172K mutations. IDH1/2 mutations were associated with normal karyotypes. Recombinant IDH1 R132C and IDH2 R172K proteins catalyze the novel nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reduction of alpha-ketoglutarate (alpha-KG) to 2-HG. The IDH1 R132C mutation commonly found in AML reduces the affinity for isocitrate, and increases the affinity for NADPH and alpha-KG. This prevents the oxidative decarboxylation of isocitrate to alpha-KG, and facilitates the conversion of alpha-KG to 2-HG. IDH1/2 mutations confer an enzymatic gain of function that dramatically increases 2-HG in AML. This provides an explanation for the heterozygous acquisition of these mutations during tumorigenesis. 2-HG is a tractable metabolic biomarker of mutant IDH1/2 enzyme activity.

Mutations in isocitrate dehydrogenase 1 and 2 (IDH1/2), are present in most gliomas and secondary glioblastomas, but are rare in other neoplasms. IDH1/2 mutations are heterozygous, and affect a single arginine residue. Recently, IDH1 mutations were identified in 8% of acute myelogenous leukemia (AML) patients. Our previous study revealed that IDH1 mutations cause a gain of function, resulting in the production and accumulation of 2-hydroxyglutarate (2-HG). Genotyping of 145 AML biopsies identified 11 IDH1 R132 mutant samples. Liquid chromatography-mass spectrometry metabolite screening revealed increased 2-HG levels in IDH1 R132 mutant cells and sera, and uncovered two IDH2 R172K mutations. IDH1/2 mutations were associated with normal karyotypes. Recombinant IDH1 R132C and IDH2 R172K proteins catalyze the novel NADPH -dependent reduction of alpha-ketoglutarate (a-KG) to 2-HG. The IDH1 R132C mutation commonly found in AML reduces the affinity for isocitrate, and increases the affinity for NADPH and a-KG. This prevents the oxidative decarboxylation of isocitrate to a-KG, and facilitates the conversion of a-KG to 2-HG. IDH1/2 mutations confer an enzymatic gain of function that dramatically increases 2-HG in AML. This provides an explanation for the heterozygous acquisition of these mutations during tumorigenesis. 2-HG is a tractable metabolic biomarker of mutant IDH1/2 enzyme activity. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5452.