1601
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Curry MC, Peters AA, Kenny PA, Roberts-Thomson SJ, Monteith GR. Mitochondrial calcium uniporter silencing potentiates caspase-independent cell death in MDA-MB-231 breast cancer cells. Biochem Biophys Res Commun 2013; 434:695-700. [DOI: 10.1016/j.bbrc.2013.04.015] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 04/11/2013] [Indexed: 01/08/2023]
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1602
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Lee C, Yen K, Cohen P. Humanin: a harbinger of mitochondrial-derived peptides? Trends Endocrinol Metab 2013; 24:222-8. [PMID: 23402768 PMCID: PMC3641182 DOI: 10.1016/j.tem.2013.01.005] [Citation(s) in RCA: 190] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 01/04/2013] [Accepted: 01/10/2013] [Indexed: 11/18/2022]
Abstract
Mitochondria have been largely considered as 'end-function' organelles, servicing the cell by producing energy and regulating cell death in response to complex signals. Being cellular entities with vital roles, mitochondria communicate back to the cell and actively engage in determining major cellular policies. These signals, collectively referred to as retrograde signals, are encoded in the nuclear genome or are secondary products of mitochondrial metabolism. Here, we discuss humanin, the first small peptide of a putative set of mitochondrial-derived peptides (MDPs), which exhibits strong cytoprotective actions against various stress and disease models. The study of humanin and other mitochondrial-derived retrograde signal peptides will aid in the identification of genes and peptides with therapeutic and diagnostic potential in treating human diseases.
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Affiliation(s)
- Changhan Lee
- University of Southern California Davis School of Gerontology, Ethel Percy Andrus Gerontology Center, University of Southern California, Los Angeles, CA 90089-0191, USA
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1603
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Peck B, Ferber EC, Schulze A. Antagonism between FOXO and MYC Regulates Cellular Powerhouse. Front Oncol 2013; 3:96. [PMID: 23630664 PMCID: PMC3635031 DOI: 10.3389/fonc.2013.00096] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 04/08/2013] [Indexed: 11/13/2022] Open
Abstract
Alterations in cellular metabolism are a key feature of the transformed phenotype. Enhanced macromolecule synthesis is a prerequisite for rapid proliferation but may also contribute to induction of angiogenesis, metastasis formation, and tumor progression, thereby leading to a poorer clinical outcome. Metabolic adaptations enable cancer cells to survive in suboptimal growth conditions, such as the limited supply of nutrient and oxygen often found in the tumor microenvironment. Metabolic changes, including activation of glycolysis and inhibition of mitochondrial ATP production, are induced under hypoxia to promote survival in low oxygen. FOXO3a, a transcription factor that is inhibited by the phosphatidylinositol 3-kinase/Akt pathway and is upregulated in hypoxia, has emerged as an important negative regulator of MYC function. Recent studies have revealed that FOXO3a acts as a negative regulator of mitochondrial function through inhibition of MYC. Ablation of FOXO3a prevents the inhibition of mitochondrial function induced by hypoxia and results in enhanced oxidative stress. This review will focus on the antagonism between FOXO3a and MYC and discuss their role in cellular bioenergetics, reactive oxygen metabolism, and adaptation to hypoxia, raising questions about the role of FOXO proteins in cancer.
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Affiliation(s)
- Barrie Peck
- Gene Expression Analysis Laboratory, Cancer Research UK, London Research Institute London, UK
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1604
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Chen YF, Chen YT, Chiu WT, Shen MR. Remodeling of calcium signaling in tumor progression. J Biomed Sci 2013; 20:23. [PMID: 23594099 PMCID: PMC3639169 DOI: 10.1186/1423-0127-20-23] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 04/08/2013] [Indexed: 02/06/2023] Open
Abstract
Intracellular Ca2+ is one of the crucial signalings that modulate various cellular functions. The dysregulation of Ca2+ homeostasis has been suggested as an important event in driving the expression of the malignant phenotypes, such as proliferation, migration, invasion, and metastasis. Cell migration is an early prerequisite for tumor metastasis that has a significant impact on patient prognosis. During cell migration, the exquisite spatial and temporal organization of intracellular Ca2+ provides a rapid and robust way for the selective activation of signaling components that play a central role in cytoskeletal reorganization, traction force generation, and focal adhesion dynamics. A number of known molecular components involved in Ca2+ influx pathways, including stromal interaction molecule (STIM)/Orai-mediated store-operated Ca2+ entry (SOCE) and the Ca2+-permeable transient receptor potential (TRP) channels, have been implicated in cancer cell migration and tumor metastasis. The clinical significance of these molecules, such as STIM proteins and the TRPM7 channel, in tumor progression and their diagnostic and prognostic potentials have also been demonstrated in specific cancer types. In this review, we summarize the recent advances in understanding the important roles and regulatory mechanisms of these Ca2+ influx pathways on malignant behaviors of tumor cells. The clinical implications in facilitating current diagnostic and therapeutic procedures are also discussed.
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Affiliation(s)
- Yih-Fung Chen
- Department of Pharmacology, National Cheng Kung University, Tainan, Taiwan
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1605
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Abstract
The classical Mendelian genetic perspective has failed to adequately explain the biology and genetics of common metabolic and degenerative diseases. This is because these diseases are primarily systemic bioenergetic diseases, and the most important energy genes are located in the cytoplasmic mitochondrial DNA (mtDNA). Therefore, to understand these "complex" diseases, we must investigate their bioenergetic pathophysiology and consider the genetics of the thousands of copies of maternally inherited mtDNA, the more than 1,000 nuclear DNA (nDNA) bioenergetic genes, and the epigenomic and signal transduction systems that coordinate these dispersed elements of the mitochondrial genome.
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Affiliation(s)
- Douglas C Wallace
- Center for Mitochondrial and Epigenomic Medicine, Children's Hospital of Philadelphia, and Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-4302, USA.
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1606
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Guan JL, Simon AK, Prescott M, Menendez JA, Liu F, Wang F, Wang C, Wolvetang E, Vazquez-Martin A, Zhang J. Autophagy in stem cells. Autophagy 2013; 9:830-49. [PMID: 23486312 DOI: 10.4161/auto.24132] [Citation(s) in RCA: 221] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Autophagy is a highly conserved cellular process by which cytoplasmic components are sequestered in autophagosomes and delivered to lysosomes for degradation. As a major intracellular degradation and recycling pathway, autophagy is crucial for maintaining cellular homeostasis as well as remodeling during normal development, and dysfunctions in autophagy have been associated with a variety of pathologies including cancer, inflammatory bowel disease and neurodegenerative disease. Stem cells are unique in their ability to self-renew and differentiate into various cells in the body, which are important in development, tissue renewal and a range of disease processes. Therefore, it is predicted that autophagy would be crucial for the quality control mechanisms and maintenance of cellular homeostasis in various stem cells given their relatively long life in the organisms. In contrast to the extensive body of knowledge available for somatic cells, the role of autophagy in the maintenance and function of stem cells is only beginning to be revealed as a result of recent studies. Here we provide a comprehensive review of the current understanding of the mechanisms and regulation of autophagy in embryonic stem cells, several tissue stem cells (particularly hematopoietic stem cells), as well as a number of cancer stem cells. We discuss how recent studies of different knockout mice models have defined the roles of various autophagy genes and related pathways in the regulation of the maintenance, expansion and differentiation of various stem cells. We also highlight the many unanswered questions that will help to drive further research at the intersection of autophagy and stem cell biology in the near future.
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Affiliation(s)
- Jun-Lin Guan
- Division of Molecular Medicine, Department of Internal Medicine and Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA.
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1607
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Zhang R. MNADK, a novel liver-enriched mitochondrion-localized NAD kinase. Biol Open 2013; 2:432-8. [PMID: 23616928 PMCID: PMC3625872 DOI: 10.1242/bio.20134259] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 02/04/2013] [Indexed: 11/28/2022] Open
Abstract
NADP+ and its reducing equivalent NADPH are essential for counteracting oxidative damage. Mitochondria are the major source of oxidative stress, since the majority of superoxide is generated from the mitochondrial respiratory chain. Because NADP+ cannot pass through the mitochondrial membrane, NADP+ generation within mitochondria is critical. However, only a single human NAD kinase (NADK) has been identified, and it is localized to the cytosol. Therefore, sources of mitochondrial NADP+ and mechanisms for maintaining its redox balance remain largely unknown. Here, we show that the uncharacterized human gene C5ORF33, named MNADK (mouse homologue 1110020G09Rik), encodes a novel mitochondrion-localized NAD kinase. In mice MNADK is mostly expressed in the liver, and also abundant in brown fat, heart, muscle and kidney, all being mitochondrion-rich. Indeed, MNADK is localized to mitochondria in Hep G2 cells, a human liver cell line, as demonstrated by fluorescence imaging. Having a conserved NAD kinase domain, a recombinant MNADK showed NAD kinase activity, confirmed by mass spectrometry analysis. Consistent with a role of NADP+ as a coenzyme in anabolic reactions, such as lipid synthesis, MNADK is nutritionally regulated in mice. Fasting increased MNADK levels in liver and fat, and obesity dramatically reduced its level in fat. MNADK expression was suppressed in human liver tumors. Identification of MNADK immediately suggests a model in which NADK and MNADK are responsible for de novo synthesis of NADP+ in cytosol and mitochondria, respectively, and therefore provides novel insights into understanding the sources and mechanisms of mitochondrial NADP+ and NADH production in human cells.
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Affiliation(s)
- Ren Zhang
- Center for Molecular Medicine and Genetics, School of Medicine, Wayne State University , Detroit, MI 48201 , USA
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1608
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Gonzalez C. Drosophila melanogaster: a model and a tool to investigate malignancy and identify new therapeutics. Nat Rev Cancer 2013; 13:172-83. [PMID: 23388617 DOI: 10.1038/nrc3461] [Citation(s) in RCA: 206] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
For decades, lower-model organisms such as Drosophila melanogaster have often provided the first glimpse into the mechanism of action of human cancer-related proteins, thus making a substantial contribution to elucidating the molecular basis of the disease. More recently, D. melanogaster strains that are engineered to recapitulate key aspects of specific types of human cancer have been paving the way for the future role of this 'workhorse' of biomedical research, helping to further investigate the process of malignancy, and serving as platforms for therapeutic drug discovery.
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Affiliation(s)
- Cayetano Gonzalez
- IRB-Barcelona, c/Baldiri Reixac 10-12, Barcelona, Spain. gonzalez@ irbbarcelona.org
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1609
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Strauss KA, DuBiner L, Simon M, Zaragoza M, Sengupta PP, Li P, Narula N, Dreike S, Platt J, Procaccio V, Ortiz-González XR, Puffenberger EG, Kelley RI, Morton DH, Narula J, Wallace DC. Severity of cardiomyopathy associated with adenine nucleotide translocator-1 deficiency correlates with mtDNA haplogroup. Proc Natl Acad Sci U S A 2013; 110:3453-8. [PMID: 23401503 PMCID: PMC3587196 DOI: 10.1073/pnas.1300690110] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Mutations of both nuclear and mitochondrial DNA (mtDNA)-encoded mitochondrial proteins can cause cardiomyopathy associated with mitochondrial dysfunction. Hence, the cardiac phenotype of nuclear DNA mitochondrial mutations might be modulated by mtDNA variation. We studied a 13-generation Mennonite pedigree with autosomal recessive myopathy and cardiomyopathy due to an SLC25A4 frameshift null mutation (c.523delC, p.Q175RfsX38), which codes for the heart-muscle isoform of the adenine nucleotide translocator-1. Ten homozygous null (adenine nucleotide translocator-1(-/-)) patients monitored over a median of 6 years had a phenotype of progressive myocardial thickening, hyperalaninemia, lactic acidosis, exercise intolerance, and persistent adrenergic activation. Electrocardiography and echocardiography with velocity vector imaging revealed abnormal contractile mechanics, myocardial repolarization abnormalities, and impaired left ventricular relaxation. End-stage heart disease was characterized by massive, symmetric, concentric cardiac hypertrophy; widespread cardiomyocyte degeneration; overabundant and structurally abnormal mitochondria; extensive subendocardial interstitial fibrosis; and marked hypertrophy of arteriolar smooth muscle. Substantial variability in the progression and severity of heart disease segregated with maternal lineage, and sequencing of mtDNA from five maternal lineages revealed two major European haplogroups, U and H. Patients with the haplogroup U mtDNAs had more rapid and severe cardiomyopathy than those with haplogroup H.
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Affiliation(s)
- Kevin A. Strauss
- Clinic for Special Children, Strasburg, PA 17579
- Department of Biology, Franklin and Marshall College, Lancaster, PA 17603
- Lancaster General Hospital, Lancaster, PA 17602
| | - Lauren DuBiner
- Department of Biology, Franklin and Marshall College, Lancaster, PA 17603
| | - Mariella Simon
- Departments of Pediatrics and Biological Chemistry and Center for Molecular and Mitochondrial Medicine and Genetics, University of California, Irvine, CA 92697
| | - Michael Zaragoza
- Departments of Pediatrics and Biological Chemistry and Center for Molecular and Mitochondrial Medicine and Genetics, University of California, Irvine, CA 92697
| | | | - Peng Li
- Department of Medicine, University of California, Irvine, CA 92697
| | - Navneet Narula
- Department of Pathology, Weill Cornell Medical College, New York, NY 10019
| | - Sandra Dreike
- Departments of Pediatrics and Biological Chemistry and Center for Molecular and Mitochondrial Medicine and Genetics, University of California, Irvine, CA 92697
- Kapiolani Medical Center for Women and Children, Honolulu, HI 96826
| | - Julia Platt
- Departments of Pediatrics and Biological Chemistry and Center for Molecular and Mitochondrial Medicine and Genetics, University of California, Irvine, CA 92697
- Department of Pediatrics, Stanford University School of Medicine, Palo Alto, CA 94305
| | - Vincent Procaccio
- Departments of Pediatrics and Biological Chemistry and Center for Molecular and Mitochondrial Medicine and Genetics, University of California, Irvine, CA 92697
- Biochemistry and Genetics Department, National Center for Neurodegenerative and Mitochondrial Diseases, Centre Hospitalier Universitaire d' Angers, 49933 Angers, France
| | - Xilma R. Ortiz-González
- Center for Mitochondrial and Epigenomic Medicine, Children’s Hospital of Philadelphia and Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104; and
| | - Erik G. Puffenberger
- Clinic for Special Children, Strasburg, PA 17579
- Department of Biology, Franklin and Marshall College, Lancaster, PA 17603
| | - Richard I. Kelley
- Kennedy Krieger Institute, The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - D. Holmes Morton
- Clinic for Special Children, Strasburg, PA 17579
- Department of Biology, Franklin and Marshall College, Lancaster, PA 17603
- Lancaster General Hospital, Lancaster, PA 17602
| | | | - Douglas C. Wallace
- Departments of Pediatrics and Biological Chemistry and Center for Molecular and Mitochondrial Medicine and Genetics, University of California, Irvine, CA 92697
- Center for Mitochondrial and Epigenomic Medicine, Children’s Hospital of Philadelphia and Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104; and
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1610
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Metabolic changes in cancer cells upon suppression of MYC. Cancer Metab 2013; 1:7. [PMID: 24280108 PMCID: PMC4178210 DOI: 10.1186/2049-3002-1-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 01/03/2013] [Indexed: 02/07/2023] Open
Abstract
Background Cancer cells engage in aerobic glycolysis and glutaminolysis to fulfill their biosynthetic and energetic demands in part by activating MYC. Previous reports have characterized metabolic changes in proliferating cells upon MYC loss or gain of function. However, metabolic differences between MYC-dependent cancer cells and their isogenic differentiated counterparts have not been characterized upon MYC suppression in vitro. Results Here we report metabolic changes between MYC-dependent mouse osteogenic sarcomas and differentiated osteoid cells induced upon MYC suppression. While osteogenic sarcoma cells increased oxygen consumption and spare respiratory capacity upon MYC suppression, they displayed minimal changes in glucose and glutamine consumption as well as their respective contribution to the citrate pool. However, glutamine significantly induced oxygen consumption in the presence of MYC which was dependent on aminotransferases. Furthermore, inhibition of aminotransferases selectively diminished cell proliferation and survival of osteogenic sarcoma MYC-expressing cells. There were minimal changes in ROS levels and cell death sensitivity to reactive oxygen species (ROS)-inducing agents between osteoid cells and osteogenic sarcoma cells. Nevertheless, the mitochondrial-targeted antioxidant Mito-Vitamin E still diminished proliferation of MYC-dependent osteogenic sarcoma cells. Conclusion These data highlight that aminotransferases and mitochondrial ROS might be attractive targets for cancer therapy in MYC-driven tumors.
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1611
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Kondrashina AV, Papkovsky DB, Dmitriev RI. Measurement of cell respiration and oxygenation in standard multichannel biochips using phosphorescent O2-sensitive probes. Analyst 2013; 138:4915-21. [DOI: 10.1039/c3an00658a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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1612
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Sanchez-Alvarez R, Martinez-Outschoorn UE, Lamb R, Hulit J, Howell A, Gandara R, Sartini M, Rubin E, Lisanti MP, Sotgia F. Mitochondrial dysfunction in breast cancer cells prevents tumor growth: understanding chemoprevention with metformin. Cell Cycle 2012; 12:172-82. [PMID: 23257779 DOI: 10.4161/cc.23058] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Metformin is a well-established diabetes drug that prevents the onset of most types of human cancers in diabetic patients, especially by targeting cancer stem cells. Metformin exerts its protective effects by functioning as a weak "mitochondrial poison," as it acts as a complex I inhibitor and prevents oxidative mitochondrial metabolism (OXPHOS). Thus, mitochondrial metabolism must play an essential role in promoting tumor growth. To determine the functional role of "mitochondrial health" in breast cancer pathogenesis, here we used mitochondrial uncoupling proteins (UCPs) to genetically induce mitochondrial dysfunction in either human breast cancer cells (MDA-MB-231) or cancer-associated fibroblasts (hTERT-BJ1 cells). Our results directly show that all three UCP family members (UCP-1/2/3) induce autophagy and mitochondrial dysfunction in human breast cancer cells, which results in significant reductions in tumor growth. Conversely, induction of mitochondrial dysfunction in cancer-associated fibroblasts has just the opposite effect. More specifically, overexpression of UCP-1 in stromal fibroblasts increases β-oxidation, ketone body production and the release of ATP-rich vesicles, which "fuels" tumor growth by providing high-energy nutrients in a paracrine fashion to epithelial cancer cells. Hence, the effects of mitochondrial dysfunction are truly compartment-specific. Thus, we conclude that the beneficial anticancer effects of mitochondrial inhibitors (such as metformin) may be attributed to the induction of mitochondrial dysfunction in the epithelial cancer cell compartment. Our studies identify cancer cell mitochondria as a clear target for drug discovery and for novel therapeutic interventions.
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1613
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Flanagan S, Lee M, Li CCY, Suter CM, Buckland ME. Promoter Methylation Analysis of IDH Genes in Human Gliomas. Front Oncol 2012; 2:193. [PMID: 23267435 PMCID: PMC3525876 DOI: 10.3389/fonc.2012.00193] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 11/29/2012] [Indexed: 01/22/2023] Open
Abstract
Mutations in isocitrate dehydrogenase (IDH)-1 or -2 are found in the majority of WHO grade II and III astrocytomas and oligodendrogliomas, and secondary glioblastomas. Almost all described mutations are heterozygous missense mutations affecting a conserved arginine residue in the substrate binding site of IDH1 (R132) or IDH2 (R172). But the exact mechanism of IDH mutations in neoplasia is not understood. It has been proposed that IDH mutations impart a “toxic gain-of-function” to the mutant protein, however a dominant-negative effect of mutant IDH has also been described, implying that IDH may function as a tumor suppressor gene. As most, if not all, tumor suppressor genes are inactivated by epigenetic silencing, in a wide variety of tumors, we asked if IDH1 or IDH2 carry the epigenetic signature of a tumor suppressor by assessing cytosine methylation at their promoters. Methylation was quantified in 68 human brain tumors, including both IDH-mutant and IDH wildtype, by bisulfite pyrosequencing. In all tumors examined, CpG methylation levels were less than 8%. Our data demonstrate that inactivation of IDH function through promoter hypermethylation is not common in human gliomas and other brain tumors. These findings do not support a tumor suppressor role for IDH genes in human gliomas.
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Affiliation(s)
- Simon Flanagan
- Discipline of Pathology, University of Sydney Sydney, NSW, Australia ; Department of Neuropathology, Royal Prince Alfred Hospital Sydney, NSW, Australia
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1614
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Sotgia F, Whitaker-Menezes D, Martinez-Outschoorn UE, Salem AF, Tsirigos A, Lamb R, Sneddon S, Hulit J, Howell A, Lisanti MP. Mitochondria "fuel" breast cancer metabolism: fifteen markers of mitochondrial biogenesis label epithelial cancer cells, but are excluded from adjacent stromal cells. Cell Cycle 2012; 11:4390-401. [PMID: 23172368 DOI: 10.4161/cc.22777] [Citation(s) in RCA: 131] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Here, we present new genetic and morphological evidence that human tumors consist of two distinct metabolic compartments. First, re-analysis of genome-wide transcriptional profiling data revealed that > 95 gene transcripts associated with mitochondrial biogenesis and/or mitochondrial translation were significantly elevated in human breast cancer cells, as compared with adjacent stromal tissue. Remarkably, nearly 40 of these upregulated gene transcripts were mitochondrial ribosomal proteins (MRPs), functionally associated with mitochondrial translation of protein components of the OXPHOS complex. Second, during validation by immunohistochemistry, we observed that antibodies directed against 15 markers of mitochondrial biogenesis and/or mitochondrial translation (AKAP1, GOLPH3, GOLPH3L, MCT1, MRPL40, MRPS7, MRPS15, MRPS22, NRF1, NRF2, PGC1-α, POLRMT, TFAM, TIMM9 and TOMM70A) selectively labeled epithelial breast cancer cells. These same mitochondrial markers were largely absent or excluded from adjacent tumor stromal cells. Finally, markers of mitochondrial lipid synthesis (GOLPH3) and mitochondrial translation (POLRMT) were associated with poor clinical outcome in human breast cancer patients. Thus, we conclude that human breast cancers contain two distinct metabolic compartments-a glycolytic tumor stroma, which surrounds oxidative epithelial cancer cells-that are mitochondria-rich. The co-existence of these two compartments is indicative of metabolic symbiosis between epithelial cancer cells and their surrounding stroma. As such, epithelial breast cancer cells should be viewed as predatory metabolic "parasites," which undergo anabolic reprogramming to amplify their mitochondrial "power." This notion is consistent with the observation that the anti-malarial agent chloroquine may be an effective anticancer agent. New anticancer therapies should be developed to target mitochondrial biogenesis and/or mitochondrial translation in human cancer cells.
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Affiliation(s)
- Federica Sotgia
- Jefferson Stem Cell Biology and Regenerative Medicine Center; Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA USA.
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1615
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