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Yu EY, Pérez-Martín J, Holloman WK, Lue NF. Mre11 and Blm-Dependent Formation of ALT-Like Telomeres in Ku-Deficient Ustilago maydis. PLoS Genet 2015; 11:e1005570. [PMID: 26492073 PMCID: PMC4619612 DOI: 10.1371/journal.pgen.1005570] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 09/15/2015] [Indexed: 11/19/2022] Open
Abstract
A subset of human cancer cells uses a specialized, aberrant recombination pathway known as ALT to maintain telomeres, which in these cells are characterized by complex aberrations including length heterogeneity, high levels of unpaired C-strand, and accumulation of extra-chromosomal telomere repeats (ECTR). These phenotypes have not been recapitulated in any standard budding or fission yeast mutant. We found that eliminating Ku70 or Ku80 in the yeast-like fungus Ustilago maydis results initially in all the characteristic telomere aberrations of ALT cancer cells, including C-circles, a highly specific marker of ALT. Subsequently the ku mutants experience permanent G2 cell cycle arrest, accompanied by loss of telomere repeats from chromosome ends and even more drastic accumulation of very short ECTRs (vsECTRs). The deletion of atr1 or chk1 rescued the lethality of the ku mutant, and "trapped" the telomere aberrations in the early ALT-like stage. Telomere abnormalities are telomerase-independent, but dramatically suppressed by deletion of mre11 or blm, suggesting major roles for these factors in the induction of the ALT pathway. In contrast, removal of other DNA damage response and repair factors such as Rad51 has disparate effects on the ALT phenotypes, suggesting that these factors process ALT intermediates or products. Notably, the antagonism of Ku and Mre11 in the induction of ALT is reminiscent of their roles in DSB resection, in which Blm is also known to play a key role. We suggest that an aberrant resection reaction may constitute an early trigger for ALT telomeres, and that the outcomes of ALT are distinct from DSB because of the unique telomere nucleoprotein structure.
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Affiliation(s)
- Eun Young Yu
- Department of Microbiology & Immunology, W. R. Hearst Microbiology Research Center, Weill Medical College of Cornell University, New York, New York, United States of America
| | | | - William K. Holloman
- Department of Microbiology & Immunology, W. R. Hearst Microbiology Research Center, Weill Medical College of Cornell University, New York, New York, United States of America
- Sandra and Edward Meyer Cancer Center, Weill Cornell Medical College, New York, New York, United States of America
| | - Neal F. Lue
- Department of Microbiology & Immunology, W. R. Hearst Microbiology Research Center, Weill Medical College of Cornell University, New York, New York, United States of America
- Sandra and Edward Meyer Cancer Center, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail:
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52
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Martí-Centelles R, Falomir E, Murga J, Carda M, Marco JA. Inhibitory effect of cytotoxic stilbenes related to resveratrol on the expression of the VEGF, hTERT and c-Myc genes. Eur J Med Chem 2015; 103:488-96. [PMID: 26402726 DOI: 10.1016/j.ejmech.2015.09.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 09/08/2015] [Accepted: 09/09/2015] [Indexed: 01/31/2023]
Abstract
A group of thirty-nine stilbene derivatives, prepared by means of Heck coupling reactions, has been investigated for their cytotoxicity, as well as for their ability to inhibit the production of the vascular endothelial growth factor (VEGF) and the activation of telomerase. The ability of these compounds to inhibit proliferation of two tumoral cell lines (HT-29 and MCF-7) and one non tumoral cell line (HEK-293) was first determined. Subsequently, we determined the capacity of the compounds to inhibit the secretion of VEGF in the aforementioned cell lines and to downregulate the expression of the VEGF, hTERT and c-Myc genes, the two latter involved in the control of the activation of telomerase. One of the synthetic stilbenes, (E)-4-(4-methoxystyryl)aniline, showed strong cytotoxicity and proved able to cause a marked decrease both in the secretion of VEGF and in the expression of the hTERT and c-Myc genes, in all cases at concentrations in the low nanomolar range.
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Affiliation(s)
| | - Eva Falomir
- Depart. de Q. Inorgánica y Orgánica, Univ. Jaume I, E-12071, Castellón, Spain.
| | - Juan Murga
- Depart. de Q. Inorgánica y Orgánica, Univ. Jaume I, E-12071, Castellón, Spain
| | - Miguel Carda
- Depart. de Q. Inorgánica y Orgánica, Univ. Jaume I, E-12071, Castellón, Spain.
| | - J Alberto Marco
- Depart. de Q. Orgánica, Univ. de Valencia, E-46100, Burjassot, Valencia, Spain
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Abstract
The key step of carcinogenesis is the malignant transformation which is fundamentally a telomere biology dysfunction permitting cells to bypass the Hayflick limit and to divide indefinitely and uncontrollably. Thus all partners and structures involved in normal and abnormal telomere maintenance, protection and lengthening can be considered as potential anti-cancer therapeutic targets. In this Point of View we discuss, highlight and provide new perspectives from the current knowledge and understanding to position the different aspects of telomere biology and dysfunction as diagnostic, preventive and curative tools in the field of cancer.
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Affiliation(s)
- Philippe Rousseau
- a Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Jewish General Hospital ; Montréal , Québec , Canada
| | - Chantal Autexier
- a Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, Jewish General Hospital ; Montréal , Québec , Canada.,b Division of Experimental Medicine, Department of Anatomy and Cell Biology, McGill University ; Montréal , Québec , Canada
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54
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Vafaiyan Z, Gharaei R, Asadi J. The correlation between telomerase activity and Bax/Bcl-2 ratio in valproic acid-treated MCF-7 breast cancer cell line. IRANIAN JOURNAL OF BASIC MEDICAL SCIENCES 2015; 18:700-4. [PMID: 26351561 PMCID: PMC4556764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Accepted: 05/21/2015] [Indexed: 11/29/2022]
Abstract
OBJECTIVES Valproic acid (VPA), a drug used in the treatment of neurological disorders, has been shown to have cytotoxic effects on cancer cells through different mechanisms. Telomerase, a ribonucleoprotein reverse transcriptase, is responsible for elongation of the telomere and is activated in cancers. A relation between telomerase activity and resistance to apoptosis has been established. This study focused on probable effects of VPA on MCF-7 cancer cells. In particular, we investigated VPA effects on viability, apoptosis and telomerase activity. MATERIALS AND METHODS Cytotoxicity effects of VPA on MCF-7 cells were determined by neutral red uptake assay. Cells were treated with different concentrations of VPA (0-32 mM) and telomerase activity and Bax and Bcl-2 protein levels were determined using TRAP assay (PCR-ELISA) method and ELISA method, respectively. RESULTS The cytotoxic effects of different concentration of VPA on MCF-7 cells were observed as a reduction in cell viability and telomerase activity and altered expression of Bcl-2 family protein levels. The results also showed that there is a significant correlation between reduction of telomerase activity and increase in Bax/Bcl-2 ratio (P=0.001). CONCLUSION Our study demonstrated that cell viability of MCF-7 cells was decreased after treatment with VPA, probably through a reduction of telomerase activity and an increase in Bax/bcl-2 ratio. Therefore, it could be concluded that VPA is a potent anti-cancer agent for breast cancer cells through inhibition of telomerase activity and induction of apoptosis.
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Affiliation(s)
- Zahra Vafaiyan
- Department of Biochemistry and Biophysics, Disorder Metabolic Research Center, Golestan University of Medical Sciences, Gorgan, Iran
| | - Roghaye Gharaei
- Department of Biochemistry and Biophysics, Disorder Metabolic Research Center, Golestan University of Medical Sciences, Gorgan, Iran
| | - Jahanbakhsh Asadi
- Department of Biochemistry and Biophysics, Disorder Metabolic Research Center, Golestan University of Medical Sciences, Gorgan, Iran,Corresponding author: Jahanbakhsh Asadi. Department of Biochemistry and Biophysics, Disorder Metabolic Research Center, Golestan University of Medical Sciences, Gorgan, Iran. Tel: +98-17-32440225; Fax: +98-17-32421651;
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55
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Reddel RR. Telomere maintenance mechanisms in cancer: clinical implications. Curr Pharm Des 2015; 20:6361-74. [PMID: 24975603 PMCID: PMC4262939 DOI: 10.2174/1381612820666140630101047] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 06/26/2014] [Indexed: 01/20/2023]
Abstract
The presence of immortal cell populations with an up-regulated telomere maintenance mechanism (TMM) is an almost universal characteristic of cancers, whereas normal somatic cells are unable to prevent proliferation-associated telomere shortening and have a limited proliferative potential. TMMs and related aspects of telomere structure and function therefore appear to be ideal targets for the development of anticancer therapeutics. Such treatments would be targeted to a specific cancer-related molecular abnormality, and also be broad-spectrum in that they would be expected to be potentially applicable to most cancers. However, the telomere biology of normal and malignant human cells is a relatively young research field with large numbers of unanswered questions, so the optimal design of TMM-targeted therapeutic approaches remains unclear. This review outlines the opportunities and challenges presented by telomeres and TMMs for clinical management of cancer.
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Affiliation(s)
- Roger R Reddel
- Children's Medical Research Institute, 214 Hawkesbury Road, Westmead, New South Wales 2145, Australia.
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56
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Hsieh MH, Tsai CH, Lin CC, Li TK, Hung TW, Chang LT, Hsin LW, Teng SC. Topoisomerase II inhibition suppresses the proliferation of telomerase-negative cancers. Cell Mol Life Sci 2015; 72:1825-37. [PMID: 25430478 PMCID: PMC11113807 DOI: 10.1007/s00018-014-1783-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Revised: 11/10/2014] [Accepted: 11/13/2014] [Indexed: 10/24/2022]
Abstract
Telomere maintenance is required for chromosome stability, and telomeres are typically elongated by telomerase following DNA replication. In both tumor and yeast cells that lack telomerase, telomeres are maintained via an alternative recombination mechanism. Previous studies have indicated that yeast Sgs1 and Top3 may work together to remove highly negative supercoils that are generated from recombination. However, the mechanism by which cells eradicate highly positive supercoils during recombination remains unclear. In the present study, we demonstrate that TOP2 is involved in telomere-telomere recombination. Disturbance of telomeric structure by RIF1 or RIF2 deletion alleviates the requirement for TOP2 in telomere-telomere recombination. In human telomerase-negative alternative lengthening of telomere (ALT) cells, TOP2α or TOP2β knockdown decreases ALT-associated PML bodies, increases telomere dysfunction-induced foci and triggers telomere shortening. Similar results were observed when ALT cells were treated with ICRF-193, a TOP2 inhibitor. Importantly, ICRF-193 treatment blocks ALT-associated phenotypes in vitro, causes telomere shortening, and inhibits ALT cell proliferation in mice. Taken together, these findings imply that TOP2 is involved in the ALT pathway, perhaps by resolving the highly positive supercoil structure at the front of the helicase. Inhibition of topoisomerase II may be a promising therapeutic approach that can be used to prevent cell proliferation in ALT-type cancer cells.
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Affiliation(s)
- Meng-Hsun Hsieh
- Department of Microbiology, College of Medicine, National Taiwan University, No. 1, Sec. 1, Jen-Ai Road, Taipei, 100, Taiwan,
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A combination of the telomerase inhibitor, BIBR1532, and paclitaxel synergistically inhibit cell proliferation in breast cancer cell lines. Target Oncol 2015; 10:565-73. [DOI: 10.1007/s11523-015-0364-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 03/05/2015] [Indexed: 10/23/2022]
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58
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Tahtouh R, Azzi AS, Alaaeddine N, Chamat S, Bouharoun-Tayoun H, Wardi L, Raad I, Sarkis R, Antoun NA, Hilal G. Telomerase inhibition decreases alpha-fetoprotein expression and secretion by hepatocellular carcinoma cell lines: in vitro and in vivo study. PLoS One 2015; 10:e0119512. [PMID: 25822740 PMCID: PMC4379025 DOI: 10.1371/journal.pone.0119512] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 01/13/2015] [Indexed: 12/13/2022] Open
Abstract
Alpha-fetoprotein (AFP) is a diagnostic marker for hepatocellular carcinoma (HCC). A direct relationship between poor prognosis and the concentration of serum AFP has been observed. Telomerase, an enzyme that stabilizes the telomere length, is expressed by 90% of HCC. The aim of this study was to investigate the effect of telomerase inhibition on AFP secretion and the involvement of the PI3K/Akt/mTOR signaling pathway. Proliferation and viability tests were performed using tetrazolium salt. Apoptosis was determined through the Annexin V assay using flow cytometry. The concentrations of AFP were measured using ELISA kits. The AFP mRNA expression was evaluated using RT-PCR, and cell migration was evaluated using a Boyden chamber assay. The in vivo effect of costunolide on AFP production was tested in NSG mice. Telomerase inhibition by costunolide and BIBR 1532 at 5 and 10 μM decreased AFP mRNA expression and protein secretion by HepG2/C3A cells. The same pattern was obtained with cells treated with hTERT siRNA. This treatment exhibited no apoptotic effect. The AFP mRNA expression and protein secretion by PLC/PRF/5 was decreased after treatment with BIBR1532 at 10 μM. In contrast, no effect was obtained for PLC/PRF/5 cells treated with costunolide at 5 or 10 μM. Inhibition of the PI3K/Akt/mTOR signaling pathway decreased the AFP concentration. In contrast, the MAPK/ERK pathway appeared to not be involved in HepG2/C3A cells, whereas ERK inhibition decreased the AFP concentration in PLC/PRF/5 cells. Modulation of the AFP concentration was also obtained after the inhibition or activation of PKC. Costunolide (30 mg/kg) significantly decreased the AFP serum concentration of NSG mice bearing HepG2/C3A cells. Both the inhibition of telomerase and the inhibition of the PI3K/Akt/mTOR signaling pathway decreased the AFP production of HepG2/C3A and PLC/PRF/5 cells, suggesting a relationship between telomerase and AFP expression through the PI3K/Akt/mTOR pathway.
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MESH Headings
- Aminobenzoates/pharmacology
- Animals
- Apoptosis/drug effects
- Carcinoma, Hepatocellular/drug therapy
- Carcinoma, Hepatocellular/metabolism
- Carcinoma, Hepatocellular/pathology
- Cell Line, Tumor
- Cell Movement/drug effects
- Enzyme Inhibitors/pharmacology
- Hep G2 Cells
- Humans
- Liver Neoplasms/drug therapy
- Liver Neoplasms/metabolism
- Liver Neoplasms/pathology
- Male
- Mice
- Mice, Inbred NOD
- Mice, SCID
- Naphthalenes/pharmacology
- Neoplasm Invasiveness/pathology
- Neoplasm Invasiveness/prevention & control
- Phosphatidylinositol 3-Kinases/metabolism
- Proto-Oncogene Proteins c-akt/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Neoplasm/genetics
- RNA, Neoplasm/metabolism
- RNA, Small Interfering/genetics
- Sesquiterpenes/pharmacology
- Signal Transduction/drug effects
- TOR Serine-Threonine Kinases/metabolism
- Telomerase/antagonists & inhibitors
- Telomerase/genetics
- Xenograft Model Antitumor Assays
- alpha-Fetoproteins/genetics
- alpha-Fetoproteins/metabolism
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Affiliation(s)
- Roula Tahtouh
- Cancer and Metabolism Laboratory, Faculty of Medicine, Saint-Joseph University, Beirut, Lebanon
| | - Anne-Sophie Azzi
- Cancer and Metabolism Laboratory, Faculty of Medicine, Saint-Joseph University, Beirut, Lebanon
| | - Nada Alaaeddine
- Regenerative Medicine Laboratory, Faculty of Medicine, Saint-Joseph University, Beirut, Lebanon
| | - Soulaima Chamat
- Faculty of Health Sciences, Lebanese University, Fanar, Lebanon
| | | | - Layal Wardi
- Cancer and Metabolism Laboratory, Faculty of Medicine, Saint-Joseph University, Beirut, Lebanon
| | - Issam Raad
- Department of Infectious Diseases, the University of Texas M. D. Anderson Cancer Center, Houston, Texas, United States of America
| | - Riad Sarkis
- Faculty of Medicine, Saint-Joseph University and Hotel-Dieu de France, Surgery Department, Beirut, Lebanon
| | | | - George Hilal
- Cancer and Metabolism Laboratory, Faculty of Medicine, Saint-Joseph University, Beirut, Lebanon
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Martí-Centelles R, Murga J, Falomir E, Carda M, Alberto Marco J. Inhibitory effect of cytotoxic nitrogen-containing heterocyclic stilbene analogues on VEGF protein secretion and VEGF, hTERT and c-Myc gene expression. MEDCHEMCOMM 2015. [DOI: 10.1039/c5md00197h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Twenty-one nitrogen-containing heterocyclic stilbenes were synthesized. Their cytotoxicity and effect on VEGF protein secretion as well asVEGF,hTERTandc-Mycgene expression were evaluated.
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Affiliation(s)
| | - Juan Murga
- Depart. de Química Inorgánica y Orgánica
- Univ. Jaume I
- E-12071 Castellón
- Spain
| | - Eva Falomir
- Depart. de Química Inorgánica y Orgánica
- Univ. Jaume I
- E-12071 Castellón
- Spain
| | - Miguel Carda
- Depart. de Química Inorgánica y Orgánica
- Univ. Jaume I
- E-12071 Castellón
- Spain
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60
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The effect of benzyl isothiocyanate and its computer-aided design derivants targeting alkylglycerone phosphate synthase on the inhibition of human glioma U87MG cell line. Tumour Biol 2014; 36:3499-509. [DOI: 10.1007/s13277-014-2986-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2014] [Accepted: 12/16/2014] [Indexed: 10/24/2022] Open
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61
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Kalathiya U, Padariya M, Baginski M. Molecular Modeling and Evaluation of Novel Dibenzopyrrole Derivatives as Telomerase Inhibitors and Potential Drug for Cancer Therapy. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2014; 11:1196-1207. [PMID: 26357055 DOI: 10.1109/tcbb.2014.2326860] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
During previous years, many studies on synthesis, as well as on anti-tumor, anti-inflammatory and anti-bacterial activities of the pyrazole derivatives have been described. Certain pyrazole derivatives exhibit important pharmacological activities and have proved to be useful template in drug research. Considering importance of pyrazole template, in current work the series of novel inhibitors were designed by replacing central ring of acridine with pyrazole ring. These heterocyclic compounds were proposed as a new potential base for telomerase inhibitors. Obtained dibenzopyrrole structure was used as a novel scaffold structure and extension of inhibitors was done by different functional groups. Docking of newly designed compounds in the telomerase active site (telomerase catalytic subunit TERT) was carried out. All dibenzopyrrole derivatives were evaluated by three docking programs: CDOCKER, Ligandfit docking (Scoring Functions) and AutoDock. Compound C_9g, C_9k and C_9l performed best in comparison to all designed inhibitors during the docking in all methods and in interaction analysis. Introduction of pyrazole and extension of dibenzopyrrole in compounds confirm that such compound may act as potential telomerase inhibitors.
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62
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Brosh RM, Cantor SB. Molecular and cellular functions of the FANCJ DNA helicase defective in cancer and in Fanconi anemia. Front Genet 2014; 5:372. [PMID: 25374583 PMCID: PMC4204437 DOI: 10.3389/fgene.2014.00372] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Accepted: 10/05/2014] [Indexed: 01/11/2023] Open
Abstract
The FANCJ DNA helicase is mutated in hereditary breast and ovarian cancer as well as the progressive bone marrow failure disorder Fanconi anemia (FA). FANCJ is linked to cancer suppression and DNA double strand break repair through its direct interaction with the hereditary breast cancer associated gene product, BRCA1. FANCJ also operates in the FA pathway of interstrand cross-link repair and contributes to homologous recombination. FANCJ collaborates with a number of DNA metabolizing proteins implicated in DNA damage detection and repair, and plays an important role in cell cycle checkpoint control. In addition to its role in the classical FA pathway, FANCJ is believed to have other functions that are centered on alleviating replication stress. FANCJ resolves G-quadruplex (G4) DNA structures that are known to affect cellular replication and transcription, and potentially play a role in the preservation and functionality of chromosomal structures such as telomeres. Recent studies suggest that FANCJ helps to maintain chromatin structure and preserve epigenetic stability by facilitating smooth progression of the replication fork when it encounters DNA damage or an alternate DNA structure such as a G4. Ongoing studies suggest a prominent but still not well-understood role of FANCJ in transcriptional regulation, chromosomal structure and function, and DNA damage repair to maintain genomic stability. This review will synthesize our current understanding of the molecular and cellular functions of FANCJ that are critical for chromosomal integrity.
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Affiliation(s)
- Robert M Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health Baltimore, MD, USA
| | - Sharon B Cantor
- Department of Cancer Biology, University of Massachusetts Medical School - UMASS Memorial Cancer Center Worcester, MA, USA
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63
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Optimization of a gene electrotransfer procedure for efficient intradermal immunization with an hTERT-based DNA vaccine in mice. MOLECULAR THERAPY-METHODS & CLINICAL DEVELOPMENT 2014; 1:14045. [PMID: 26015983 PMCID: PMC4362362 DOI: 10.1038/mtm.2014.45] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 06/30/2014] [Accepted: 07/11/2014] [Indexed: 12/30/2022]
Abstract
DNA vaccination consists in administering an antigen-encoding plasmid in order to trigger a specific immune response. This specific vaccine strategy is of particular interest to fight against various infectious diseases and cancer. Gene electrotransfer is the most efficient and safest non-viral gene transfer procedure and specific electrical parameters have been developed for several target tissues. Here, a gene electrotransfer protocol into the skin has been optimized in mice for efficient intradermal immunization against the well-known telomerase tumor antigen. First, the luciferase reporter gene was used to evaluate gene electrotransfer efficiency into the skin as a function of the electrical parameters and electrodes, either non-invasive or invasive. In a second time, these parameters were tested for their potency to generate specific cellular CD8 immune responses against telomerase epitopes. These CD8 T-cells were fully functional as they secreted IFNγ and were endowed with specific cytotoxic activity towards target cells. This simple and optimized procedure for efficient gene electrotransfer into the skin using the telomerase antigen is to be used in cancer patients for the phase 1 clinical evaluation of a therapeutic cancer DNA vaccine called INVAC-1.
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64
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Jhunjhunwala S, Jiang Z, Stawiski EW, Gnad F, Liu J, Mayba O, Du P, Diao J, Johnson S, Wong KF, Gao Z, Li Y, Wu TD, Kapadia SB, Modrusan Z, French DM, Luk JM, Seshagiri S, Zhang Z. Diverse modes of genomic alteration in hepatocellular carcinoma. Genome Biol 2014; 15:436. [PMID: 25159915 PMCID: PMC4189592 DOI: 10.1186/s13059-014-0436-9] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 08/11/2014] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Hepatocellular carcinoma (HCC) is a heterogeneous disease with high mortality rate. Recent genomic studies have identified TP53, AXIN1, and CTNNB1 as the most frequently mutated genes. Lower frequency mutations have been reported in ARID1A, ARID2 and JAK1. In addition, hepatitis B virus (HBV) integrations into the human genome have been associated with HCC. RESULTS Here, we deep-sequence 42 HCC patients with a combination of whole genome, exome and transcriptome sequencing to identify the mutational landscape of HCC using a reasonably large discovery cohort. We find frequent mutations in TP53, CTNNB1 and AXIN1, and rare but likely functional mutations in BAP1 and IDH1. Besides frequent hepatitis B virus integrations at TERT, we identify translocations at the boundaries of TERT. A novel deletion is identified in CTNNB1 in a region that is heavily mutated in multiple cancers. We also find multiple high-allelic frequency mutations in the extracellular matrix protein LAMA2. Lower expression levels of LAMA2 correlate with a proliferative signature, and predict poor survival and higher chance of cancer recurrence in HCC patients, suggesting an important role of the extracellular matrix and cell adhesion in tumor progression of a subgroup of HCC patients. CONCLUSIONS The heterogeneous disease of HCC features diverse modes of genomic alteration. In addition to common point mutations, structural variations and methylation changes, there are several virus-associated changes, including gene disruption or activation, formation of chimeric viral-human transcripts, and DNA copy number changes. Such a multitude of genomic events likely contributes to the heterogeneous nature of HCC.
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Affiliation(s)
- Suchit Jhunjhunwala
- />Department of Bioinformatics and Computational Biology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Zhaoshi Jiang
- />Department of Bioinformatics and Computational Biology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Eric W Stawiski
- />Department of Bioinformatics and Computational Biology, Genentech Inc., South San Francisco, CA 94080 USA
- />Department of Molecular Biology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Florian Gnad
- />Department of Bioinformatics and Computational Biology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Jinfeng Liu
- />Department of Bioinformatics and Computational Biology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Oleg Mayba
- />Department of Bioinformatics and Computational Biology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Pan Du
- />Department of Bioinformatics and Computational Biology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Jingyu Diao
- />Department of Infectious diseases, Genentech Inc., South San Francisco, CA 94080 USA
| | - Stephanie Johnson
- />Department of Pathology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Kwong-Fai Wong
- />Department of Surgery, University of Hong Kong, Pokfulam, Hong Kong
| | - Zhibo Gao
- />BGI-Shenzhen, Shenzhen, 518083 China
| | | | - Thomas D Wu
- />Department of Bioinformatics and Computational Biology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Sharookh B Kapadia
- />Department of Infectious diseases, Genentech Inc., South San Francisco, CA 94080 USA
| | - Zora Modrusan
- />Department of Molecular Biology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Dorothy M French
- />Department of Pathology, Genentech Inc., South San Francisco, CA 94080 USA
| | - John M Luk
- />Department of Surgery, University of Hong Kong, Pokfulam, Hong Kong
- />Department of Pharmacology, National University of Singapore, Singapore, 117597 Singapore
- />Institute of Molecular and Cell Biology, A*STAR, 61 Biopolis Drive, Singapore, 138673 Singapore
| | - Somasekar Seshagiri
- />Department of Molecular Biology, Genentech Inc., South San Francisco, CA 94080 USA
| | - Zemin Zhang
- />Department of Bioinformatics and Computational Biology, Genentech Inc., South San Francisco, CA 94080 USA
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65
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Vinagre J, Pinto V, Celestino R, Reis M, Pópulo H, Boaventura P, Melo M, Catarino T, Lima J, Lopes JM, Máximo V, Sobrinho-Simões M, Soares P. Telomerase promoter mutations in cancer: an emerging molecular biomarker? Virchows Arch 2014; 465:119-33. [DOI: 10.1007/s00428-014-1608-4] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2014] [Revised: 05/19/2014] [Accepted: 06/16/2014] [Indexed: 12/16/2022]
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Cheng YB, Guo LP, Yao P, Ning XY, Aerken G, Fang DC. Telomerase and hTERT: Can they serve as markers for gastric cancer diagnosis? World J Gastroenterol 2014; 20:6615-6619. [PMID: 24914385 PMCID: PMC4047349 DOI: 10.3748/wjg.v20.i21.6615] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 02/15/2014] [Accepted: 03/05/2014] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate telomerase activity and human telomerase reverse transcriptase (hTERT) expression in normal human gastric mucosal epithelial cells (nhGMECs) and fibroblasts (nhGMFs).
METHODS: nhGMECs and nhGMFs were isolated and cultured from specimens obtained during routine surgery for bleeding peptic ulcer. Telomerase activity in nhGMFs, nhGMECs, and the tumor cell lines BGC-823, SGC-7901 and MKN-28 cells was analyzed using the telomeric repeat amplification protocol assay. hTERT protein was determined in nhGMECs, nhGMFs, BGC-823, SGC-7901 and MKN-28 cells by indirect immunofluorescence.
RESULTS: A similar level of telomerase activity was observed in nhGMECs, nhGMFs and BGC-823, SGC-7901, MKN-28 cell lines. Positive hTERT immunostaining was detected in nhGMECs, nhGMFs, BGC-823, SGC-7901 and MKN-28 cell lines.
CONCLUSION: The use of telomerase or hTERT as diagnostic markers for gastric cancer may require further studies.
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Mohit E, Hashemi A, Allahyari M. Breast cancer immunotherapy: monoclonal antibodies and peptide-based vaccines. Expert Rev Clin Immunol 2014; 10:927-61. [DOI: 10.1586/1744666x.2014.916211] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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68
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Qin Y, Guo H, Tang B, Yang SM. The non-reverse transcriptase activity of the human telomerase reverse transcriptase promotes tumor progression (review). Int J Oncol 2014; 45:525-31. [PMID: 24888567 DOI: 10.3892/ijo.2014.2470] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 04/17/2014] [Indexed: 11/05/2022] Open
Abstract
In human cancer, high expression of telomerase is correlated with tumor aggressiveness and metastatic potential. Human telomerase reverse transcriptase (hTERT), which regulates telomere length, can promote tumor development. Most research on hTERT has been focused on its crucial function of telomere maintenance. However, there are many phenomena that cannot be explained by its reverse transcriptase activity. Accumulating evidence suggests that hTERT has functions independent of its protective function at the telomere ends, such as increasing the anti-apoptotic capacity of cells, enhancing DNA repair, maintaining stem cells and regulating gene expression. This review will provide an update on the non-reverse transcriptase activity of hTERT and its contribution to tumor formation, metastasis and cancer stem cell maintenance. Repression of the non-reverse transcriptase activity of hTERT may be a new strategy for tumor therapy.
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Affiliation(s)
- Yong Qin
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, P.R. China
| | - Hong Guo
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, P.R. China
| | - Bo Tang
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, P.R. China
| | - Shi-Ming Yang
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, P.R. China
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69
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Gardano L. Using PCR coupled to PAGE for detection and semiquantitative evaluation of telomerase activity. Methods Mol Biol 2014; 1054:283-93. [PMID: 23913300 DOI: 10.1007/978-1-62703-565-1_19] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Telomerase is the enzyme that extends the chromosome ends, thereby contributing to eukaryotic cell genome stability. Telomerase is expressed in the majority of cells that have an unlimited proliferation such as stem cells and cancer cells. The increased interest in telomerase in cancer research, challenged by the low cellular abundance of the enzyme, has led to the development of a reliable and at the same time very sensitive approach to detect telomerase activity. The telomeric repeat amplification protocol (TRAP) represents an easy and rapid method for detection of telomerase activity in cells. A non-telomeric TS primer is extended by telomerase in the first step followed by the PCR amplification of the products. The PCR step renders this protocol very sensitive to detect telomerase activity at the single cell level making it compatible with the analysis of tumor samples. When run on a polyacrylamide gel, the PCR product is a characteristic ladder of bands due to the repetitive nature of telomeric DNA sequence. The densitometric analysis of the ladder allows the TRAP assay to be used for comparative quantification of telomerase activity in different samples.
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70
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Progress in structural studies of telomerase. Curr Opin Struct Biol 2014; 24:115-24. [PMID: 24508601 DOI: 10.1016/j.sbi.2014.01.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 01/01/2014] [Accepted: 01/08/2014] [Indexed: 02/01/2023]
Abstract
Telomerase is the ribonucleoprotein (RNP) reverse transcriptase responsible for synthesizing the 3' ends of linear chromosomes. It plays critical roles in tumorigenesis, cellular aging, and stem cell renewal. The past two years have seen exciting progress in determining telomerase holoenzyme architecture and the structural basis of telomerase activity. Notably, the first electron microscopy structures of telomerase were reported, of the Tetrahymena thermophila telomerase holoenzyme and a human telomerase dimer. In addition to new structures of TERT and TER domains, the first structures of telomerase protein domains beyond TERT, and their complexes with TER or telomeric single-stranded DNA, were reported. Together these studies provide the first glimpse into the organization of the proteins and RNA in the telomerase RNP.
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71
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Shim G, Ricoul M, Hempel WM, Azzam EI, Sabatier L. Crosstalk between telomere maintenance and radiation effects: A key player in the process of radiation-induced carcinogenesis. MUTATION RESEARCH. REVIEWS IN MUTATION RESEARCH 2014; 760:S1383-5742(14)00002-7. [PMID: 24486376 PMCID: PMC4119099 DOI: 10.1016/j.mrrev.2014.01.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 01/14/2014] [Accepted: 01/22/2014] [Indexed: 02/06/2023]
Abstract
It is well established that ionizing radiation induces chromosomal damage, both following direct radiation exposure and via non-targeted (bystander) effects, activating DNA damage repair pathways, of which the proteins are closely linked to telomeric proteins and telomere maintenance. Long-term propagation of this radiation-induced chromosomal damage during cell proliferation results in chromosomal instability. Many studies have shown the link between radiation exposure and radiation-induced changes in oxidative stress and DNA damage repair in both targeted and non-targeted cells. However, the effect of these factors on telomeres, long established as guardians of the genome, still remains to be clarified. In this review, we will focus on what is known about how telomeres are affected by exposure to low- and high-LET ionizing radiation and during proliferation, and will discuss how telomeres may be a key player in the process of radiation-induced carcinogenesis.
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72
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Torijano-Gutiérrez S, Díaz-Oltra S, Falomir E, Murga J, Carda M, Marco JA. Synthesis of combretastatin A-4 O-alkyl derivatives and evaluation of their cytotoxic, antiangiogenic and antitelomerase activity. Bioorg Med Chem 2013; 21:7267-74. [DOI: 10.1016/j.bmc.2013.09.064] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Revised: 09/22/2013] [Accepted: 09/26/2013] [Indexed: 11/26/2022]
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73
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Mohammad RY, Somayyeh G, Gholamreza H, Majid M, Yousef R. Diosgenin Inhibits hTERT Gene Expression in the A549 Lung Cancer Cell Line. Asian Pac J Cancer Prev 2013; 14:6945-8. [DOI: 10.7314/apjcp.2013.14.11.6945] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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74
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Cobrinik D, Ostrovnaya I, Hassimi M, Tickoo SK, Cheung IY, Cheung NKV. Recurrent pre-existing and acquired DNA copy number alterations, including focal TERT gains, in neuroblastoma central nervous system metastases. Genes Chromosomes Cancer 2013; 52:1150-66. [PMID: 24123354 DOI: 10.1002/gcc.22110] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 08/14/2013] [Indexed: 12/13/2022] Open
Abstract
Stage 4 neuroblastomas have a high rate of local and metastatic relapse and associated disease mortality. The central nervous system (CNS) is currently one of the most common isolated relapse sites, yet the genomic alterations that contribute to these metastases are unknown. This study sought to identify recurrent DNA copy number alterations (CNAs) and target genes relating to neuroblastoma CNS metastases by studying 19 pre-CNS primary tumors and 27 CNS metastases, including 12 matched pairs. SNP microarray analyses revealed that MYCN amplified (MYCNA) tumors had recurrent CNAs different from non-MYCNA cohorts. Several CNAs known to be prevalent among primary neuroblastomas occurred more frequently in CNS metastases, including 4p-, 7q+, 12q+, and 19q- in non-MYCNA metastases, and 9p- and 14q- irrespective of MYCNA status. In addition, novel CNS metastases-related CNAs included 18q22.1 gains in non-MYCNA pre-CNS primaries and 5p15.33 gains and 15q26.1→tel losses in non-MYCNA CNS metastases. Based on minimal common regions, gene expression, and biological properties, TERT (5p), NR2F2 (15q), ALDH1A3 (15q), CDKN2A (9p), and possibly CDH7 and CDH19 (18q) were candidate genes associated with the CNS metastatic process. Notably, the 5p15 minimal common region contained only TERT, and non-MYCNA CNS metastases with focal 5p15 gains had increased TERT expression, similar to MYCNA tumors. These findings suggest that a specific genomic lesion (18q22.1 gain) predisposes to CNS metastases and that distinct lesions are recurrently acquired during metastatic progression. Among the acquired lesions, increased TERT copy number and expression appears likely to function in lieu of MYCNA to promote CNS metastasis.
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Affiliation(s)
- David Cobrinik
- Department of Pediatrics, Memorial Sloan-Kettering Cancer Center, New York, NY, 10065
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75
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Acacetin and chrysin, two polyphenolic compounds, alleviate telomeric position effect in human cells. MOLECULAR THERAPY. NUCLEIC ACIDS 2013; 2:e116. [PMID: 23962900 PMCID: PMC3759739 DOI: 10.1038/mtna.2013.42] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Accepted: 06/04/2013] [Indexed: 12/28/2022]
Abstract
We took advantage of the ability of human telomeres to silence neighboring genes (telomere position effect or TPE) to design a high-throughput screening assay for drugs altering telomeres. We identified, for the first time, that two dietary flavones, acacetin and chrysin, are able to specifically alleviate TPE in human cells. We further investigated their influence on telomere integrity and showed that both drugs drastically deprotect telomeres against DNA damage response. However, telomere deprotection triggered by shelterin dysfunction does not affect TPE, indicating that acacetin and chrysin target several functions of telomeres. These results show that TPE-based screening assays represent valuable methods to discover new compounds targeting telomeres.
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76
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Lu H, Lei Z, Lu Z, Lu Q, Lu C, Chen W, Wang C, Tang Q, Kong Q. Silencing tankyrase and telomerase promotes A549 human lung adenocarcinoma cell apoptosis and inhibits proliferation. Oncol Rep 2013; 30:1745-52. [PMID: 23933993 DOI: 10.3892/or.2013.2665] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 07/30/2013] [Indexed: 11/05/2022] Open
Abstract
Telomeres are the end structures of chromosomes in mammalian cells; they play a pivotal role in maintaining the stability of the chromosome and become shorter with each cell division. However, several types of tumor cells express telomerase in very high levels to overcome this crisis and achieve the ability to proliferate endlessly. The telomerase inhibitors can partly inhibit tumor cell proliferation and promote apoptosis, but their roles are only limited. Tankyrase is a poly(ADP-ribose) polymerase which has synergistic effect on telomerase, and is expressed in lung cancer cells in high levels. In the present study, antisense oligonucleotides of telomerase (ashTERT) and tankyrase (asTANKS) were used as specific inhibitors to silence the expression of target genes in A549 human lung adenocarcinoma cells by transfection. The results showed that ashTERT and asTANKS suppressed the expression of telomerase and tankyrase significantly; both inhibited the activity of telomerase and the combination group achieved better effect, but only ashTERT shortened the length of telomeres, asTANKS did not. Further studies showed that ashTERT and asTANKS-promoted A549 apoptosis was not mediated by downregulation of the expression of the anti-apoptotic gene BCL-2 or upregulation of the expression of the pro-apoptotic gene BAX, but by adjusting the two isoforms proportion of myeloid cell leukemia-1 (MCL-1) which can interact with tankyrase directly. MCL-1short (MCL-1S), a pro-apoptotic gene, increased more than MCL-1Long (MCL-1L) which is an anti-apoptotic gene, leading to A549 cell apoptosis and a similar result was obtained in nude mice in vivo. The present study suggests that combination of the inhibitors of telomerase and tankyrase can be used as a strategy for the treatment of lung cancer in humans.
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Affiliation(s)
- Hongda Lu
- Department of Oncology, the Central Hospital of Wuhan, Wuhan, Hubei, P.R. China
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77
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Telomerase: central regulator of all of the hallmarks of cancer. Trends Biochem Sci 2013; 38:426-34. [PMID: 23932019 DOI: 10.1016/j.tibs.2013.07.001] [Citation(s) in RCA: 180] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 06/26/2013] [Accepted: 07/01/2013] [Indexed: 12/13/2022]
Abstract
The hallmarks of cancer described by Hanahan and Weinberg are properties that cancer cells must possess for successful transformation. It is believed that each of these hallmarks is independently driven. Although elongation of telomeres is thought to be the prime function of reactivated telomerase reverse transcriptase, this activity does not account for all its effects, such as increasing cell proliferation, resistance to apoptosis, and invasion. Recent studies suggest that the telomerase subunit telomerase reverse transcriptase (TERT) has novel molecular functions including transcriptional regulation and metabolic reprogramming. We summarize these functions and discuss how they could directly regulate the various hallmarks of cancer. Finally, we suggest that therapeutics targeting noncanonical telomerase functions may work better than those that target its role in telomere extension.
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78
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Abstract
Helicases have major roles in genome maintenance by unwinding structured nucleic acids. Their prominence is marked by various cancers and genetic disorders that are linked to helicase defects. Although considerable effort has been made to understand the functions of DNA helicases that are important for genomic stability and cellular homeostasis, the complexity of the DNA damage response leaves us with unanswered questions regarding how helicase-dependent DNA repair pathways are regulated and coordinated with cell cycle checkpoints. Further studies may open the door to targeting helicases in order to improve cancer treatments based on DNA-damaging chemotherapy or radiation.
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Affiliation(s)
- Robert M Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, NIH Biomedical Research Center, 251 Bayview Boulevard, Baltimore, Maryland 21224, USA.
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79
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The hallmarks of cancer and the radiation oncologist: updating the 5Rs of radiobiology. Clin Oncol (R Coll Radiol) 2013; 25:569-77. [PMID: 23850153 DOI: 10.1016/j.clon.2013.06.009] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 05/06/2013] [Accepted: 06/14/2013] [Indexed: 12/17/2022]
Abstract
A comprehensive, mechanistic understanding of radiobiological phenomena that can be integrated within the broader context of cancer biology offers the prospect of transforming clinical practice in radiation oncology. In this review, we revisit the six established biological hallmarks of cancer and examine how they have provided insights into novel therapeutic strategies. In addition, we discuss the potential of two emerging hallmarks to continue to expand our understanding beyond the narrow confines of the traditional 5Rs of radiobiology.
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80
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Yu EY, Kojic M, Holloman WK, Lue NF. Brh2 and Rad51 promote telomere maintenance in Ustilago maydis, a new model system of DNA repair proteins at telomeres. DNA Repair (Amst) 2013; 12:472-9. [PMID: 23726221 DOI: 10.1016/j.dnarep.2013.04.027] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Revised: 04/19/2013] [Accepted: 04/22/2013] [Indexed: 11/28/2022]
Abstract
Recent studies implicate a number of DNA repair proteins in mammalian telomere maintenance. However, because several key repair proteins in mammals are missing from the well-studied budding and fission yeast, their roles at telomeres cannot be modeled in standard fungi. In this report, we explored the dimorphic fungus Ustilago maydis as an alternative model for telomere research. This fungus, which belongs to the phylum Basidiomycota, has a telomere repeat unit that is identical to the mammalian repeat, as well as a constellation of DNA repair proteins that more closely mimic the mammalian collection. We showed that the two core components of homology-directed repair (HDR) in U. maydis, namely Brh2 and Rad51, both promote telomere maintenance in telomerase positive cells, just like in mammals. In addition, we found that Brh2 is localized to telomeres in vivo, suggesting that it acts directly at chromosome ends. We surveyed a series of mutants with DNA repair defects, and found many of them to have short telomeres. Our results indicate that factors involved in DNA repair are probably also needed for optimal telomere maintenance in U. maydis, and that this fungus is a useful alternative model system for telomere research.
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Affiliation(s)
- Eun Young Yu
- Department of Microbiology & Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10065, USA
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81
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Ishikawa F. Portrait of replication stress viewed from telomeres. Cancer Sci 2013; 104:790-4. [PMID: 23557232 PMCID: PMC3881512 DOI: 10.1111/cas.12165] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 03/16/2013] [Accepted: 03/19/2013] [Indexed: 01/23/2023] Open
Abstract
Genetic instability is the driving force of the malignant progression of cancer cells. Recently, replication stress has attracted much attention as a source of genetic instability that gives rise to an accumulation of mutations during the lifespan of individuals. However, the molecular details of the process are not fully understood. Here, recent progress in understanding how genetic alterations accumulate at telomeres will be reviewed. In particular, two aspects of telomere replication will be discussed in this context, covering conventional semi-conservative replication, and DNA synthesis by telomerase plus the C-strand fill-in reactions. Although these processes are seemingly telomere-specific, I will emphasize the possibility that the molecular understanding of the telomere events may shed light on genetic instability at other genetic loci in general.
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Affiliation(s)
- Fuyuki Ishikawa
- Graduate School of Biostudies, Kyoto University, Kyoto, Japan.
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82
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Holysz H, Lipinska N, Paszel-Jaworska A, Rubis B. Telomerase as a useful target in cancer fighting-the breast cancer case. Tumour Biol 2013; 34:1371-80. [PMID: 23558965 PMCID: PMC3661921 DOI: 10.1007/s13277-013-0757-4] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 03/20/2013] [Indexed: 12/17/2022] Open
Abstract
Telomerase was initially considered as a relevant factor distinguishing cancer from normal cells. During detailed studies, it appeared that its expression and activity is not only limited to cancer cells however, but in this particular cells, the telomerase is much more abundant. Thus, it has become a very promising target for an anticancer therapy. It was revealed in many studies that regulation of telomerase is a multifactorial process in mammalian cells, involving regulation of expression of telomerase subunits coding genes, post-translational protein–protein interactions, and protein phosphorylation. Numerous proto-oncogenes and tumor suppressor genes are engaged in this mechanism, and the complexity of telomerase control is studied in the context of tumor development as well as aging. Additionally, since numerous studies reveal a correlation between short telomeres and increased genome instability or cell mortality, the telomerase control appears to be one of the crucial factors to study in order to improve the cancer diagnostics and therapy or prevention. Interestingly, almost 100 % of adenocarcinoma, including breast cancer cells, expresses telomerase which makes it a good target for telomerase-related therapy. Additionally, telomerase is also supposed to be associated with drug resistance. Thus, targeting the enzyme might result in attenuation of this phenomenon. Moreover, since stem cells existence was reported, it must be considered whether targeting telomerase can bring some serious side effects and result in stem cells viability or their regenerative potential decrease. Thus, we review some molecular mechanisms engaged in therapy based on targeting telomerase in breast cancer cells.
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Affiliation(s)
- Hanna Holysz
- Department of Clinical Chemistry and Molecular Diagnostics, Poznan University of Medical Sciences, ul. Przybyszewskiego 49, 60-355, Poznan, Poland
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83
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Vummidi BR, Alzeer J, Luedtke NW. Fluorescent Probes for G-Quadruplex Structures. Chembiochem 2013; 14:540-58. [DOI: 10.1002/cbic.201200612] [Citation(s) in RCA: 197] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Indexed: 12/19/2022]
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84
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Hasei J, Sasaki T, Tazawa H, Osaki S, Yamakawa Y, Kunisada T, Yoshida A, Hashimoto Y, Onishi T, Uno F, Kagawa S, Urata Y, Ozaki T, Fujiwara T. Dual programmed cell death pathways induced by p53 transactivation overcome resistance to oncolytic adenovirus in human osteosarcoma cells. Mol Cancer Ther 2013; 12:314-25. [PMID: 23315976 DOI: 10.1158/1535-7163.mct-12-0869] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Tumor suppressor p53 is a multifunctional transcription factor that regulates diverse cell fates, including apoptosis and autophagy in tumor biology. p53 overexpression enhances the antitumor activity of oncolytic adenoviruses; however, the molecular mechanism of this occurrence remains unclear. We previously developed a tumor-specific replication-competent oncolytic adenovirus, OBP-301, that kills human osteosarcoma cells, but some human osteosarcoma cells were OBP-301-resistant. In this study, we investigated the antitumor activity of a p53-expressing oncolytic adenovirus, OBP-702, and the molecular mechanism of the p53-mediated cell death pathway in OBP-301-resistant human osteosarcoma cells. The cytopathic activity of OBP-702 was examined in OBP-301-sensitive (U2OS and HOS) and OBP-301-resistant (SaOS-2 and MNNG/HOS) human osteosarcoma cells. The molecular mechanism in the OBP-702-mediated induction of two cell death pathways, apoptosis and autophagy, was investigated in OBP-301-resistant osteosarcoma cells. The antitumor effect of OBP-702 was further assessed using an orthotopic OBP-301-resistant MNNG/HOS osteosarcoma xenograft tumor model. OBP-702 suppressed the viability of OBP-301-sensitive and -resistant osteosarcoma cells more efficiently than OBP-301 or a replication-deficient p53-expressing adenovirus (Ad-p53). OBP-702 induced more profound apoptosis and autophagy when compared with OBP-301 or Ad-p53. E1A-mediated miR-93/106b upregulation induced p21 suppression, leading to p53-mediated apoptosis and autophagy in OBP-702-infected cells. p53 overexpression enhanced adenovirus-mediated autophagy through activation of damage-regulated autophagy modulator (DRAM). Moreover, OBP-702 suppressed tumor growth in an orthotopic OBP-301-resistant MNNG/HOS xenograft tumor model. These results suggest that OBP-702-mediated p53 transactivation is a promising antitumor strategy to induce dual apoptotic and autophagic cell death pathways via regulation of miRNA and DRAM in human osteosarcoma cells.
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Affiliation(s)
- Joe Hasei
- Department of Orthopaedic Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
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85
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Hung NA, Hsia H, Royds JA, Slatter TL. Telomere Maintenance Mechanisms: Prognostic and Therapeutic Implications for the Pathologist and Oncologist. ACTA ACUST UNITED AC 2013. [DOI: 10.4236/ojpathology.2013.31003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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86
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Taka T, Huang L, Wongnoppavich A, Tam-Chang SW, Lee TR, Tuntiwechapikul W. Telomere shortening and cell senescence induced by perylene derivatives in A549 human lung cancer cells. Bioorg Med Chem 2012; 21:883-90. [PMID: 23321015 DOI: 10.1016/j.bmc.2012.12.020] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Revised: 12/08/2012] [Accepted: 12/10/2012] [Indexed: 01/29/2023]
Abstract
Cancer cells evade replicative senescence by re-expressing telomerase, which maintains telomere length and hence chromosomal integrity. Telomerase inhibition would lead cancer cells to senesce and therefore prevent cancer cells from growing indefinitely. G-quadruplex ligands can attenuate telomerase activity by inducing G-quadruplex formation at the 3'-overhang of telomere and at the human telomerase reverse transcriptase (hTERT) promoter; the former prevents telomerase from accessing the telomere, and the latter acts as a transcriptional silencer. The present investigation found that perylene derivatives PM2 and PIPER induced G-quadruplex formation from both telomeric DNA and the hTERT promoter region in vitro. Further, TRAP assay showed that these compounds inhibited telomerase in a dose-dependent manner. When A549 human lung cancer cells were treated with these compounds, hTERT expression was down-regulated. Moreover, the crude protein extract from these treated cells exhibited less telomerase activity. In the long-term treatment of A549 lung cancer cells with sub-cytotoxic dose of these perylenes, telomere shortening, reduction of cell proliferation and tumorigenicity, and cell senescence were observed. The results of this study indicate that perylene derivatives warrant further consideration as effective agents for cancer therapy.
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Affiliation(s)
- Thanachai Taka
- Department of Biochemistry, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
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87
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Riffell JL, Lord CJ, Ashworth A. Tankyrase-targeted therapeutics: expanding opportunities in the PARP family. Nat Rev Drug Discov 2012; 11:923-36. [PMID: 23197039 DOI: 10.1038/nrd3868] [Citation(s) in RCA: 217] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The poly(ADP-ribose) polymerase (PARP) protein superfamily has wide-ranging roles in cellular processes such as DNA repair and WNT signalling. Efforts to pharmacologically target PARP enzymes have largely focused on PARP1 and the closely related PARP2, but recent work highlighting the role of another family member, tankyrase 1 (TANK1; also known as PARP5A and ARTD5), in the control of WNT signalling has fuelled interest in the development of additional inhibitors to target this enzyme class. Tankyrase function is also implicated in other processes such as the regulation of telomere length, lung fibrogenesis and myelination, suggesting that tankyrase inhibitors could have broad clinical utility. Here, we discuss the biology of tankyrases and the discovery of tankyrase-specific inhibitors. We also consider the challenges that lie ahead for the clinical development of PARP family inhibitors in general.
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Affiliation(s)
- Jenna L Riffell
- The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, Fulham Road, London SW3 6JB, UK
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88
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Abstract
There has been mounting evidence of a causal role for telomere dysfunction in a number of degenerative disorders. Their manifestations encompass common disease states such as idiopathic pulmonary fibrosis and bone marrow failure. Although these disorders seem to be clinically diverse, collectively they comprise a single syndrome spectrum defined by the short telomere defect. Here we review the manifestations and unique genetics of telomere syndromes. We also discuss their underlying molecular mechanisms and significance for understanding common age-related disease processes.
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Affiliation(s)
- Mary Armanios
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
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89
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Altschuler SE, Croy JE, Wuttke DS. A small molecule inhibitor of Pot1 binding to telomeric DNA. Biochemistry 2012; 51:7833-45. [PMID: 22978652 DOI: 10.1021/bi300365k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Chromosome ends are complex structures, consisting of repetitive DNA sequence terminating in an ssDNA overhang with many associated proteins. Because alteration of the regulation of these ends is a hallmark of cancer, telomeres and telomere maintenance have been prime drug targets. The universally conserved ssDNA overhang is sequence-specifically bound and regulated by Pot1 (protection of telomeres 1), and perturbation of Pot1 function has deleterious effects for proliferating cells. The specificity of the Pot1/ssDNA interaction and the key involvement of this protein in telomere maintenance have suggested directed inhibition of Pot1/ssDNA binding as an efficient means of disrupting telomere function. To explore this idea, we developed a high-throughput time-resolved fluorescence resonance energy transfer (TR-FRET) screen for inhibitors of Pot1/ssDNA interaction. We conducted this screen with the DNA-binding subdomain of Schizosaccharomyces pombe Pot1 (Pot1pN), which confers the vast majority of Pot1 sequence-specificity and is highly similar to the first domain of human Pot1 (hPOT1). Screening a library of ∼20 000 compounds yielded a single inhibitor, which we found interacted tightly with sub-micromolar affinity. Furthermore, this compound, subsequently identified as the bis-azo dye Congo red (CR), was able to competitively inhibit hPOT1 binding to telomeric DNA. Isothermal titration calorimetry and NMR chemical shift analysis suggest that CR interacts specifically with the ssDNA-binding cleft of Pot1, and that alteration of this surface disrupts CR binding. The identification of a specific inhibitor of ssDNA interaction establishes a new pathway for targeted telomere disruption.
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Affiliation(s)
- Sarah E Altschuler
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA
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90
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Abstract
There has been mounting evidence of a causal role for telomere dysfunction in a number of degenerative disorders. Their manifestations encompass common disease states such as idiopathic pulmonary fibrosis and bone marrow failure. Although these disorders seem to be clinically diverse, collectively they comprise a single syndrome spectrum defined by the short telomere defect. Here we review the manifestations and unique genetics of telomere syndromes. We also discuss their underlying molecular mechanisms and significance for understanding common age-related disease processes.
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91
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Abstract
There has been mounting evidence of a causal role for telomere dysfunction in a number of degenerative disorders. Their manifestations encompass common disease states such as idiopathic pulmonary fibrosis and bone marrow failure. Although these disorders seem to be clinically diverse, collectively they comprise a single syndrome spectrum defined by the short telomere defect. Here we review the manifestations and unique genetics of telomere syndromes. We also discuss their underlying molecular mechanisms and significance for understanding common age-related disease processes.
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Affiliation(s)
- Mary Armanios
- Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
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92
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Synthesis and evaluation of 10-(3,5-dimethoxy)benzyl-9(10H)-acridone derivatives as selective telomeric G-quadruplex DNA ligands. Tetrahedron 2012. [DOI: 10.1016/j.tet.2012.07.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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93
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Greider CW. Molecular biology. Wnt regulates TERT--putting the horse before the cart. Science 2012; 336:1519-20. [PMID: 22723405 DOI: 10.1126/science.1223785] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Carol W Greider
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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94
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Essaghir A, Demoulin JB. A minimal connected network of transcription factors regulated in human tumors and its application to the quest for universal cancer biomarkers. PLoS One 2012; 7:e39666. [PMID: 22761861 PMCID: PMC3382591 DOI: 10.1371/journal.pone.0039666] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Accepted: 05/25/2012] [Indexed: 12/19/2022] Open
Abstract
A universal cancer biomarker candidate for diagnosis is supposed to distinguish, within a broad range of tumors, between healthy and diseased patients. Recently published studies have explored the universal usefulness of some biomarkers in human tumors. In this study, we present an integrative approach to search for potential common cancer biomarkers. Using the TFactS web-tool with a catalogue of experimentally established gene regulations, we could predict transcription factors (TFs) regulated in 305 different human cancer cell lines covering a large panel of tumor types. We also identified chromosomal regions having significant copy number variation (CNV) in these cell lines. Within the scope of TFactS catalogue, 88 TFs whose activity status were explained by their gene expressions and CNVs were identified. Their minimal connected network (MCN) of protein-protein interactions forms a significant module within the human curated TF proteome. Functional analysis of the proteins included in this MCN revealed enrichment in cancer pathways as well as inflammation. The ten most central proteins in MCN are TFs that trans-regulate 157 known genes encoding secreted and transmembrane proteins. In publicly available collections of gene expression data from 8,525 patient tissues, 86 genes were differentially regulated in cancer compared to inflammatory diseases and controls. From TCGA cancer gene expression data sets, 50 genes were significantly associated to patient survival in at least one tumor type. Enrichment analysis shows that these genes mechanistically interact in common cancer pathways. Among these cancer biomarker candidates, TFRC, MET and VEGFA are commonly amplified genes in tumors and their encoded proteins stained positive in more than 80% of malignancies from public databases. They are linked to angiogenesis and hypoxia, which are common in cancer. They could be interesting for further investigations in cancer diagnostic strategies.
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Affiliation(s)
- Ahmed Essaghir
- de Duve institute, Université Catholique de Louvain, Brussels, Belgium.
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95
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Stewart JA, Chaiken MF, Wang F, Price CM. Maintaining the end: roles of telomere proteins in end-protection, telomere replication and length regulation. Mutat Res 2012; 730:12-9. [PMID: 21945241 PMCID: PMC3256267 DOI: 10.1016/j.mrfmmm.2011.08.011] [Citation(s) in RCA: 140] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 08/15/2011] [Accepted: 08/17/2011] [Indexed: 11/16/2022]
Abstract
Chromosome end protection is essential to protect genome integrity. Telomeres, tracts of repetitive DNA sequence and associated proteins located at the chromosomal terminus, serve to safeguard the ends from degradation and unwanted double strand break repair. Due to the essential nature of telomeres in protecting the genome, a number of unique proteins have evolved to ensure that telomere length and structure are preserved. The inability to properly maintain telomeres can lead to diseases such as dyskeratosis congenita, pulmonary fibrosis and cancer. In this review, we will discuss the known functions of mammalian telomere-associated proteins, their role in telomere replication and length regulation and how these processes relate to genome instability and human disease.
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Affiliation(s)
- Jason A. Stewart
- Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, Ohio 45267, USA
| | - Mary F. Chaiken
- Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, Ohio 45267, USA
| | - Feng Wang
- Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, Ohio 45267, USA
| | - Carolyn M. Price
- Department of Cancer and Cell Biology, University of Cincinnati, Cincinnati, Ohio 45267, USA
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96
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Durant ST. Telomerase-independent paths to immortality in predictable cancer subtypes. J Cancer 2012; 3:67-82. [PMID: 22315652 PMCID: PMC3273709 DOI: 10.7150/jca.3965] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 01/28/2012] [Indexed: 01/17/2023] Open
Abstract
The vast majority of cancers commandeer the activity of telomerase - the remarkable enzyme responsible for prolonging cellular lifespan by maintaining the length of telomeres at the ends of chromosomes. Telomerase is only normally active in embryonic and highly proliferative somatic cells. Thus, targeting telomerase is an attractive anti-cancer therapeutic rationale currently under investigation in various phases of clinical development. However, previous reports suggest that an average of 10-15% of all cancers lose the functional activity of telomerase and most of these turn to an Alternative Lengthening of Telomeres pathway (ALT). ALT-positive tumours will therefore not respond to anti-telomerase therapies and there is a real possibility that such drugs would be toxic to normal telomerase-utilising cells and ultimately select for resistant cells that activate an ALT mechanism. ALT exploits certain DNA damage response (DDR) components to counteract telomere shortening and rapid trimming. ALT has been reported in many cancer subtypes including sarcoma, gastric carcinoma, central nervous system malignancies, subtypes of kidney (Wilm's Tumour) and bladder carcinoma, mesothelioma, malignant melanoma and germ cell testicular cancers to name but a few. A recent heroic study that analysed ALT in over six thousand tumour samples supports this historical spread, although only reporting an approximate 4% prevalence. This review highlights the various methods of ALT detection, unravels several molecular ALT models thought to promote telomere maintenance and elongation, spotlights the DDR components known to facilitate these and explores why certain tissues are more likely to subvert DDR away from its usually protective functions, resulting in a predictive pattern of prevalence in specific cancer subsets.
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Affiliation(s)
- Stephen T Durant
- AstraZeneca - DNA Damage Response, Bioscience, Oncology iMed, Alderley Park, Cheshire, SK10 4TG, England, UK
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97
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Abstract
There is mounting evidence for the existence of an important relationship between telomeres and telomerase and cellular aging and cancer. Normal human cells progressively lose telomeres with each cell division until a few short telomeres become uncapped leading to a growth arrest known as replicative aging. In the absence of genomic alterations these cells do not die but remain quiescent producing a different constellation of proteins compared to young quiescent cells. Upon specific genetic and epigenetic alterations, normal human cells bypass replicative senescence and continue to proliferate until many telomere ends become uncapped leading to a phenomenon known as crisis. In crisis cells have critically shortened telomeres but continue to attempt to divide leading to significant cell death (apoptosis) and progressive genomic instability. Rarely, a human cell escapes crisis and these cells almost universally express the ribonucleoprotein, telomerase, and maintain stable but short telomeres. The activation of telomerase may be thought of as a mechanism to slow down the rate genomic instability due to dysfunctional telomeres. While telomerase does not drive the oncogenic process, it is permissive and required for the sustain growth of most advanced cancers. Since telomerase is not expressed in most normal human cells, this has led to the development of targeted telomerase cancer therapeutic approaches that are presently in advanced clinical trials.
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Affiliation(s)
- Jerry W Shay
- UT Southwestern Medical Center, Department of Cell Biology, 5323 Harry Hines Blvd, Dallas, TX 75390-9039, USA.
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98
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Shay JW, Wright WE. Role of telomeres and telomerase in cancer. Semin Cancer Biol 2011; 21:349-53. [PMID: 22015685 DOI: 10.1016/j.semcancer.2011.10.001] [Citation(s) in RCA: 341] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 09/29/2011] [Accepted: 10/01/2011] [Indexed: 12/23/2022]
Abstract
There is mounting evidence for the existence of an important relationship between telomeres and telomerase and cellular aging and cancer. Normal human cells progressively lose telomeres with each cell division until a few short telomeres become uncapped leading to a growth arrest known as replicative aging. In the absence of genomic alterations these cells do not die but remain quiescent producing a different constellation of proteins compared to young quiescent cells. Upon specific genetic and epigenetic alterations, normal human cells bypass replicative senescence and continue to proliferate until many telomere ends become uncapped leading to a phenomenon known as crisis. In crisis cells have critically shortened telomeres but continue to attempt to divide leading to significant cell death (apoptosis) and progressive genomic instability. Rarely, a human cell escapes crisis and these cells almost universally express the ribonucleoprotein, telomerase, and maintain stable but short telomeres. The activation of telomerase may be thought of as a mechanism to slow down the rate genomic instability due to dysfunctional telomeres. While telomerase does not drive the oncogenic process, it is permissive and required for the sustain growth of most advanced cancers. Since telomerase is not expressed in most normal human cells, this has led to the development of targeted telomerase cancer therapeutic approaches that are presently in advanced clinical trials.
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Affiliation(s)
- Jerry W Shay
- UT Southwestern Medical Center, Department of Cell Biology, 5323 Harry Hines Blvd, Dallas, TX 75390-9039, USA.
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