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Afzaal H, Altaf R, Ilyas U, Zaman SU, Abbas Hamdani SD, Khan S, Zafar H, Babar MM, Duan Y. Virtual screening and drug repositioning of FDA-approved drugs from the ZINC database to identify the potential hTERT inhibitors. Front Pharmacol 2022; 13:1048691. [DOI: 10.3389/fphar.2022.1048691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Accepted: 10/28/2022] [Indexed: 11/21/2022] Open
Abstract
The length of the telomeres is maintained with the help of the enzyme telomerase constituting of two components, namely, a core reverse transcriptase protein (hTERT) and RNA (hTR). It serves as a significant and universal cancer target. In silico approaches play a crucial role in accelerating drug development processes, especially cancer drug repurposing is an attractive approach. The current study is aimed at the repurposing of FDA-approved drugs for their potential role as hTERT inhibitors. Accordingly, a library of 2,915 sets of FDA-approved drugs was generated from the ZINC database in order to screen for novel hTERT inhibitors; later on, these were subjected to molecular docking analysis. The top two hits, ZINC03784182 and ZINC01530694, were shortlisted for molecular dynamic simulation studies at 100 ns based on their binding scores. The RMSD, RMSF, Rg, SASA, and interaction energies were calculated for a 100-ns simulation period. The hit compounds were also analyzed for antitumor activity, and the results revealed promising cytotoxic activities of these compounds. The study has revealed the potential application of these drugs as antitumor agents that can be useful in treating cancer and can serve as lead compounds for further in vivo, in vitro, and clinical studies.
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Marrone A, Dokal I. Dyskeratosis congenita: a disorder of telomerase deficiency and its relationship to other diseases. ACTA ACUST UNITED AC 2014. [DOI: 10.1586/17469872.1.3.463] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Gong HX, He L, Li XP, Wang YD, Li Y, Huang JJ, Wang Z, Xie D, Kung HF, Peng Y. Effective antitumor immunity against murine gliomas using dendritic cells transduced with hTERTC27 recombinant adenovirus. Oncol Rep 2011; 27:1163-9. [PMID: 22210010 PMCID: PMC3583520 DOI: 10.3892/or.2011.1619] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 12/02/2011] [Indexed: 01/05/2023] Open
Abstract
hTERTC27, a 27-kDa hTERT C-terminal polypeptide has been demonstrated to cause hTERT-positive HeLa cell apoptosis and inhibits the growth of mouse melanoma. hTERTC27 has been associated with telomere dysfunction, regulation of gene-regulated apoptosis, the cell cycle and activation of natural killer (NK) cells, but its mechanism of action is not fully understood. Here, we report that dendritic cells (DCs) transduced with hTERTC27 can increase T-cell proliferation, and augment the concentration of interleukin-2 (IL-2) and interferon-γ (IFN-γ) in the supernatants of T cells. It can also induce antigen-specific cytotoxic T lymphocytes (CTL) against glioma cells in vitro. Moreover, hTERTC27 gene-transduced DCs exhibit a very potent cytotoxicity to glioma cells in vivo. It could prolong the survival time and inhibit the growth of glioma-bearing mice. These data suggest that hTERTC27 gene-transduced DCs can efficiently enhance immunity against gliomas in vitro and in vivo.
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Affiliation(s)
- Han-Xian Gong
- Department of Neurology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou 510120, PR China
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Lin PC, Lin SZ, Chen YL, Chang JS, Ho LI, Liu PY, Chang LF, Harn YC, Chen SP, Sun LY, Huang PC, Chein JT, Tsai CH, Chou CW, Harn HJ, Chiou TW. Butylidenephthalide suppresses human telomerase reverse transcriptase (TERT) in human glioblastomas. Ann Surg Oncol 2011; 18:3514-27. [PMID: 21553143 DOI: 10.1245/s10434-011-1644-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2010] [Indexed: 12/29/2022]
Abstract
BACKGROUND Telomerase is widely expressed in most human cancers, but is almost undetectable in normal somatic cells and is therefore a potential drug target. Using the human telomerase promoter platform, the naturally occurring compound butylidenephthalide (BP) was selected for subsequent investigation of antitumor activity in vitro and in vivo. METHODS We treated human glioblastoma cells with BP and found a dose-dependent decrease in human telomerase reverse transcriptase (hTERT) mRNA expression and a concomitant increase in p16 and p21 expression. Because c-Myc and Sp1 are involved in transcriptional regulation of hTERT, the effect of BP on c-Myc and Sp1 expression was examined. RESULTS Using electrophoretic mobility shift assays and western blotting, we showed that BP represses hTERT transcriptional activity via downregulation of Sp1 expression. Using the telomerase repeat amplification protocol, an association between BP concentration and suppression of telomerase activity, induction of human glioblastoma senescence, and inhibition of cellular proliferation was identified. This was supported by a mouse xenograft model, in which BP repressed telomerase and inhibited tumor proliferation, resulting in tumor senescence. Overexpression of hTERT restored telomerase activity in human glioblastoma cells and overcame replicative senescence. CONCLUSIONS These findings suggest that BP inhibits proliferation and induces senescence in human glioblastomas by downregulating hTERT expression and consequently telomerase activity. This is the first study to describe regulation of telomerase activity by BP in human glioblastomas.
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Affiliation(s)
- Po-Cheng Lin
- Department of Life Science and Graduate Institute of Biotechnology, National Dong Hwa University, Hualien, Taiwan, Republic of China
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Kryukov F, Ocadlíková D, Kovárová L, Buresová I, Hájek R, Michálek J. In vitro activation of cytotoxic T-lymphocytes by hTERT-pulsed dendritic cells. J Immunotoxicol 2010; 6:243-8. [PMID: 19908943 DOI: 10.3109/15476910903236134] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Multiple myeloma has been considered a weakly immunogenic malignancy that can cause profound defects in the immune system. An important issue for the immunotherapy of myeloma is the identification of appropriate tumor-associated antigens (TAAs). Recently, hTERT (human telomerase reverse transcriptase) was detected on a majority of human malignancies. In the studies reported here, we studied antigen-specific and HLA-A2-restricted cytotoxic activity against an ARH77 myeloma cell line in vitro. An HLA-A2-specific hTERT-derived nonapeptide ((540)ILAKFLHWL(548)) was used as a TAA. Myeloma-specific cytotoxic activity of hTERT-reactive cytotoxic lymphocytes (CTLs) was established by repeated stimulation of the CTLs via dendritic cells loaded with hTERT-derived nonapeptide. These studies were able to demonstrate that hTERT-reactive T-lymphocytes can be identified and expanded using relatively simple in vitro techniques consisting of antigen-specific stimulation, immunomagnetic sorting, and then induction of rapid expansion.
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Affiliation(s)
- Fedor Kryukov
- University Cell Immunotherapy Center, Masaryk University, Brno, Czech Republic.
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A complex cell division machinery was present in the last common ancestor of eukaryotes. PLoS One 2009; 4:e5021. [PMID: 19352429 PMCID: PMC2661371 DOI: 10.1371/journal.pone.0005021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2009] [Accepted: 03/02/2009] [Indexed: 12/22/2022] Open
Abstract
Background The midbody is a transient complex structure containing proteins involved in cytokinesis. Up to now, it has been described only in Metazoa. Other eukaryotes present a variety of structures implied in the last steps of cell division, such as the septum in fungi or the phragmoplast in plants. However, it is unclear whether these structures are homologous (derive from a common ancestral structure) or analogous (have distinct evolutionary origins). Recently, the proteome of the hamster midbody has been characterized and 160 proteins identified. Methodology/Principal Findings Using phylogenomic approaches, we show here that nearly all of these 160 proteins (95%) are conserved across metazoan lineages. More surprisingly, we show that a large part of the mammalian midbody components (91 proteins) were already present in the last common ancestor of all eukaryotes (LECA) and were most likely involved in the construction of a complex multi-protein assemblage acting in cell division. Conclusions/Significance Our results indicate that the midbodies of non-mammalian metazoa are likely very similar to the mammalian one and that the ancestor of Metazoa possessed a nearly modern midbody. Moreover, our analyses support the hypothesis that the midbody and the structures involved in cytokinesis in other eukaryotes derive from a large and complex structure present in LECA, likely involved in cytokinesis. This is an additional argument in favour of the idea of a complex ancestor for all contemporary eukaryotes.
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Mantripragada KK, Caley M, Stephens P, Jones CJ, Kluwe L, Guha A, Mautner V, Upadhyaya M. Telomerase activity is a biomarker for high grade malignant peripheral nerve sheath tumors in neurofibromatosis type 1 individuals. Genes Chromosomes Cancer 2008; 47:238-46. [PMID: 18069666 DOI: 10.1002/gcc.20525] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Telomerase activity (TA) and the expression of its enzymatic subunits, which have been demonstrated in many tumors, remain poorly investigated in tumors associated with neurofibromatosis type 1 (NF1). In this study, we analysed the association of TA and the expression of telomerase RNA (TR) and telomerase reverse transcriptase (TERT) in 23 malignant peripheral nerve sheath tumors (MPNST) (17 high grade and 6 low grade tumors), 11 plexiform neurofibromas (PNF) and 6 dermal neurofibromas (DNF). TA was studied using telomerase repeat amplification protocol (TRAP) assay and expression of TR and TERT was investigated using reverse transcription PCR (RT-PCR) and real-time PCR. TA was detected in 14 out of 17 (82%) high grade MPNST, whereas all 6 low grade MPNST and 17 benign tumors were telomerase negative. The TERT transcripts were detected in all high grade MPNST, 50% of the low grade MPNST, and 4 benign tumors. However, the expression level of the TERT strikingly correlated with TA and high grade MPNST. Thus, while TERT expression was similar in both low grade MPNST and PNF (P = 0.115), it was significantly higher in high grade MPNST when compared to either low grade MPNST (P = 0.042), PNF (P = 0.001) or DNF tumors (P = 0.010). These findings indicate that TA and expression level of TERT are potential markers for high grade malignancy in NF1 patients.
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Cairney CJ, Keith WN. Telomerase redefined: Integrated regulation of hTR and hTERT for telomere maintenance and telomerase activity. Biochimie 2008; 90:13-23. [PMID: 17854971 DOI: 10.1016/j.biochi.2007.07.025] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Accepted: 07/23/2007] [Indexed: 10/23/2022]
Abstract
Telomerase activity is dependent on the expression of 2 main core component genes, hTERT, which encodes the catalytic component and hTR (also called TERC), which encodes the RNA component. The correlation between telomerase activity and carcinogenesis has made this molecule of great interest in cancer research, however in order to fully understand the regulation of telomerase the mechanisms controlling both telomerase genes need to be studied. Some of these mechanisms of regulation have begun to emerge, however many more remain to be deciphered. For many years hTERT has been regarded as the limiting component of telomerase and much of the research in this field has focussed on its regulation, however it was clear from an early stage that hTR expression was also tightly regulated in normal cells and disease. More recently evidence from biochemistry, promoter studies and mouse models has been steadily increasing for a role for hTR as a limiting and essential component for telomerase activity and telomere maintenance. Perhaps the time has come to redefine our view of telomerase regulation. Knowledge of the mechanisms controlling both telomerase genes in normal systems and cancer may aid our understanding of the role of telomerase in carcinogenesis or highlight potential areas for therapeutic intervention. Here we review the essential requirement of hTR for telomere maintenance and telomerase activity in normal tissues and disease and focus on recent advances in our understanding of hTR regulation in relation to hTERT.
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Affiliation(s)
- C J Cairney
- Centre for Oncology and Applied Pharmacology, University of Glasgow, Cancer Research UK Beatson Laboratories, Bearsden, Glasgow G61 1BD, UK
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9
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Phatak P, Burger AM. Telomerase and its potential for therapeutic intervention. Br J Pharmacol 2007; 152:1003-11. [PMID: 17603541 PMCID: PMC2095101 DOI: 10.1038/sj.bjp.0707374] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2007] [Revised: 06/08/2007] [Accepted: 06/08/2007] [Indexed: 01/12/2023] Open
Abstract
Telomerase and telomeres are attractive targets for anticancer therapy. This is supported by the fact that the majority of human cancers express the enzyme telomerase which is essential to maintain their telomere length and thus, to ensure indefinite cell proliferation--a hallmark of cancer. Tumours have relatively shorter telomeres compared to normal cell types, opening the possibility that human cancers may be considerably more susceptible to killing by agents that inhibit telomere replication than normal cells. Advances in the understanding of the regulation of telomerase activity and the telomere structure, as well as the identification of telomerase and telomere associated binding proteins have opened new avenues for therapeutic intervention. Here, we review telomere and telomerase biology and the various approaches which have been developed to inhibit the telomere/telomerase complex over the past decade. They include inhibitors of the enzyme catalytic subunit and RNA component, agents that target telomeres, telomerase vaccines and drugs targeting binding proteins. The emerging role of telomerase in cancer stem cells and the implications for cancer therapy are also discussed.
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Affiliation(s)
- P Phatak
- Department of Pharmacology and Experimental Therapeutics; and Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine Baltimore, MD, USA
| | - A M Burger
- Department of Pharmacology and Experimental Therapeutics; and Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine Baltimore, MD, USA
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Abstract
Treatment of pancreatic cancer remains challenging today and mostly palliative. Despite many efforts to understand the underlying mechanisms of this aggressive tumoral phenotype and to develop new therapeutic agents, advances in its management and survival benefit are poor. Although gemcitabine remains the backbone of routine therapy in advanced disease, newer drugs, mainly constituted by (multi)targeted agents, represent promising therapeutic areas. In this setting, anti-EGF receptor, antiangiogenic or both therapies combined appear to have valuable potential, providing their optimal and comprehensive development and use in pancreatic cancer. Multitargeted agents, such as receptor tyrosine kinase inhibitor small molecules, combining different therapeutic interventions, also deserve new preclinical and clinical development, supported and paralleled by a translational approach. Over the next few years, we need to identify new target mechanisms in pancreatic carcinogenesis, to rapidly test selected drugs against these targets and imperatively to understand and determine which patients respond and who will benefit from such therapies. Significant advances should be immediately evaluated in the perioperative setting in order to improve the curative approach of this devastating disease.
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Affiliation(s)
- Jean-Luc Van Laethem
- Erasme University Hospital, Department of Gastroenterology, Gastrointestinal Cancer Unit, ULB, Brussels.
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Bilsland AE, Merron A, Vassaux G, Keith WN. Modulation of telomerase promoter tumor selectivity in the context of oncolytic adenoviruses. Cancer Res 2007; 67:1299-307. [PMID: 17283167 DOI: 10.1158/0008-5472.can-06-3000] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The telomerase RNA (hTR) and reverse transcriptase (hTERT) promoters are active in most cancer cells, but not in normal cells, and are useful for transcriptional targeting in gene therapy models. Telomerase-specific conditionally replicating adenoviruses (CRAd) are attractive vectors because they should selectively lyse tumor cells. Here, we compare CRAds, in which either the hTR or hTERT promoter controls expression of the adenovirus E1A gene. In replication-defective reporter adenoviruses, the hTR promoter was up to 57-fold stronger in cancer cells than normal cells and up to 49-fold stronger than hTERT. In normal cells, hTERT promoter activity was essentially absent. Doses of telomerase-specific CRAds between 1.8 and 28 infectious units per cell efficiently killed cancer cells, but normal cells required higher doses. However, CRAd DNA replication and E1A expression were detected in both cancer and normal cells. Overall, tumor specificity of the CRAds was limited compared with nonreplicating vectors. Surprisingly, both CRAds expressed similar E1A levels and functional behavior, despite known differentials between hTR and hTERT promoter activities, suggesting that the promoters are deregulated. Rapid amplification of cDNA ends analysis of hTR-/hTERT-E1A transcripts ruled out cryptic transcription from the vector backbone. Blocking E1A translation partially restored the hTR-/hTERT-E1A mRNA differential, evidencing feedback regulation by E1A.
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Affiliation(s)
- Alan E Bilsland
- Centre for Oncology and Applied Pharmacology, University of Glasgow, Cancer Research UK Beatson Laboratories, Garscube Estate, Switchback Road, Bearsden, Glasgow, UK
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Shervington A, Patel R, Lu C, Cruickshanks N, Lea R, Roberts G, Dawson T, Shervington L. Telomerase subunits expression variation between biopsy samples and cell lines derived from malignant glioma. Brain Res 2007; 1134:45-52. [PMID: 17196947 DOI: 10.1016/j.brainres.2006.11.093] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2006] [Revised: 11/29/2006] [Accepted: 11/30/2006] [Indexed: 01/12/2023]
Abstract
Although scientific advances have recognised the prognostic power of telomerase activity in different cancers, as yet there has been no investigation regarding the expression variation of telomerase subunits in glioma tissues and cell lines. In this study, a recurrent anaplastic ependymoma and seven glioblastoma biopsy samples, four cell lines and four controls including two normal brain tissues were analysed for telomerase subunit expression profiles together with telomerase activity. Since telomerase activity is linked to tumourgenesis, the genes were analysed with respect to their expression variation. TEP1 was expressed in all glioma cell lines and 70% of glioblastoma tissues, in addition to the control brain tissues. Tankyrase was expressed in 85% of the glioblastoma tissues and was down-regulated in the recurrent anaplastic ependymoma tissue control cell lines. However, it was expressed in the control tissues. Dyskerin was expressed in all cell lines and tissues apart from U87-MG and NHA cells and the recurrent anaplastic ependymoma tissue. As expected, PARP1 and GAPDH showed constitutive expression throughout all cell lines and tissues since both are known to be housekeeping genes. hTERT was expressed in all glioma cell lines and tissues but was absent in the control cells and tissues. Telomerase activity was absent in IPDDC-A2 cells and 57% of the glioblastoma tissues. These results suggest that hTERT expression and not telomerase activity possibly represents a simple and reliable biological diagnostic tool.
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Affiliation(s)
- Amal Shervington
- Department of Biological Sciences, University of Central Lancashire, and Neurosurgery Department, Royal Preston Hospital, UK.
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13
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Emerald BS, Chen Y, Zhu T, Zhu Z, Lee KO, Gluckman PD, Lobie PE. AlphaCP1 mediates stabilization of hTERT mRNA by autocrine human growth hormone. J Biol Chem 2006; 282:680-90. [PMID: 17085453 DOI: 10.1074/jbc.m600224200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We herein demonstrate that autocrine human growth hormone production in human mammary carcinoma cells results in increased telomerase activity as a result of specific up-regulation of telomerase catalytic subunit (human telomerase reverse transcriptase (hTERT)) mRNA and protein. This increase in hTERT gene expression is not due to increased transcriptional activation of the hTERT promoter but is the result of increased stability of hTERT mRNA exerted by CU-rich cis-regulatory sequences present in the 3'-untranslated region of TERT mRNA. Autocrine human growth hormone up-regulates two poly(C)-binding proteins, alphaCP1 and alphaCP2, which bind to these cis-regulatory elements and stabilize hTERT mRNA. We have therefore demonstrated that post-transcriptional modulation of the level of hTERT mRNA is one mechanism for regulation of cellular telomerase activity.
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Affiliation(s)
- B Starling Emerald
- Liggins Institute and the National Research Centre for Growth and Development, University of Auckland, Auckland, New Zealand
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Bilsland AE, Stevenson K, Atkinson S, Kolch W, Keith WN. Transcriptional Repression of Telomerase RNA Gene Expression by c-Jun-NH2-Kinase and Sp1/Sp3. Cancer Res 2006; 66:1363-70. [PMID: 16452190 DOI: 10.1158/0008-5472.can-05-1941] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Telomerase is essential for immortalization of most human cancer cells. Expression of the core telomerase RNA (hTR) and reverse transcriptase (hTERT) subunits is mainly regulated by transcription. However, hTR transcriptional regulation remains poorly understood. We previously showed that the core hTR promoter is activated by Sp1 and is repressed by Sp3. Here, we show that the mitogen-activated protein kinase kinase kinase 1 (MEKK1)/c-Jun-NH(2)-kinase (JNK) pathway represses hTR expression by a mechanism that involves Sp1 and Sp3. Promoter activity was induced by the JNK inhibitor SP600125 and was repressed by activated MEKK1. Repression by MEKK1 was blocked by SP600125 or enhanced by coexpression of wild-type but not phosphoacceptor mutated JNK. SP600125 treatment also increased levels of endogenous hTR. Mutations in the hTR promoter Sp1/Sp3 binding sites attenuated SP600125-mediated promoter induction, whereas coexpression of MEKK1 with Sp3 enhanced hTR promoter repression. Chromatin immunoprecipitation showed that levels of immunoreactive Sp1 associated with the hTR promoter were low in comparison with Sp3 in control cells but increased after JNK inhibition with a reciprocal decrease in Sp3 levels. No corresponding changes in Sp1/Sp3 protein levels were detected. Thus, JNK represses hTR promoter activity and expression, apparently by enhancing repression through Sp3.
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Affiliation(s)
- Alan E Bilsland
- Centre for Oncology and Applied Pharmacology, University of Glasgow, Scotland, UK
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Bilsland AE, Fletcher-Monaghan A, Keith WN. Properties of a telomerase-specific Cre/Lox switch for transcriptionally targeted cancer gene therapy. Neoplasia 2006; 7:1020-9. [PMID: 16331888 PMCID: PMC1502022 DOI: 10.1593/neo.05385] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2005] [Revised: 08/02/2005] [Accepted: 08/03/2005] [Indexed: 11/18/2022]
Abstract
Telomerase expression represents a good target for cancer gene therapy. The promoters of the core telomerase catalytic [human telomerase reverse transcriptase (hTERT)] and RNA [human telomerase RNA (hTR)] subunits show selective activity in cancer cells but not in normal cells. This property can be harnessed to express therapeutic transgenes in a wide range of cancer cells. Unfortunately, weak hTR and hTERT promoter activities in some cancer cells could limit the target cell range. Therefore, strategies to enhance telomerase-specific gene therapy are of interest. We constructed a Cre/Lox reporter switch coupling telomerase promoter specificity with Cytomegalovirus (CMV) promoter activity, which is generally considered to be constitutively high. In this approach, a telomerase-specific vector expressing Cre recombinase directs excisive recombination on a second vector, removing a transcriptional blockade to CMV-dependent luciferase expression. We tested switch activation in cell lines over a wide range of telomerase promoter activities. However, Cre/Lox-dependent luciferase expression was not enhanced relative to expression using hTR or hTERT promoters directly. Cell-specific differences between telomerase and CMV promoter activities and incomplete sigmoid switch activation were limiting factors. Notably, CMV activity was not always significantly stronger than telomerase promoter activity. Our conclusions provide a general basis for a more rational design of novel recombinase switches in gene therapy.
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Affiliation(s)
- Alan E Bilsland
- Cancer Research UK Centre for Oncology and Applied Pharmacology, University of Glasgow, Cancer Research UK Beatson Laboratories, Garscube Estate, Switchback Road, UK
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Serakinci N, Hoare SF, Kassem M, Atkinson SP, Keith WN. Telomerase promoter reprogramming and interaction with general transcription factors in the human mesenchymal stem cell. Regen Med 2006; 1:125-31. [PMID: 17465827 DOI: 10.2217/17460751.1.1.125] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The human adult mesenchymal stem cell (hMSC) does not express telomerase and has been shown to be the target for neoplastic transformation after transduction with hTERT. These findings lend support to the stem cell hypothesis of cancer development but by supplying hTERT, the molecular events required to upregulate hTERT expression in cancer development are missed. Therefore, the hMSC is ideal for the identification of molecular mechanisms regulating telomerase gene expression in stem cells. This study shows that the repression of hTERT expression in hMSC is chromatin based and that modifications of the chromatin environment lead to reactivation of telomerase gene expression. It is shown that repression of hTERT expression in hMSCs is due to promoter-specific histone hypoacetylation coupled with low Pol II and TFIIB trafficking. This repression is overcome by treatment with Trichostatin A (TSA), an HDAC inhibitor, concomitant with increases in promoter-specific histone acetylation and increases in Pol II and TFIIB tracking. hTR expression is also increased in TSA-treated hMSCs, concomitant with changes in Pol II and TFIIB dynamics.
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Affiliation(s)
- Nedime Serakinci
- University of Southern Denmark, Institute of Medical Biology, Department of Anatomy and Neurobiology, Odense C, Denmark
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17
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Brümmendorf TH. Telomerase Activity – a Prognostic Factor in Colorectal Cancer? Oncol Res Treat 2005; 28:550-1. [PMID: 16249639 DOI: 10.1159/000088298] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Indexed: 11/19/2022]
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Ghosh U, Bhattacharyya NP. Benzamide and 4-amino 1,8 naphthalimide treatment inhibit telomerase activity by down-regulating the expression of telomerase associated protein and inhibiting the poly(ADP-ribosyl)ation of telomerase reverse transcriptase in cultured cells. FEBS J 2005; 272:4237-48. [PMID: 16098204 DOI: 10.1111/j.1742-4658.2005.04837.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
To test the role of poly(ADP-ribose) polymerase on the telomerase activity, we determined the telomerase activity in leukemic cells K562 treated with benzamide and 4-amino 1,8 naphthalimide (NAP), the inhibitors of PARP. We observed that both the agents inhibited telomerase activity in a dose-dependent manner. The doses of benzamide and NAP that inhibited telomerase activity to 50% of untreated control cells were 10.7 +/- 0.6 mm and 200 +/- 7 microm, respectively. Benzamide treatment (10 mm) inhibited telomerase activity in a time-dependent manner. We also tested the ability of benzamide to inhibit the telomerase activity in Chinese hamster V79 cells and observed similar inhibition of the telomerase activity. Expression of telomerase reverse transcriptase (TERT) and telomerase RNA component, detected by RT-PCR, remained unaltered by treatment with benzamide or NAP. On the contrary, the expression of telomerase associated protein (TEP1/TP1), as detected by RT-PCR and western blot analysis, was reduced by both the agents. Further, in K562 cells, immunoprecipitation with the anti-TERT IgG and probed anti-poly (ADP-ribose) IgG revealed that TERT was poly(ADP-ribosyl)ated in the physiological condition of cell growth and such poly(ADP-ribosyl)ation was inhibited by benzamide treatment. Decrease in TEP1/TP1 expression and poly(ADP-ribosyl)ation of TERT were correlated with the inhibition of PARP activity by benzamide, indicating that PARP had a role in telomerase activity through poly(ADP-ribosyl)ation of TERT and down-regulation of TEP1/TP1.
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Affiliation(s)
- Utpal Ghosh
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, Calcutta, India
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Savage SA, Stewart BJ, Liao JS, Helman LJ, Chanock SJ. Telomere stability genes are not mutated in osteosarcoma cell lines. ACTA ACUST UNITED AC 2005; 160:79-81. [PMID: 15949576 DOI: 10.1016/j.cancergencyto.2004.12.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2004] [Revised: 12/02/2004] [Accepted: 12/03/2004] [Indexed: 10/25/2022]
Abstract
Osteosarcoma (OS), the most common primary bone tumor in adolescents and young adults, is characterized by a high degree of chromosomal abnormalities. Because telomeres are important for maintaining chromosomal integrity, it is plausible that germ-line or somatic mutations in the genes responsible for stabilizing the telomere complex could contribute to OS. We performed bi-directional sequence analysis in five OS cell lines and targeted all exons and proximal promoter regions in eight genes important in telomere stability: telomerase, the RNA component of telomerase (TERC), telomeric repeat binding factor 1, telomeric repeat binding factor 2, TERF1 interacting nuclear factor 2, human Rap1, protection of telomeres 1 and tankyrase. In this pilot study, we did not identify either somatic mutations or novel germ-line mutations in the five cell lines studied. However, we did confirm common genetic polymorphisms; an analysis of heterozygous sites suggests that loss of heterozygosity in OS is not present across these eight genes.
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Affiliation(s)
- Sharon A Savage
- Section of Genomic Variation, Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Advanced Technology Center, 8717 Grovemont Circle, Bethesda, MD 20892-4605, USA.
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Keith WN, Bilsland A, Hardie M, Evans TRJ. Drug Insight: cancer cell immortality—telomerase as a target for novel cancer gene therapies. ACTA ACUST UNITED AC 2004; 1:88-96. [PMID: 16264826 DOI: 10.1038/ncponc0044] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2004] [Accepted: 10/20/2004] [Indexed: 11/08/2022]
Abstract
Rapid advances in our understanding of the molecular basis of cancer development and progression over the past three decades have led to the design of new potential cancer therapies. High throughput target validation and expression studies are expected to yield a powerful arsenal of new cancer treatments, but untangling the complex pathways underlying the major cancer phenotypes remains a significant challenge. A considerable body of evidence in recent years implicates deregulated expression of a single multi-component enzyme, telomerase, as a causative factor at the heart of immortalization in the vast majority of human tumors. This review highlights the potential of telomerase as a target for novel cancer therapies. The potential of exploiting the selectivity of the telomerase family of genes within cancer cells to develop gene therapy strategies is discussed, and the progress towards translating these novel therapeutics from the laboratory to the clinic is reviewed.
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Affiliation(s)
- W Nicol Keith
- Telomerase Therapeutics Program, CRUK Centre for Oncology and Applied Pharmacology, Glasgow, UK.
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Norgren RB. Creation of non-human primate neurogenetic disease models by gene targeting and nuclear transfer. Reprod Biol Endocrinol 2004; 2:40. [PMID: 15200671 PMCID: PMC455690 DOI: 10.1186/1477-7827-2-40] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2004] [Accepted: 06/16/2004] [Indexed: 12/02/2022] Open
Abstract
Genetically modified rhesus macaques are necessary because mouse models are not suitable for a number of important neurogenetic disorders; for example, Kallmann's syndrome, Lesch-Nyhan's disease and Ataxia-Telangiectasia. Mouse models may not be suitable because there may be no mouse ortholog of the human gene of interest, as is the case for Kallmann's syndrome, or because mutant mice do not exhibit the same phenotype observed in humans, as is the the case for Lesch-Nyhan's disease and Ataxia-Telangiectasia. Non-human primate models of neurogenetic diseases are expected to more closely resemble human diseases than existing mouse models. Genetically modified rhesus macaques can be created by modifying the genome of a somatic cell and then transferring the nucleus from this cell to an enucleated oocyte. Random integration of a transgene is sufficient to create models of gain-of-function genetic diseases. Stable expression of green fluorescent protein has been achieved in rhesus macaque fibroblasts. However, gene targeting is necessary to create models of loss-of-function genetic diseases. Several technical challenges must be overcome before null mutant non-human primates can be produced. In our experience, fetal fibroblasts frequently become senescent before selection procedures can be completed. We have overcome this problem by transfecting somatic cells with human telomerase reverse transcriptase. This enzyme extends the telomeres, and lifespan, of somatic cells. Long and accurate polymerase chain reaction can be used to obtain sufficient regions of homology of isogenic rhesus genomic DNA for targeting constructs. This should improve gene targeting efficiency. Gene targeting experiments are currently underway. Null mutant rhesus macaques will likely result in breakthrough advances in the understanding of neurogenetic disease and prove invaluable for preclinical trials of new therapies.
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Affiliation(s)
- Robert B Norgren
- Department of Genetics, Cell Biology and Anatomy, University of Nebraska Medical Center, Omaha, Nebraska, USA.
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Alvarez-Núñez F, Mora J, Matías-Guiu X. [Thyroid carcinomas of the follicular epithelium: tumor markers and oncogenes]. Med Clin (Barc) 2003; 121:264-9. [PMID: 12975039 DOI: 10.1016/s0025-7753(03)75192-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Several genes control cell growth, differentiation and apoptosis. Any alteration in the sequence or expression of these genes can cause an uncontrolled growth of the tissue and produce a tumor. Quantitative and qualitative gene expression studies using genes as tumor markers are essential for the diagnosis and prognosis of the tumor and its behavior. Oncogenes are genes that stimulate cell growth and have an increased expression. On the contrary, tumor suppressor genes are genes that inhibit cell growth and have a decreased expression in tumor cells. To study these tumor markers we apply simple and random molecular biology techniques such as polymerase chain reaction (PCR), reverse transcription and genomic sequencing. In the case of thyroid epithelial neoplasia, tumor markers such as PTEN/MMAC1/TEP1, telomerase, RET/PTC, b-catenine, PAX8/PPAR(1, ciclooxygenase, thyroid stimulating hormonal receptor (TSHR), and thyro-globulin are being investigated. These markers are analyzed for somatic mutations in the genetic sequence, chromosomical rearrangements, alterations in the promoter zone that affect gene expression, regulation and studies of genes at mRNA level. A deeper study of these markers is deemed to help improve the accuracy of tumor diagnosis, behavior and prognosis. Hence, more effective therapeutic options will be adapted to each individual, eventually reducing hospital costs.
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Abstract
A number of different approaches have been developed to inhibit telomerase activity in human cancer cells. Different components and types of inhibitors targeting various regulatory levels have been regarded as useful for telomerase inhibition. Most methods, however, rely on successive telomere shortening. This process is very slow and causes a long time lag between the onset of inhibition and the occurrence of senescence or apoptosis as a reversal of the immortal phenotype. Many telomerase inhibitors seem to be most efficient when combined with conventional chemotherapeutics. There are some promising approaches that seem to circumvent the slow way of telomere shortening and induce fast apoptosis in treated tumor cells. It has been demonstrated that telomerase may be involved in triggering apoptosis, but the underlying molecular mechanism remains unclear.
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Chen Z, Corey DR. Telomerase inhibitors: a new option for chemotherapy. Adv Cancer Res 2003. [DOI: 10.1016/s0065-230x(03)87294-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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