1
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Taheri M, Ghafouri-Fard S, Najafi S, Kallenbach J, Keramatfar E, Atri Roozbahani G, Heidari Horestani M, Hussen BM, Baniahmad A. Hormonal regulation of telomerase activity and hTERT expression in steroid-regulated tissues and cancer. Cancer Cell Int 2022; 22:258. [PMID: 35974340 PMCID: PMC9380309 DOI: 10.1186/s12935-022-02678-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 08/05/2022] [Indexed: 11/10/2022] Open
Abstract
Naturally, in somatic cells chromosome ends (telomeres) shorten during each cell division. This process ensures to limit proliferation of somatic cells to avoid malignant proliferation; however, it leads to proliferative senescence. Telomerase contains the reverse transcriptase TERT, which together with the TERC component, is responsible for protection of genome integrity by preventing shortening of telomeres through adding repetitive sequences. In addition, telomerase has non-telomeric function and supports growth factor independent growth. Unlike somatic cells, telomerase is detectable in stem cells, germ line cells, and cancer cells to support self-renewal and expansion. Elevated telomerase activity is reported in almost all of human cancers. Increased expression of hTERT gene or its reactivation is required for limitless cellular proliferation in immortal malignant cells. In hormonally regulated tissues as well as in prostate, breast and endometrial cancers, telomerase activity and hTERT expression are under control of steroid sex hormones and growth factors. Also, a number of hormones and growth factors are known to play a role in the carcinogenesis via regulation of hTERT levels or telomerase activity. Understanding the role of hormones in interaction with telomerase may help finding therapeutical targets for anticancer strategies. In this review, we outline the roles and functions of several steroid hormones and growth factors in telomerase regulation, particularly in hormone regulated cancers such as prostate, breast and endometrial cancer.
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Affiliation(s)
- Mohammad Taheri
- Urology and Nephrology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Institute of Human Genetics, Jena University Hospital, 07740, Jena, Germany
| | - Soudeh Ghafouri-Fard
- Department of Medical Genetics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Sajad Najafi
- Department of Medical Biotechnology, School of Advanced Technologies in Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Julia Kallenbach
- Institute of Human Genetics, Jena University Hospital, 07740, Jena, Germany
| | - Elmira Keramatfar
- Institute of Human Genetics, Jena University Hospital, 07740, Jena, Germany
| | | | | | - Bashdar Mahmud Hussen
- Department of Pharmacognosy, College of Pharmacy, Hawler Medical University, Kurdistan Region, Erbil, Iraq.,Center of Research and Strategic Studies, Lebanese French University, Erbil, Kurdistan Region, Iraq
| | - Aria Baniahmad
- Institute of Human Genetics, Jena University Hospital, 07740, Jena, Germany.
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2
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Rozenberg JM, Zvereva S, Dalina A, Blatov I, Zubarev I, Luppov D, Bessmertnyi A, Romanishin A, Alsoulaiman L, Kumeiko V, Kagansky A, Melino G, Ganini C, Barlev NA. The p53 family member p73 in the regulation of cell stress response. Biol Direct 2021; 16:23. [PMID: 34749806 PMCID: PMC8577020 DOI: 10.1186/s13062-021-00307-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 10/12/2021] [Indexed: 12/14/2022] Open
Abstract
During oncogenesis, cells become unrestrictedly proliferative thereby altering the tissue homeostasis and resulting in subsequent hyperplasia. This process is paralleled by resumption of cell cycle, aberrant DNA repair and blunting the apoptotic program in response to DNA damage. In most human cancers these processes are associated with malfunctioning of tumor suppressor p53. Intriguingly, in some cases two other members of the p53 family of proteins, transcription factors p63 and p73, can compensate for loss of p53. Although both p63 and p73 can bind the same DNA sequences as p53 and their transcriptionally active isoforms are able to regulate the expression of p53-dependent genes, the strongest overlap with p53 functions was detected for p73. Surprisingly, unlike p53, the p73 is rarely lost or mutated in cancers. On the contrary, its inactive isoforms are often overexpressed in cancer. In this review, we discuss several lines of evidence that cancer cells develop various mechanisms to repress p73-mediated cell death. Moreover, p73 isoforms may promote cancer growth by enhancing an anti-oxidative response, the Warburg effect and by repressing senescence. Thus, we speculate that the role of p73 in tumorigenesis can be ambivalent and hence, requires new therapeutic strategies that would specifically repress the oncogenic functions of p73, while keeping its tumor suppressive properties intact.
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Affiliation(s)
- Julian M Rozenberg
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia.
| | - Svetlana Zvereva
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Aleksandra Dalina
- The Engelhardt Institute of Molecular Biology, Russian Academy of Science, Moscow, Russia
| | - Igor Blatov
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Ilya Zubarev
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Daniil Luppov
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | | | - Alexander Romanishin
- School of Biomedicine, Far Eastern Federal University, Vladivostok, Russia.,School of Life Sciences, Immanuel Kant Baltic Federal University, Kaliningrad, Russia
| | - Lamak Alsoulaiman
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
| | - Vadim Kumeiko
- School of Biomedicine, Far Eastern Federal University, Vladivostok, Russia
| | - Alexander Kagansky
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia.,School of Biomedicine, Far Eastern Federal University, Vladivostok, Russia
| | - Gerry Melino
- Department of Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Carlo Ganini
- Department of Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Nikolai A Barlev
- Cell Signaling Regulation Laboratory, Moscow Institute of Physics and Technology, Dolgoprudny, Russia. .,Institute of Cytology, Russian Academy of Science, Saint-Petersburg, Russia.
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3
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Tomasova K, Kroupa M, Forsti A, Vodicka P, Vodickova L. Telomere maintenance in interplay with DNA repair in pathogenesis and treatment of colorectal cancer. Mutagenesis 2021; 35:261-271. [PMID: 32083302 DOI: 10.1093/mutage/geaa005] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 01/29/2020] [Indexed: 12/14/2022] Open
Abstract
Colorectal cancer (CRC) continues to be one of the leading malignancies and causes of tumour-related deaths worldwide. Both impaired DNA repair mechanisms and disrupted telomere length homeostasis represent key culprits in CRC initiation, progression and prognosis. Mechanistically, altered DNA repair results in the accumulation of mutations in the genome and, ultimately, in genomic instability. DNA repair also determines the response to chemotherapeutics in CRC treatment, suggesting its utilisation in the prediction of therapy response and individual approach to patients. Telomere attrition resulting in replicative senescence, simultaneously by-passing cell cycle checkpoints, is a hallmark of malignant transformation of the cell. Telomerase is almost ubiquitous in advanced solid cancers, including CRC, and its expression is fundamental to cell immortalisation. Therefore, there is a persistent effort to develop therapeutics, which are telomerase-specific and gentle to non-malignant tissues. However, in practice, we are still at the level of clinical trials. The current state of knowledge and the route, which the research takes, gives us a positive perspective that the problem of molecular models of telomerase activation and telomere length stabilisation will finally be solved. We summarise the current literature herein, by pointing out the crosstalk between proteins involved in DNA repair and telomere length homeostasis in relation to CRC.
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Affiliation(s)
- Kristyna Tomasova
- Department of Molecular Biology of Cancer, Institute of Experimental Medicine, The Czech Academy of Sciences, Vídeňská, Praha, Czech Republic.,Faculty of Medicine and Biomedical Center in Pilsen, Charles University, Pilsen, Alej Svobody, Plzeň, Czech Republic
| | - Michal Kroupa
- Department of Molecular Biology of Cancer, Institute of Experimental Medicine, The Czech Academy of Sciences, Vídeňská, Praha, Czech Republic.,Faculty of Medicine and Biomedical Center in Pilsen, Charles University, Pilsen, Alej Svobody, Plzeň, Czech Republic
| | - Asta Forsti
- Hopp Children's Cancer Center (KiTZ), Im Neuenheimer Feld, Heidelberg, Germany.,Division of Pediatric Neurooncology, German Cancer Research Center (DKFZ), German Cancer Consortium (DKTK), Im Neuenheimer Feld, Heidelberg, Germany
| | - Pavel Vodicka
- Department of Molecular Biology of Cancer, Institute of Experimental Medicine, The Czech Academy of Sciences, Vídeňská, Praha, Czech Republic.,Faculty of Medicine and Biomedical Center in Pilsen, Charles University, Pilsen, Alej Svobody, Plzeň, Czech Republic.,Institute of Biology and Medical Genetics, First Faculty of Medicine, Charles University, Albertov, Praha, Czech Republic
| | - Ludmila Vodickova
- Department of Molecular Biology of Cancer, Institute of Experimental Medicine, The Czech Academy of Sciences, Vídeňská, Praha, Czech Republic.,Faculty of Medicine and Biomedical Center in Pilsen, Charles University, Pilsen, Alej Svobody, Plzeň, Czech Republic.,Institute of Biology and Medical Genetics, First Faculty of Medicine, Charles University, Albertov, Praha, Czech Republic
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4
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Trybek T, Kowalik A, Góźdź S, Kowalska A. Telomeres and telomerase in oncogenesis. Oncol Lett 2020; 20:1015-1027. [PMID: 32724340 PMCID: PMC7377093 DOI: 10.3892/ol.2020.11659] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 03/25/2020] [Indexed: 12/24/2022] Open
Abstract
Telomeres are located at the ends of chromosomes and protect them from degradation. Suppressing the activity of telomerase, a telomere-synthesizing enzyme, and maintaining short telomeres is a protective mechanism against cancer in humans. In most human somatic cells, the expression of telomerase reverse transcriptase (TERT) is repressed and telomerase activity is inhibited. This leads to the progressive shortening of telomeres and inhibition of cell growth in a process called replicative senescence. Most types of primary cancer exhibit telomerase activation, which allows uncontrolled cell proliferation. Previous research indicates that TERT activation also affects cancer development through activities other than the canonical function of mediating telomere elongation. Recent studies have improved the understanding of the structure and function of telomeres and telomerase as well as key mechanisms underlying the activation of TERT and its role in oncogenesis. These advances led to a search for drugs that inhibit telomerase as a target for cancer therapy. The present review article summarizes the organization and function of telomeres, their role in carcinogenesis, and advances in telomerase-targeted therapy.
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Affiliation(s)
- Tomasz Trybek
- Endocrinology Clinic, Holycross Cancer Center, 25-734 Kielce, Poland
| | - Artur Kowalik
- Department of Molecular Diagnostics, Holycross Cancer Center, 25-734 Kielce, Poland
| | - Stanisław Góźdź
- The Faculty of Health Sciences, Jan Kochanowski University, 25-319 Kielce, Poland.,Oncology Clinic, Holycross Cancer Center, 25-734 Kielce, Poland
| | - Aldona Kowalska
- Endocrinology Clinic, Holycross Cancer Center, 25-734 Kielce, Poland.,The Faculty of Health Sciences, Jan Kochanowski University, 25-319 Kielce, Poland
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5
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Berei J, Eckburg A, Miliavski E, Anderson AD, Miller RJ, Dein J, Giuffre AM, Tang D, Deb S, Racherla KS, Patel M, Vela MS, Puri N. Potential Telomere-Related Pharmacological Targets. Curr Top Med Chem 2020; 20:458-484. [DOI: 10.2174/1568026620666200109114339] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 11/21/2019] [Accepted: 11/21/2019] [Indexed: 12/22/2022]
Abstract
Telomeres function as protective caps at the terminal portion of chromosomes, containing
non-coding nucleotide sequence repeats. As part of their protective function, telomeres preserve genomic
integrity and minimize chromosomal exposure, thus limiting DNA damage responses. With
continued mitotic divisions in normal cells, telomeres progressively shorten until they reach a threshold
at a point where they activate senescence or cell death pathways. However, the presence of the enzyme
telomerase can provide functional immortality to the cells that have reached or progressed past
senescence. In senescent cells that amass several oncogenic mutations, cancer formation can occur due
to genomic instability and the induction of telomerase activity. Telomerase has been found to be expressed
in over 85% of human tumors and is labeled as a near-universal marker for cancer. Due to this
feature being present in a majority of tumors but absent in most somatic cells, telomerase and telomeres
have become promising targets for the development of new and effective anticancer therapeutics.
In this review, we evaluate novel anticancer targets in development which aim to alter telomerase
or telomere function. Additionally, we analyze the progress that has been made, including preclinical
studies and clinical trials, with therapeutics directed at telomere-related targets. Furthermore, we review
the potential telomere-related therapeutics that are used in combination therapy with more traditional
cancer treatments. Throughout the review, topics related to medicinal chemistry are discussed,
including drug bioavailability and delivery, chemical structure-activity relationships of select therapies,
and the development of a unique telomere assay to analyze compounds affecting telomere elongation.
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Affiliation(s)
- Joseph Berei
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Adam Eckburg
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Edward Miliavski
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Austin D. Anderson
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Rachel J. Miller
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Joshua Dein
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Allison M. Giuffre
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Diana Tang
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Shreya Deb
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Kavya Sri Racherla
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Meet Patel
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Monica Saravana Vela
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
| | - Neelu Puri
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, United States
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6
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Srinivas N, Rachakonda S, Kumar R. Telomeres and Telomere Length: A General Overview. Cancers (Basel) 2020; 12:E558. [PMID: 32121056 PMCID: PMC7139734 DOI: 10.3390/cancers12030558] [Citation(s) in RCA: 131] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/24/2020] [Accepted: 02/26/2020] [Indexed: 02/06/2023] Open
Abstract
Telomeres are highly conserved tandem nucleotide repeats that include proximal double-stranded and distal single-stranded regions that in complex with shelterin proteins afford protection at chromosomal ends to maintain genomic integrity. Due to the inherent limitations of DNA replication and telomerase suppression in most somatic cells, telomeres undergo age-dependent incremental attrition. Short or dysfunctional telomeres are recognized as DNA double-stranded breaks, triggering cells to undergo replicative senescence. Telomere shortening, therefore, acts as a counting mechanism that drives replicative senescence by limiting the mitotic potential of cells. Telomere length, a complex hereditary trait, is associated with aging and age-related diseases. Epidemiological data, in general, support an association with varying magnitudes between constitutive telomere length and several disorders, including cancers. Telomere attrition is also influenced by oxidative damage and replicative stress caused by genetic, epigenetic, and environmental factors. Several single nucleotide polymorphisms at different loci, identified through genome-wide association studies, influence inter-individual variation in telomere length. In addition to genetic factors, environmental factors also influence telomere length during growth and development. Telomeres hold potential as biomarkers that reflect the genetic predisposition together with the impact of environmental conditions and as targets for anti-cancer therapies.
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Affiliation(s)
| | | | - Rajiv Kumar
- Division of Functional Genome Analysis, German Cancer Research Center, Im Neunheimer Feld 580, 69120 Heidelberg, Germany; (N.S.); (S.R.)
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7
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Assani G, Xiong Y, Zhou F, Zhou Y. Effect of therapies-mediated modulation of telomere and/or telomerase on cancer cells radiosensitivity. Oncotarget 2018; 9:35008-35025. [PMID: 30405890 PMCID: PMC6201854 DOI: 10.18632/oncotarget.26150] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 07/31/2018] [Indexed: 12/11/2022] Open
Abstract
Cancer is one of the leading causes of death in the world. Many strategies of cancer treatment such as radiotherapy which plays a key role in cancer treatment are developed and used nowadays. However, the side effects post-cancer radiotherapy and cancer radioresistance are two major causes of the limitation of cancer radiotherapy effectiveness in the cancer patients. Moreover, reduction of the limitation of cancer radiotherapy effectiveness by reducing the side effects post-cancer radiotherapy and cancer radioresistance is the aim of several radiotherapy-oncologic teams. Otherwise, Telomere and telomerase are two cells components which play an important role in cancer initiation, cancer progression and cancer therapy resistance such as radiotherapy resistance. For resolving the problems of the limitation of cancer radiotherapy effectiveness especially the cancer radio-resistance problems, the radio-gene-therapy strategy which is the use of gene-therapy via modulation of gene expression combined with radiotherapy was developed and used as a new strategy to treat the patients with cancer. In this review, we summarized the information concerning the implication of telomere and telomerase modulation in cancer radiosensitivity.
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Affiliation(s)
- Ganiou Assani
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China
- Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuhan, China
- Hubei Key Laboratory of Tumor Biology Behaviors, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Yudi Xiong
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China
- Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuhan, China
- Hubei Key Laboratory of Tumor Biology Behaviors, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Fuxiang Zhou
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China
- Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuhan, China
- Hubei Key Laboratory of Tumor Biology Behaviors, Zhongnan Hospital of Wuhan University, Wuhan, China
| | - Yunfeng Zhou
- Department of Radiation and Medical Oncology, Zhongnan Hospital of Wuhan University, Wuhan, China
- Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuhan, China
- Hubei Key Laboratory of Tumor Biology Behaviors, Zhongnan Hospital of Wuhan University, Wuhan, China
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8
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Schrank Z, Khan N, Osude C, Singh S, Miller RJ, Merrick C, Mabel A, Kuckovic A, Puri N. Oligonucleotides Targeting Telomeres and Telomerase in Cancer. Molecules 2018; 23:molecules23092267. [PMID: 30189661 PMCID: PMC6225148 DOI: 10.3390/molecules23092267] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 08/27/2018] [Accepted: 09/04/2018] [Indexed: 02/07/2023] Open
Abstract
Telomeres and telomerase have become attractive targets for the development of anticancer therapeutics due to their involvement in cancer cell immortality. Currently, several therapeutics have been developed that directly target telomerase and telomeres, such as telomerase inhibitors and G-quadruplex stabilizing ligands. Telomere-specific oligonucleotides that reduce telomerase activity and disrupt telomere architecture are also in development as novel anticancer therapeutics. Specifically, GRN163L and T-oligos have demonstrated promising anticancer activity in multiple cancers types via induction of potent DNA damage responses. Currently, several miRNAs have been implicated in the regulation of telomerase activity and may prove to be valuable targets in the development of novel therapies by reducing expression of telomerase subunits. Targeting miRNAs that are known to increase expression of telomerase subunits may be another strategy to reduce carcinogenesis. This review aims to provide a comprehensive understanding of current oligonucleotide-based anticancer therapies that target telomeres and telomerase. These studies may help design novel therapeutic approaches to overcome the challenges of oligonucleotide therapy in a clinical setting.
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Affiliation(s)
- Zachary Schrank
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, USA.
| | - Nabiha Khan
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, USA.
| | - Chike Osude
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, USA.
| | - Sanjana Singh
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, USA.
| | - Rachel J Miller
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, USA.
| | - Collin Merrick
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, USA.
| | - Alexander Mabel
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, USA.
| | - Adijan Kuckovic
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, USA.
| | - Neelu Puri
- Department of Biomedical Sciences, University of Illinois College of Medicine at Rockford, Rockford, IL 61107, USA.
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9
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Chhabra G, Wojdyla L, Frakes M, Schrank Z, Leviskas B, Ivancich M, Vinay P, Ganapathy R, Ramirez BE, Puri N. Mechanism of Action of G-Quadruplex-Forming Oligonucleotide Homologous to the Telomere Overhang in Melanoma. J Invest Dermatol 2017; 138:903-910. [PMID: 29203363 DOI: 10.1016/j.jid.2017.11.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Revised: 11/09/2017] [Accepted: 11/13/2017] [Indexed: 12/19/2022]
Abstract
T-oligo, a guanine-rich oligonucleotide homologous to the 3'-telomeric overhang of telomeres, elicits potent DNA-damage responses in melanoma cells; however, its mechanism of action is largely unknown. Guanine-rich oligonucleotides can form G-quadruplexes (G4), which are stabilized by the hydrogen bonding of guanine residues. In this study, we confirmed the G4-forming capabilities of T-oligo using nondenaturing PAGE, nuclear magnetic resonance, and immunofluorescence. Using an anti-G-quadruplex antibody, we showed that T-oligo can form G4 in the nuclei of melanoma cells. Furthermore, using DNase I in a nuclease degradation assay, G4-T-oligo was found to be more stable than single-stranded T-oligo. G4-T-oligo had decreased antiproliferative effects compared with single-stranded T-oligo. However, G4-T-oligo has similar cellular uptake as single-stranded T-oligo, as shown by FACS analysis. Inhibition of JNK, which causes DNA damage-induced apoptosis, partially reversed the antiproliferative activity of T-oligo. T-oligo also inhibited mRNA expression of human telomerase reverse transcriptase, a catalytic subunit of telomerase that was reversed by JNK inhibition. Furthermore, two shelterin complex proteins TRF2/POT1 were found to be up-regulated and bound by T-oligo, suggesting that T-oligo may mediate dissociation of these proteins from the telomere overhang. These studies show that T-oligo can form a G-quadruplex and that the antitumor effects of T-oligo may be mediated through POT1/TRF2 and via human telomerase reverse transcriptase inhibition through JNK activation.
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Affiliation(s)
- Gagan Chhabra
- University of Illinois College of Medicine at Rockford, Rockford, Illinois, USA
| | - Luke Wojdyla
- University of Illinois College of Medicine at Rockford, Rockford, Illinois, USA
| | - Mark Frakes
- University of Illinois College of Medicine at Rockford, Rockford, Illinois, USA
| | - Zachary Schrank
- University of Illinois College of Medicine at Rockford, Rockford, Illinois, USA
| | - Brandon Leviskas
- University of Illinois College of Medicine at Rockford, Rockford, Illinois, USA
| | - Marko Ivancich
- University of Illinois College of Medicine at Rockford, Rockford, Illinois, USA
| | - Pooja Vinay
- University of Illinois College of Medicine at Rockford, Rockford, Illinois, USA
| | | | - Benjamin E Ramirez
- Center for Structural Biology, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Neelu Puri
- University of Illinois College of Medicine at Rockford, Rockford, Illinois, USA.
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10
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Treating Cancer by Targeting Telomeres and Telomerase. Antioxidants (Basel) 2017; 6:antiox6010015. [PMID: 28218725 PMCID: PMC5384178 DOI: 10.3390/antiox6010015] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 02/15/2017] [Accepted: 02/16/2017] [Indexed: 12/22/2022] Open
Abstract
Telomerase is expressed in more than 85% of cancer cells. Tumor cells with metastatic potential may have a high telomerase activity, allowing cells to escape from the inhibition of cell proliferation due to shortened telomeres. Human telomerase primarily consists of two main components: hTERT, a catalytic subunit, and hTR, an RNA template whose sequence is complimentary to the telomeric 5′-dTTAGGG-3′ repeat. In humans, telomerase activity is typically restricted to renewing tissues, such as germ cells and stem cells, and is generally absent in normal cells. While hTR is constitutively expressed in most tissue types, hTERT expression levels are low enough that telomere length cannot be maintained, which sets a proliferative lifespan on normal cells. However, in the majority of cancers, telomerase maintains stable telomere length, thereby conferring cell immortality. Levels of hTERT mRNA are directly related to telomerase activity, thereby making it a more suitable therapeutic target than hTR. Recent data suggests that stabilization of telomeric G-quadruplexes may act to indirectly inhibit telomerase action by blocking hTR binding. Telomeric DNA has the propensity to spontaneously form intramolecular G-quadruplexes, four-stranded DNA secondary structures that are stabilized by the stacking of guanine residues in a planar arrangement. The functional roles of telomeric G-quadruplexes are not completely understood, but recent evidence suggests that they can stall the replication fork during DNA synthesis and inhibit telomere replication by preventing telomerase and related proteins from binding to the telomere. Long-term treatment with G-quadruplex stabilizers induces a gradual reduction in the length of the G-rich 3’ end of the telomere without a reduction of the total telomere length, suggesting that telomerase activity is inhibited. However, inhibition of telomerase, either directly or indirectly, has shown only moderate success in cancer patients. Another promising approach of targeting the telomere is the use of guanine-rich oligonucleotides (GROs) homologous to the 3’ telomere overhang sequence (T-oligos). T-oligos, particularly a specific 11-base oligonucleotide (5’-dGTTAGGGTTAG-3’) called T11, have been shown to induce DNA damage responses (DDRs) such as senescence, apoptosis, and cell cycle arrest in numerous cancer cell types with minimal or no cytostatic effects in normal, non-transformed cells. As a result, T-oligos and other GROs are being investigated as prospective anticancer therapeutics. Interestingly, the DDRs induced by T-oligos in cancer cells are similar to the effects seen after progressive telomere degradation in normal cells. The loss of telomeres is an important tumor suppressor mechanism that is commonly absent in transformed malignant cells, and hence, T-oligos have garnered significant interest as a novel strategy to combat cancer. However, little is known about their mechanism of action. In this review, we discuss the current understanding of how T-oligos exert their antiproliferative effects in cancer cells and their role in inhibition of telomerase. We also discuss the current understanding of telomerase in cancer and various therapeutic targets related to the telomeres and telomerase.
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Engelmann D, Meier C, Alla V, Pützer BM. A balancing act: orchestrating amino-truncated and full-length p73 variants as decisive factors in cancer progression. Oncogene 2014; 34:4287-99. [PMID: 25381823 DOI: 10.1038/onc.2014.365] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 09/24/2014] [Accepted: 09/29/2014] [Indexed: 12/23/2022]
Abstract
p73 is the older sibling of p53 and mimics most of its tumor-suppressor functions. Through alternative promoter usage and splicing, the TP73 gene generates more than two dozen isoforms of which N-terminal truncated DNp73 variants have a decisive role in cancer pathogenesis as they outweigh the positive effects of full-length TAp73 and p53 in acting as a barrier to tumor development. Beyond the prevailing view that DNp73 predominantly counteract cell cycle arrest and apoptosis, latest progress indicates that these isoforms acquire novel functions in epithelial-to-mesenchymal transition, metastasis and therapy resistance. New insight into the mechanisms underlying this behavior reinforced the expectation that DNp73 variants contribute to aggressive cellular traits through both loss of wild-type tumor-suppressor activity and gain-of-function, suggesting an equally important role in cancer progression as mutant p53. In this review, we describe the novel properties of DNp73 in the invasion metastasis cascade and outline the comprehensive p73 regulatome with an emphasis on molecular processes putting TAp73 out of action in advanced tumors. These intriguing insights provoke a new understanding of the acquisition of aggressive traits by cancer cells and may help to set novel therapies for a broad range of metastatic tumors.
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Affiliation(s)
- D Engelmann
- Institute of Experimental Gene Therapy and Cancer Research, Rostock University Medical Center, Rostock, Germany
| | - C Meier
- Institute of Experimental Gene Therapy and Cancer Research, Rostock University Medical Center, Rostock, Germany
| | - V Alla
- Institute of Experimental Gene Therapy and Cancer Research, Rostock University Medical Center, Rostock, Germany
| | - B M Pützer
- Institute of Experimental Gene Therapy and Cancer Research, Rostock University Medical Center, Rostock, Germany
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