1
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Wang ZQ, Zhang ZC, Wu YY, Pi YN, Lou SH, Liu TB, Lou G, Yang C. Bromodomain and extraterminal (BET) proteins: biological functions, diseases, and targeted therapy. Signal Transduct Target Ther 2023; 8:420. [PMID: 37926722 PMCID: PMC10625992 DOI: 10.1038/s41392-023-01647-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 08/23/2023] [Accepted: 09/12/2023] [Indexed: 11/07/2023] Open
Abstract
BET proteins, which influence gene expression and contribute to the development of cancer, are epigenetic interpreters. Thus, BET inhibitors represent a novel form of epigenetic anticancer treatment. Although preliminary clinical trials have shown the anticancer potential of BET inhibitors, it appears that these drugs have limited effectiveness when used alone. Therefore, given the limited monotherapeutic activity of BET inhibitors, their use in combination with other drugs warrants attention, including the meaningful variations in pharmacodynamic activity among chosen drug combinations. In this paper, we review the function of BET proteins, the preclinical justification for BET protein targeting in cancer, recent advances in small-molecule BET inhibitors, and preliminary clinical trial findings. We elucidate BET inhibitor resistance mechanisms, shed light on the associated adverse events, investigate the potential of combining these inhibitors with diverse therapeutic agents, present a comprehensive compilation of synergistic treatments involving BET inhibitors, and provide an outlook on their future prospects as potent antitumor agents. We conclude by suggesting that combining BET inhibitors with other anticancer drugs and innovative next-generation agents holds great potential for advancing the effective targeting of BET proteins as a promising anticancer strategy.
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Affiliation(s)
- Zhi-Qiang Wang
- Department of Gynecology Oncology, Harbin Medical University Cancer Hospital, Harbin, 150086, China
| | - Zhao-Cong Zhang
- Department of Gynecology Oncology, Harbin Medical University Cancer Hospital, Harbin, 150086, China
| | - Yu-Yang Wu
- School of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - Ya-Nan Pi
- Department of Gynecology Oncology, Harbin Medical University Cancer Hospital, Harbin, 150086, China
| | - Sheng-Han Lou
- Department of Colorectal Surgery, Harbin Medical University Cancer Hospital, Harbin, China
| | - Tian-Bo Liu
- Department of Gynecology Oncology, Harbin Medical University Cancer Hospital, Harbin, 150086, China
| | - Ge Lou
- Department of Gynecology Oncology, Harbin Medical University Cancer Hospital, Harbin, 150086, China.
| | - Chang Yang
- Department of Gynecology Oncology, Harbin Medical University Cancer Hospital, Harbin, 150086, China.
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2
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Ali JH, Walter M. Combining old and new concepts in targeting telomerase for cancer therapy: transient, immediate, complete and combinatory attack (TICCA). Cancer Cell Int 2023; 23:197. [PMID: 37679807 PMCID: PMC10483736 DOI: 10.1186/s12935-023-03041-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 08/25/2023] [Indexed: 09/09/2023] Open
Abstract
Telomerase can overcome replicative senescence by elongation of telomeres but is also a specific element in most cancer cells. It is expressed more vastly than any other tumor marker. Telomerase as a tumor target inducing replicative immortality can be overcome by only one other mechanism: alternative lengthening of telomeres (ALT). This limits the probability to develop resistance to treatments. Moreover, telomerase inhibition offers some degree of specificity with a low risk of toxicity in normal cells. Nevertheless, only one telomerase antagonist reached late preclinical studies. The underlying causes, the pitfalls of telomerase-based therapies, and future chances based on recent technical advancements are summarized in this review. Based on new findings and approaches, we propose a concept how long-term survival in telomerase-based cancer therapies can be significantly improved: the TICCA (Transient Immediate Complete and Combinatory Attack) strategy.
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Affiliation(s)
- Jaber Haj Ali
- Institute of Laboratory Medicine, Clinical Chemistry and Pathobiochemistry, Charité Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany
- Institute of Clinical Chemistry and Laboratory Medicine, Universitätsmedizin Rostock, Ernst-Heydemann-Straße 6, 18057, Rostock, Germany
| | - Michael Walter
- Institute of Clinical Chemistry and Laboratory Medicine, Universitätsmedizin Rostock, Ernst-Heydemann-Straße 6, 18057, Rostock, Germany.
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3
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Ali HA, Li Y, Bilal AHM, Qin T, Yuan Z, Zhao W. A Comprehensive Review of BET Protein Biochemistry, Physiology, and Pathological Roles. Front Pharmacol 2022; 13:818891. [PMID: 35401196 PMCID: PMC8990909 DOI: 10.3389/fphar.2022.818891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 01/26/2022] [Indexed: 11/13/2022] Open
Abstract
Epigenetic modifications, specifically acetylation of histone plays a decisive role in gene regulation and transcription of normal cellular mechanisms and pathological conditions. The bromodomain and extraterminal (BET) proteins (BRD2, BRD3, BRD4, and BRDT), being epigenetic readers, ligate to acetylated regions of histone and synchronize gene transcription. BET proteins are crucial for normal cellular processing as they control cell cycle progression, neurogenesis, differentiation, and maturation of erythroids and spermatogenesis, etc. Research-based evidence indicated that BET proteins (mainly BRD4) are associated with numeral pathological ailments, including cancer, inflammation, infections, renal diseases, and cardiac diseases. To counter the BET protein-related pathological conditions, there are some BET inhibitors developed and also under development. BET proteins are a topic of most research nowadays. This review, provides an ephemeral but comprehensive knowledge about BET proteins’ basic structure, biochemistry, physiological roles, and pathological conditions in which the role of BETs have been proven. This review also highlights the current and future approaches to pledge BET protein-related pathologies.
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Affiliation(s)
- Hafiz Akbar Ali
- Affiliated Cancer Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China.,Key Laboratory of Advanced Drug Preparation Technologies, Ministry of Education, School of Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, China
| | - Yalan Li
- Key Laboratory of Advanced Drug Preparation Technologies, Ministry of Education, School of Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, China
| | - Akram Hafiz Muhammad Bilal
- Key Laboratory of Advanced Drug Preparation Technologies, Ministry of Education, School of Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, China
| | - Tingting Qin
- Affiliated Cancer Hospital of Zhengzhou University, Zhengzhou University, Zhengzhou, China
| | - Ziqiao Yuan
- Key Laboratory of Advanced Drug Preparation Technologies, Ministry of Education, School of Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, China
| | - Wen Zhao
- Key Laboratory of Advanced Drug Preparation Technologies, Ministry of Education, School of Pharmaceutical Sciences, Zhengzhou University, Zhengzhou, China.,State Key Laboratory of Esophageal Cancer Prevention and Treatment, Zhengzhou University, Zhengzhou, China
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4
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Gala K, Khattar E. Long non-coding RNAs at work on telomeres: Functions and implications in cancer therapy. Cancer Lett 2021; 502:120-132. [PMID: 33450357 DOI: 10.1016/j.canlet.2020.12.036] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 12/13/2020] [Accepted: 12/29/2020] [Indexed: 12/27/2022]
Abstract
Long non-coding RNAs (lncRNAs) are known to regulate various biological processes including cancer. Cancer cells possess limitless replicative potential which is attained by telomere length maintenance while normal somatic cells have a limited lifespan because their telomeres shorten with every cell division ultimately triggering replicative senescence. Two lncRNAs have been observed to play a key role in telomere length maintenance. First is the lncRNA TERC (telomerase RNA component) which functions as a template for telomeric DNA synthesis in association with telomerase reverse transcriptase (TERT) which serves as the catalytic component. Together they constitute the telomerase complex which functions as a reverse transcriptase to elongate telomeres. Second lncRNA that helps in regulating telomere length is the telomeric repeat-containing RNA (TERRA) which is transcribed from the subtelomeric region and extends to the telomeric region. TERC and TERRA exhibit important functions in cancer with implications in precision oncology. In this review, we discuss various aspects of these important lncRNAs in humans and their role in cancer along with recent advancements in their anticancer therapeutic application.
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Affiliation(s)
- Kavita Gala
- Sunandan Divatia School of Science, SVKM's NMIMS (Deemed to be) University, Mumbai, 400056, Maharashtra, India
| | - Ekta Khattar
- Sunandan Divatia School of Science, SVKM's NMIMS (Deemed to be) University, Mumbai, 400056, Maharashtra, India.
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5
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Alidousty C, Duerbaum N, Wagener-Ryczek S, Baar T, Martelotto LG, Heydt C, Siemanowski J, Holz B, Binot E, Fassunke J, Merkelbach-Bruse S, Wolf J, Kron A, Buettner R, Schultheis AM. Prevalence and potential biological role of TERT amplifications in ALK translocated adenocarcinoma of the lung. Histopathology 2020; 78:578-585. [PMID: 32946634 DOI: 10.1111/his.14256] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Accepted: 09/11/2020] [Indexed: 12/20/2022]
Abstract
AIMS The advent of specific ALK-targeting drugs has radically changed the outcome of patients with ALK translocated non-small-cell lung cancer (NSCLC). However, emerging resistance to treatment with ALK inhibitors in these patients remains a major concern. In previous studies, we analysed two ALK+ patient cohorts (TP53 wild-type/TP53 mutated) in terms of copy number alterations. All patients belonging to the TP53 wild-type group had mainly genetically stable genomes, with one exception showing chromosomal instability and amplifications of several gene loci, including TERT. Here, we aimed to determine the prevalence of TERT amplifications in these ALK+ lung cancer patients by analysing an independent cohort of 109 ALK translocated cases. We further analysed the copy numbers of numerous cancer-relevant genes and other genetic aberrations. METHODS AND RESULTS The prevalence of TERT amplifications was determined by means of FISH analyses. Copy numbers of 87 cancer-relevant genes were determined by NanoString nCounter® technology, FoundationOne® and lung-specific NGS panels in some of these TERT-amplified samples, and clinical data on patients with TERT-amplified tumours were collected. Our data revealed that five (4.6%) of all 109 analysed ALK+ patients harboured amplification of TERT and that these patients had genetically unstable genomes. CONCLUSIONS Our preliminary study shows that ALK+ adenocarcinomas should be evaluated in the context of their genomic background in order to more clearly understand and predict patients' individual course of disease.
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Affiliation(s)
| | - Nicolai Duerbaum
- Institute of Pathology, University Hospital Cologne, Cologne, Germany
| | | | - Till Baar
- Faculty of Medicine, Institute of Medical Statistics and Computational Biology, University of Cologne, Cologne, Germany
| | | | - Carina Heydt
- Institute of Pathology, University Hospital Cologne, Cologne, Germany
| | - Janna Siemanowski
- Institute of Pathology, University Hospital Cologne, Cologne, Germany
| | - Barbara Holz
- Institute of Pathology, University Hospital Cologne, Cologne, Germany
| | - Elke Binot
- Institute of Pathology, University Hospital Cologne, Cologne, Germany
| | - Jana Fassunke
- Institute of Pathology, University Hospital Cologne, Cologne, Germany
| | | | - Jürgen Wolf
- Network Genomic Medicine, Cologne, Germany.,Lung Cancer Group Cologne, Department I of Internal Medicine, University Hospital of Cologne, Cologne, Germany.,Center for Integrated Oncology Koeln Bonn, Cologne, Germany
| | - Anna Kron
- Network Genomic Medicine, Cologne, Germany.,Lung Cancer Group Cologne, Department I of Internal Medicine, University Hospital of Cologne, Cologne, Germany.,Center for Integrated Oncology Koeln Bonn, Cologne, Germany
| | - Reinhard Buettner
- Institute of Pathology, University Hospital Cologne, Cologne, Germany.,Network Genomic Medicine, Cologne, Germany.,Center for Integrated Oncology Koeln Bonn, Cologne, Germany
| | - Anne M Schultheis
- Institute of Pathology, University Hospital Cologne, Cologne, Germany
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6
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Song YS, Park YJ. Mechanisms of TERT Reactivation and Its Interaction with BRAFV600E. Endocrinol Metab (Seoul) 2020; 35:515-525. [PMID: 32981294 PMCID: PMC7520576 DOI: 10.3803/enm.2020.304] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Accepted: 07/27/2020] [Indexed: 12/26/2022] Open
Abstract
The telomerase reverse transcriptase (TERT) gene, which is repressed in most differentiated human cells, can be reactivated by somatic TERT alterations and epigenetic modulations. Moreover, the recruitment, accessibility, and binding of transcription factors also affect the regulation of TERT expression. Reactivated TERT contributes to the development and progression of cancer through telomere lengthening-dependent and independent ways. In particular, because of recent advances in high-throughput sequencing technologies, studies on genomic alterations in various cancers that cause increased TERT transcriptional activity have been actively conducted. TERT reactivation has been reported to be associated with poor prognosis in several cancers, and TERT promoter mutations are among the most potent prognostic markers in thyroid cancer. In particular, when a TERT promoter mutation coexists with the BRAFV600E mutation, these mutations exert synergistic effects on a poor prognosis. Efforts have been made to uncover the mechanisms of these synergistic interactions. In this review, we discuss the role of TERT reactivation in tumorigenesis, the mechanisms of TERT reactivation across all human cancers and in thyroid cancer, and the mechanisms of interactions between BRAFV600E and TERT promoter mutations.
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Affiliation(s)
- Young Shin Song
- Department of Internal Medicine, CHA Bundang Medical Center, CHA University School of Medicine, Seongnam, Korea
| | - Young Joo Park
- Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea
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7
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Yang JH, Wu MZ, Wang XB, Wang S, Qiu XS, Wang EH, Wu GP. HPV16 E6/E7 upregulate hTERC mRNA and gene amplification levels by relieving the effect of LKB1 on Sp1 phosphorylation in lung cancer cells. Ther Adv Med Oncol 2020; 12:1758835920917562. [PMID: 32499837 PMCID: PMC7243384 DOI: 10.1177/1758835920917562] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Accepted: 03/04/2020] [Indexed: 11/18/2022] Open
Abstract
Background: There is an immediate need for research on the mechanism underlying
telomerase activation and overexpression. Materials & Methods: A total of 174 patients with lung cancer (n = 106) and
benign lung disease (n = 68) were recruited for the current
study. The mRNA expression levels of E6, E7, LKB1, Sp1, and hTERC in
brushing cells were detected by quantitative reverse transcriptase
polymerase chain reaction (qRT-PCR), and hTERC amplification was also
detected by fluorescence in situ hybridization (FISH). To investigate the
potential mechanism, bidirectional genetic manipulation was performed in
well-established lung cancer cell lines. Results: Our results indicated that the mRNA expression levels of E6, E7, Sp1, and
hTERC and the amplification level of hTERC were significantly increased in
the malignant group compared with those of the benign group
(p < 0.01). Conversely, the mRNA expression level of
LKB1 was significantly decreased in the malignant group
(p < 0.01). The correlation between E6, E7, Sp1, and
hTERC expression was positive but was negative with LKB1
(p < 0.01). Our results also showed that HPV16 E6/E7
downregulated the expression of LKB1 at both the protein and mRNA levels.
The loss of LKB1 upregulated Sp1 expression, and also promoted Sp1 activity.
Sp1 further upregulated hTERC at the mRNA and gene amplification levels.
Thus, we proposed a HPV–LKB1–Sp1–hTERC axis of E6/E7 upregulation of hTERC
expression. Conclusion: We demonstrated for the first time that E6 and E7 promoted hTERC mRNA
expression and the amplification of hTERC by relieving the effect of LKB1 on
the phosphorylation of Sp1. Sp1 further activated hTERC by directly binding
to the promoter regions of hTERC.
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Affiliation(s)
- Jing-Hua Yang
- Department of Pathology, The First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, China
| | - Ming-Zhe Wu
- Department of Gynecology, The First Hospital of China Medical University, Shenyang, China
| | - Xu-Bo Wang
- Department of Pathology, Xuzhou City Hospital of TCM, Nanjing University of Chinese Medicine, Xuzhou, China
| | - Shiyu Wang
- Geisinger Commonwealth School of Medicine, Scranton, PA, USA
| | - Xue-Shan Qiu
- Department of Pathology, The First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, China
| | - En-Hua Wang
- Department of Pathology, The First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, Shenyang, China
| | - Guang-Ping Wu
- Department of Pathology, The First Affiliated Hospital and College of Basic Medical Sciences, China Medical University, No.155 Nanjing Bei Street, Shenyang 110001, China
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8
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Yuan X, Larsson C, Xu D. Mechanisms underlying the activation of TERT transcription and telomerase activity in human cancer: old actors and new players. Oncogene 2019; 38:6172-6183. [PMID: 31285550 PMCID: PMC6756069 DOI: 10.1038/s41388-019-0872-9] [Citation(s) in RCA: 250] [Impact Index Per Article: 50.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2019] [Revised: 06/20/2019] [Accepted: 06/20/2019] [Indexed: 12/25/2022]
Abstract
Long-lived species Homo sapiens have evolved robust protection mechanisms against cancer by repressing telomerase and maintaining short telomeres, thereby delaying the onset of the majority of cancer types until post-reproductive age. Indeed, telomerase is silent in most differentiated human cells, predominantly due to the transcriptional repression of its catalytic component telomerase reverse transcriptase (TERT) gene. The lack of telomerase/TERT expression leads to progressive telomere erosion in dividing human cells, whereas critically shortened telomere length induces a permanent growth arrest stage named replicative senescence. TERT/telomerase activation has been experimentally shown to be essential to cellular immortalization and malignant transformation by stabilizing telomere length and erasing the senescence barrier. Consistently, TERT expression/telomerase activity is detectable in up to 90% of human primary cancers. Compelling evidence has also accumulated that TERT contributes to cancer development and progression via multiple activities beyond its canonical telomere-lengthening function. Given these key roles of telomerase and TERT in oncogenesis, great efforts have been made to decipher mechanisms underlying telomerase activation and TERT induction. In the last two decades since the TERT gene and promoter were cloned, the derepression of the TERT gene has been shown to be achieved typically at a transcriptional level through dysregulation of oncogenic factors or signaling, post-transcriptional/translational regulation and genomic amplification. However, advances in high-throughput next-generation sequencing technologies have prompted a revolution in cancer genomics, which leads to the recent discovery that genomic alterations take center stage in activating the TERT gene. In this review article, we summarize critical mechanisms activating TERT transcription, with special emphases on the contribution of TERT promoter mutations and structural alterations at the TERT locus, and briefly discuss the underlying implications of these genomic events-driven TERT hyperactivity in cancer initiation/progression and potential clinical applications as well.
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Affiliation(s)
- Xiaotian Yuan
- School of Medicine, Shandong University, 250012, Jinan, People's Republic of China. .,Department of Medicine, Center for Molecular Medicine (CMM) and Bioclinicum, Karolinska Institutet and Karolinska University Hospital Solna, 171 64, Solna, Sweden.
| | - Catharina Larsson
- Department of Oncology-Pathology and Bioclinicum, Karolinska Institutet and Karolinska University Hospital Solna, 171 64, Solna, Sweden
| | - Dawei Xu
- Department of Medicine, Center for Molecular Medicine (CMM) and Bioclinicum, Karolinska Institutet and Karolinska University Hospital Solna, 171 64, Solna, Sweden.
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9
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Yaswen P, MacKenzie KL, Keith WN, Hentosh P, Rodier F, Zhu J, Firestone GL, Matheu A, Carnero A, Bilsland A, Sundin T, Honoki K, Fujii H, Georgakilas AG, Amedei A, Amin A, Helferich B, Boosani CS, Guha G, Ciriolo MR, Chen S, Mohammed SI, Azmi AS, Bhakta D, Halicka D, Niccolai E, Aquilano K, Ashraf SS, Nowsheen S, Yang X. Therapeutic targeting of replicative immortality. Semin Cancer Biol 2015; 35 Suppl:S104-S128. [PMID: 25869441 PMCID: PMC4600408 DOI: 10.1016/j.semcancer.2015.03.007] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 03/06/2015] [Accepted: 03/13/2015] [Indexed: 12/15/2022]
Abstract
One of the hallmarks of malignant cell populations is the ability to undergo continuous proliferation. This property allows clonal lineages to acquire sequential aberrations that can fuel increasingly autonomous growth, invasiveness, and therapeutic resistance. Innate cellular mechanisms have evolved to regulate replicative potential as a hedge against malignant progression. When activated in the absence of normal terminal differentiation cues, these mechanisms can result in a state of persistent cytostasis. This state, termed “senescence,” can be triggered by intrinsic cellular processes such as telomere dysfunction and oncogene expression, and by exogenous factors such as DNA damaging agents or oxidative environments. Despite differences in upstream signaling, senescence often involves convergent interdependent activation of tumor suppressors p53 and p16/pRB, but can be induced, albeit with reduced sensitivity, when these suppressors are compromised. Doses of conventional genotoxic drugs required to achieve cancer cell senescence are often much lower than doses required to achieve outright cell death. Additional therapies, such as those targeting cyclin dependent kinases or components of the PI3K signaling pathway, may induce senescence specifically in cancer cells by circumventing defects in tumor suppressor pathways or exploiting cancer cells’ heightened requirements for telomerase. Such treatments sufficient to induce cancer cell senescence could provide increased patient survival with fewer and less severe side effects than conventional cytotoxic regimens. This positive aspect is countered by important caveats regarding senescence reversibility, genomic instability, and paracrine effects that may increase heterogeneity and adaptive resistance of surviving cancer cells. Nevertheless, agents that effectively disrupt replicative immortality will likely be valuable components of new combinatorial approaches to cancer therapy.
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Affiliation(s)
- Paul Yaswen
- Life Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA, United States.
| | - Karen L MacKenzie
- Children's Cancer Institute Australia, Kensington, New South Wales, Australia.
| | | | | | | | - Jiyue Zhu
- Washington State University College of Pharmacy, Pullman, WA, United States.
| | | | | | - Amancio Carnero
- Instituto de Biomedicina de Sevilla, HUVR, Consejo Superior de Investigaciones Cientificas, Universdad de Sevilla, Seville, Spain.
| | | | | | | | | | | | | | - Amr Amin
- United Arab Emirates University, Al Ain, United Arab Emirates; Cairo University, Cairo, Egypt
| | - Bill Helferich
- University of Illinois at Urbana Champaign, Champaign, IL, United States
| | | | - Gunjan Guha
- SASTRA University, Thanjavur, Tamil Nadu, India
| | | | - Sophie Chen
- Ovarian and Prostate Cancer Research Trust, Guildford, Surrey, United Kingdom
| | | | - Asfar S Azmi
- Karmanos Cancer Institute, Wayne State University, Detroit, MI, United States
| | | | | | | | | | - S Salman Ashraf
- United Arab Emirates University, Al Ain, United Arab Emirates; Cairo University, Cairo, Egypt
| | | | - Xujuan Yang
- University of Illinois at Urbana Champaign, Champaign, IL, United States
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10
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Beishline K, Azizkhan-Clifford J. Sp1 and the 'hallmarks of cancer'. FEBS J 2015; 282:224-58. [PMID: 25393971 DOI: 10.1111/febs.13148] [Citation(s) in RCA: 369] [Impact Index Per Article: 41.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 09/26/2014] [Accepted: 11/10/2014] [Indexed: 12/19/2022]
Abstract
For many years, transcription factor Sp1 was viewed as a basal transcription factor and relegated to a role in the regulation of so-called housekeeping genes. Identification of Sp1's role in recruiting the general transcription machinery in the absence of a TATA box increased its importance in gene regulation, particularly in light of recent estimates that the majority of mammalian genes lack a TATA box. In this review, we briefly consider the history of Sp1, the founding member of the Sp family of transcription factors. We review the evidence suggesting that Sp1 is highly regulated by post-translational modifications that positively and negatively affect the activity of Sp1 on a wide array of genes. Sp1 is over-expressed in many cancers and is associated with poor prognosis. Targeting Sp1 in cancer treatment has been suggested; however, our review of the literature on the role of Sp1 in the regulation of genes that contribute to the 'hallmarks of cancer' illustrates the extreme complexity of Sp1 functions. Sp1 both activates and suppresses the expression of a number of essential oncogenes and tumor suppressors, as well as genes involved in essential cellular functions, including proliferation, differentiation, the DNA damage response, apoptosis, senescence and angiogenesis. Sp1 is also implicated in inflammation and genomic instability, as well as epigenetic silencing. Given the apparently opposing effects of Sp1, a more complete understanding of the function of Sp1 in cancer is required to validate its potential as a therapeutic target.
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Affiliation(s)
- Kate Beishline
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, USA
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11
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Gao T, Wang J, Yang M, Li H. Transcriptome analysis reveals the effect of oral contraceptive use on cervical cancer. Mol Med Rep 2014; 10:1703-8. [PMID: 25109897 PMCID: PMC4148377 DOI: 10.3892/mmr.2014.2466] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 05/09/2014] [Indexed: 12/25/2022] Open
Abstract
Differentially-expressed genes (DEGs) correlated to oral contraceptives (OCs) were identified by comparing the transcriptomes of cervical cancer patients who have taken OCs and those who have not. Their biological functions and relevance to clinical manifestations were investigated further in order to gain an understanding of the pathogenesis of cervical cancer and provide potential therapeutic targets. Level 3 RNA-sequencing (seq) data for cervical squamous-cell carcinoma and endocervical adenocarcinoma and the clinical information were downloaded from The Cancer Genome Atlas. The present study analyzed the RNA‑seq data and information on OC use of 35 patients [OC users (n=18) and those who have never used OCs (n=17)]. Student's t‑test was used in order to identify DEGs and the false discovery rate (FDR) was estimated by a Beta-Uniform Mixture model, which was adopted in multiple testing corrections. A functional enrichment analysis was performed with the Database for Annotation, Visualization and Integrated Discovery tool and BioCarta. A total of 80 DEGs were identified in OC users while FDR=0.3 was set as the cut-off value. The metabolic process and human telomerase RNA gene transcription were significantly upregulated in DEGs. Furthermore, secreted LY6/PLAUR domain containing 1 was identified to be correlated to the pathological response, while the synapse defective 1 Rho GTPase homolog 2 was found to be significantly associated with the histological grade and overall survival time. In conclusion, present study shed light on the effect of OC use on the oncogenesis of the cervix and may indicate novel approaches for a targeted therapy of cervical cancer.
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Affiliation(s)
- Tian Gao
- Department of Obstetrics and Gynecology, Tongji Hospital, Tongji University, Shanghai 200065, P.R. China
| | - Jianjun Wang
- Department of Obstetrics and Gynecology, Tongji Hospital, Tongji University, Shanghai 200065, P.R. China
| | - Min Yang
- Department of Obstetrics and Gynecology, Women's Hospital School of Medicine, Zhejiang University, Hangzhou 310006, P.R. China
| | - Huaifang Li
- Department of Obstetrics and Gynecology, Tongji Hospital, Tongji University, Shanghai 200065, P.R. China
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12
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Structural Features of the Telomerase RNA Gene in the Naked Mole Rat Heterocephalus glaber. Acta Naturae 2014; 6:41-7. [PMID: 25093110 PMCID: PMC4115225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Telomere length, an important feature of life span control, is dependent on the activity of telomerase (a key enzyme of the telomere-length-maintaining system). Telomerase RNA is a component of telomerase and, thus, is crucial for its activity. The structures of telomerase RNA genes and their promoter regions were compared for the long-living naked mole rat and different organisms. Two rare polymorphisms in Heterocephalus glaber telomerase RNA (hgTER) were identified: A→G in the first loop of pseudoknot P2b-p3 (an equivalent of 111nt in hTR) and G→A in the scaRNA domain CR7-p8b (an equivalent of 421nt in hTR). Analysis of TER promoter regions allowed us to identify two new transcription factor binding sites. The first one is the ETS family site, which was found to be a conserved element for all the analyzed TER promoters. The second site is unique for the promoter region of TER of the naked mole rat and is a binding site for the SOX17 transcription factor. The absence of one Sp1 site in the TER promoter region of the naked small rat is an additional specific feature of the promoter area of hgTER. Such variation in the hgTER transcription regulation region and hgTER itself could provide increased telomerase activity in stem cells and an extended lifespan to H. glaber.
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Characterization of a far upstream located promoter expressing the acetyl-CoA carboxylase-alpha in the brain of cattle. Gene 2013; 515:266-71. [DOI: 10.1016/j.gene.2012.12.033] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 11/29/2012] [Accepted: 12/02/2012] [Indexed: 01/23/2023]
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Shi X, Metges CC, Seyfert HM. Interaction of C/EBP-beta and NF-Y factors constrains activity levels of the nutritionally controlled promoter IA expressing the acetyl-CoA carboxylase-alpha gene in cattle. BMC Mol Biol 2012; 13:21. [PMID: 22738246 PMCID: PMC3441787 DOI: 10.1186/1471-2199-13-21] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 05/16/2012] [Indexed: 11/10/2022] Open
Abstract
Background The enzyme acetyl-CoA carboxylase-alpha (ACC-α) is rate limiting for de novo fatty acid synthesis. Among the four promoters expressing the bovine gene, promoter IA (PIA) is dominantly active in lipogenic tissues. This promoter is in principal repressed but activated under favorable nutritional conditions. Previous analyses already coarsely delineated the repressive elements on the distal promoter but did not resolve the molecular nature of the repressor. Knowledge about the molecular functioning of this repressor is fundamental to understanding the nutrition mediated regulation of PIA activity. We analyzed here the molecular mechanism calibrating PIA activity. Results We finely mapped the repressor binding sites in reporter gene assays and demonstrate together with Electrophoretic Mobility Shift Assays that nuclear factor-Y (NF-Y) and CCAAT/enhancer binding protein-β (C/EBPβ) each separately repress PIA activity by binding to their cognate low affinity sites, located on distal elements of the promoter. Simultaneous binding of both factors results in strongest repression. Paradoxically, over expression of NFY factors, but also - and even more so - of C/EBPβ significantly activated the promoter when bound to high affinity sites on the proximal promoter. However, co-transfection experiments revealed that NF-Y may eventually diminish the strong stimulatory effect of C/EBPβ at the proximal PIA in a dose dependent fashion. We validated by chromatin immunoprecipitation, that NF-Y and C/EBP factors may physically interact. Conclusion The proximal promoter segment of PIA appears to be principally in an active state, since even minute concentrations of both, NF-Y and C/EBPβ factors can saturate the high affinity activator sites. Higher factor concentrations will saturate the low affinity repressive sites on the distal promoter resulting in reduced and calibrated promoter activity. Based on measurements of the mRNA concentrations of those factors in different tissues we propose that the interplay of both factors may set tissue-specific limits for PIA activity.
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Affiliation(s)
- Xuanming Shi
- Research Unit for Molecular Biology, Leibniz Institute for Farm Animal Biology (FBN), Wilhelm-Stahl-Allee 2, D-18196, Dummerstorf, Germany
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15
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Abstract
Mutations in the coding region of telomerase complex genes can result in accelerated telomere attrition and human disease. Manifestations of telomere disease include the bone marrow failure syndromes dyskeratosis congenita and aplastic anemia, acute myeloid leukemia, liver cirrhosis, and pulmonary fibrosis. Here, we describe a mutation in the CCAAT box (GCAAT) of the TERC gene promoter in a family in which multiple members had typical features of telomeropathy. The genetic alteration in this critical regulatory sequence resulted in reduced reporter gene activity and absent binding of transcription factor NF-Y, likely responsible for reduced TERC levels, decreased telomerase activity, and short telomeres. This is the first description of a pathogenic mutation in the highly conserved CCAAT box and the first instance of a mutation in the promoter region of TERC producing a telomeropathy. We propose that current mutation-screening strategies should include gene promoter regions for the diagnosis of telomere diseases. This clinical trial was registered at www.clinicaltrials.gov as #NCT00071045.
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Guo Q, Sui L, Feng Y. Cervical cancer screening: hTERC gene amplification detection by FISH in comparison with conventional methods. ACTA ACUST UNITED AC 2012. [DOI: 10.4236/ojog.2012.21003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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17
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Mild hyperoxia limits hTR levels, telomerase activity, and telomere length maintenance in hTERT-transduced bone marrow endothelial cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:1142-53. [DOI: 10.1016/j.bbamcr.2010.06.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 06/28/2010] [Accepted: 06/28/2010] [Indexed: 01/01/2023]
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Skvortzov DA, Rubzova MP, Zvereva ME, Kiselev FL, Donzova OA. The regulation of telomerase in oncogenesis. Acta Naturae 2009; 1:51-67. [PMID: 22649586 PMCID: PMC3347505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
The influence that the expression of the human (glial-derived neurotrophic factor (GDNF)) neurotrophic factor has on the morphology and proliferative activity of embryonic stem cells (SC) of a mouse with R1 lineage, as well as their ability to form embroid bodies (EB), has been studied. Before that, using a PCR (polymerase chain reaction) coupled with reverse transcription, it was shown that, in this very lineage of the embryonic SC, the expression of the receptors' genes is being fulfilled for the neurotropfic RET and GFRα1 glia factor. The mouse's embryonic SC lineage has been obtained, transfected by the human GDNF gene, and has been fused with the "green" fluorescent protein (GFP) gene. The presence of the expression of the human GDNF gene in the cells was shown by northern hybridization and the synthesis of its albuminous product by immunocitochemical coloration with the use of specific antibodies. The reliable slowing-down of the embriod-body formation by the embryonic SC transfected by the GDNF gene has been shown. No significant influence of the expression of the GDNF gene on the morphology and the proliferative activity of the transfected embryonic SCs has been found when compared with the control ones.
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Affiliation(s)
- D A Skvortzov
- Department of Chemistry, Moscow State University, 119992 Moscow
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Liu L, Ishihara K, Ichimura T, Fujita N, Hino S, Tomita S, Watanabe S, Saitoh N, Ito T, Nakao M. MCAF1/AM is involved in Sp1-mediated maintenance of cancer-associated telomerase activity. J Biol Chem 2008; 284:5165-74. [PMID: 19106100 DOI: 10.1074/jbc.m807098200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Telomerase maintains telomere length and is implicated in senescence and immortalization of mammalian cells. Two essential components for this enzyme are telomerase reverse transcriptase (TERT) and the telomerase RNA component (encoded by the TERC gene). These telomerase subunit genes are known to be mainly expressed by specificity protein 1 (Sp1). MBD1-containing chromatin-associated factor 1 (MCAF1), also known as ATFa-associated modulator (AM) and activating transcription factor 7-interacting protein (ATF7IP), mediates gene regulation, although the precise function of MCAF1 remains to be elucidated. Here, we report that MCAF1 is involved in Sp1-dependent maintenance of telomerase activity in cancer cells. Two evolutionarily conserved domains of MCAF1 directly interact with Sp1 and the general transcriptional apparatus. Selective depletion of MCAF1 or Sp1 down-regulates TERT and TERC genes in cultured cells, which results in decreased telomerase activity. The transcriptionally active form of RNA polymerase II and the general transcription factor ERCC3 decreased in the TERT promoter under the loss of MCAF1 or Sp1. Consistently, MCAF1 is found to be frequently overexpressed in naturally occurring cancers that originate in different tissues. Our data suggest that transcriptional function of MCAF1 facilitates telomerase expression by Sp1, which may be a common mechanism in proliferative cancer cells.
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Affiliation(s)
- Lifeng Liu
- Department of Regeneration Medicine, Institute of Molecular Embryology and Genetics, Kumamoto University, 2-2-1 Honjo, Kumamoto 860-0811, Japan
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20
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Cairney CJ, Hoare SF, Daidone MG, Zaffaroni N, Keith WN. High level of telomerase RNA gene expression is associated with chromatin modification, the ALT phenotype and poor prognosis in liposarcoma. Br J Cancer 2008; 98:1467-74. [PMID: 18414473 PMCID: PMC2361713 DOI: 10.1038/sj.bjc.6604328] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Telomere length is maintained by two known mechanisms, activation of telomerase or alternative lengthening of telomeres (ALT). The ALT pathway is more commonly activated in tumours of mesenchymal origin, although the mechanisms involved in the decision of a cell to activate either telomerase or ALT are unknown at present and no molecular markers exist to define the ALT phenotype. We have previously shown an association between chromatin remodelling, telomerase gene expression and ALT in cell line models. Here, we evaluate these findings and investigate their prognostic significance in a panel of liposarcoma tissue samples to understand the biology underlying the ALT phenotype. Liposarcoma samples were split into three groups: telomerase positive (Tel+); ALT positive; ALT−/Tel−. Differences in telomerase gene expression were evident between the groups with increased expression of hTR in ALT and Tel+ compared to ALT−/Tel− samples and increased hTERT in Tel+ samples only. Investigation of a small panel of chromatin modifications revealed significantly increased binding of acetyl H3 in association with hTR expression. We confirm that the presence of the ALT phenotype is associated with poor prognosis and in addition, for the first time, we show a direct association between hTR expression and poor prognosis in liposarcoma patients.
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Affiliation(s)
- C J Cairney
- Centre for Oncology and Applied Pharmacology, University of Glasgow, Cancer Research UK Beatson Laboratories, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
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21
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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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22
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Zimmermann S, Martens UM. Telomeres, senescence, and hematopoietic stem cells. Cell Tissue Res 2007; 331:79-90. [PMID: 17960423 DOI: 10.1007/s00441-007-0469-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2007] [Accepted: 07/10/2007] [Indexed: 01/01/2023]
Abstract
The replicative lifespan of normal somatic cells is restricted by the erosion of telomeres, which are protective caps at the ends of linear chromosomes. The loss of telomeres induces antiproliferative signals that eventually lead to cellular senescence. The enzyme complex telomerase can maintain telomeres, but its expression is confined to highly proliferative cells such as stem cells and tumor cells. The immense regenerative capacity of the hematopoietic system is provided by a distinct type of adult stem cell: hematopoietic stem cells (HSCs). Although blood cells have to be produced continuously throughout life, the HSC pool seems not to be spared by aging processes. Indeed, limited expression of telomerase is not sufficient to prevent telomere shortening in these cells, which is thought ultimately to limit their proliferative capacity. In this review, we discuss the relevance of telomere maintenance for the hematopoietic stem cell compartment and consider potential functions of telomerase in this context. We also present possible clinical applications of telomere manipulation in HSCs and new insights affecting the aging of the hematopoietic stem cell pool and replicative exhaustion.
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Affiliation(s)
- Stefan Zimmermann
- Department of Hematology/Oncology, Freiburg University Medical Center, Hugstetterstrasse 55, 79106, Freiburg, Germany.
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23
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Shkreli M, Dambrine G, Soubieux D, Kut E, Rasschaert D. Involvement of the oncoprotein c-Myc in viral telomerase RNA gene regulation during Marek's disease virus-induced lymphomagenesis. J Virol 2007; 81:4848-57. [PMID: 17314164 PMCID: PMC1900149 DOI: 10.1128/jvi.02530-06] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Marek's disease virus (MDV) is an alphaherpesvirus that induces a highly malignant T-lymphoma in chickens. The viral genome encodes two identical copies of a viral telomerase RNA subunit (vTR) that exhibits 88% sequence identity to its chicken ortholog chTR. The minimal telomerase ribonucleoprotein complex consists of a protein subunit with reverse transcriptase activity (TERT) and an RNA subunit (TR). The active complex compensates for the progressive telomere shortening that occurs during mitosis and is involved in the cell immortalization process. We show here that the upregulation of telomerase activity is associated with an increase in vTR gene expression in chickens infected with the highly oncogenic MDV strain RB-1B. A comparative functional analysis of the viral and chicken TR promoters, based on luciferase reporter assays, revealed that the vTR promoter was up to threefold more efficient than the chTR promoter in avian cells. We demonstrated, by directed mutagenesis of the vTR promoter region, that the stronger transcriptional activity of the vTR promoter resulted largely from an E-box located two nucleotides downstream from the transcriptional start site of the vTR gene. Furthermore, transactivation assays and chromatin immunoprecipitation assays demonstrated the involvement of the c-Myc oncoprotein in the transcriptional regulation of vTR. Finally, an Ets binding site was specifically implicated in the transcriptional regulation of vTR in the MDV-transformed lymphoblastoid cell line MSB-1.
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Affiliation(s)
- Marina Shkreli
- Equipe Télomérase et Lymphome Viro-Induit, Centre INRA de Tours, Unité IASP 213, 37380 Nouzilly, France
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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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25
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Alonso MM, Fueyo J, Shay JW, Aldape KD, Jiang H, Lee OH, Johnson DG, Xu J, Kondo Y, Kanzawa T, Kyo S, Bekele BN, Zhou X, Nigro J, McDonald JM, Yung WKA, Gomez-Manzano C. Expression of transcription factor E2F1 and telomerase in glioblastomas: mechanistic linkage and prognostic significance. J Natl Cancer Inst 2005; 97:1589-600. [PMID: 16264179 DOI: 10.1093/jnci/dji340] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Several tumor suppressor pathways have been identified as modulators of telomerase function. We examined the functional role of the retinoblastoma-E2F1 pathway in regulating telomerase activity in malignant gliomas. METHODS Adenovirus vectors were used to transfer cDNAs into human glioblastoma and sarcoma cells. Telomerase activity was assessed with a telomere repeat amplification protocol. Promoter activity in cancer cells was assessed with promoter-luciferase reporter constructs. Promoter binding was assessed with the chromatin immunoprecipitation (ChIP) assay. We isolated astrocytes from E2F1 transgenic mice and normal mice for in vivo studies. We evaluated the expression of E2F1 and hTERT (the catalytic subunit of human telomerase) mRNAs by reverse transcriptase-polymerase chain reaction and proteins in human glioblastoma samples by immunoblot analysis. Associations between survival among 61 glioblastoma multiforme patients and expression of E2F1 and hTERT mRNA and protein were examined with Kaplan-Meier analysis, the log-rank test, and Cox proportional hazards regression models. All statistical tests were two-sided. RESULTS Ectopic E2F1 expression increased hTERT promoter activity in cancer cells. We detected an interaction between E2F1 protein and the hTERT promoter. Transgenic E2F1 astrocytes contained functional telomerase protein. E2F1 mRNA expression and hTERT mRNA expression were statistically significantly correlated in human glioblastoma specimens (R = .8; P < .001). Longer median survival was statistically significantly associated with lower E2F1 mRNA expression in tumors (103.6 weeks) rather than with higher expression (46.1 weeks) (difference = 57.5 weeks; 95% confidence interval [CI] = 14.7 to 159.7; log-rank P = .002). E2F1 mRNA was the only factor that was statistically significantly associated with overall survival in a multivariable model (P = .04). Among 27 patients with glioblastoma multiforme samples, the expression of E2F1 protein was statistically significantly associated with survival (log-rank P < .001). CONCLUSIONS E2F1 may participate in telomerase activity regulation in malignant glioma cells. Its expression appears to be strongly associated with the survival of patients with malignant brain tumors.
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Affiliation(s)
- Marta M Alonso
- Department of Neuro-Oncology, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
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Glasspool RM, Burns S, Hoare SF, Svensson C, Keith WN. The hTERT and hTERC telomerase gene promoters are activated by the second exon of the adenoviral protein, E1A, identifying the transcriptional corepressor CtBP as a potential repressor of both genes. Neoplasia 2005; 7:614-22. [PMID: 16036112 PMCID: PMC1501281 DOI: 10.1593/neo.04766] [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] [Received: 12/08/2004] [Revised: 02/17/2005] [Accepted: 02/21/2005] [Indexed: 12/25/2022] Open
Abstract
Telomerase plays a role in the unlimited replicative capacity of the majority of cancer cells and provides a potential anticancer target. The regulation of telomerase is complex but transcriptional control of its two essential components, hTERC (RNA component) and hTERT (reverse transcriptase component), is of major importance. To investigate this further, we have used the adenoviral protein, E1A, as a tool to probe potential pathways involved in the control of telomerase transcription. The second exon of the adenoviral protein E1A activates both telomerase gene promoters in transient transfections. The corepressor, C terminal binding protein, is one of only two proteins known to bind to this region, and we propose that E1A activates both promoters by sequestering CtBP, thereby relieving repression. Activation by exon 2 of E1A involves the SP1 sites in both promoters, and consistent with this, SP1 and CtBP interact in coimmunoprecipitation studies. Modulation of the chromatin environment has been implicated in the regulation of hTERT transcription and appears to involve the SP1 sites. CtBP can be found within a histone-modifying complex and it is possible that a CtBP complex, associating with the SP1 sites, represses transcription from the telomerase promoters by modifying chromatin structure.
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Affiliation(s)
- Rosalind M Glasspool
- Cancer Research UK Centre for Oncology and Applied Pharmacology, University of Glasgow, Cancer Research UK Beatson Laboratories, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
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Zhu J, Zhang Y, Joe GJ, Pompetti R, Emerson SG. NF-Ya activates multiple hematopoietic stem cell (HSC) regulatory genes and promotes HSC self-renewal. Proc Natl Acad Sci U S A 2005; 102:11728-33. [PMID: 16081537 PMCID: PMC1187979 DOI: 10.1073/pnas.0503405102] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Hematopoietic stem cell (HSC) self-renewal and differentiation are influenced through multiple pathways, including homeobox transcription factors, signaling through beta-catenin and Notch-1, telomerase, and p27. How these multiple pathways interact and are orchestrated is currently unknown. We now report that NF-Ya, the regulatory and DNA-binding subunit of the trimeric transcription factor NF-Y, plays a central, integrating role in several of these HSC pathways. NF-Ya is preferentially expressed in HSC-enriched bone marrow subpopulations, and NF-Ya mRNA rapidly declines with HSC differentiation. Overexpression of NF-Ya in primitive hematopoietic cells activates the transcription of multiple HOX4 paralogs, as well as Notch-1, LEF-1, and telomerase RNA. HSCs overexpressing NF-Ya are biased toward primitive hematopoiesis in vitro and show strikingly increased in vivo repopulating abilities after single or sequential bone marrow transplantation. Thus, NF-Ya is a potent cellular regulator of HSC self-renewal.
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Affiliation(s)
- Jiang Zhu
- Department of Medicine, and Abramson Cancer Center, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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Prandini MH, Dreher I, Bouillot S, Benkerri S, Moll T, Huber P. The human VE-cadherin promoter is subjected to organ-specific regulation and is activated in tumour angiogenesis. Oncogene 2005; 24:2992-3001. [PMID: 15735710 PMCID: PMC2800996 DOI: 10.1038/sj.onc.1208483] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Vascular endothelial (VE)-cadherin is exclusively expressed at interendothelial junctions of normal and tumour vessels. In this report, we characterized the transcriptional activity of the human VE-cadherin promoter. Transient transfection assays revealed that sequences at positions --1135/-744 and -166/-5 base pairs are critical for promoter activity in endothelial cells. We show that specific sequences in the proximal region interact with Ets and Sp1 family members. Transgenic mice were created and the human VE-cadherin promoter was able to confer correct temporal and spatial expression on the LacZ gene in embryos. In adults, the transgene was specifically and strongly expressed in the lung, heart, ovary, spleen and kidney glomeruli, whereas expression was weak or absent in the vasculature of other organs, including the brain, thymus, liver and skeletal muscle. Neovessels in tumour grafts and Matrigel implants harboured strong stainings, indicating that promoter activity is enhanced in angiogenic situations. Furthermore, Matrigel and transfection assays showed that VE-cadherin promoter is subjected to bFGF induction. Transgene expression was also noticed in extravascular sites of the central nervous system, suggesting that silencer elements may be located elsewhere in the gene. These results are a first step towards addressing the organ- and tumour-specific regulation of the VE-cadherin gene.
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Affiliation(s)
- Marie-Hélène Prandini
- Laboratoire de développement et vieillissement de l'endothélium
INSERM : EMI0219CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble IFR
| | | | - Stéphanie Bouillot
- Laboratoire de développement et vieillissement de l'endothélium
INSERM : EMI0219CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble IFR
| | - Souhila Benkerri
- Laboratoire de développement et vieillissement de l'endothélium
INSERM : EMI0219CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble IFR
| | | | - Philippe Huber
- Laboratoire de développement et vieillissement de l'endothélium
INSERM : EMI0219CEA : DSV/IRTSVUniversité Joseph Fourier - Grenoble IFR
- * Correspondence should be adressed to: Philippe Huber
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MDM2 negatively regulates the human telomerase RNA gene promoter. BMC Cancer 2005; 5:6. [PMID: 15656906 PMCID: PMC546012 DOI: 10.1186/1471-2407-5-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2004] [Accepted: 01/18/2005] [Indexed: 12/28/2022] Open
Abstract
Background We have previously demonstrated that NF-Y and Sp1 interact with the human telomerase RNA (hTR) promoter and play a central role in its regulation. We have also shown that pRB activates the hTR promoter, but the mechanism of pRb directed activation is unknown. It has recently been reported that pRB induces Sp1 activity by relieving inhibition mediated by mdm2. The aim was to investigate possible roles for mdm2 in hTR promoter regulation. Methods Chromatin immunoprecipitation was used to determine binding of mdm2 to the hTR promoter. Transfection and luciferase assays were used to investigate mdm2 repression of the promoter activity and interaction with known transcriptional modulators. Results Here we show using chromatin immunoprecipitation that mdm2 specifically binds the hTR promoter in vivo. Transient co-transfection experiments using an hTR promoter luciferase reporter construct show that hTR promoter activity is inhibited by over-expression of mdm2 in 5637 bladder carcinoma cells (p53 and pRB negative, low mdm2). Titration of mdm2 was able to antagonise activation of hTR promoter activity mediated by pRB or Sp1 over-expression, although in the presence of pRB, mdm2 could not repress promoter activity below basal levels. Using an Sp1 binding site mutation construct we showed that mdm2 repression did not absolutely require Sp1 binding sites in the hTR promoter, suggesting the possibility of pRB/Sp1 independent mechanisms of repression. Finally, we show that NF-Y mediated transactivation of the hTR promoter was also suppressed by mdm2 in a dose-dependent manner. Conclusions These studies suggest that mdm2 may inhibit the hTR promoter by multiple mechanisms. Mdm2 may directly repress activation by both pRB and Sp1, or activation by NF-Y. Furthermore, the ability of mdm2 to interact and interfere with components of the general transcription machinery might partly explain the general repressive effect seen here. Elucidation of new regulators affecting hTR basal promoter activity in cancer cells provides a basis for future studies aimed at improving our understanding of the differential hTR expression between normal and cancer cells.
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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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Argyle DJ, McKevitt T, Gault E, Nasir L. Evaluation of telomerase-targeted therapies in canine cancer cell lines. Vet Comp Oncol 2004; 2:214-21. [DOI: 10.1111/j.1476-5810.2004.00054.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Keith WN, Vulliamy T, Zhao J, Ar C, Erzik C, Bilsland A, Ulku B, Marrone A, Mason PJ, Bessler M, Serakinci N, Dokal I. A mutation in a functional Sp1 binding site of the telomerase RNA gene (hTERC) promoter in a patient with Paroxysmal Nocturnal Haemoglobinuria. BMC HEMATOLOGY 2004; 4:3. [PMID: 15212690 PMCID: PMC442127 DOI: 10.1186/1471-2326-4-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Accepted: 06/22/2004] [Indexed: 11/14/2022]
Abstract
Background Mutations in the gene coding for the RNA component of telomerase, hTERC, have been found in autosomal dominant dyskeratosis congenita (DC) and aplastic anemia. Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal blood disorder associated with aplastic anemia and characterized by the presence of one or more clones of blood cells lacking glycosylphosphatidylinositol (GPI) anchored proteins due to a somatic mutation in the PIGA gene. Methods We searched for mutations in DNA extracted from PNH patients by amplification of the hTERC gene and denaturing high performance liquid chromatography (dHPLC). After a mutation was found in a potential transcription factor binding site in one patient electrophoretic mobility shift assays were used to detect binding of transcription factors to that site. The effect of the mutation on the function of the promoter was tested by transient transfection constructs in which the promoter is used to drive a reporter gene. Results Here we report the finding of a novel promoter mutation (-99C->G) in the hTERC gene in a patient with PNH. The mutation disrupts an Sp1 binding site and destroys its ability to bind Sp1. Transient transfection assays show that mutations in this hTERC site including C-99G cause either up- or down-regulation of promoter activity and suggest that the site regulates core promoter activity in a context dependent manner in cancer cells. Conclusions These data are the first report of an hTERC promoter mutation from a patient sample which can modulate core promoter activity in vitro, raising the possibility that the mutation may affect the transcription of the gene in hematopoietic stem cells in vivo, and that dysregulation of telomerase may play a role in the development of bone marrow failure and the evolution of PNH clones.
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Affiliation(s)
- W Nicol Keith
- Cancer Research UK, Department of Medical Oncology, Cancer Research UK Beatson Laboratories, University of Glasgow, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Tom Vulliamy
- Department of Haematology-Division of Investigative Science, Imperial College London, Hammersmith Hospital, London, UK
| | - Jiangqin Zhao
- Cancer Research UK, Department of Medical Oncology, Cancer Research UK Beatson Laboratories, University of Glasgow, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Cem Ar
- Department of Haematology, Cerrahpasa Medical Faculty, Istanbul University, Turkey
| | - Can Erzik
- Medical Faculty, Marmara University, Turkey
| | - Alan Bilsland
- Cancer Research UK, Department of Medical Oncology, Cancer Research UK Beatson Laboratories, University of Glasgow, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK
| | - Birsen Ulku
- Department of Haematology, Cerrahpasa Medical Faculty, Istanbul University, Turkey
| | - Anna Marrone
- Department of Haematology-Division of Investigative Science, Imperial College London, Hammersmith Hospital, London, UK
| | - Philip J Mason
- Department of Haematology-Division of Investigative Science, Imperial College London, Hammersmith Hospital, London, UK
- Department of Internal Medicine, Division of Hematology, Washington University School of Medicine, St.Louis, MO, 63110, USA
| | - Monica Bessler
- Department of Internal Medicine, Division of Hematology, Washington University School of Medicine, St.Louis, MO, 63110, USA
| | - Nedime Serakinci
- Department of Human Genetics, Bartholin Building, University of Aarhus, Universitetsparken, 8000 Aarhus C, Denmark
| | - Inderjeet Dokal
- Department of Haematology-Division of Investigative Science, Imperial College London, Hammersmith Hospital, London, UK
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Zhao J, Bilsland A, Hoare SF, Keith WN. Involvement of NF-Y and Sp1 binding sequences in basal transcription of the human telomerase RNA gene. FEBS Lett 2003; 536:111-9. [PMID: 12586348 DOI: 10.1016/s0014-5793(03)00038-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The proximal promoter of the telomerase RNA gene, hTR, contains four Sp1 sites and one CCAAT box. We have carried out a functional analysis of the role of these sequence elements. Two Sp1 sites downstream of the CCAAT box mediated negative regulation, while the other two Sp1 sites were positive regulators with the strongest effect mediated by the negative regulatory Sp1 site closely flanking the CCAAT box. Basal transcriptional activity is maintained via the CCAAT box even when all four Sp1 sites are mutated, suggesting nuclear factor-Y (NF-Y) is a fundamental regulator of hTR promoter function. Chromatin immunoprecipitation revealed binding of NF-Y, Sp1 and TFIIB to the promoter in vivo. Thus the interaction of NF-Y at the CCAAT box is pivotal to hTR gene transcription and surrounding sequence elements may provide an environment for the regulation of activity through recruitment of additional protein complexes.
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Affiliation(s)
- Jiangqin Zhao
- Cancer Research UK Department of Medical Oncology, University of Glasgow, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
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Bilsland AE, Anderson CJ, Fletcher-Monaghan AJ, McGregor F, Evans TRJ, Ganly I, Knox RJ, Plumb JA, Keith WN. Selective ablation of human cancer cells by telomerase-specific adenoviral suicide gene therapy vectors expressing bacterial nitroreductase. Oncogene 2003; 22:370-80. [PMID: 12545158 DOI: 10.1038/sj.onc.1206168] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Reactivation of telomerase maintains telomere function and is considered critical to immortalization in most human cancer cells. Elevation of telomerase expression in cancer cells is highly specific: transcription of both RNA (hTR) and protein (hTERT) components is strongly upregulated in cancer cells relative to normal cells. Therefore, telomerase promoters may be useful in cancer gene therapy by selectively expressing suicide genes in cancer cells and not normal cells. One example of suicide gene therapy is the bacterial nitroreductase (NTR) gene, which bioactivates the prodrug CB1954 into an active cytotoxic alkylating agent. We describe construction of adenovirus vectors harbouring the bacterial NTR gene under control of the hTR or hTERT promoters. Western blot analysis of NTR expression in normal and cancer cells infected with adenoviral vectors showed cancer cell-specific nitroreductase expression. Infection with adenoviral telomerase-NTR constructs in a panel of seven cancer cell lines resulted in up to 18-fold sensitization to the prodrug CB1954, an effect that was retained in two drug-resistant ovarian lines. Importantly, no sensitization was observed with either promoter in any of the four normal cell strains. Finally, an efficacious effect was observed in cervical and ovarian xenograft models following single intratumoural injection with low doses of vector, followed by injection with CB1954.
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Affiliation(s)
- Alan E Bilsland
- Cancer Research UK Department of Medical Oncology, University of Glascow, Cancer Research UK Beatson Laboratories, Bearsden, UK
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Fajkus J, Simícková M, Maláska J. Tiptoeing to chromosome tips: facts, promises and perils of today's human telomere biology. Philos Trans R Soc Lond B Biol Sci 2002; 357:545-62. [PMID: 12028791 PMCID: PMC1692969 DOI: 10.1098/rstb.2001.1053] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The past decade has witnessed an explosion of knowledge concerning the structure and function of chromosome terminal structures-telomeres. Today's telomere research has advanced from a pure descriptive approach of DNA and protein components to an elementary understanding of telomere metabolism, and now to promising applications in medicine. These applications include 'passive' ones, among which the use of analysis of telomeres and telomerase (a cellular reverse transcriptase that synthesizes telomeres) for cancer diagnostics is the best known. The 'active' applications involve targeted downregulation or upregulation of telomere synthesis, either to mortalize immortal cancer cells, or to rejuvenate mortal somatic cells and tissues for cellular transplantations, respectively. This article reviews the basic data on structure and function of human telomeres and telomerase, as well as both passive and active applications of human telomere biology.
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Affiliation(s)
- J Fajkus
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Královopolská 135, CZ-612 65 Brno, Czech Republic.
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Plumb JA, Bilsland A, Kakani R, Zhao J, Glasspool RM, Knox RJ, Evans TR, Keith WN. Telomerase-specific suicide gene therapy vectors expressing bacterial nitroreductase sensitize human cancer cells to the pro-drug CB1954. Oncogene 2001; 20:7797-803. [PMID: 11753658 DOI: 10.1038/sj.onc.1204954] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2001] [Revised: 08/31/2001] [Accepted: 09/04/2001] [Indexed: 12/30/2022]
Abstract
Telomerase activation is considered to be a critical step in cancer progression due to its role in cellular immortalization. The prevalence of telomerase expression in human cancers makes it an attractive candidate for new mechanism-based targets for cancer therapy. The selective killing of cancer cells can be achieved by gene-directed enzyme pro-drug therapy (GDEPT). In this study we have tested the feasibility of using the transcriptional regulatory sequences from the hTERT and hTR genes to regulate expression of the bacterial nitroreductase enzyme in combination with the pro-drug CB1954 in a suicide gene therapy strategy. hTERT and hTR promoter activity was compared in a panel of 10 cell lines and showed a wide distribution in activity; low activity was observed in normal cells and telomerase-negative immortal ALT cell lines, with up to 300-fold higher activity observed in telomerase positive cancer lines. Placing the nitroreductase gene under the control of the telomerase gene promoters sensitized cancer cells in tissue culture to the pro-drug CB1954 and promoter activity was predictive of sensitization to the pro-drug (2-20-fold sensitization), with cell death restricted to lines exhibiting high levels of promoter activity. The in vivo relevance of these data was tested using two xenograft models (C33a and GLC4 cells). Significant tumour reduction was seen with both telomerase promoters and the promoter-specific patterns of sensitization observed in tissue culture were retained in xenograft models. Thus, telomerase-specific suicide gene therapy vectors expressing bacterial nitroreductase sensitize human cancer cells to the pro-drug CB1954.
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Affiliation(s)
- J A Plumb
- CRC Department of Medical Oncology, University of Glasgow, CRC Beatson Laboratories, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, UK
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Keith WN, Jeffry Evans TR, Glasspool RM. Telomerase and cancer: time to move from a promising target to a clinical reality. J Pathol 2001; 195:404-14. [PMID: 11745671 DOI: 10.1002/path.1001] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The past 25 years have seen unparalleled advances in our understanding of the molecular basis of cancer. As a result, novel molecular targets have been identified that provide great potential for the development of new cancer diagnostics and therapies. Four key features of cancer cells distinguish them from their normal counterparts: loss of cell-cycle regulation, loss of control over invasion and metastasis, failure of apoptotic mechanisms, and bypass of senescence. This review examines our understanding of the bypass of senescence and the process of immortalization during carcinogenesis. In addition, the realistic opportunities for telomerase in cancer diagnostics and the challenges faced in clinical trial design for telomerase therapeutics are discussed.
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Affiliation(s)
- W N Keith
- CRC Department of Medical Oncology, University of Glasgow, CRC Beatson Laboratories, Garscube Estate, Switchback Road, Glasgow G61 1BD, UK.
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