1
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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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2
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Bajaj S, Kumar MS, Peters GJ, Mayur YC. Targeting telomerase for its advent in cancer therapeutics. Med Res Rev 2020; 40:1871-1919. [PMID: 32391613 DOI: 10.1002/med.21674] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Revised: 04/19/2020] [Accepted: 04/21/2020] [Indexed: 12/24/2022]
Abstract
Telomerase has emerged as an important primary target in anticancer therapy. It is a distinctive reverse transcriptase enzyme, which extends the length of telomere at the 3' chromosomal end, and uses telomerase reverse transcriptase (TERT) and telomerase RNA template-containing domains. Telomerase has a vital role and is a contributing factor in human health, mainly affecting cell aging and cell proliferation. Due to its unique feature, it ensures unrestricted cell proliferation in malignancy and plays a major role in cancer disease. The development of telomerase inhibitors with increased specificity and better pharmacokinetics is being considered to design and develop newer potent anticancer agents. Use of natural and synthetic compounds for the inhibition of telomerase activity can lead to an opening of new vistas in cancer treatment. This review details about the telomerase biochemistry, use of natural and synthetic compounds; vaccines and oncolytic virus in therapy that suppress the telomerase activity. We have discussed structure-activity relationships of various natural and synthetic telomerase inhibitors to help medicinal chemists and chemical biology researchers with a ready reference and updated status of their clinical trials. Suppression of human TERT (hTERT) activity through inhibition of hTERT promoter is an important approach for telomerase inhibition.
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Affiliation(s)
| | | | - G J Peters
- Department of Medical Oncology, VU University Medical Centre, Amsterdam, The Netherlands
| | - Y C Mayur
- SPPSPTM, SVKM's NMIMS, Mumbai, India
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3
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Rossi M, Gorospe M. Noncoding RNAs Controlling Telomere Homeostasis in Senescence and Aging. Trends Mol Med 2020; 26:422-433. [PMID: 32277935 DOI: 10.1016/j.molmed.2020.01.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Revised: 12/23/2019] [Accepted: 01/21/2020] [Indexed: 12/12/2022]
Abstract
Aging is a universal and time-dependent biological decline associated with progressive deterioration of cells, tissues, and organs. Age-related decay can eventually lead to pathology such as cardiovascular and neurodegenerative diseases, cancer, and diabetes. A prominent molecular process underlying aging is the progressive shortening of telomeres, the structures that protect the ends of chromosomes, eventually triggering cellular senescence. Noncoding (nc)RNAs are emerging as major regulators of telomere length homeostasis. In this review, we describe the impact of ncRNAs on telomere function and discuss their implications in senescence and age-related diseases. We discuss emerging therapeutic strategies targeting telomere-regulatory ncRNAs in aging pathology.
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Affiliation(s)
- Martina Rossi
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, Maryland 21224, USA
| | - Myriam Gorospe
- Laboratory of Genetics and Genomics, National Institute on Aging Intramural Research Program, National Institutes of Health, Baltimore, Maryland 21224, USA.
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4
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Huang L, Jin K, Lan H. Luteolin inhibits cell cycle progression and induces apoptosis of breast cancer cells through downregulation of human telomerase reverse transcriptase. Oncol Lett 2019; 17:3842-3850. [PMID: 30930986 PMCID: PMC6425390 DOI: 10.3892/ol.2019.10052] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 01/16/2019] [Indexed: 01/03/2023] Open
Abstract
Luteolin is a flavonoid, which has been extensively investigated due to its antitumor effects; however, the underlying mechanisms of its action remain largely unknown. The present study aimed to investigate the role of luteolin in breast cancer (BC), and explored how luteolin suppresses the growth and induces the apoptosis of BC cells. The MTS assay was used to determine the anticancer activity of luteolin. Colony formation and Transwell assays were performed to evaluate the effects of luteolin on cell growth and invasion. Cell cycle progression and apoptosis were analyzed by flow cytometry. In addition, western blotting was performed to analyze cellular apoptosis and signaling pathways elicited by luteolin. The present study revealed that the proliferation of the BC cell line MDA-MB-231 was effectively suppressed by luteolin in a dose-dependent manner. Additionally, luteolin was revealed to increase apoptotic rates in BC cells. Dose-dependent cell cycle arrest in S phase was observed following treatment with luteolin in MDA-MB-231 cells. Mechanistically, luteolin reduced telomerase levels in a dose-dependent manner. Additionally, luteolin inhibited phosphorylation of the nuclear factor-κB inhibitor α and its target gene c-Myc, to suppress human telomerase reverse transcriptase (hTERT) expression, which encodes the catalytic subunit of telomerase. Collectively, the results of the present study indicated that luteolin may inhibit BC cell growth by targeting hTERT, suggesting that the mechanism of hTERT regulation by luteolin may justify further study regarding its potential as a therapeutic target for BC treatment.
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Affiliation(s)
- Liming Huang
- Department of Breast and Thyroid Surgery, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China
| | - Ketao Jin
- Department of Colorectal Surgery, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China
| | - Huanrong Lan
- Department of Breast and Thyroid Surgery, Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang 312000, P.R. China
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5
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Jeung HC, Rha SY, Shin SJ, Ahn JB, Park KH, Kim TS, Kim JJ, Roh JK, Chung HC. Changes in telomerase activity due to alternative splicing of human telomerase reverse transcriptase in colorectal cancer. Oncol Lett 2017; 14:2385-2392. [PMID: 28781675 DOI: 10.3892/ol.2017.6438] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 02/27/2017] [Indexed: 11/05/2022] Open
Abstract
Human telomerase reverse transcriptase (hTERT) expression level may not always correlate with telomerase activity. The present study analyzed hTERT splicing patterns with respect to hTERT and telomerase activity in colorectal cancer. Telomerase activity was determined by telomeric repeat amplification protocol assay, and spliced variants of hTERT were identified by reverse transcription-polymerase chain reaction in 40 colorectal cancer tissue samples. In the lower range of telomerase activity (0-100 units), the percentage of the β variant decreased with the increment in telomerase activity, whereas in the higher range of telomerase activity (>100 units), total hTERT expression level revealed a trend toward increment. There was a positive correlation between the full-length variant level and β variant level. Conversely, there was a negative correlation between the percentage of the full-length variant and β variant. Tumor-node-metastasis stage was the strongest prognostic factor in multivariate analysis and the percentage of the full-length variant was an independent prognostic factor for survival. Telomerase activity was primarily altered with changes in alternative splicing of the full-length and β variants of hTERT in colorectal cancer.
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Affiliation(s)
- Hei Cheul Jeung
- Cancer Metastasis Research Center, Division of Medical Oncology, Cancer Center Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul 06273, Republic of Korea
| | - Sun Young Rha
- Cancer Metastasis Research Center, Division of Medical Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Sang Joon Shin
- Cancer Metastasis Research Center, Division of Medical Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Joong Bae Ahn
- Cancer Metastasis Research Center, Division of Medical Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Kyu Hyun Park
- Cancer Metastasis Research Center, Division of Medical Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Tae Soo Kim
- Cancer Metastasis Research Center, Division of Medical Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Jin Ju Kim
- Department of Laboratory Medicine, Inha University School of Medicine, Incheon 22332, Republic of Korea
| | - Jae Kyung Roh
- Cancer Metastasis Research Center, Division of Medical Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
| | - Hyun Cheol Chung
- Cancer Metastasis Research Center, Division of Medical Oncology, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul 03722, Republic of Korea
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6
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Sekaran V, Soares J, Jarstfer MB. Telomere Maintenance as a Target for Drug Discovery. J Med Chem 2013; 57:521-38. [DOI: 10.1021/jm400528t] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Vijay Sekaran
- Division of Chemical Biology
and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Joana Soares
- Division of Chemical Biology
and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
| | - Michael B. Jarstfer
- Division of Chemical Biology
and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States
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7
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Nasiri M, Zarghami N, Koshki KN, Mollazadeh M, Moghaddam MP, Yamchi MR, Esfahlan RJ, Barkhordari A, Alibakhshi A. Curcumin and Silibinin Inhibit Telomerase Expression in T47D Human Breast Cancer Cells. Asian Pac J Cancer Prev 2013; 14:3449-3453. [DOI: 10.7314/apjcp.2013.14.6.3449] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/02/2023] Open
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8
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Jayasooriya RGPT, Kang SH, Kang CH, Choi YH, Moon DO, Hyun JW, Chang WY, Kim GY. Apigenin decreases cell viability and telomerase activity in human leukemia cell lines. Food Chem Toxicol 2012; 50:2605-11. [PMID: 22617349 DOI: 10.1016/j.fct.2012.05.024] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2011] [Revised: 04/21/2012] [Accepted: 05/11/2012] [Indexed: 10/28/2022]
Abstract
Recent studies have shown that apigenin (4',5,7-trihydroxyflavone inhibits human malignant cancer cell growth through cell cycle arrest and apoptosis. However, the underlying relationship between apoptosis and telomerase activity in response to apigenin exposure is not well understood. In this study, we found that apigenin significantly induces direct cytotoxicity in human leukemia cells (U937, THP-1 and HL60) through activation of the caspase pathway. As we presumed, treatment with apigenin was found to increase the level of intracellular reactive oxygen species (ROS), whereas pretreatment with antioxidants, N-acetyl-cysteine (NAC) or glutathione (GSH), completely attenuated ROS generation. Surprisingly, these antioxidants did not promote recuperation from apigenin-induced cell death. We further showed that apigenin downregulates telomerase activity in caspase-dependent apoptosis and observed that apigenin dosing results in downregulation of telomerase activity by suppression of c-Myc-mediated telomerase reverse transcriptase (hTERT) expression. In addition, treatment of apigenin-dosed cells with the two antioxidants did not restore telomerase activity. Taken together, this data suggests that ROS is not essential for suppression of apigenin-mediated apoptosis associated with the activation of caspases and regulation of telomerase activity via suppression of hTERT. We conclude that apigenin has a direct cytotoxic effect and the loss of telomerase activity in leukemia cells.
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Affiliation(s)
- R G P T Jayasooriya
- Laboratory of Immunobiology, Department of Marine Life Sciences, Jeju National University, Jeju 690-756, Republic of Korea
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9
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Glukhov AI, Svinareva LV, Severin SE, Shvets VI. Telomerase inhibitors as novel antitumor drugs. APPL BIOCHEM MICRO+ 2011. [DOI: 10.1134/s0003683811070039] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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10
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Inhibition of telomerase activity by HDV ribozyme in cancers. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2011; 30:1. [PMID: 21208462 PMCID: PMC3024244 DOI: 10.1186/1756-9966-30-1] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/03/2010] [Accepted: 01/06/2011] [Indexed: 12/30/2022]
Abstract
Background Telomerase plays an important role in cell proliferation and carcinogenesis and is believed to be a good target for anti-cancer drugs. Elimination of template function of telomerase RNA may repress the telomerase activity. Methods A pseudo-knotted HDV ribozyme (g.RZ57) directed against the RNA component of human telomerase (hTR) was designed and synthesized. An in vitro transcription plasmid and a eukaryotic expression plasmid of ribozyme were constructed. The eukaryotic expression plasmid was induced into heptocellular carcinoma 7402 cells, colon cancer HCT116 cells and L02 hepatocytes respectively. Then we determine the cleavage activity of ribozyme against human telomerase RNA component (hTR) both in vitro and in vivo, and detect telomerase activity continuously. Results HDV ribozyme showed a specific cleavage activity against the telomerase RNA in vitro. The maximum cleavage ratio reached about 70.4%. Transfection of HDV ribozyme into 7402 cells and colon cancer cells HCT116 led to growth arrest and the spontaneous apoptosis of cells, and the telomerase activity dropped to 10% of that before. Conclussion HDV ribozyme (g.RZ57) is an effective strategy for gene therapy.
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11
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Abstract
Advances in chromosome dynamics have increased our understanding of the significant role of telomeres and telomerase in cancer. Telomerase is expressed in almost all cancer cells but is inactive in most normal somatic cells. Therefore, telomerase is an important target for the design of therapeutic agents that might have minimal side effects. Herein, we evaluate current approaches to telomerase/telomere-targeted therapy, discuss the benefits and disadvantages, and speculate on the future direction of telomerase inhibitors as cancer therapeutics.
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12
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Moon DO, Kang CH, Kim MO, Jeon YJ, Lee JD, Choi YH, Kim GY. Beta-lapachone (LAPA) decreases cell viability and telomerase activity in leukemia cells: suppression of telomerase activity by LAPA. J Med Food 2010; 13:481-8. [PMID: 20438329 DOI: 10.1089/jmf.2008.1219] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Up-regulation of telomerase activity is associated with immortalization and unlimited cell division in most cancer cells. Therefore, telomerase represents a particularly attractive target for anticancer therapy. Recent reports have suggested that beta-lapachone (LAPA), the product of the South American Tabebuia avellanedae tree, inhibits growth of tumor cells. However, the underlying relationship between telomerase activity and apoptosis in response to LAPA exposure in leukemia cells remains poorly understood. In this study, we confirmed that LAPA treatment induces direct cytotoxicity in human leukemia cells (U937, K562, HL60, and THP-1) through activation of caspase-3 and subsequent cleavage of poly(ADP-ribose) polymerase. The observed induction of cell death was associated with decreased telomerase activity, which was ascribed to down-regulation of telomerase reverse transcriptase. Additionally, overexpression of anti-apoptotic Bcl-2 could not overcome the induction of apoptosis or the decreased telomerase activity in response to treatment of U937 cells with LAPA. We conclude that LAPA has a direct cytotoxic effect and the loss of telomerase activity in leukemia cells.
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Affiliation(s)
- Dong-Oh Moon
- Department of Marine Sciences, Jeju National University, Jeju, Republic of Korea
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13
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Abstract
Telomeres and telomerase play essential roles in the regulation of the lifespan of human cells. While normal human somatic cells do not or only transiently express telomerase and therefore shorten their telomeres with each cell division, most human cancer cells typically express high levels of telomerase and show unlimited cell proliferation. High telomerase expression allows cells to proliferate and expand long-term and therefore supports tumor growth. Owing to the high expression and its role, telomerase has become an attractive diagnostic and therapeutic cancer target. Imetelstat (GRN163L) is a potent and specific telomerase inhibitor and so far the only drug of its class in clinical trials. Here, we report on the structure and the mechanism of action of imetelstat as well as about the preclinical and clinical data and future prospects using imetelstat in cancer therapy.
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14
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Sumi D, Shinkai Y, Kumagai Y. Signal transduction pathways and transcription factors triggered by arsenic trioxide in leukemia cells. Toxicol Appl Pharmacol 2010; 244:385-92. [PMID: 20193703 DOI: 10.1016/j.taap.2010.02.012] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 02/09/2010] [Accepted: 02/21/2010] [Indexed: 12/23/2022]
Abstract
Arsenic trioxide (As(2)O(3)) is widely used to treat acute promyelocytic leukemia (APL). Several lines of evidence have indicated that As(2)O(3) affects signal transduction and transactivation of transcription factors, resulting in the stimulation of apoptosis in leukemia cells, because some transcription factors are reported to associate with the redox condition of the cells, and arsenicals cause oxidative stress. Thus, the disturbance and activation of the cellular signaling pathway and transcription factors due to reactive oxygen species (ROS) generation during arsenic exposure may explain the ability of As(2)O(3) to induce a complete remission in relapsed APL patients. In this report, we review recent findings on ROS generation and alterations in signal transduction and in transactivation of transcription factors during As(2)O(3) exposure in leukemia cells.
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Affiliation(s)
- Daigo Sumi
- Faculty of Pharmaceutical Sciences, Tokushima Bunri University, 180, Yamashiro-cho, Tokushima-city, Tokushima 770-8514, Japan.
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Gefitinib induces apoptosis and decreases telomerase activity in MDA-MB-231 human breast cancer cells. Arch Pharm Res 2009; 32:1351-60. [PMID: 19898796 DOI: 10.1007/s12272-009-2002-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 07/16/2009] [Accepted: 07/17/2009] [Indexed: 10/20/2022]
Abstract
Gefitinib is an anti-cancer drug that selectively inhibits epithelial growth factor receptor (EGFR) tyrosine kinase activity and induces apoptosis in many cancer cells. Cancer cells are often protected from apoptotic cell death by telomerase, however the gefitinib-induced telomerase inhibition remains unknown. Here we investigated the effects of gefitinib on telomerase activity in two different breast cancer lines, MCF-7 (low expression of EGFR) and MDA-MB-231 (high expression of EGFR). We observed the inhibition of EGFR phosphorylation that occurred only MDA-MB-231 cells cultured in media containing 10% FBS. Direct cytotoxicity was observed in MDA-MB-231 cells, but not MCF-7 cells when treated with concentrations of gefitinib ranging from 15 to 20 microM. This cytotoxicity was associated with decreased telomerase activity and downregulation of the telomerase subunit, hTERT. c-Myc has previously been shown to activate telomerase activity through transcriptional regulation of hTERT. A decrease in c-myc expression and DNA-binding activity following treatment with gefitinib was observed exclusively in MDA-MB-231 cells. We also demonstrated that gefitinib downregulates the activation of Akt and subsequent hTERT phosphorylation and translocation into the nucleus in MDA-MB-231 cells. These results indicate that gefitinib induces loss of telomerase activity through dephosphorylation of EGFR in MDA-MB-231 cells.
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16
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Moon DO, Kim MO, Lee JD, Choi YH, Kim GY. Butein suppresses c-Myc-dependent transcription and Akt-dependent phosphorylation of hTERT in human leukemia cells. Cancer Lett 2009; 286:172-9. [PMID: 19560862 DOI: 10.1016/j.canlet.2009.05.028] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Revised: 05/12/2009] [Accepted: 05/25/2009] [Indexed: 01/21/2023]
Abstract
Telomerase, a ribonucleoprotein that plays an important role in neoplastic immortality, is up-regulated in approximately 85% of cancers, especially in leukemia. The polyphenol, butein, has potent effects against various types of cancer cells, but its effects on telomerase activity have not been well characterized. In this study, we show that butein causes a down-regulation of hTERT gene expression and a concomitant decrease of telomerase activity. Butein also suppresses expression of c-Myc at the transcriptional level and down-regulates DNA-binding activity, regardless of cell type specificity, in leukemia cells. DNA-binding activities of c-Myc to the hTERT core promoter were decreased in butein-treated cells, as seen by chromatin immunoprecipitation assay. Treatment with butein also suppressed the activation of Akt, thereby inhibiting hTERT phosphorylation and translocation into the nucleus. In this process, butein also up-regulated the surface expression of CD11b in leukemia cells. Inhibition of telomerase activity by butein was followed by loss of proliferative capacity, induction of apoptosis, and differentiation. These findings demonstrate the effectiveness of butein at inhibiting telomerase activity by down-regulating hTERT gene expression in human leukemia cells.
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Affiliation(s)
- Dong-Oh Moon
- Department of Marine Life Science, Jeju National University and Jeju Regional Cancer Center, Jeju 690-756, Republic of Korea
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17
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Deville L, Hillion J, Ségal-Bendirdjian E. Telomerase regulation in hematological cancers: a matter of stemness? Biochim Biophys Acta Mol Basis Dis 2009; 1792:229-39. [PMID: 19419697 DOI: 10.1016/j.bbadis.2009.01.016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Revised: 01/30/2009] [Accepted: 01/30/2009] [Indexed: 01/02/2023]
Abstract
Human telomerase is a nuclear ribonucleoprotein enzyme complex that catalyzes the synthesis and extension of telomeric DNA. This enzyme is highly expressed and active in most malignant tumors while it is usually not or transiently detectable in normal somatic cells, suggesting that it plays an important role in cellular immortalization and tumorigenesis. As most leukemic cells are generally telomerase-positive and have often shortened telomeres, our understanding of how telomerase is deregulated in these diseases could help to define novel therapies targeting the telomere/telomerase complex. Nonetheless, considering that normal hematopoietic stem cells and some of their progeny do express a functional telomerase, it is tempting to consider such an activity in leukemias as a sustained stemness feature and important to understand how telomere length and telomerase activity are regulated in the various forms of leukemias.
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Affiliation(s)
- Laure Deville
- INSERM UMR-S 685, Institut d'Hématologie, Hôpital Saint-Louis, 75475 Paris cedex 10, France
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18
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Kim MO, Moon DO, Kang SH, Heo MS, Choi YH, Jung JH, Lee JD, Kim GY. Pectenotoxin-2 represses telomerase activity in human leukemia cells through suppression of hTERT gene expression and Akt-dependent hTERT phosphorylation. FEBS Lett 2008; 582:3263-9. [PMID: 18775701 DOI: 10.1016/j.febslet.2008.08.030] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2008] [Revised: 08/11/2008] [Accepted: 08/12/2008] [Indexed: 11/29/2022]
Abstract
In this study, we found that pectenotoxin-2 (PTX-2) decreased cell viability and inhibited telomerase activity with downregulation of hTERT expression in human leukemia cells. PTX-2 treatment also reduced c-Myc and Sp1 gene expression and DNA binding activity. Further chromatin immunoprecipitation assay demonstrated that PTX-2 attenuated the binding of c-Myc and Sp1 to the regulatory regions of hTERT. We also observed that PTX-2 treatment attenuated the phosphorylation of Akt, thereby reducing the phosphorylation and nuclear translocation of hTERT. We concluded that PTX-2 suppressed telomerase activity through the transcriptional and post-translational suppression of hTERT and this process precedes cellular differentiation of human leukemia cells.
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Affiliation(s)
- Mun-Ock Kim
- Department of Microbiology, Pusan National University, Busan 609-735, Republic of Korea
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19
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Kim MO, Moon DO, Choi YH, Shin DY, Kang HS, Choi BT, Lee JD, Li W, Kim GY. Platycodin D induces apoptosis and decreases telomerase activity in human leukemia cells. Cancer Lett 2008; 261:98-107. [PMID: 18093727 DOI: 10.1016/j.canlet.2007.11.010] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 10/15/2007] [Accepted: 11/06/2007] [Indexed: 10/22/2022]
Abstract
Platycodin D (PD) is a major constituent of triterpene saponins found in the root of Platycodon grandiflorum. Recent studies have demonstrated that PD is a potentially interesting candidate for use in cancer chemotherapy. However, the molecular mechanisms responsible for PD-induced telomerase inhibition remain to be poorly known. In this study, we examined the effects of PD treatment on telomerase activity in different human leukemia cell lines. At concentrations between 10 and 20 microM, PD exerted a dose-dependent direct cytotoxic effect and inhibition of telomerase activity via downregulation of hTERT expression. Because c-Myc and Sp1 are known to directly regulate transcription of hTERT, we also evaluated the expression and DNA binding activity of these proteins. PD treatment reduced c-Myc and Sp1 protein levels and DNA binding activities in a dose-dependent manner. We also observed that PD treatment downregulates the activation of Akt, thereby reducing the phosphorylation and nuclear translocation of hTERT. We conclude that PD has direct cytotoxic effect on human leukemia cells and suppresses telomerase activity through transcriptional and posttranslational suppression of hTERT.
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Affiliation(s)
- Mun-Ock Kim
- Department of Microbiology, College of Natural Sciences, Pusan National University, Busan 609-735, Republic of Korea
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Olaussen KA, Dubrana K, Domont J, Spano JP, Sabatier L, Soria JC. Telomeres and telomerase as targets for anticancer drug development. Crit Rev Oncol Hematol 2006; 57:191-214. [PMID: 16469501 DOI: 10.1016/j.critrevonc.2005.08.007] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2005] [Revised: 08/10/2005] [Accepted: 08/11/2005] [Indexed: 12/15/2022] Open
Abstract
In most human cancers, the telomere erosion problem has been bypassed through the activation of a telomere maintenance system (usually activation of telomerase). Therefore, telomere and telomerase are attractive targets for anti-cancer therapeutic interventions. Here, we review a large panel of strategies that have been explored to date, from small inhibitors of the catalytic sub-unit of telomerase to anti-telomerase immunotherapy and gene therapy. The many positive results that are reported from anti-telomere/telomerase assays suggest a prudent optimism for a possible clinical application in a close future. However, we discuss some of the main limits for these approaches of antitumour drug development and why significant work remains before a clinically useful drug can be proposed to patients.
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Affiliation(s)
- Ken André Olaussen
- Laboratory of Radiobiology and Oncology, DSV/DRR/LRO, CEA, Fontenay aux Roses, France
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Lindkvist A, Ivarsson K, Jernberg-Wiklund H, Paulsson-Karlsson Y. Interferon-induced sensitization to apoptosis is associated with repressed transcriptional activity of the hTERT promoter in multiple myeloma. Biochem Biophys Res Commun 2006; 341:1141-8. [PMID: 16460686 DOI: 10.1016/j.bbrc.2006.01.068] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2006] [Accepted: 01/18/2006] [Indexed: 11/21/2022]
Abstract
The aim of the present study was to explore hTERT as a target for IFN-induced sensitization to apoptosis in multiple myeloma (MM). IFN-alpha and IFN-gamma downregulated telomerase activity in the IL-6-dependent MM cell line U-266-1970. In MM cells undergoing IFN-induced sensitization to Fas-mediated apoptosis, the repression of telomerase was increased as compared to IFN-alpha treatment alone. Similar to the sensitization effect of IFN, the use of a dominant negative IkappaBalpha vector inhibiting hTERT activity via transcriptional targeting resulted in augmentation of Fas-mediated apoptosis. The mechanism underlying the reduction of telomerase activity by IFN was shown to be transcriptional repression of the hTERT gene. The present study does not support a direct effect of IFN on NF-kappaB binding to the hTERT promoter as underlying the transcriptional repression. We conclude that one potential mechanism whereby IFNs induce apoptosis sensitization is by repressing hTERT transcription and telomerase activity, thereby constituting attractive targets for MM therapy.
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Affiliation(s)
- Anna Lindkvist
- Department of Genetics and Pathology, Uppsala University Hospital, Rudbeck Laboratory, SE-751 85 Uppsala, Sweden.
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22
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Cunningham AP, Love WK, Zhang RW, Andrews LG, Tollefsbol TO. Telomerase inhibition in cancer therapeutics: molecular-based approaches. Curr Med Chem 2006; 13:2875-88. [PMID: 17073634 PMCID: PMC2423208 DOI: 10.2174/092986706778521887] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Current standard cancer therapies (chemotherapy and radiation) often cause serious adverse off-target effects. Drug design strategies are therefore being developed that will more precisely target cancer cells for destruction while leaving surrounding normal cells relatively unaffected. Telomerase, widely expressed in most human cancers but almost undetectable in normal somatic cells, provides an exciting drug target. This review focuses on recent pharmacogenomic approaches to telomerase inhibition. Antisense oligonucleotides, RNA interference, ribozymes, mutant expression, and the exploitation of differential telomerase expression as a strategy for targeted oncolysis are discussed here in the context of cancer therapeutics. Reports of synergism between telomerase inhibitors and traditional cancer therapeutic agents are also analyzed.
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MESH Headings
- Drug Design
- Enzyme Inhibitors/pharmacology
- Enzyme Inhibitors/therapeutic use
- Humans
- Neoplasms/drug therapy
- Neoplasms/enzymology
- Neoplasms/pathology
- Oligonucleotides, Antisense/genetics
- Oligonucleotides, Antisense/pharmacology
- Oligonucleotides, Antisense/therapeutic use
- RNA, Antisense/genetics
- RNA, Antisense/pharmacology
- RNA, Antisense/therapeutic use
- RNA, Catalytic/genetics
- RNA, Catalytic/metabolism
- RNA, Untranslated/genetics
- RNA, Untranslated/metabolism
- Telomerase/antagonists & inhibitors
- Telomerase/genetics
- Telomerase/metabolism
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Affiliation(s)
- A P Cunningham
- Department of Biology, University of Alabama at Birmingham, AL 35294, USA
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Abstract
Telomeres are complex structures which serve to protect chromosome ends. Telomere shortening occurs in normal somatic cells reaching a point in which cells senesce. Senescence can be counteracted by activating telomerase. Telomerase activity is present in a majority of cancer cells and requires the upregulation of the reverse transcriptase component called hTERT. Because telomerase activity is essential for proliferation of most cancer cells, therapeutic strategies have been developed to inhibit its activity. These strategies centre on targeting the active site, hTERT and hTERC expression, core enzyme stability and telomeric DNA. Successful approaches involve a combination of traditional drugs with telomerase inhibitors. Disrupting the functional expression of hTERT is particularly effective in agreement with evidence that hTERT is an antiapoptotic factor in some cancer cells. In addition, approaches that stabilise DNA secondary structures may disrupt telomere maintenance through a variety of routes making them, potentially, very potent in attack-ing cancer cells.
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Affiliation(s)
- Terace M Fletcher
- Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, 1011 NW 15 Street, Miami, FL 33136, USA.
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