701
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Zhang A, Zheng C, Hou M, Lindvall C, Li KJ, Erlandsson F, Björkholm M, Gruber A, Blennow E, Xu D. Deletion of the telomerase reverse transcriptase gene and haploinsufficiency of telomere maintenance in Cri du chat syndrome. Am J Hum Genet 2003; 72:940-8. [PMID: 12629597 PMCID: PMC1180356 DOI: 10.1086/374565] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2002] [Accepted: 01/13/2003] [Indexed: 01/11/2023] Open
Abstract
Cri du chat syndrome (CdCS) results from loss of the distal portion of chromosome 5p, where the telomerase reverse transcriptase (hTERT) gene is localized (5p15.33). hTERT is the rate-limiting component for telomerase activity that is essential for telomere-length maintenance and sustained cell proliferation. Here, we show that a concomitant deletion of the hTERT allele occurs in all 10 patients with CdCS whom we examined. Induction of hTERT mRNA in proliferating lymphocytes derived from five of seven patients was lower than that in unaffected control individuals (P<.05). The patient lymphocytes exhibited shorter telomeres than age-matched unaffected individuals (P<.0001). A reduction in replicative life span and a high rate of chromosome fusions were observed in cultured patient fibroblasts. Reconstitution of telomerase activity by ectopic expression of hTERT extended the telomere length, increased the population doublings, and prevented the end-to-end fusion of chromosomes. We conclude that hTERT is limiting and haploinsufficient for telomere maintenance in humans in vivo. Accordingly, the hTERT deletion may be one genetic element contributing to the phenotypic changes in CdCS.
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Affiliation(s)
- Anju Zhang
- Department of Pathology and Oncology, Department of Medicine, Division of Hematology, Department of Molecular Medicine, and Department of Biosciences at Novum, Karolinska Institutet and Hospital, Stockholm; and Shaanxi Provincial Hospital, Xian, China
| | - Chengyun Zheng
- Department of Pathology and Oncology, Department of Medicine, Division of Hematology, Department of Molecular Medicine, and Department of Biosciences at Novum, Karolinska Institutet and Hospital, Stockholm; and Shaanxi Provincial Hospital, Xian, China
| | - Mi Hou
- Department of Pathology and Oncology, Department of Medicine, Division of Hematology, Department of Molecular Medicine, and Department of Biosciences at Novum, Karolinska Institutet and Hospital, Stockholm; and Shaanxi Provincial Hospital, Xian, China
| | - Charlotta Lindvall
- Department of Pathology and Oncology, Department of Medicine, Division of Hematology, Department of Molecular Medicine, and Department of Biosciences at Novum, Karolinska Institutet and Hospital, Stockholm; and Shaanxi Provincial Hospital, Xian, China
| | - Ke-Jun Li
- Department of Pathology and Oncology, Department of Medicine, Division of Hematology, Department of Molecular Medicine, and Department of Biosciences at Novum, Karolinska Institutet and Hospital, Stockholm; and Shaanxi Provincial Hospital, Xian, China
| | - Fredrik Erlandsson
- Department of Pathology and Oncology, Department of Medicine, Division of Hematology, Department of Molecular Medicine, and Department of Biosciences at Novum, Karolinska Institutet and Hospital, Stockholm; and Shaanxi Provincial Hospital, Xian, China
| | - Magnus Björkholm
- Department of Pathology and Oncology, Department of Medicine, Division of Hematology, Department of Molecular Medicine, and Department of Biosciences at Novum, Karolinska Institutet and Hospital, Stockholm; and Shaanxi Provincial Hospital, Xian, China
| | - Astrid Gruber
- Department of Pathology and Oncology, Department of Medicine, Division of Hematology, Department of Molecular Medicine, and Department of Biosciences at Novum, Karolinska Institutet and Hospital, Stockholm; and Shaanxi Provincial Hospital, Xian, China
| | - Elisabeth Blennow
- Department of Pathology and Oncology, Department of Medicine, Division of Hematology, Department of Molecular Medicine, and Department of Biosciences at Novum, Karolinska Institutet and Hospital, Stockholm; and Shaanxi Provincial Hospital, Xian, China
| | - Dawei Xu
- Department of Pathology and Oncology, Department of Medicine, Division of Hematology, Department of Molecular Medicine, and Department of Biosciences at Novum, Karolinska Institutet and Hospital, Stockholm; and Shaanxi Provincial Hospital, Xian, China
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702
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Abstract
The incidence of cancer increases with age in humans and in laboratory animals alike. There are different patterns of age-related distribution of tumors in different organs and tissues. Aging may increase or decrease the susceptibility of various tissues to initiation of carcinogenesis and usually facilitates promotion and progression of carcinogenesis. Aging may predispose to cancer by several mechanisms: (1) tissue accumulation of cells in late stages of carcinogenesis; (2) alterations in homeostasis, in particular, alterations in immune and endocrine system and (3) telomere instability linking aging and increased cancer risk. Increased susceptibility to the effects of tumor promoters is found both in aged animals and aged humans, as predicted by the multistage model of carcinogenesis. Available evidence supporting the relevance of replicative senescence of human cells and telomere biology to human cancer seems quite strong, however, the evidence linking cellular senescence to human aging is controversial and required additional studies. Data on the acceleration of aging by carcinogenic agents as well as on increased cancer risk in patients with premature aging are critically discussed. In genetically modified mouse models (transgenic, knockout or mutant) characterized by the aging delay, the incidence of tumors usually similar to those in controls, whereas the latent period of tumor development is increased. Practically all models of accelerated of aging in genetically modified animals show the increase in the incidence and the reduction in the latency of tumors. Strategies for cancer prevention must include not only measures to minimize exposure to exogenous carcinogenic agents, but also measures to normalize the age-related alterations in internal milieu. Life-span prolonging drugs (geroprotectors) may either postpone population aging and increase of tumor latency or decrease the mortality in long-living individuals in populations and inhibit carcinogenesis. At least some geroprotectors may increase the survival of a short-living individuals in populations but increase the incidence of malignancy.
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Affiliation(s)
- Vladimir N Anisimov
- Department of Carcinogenesis and Oncogerontology, N.N. Petrov Research Institute of Oncology, Pesochny-2, 68 Leningradskaya St., St. Petersburg 197758, Russia.
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703
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Nakajima A, Tauchi T, Sashida G, Sumi M, Abe K, Yamamoto K, Ohyashiki JH, Ohyashiki K. Telomerase inhibition enhances apoptosis in human acute leukemia cells: possibility of antitelomerase therapy. Leukemia 2003; 17:560-7. [PMID: 12646945 DOI: 10.1038/sj.leu.2402825] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Telomerase is a ribonucleoprotein enzyme that maintains protective structures at the ends of eukaryotic chromosomes. We examined the impact of telomerase inhibition by the dominant-negative human catalytic subunit of telomerase (DN-hTERT) on the biological features of acute leukemia. We introduced vectors encoding dominant- negative (DN)-hTERT, wild-type (WT)-hTERT, or a control vector expressing only a drug-resistant marker into a telomerase-positive human acute lymphoblastic leukemia cell line, HAL-01. Expression of DN-hTERT dramatically inhibited telomerase activity, leading to apoptotic cell death. Mutant telomerase expression also enhanced daunorubicin-induced apoptosis. Nude mice (n=5 per group) received subcutanous implants of HAL-01 cells expressing the control vector or DN-hTERT or WT-hTERT. Implantation of HAL-01 cells expressing control vector (n=5) rapidly produced tumors, whereas implantation of those expressing DN-hTERT (n=5) did not. Thus, telomerase inhibition both growth of HAL-01 cells in vitro and tumorigenic capacity in vivo. Furthermore, the G-quadruplex-interactive telomerase-specific inhibitor, telomestatin, shortened the telomere length and induced apoptosis in freshly isolated primary acute leukemia cells. These results suggest that antitelomerase therapy may be useful in some acute leukemias in combination with antileukemic agents such as daunorubicin.
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Affiliation(s)
- A Nakajima
- First Department of Internal Medicine, Tokyo Medical University, Shinjuku-ku, Japan
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704
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Papadopoulou A, Trangas T, Teixeira MR, Heim S, Dimitriadis E, Tsarouha H, Andersen JA, Evangelou E, Ioannidis P, Agnantis NJ, Pandis N. Telomerase activity and genetic alterations in primary breast carcinomas. Neoplasia 2003; 5:170-8. [PMID: 12659690 PMCID: PMC1502403 DOI: 10.1016/s1476-5586(03)80009-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
It has been proposed that the structural and numerical chromosome abnormalities recorded in breast cancer could be the result of telomere dysfunction and that telomerase is activated de novo to provide a survival mechanism curtailing further chromosomal aberrations. However, recent in vivo and in vitro data show that the ectopic expression of telomerase promotes tumorigenesis via a telomere length-independent mechanism. In this study, the relation between telomerase expression and the extent of chromosomal aberrations was investigated in 62 primary breast carcinomas. Telomerase activity was measured using a polymerase chain reaction-based telomeric repeat amplification protocol assay and 92% of the tumors were found to express telomerase with a relative activity ranging from 0 to 3839.6. Genetic alterations were determined by G-banding and comparative genomic hybridization analysis and 97% of the tumors exhibited chromosomal aberrations ranging from 0 to 44 (average: 10.98). In the overall series, the relationship between telomerase activity levels and genetic changes could be best described by a quadratic model, whereas in tumors with below-average genetic alteration numbers, a significant positive association was recorded between the two variables (coefficient=0.374, P=.017). The relationship between telomerase activity levels and the extent of genetic alteration may reflect the complex effect of telomerase activation upon tumor progression in breast carcinomas.
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Affiliation(s)
| | - Theoni Trangas
- Department of Genetics, Saint Savas Hospital, Athens, Greece
| | - Manuel R Teixeira
- Department of Genetics, Portuguese Oncology Institute, Porto, Portugal
| | - Sverre Heim
- Department of Cancer Genetics, The Norwegian Radium Hospital, Oslo, Norway
| | | | | | - Johan A Andersen
- Department of Pathology, Odense University Hospital, Odense, Denmark
| | - Evangelos Evangelou
- Department of Public Health, School of Nursing, University of Athens, Athens, Greece
| | | | | | - Nikos Pandis
- Department of Genetics, Saint Savas Hospital, Athens, Greece
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705
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Wong KK, Maser RS, Bachoo RM, Menon J, Carrasco DR, Gu Y, Alt FW, DePinho RA. Telomere dysfunction and Atm deficiency compromises organ homeostasis and accelerates ageing. Nature 2003; 421:643-8. [PMID: 12540856 DOI: 10.1038/nature01385] [Citation(s) in RCA: 285] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2002] [Accepted: 12/17/2002] [Indexed: 11/09/2022]
Abstract
Ataxia-telangiectasia (A-T) results from the loss of ataxia-telangiectasia mutated (Atm) function and is characterized by accelerated telomere loss, genomic instability, progressive neurological degeneration, premature ageing and increased neoplasia incidence. Here we evaluate the functional interaction of Atm and telomeres in vivo. We examined the impact of Atm deficiency as a function of progressive telomere attrition at both the cellular and whole-organism level in mice doubly null for Atm and the telomerase RNA component (Terc). These compound mutants showed increased telomere erosion and genomic instability, yet they experienced a substantial elimination of T-cell lymphomas associated with Atm deficiency. A generalized proliferation defect was evident in all cell types and tissues examined, and this defect extended to tissue stem/progenitor cell compartments, thereby providing a basis for progressive multi-organ system compromise, accelerated ageing and premature death. We show that Atm deficiency and telomere dysfunction act together to impair cellular and whole-organism viability, thus supporting the view that aspects of A-T pathophysiology are linked to the functional state of telomeres and its adverse effects on stem/progenitor cell reserves.
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Affiliation(s)
- Kwok-Kin Wong
- Department of Adult Oncology, Dana Farber Cancer Institute Boston, Massachusetts 02115, USA
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706
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Abstract
Telomerase activity is necessary to maintain the integrity of telomeres, which in turn prevent chromosome ends from being processed and signaled as damaged DNA. That cancer cells rely on telomerase to maintain functional telomeres and to divide indefinitely has highlighted the potential for developing novel therapeutic approaches that target telomerase.
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Affiliation(s)
- MarÃa A Blasco
- Department of Immunology and Oncology, National Centre of Biotechnology, Madrid, Spain.
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707
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Abstract
Loss of tumour suppressor function is a common mechanistic step in deregulated cell growth and neoplasia. The p53 tumour suppressor gene is the most frequently mutated gene in cancer, and is inactivated in approximately 50% of human tumours. Mutation of p53 is also the predominant molecular basis of the Li-Fraumeni familial cancer susceptibility syndrome. p53 is a transcription factor that functions to regulate the integrity of the genome in response to DNA damage by inducing genes that promote cell cycle arrest, cell death, or repair of damaged DNA. These various effects exerted by p53 ensure that mutations do not pass on to subsequent generations, thus avoiding the presence of cells with multiple genetic hits that predispose the cell to neoplastic growth. Analysis of p53 functions using genetically-modified mice has complimented studies performed with human cancer tissue or cultured cells, and has greatly expanded knowledge about the role of p53 in tumour suppression. This finer understanding of p53 function has greatly facilitated research into small-molecule and other drug modifications of p53 activity as treatment modalities for the many human cancers bearing altered p53 function. This review will examine mouse models containing p53 modifications, and access the contribution of these studies to the understanding of p53-mediated tumour suppression.
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Affiliation(s)
- Hayla K Sluss
- Department of Cell Biology, University of Massachusetts Medical School, 55 Lake Avenue, Worcester, Massachusetts 01541, USA.
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708
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Baerlocher GM, Mak J, Röth A, Rice KS, Lansdorp PM. Telomere shortening in leukocyte subpopulations from baboons. J Leukoc Biol 2003; 73:289-96. [PMID: 12554806 DOI: 10.1189/jlb.0702361] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
To address questions about telomere length regulation in nonhuman primates, we studied the telomere length in subpopulations of leukocytes from the peripheral blood of baboons aged 0.2-26.5 years. Telomere length in granulocytes, B cells, and subpopulations of T cells all decreased with age. Overall, telomere length kinetics were lineage- and cell subset-specific. T cells showed the most pronounced, overall decline in telomere length. Levels of telomerase in stimulated T cells from old animals were lower than in corresponding cells from young animals. Memory T cells with very short telomeres accumulated in old animals. In contrast, the average telomere length values in B cells remained relatively constant from middle age onward. Individual B cells showed highly variable telomere length, and B cells with very long telomeres were observed after the ages of 1-2 years. In general, cell type-specific telomere kinetics in baboons were remarkably similar to those observed in humans.
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Affiliation(s)
- Gabriela M Baerlocher
- Terry Fox Laboratory, British Columbia Cancer Agency, 601 West 10th Avenue, Vancouver, BC, V5Z 1L3 Canada
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709
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Abstract
The analysis of compound mouse mutants for nonhomologous end-joining DNA double-strand break repair and those deficient for the p53 checkpoint pathway has provided a fascinating look at the carcinogenic consequences of the failure to properly repair DNA damage and to elicit appropriate checkpoints.
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Affiliation(s)
- Richard S Maser
- Department of Medical Oncology, Dana Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA.
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710
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Abstract
Telomeres are the structures that protect eukaryotic chromosomes from recognition by DNA damage surveillance mechanisms and are maintained in the germ line of multicellular animals by telomerase. In most human somatic cells telomerase is silenced during development and after extensive cell division telomeres shorten to trigger growth arrest. Around 80% of human cancers escape from this growth arrest by re-activating telomerase but at diagnosis many cancers still have very short telomeres making them very vulnerable to the inhibition of telomerase. As normal cells have a considerable telomere reserve, even in elderly humans, this makes telomerase an attractive and potentially selective anti-cancer drug target. Proof-of-principle experiments are reviewed which show that this optimism may be justified at least for the subset of human cancers with short telomeres. I also address many of the commonly raised concerns that surround telomerase as a target for anti-cancer drug design.
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Affiliation(s)
- Eric Kenneth Parkinson
- Beatson Institute for Cancer Research, Cancer Research UK Beatson Laboratories, Bearsden, Glasgow, Scotland, UK.
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711
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Blankenstein T, Qin Z. Chemical carcinogens as foreign bodies and some pitfalls regarding cancer immune surveillance. Adv Cancer Res 2003; 90:179-207. [PMID: 14710951 DOI: 10.1016/s0065-230x(03)90006-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Interferon-gamma-receptor (IFN-gammaR)-deficient mice are more susceptible to tumor induction by methylcholanthrene (MCA) in comparison to control littermates. The cellular source of IFNgamma is not known, but the absence of T cells does not significantly increase the incidence of MCA-induced tumors. However, it appears that the presence of T cells in combination with unknown, perhaps environmental, factors can decrease MCA-induced tumor incidence, indicating that IFN-gamma of unknown origin contributes to the protective response. The current knowledge of cancer biology, immune regulation, and tumor-promoting effects of inflammation are difficult to reconcile with the concept of immune surveillance against non-virus-associated cancer. Analysis of the primary MCA-treated mouse indicates, as one protective mechanism, a tissue repair response against MCA-induced damage, in the course of which MCA is encapsulated and persists for long time in tumor-free mice, termed foreign-body reaction. The protection from DNA damage could simultaneously diminish tissue injury and malignant transformation. We argue that inhibition of MCA-induced carcinogenesis is mechanistically different from tumor transplantation immunity and that a longer latency in MCA-treated mice is unlikely due to T cell-mediated tumor recognition and selection of less immunogenic variants. We discuss that the IFNgammaR-dependent mechanism against MCA is unrelated to the original concept of T cell-mediated immune surveillance and that the increased spontaneous tumor incidence observed in some immune-deficient mice is likely to be explained by opportunistic infection and tumor-promoting chronic inflammation.
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712
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Klein CA. The Systemic Progression of Human Cancer: A Focus on the Individual Disseminated Cancer Cell—The Unit of Selection. Adv Cancer Res 2003; 89:35-67. [PMID: 14587870 DOI: 10.1016/s0065-230x(03)01002-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The metastatic progression of solid tumors is discussed controversially. Because metastasis is usually lethal, it appears as an end point of successive cellular changes. This has led to the prevailing interpretation that genetic changes, in addition to those present in the most advanced clone of the primary tumor, are required to initiate invasion, dissemination, and growth at anatomically distant sites. It has become possible to detect and analyze single disseminated cancer cells at ectopic sites long before metastasis can be diagnosed by standard clinical techniques. Because the finding of single disseminated cancer cells correlates with the subsequent development of distant metastasis, these cells have been identified as the precursors of metastasis. Their direct molecular-genetic characterization, however, shows that dissemination occurs very early in the process of accumulation of genetic changes and suggests that metastases may seldom be derived from the dominant clone of the primary tumor. In contrast, it appears that cancer cell evolution explores a multitude of variant cells from which systemic cancer can develop independently. This review integrates data derived by different approaches into a model of systemic cancer progression.
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Affiliation(s)
- Christoph A Klein
- Institut für Immunologie, Ludwig-Maximilians Universität München, Goethestr 31, 80336 München, Germany
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713
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Chang S, Khoo CM, Naylor ML, Maser RS, DePinho RA. Telomere-based crisis: functional differences between telomerase activation and ALT in tumor progression. Genes Dev 2003; 17:88-100. [PMID: 12514102 PMCID: PMC195968 DOI: 10.1101/gad.1029903] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Telomerase activation is a common feature of most advanced human cancers and is postulated to restore genomic stability to a level permissive for cell viability and tumor progression. Here, we used genetically defined transformed mouse embryonic fibroblast (MEF) cultures derived from late generation mTerc(-/-) Ink4a/Arf(-/-) mice to explore more directly how telomere-based crisis relates to the evolution of cancer cell genomes and to tumor biology. An exhaustive serial analysis of cytogenetic profiles over extensive passage in culture revealed that the emergence of chromosomal fusions (including dicentrics) coincided with onset of deletions and complex nonreciprocal translocations (NRTs), whereas mTerc-transduced cultures maintained intact chromosomes and stable genomes. Despite a high degree of telomere dysfunction and genomic instability, transformed late passage mTerc(-/-) Ink4a/Arf(-/-) cultures retained the capacity to form subcutaneous tumors in immunocompromised mice. However, even moderate levels of telomere dysfunction completely abrogated the capacity of these cells to form lung metastases after tail-vein injection, whereas mTerc reconstitution alone conferred robust metastatic activity in these cells. Finally, serial subcutaneous tumor formation using late passage transformed mTerc(-/-) Ink4a/Arf(-/-) cultures revealed clear evidence of telomerase-independent alternative lengthening of telomeres (ALT). Significantly, despite a marked increase in telomere reserve, cells derived from the ALT+ subcutaneous tumors were unable to generate lung metastases, indicating in vivo functional differences in these principal mechanisms of telomere maintenance. Together, these results are consistent with the model that although telomere dysfunction provokes chromosomal aberrations that initiate carcinogenesis, telomerase-mediated telomere maintenance enables such initiated cells to efficiently achieve a fully malignant endpoint, including metastasis.
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Affiliation(s)
- Sandy Chang
- Department of Medical Oncology, Dana Farber Cancer Institute, Boston, Massachusetts 02115, USA
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714
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Artandi SE. Complex roles for telomeres and telomerase in breast carcinogenesis. Breast Cancer Res 2003; 5:37-41. [PMID: 12559044 PMCID: PMC154132 DOI: 10.1186/bcr553] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2002] [Revised: 09/06/2002] [Accepted: 10/07/2002] [Indexed: 12/03/2022] Open
Abstract
Telomerase - an enzyme that endows cells with unlimited proliferative potential - is differentially expressed in cancer cells and in normal cells. Although most primary human cells lack telomerase, the enzyme is upregulated in more than 90% of invasive breast cancers. As a result, much of breast cancer development occurs before telomerase is reactivated during a critical transition from a telomerase-negative to a telomerase-positive state. During this transition, the telomere shortening that accompanies cell division may either prevent or facilitate tumorigenesis by activating checkpoints and impairing chromosomal stability. In mature cancers, telomerase probably serves a crucial role in tumor progression and maintenance by stabilizing telomeres and supporting the immortal growth of breast cancer cells.
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Affiliation(s)
- Steven E Artandi
- Department of Medicine/Hematology, Cancer Biology Program, Stanford University School of Medicine, Stanford, California, USA.
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715
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716
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Gladdy RA, Taylor MD, Williams CJ, Grandal I, Karaskova J, Squire JA, Rutka JT, Guidos CJ, Danska JS. The RAG-1/2 endonuclease causes genomic instability and controls CNS complications of lymphoblastic leukemia in p53/Prkdc-deficient mice. Cancer Cell 2003; 3:37-50. [PMID: 12559174 DOI: 10.1016/s1535-6108(02)00236-2] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Double-strand DNA breaks (DSB) induce chromosomal translocations and gene amplification in cell culture, but mechanisms by which DSB cause genomic instability in vivo are poorly understood. We show that RAG-1/2-induced DSB cause IgH/c-Myc translocations in leukemic pro-B cells from p53/Prkdc-deficient mice. Strikingly, these translocations were complex, clonally heterogeneous and amplified. We observed reiterated IgH/c-Myc fusions on dicentric chromosomes, suggesting that amplification occurred by repeated cycles of bridge, breakage and fusion. Leukemogenesis was not mitigated in RAG-2/p53/Prkdc-deficient mice, but leukemic pro-B cells lacked IgH/c-Myc translocations. Thus, global genomic instability conferred by p53/Prkdc disruption efficiently transforms pro-B cells lacking RAG-1/2-induced DSB. Unexpectedly, RAG-2/p53/Prkdc-deficient mice also developed leptomeningeal leukemia, providing a novel spontaneous model for this frequent complication of human lymphoblastic malignancies.
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MESH Headings
- Animals
- Blotting, Northern
- Blotting, Southern
- Cell Transformation, Neoplastic/genetics
- Central Nervous System Diseases/etiology
- Central Nervous System Diseases/pathology
- DNA-Binding Proteins/deficiency
- DNA-Binding Proteins/genetics
- Flow Cytometry
- Gene Amplification/genetics
- Genes, myc/genetics
- Hematopoietic Stem Cell Transplantation
- Hematopoietic Stem Cells/physiology
- Homeodomain Proteins/genetics
- Immunoglobulin Heavy Chains/genetics
- Immunohistochemistry
- In Situ Hybridization, Fluorescence
- Leukemia, Lymphoid/complications
- Leukemia, Lymphoid/genetics
- Leukemia, Lymphoid/physiopathology
- Meningeal Neoplasms/etiology
- Meningeal Neoplasms/genetics
- Mice
- Models, Animal
- Translocation, Genetic
- Tumor Suppressor Protein p53/deficiency
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Affiliation(s)
- Rebecca A Gladdy
- Program in Developmental Biology, The Hospital for Sick Children and Department of Surgery, University of Toronto, Toronto, Ontario, Canada
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717
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Abstract
Pancreatic ductal adenocarcinoma is an aggressive and devastating disease, which is characterized by invasiveness, rapid progression and profound resistance to treatment. Advances in pathological classification and cancer genetics have improved our descriptive understanding of this disease; however, important aspects of pancreatic cancer biology remain poorly understood. What is the pathogenic role of specific gene mutations? What is the cell of origin? And how does the stroma contribute to tumorigenesis? A better understanding of pancreatic cancer biology should lead the way to more effective treatments.
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Affiliation(s)
- Nabeel Bardeesy
- Department of Adult Oncology, Dana-Farber Cancer Institute and Departments of Medicine and Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
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718
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Lo AWI, Sabatier L, Fouladi B, Pottier G, Ricoul M, Murnane JP. DNA amplification by breakage/fusion/bridge cycles initiated by spontaneous telomere loss in a human cancer cell line. Neoplasia 2002; 4:531-8. [PMID: 12407447 PMCID: PMC1503667 DOI: 10.1038/sj.neo.7900267] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2002] [Accepted: 07/24/2002] [Indexed: 11/09/2022]
Abstract
The development of genomic instability is an important step in generating the multiple genetic changes required for cancer. One consequence of genomic instability is the overexpression of oncogenes due to gene amplification. One mechanism for gene amplification is the breakage/fusion/bridge (B/F/B) cycle that involves the repeated fusion and breakage of chromosomes following the loss of a telomere. B/F/B cycles have been associated with low-copy gene amplification in human cancer cells, and have been proposed to be an initiating event in high-copy gene amplification. We have found that spontaneous telomere loss on a marker chromosome 16 in a human tumor cell line results in sister chromatid fusion and prolonged periods of chromosome instability. The high rate of anaphase bridges involving chromosome 16 demonstrates that this instability results from B/F/B cycles. The amplification of subtelomeric DNA on the marker chromosome provides conclusive evidence that B/F/B cycles initiated by spontaneous telomere loss are a mechanism for gene amplification in human cancer cells.
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Affiliation(s)
- Anthony W I Lo
- Radiation Oncology Research Laboratory, University of California, 1855 Folsom Street, MCB 200, San Francisco, CA 94103, USA
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719
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Telomere shortening is nearly universal in pancreatic intraepithelial neoplasia. THE AMERICAN JOURNAL OF PATHOLOGY 2002; 161:1541-7. [PMID: 12414502 PMCID: PMC1850788 DOI: 10.1016/s0002-9440(10)64432-x] [Citation(s) in RCA: 276] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A multistep model of carcinogenesis has recently been proposed for pancreatic ductal adenocarcinomas. In this model, noninvasive precursor lesions in the pancreatic ductules accumulate genetic alterations in cancer-associated genes eventually leading to the development of an invasive cancer. The nomenclature for these precursor lesions has been standardized as pancreatic intraepithelial neoplasia or PanIN. Despite the substantial advances made in understanding the biology of invasive pancreatic adenocarcinomas, little is known about the initiating genetic events in the pancreatic ductal epithelium that facilitates its progression to cancer. Telomeres are distinctive structures at the ends of chromosomes that protect against chromosomal breakage-fusion-bridge cycles in dividing cells. Critically shortened telomeres can cause chromosomal instability, a sine qua non of most human epithelial cancers. Although evidence for telomeric dysfunction has been demonstrated in invasive pancreatic cancer, the onset of this phenomenon has not been elucidated in the context of noninvasive precursor lesions. We used a recently described in situ hybridization technique in archival samples (Meeker AK, Gage WR, Hicks JL, Simon I, Coffman JR, Platz EA, March GE, De Marzo AM: Telomere length assessment in human archival tissues: combined telomere fluorescence in situ hybridization and immunostaining. American Journal of Pathology 2002, 160:1259-1268) for assessment of telomere length in tissue microarrays containing a variety of noninvasive pancreatic ductal lesions. These included 82 PanIN lesions of all histological grades (24 PanIN-1A, 23 PanIN-1B, 24 PanIN-2, and 11 PanIN-3) that were selected from pancreatectomy specimens for either adenocarcinoma or chronic pancreatitis. Telomere fluorescence intensities in PanIN lesions were compared with adjacent normal pancreatic ductal epithelium and acini (62 of 82 lesions, 76%), or with stromal fibroblasts and islets of Langerhans (20 of 82 lesions, 24%). Telomere signals were strikingly reduced in 79 (96%) of 82 PanINs compared to adjacent normal structures. Notably, even PanIN-1A, the earliest putative precursor lesion, demonstrated a dramatic reduction of telomere fluorescence intensity in 21 (91%) of 23 foci examined. In chronic pancreatitis, reduction of telomere signal was observed in all PanIN lesions, whereas atrophic and inflammatory ductal lesions retained normal telomere length. Telomere fluorescence intensity in PanIN lesions did not correlate with proliferation measured by quantitative Ki-67-labeling index or topoisomerase IIalpha expression. Thus, telomere shortening is by far the most common early genetic abnormality recognized to date in the progression model of pancreatic adenocarcinomas. Telomeres may be an essential gatekeeper for maintaining chromosomal integrity, and thus, normal cellular physiology in pancreatic ductal epithelium. A critical shortening of telomere length in PanINs may predispose these noninvasive ductal lesions to accumulate progressive chromosomal abnormalities and to develop toward the stage of invasive carcinoma.
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720
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Abstract
The chromosome ends have protective structures that distinguish them from broken chromosomes, known as telomeres. The function of telomeres, and that of the cellular activity that synthesises them, telomerase, are proposed to be biological determinants in the processes of cancer and aging. In this review, we will focus on mammalian telomeres and, in particular, on the analysis of different mouse models for proteins that are important for telomere function, such as telomerase and various telomere-binding proteins. These mouse models have allowed the relevance of telomeres and telomerase in tumour development and the aging of the organism to be directly tested.
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Affiliation(s)
- MarÃa A Blasco
- Department of Immunology and Oncology, National Centre of Biotechnology, E-28049, Madrid, Spain.
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721
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Krtolica A, Campisi J. Cancer and aging: a model for the cancer promoting effects of the aging stroma. Int J Biochem Cell Biol 2002; 34:1401-14. [PMID: 12200035 DOI: 10.1016/s1357-2725(02)00053-5] [Citation(s) in RCA: 203] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The incidence of cancer rises exponentially with age in humans and many other mammalian species. Malignant tumors are caused by an accumulation of oncogenic mutations. In addition, malignant tumorigenesis requires a permissive tissue environment in which mutant cells can survive, proliferate, and express their neoplastic phenotype. We propose that the age-related increase in cancer results from a synergy between the accumulation of mutations and age-related, pro-oncogenic changes in the tissue milieu. Most age-related cancers derive from the epithelial cells of renewable tissues. An important element of epithelial tissues is the stroma, the sub-epithelial layer composed of extracellular matrix and several cell types. The stroma is maintained, remodeled and repaired by resident fibroblasts, supports and instructs the epithelium, and is essential for epithelial function. One change that occurs in tissues during aging is the accumulation of epithelial cells and fibroblasts that have undergone cellular senescence. Cellular senescence irreversibly arrests proliferation in response to damage or stimuli that put cells at risk for neoplastic transformation. Senescent cells secrete factors that can disrupt tissue architecture and/or stimulate nearby cells to proliferate. We therefore speculate that their presence may create a pro-oncogenic tissue environment that synergizes with oncogenic mutations to drive the rise in cancer incidence with age. Recent evidence lends support to this idea, and suggests that senescent stromal fibroblasts may be particularly adept at creating a tissue environment that can promote the development of age-related epithelial cancers.
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Affiliation(s)
- Ana Krtolica
- Lawrence Berkeley National Laboratory, Life Sciences Division, Mailstop 84-171, 1 Cyclotron Road, Berkeley, CA 94720, USA
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722
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Abstract
Recent data indicate that loss of the protective telomeric capping function leads to active degradation of the telomeric G-strand overhang and DNA ligase IV-mediated non-homologous end joining. These molecular events may contribute to genomic instability early in tumorigenesis.
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Affiliation(s)
- Alison A Bertuch
- Department of Pediatrics, Hematology/Oncology Section, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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723
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Opitz OG, Harada H, Suliman Y, Rhoades B, Sharpless NE, Kent R, Kopelovich L, Nakagawa H, Rustgi AK. A mouse model of human oral-esophageal cancer. J Clin Invest 2002. [PMID: 12235107 DOI: 10.1172/jci0215324] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Squamous cancers of the oral cavity and esophagus are common worldwide, but no good genetically based animal model exists. A number of environmental factors as well as genetic alterations have been identified in these cancers, yet the specific combination of genetic events required for cancer progression remains unknown. The Epstein-Barr virus ED-L2 promoter (L2) can be used to target genes in a specific fashion to the oral-esophageal squamous epithelium. To that end, we generated L2-cyclin D1 (L2D1(+)) mice and crossbred these with p53-deficient mice. Whereas L2D1(+) mice exhibit a histologic phenotype of oral-esophageal dysplasia, the combination of cyclin D1 expression and p53 deficiency results in invasive oral-esophageal cancer. The development of the precancerous lesions was significantly reversed by the application of sulindac in the drinking water of the L2D1(+)/p53(+/-) mice. Furthermore, cell lines derived from oral epithelia of L2D1(+)/p53(+/-) and L2D1(+)/p53(-/-) mice, but not control mice, formed tumors in athymic nude mice. These data demonstrate that L2D1(+)/p53(+/-) mice provide a well-defined, novel, and faithful model of oral-esophageal cancer, which allows for the testing of novel chemopreventive, diagnostic, and therapeutic approaches.
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Affiliation(s)
- Oliver G Opitz
- Division of Gastroenterology, Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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724
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Masuda A, Takahashi T. Chromosome instability in human lung cancers: possible underlying mechanisms and potential consequences in the pathogenesis. Oncogene 2002; 21:6884-97. [PMID: 12362271 DOI: 10.1038/sj.onc.1205566] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Chromosomal abnormality is one of the hallmarks of neoplastic cells, and the persistent presence of chromosome instability (CIN) has been demonstrated in human cancers, including lung cancer. Recent progress in molecular and cellular biology as well as cytogenetics has shed light on the underlying mechanisms and the biological and clinical significance of chromosome abnormalities and the CIN phenotype. Chromosome abnormalities can be classified broadly into numerical (i.e., aneuploidy) and structural alterations (e.g., deletion, translocation, homogenously staining region (HSR), double minutes (DMs)). However, both alterations usually occur in the same cells, suggesting some overlap in their underlying mechanisms. Missegregation of chromosomes may result from various causes, including defects of mitotic spindle checkpoint, abnormal centrosome formation and failure of cytokinesis, while structural alterations of chromosomes may be caused especially by failure in the repair of DNA double-strand breaks (DSBs) due to the impairment of DNA damage checkpoints and/or DSB repair systems. Recent studies also suggest that telomere erosion may be involved. The consequential acquisition of the CIN phenotype would give lung cancer cells an excellent opportunity to efficiently alter their characteristics so as to be more malignant and suitable to their microenvironment, thereby gaining a selective growth advantage.
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Affiliation(s)
- Akira Masuda
- Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan
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725
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O'Sullivan JN, Bronner MP, Brentnall TA, Finley JC, Shen WT, Emerson S, Emond MJ, Gollahon KA, Moskovitz AH, Crispin DA, Potter JD, Rabinovitch PS. Chromosomal instability in ulcerative colitis is related to telomere shortening. Nat Genet 2002; 32:280-4. [PMID: 12355086 DOI: 10.1038/ng989] [Citation(s) in RCA: 267] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2002] [Accepted: 08/05/2002] [Indexed: 12/16/2022]
Abstract
Ulcerative colitis, a chronic inflammatory disease of the colon, is associated with a high risk of colorectal carcinoma that is thought to develop through genomic instability. We considered that the rapid cell turnover and oxidative injury observed in ulcerative colitis might accelerate telomere shortening, thereby increasing the potential of chromosomal ends to fuse, resulting in cycles of chromatin bridge breakage and fusion and chromosomal instability associated with tumor cell progression. Here we have used quantitative fluorescence in situ hybridization to compare chromosomal aberrations and telomere shortening in non-dysplastic mucosa taken from individuals affected by ulcerative colitis, either with (UC progressors) or without (UC non-progressors) dysplasia or cancer. Losses, but not gains, of chromosomal arms and centromeres are highly correlated with telomere shortening. Chromosomal losses are greater and telomeres are shorter in biopsy samples from UC progressors than in those from UC non-progressors or control individuals without ulcerative colitis. A mechanistic link between telomere shortening and chromosomal instability is supported by a higher frequency of anaphase bridges--an intermediate in the breakage and fusion of chromatin bridges--in UC progressors than in UC non-progressors or control individuals. Our study shows that telomere length is correlated with chromosomal instability in a precursor of human cancer.
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Affiliation(s)
- Jacintha N O'Sullivan
- Department of Pathology, University of Washington, Seattle, Washington 98195-7705, USA
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726
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Arias-Pulido H, Narayan G, Vargas H, Mansukhani M, Murty VVVS. Mapping common deleted regions on 5p15 in cervical carcinoma and their occurrence in precancerous lesions. Mol Cancer 2002; 1:3. [PMID: 12392596 PMCID: PMC140145 DOI: 10.1186/1476-4598-1-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2002] [Accepted: 10/01/2002] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Previous studies have shown that the short arm of chromosome 5 (5p) exhibit frequent genetic changes in invasive cervical carcinoma (CC), and that these changes arise early during the carcinogenesis, in precancerous lesions. These data therefore suggest that loss of candidate tumor suppressor genes located on 5p is associated with the development of CC. However, the precise location of 5p deletions is not known. RESULTS We performed a detailed deletion mapping of 5p in 60 cases of invasive CC. We found that 60% of the tumors exhibit a 5p loss of heterozygosity (LOH). The patterns of LOH allowed us to identify two minimal regions of deletions, one at 5p15.3 spanning a 5.5 cM genetic distance and a second site of 7 cM at 5p15.2-15.3. In addition, we also identified 5p deletions in 16% lesions of high-grade cervical intraepithelial neoplasia (CIN). 5p LOH was found in 63% of HPV 16 positive tumors, while only 33% tumors with other HPV-types had 5p LOH. The differences in frequency of 5p LOH between tumors harboring HPV16 in combination with other HPV types and tumors harboring HPV16 DNA alone were significantly higher, suggesting a synergistic effect of high-risk types in causing genomic instability. CONCLUSION These findings implicate the presence of tumor suppressor gene(s) on 5p relevant to CC tumorigenesis.
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Affiliation(s)
- Hugo Arias-Pulido
- Department of Pathology, College of Physicians & Surgeons of Columbia University, 630 West 168 Street, New York, 10032, USA
- Department of Tumor Molecular Biology, Instituto Nacional de CancerologÃa, Cl. 1 No 9-85, Bogotá, Colombia
- Department of Molecular Genetics and Microbiology, BRF 123, School of Medicine, 915 Camino de Salud, NE., Albuquerque, NM, 87131, USA
| | - Gopeshwar Narayan
- Department of Pathology, College of Physicians & Surgeons of Columbia University, 630 West 168 Street, New York, 10032, USA
| | - Hernan Vargas
- Department of Tumor Molecular Biology, Instituto Nacional de CancerologÃa, Cl. 1 No 9-85, Bogotá, Colombia
| | - Mahesh Mansukhani
- Department of Pathology, College of Physicians & Surgeons of Columbia University, 630 West 168 Street, New York, 10032, USA
| | - Vundavalli VVS Murty
- Department of Pathology, College of Physicians & Surgeons of Columbia University, 630 West 168 Street, New York, 10032, USA
- Institute for Cancer Genetics, College of Physicians & Surgeons of Columbia University, 630 West 168 Street, New York, 10032, USA
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727
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Opitz OG, Harada H, Suliman Y, Rhoades B, Sharpless NE, Kent R, Kopelovich L, Nakagawa H, Rustgi AK. A mouse model of human oral-esophageal cancer. J Clin Invest 2002; 110:761-9. [PMID: 12235107 PMCID: PMC151126 DOI: 10.1172/jci15324] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Squamous cancers of the oral cavity and esophagus are common worldwide, but no good genetically based animal model exists. A number of environmental factors as well as genetic alterations have been identified in these cancers, yet the specific combination of genetic events required for cancer progression remains unknown. The Epstein-Barr virus ED-L2 promoter (L2) can be used to target genes in a specific fashion to the oral-esophageal squamous epithelium. To that end, we generated L2-cyclin D1 (L2D1(+)) mice and crossbred these with p53-deficient mice. Whereas L2D1(+) mice exhibit a histologic phenotype of oral-esophageal dysplasia, the combination of cyclin D1 expression and p53 deficiency results in invasive oral-esophageal cancer. The development of the precancerous lesions was significantly reversed by the application of sulindac in the drinking water of the L2D1(+)/p53(+/-) mice. Furthermore, cell lines derived from oral epithelia of L2D1(+)/p53(+/-) and L2D1(+)/p53(-/-) mice, but not control mice, formed tumors in athymic nude mice. These data demonstrate that L2D1(+)/p53(+/-) mice provide a well-defined, novel, and faithful model of oral-esophageal cancer, which allows for the testing of novel chemopreventive, diagnostic, and therapeutic approaches.
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MESH Headings
- Animals
- Antineoplastic Agents/therapeutic use
- Cyclin D1/genetics
- Cyclin D1/metabolism
- Disease Models, Animal
- ErbB Receptors/genetics
- ErbB Receptors/metabolism
- Esophageal Neoplasms/drug therapy
- Esophageal Neoplasms/genetics
- Esophageal Neoplasms/pathology
- Genotype
- Herpesvirus 4, Human/genetics
- Humans
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Nude
- Mice, Transgenic
- Mouth Neoplasms/drug therapy
- Mouth Neoplasms/genetics
- Mouth Neoplasms/pathology
- Neoplasms, Squamous Cell/drug therapy
- Neoplasms, Squamous Cell/genetics
- Neoplasms, Squamous Cell/pathology
- Promoter Regions, Genetic
- Sulindac/therapeutic use
- Tumor Cells, Cultured
- Tumor Suppressor Protein p53/genetics
- Tumor Suppressor Protein p53/metabolism
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Affiliation(s)
- Oliver G Opitz
- Division of Gastroenterology, Abramson Family Cancer Research Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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728
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Abstract
Programmed telomere shortening in human somatic cells is thought to act as a tumor suppressor pathway, limiting the replicative potential of developing tumor cells. Critically short human telomeres induce senescence either by activating p53 or by inducing the p16/RB pathway, and suppression of both pathways is required to suppress senescence of aged human cells. Here we report that removal of TRF2 from human telomeres and the ensuing de-protection of chromosome ends induced immediate premature senescence. Although the telomeric tracts remained intact, the TRF2(DeltaBDeltaM)-induced premature senescence was indistinguishable from replicative senescence and could be mediated by either the p53 or the p16/RB pathway. Telomere de-protection also induced a growth arrest and senescent morphology in mouse cells. However, in this setting the loss of p53 function was sufficient to completely abrogate the arrest, indicating that the p16/RB response to telomere dysfunction is not active in mouse cells. These findings reveal a fundamental difference in telomere damage signaling in human and mouse cells that bears on the use of mouse models for the telomere tumor suppressor pathway.
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Affiliation(s)
| | - Titia de Lange
- Laboratory for Cell Biology and Genetics, The Rockefeller University, 1230 York Avenue, NY 10021, USA
Corresponding author e-mail:
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729
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O'Hagan RC, Chang S, Maser RS, Mohan R, Artandi SE, Chin L, DePinho RA. Telomere dysfunction provokes regional amplification and deletion in cancer genomes. Cancer Cell 2002; 2:149-55. [PMID: 12204535 DOI: 10.1016/s1535-6108(02)00094-6] [Citation(s) in RCA: 166] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Telomere dysfunction and associated fusion-breakage in the mouse encourages epithelial carcinogenesis and a more humanized genomic profile that includes nonreciprocal translocations (NRTs). Here, array comparative genomic hybridization was used to determine the pathogenic significance of NRTs and to determine whether telomere dysfunction also drives amplifications and deletions of cancer-relevant loci. Compared to tumors arising in mice with intact telomeres, tumors with telomere dysfunction possessed higher levels of genomic instability and showed numerous amplifications and deletions in regions syntenic to human cancer hotspots. These observations suggest that telomere-based crisis provides a mechanism of chromosomal instability, including regional amplifications and deletions, that drives carcinogenesis. This model provides a platform for discovery of genes responsible for the major cancers affecting aged humans.
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Affiliation(s)
- Rónán C O'Hagan
- Department of Adult Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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730
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Abstract
Cancer is a disease of impaired genome stability. The molecular forces that maintain genome integrity and sense altered chromosome structure are invariably subverted in cancer cells. Here, we explore the contrasting contributions of telomeres in the initiation and suppression of cancer and review the evidence supporting a role for telomere dysfunction as a mechanism driving the radical chromosomal aberrations that typify cancer genomes. Recent work suggests that passage of cells through crisis in the setting of deactivated DNA damage checkpoints provides a mutational mechanism that can generate the diverse genetic alterations required for cancer initiation. A greater understanding of telomere-induced crisis and the cell's crisis management mechanisms should guide the rational development of new therapeutics for cancer and other disorders.
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Affiliation(s)
- Richard S Maser
- Department of Adult Oncology, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street, M413, Boston, MA 02115, USA
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731
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Gisselsson D, Jonson T, Yu C, Martins C, Mandahl N, Wiegant J, Jin Y, Mertens F, Jin C. Centrosomal abnormalities, multipolar mitoses, and chromosomal instability in head and neck tumours with dysfunctional telomeres. Br J Cancer 2002; 87:202-7. [PMID: 12107843 PMCID: PMC2376110 DOI: 10.1038/sj.bjc.6600438] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2002] [Revised: 05/01/2002] [Accepted: 05/08/2002] [Indexed: 11/08/2022] Open
Abstract
Carcinomas of the head and neck typically exhibit complex chromosome aberrations but the underlying mutational mechanisms remain obscure. Evaluation of cell division dynamics in low-passage cell lines from three benign and five malignant head and neck tumours revealed a strong positive correlation between multipolarity of the mitotic spindle and the formation of bridges at anaphase in both benign and malignant tumours. Cells exhibiting a high rate of mitotic abnormalities also showed several chromosome termini lacking TTAGGG repeats and a high frequency of dicentric chromosomes. Multicolour karyotyping demonstrated a preferential involvement in structural rearrangements of chromosomes with deficient telomeres. The majority of malignant, mitotically unstable tumours expressed the reverse transcriptase subunit of telomerase. These data indicate that some of the genomic instability in head and neck tumours is initiated by telomere dysfunction, leading to the formation of dicentric chromosomes. These form chromosome bridges at mitosis that could prevent the normal anaphase-telophase transition. In turn, this may cause an accumulation of centrosomes and mitotic multipolarity. Telomerase expression does not confer total stability to the tumour genome but could be crucial for moderating the rate of chromosomal evolution.
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Affiliation(s)
- D Gisselsson
- Department of Clinical Genetics, University Hospital, SE-221 85 Lund, Sweden.
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732
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Lo AWI, Sprung CN, Fouladi B, Pedram M, Sabatier L, Ricoul M, Reynolds GE, Murnane JP. Chromosome instability as a result of double-strand breaks near telomeres in mouse embryonic stem cells. Mol Cell Biol 2002; 22:4836-50. [PMID: 12052890 PMCID: PMC133890 DOI: 10.1128/mcb.22.13.4836-4850.2002] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Telomeres are essential for protecting the ends of chromosomes and preventing chromosome fusion. Telomere loss has been proposed to play an important role in the chromosomal rearrangements associated with tumorigenesis. To determine the relationship between telomere loss and chromosome instability in mammalian cells, we investigated the events resulting from the introduction of a double-strand break near a telomere with I-SceI endonuclease in mouse embryonic stem cells. The inactivation of a selectable marker gene adjacent to a telomere as a result of the I-SceI-induced double-strand break involved either the addition of a telomere at the site of the break or the formation of inverted repeats and large tandem duplications on the end of the chromosome. Nucleotide sequence analysis demonstrated large deletions and little or no complementarity at the recombination sites involved in the formation of the inverted repeats. The formation of inverted repeats was followed by a period of chromosome instability, characterized by amplification of the subtelomeric region, translocation of chromosomal fragments onto the end of the chromosome, and the formation of dicentric chromosomes. Despite this heterogeneity, the rearranged chromosomes eventually acquired telomeres and were stable in most of the cells in the population at the time of analysis. Our observations are consistent with a model in which broken chromosomes that do not regain a telomere undergo sister chromatid fusion involving nonhomologous end joining. Sister chromatid fusion is followed by chromosome instability resulting from breakage-fusion-bridge cycles involving the sister chromatids and rearrangements with other chromosomes. This process results in highly rearranged chromosomes that eventually become stable through the addition of a telomere onto the broken end. We have observed similar events after spontaneous telomere loss in a human tumor cell line, suggesting that chromosome instability resulting from telomere loss plays a role in chromosomal rearrangements associated with tumor cell progression.
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Affiliation(s)
- Anthony W. I. Lo
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Carl N. Sprung
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Bijan Fouladi
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Mehrdad Pedram
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Laure Sabatier
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Michelle Ricoul
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - Gloria E. Reynolds
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
| | - John P. Murnane
- Radiation Oncology Research Laboratory, University of California, San Francisco, California 94103, Laboratoire de Radiobiologie et Oncologie, Commissariat à l'Energie Atomique, Fontenay-aux-Roses, France
- Corresponding author. Mailing address: Department of Radiation Oncology, University of California, 1855 Folsom St., MCB 200, San Francisco, CA 94103. Phone: (415) 476-9083. Fax: (415) 476-9069. E-mail:
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733
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Abstract
Replicative aging is the process by which most normal human cells "count" the number of times they have divided, eventually undergoing a growth arrest termed cellular senescence. This process is dependent on the shortening of telomeres, repeated sequences at the ends of the chromosomes. The loss of telomeric sequences with each cell division eventually induces a growth arrest that has a similar phenotype to that of cells stressed by inadequate culture or other conditions. Experiments over the past several years have identified species in which replicative aging does not occur and many examples in which a failure to proliferate has been misinterpreted as replicative senescence. Insights from these studies now permit a reevaluation of much of the seemingly contradictory data concerning replicative aging. There are good theoretical reasons for believing a limited proliferative capacity contributes to declining tissue homeostasis with increasing age. Although the presence of telomere shortening provides strong circumstantial evidence that replicative aging is occurring in vivo, thus far there is only very limited direct evidence for actual physiological effects of replicative aging.
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Affiliation(s)
- Woodring E Wright
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA.
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734
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Abstract
Most mammalian cells-excepting germ cells, tumor cells, and stem cells, that is-possess a finite replicative life span, manifested by the eventual cessation of cell proliferation. Clinically, this is germane not just to the overt derangements of cell growth in cancer, but also to organs such as the heart, in which the capacity for cell replacement and repair is insufficient to maintain organ function following cell death. Among the intrinsic mechanisms that control a conserved program of replicative senescence is the enzyme telomerase, which synthesizes the telomeric repeat for end-capping of each chromosome. The implications of telomerase for cardiac growth have recently begun to be defined. Other functions of telomerase, in maintaining genome integrity, also hold importance for cardiac muscle, as a novel means to suppress apoptosis and, thus, salvage myocardium following ischemic injury.
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Affiliation(s)
- Hidemasa Oh
- Department of Medicine, Center for Cardiovascular Development, Baylor College of Medicine, Houston, Texas, 77030, USA
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735
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Rubin H. The disparity between human cell senescence in vitro and lifelong replication in vivo. Nat Biotechnol 2002; 20:675-81. [PMID: 12089551 DOI: 10.1038/nbt0702-675] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cultured human fibroblasts undergo senescence (a loss of replicative capacity) after a uniform, fixed number of approximately 50 population doublings, commonly termed the Hayflick limit. It has been long known from clonal and other quantitative studies, however, that cells decline in replicative capacity from the time of explantation and do so in a stochastic manner, with a half-life of only approximately 8 doublings. The apparent 50-cell doubling limit reflects the expansive propagation of the last surviving clone. The relevance of either figure to survival of cells in the body is questionable, given that stem cells in some renewing tissues undergo >1,000 divisions in a lifetime with no morphological sign of senescence. Oddly enough, these observations have had little if any effect on general acceptance of the Hayflick limit in its original form. The absence of telomerase in cultured human cells and the shortening of telomeres at each population doubling have suggested that telomere length acts as a mitotic clock that accounts for their limited lifespan. This concept assumed an iconic character with the report that ectopic expression of telomerase by a vector greatly extended the lifespan of human cells. That something similar might occur in vivo seemed consistent with initial reports that most human somatic tissues lack telomerase activity. More careful study, however, has revealed telomerase activity in stem cells and some dividing transit cells of many renewing tissues and even in dividing myocytes of repairing cardiac muscle. It now seems likely that telomerase is active in vivo where and when it is needed to maintain tissue integrity. Caution is recommended in applying telomerase inhibition to kill telomerase-expressing cancer cells, because it would probably damage stem cells in essential organs and even increase the likelihood of secondary cancers. The risk may be especially high in sun-exposed skin, where there are usually thousands of p53-mutant clones of keratinocytes predisposed to cancer.
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Affiliation(s)
- Harry Rubin
- Department of Molecular and Cell Biology, Life Sciences Addition, University of California, Berkeley, CA 94720-3200, USA.
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736
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Herzig M, Christofori G. Recent advances in cancer research: mouse models of tumorigenesis. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1602:97-113. [PMID: 12020798 DOI: 10.1016/s0304-419x(02)00039-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Over the past 20 years, cancer research has gained major insights into the complexity of tumor development, in particular into the molecular mechanisms that underlie the progressive transformation of normal cells into highly malignant derivatives. It is estimated that the transformation of a normal cell to a malignant tumor cell is dependent upon a small number of genetic alterations, estimated to be within the range of four to seven rate-limiting events. Critical events in the evolution of neoplastic disease include the loss of proliferative control, the failure to undergo programmed cell death (apoptosis), the onset of neoangiogenesis, tissue remodeling, invasion of tumor cells into surrounding tissue and, finally, metastatic dissemination of tumor cells to distant organs. In patients, the molecular analysis of these multiple steps is hampered by the unavailability of tumor biopsies from all tumor stages. In contrast, mouse models of tumorigenesis allow the reproducible isolation of all tumor stages, including normal tissue, which are then amenable to pathological, genetic and biochemical analyses and, hence, have been instrumental in investigating cancer-related genes and their role in carcinogenesis. In this review, we discuss mouse tumor models that have contributed substantially to the identification and characterization of novel tumor pathways. In particular, we focus on transgenic and knockout mouse models that closely mimic human cancer and thus can be used as model systems for cancer research.
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737
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Artandi SE, Alson S, Tietze MK, Sharpless NE, Ye S, Greenberg RA, Castrillon DH, Horner JW, Weiler SR, Carrasco RD, DePinho RA. Constitutive telomerase expression promotes mammary carcinomas in aging mice. Proc Natl Acad Sci U S A 2002; 99:8191-6. [PMID: 12034875 PMCID: PMC123043 DOI: 10.1073/pnas.112515399] [Citation(s) in RCA: 249] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Telomerase is up-regulated in the vast majority of human cancers and serves to halt the progressive telomere shortening that ultimately blocks would-be cancer cells from achieving a full malignant phenotype. In contrast to humans, the laboratory mouse possesses long telomeres and, even in early generation telomerase-deficient mice, the level of telomere reserve is sufficient to avert telomere-based checkpoint responses and to permit full malignant progression. These features in the mouse provide an opportunity to determine whether enforced high-level telomerase activity can serve functions that extend beyond its ability to sustain telomere length and function. Here, we report the generation and characterization of transgenic mice that express the catalytic subunit of telomerase (mTERT) at high levels in a broad variety of tissues. Expression of mTERT conferred increased telomerase enzymatic activity in several tissues, including mammary gland, splenocytes, and cultured mouse embryonic fibroblasts. In mouse embryonic fibroblasts, mTERT overexpression extended telomere lengths but did not prevent culture-induced replicative arrest, thus reinforcing the view that this phenomenon is not related to occult telomere shortening. Robust telomerase activity, however, was associated with the spontaneous development of mammary intraepithelial neoplasia and invasive mammary carcinomas in a significant proportion of aged females. These data indicate that enforced mTERT expression can promote the development of spontaneous cancers even in the setting of ample telomere reserve.
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Affiliation(s)
- Steven E Artandi
- Department of Adult Oncology, Dana-Farber Cancer Institute, Harvard Medical School, 44 Binney Street (M413), Boston, MA 02115, USA
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738
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Moriarty TJ, Dupuis S, Autexier C. Rapid upregulation of telomerase activity in human leukemia HL-60 cells treated with clinical doses of the DNA-damaging drug etoposide. Leukemia 2002; 16:1112-20. [PMID: 12040441 PMCID: PMC5235897 DOI: 10.1038/sj.leu.2402522] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2001] [Accepted: 02/14/2002] [Indexed: 11/09/2022]
Abstract
The enzyme telomerase is implicated in cellular resistance to apoptosis, but the mechanism for this resistance remains to be elucidated. The ability of telomerase to synthesize new DNA at telomeres suggests that this enzyme might function in the repair of double-stranded DNA breaks. To distinguish the effects of double-stranded DNA break damage and apoptosis on human telomerase activity, we treated the HL-60 human hematopoietic cancer cell line with clinical doses of the chemotherapeutic drug etoposide (0.5 to 5 microM), which allowed us to distinguish between events associated with DNA damage-induced cell cycle arrest, and events associated with apoptosis. Large (three- to seven-fold) upregulation of telomerase activity occurred soon after etoposide treatment (3 h) in S/G2/M-arresting populations; this upregulation was abolished at onset of apoptotic cell death. No upregulation of telomerase activity was observed in cells treated with a larger dose of etoposide (5 microM) that caused cells to undergo rapid apoptosis without intervening cell cycle arrests. These observations are consistent with a possible role for telomerase upregulation during the DNA damage response.
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MESH Headings
- Antineoplastic Agents, Phytogenic/administration & dosage
- Antineoplastic Agents, Phytogenic/pharmacology
- Antineoplastic Agents, Phytogenic/toxicity
- Apoptosis
- Cell Cycle
- Cell Nucleus/ultrastructure
- DNA Damage
- DNA Fragmentation
- DNA, Neoplasm/genetics
- DNA, Neoplasm/ultrastructure
- Diploidy
- Dose-Response Relationship, Drug
- Enzyme Activation
- Etoposide/administration & dosage
- Etoposide/pharmacology
- Etoposide/toxicity
- HL-60 Cells
- Humans
- Kinetics
- Leukemia, Promyelocytic, Acute/enzymology
- Leukemia, Promyelocytic, Acute/genetics
- Leukemia, Promyelocytic, Acute/pathology
- Telomerase/metabolism
- Up-Regulation
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Affiliation(s)
- T J Moriarty
- Department of Anatomy and Cell Biology, McGill University, Montréal, Québec, Canada
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739
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Abstract
Telomeres must protect chromosome ends from being recognized and processed as double-strand breaks. Identification of the factors involved in end protection, and the mechanisms by which they "cap" chromosome termini, is crucial in understanding how the cell distinguishes between a double-strand break and a normal telomere end. Recent work has characterized the similarities and potential differences between the pathways utilized by multiple organisms in maintaining telomere ends. One unifying concept that has clearly emerged is that chromosome-end protection is necessary in maintaining genetic stability and preventing oncogenesis.
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Affiliation(s)
- Rachel B Cervantes
- Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA
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740
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Crompton NEA, Shi YQ, Wuergler F, Blattmann H. A single low dose of X-rays induces high frequencies of genetic instability (aneuploidy) and heritable damage (apoptosis), dependent on cell type and p53 status. Mutat Res 2002; 517:173-86. [PMID: 12034319 DOI: 10.1016/s1383-5718(02)00068-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We harvested and analyzed cells from four different non-transformed cell lines surviving a single X-ray exposure. Evidence of radiation-induced karyotype instability was observed in 100% of C3H 10T1/2 fibroblast clones and 11.3% of V79 fibroblast clones. Heritable damage: predisposition to apoptosis, but not karyotype instability, was induced in TK6 (p53(wt/wt)) and WTK1 (p53(mut/mut)) human B-lymphoblastoid cell clones. The studies indicate: (1) genetic instability and/or heritable damage are induced in cells exposed to radiation at a high frequency, and induction of genetic instability is not limited to morphologically transformed cells [Radiat. Res. 138 (1994) S105; Radiat. Environ. Biophys. 36 (1998) 255]; (2) sensitivity to genetic instability and heritable damage depend on cell type; (3) checkpoint stringency and p53 status significantly influence the frequency of radiation-induced genetic instability and heritable damage; (4) in some cell lines, damage induced by low doses of radiation (below 2 Gy) leads to heritable cytotoxic and genotoxic effects in 100% of cells exposed. The data suggest that mammalian cells misinterpret damage induced by ionizing radiation as if it were a physiological cell signal. This contrasts strongly with the response of mammalian cells to damage induced by other types of DNA-toxic agents where damage-specific repair mechanisms are activated.
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Affiliation(s)
- Nigel E A Crompton
- Division of Radiation Medicine, Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland.
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741
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Kawai K, Viars C, Arden K, Tarin D, Urquidi V, Goodison S. Comprehensive karyotyping of the HT-29 colon adenocarcinoma cell line. Genes Chromosomes Cancer 2002; 34:1-8. [PMID: 11921276 DOI: 10.1002/gcc.10003] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The tumor cell line HT-29 was derived from a primary adenocarcinoma of the rectosigmoid colon. HT-29 is hypertriploid (3n+) and has accumulated numerous chromosomal structural aberrations. To identify material involved in chromosome rearrangements, we performed a comprehensive cytogenetic analysis using G-banding, spectral karyotyping (SKY), and fluorescence in situ hybridization (FISH). The combination of molecular cytogenetic techniques enabled us to define the first comprehensive karyotype for HT-29. Seventeen marker chromosomes were found in 75-100% of metaphase cells, generally in a single copy per cell. We confirmed the composition of eight previously described markers, refined the classification of seven others, and identified two novel marker chromosomes. Notable aberrations included a reciprocal translocation between chromosomes 6 and 14 and an unusual, large derivative chromosome 8 composed entirely of 8q material. The telomere status, evaluated by FISH, revealed telomeric signals at the termini of all chromosomes. No interstitial telomeric sequences were observed in any cell. Although numerous chromosomal aberrations are present in HT-29, the cell line appears to have retained a high level of genomic stability during passage in culture since undergoing transformation. The excellent resolving power of SKY, coupled with additional information obtained from molecular cytogenetic analyses, will improve our ability to identify genetic lesions characteristic of cancer.
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Affiliation(s)
- Kanji Kawai
- UCSD Cancer Center and Department of Pathology, University of California San Diego, La Jolla, California 92093-0912, USA
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742
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Abstract
Cancer arises from a stepwise accumulation of genetic changes that liberates neoplastic cells from the homeostatic mechanisms that govern normal cell proliferation. In humans, at least four to six mutations are required to reach this state, but fewer seem to be required in mice. By rationalizing the shared and unique elements of human and mouse models of cancer, we should be able to identify the molecular circuits that function differently in humans and mice, and use this knowledge to improve existing models of cancer.
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Affiliation(s)
- William C Hahn
- Whitehead Institute for Biomedical Research, Massachusetts 02142, USA.
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743
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Vafa O, Wade M, Kern S, Beeche M, Pandita TK, Hampton GM, Wahl GM. c-Myc can induce DNA damage, increase reactive oxygen species, and mitigate p53 function: a mechanism for oncogene-induced genetic instability. Mol Cell 2002; 9:1031-44. [PMID: 12049739 DOI: 10.1016/s1097-2765(02)00520-8] [Citation(s) in RCA: 656] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Oncogene overexpression activates p53 by a mechanism posited to involve uncharacterized hyperproliferative signals. We determined whether such signals produce metabolic perturbations that generate DNA damage, a known p53 inducer. Biochemical, cytological, cell cycle, and global gene expression analyses revealed that brief c-Myc activation can induce DNA damage prior to S phase in normal human fibroblasts. Damage correlated with induction of reactive oxygen species (ROS) without induction of apoptosis. Deregulated c-Myc partially disabled the p53-mediated DNA damage response, enabling cells with damaged genomes to enter the cycle, resulting in poor clonogenic survival. An antioxidant reduced ROS, decreased DNA damage and p53 activation, and improved survival. We propose that oncogene activation can induce DNA damage and override damage controls, thereby accelerating tumor progression via genetic instability.
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Affiliation(s)
- Omid Vafa
- The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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744
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McCaul JA, Gordon KE, Clark LJ, Parkinson EK. Telomerase inhibition and the future management of head-and-neck cancer. Lancet Oncol 2002; 3:280-8. [PMID: 12067805 DOI: 10.1016/s1470-2045(02)00729-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Telomeres are tandem repeats of DNA associated with specific proteins. These structures cap eukaryotic chromosomes and maintain the integrity of the chromosome ends. In the germline, telomeres are maintained by the enzyme telomerase, but in normal somatic cells the enzyme's activity is low or undetectable. Human tumours, including squamous-cell carcinoma of the head and neck (SCCHN), need telomerase to maintain telomere function; inhibition of the enzyme can lead to apoptosis. Furthermore, because most tumour cells have very short telomeres, they are more likely to succumb to telomerase inhibition than normal cells. Telomerase is therefore a potential selective anticancer target. The telomere is also involved in the repair of DNA double strand breaks, and telomere dysfunction provokes radiosensitivity. In this review we consider whether manipulation of telomere function may selectively sensitise SCCHN to radiotherapy and discuss the possible pitfalls. We also assess how some conventional treatments may affect the subsequent use of telomerase inhibitors.
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Affiliation(s)
- James A McCaul
- Maxillofacial surgery, Beatson Institute for Cancer Research, Glasgow, UK.
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745
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Abstract
First-generation mouse tumour models, which used transgenic mice or conventional knockouts, are now being superseded by models that are based on conditional knockouts and mice that carry regulatable oncogenes. In these mice, somatic mutations can be induced in a tissue-specific and time-controlled fashion, which more faithfully mimics sporadic tumour formation. These second-generation models provide exciting new opportunities to gain insight into the contribution of known and unknown genes in the initiation, progression and treatment of cancer, and mimic human cancer better than ever before.
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Affiliation(s)
- Jos Jonkers
- Division of Molecular Genetics, and Centre of Biomedical Genetics, The Netherlands Cancer Institute, Amsterdam
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746
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Abstract
Oncogenes were initially discovered as retrovirally transmitted tumor causing agents. The realization that such retroviral oncogenes constitute specifically altered versions of cellular genes-proto-oncogenes, was a landmark discovery that set the stage for the molecular and mechanistic era of cancer research. Moreover, the studies on oncogene functions have been instrumental in delineating many of the paradigms of cellular signal transduction. In contrast to the original studies in animals, oncogenic activation through retroviral transmission does not appear to be a major factor in human tumorigenesis. However, oncogenes are frequently activated by gain of function mutations or fusions with other genes, or they are aberrantly expressed due to amplification, increased promoter activity, or protein stabilization, and hence they play integral roles in the genesis of human tumors.
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Affiliation(s)
- Karl Münger
- Department of Pathology and Harvard Center for Cancer Biology, Harvard Medical School, Boston, MA 02115-5701, USA.
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747
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Izumi H, Hara T, Oga A, Matsuda K, Sato Y, Naito K, Sasaki K. High telomerase activity correlates with the stabilities of genome and DNA ploidy in renal cell carcinoma. Neoplasia 2002; 4:103-11. [PMID: 11896565 PMCID: PMC1550322 DOI: 10.1038/sj.neo.7900205] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2001] [Accepted: 08/20/2001] [Indexed: 11/09/2022]
Abstract
Malignant tumors have telomerase activity, which is thought to play a critical role in tumor growth. However, the relation between telomerase activity and genomic DNA status in tumor cells is poorly understood. In the present study, we examined telomerase activity in 13 clear cell type renal cell carcinomas (CRCCs) with similar clinicopathologic features by telomeric repeat amplification protocol assay (TRAP). Based on TRAP assay results, we divided the CRCCs into two groups: a high telomerase activity group and a low/no telomerase activity group. We then analyzed genomic aberration, DNA ploidy, and telomere status in these two groups by comparative genomic hybridization (CGH), laser scanning cytometry (LSC), and telomere-specific fluorescence in situ hybridization (T-FISH), respectively. CGH showed the high telomerase activity group to have fewer genomic changes than the low/no telomerase activity group, which had many genomic aberrations. Moreover, with LSC, DNA diploid cells were found more frequently in the high telomerase activity group than in the low/no telomerase activity group. In addition, T-FISH revealed strong telomere signal intensity in the high telomerase activity group compared with that of the low/no telomerase activity group. These results suggest that telomerase activity is linked to genomic DNA status and that high telomerase activity is associated with genomic stability, DNA ploidy, and telomere length in CRCC.
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Affiliation(s)
- Hideki Izumi
- of Pathology, Yamaguchi University School of Medicine, 1-1-1, Minami Kogushi, Ube-city, Yamaguchi, 755-8505, Japan
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748
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Mergny JL, Riou JF, Mailliet P, Teulade-Fichou MP, Gilson E. Natural and pharmacological regulation of telomerase. Nucleic Acids Res 2002; 30:839-65. [PMID: 11842096 PMCID: PMC100331 DOI: 10.1093/nar/30.4.839] [Citation(s) in RCA: 273] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2001] [Revised: 11/29/2001] [Accepted: 11/29/2001] [Indexed: 01/14/2023] Open
Abstract
The extremities of eukaryotic chromosomes are called telomeres. They have a structure unlike the bulk of the chromosome, which allows the cell DNA repair machinery to distinguish them from 'broken' DNA ends. But these specialised structures present a problem when it comes to replicating the DNA. Indeed, telomeric DNA progressively erodes with each round of cell division in cells that do not express telomerase, a specialised reverse transcriptase necessary to fully duplicate the telomeric DNA. Telomerase is expressed in tumour cells but not in most somatic cells and thus telomeres and telomerase may be proposed as attractive targets for the discovery of new anticancer agents.
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Affiliation(s)
- Jean-Louis Mergny
- Laboratoire de Biophysique, Muséum National d'Histoire Naturelle, INSERM U 201, CNRS UMR 8646, 43 rue Cuvier, F-75005 Paris, France.
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749
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Hellman A, Zlotorynski E, Scherer SW, Cheung J, Vincent JB, Smith DI, Trakhtenbrot L, Kerem B. A role for common fragile site induction in amplification of human oncogenes. Cancer Cell 2002; 1:89-97. [PMID: 12086891 DOI: 10.1016/s1535-6108(02)00017-x] [Citation(s) in RCA: 216] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Oncogene amplification is an important process in human tumorigenesis, but its underlying mechanism is currently unknown. Cytogenetic analysis indicates that amplification of drug-selected genes in rodent cells is driven by recurrent breaks within chromosomal common fragile sites (CFSs), via the breakage-fusion-bridge (BFB) mechanism. Here we show that BFB cycles drive the intrachromosomal amplification of the MET oncogene in a human gastric carcinoma. Our molecular evidence includes a "ladder-like" structure and inverted repeat organization of the MET amplicons. Furthermore, we show that the breakpoints, setting the centromeric amplicon boundaries, are within the CFS FRA7G region. Upon replication stress, this region showed perturbed chromatin organization, predisposing it to breakage. Thus, in vivo induction of CFSs can play an important role in human oncogenesis.
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Affiliation(s)
- Asaf Hellman
- Department of Genetics, The Life Sciences Institute, The Hebrew University, Jerusalem 91904, Israel
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750
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Abstract
Genetically engineered mouse models have contributed extensively to the field of cancer research. The ability to manipulate the mouse germline affords numerous approaches toward understanding the complexities of this disease, possibly providing accurate preclinical models for therapeutic and diagnostic advances. This review highlights some of the current strategies for modeling cancer in the mouse, recent accomplishments, and key remaining challenges.
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Affiliation(s)
- Terry Van Dyke
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
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