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Robinson K, Asawachaicharn N, Galloway DA, Grandori C. c-Myc accelerates S-phase and requires WRN to avoid replication stress. PLoS One 2009; 4:e5951. [PMID: 19554081 PMCID: PMC2694031 DOI: 10.1371/journal.pone.0005951] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Accepted: 05/05/2009] [Indexed: 12/31/2022] Open
Abstract
c-Myc interacts with components of the pre-replication complex and directly regulates DNA replication [1]. However the consequences of this novel c-Myc function on cell cycle dynamics and replication-associated damage are unknown. Here, we show that c-Myc overexpression in primary human fibroblasts markedly accelerates S-phase while c-Myc deficient fibroblasts exhibit a prolonged S-phase. We also show that the Werner DNA helicase protein (WRN) plays a critical role in supporting c-Myc-driven S-phase, as depletion of WRN in c-Myc overexpressing cells increases DNA damage specifically at sites of DNA synthesis. This excess DNA damage activates a “replication stress” pathway involving ATR, CHK1, CHK2, and p53, leading to rapid senescence of WRN deficient c-Myc overexpressing cells. Indeed, depletion of p53 rescues this senescence response. We propose that WRN functions to repair abnormal replication structures caused by the acceleration of DNA replication by c-Myc. This work provides an additional mechanistic explanation for c-Myc-induced DNA damage and senescence, and reveals a vulnerability of c-Myc overexpressing cells that could potentially be exploited in cancer therapy.
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Affiliation(s)
- Kristin Robinson
- Program in Cancer Biology and Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Nichaya Asawachaicharn
- Program in Cancer Biology and Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Denise A. Galloway
- Program in Cancer Biology and Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Carla Grandori
- Program in Cancer Biology and Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
- * E-mail:
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102
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De Vos WH, Hoebe RA, Joss GH, Haffmans W, Baatout S, Van Oostveldt P, Manders EMM. Controlled light exposure microscopy reveals dynamic telomere microterritories throughout the cell cycle. Cytometry A 2009; 75:428-39. [PMID: 19097172 DOI: 10.1002/cyto.a.20699] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Telomeres are complex end structures that confer functional integrity and positional stability to human chromosomes. Despite their critical importance, there is no clear view on telomere organization in cycling human cells and their dynamic behavior throughout the cell cycle. We investigated spatiotemporal organization of telomeres in living human ECV-304 cells stably expressing telomere binding proteins TRF1 and TRF2 fused to mCitrine using four dimensional microscopy. We thereby made use of controlled light exposure microscopy (CLEM), a novel technology that strongly reduces photodamage by limiting excitation in parts of the image where full exposure is not needed. We found that telomeres share small territories where they dynamically associate. These territories are preferentially positioned at the interface of chromatin domains. TRF1 and TRF2 are abundantly present in these territories but not firmly bound. At the onset of mitosis, the bulk of TRF protein dissociates from telomere regions, territories disintegrate and individual telomeres become faintly visible. The combination of stable cell lines, CLEM and cytometry proved essential in providing novel insights in compartment-based nuclear organization and may serve as a model approach for investigating telomere-driven genome-instability and studying long-term nuclear dynamics.
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Affiliation(s)
- Winnok H De Vos
- Department of Molecular Biotechnology, Faculty of Bio-engineering Sciences, Ghent University, Coupure links 653, Ghent 9000, Belgium.
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103
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Abstract
Just over 25 years ago, MYC, the human homologue of a retroviral oncogene, was identified. Since that time, MYC research has been intense and the advances impressive. On reflection, it is astonishing how each incremental insight into MYC regulation and function has also had an impact on numerous biological disciplines, including our understanding of molecular oncogenesis in general. Here we chronicle the major advances in our understanding of MYC biology, and peer into the future of MYC research.
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104
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Knecht H, Sawan B, Lichtensztejn D, Lemieux B, Wellinger RJ, Mai S. The 3D nuclear organization of telomeres marks the transition from Hodgkin to Reed-Sternberg cells. Leukemia 2008; 23:565-73. [PMID: 19039323 DOI: 10.1038/leu.2008.314] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
To get an insight into the transition from mononuclear Hodgkin cells (H cells) to diagnostic multinuclear Reed-Sternberg cells (RS cells), we performed an analysis of the three-dimensional (3D) structure of the telomeres in the nuclei of the Hodgkin cell lines HDLM-2, L-428, L-1236 and lymph node biopsies of patients with Hodgkin's disease. Cellular localization of key proteins of the telomere-localized shelterin complex, the mitotic spindle and double-stranded DNA breaks was also analyzed. RS cells show significantly shorter and significantly fewer telomeres in relation to the total nuclear volume when compared with H cells; in particular, telomere-poor 'ghost' nuclei are often adjacent to one or two nuclei displaying huge telomeric aggregates. Shelterin proteins are mainly cytoplasmic in both H and RS cells, whereas double-stranded DNA breaks accumulate in the nuclei of RS cells. In RS cells, multipolar spindles prevent proper chromosome segregation. In conclusion, a process of nuclear disorganization seems to initiate in H cells and further progresses when the cells turn into RS cells and become end-stage tumor cells, unable to divide further because of telomere loss, shortening and aggregate formation, extensive DNA damage and aberrant mitotic spindles that may no longer sustain chromosome segregation. Our findings allow a mechanistic 3D understanding of the transition of H to RS cells.
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Affiliation(s)
- H Knecht
- Département de Médicine, CHUS, Université de Sherbrooke, Sherbrooke, Québec, Canada.
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105
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Goldberg-Bittman L, Kitay-Cohen Y, Quitt M, Hadary R, Fejgin MD, Yukla M, Amiel A. Telomere aggregates in non-Hodgkin lymphoma patients at different disease stages. ACTA ACUST UNITED AC 2008; 184:105-8. [PMID: 18617059 DOI: 10.1016/j.cancergencyto.2008.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Accepted: 04/07/2008] [Indexed: 10/21/2022]
Abstract
Telomeres of tumor nuclei tend to form aggregates (TA). The same phenomenon was also observed in premalignant states. The aim of this study was to estimate TA formation in leukocytes of patients with non-Hodgkin lymphoma (NHL) at different disease stages (diagnosis, treatment, relapse, and remission). The peptide nucleic acid Telomere Kit was used to evaluate TA formation, using two-dimensional fluorescence microscopy. A higher rate of TA was found in all the NHL stages (including remission) than in the control group. Significantly higher TA formation was also observed in the relapse group, compared to the diagnosis group. It may be possible that patients with higher TA numbers are prone to relapse. From our previous results involving replication pattern, random aneuploidy rate, and (recently) TA formation, it can be concluded that the patients in remission are at higher risk of developing relapse than the normal population throughout their life span. The genetic instability parameters remain in the cells of these patients, who must continue to be monitored throughout their life.
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Affiliation(s)
- L Goldberg-Bittman
- Genetic Institute, Meir Hospital, 59 Tchernichovski St., Kfar-Saba 44281, Israel
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106
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Coletta RD, Christensen KL, Micalizzi DS, Jedlicka P, Varella-Garcia M, Ford HL. Six1 overexpression in mammary cells induces genomic instability and is sufficient for malignant transformation. Cancer Res 2008; 68:2204-13. [PMID: 18381426 DOI: 10.1158/0008-5472.can-07-3141] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Homeoproteins are transcription factors that act as master regulators of development and are frequently dysregulated in cancers. During embryogenesis, the Six1 homeoprotein is essential for the expansion of precursor cell populations that give rise to muscle and kidney, among other organs. Six1 overexpression is observed in numerous cancers, resulting in increased proliferation, survival, and metastasis. Here, we investigate whether Six1 can play a causal role in mammary tumor initiation. We show that Six1 overexpression in MCF12A mammary epithelial cells promotes multiple properties associated with malignant transformation, including increased proliferation, genomic instability, and anchorage-independent growth. We further show that this transformation is dependent on up-regulation of its transcriptional target, cyclin A1, which is normally expressed in the embryonic mammary gland but dramatically reduced in the adult gland. Six1-transformed MCF12A cells are tumorigenic in nude mice, forming aggressive tumors that are locally invasive and exhibit peritumoral lymphovascular invasion. In human breast carcinomas, expression of Six1 and cyclin A1 mRNA correlate strongly with each other (P < 0.0001), and expression of Six1 and cyclin A1 each correlate with Ki67, a marker of proliferation (P < 0.0001 and P = 0.014, respectively). Together, our data indicate that Six1 overexpression is sufficient for malignant transformation of immortalized, nontumorigenic mammary epithelial cells, and suggest that the mechanism of this transformation involves inappropriate reexpression of cyclin A1 in the adult mammary gland.
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Affiliation(s)
- Ricardo D Coletta
- Department of Obstretrics and Gynecology, University of Colorado Health Sciences Center, Aurora, Colorado 80045, USA
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107
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Reddy K. Double minutes (dmin) and homogeneously staining regions (hsr) in myeloid disorders: a new case suggesting that dmin form hsr in vivo. Cytogenet Genome Res 2007; 119:53-9. [DOI: 10.1159/000109619] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2007] [Accepted: 06/04/2007] [Indexed: 12/21/2022] Open
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108
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Guffei A, Lichtensztejn Z, Gonçalves dos Santos Silva A, Louis SF, Caporali A, Mai S. c-Myc-dependent formation of Robertsonian translocation chromosomes in mouse cells. Neoplasia 2007; 9:578-88. [PMID: 17710161 PMCID: PMC1941693 DOI: 10.1593/neo.07355] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Revised: 05/31/2007] [Accepted: 06/01/2007] [Indexed: 12/29/2022] Open
Abstract
Robertsonian (Rb) translocation chromosomes occur in human and murine cancers and involve the aberrant joining of two acrocentric chromosomes in humans and two telocentric chromosomes in mice. Mechanisms leading to their generation remain elusive, but models for their formation have been proposed. They include breakage of centromeric sequences and their subsequent fusions, centric misdivision, misparing between highly repetitive sequences of p-tel or p-arm repeats, and recombinational joining of centromeres and/or centromeric fusions. Here, we have investigated the role of the oncoprotein c-Myc in the formation of Rb chromosomes in mouse cells harboring exclusively telocentric chromosomes. In mouse plasmacytoma cells with constitutive c-Myc deregulation and in immortalized mouse lymphocytes with conditional c-Myc expression, we show that positional remodeling of centromeres in interphase nuclei coincides with the formation of Rb chromosomes. Furthermore, we demonstrate that c-Myc deregulation in a myc box II-dependent manner is sufficient to induce Rb translocation chromosomes. Because telomeric signals are present at all joined centromeres of Rb chromosomes, we conclude that c-Myc mediates Rb chromosome formation in mouse cells by telomere fusions at centromeric termini of telocentric chromosomes. Our findings are relevant to the understanding of nuclear chromosome remodeling during the initiation of genomic instability and tumorigenesis.
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Affiliation(s)
- Amanda Guffei
- Manitoba Institute of Cell Biology, The University of Manitoba, CancerCare Manitoba, Winnipeg, MB, Canada
| | - Zelda Lichtensztejn
- Manitoba Institute of Cell Biology, The University of Manitoba, CancerCare Manitoba, Winnipeg, MB, Canada
| | - Amanda Gonçalves dos Santos Silva
- Manitoba Institute of Cell Biology, The University of Manitoba, CancerCare Manitoba, Winnipeg, MB, Canada
- Disciplina de Imunologia, Departamento de Microbiologia, Imunologia, e Parasitologia, Universidade Federal de São Paulo, São Paulo, SP 04023-062, Brazil
| | - Sherif F Louis
- Manitoba Institute of Cell Biology, The University of Manitoba, CancerCare Manitoba, Winnipeg, MB, Canada
| | - Andrea Caporali
- Manitoba Institute of Cell Biology, The University of Manitoba, CancerCare Manitoba, Winnipeg, MB, Canada
- Dipartimento di Medicina Sperimentale, Sezione di Biochimica, Biochimica Clinica e Biochimica dell'Esercizio Fisico, Università degli Studi di Parma, Parma 43100, Italy
| | - Sabine Mai
- Manitoba Institute of Cell Biology, The University of Manitoba, CancerCare Manitoba, Winnipeg, MB, Canada
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109
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Gorringe KL, Jacobs S, Thompson ER, Sridhar A, Qiu W, Choong DYH, Campbell IG. High-resolution single nucleotide polymorphism array analysis of epithelial ovarian cancer reveals numerous microdeletions and amplifications. Clin Cancer Res 2007; 13:4731-9. [PMID: 17699850 DOI: 10.1158/1078-0432.ccr-07-0502] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Genetic changes in sporadic ovarian cancer are relatively poorly characterized compared with other tumor types. We have evaluated the use of high-resolution whole genome arrays for the genetic profiling of epithelial ovarian cancer. EXPERIMENTAL DESIGN We have evaluated 31 primary ovarian cancers and matched normal DNA for loss of heterozygosity and copy number alterations using 500 K single nucleotide polymorphism arrays. RESULTS In addition to identifying the expected large-scale genomic copy number changes, >380 small regions of copy number gain or loss (<500 kb) were identified among the 31 tumors, including 33 regions of high-level gain (>5 copies) and 27 homozygous deletions. The existence of such a high frequency of small regions exhibiting copy number alterations had not been previously suspected because earlier genomic array platforms lacked comparable resolution. Interestingly, many of these regions harbor known cancer genes. For example, one tumor harbored a 350-kb high-level amplification centered on FGFR1 and three tumors showed regions of homozygous loss 109 to 216 kb in size involving the RB1 tumor suppressor gene only. CONCLUSIONS These data suggest that novel cancer genes may be located within the other identified small regions of copy number alteration. Analysis of the number of copy number breakpoints and the distribution of the small regions of copy number change indicate high levels of structural chromosomal genetic instability in ovarian cancer.
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Affiliation(s)
- Kylie L Gorringe
- Victorian Breast Cancer Research Consortium Cancer Genetics Laboratory, Peter MacCallum Cancer Centre, East Melbourne, Victoria, Australia
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110
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Maclean KH, Kastan MB, Cleveland JL. Atm deficiency affects both apoptosis and proliferation to augment Myc-induced lymphomagenesis. Mol Cancer Res 2007; 5:705-11. [PMID: 17634425 DOI: 10.1158/1541-7786.mcr-07-0058] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Myc oncoproteins are commonly activated in malignancies and are sufficient to provoke many types of cancer. However, the critical mechanisms by which Myc contributes to malignant transformation are not clear. DNA damage seems to be an important initiating event in tumorigenesis. Here, we show that although Myc does not directly induce double-stranded DNA breaks, it does augment activation of the Atm/p53 DNA damage response pathway, suggesting that Atm may function as a guardian against Myc-induced transformation. Indeed, we show that Atm loss augments Myc-induced lymphomagenesis and impairs Myc-induced apoptosis, which normally harnesses Myc-driven tumorigenesis. Surprisingly, Atm loss also augments the proliferative response induced by Myc, and this augmentation is associated with enhanced suppression of the expression of the cyclin-dependent kinase inhibitor p27(Kip1). Therefore, regulation of cell proliferation and p27(Kip1) seems to be a contributing mechanism by which Atm holds tumor formation in check.
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Affiliation(s)
- Kirsteen H Maclean
- Department of Biochemistry, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
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111
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Gao P, Zhang H, Dinavahi R, Li F, Xiang Y, Raman V, Bhujwalla ZM, Felsher DW, Cheng L, Pevsner J, Lee LA, Semenza GL, Dang CV. HIF-dependent antitumorigenic effect of antioxidants in vivo. Cancer Cell 2007; 12:230-8. [PMID: 17785204 PMCID: PMC2084208 DOI: 10.1016/j.ccr.2007.08.004] [Citation(s) in RCA: 399] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Revised: 06/20/2007] [Accepted: 08/02/2007] [Indexed: 01/09/2023]
Abstract
The antitumorigenic activity of antioxidants has been presumed to arise from their ability to squelch DNA damage and genomic instability mediated by reactive oxygen species (ROS). Here, we report that antioxidants inhibited three tumorigenic models in vivo. Inhibition of a MYC-dependent human B lymphoma model was unassociated with genomic instability but was linked to diminished hypoxia-inducible factor (HIF)-1 levels in a prolyl hydroxylase 2 and von Hippel-Lindau protein-dependent manner. Ectopic expression of an oxygen-independent, stabilized HIF-1 mutant rescued lymphoma xenografts from inhibition by two antioxidants: N-acetylcysteine and vitamin C. These findings challenge the paradigm that antioxidants diminish tumorigenesis primarily through decreasing DNA damage and mutations and provide significant support for a key antitumorigenic effect of diminishing HIF levels.
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Affiliation(s)
- Ping Gao
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Huafeng Zhang
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Ramani Dinavahi
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Feng Li
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Yan Xiang
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Venu Raman
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Zaver M. Bhujwalla
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Dean W. Felsher
- Departments of Medicine and Pathology, Stanford University School of Medicine, Stanford, CA 94305
| | - Linzhao Cheng
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Jonathan Pevsner
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Linda A. Lee
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Gregg L. Semenza
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Chi V. Dang
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205
- *Correspondence: Ross Research Building, Room 1032, 720 Rutland Avenue, Baltimore, MD 21205, Tel: 410-955-2411, FAX: 410-955-0185,
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112
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Sarkar R, Guffei A, Vermolen BJ, Garini Y, Mai S. Alterations of centromere positions in nuclei of immortalized and malignant mouse lymphocytes. Cytometry A 2007; 71:386-92. [PMID: 17342774 DOI: 10.1002/cyto.a.20395] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The three-dimensional (3D) positions of centromeres have been studied in several cell systems. However, data on centromere positions during cellular transformation remain elusive. This study has focused on mouse lymphocytes and investigated the centromere positions in primary, immortalized, and tumor cells. METHODS Eighty-to-ninety z-slices of each mouse lymphocyte nucleus were acquired using a sampling distance of 107 nm in the xy plane and 200 nm along z for each z-stack, using an Axioplan 2 microscope, an AxioCam HR CCD, a 63x/1.4 oil objective, and the Axiovision 3.1 software (Carl Zeiss, Canada). A constrained iterative algorithm (Schaefer et al., J Microsc 2001;204:99-107) was used for deconvolution. Centromere positions in 3D images were analyzed using CentroView, a program we developed to measure nuclear centromere positions. RESULTS Using CentroView we determined the positions of centromeres in primary lymphocytes, immortalized and malignant mouse B cells. We show that centromeres exhibit altered nuclear positions in immortalized and malignant B cells. These changes are independent of previously described cell cycle-dependent centromere dynamics. CONCLUSIONS The 3D positions of centromeres are altered during cellular transformation. In lymphocytes, centromeres are found in more central nuclear positions following immortalization and transformation. These nuclear changes reflect structural remodeling of mammalian nuclei during oncogenesis and may impact on the structural organization of chromosomes. How centromeric changes are linked to nuclear remodeling can now be quantitatively examined using the tools of this study.
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Affiliation(s)
- Rahul Sarkar
- Manitoba Institute of Cell Biology, The University of Manitoba, CancerCare Manitoba, Winnipeg, Manitoba, Canada
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113
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Ford RJ, Shen L, Lin-Lee YC, Pham LV, Multani A, Zhou HJ, Tamayo AT, Zhang C, Hawthorn L, Cowell JK, Ambrus JL. Development of a murine model for blastoid variant mantle-cell lymphoma. Blood 2007; 109:4899-906. [PMID: 17311992 PMCID: PMC1885517 DOI: 10.1182/blood-2006-08-038497] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2006] [Accepted: 02/12/2007] [Indexed: 12/20/2022] Open
Abstract
Blastoid-variant mantle-cell lymphoma (MCL-BV), unlike most B-cell non-Hodgkin lymphomas (NHL-Bs), is refractory to conventional chemotherapy and associated with a very poor prognosis. Development of new therapies has been hampered by the lack of valid animal models. We have developed a novel murine model of MCL-BV by crossing interleukin 14alpha (IL-14alpha) transgenic mice with c-Myc transgenic mice (double transgenic [DTG]). IL-14alpha is a B-cell growth factor that is expressed in a number of high-grade lymphomas, including MCL-BV. Ninety-five percent of IL-14alpha transgenic mice develop CD5(+) large B-cell lymphomas by 18 months of age. Sixty percent of c-Myc transgenic mice develop pre-B-cell lymphomas by 12 months of age. Close to 100% of DTG mice develop an aggressive, rapidly fatal lymphoma at 3 to 4 months of age that is CD5(+), CD19(+), CD21(-), CD23(-), sIgM(+). The tumor is found in the blood, bone marrow, liver, spleen, lymph nodes, gastrointestinal tract, and lungs and rarely in the brain, similar to the involvement seen in human MCL-BV. Immunoglobulin gene rearrangements document the monoclonality of the tumor. Cyclin D1 is highly expressed in these tumors, as it is in MCL-BV. DTG represents a novel model for MCL-BV that should reveal important insights into the pathogenesis of the lymphoma and contribute to the development of new forms of therapy.
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Affiliation(s)
- Richard J Ford
- Department of Hematopathology, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
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114
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McCaul JA, Gordon KE, Minty F, Fleming J, Parkinson EK. Telomere dysfunction is related to the intrinsic radio-resistance of human oral cancer cells. Oral Oncol 2007; 44:261-9. [PMID: 17475542 DOI: 10.1016/j.oraloncology.2007.02.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2006] [Revised: 02/23/2007] [Accepted: 02/23/2007] [Indexed: 12/27/2022]
Abstract
Evidence from telomerase-deficient mice strongly suggests that dysfunctional short telomeres affect cellular radio-sensitivity but this idea has yet to be extensively tested in relevant human cancer types such as oral squamous cell carcinomas (OSCCs), which are frequently treated by radiotherapy. The OSCC line BICR7 has low levels of telomerase activity, short telomeres and high levels of telomere dysfunction (judged by a high level of anaphase bridges); whereas the BICR6 line has high levels of telomerase and is more radio-resistant. Ectopic expression of the human TElomerase Reverse Transcriptase (hTERT) reduced telomere dysfunction and increased radio-resistance in BICR7 cells, but not BICR6. Furthermore, the radio-resistance of GM847 cells, which use telomerase-independent mechanisms of telomere maintenance, and of telomerase-negative normal human fibroblasts with long telomeres are similarly unaffected by ectopic expression of telomerase. We tested whether telomere function, as measured by the Anaphase Bridge Index (ABI), was found to be a useful predictor of radio-resistance in a panel of OSCC lines. Using inverse regression analysis, we found a strong inverse relationship between the ABI and radio-resistance (P<0.001), as measured by the Surviving Fraction at 4Gy (SF4). These results suggest that telomerase inhibitors could sensitise a subset of oral SCCs with short telomeres to radiotherapy and for the first time demonstrate that the tumour ABI may assist the selection of cancers that would be suitable for such sensitisation therapy.
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Affiliation(s)
- James A McCaul
- Beatson Institute for Cancer Research, Cancer Research UK Beatson Laboratories, Garscube Estate, Switchback Rd., Bearsden, Glasgow G61 1BD, UK
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115
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Abstract
It was in the 1930s that telomeres (from the Greek telos = end and meros = part) were first recognized as essential structures at the ends of the chromosomes and were shown to be important for chromosomal stability (Muller HJ: The remaking of chromosomes. The Collecting Net-Woods Hole 1938: 13: 181-198, McClintock B, The stability of broken ends of chromosomes in Zea mays. Genetics 1041: 26: 234-282). However, it was only in 1978 that the first telomeric sequence was identified -- in the protocoa Tetrahymena, a single cell organism that at a certain stage of development has many identical minichromosomes with twice as many telomeres (Blackburn EH and Gall JG. A tandemly repeated sequence at the termini of the extrachromosomal ribosomal RNA genes in Tetrahymena. J. Mol. Biol. 1978: 120: 33-53.). Today we know that telomeres form specialized, three-dimensional DNA-protein structures and fulfil important capping functions. Besides, telomeric DNA is essential as ''access DNA'' for those cells that are not able to counteract loss of DNA during replication because they do not express telomerase, the enzyme responsible for telomere length maintenance. Since telomerase is mostly found in tumor cells and inhibition correlates with telomere shortening and finally growth inhibition, telomerase and lately also the telomeres themselves have become attractive targets for anti-cancer therapy. This review aims to critically throw light on different therapeutical approaches and comes to the conclusion that telomeres may be the better targets for cancer therapeutics.
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Affiliation(s)
- Petra Boukamp
- Department of Genetics and Skin Carcinogenesis, German Cancer Research Center, Heidelberg, Germany.
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116
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Bayani J, Selvarajah S, Maire G, Vukovic B, Al-Romaih K, Zielenska M, Squire JA. Genomic mechanisms and measurement of structural and numerical instability in cancer cells. Semin Cancer Biol 2006; 17:5-18. [PMID: 17126026 DOI: 10.1016/j.semcancer.2006.10.006] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2006] [Accepted: 10/17/2006] [Indexed: 12/15/2022]
Abstract
The progression to cancer is often associated with instability and the acquisition of genomic heterogeneity, generating both clonal and non-clonal populations. Chromosomal instability (CIN) describes the excessive rate of numerical and structural genomic change in tumors. Mitotic segregation errors strongly influences copy number, while structural aberrations can occur at unstable genomic regions, or through aberrant DNA repair or methylation. Combined molecular cytogenetic analyses can evaluate cell-to-cell variation, and define the complexity of numerical and structural alterations. Because structural change may occur independently of numerical alteration, we propose the term structural chromosomal instability [(S)-CIN] to distinguish numerical from structural CIN.
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Affiliation(s)
- Jane Bayani
- Division of Applied Molecular Oncology, Princess Margaret Hospital, University Health Network, 610 University Avenue, Room 9-717, Toronto, Ontario, Canada M5G 2M9.
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Kuttler F, Mai S. Formation of non-random extrachromosomal elements during development, differentiation and oncogenesis. Semin Cancer Biol 2006; 17:56-64. [PMID: 17116402 DOI: 10.1016/j.semcancer.2006.10.007] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2006] [Accepted: 10/17/2006] [Indexed: 11/25/2022]
Abstract
Extrachromosomal elements (EEs) were first discovered as minute chromatin bodies [Cox et al. Minute chromatin bodies in malignant tumors of childhood. Lancet 1965;62:55-8], and subsequently characterized as small circular DNA molecules physically separated from chromosomes. They include episomes, minichromosomes, small polydispersed DNAs or double minutes. This review focuses on eukaryotic EEs generated by genome rearrangements under physiological or pathological conditions. Some of those rearrangements occur randomly, but others are strictly non-random, highly regulated, and involve specific chromosomal locations (V(D)J-recombination, telomere maintenance mechanisms, c-myc deregulation). The multiple mechanisms of EEs formation are strongly interconnected and frequently linked to gene amplification. Identification of genes located on EEs will undoubtedly allow a better understanding of genome dynamics and oncogenic pathways.
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Affiliation(s)
- Fabien Kuttler
- Manitoba Institute of Cell Biology, CancerCare Manitoba, University of Manitoba, 675 McDermot Avenue, Winnipeg, Man. R3E 0V9, Canada.
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118
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Raz V, Carlotti F, Vermolen BJ, van der Poel E, Sloos WCR, Knaän-Shanzer S, de Vries AAF, Hoeben RC, Young IT, Tanke HJ, Garini Y, Dirks RW. Changes in lamina structure are followed by spatial reorganization of heterochromatic regions in caspase-8-activated human mesenchymal stem cells. J Cell Sci 2006; 119:4247-56. [PMID: 17003109 DOI: 10.1242/jcs.03180] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Apoptosis is fundamental to the regulation of homeostasis of stem cells in vivo. Whereas the pathways underlying the molecular and biochemical details of nuclear breakdown that accompanies apoptosis have been elucidated, the precise nature of nuclear reorganization that precedes the demolition phase is not fully understood. Here, we expressed an inducible caspase-8 in human mesenchymal stem cells, and quantitatively followed the early changes in nuclear organization during apoptosis. We found that caspase-8 induces alteration of the nuclear lamina and a subsequent spatial reorganization of both centromeres, which are shifted towards a peripheral localization, and telomeres, which form aggregates. This nuclear reorganization correlates with caspase-3 sensitivity of lamina proteins, because the expression of lamin mutant constructs with caspase-3 hypersensitivity resulted in a caspase-8-independent appearance of lamina intranuclear structures and telomere aggregates, whereas application of a caspase inhibitor restrains these changes in nuclear reorganization. Notably, upon activation of apoptosis, we observed no initial changes in the spatial organization of the promyelocytic leukemia nuclear bodies (PML-NBs). We suggest that during activation of the caspase-8 pathway changes in the lamina structure precede changes in heterochromatin spatial organization, and the subsequent breakdown of lamina and PML-NB.
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Affiliation(s)
- Vered Raz
- Department of Molecular Cell Biology, Leiden University Medical Center, Einsteinweg 20, 2300RC Leiden, The Netherlands.
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119
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Ray S, Atkuri KR, Deb-Basu D, Adler AS, Chang HY, Herzenberg LA, Felsher DW. MYC can induce DNA breaks in vivo and in vitro independent of reactive oxygen species. Cancer Res 2006; 66:6598-605. [PMID: 16818632 DOI: 10.1158/0008-5472.can-05-3115] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
MYC overexpression is thought to initiate tumorigenesis by inducing cellular proliferation and growth and to be restrained from causing tumorigenesis by inducing cell cycle arrest, cellular senescence, and/or apoptosis. Here we show that MYC can induce DNA breaks both in vitro and in vivo independent of increased production of reactive oxygen species (ROS). We provide an insight into the specific circumstances under which MYC generates ROS in vitro and propose a possible mechanism. We found that MYC induces DNA double-strand breaks (DSBs) independent of ROS production in murine lymphocytes in vivo as well as in normal human foreskin fibroblasts (NHFs) in vitro in normal (10%) serum, as measured by gammaH2AX staining. However, NHFs cultured in vitro in low serum (0.05%) and/or ambient oxygen saturation resulted in ROS-associated oxidative damage and DNA single-strand breaks (SSBs), as measured by Ape-1 staining. In NHFs cultured in low versus normal serum, MYC induced increased expression of CYP2C9, a gene product well known to be associated with ROS production. Specific inhibition of CYP2C9 by small interfering RNA was shown to partially inhibit MYC-induced ROS production. Hence, MYC overexpression can induce ROS and SSBs under some conditions, but generally induces widespread DSBs in vivo and in vitro independent of ROS production.
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Affiliation(s)
- Suma Ray
- Division of Oncology, Department of Medicine and Pathology, Stanford University School of Medicine, 269 Campus Drive, Stanford, CA 94305, USA
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120
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Caporali A, Wark L, Vermolen BJ, Garini Y, Mai S. Telomeric aggregates and end-to-end chromosomal fusions require myc box II. Oncogene 2006; 26:1398-406. [PMID: 16953226 DOI: 10.1038/sj.onc.1209928] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Telomeres of tumor cells form telomeric aggregates (TAs) within the three-dimensional (3D) interphase nucleus. Some of these TAs represent end-to-end chromosomal fusions and may subsequently initiate breakage-bridge-fusion cycles. Wild-type (wt) and myc box II mutant (mt) Myc induce different types of genomic instability when conditionally expressed in mouse proB cells (Ba/F3). Only wt Myc overexpressing Ba/F3 cells are capable of tumor formation in severe combined immunodeficient mice. In this study, we investigated whether telomere dysfunction leading to TA formation is linked to the genetic changes that permit wt c-Myc-dependent transformation of Ba/F3 cells. To this end, we examined the 3D organization of telomeres after the deregulated expression of deletion myc boxII mutant (Delta106) or wt Myc. Delta106-Myc overexpression did not induce TAs, whereas wt-Myc deregulation did. Instead, Delta106-Myc remodelled the 3D telomeric organization such that telomeres aligned in the center of the 3D interphase nucleus forming a telomeric disk owing to a Delta106-induced G1/S cell cycle arrest. In contrast, wt-Myc overexpression led to distorted telomere distribution and TA formation. Analysis of chromosomal alterations using spectral karyotyping confirmed Delta106-Myc and wt-Myc-associated genomic instability. A significant number of chromosomal end-to-end fusions indicative of telomere dysfunction were noted in wt-Myc-expressing cells only. This study suggests that TAs may play a fundamental role in Myc-induced tumorigenesis and provides a novel way to dissect tumor initiation.
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Affiliation(s)
- A Caporali
- Dipartimento di Medicina Sperimentale, Sezione di Biochimica, Biochimica Clinica e Biochimica dell'Esercizio Fisico, Università degli Studi di Parma, Parma, Italy
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121
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Arvanitis C, Felsher DW. Conditional transgenic models define how MYC initiates and maintains tumorigenesis. Semin Cancer Biol 2006; 16:313-7. [PMID: 16935001 DOI: 10.1016/j.semcancer.2006.07.012] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
MYC is one of the most commonly overexpressed oncogenes in human cancer. The targeted inactivation of MYC is a possible therapy for neoplasia. Conditional transgenic mouse model systems are tractable methods to precisely dissect how and when the inactivation of MYC might be effective in the treatment for human cancer. From these model systems, several general principles emerge. MYC inactivation stereotypically results in the proliferative arrest, differentiation and/or apoptosis of tumor cells. The specific consequences of MYC inactivation appear to depend both on the type of cancer as well as the constellation of genetic events unique to a given tumor. Tumors can escape from dependence upon MYC by acquiring compensatory genetic events. MYC inactivation can uncover the stem cell properties of tumor cells that differentiate into normal appearing cells. In some cases, these differentiated cells are actually dormant tumor cells that recover their neoplastic properties upon MYC reactivation. In other cases, even brief MYC inactivation is sufficient to induce sustained tumor regression. Insights from conditional transgenic mouse models will be useful in the development of therapies that target MYC for the treatment of cancer.
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Affiliation(s)
- Constadina Arvanitis
- Department of Molecular Pharmacology, Stanford University School of Medicine, Stanford, CA 94305, USA
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122
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Mai S, Garini Y. The significance of telomeric aggregates in the interphase nuclei of tumor cells. J Cell Biochem 2006; 97:904-15. [PMID: 16408280 DOI: 10.1002/jcb.20760] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Telomeres are TTAGGG repetitive motifs found at the ends of vertebrate chromosomes. In humans, telomeres are protected by shelterin, a complex of six proteins (de Lange [2005] Genes Dev. 19: 2100-2110). Since (Müller [1938] Collecting Net. 13: 181-198; McClintock [1941] Genetics 26: 234-282), their function in maintaining chromosome stability has been intensively studied. This interest, especially in cancer biology, stems from the fact that telomere dysfunction is linked to genomic instability and tumorigenesis (Gisselsson et al. [2001] Proc. Natl. Acad. Sci. USA 98: 12683-12688; Deng et al. [2003] Genes Chromosomes Cancer 37: 92-97; DePinho and Polyak [2004] Nat. Genetics 36: 932-934; Meeker et al. [2004] Clin. Cancer Res. 10: 3317-3326). In the present overview, we will discuss the role of telomeres in genome stability, recent findings on three-dimensional (3D) changes of telomeres in tumor interphase nuclei, and outline future avenues of research.
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MESH Headings
- Animals
- Apoptosis
- Cell Nucleus/chemistry
- Cell Nucleus/genetics
- Chromosome Aberrations
- Chromosomes, Human
- Chromosomes, Human, Pair 10
- Chromosomes, Human, Pair 13
- Chromosomes, Human, Pair 17
- Chromosomes, Human, Pair 5
- Chromosomes, Human, Pair 7
- Evolution, Molecular
- Genome
- Humans
- Interphase/genetics
- Mice
- Neoplasms/genetics
- Neoplasms/metabolism
- Telomere/chemistry
- Telomere/genetics
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Affiliation(s)
- Sabine Mai
- Manitoba Institute of Cell Biology, CancerCare Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 0V9.
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