51
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Horn S, Figl A, Rachakonda PS, Fischer C, Sucker A, Gast A, Kadel S, Moll I, Nagore E, Hemminki K, Schadendorf D, Kumar R. TERT promoter mutations in familial and sporadic melanoma. Science 2013; 339:959-61. [PMID: 23348503 DOI: 10.1126/science.1230062] [Citation(s) in RCA: 1329] [Impact Index Per Article: 120.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Cutaneous melanoma occurs in both familial and sporadic forms. We investigated a melanoma-prone family through linkage analysis and high-throughput sequencing and identified a disease-segregating germline mutation in the promoter of the telomerase reverse transcriptase (TERT) gene, which encodes the catalytic subunit of telomerase. The mutation creates a new binding motif for Ets transcription factors and ternary complex factors (TCFs) near the transcription start and, in reporter gene assays, caused up to twofold increase in transcription. We then screened the TERT promoter in sporadic melanoma and observed recurrent ultraviolet signature somatic mutations in 125 of 168 (74%) of human cell lines derived from metastatic melanomas, 45 of 53 corresponding metastatic tumor tissues (85%), and 25 of 77 (33%) primary melanomas. The majority of those mutations occurred at two positions in the TERT promoter and also generated binding motifs for Ets/TCF transcription factors.
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Affiliation(s)
- Susanne Horn
- Division of Molecular Genetic Epidemiology, German Cancer Research Center, Im Neuenheimer Feld 580, 69120 Heidelberg, Germany
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52
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Chan WL, Chang YS, Yang WK, Huang HD, Chang JG. Very long non-coding RNA and human disease. Biomedicine (Taipei) 2012. [DOI: 10.1016/j.biomed.2012.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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53
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The WSTF-ISWI chromatin remodeling complex transiently associates with the human inactive X chromosome during late S-phase prior to BRCA1 and γ-H2AX. PLoS One 2012; 7:e50023. [PMID: 23166813 PMCID: PMC3498190 DOI: 10.1371/journal.pone.0050023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 10/16/2012] [Indexed: 01/08/2023] Open
Abstract
Replicating the genome prior to each somatic cell division not only requires precise duplication of the genetic information, but also accurately reestablishing the epigenetic signatures that instruct how the genetic material is to be interpreted in the daughter cells. The mammalian inactive X chromosome (Xi), which is faithfully inherited in a silent state in each daughter cell, provides an excellent model of epigenetic regulation. While much is known about the early stages of X chromosome inactivation, much less is understood with regards to retaining the Xi chromatin through somatic cell division. Here we report that the WSTF-ISWI chromatin remodeling complex (WICH) associates with the Xi during late S-phase as the Xi DNA is replicated. Elevated levels of WICH at the Xi is restricted to late S-phase and appears before BRCA1 and γ-H2A.X. The sequential appearance of WICH and BRCA1/γ-H2A.X implicate each as performing important but distinct roles in the maturation and maintenance of heterochromatin at the Xi.
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54
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Abstract
The discovery of numerous noncoding RNA (ncRNA) transcripts in species from yeast to mammals has dramatically altered our understanding of cell biology, especially the biology of diseases such as cancer. In humans, the identification of abundant long ncRNA (lncRNA) >200 bp has catalyzed their characterization as critical components of cancer biology. Recently, roles for lncRNAs as drivers of tumor suppressive and oncogenic functions have appeared in prevalent cancer types, such as breast and prostate cancer. In this review, we highlight the emerging impact of ncRNAs in cancer research, with a particular focus on the mechanisms and functions of lncRNAs.
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Affiliation(s)
- John R Prensner
- Michigan Center for Translational Pathology, Department of Pathology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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55
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Henderson BR. The BRCA1 Breast Cancer Suppressor: Regulation of Transport, Dynamics, and Function at Multiple Subcellular Locations. SCIENTIFICA 2012; 2012:796808. [PMID: 24278741 PMCID: PMC3820561 DOI: 10.6064/2012/796808] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2012] [Accepted: 09/18/2012] [Indexed: 06/02/2023]
Abstract
Inherited mutations in the BRCA1 gene predispose to a higher risk of breast/ovarian cancer. The BRCA1 tumor suppressor is a 1863 amino acid protein with multiple protein interaction domains that facilitate its roles in regulating DNA repair and maintenance, cell cycle progression, transcription, and cell survival/apoptosis. BRCA1 was first identified as a nuclear phosphoprotein, but has since been shown to contain different transport sequences including nuclear export and nuclear localization signals that enable it to shuttle between specific sites within the nucleus and cytoplasm, including DNA repair foci, centrosomes, and mitochondria. BRCA1 nuclear transport and ubiquitin E3 ligase enzymatic activity are tightly regulated by the BRCA1 dimeric binding partner BARD1 and further modulated by cancer mutations and diverse signaling pathways. This paper will focus on the transport, dynamics, and multiple intracellular destinations of BRCA1 with emphasis on how regulation of these events has impact on, and determines, a broad range of important cellular functions.
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Affiliation(s)
- Beric R. Henderson
- Westmead Institute for Cancer Research, Westmead Millennium Institute at Westmead Hospital, University of Sydney, Darcy Road, P.O. Box 412, Westmead, NSW 2145, Australia
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56
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Zhang F, Bick G, Park JY, Andreassen PR. MDC1 and RNF8 function in a pathway that directs BRCA1-dependent localization of PALB2 required for homologous recombination. J Cell Sci 2012; 125:6049-57. [PMID: 23038782 DOI: 10.1242/jcs.111872] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The PALB2 protein is associated with breast cancer susceptibility and Fanconi anemia. Notably, PALB2 is also required for DNA repair by homologous recombination (HR). However, the mechanisms that regulate PALB2, and the functional significance of its interaction with the BRCA1 breast cancer susceptibility protein, are poorly understood. Here, to better understand these processes, we fused PALB2, or the PALB2(L21P) mutant which cannot bind to BRCA1, with the BRCT repeats that are present in, and which localize, BRCA1. Our results yield important insights into the regulation of PALB2 function. Both fusion proteins can bypass BRCA1 to localize to sites of DNA damage. Further, the localized fusion proteins are functional, as determined by their ability to support the assembly of RAD51 foci, even in the absence of the capacity of PALB2 to bind BRCA1. Strikingly, the localized fusion proteins mediate DNA double-strand break (DSB)-initiated HR and resistance to mitomycin C in PALB2-deficient cells. Additionally, we show that the BRCA1-PALB2 heterodimer, rather than the PALB2-PALB2 homodimer, mediates these responses. Importantly, we offer the first insight into how BRCA1-dependent recruitment of PALB2 is integrated with other DNA damage signaling pathways. We find that PALB2 localization depends on the presence of MDC1, RNF8, RAP80 and Abraxas upstream of BRCA1. Thus, PALB2 may link HR to a key ubiquitin-related signaling pathway that responds to DSBs.
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Affiliation(s)
- Fan Zhang
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Research Foundation, Cincinnati, OH 45229, USA
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57
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The secret life of Bcl-2: Apoptosis-independent inhibition of DNA repair by Bcl-2 family members. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2012; 751:247-257. [DOI: 10.1016/j.mrrev.2012.05.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 05/25/2012] [Accepted: 05/26/2012] [Indexed: 11/22/2022]
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58
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Ohhata T, Wutz A. Reactivation of the inactive X chromosome in development and reprogramming. Cell Mol Life Sci 2012; 70:2443-61. [PMID: 23052214 PMCID: PMC3689915 DOI: 10.1007/s00018-012-1174-3] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Revised: 08/26/2012] [Accepted: 09/17/2012] [Indexed: 01/01/2023]
Abstract
In mammals, one of the two X chromosomes of female cells is inactivated for dosage compensation between the sexes. X chromosome inactivation is initiated in early embryos by the noncoding Xist RNA. Subsequent chromatin modifications on the inactive X chromosome (Xi) lead to a remarkable stability of gene repression in somatic cell lineages. In mice, reactivation of genes on the Xi accompanies the establishment of pluripotent cells of the female blastocyst and the development of primordial germ cells. Xi reactivation also occurs when pluripotency is established during the reprogramming of somatic cells to induced pluripotent stem cells. The mechanism of Xi reactivation has attracted increasing interest for studying changes in epigenetic patterns and for improving methods of cell reprogramming. Here, we review recent advances in the understanding of Xi reactivation during development and reprogramming and illustrate potential clinical applications.
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Affiliation(s)
- Tatsuya Ohhata
- Wellcome Trust and MRC Stem Cell Institute, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR UK
- Present Address: Department of Molecular Biology, Hamamatsu University School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192 Japan
| | - Anton Wutz
- Wellcome Trust and MRC Stem Cell Institute, Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QR UK
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59
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Nakada S, Yonamine RM, Matsuo K. RNF8 regulates assembly of RAD51 at DNA double-strand breaks in the absence of BRCA1 and 53BP1. Cancer Res 2012; 72:4974-83. [PMID: 22865450 DOI: 10.1158/0008-5472.can-12-1057] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The tumor suppressor protein BRCA1 localizes to sites of DNA double-strand breaks (DSB), promoting repair by homologous recombination through the recruitment of DNA damage repair proteins. In normal cells, homologous recombination largely depends on BRCA1. However, assembly of the pivotal homologous recombination regulator RAD51 can occur independently of BRCA1 in the absence of 53BP1, another DNA damage response protein. How this assembly process proceeds is unclear, but important to understand in tumor cell settings where BRCA1 is disabled. Here we report that RNF8 regulates BRCA1-independent homologous recombination in 53BP1-depleted cells. RNF8 depletion suppressed the recruitment of RAD51 to DSB sites without affecting assembly or phosphorylation of the replication protein RPA in neocarzinostatin-treated or X-ray-irradiated BRCA1/53BP1-depleted cells. Furthermore, RNF8/BRCA1/53BP1-depleted cells exhibited less efficient homologous recombination than BRCA1/53BP1-depleted cells. Intriguingly, neither RNF8 nor its relative RNF168 were required for RAD51 assembly at DSB sites in 53BP1-expressing cells. Moreover, RNF8-independent RAD51 assembly was found to be regulated by BRCA1. Together, our findings indicate a tripartite regulation of homologous recombination by RNF8, BRCA1, and 53BP1. In addition, our results predict that RNF8 inhibition may be a useful treatment of BRCA1-mutated/53BP1(low) cancers, which are considered resistant to treatment by PARP1 inhibitors and of marked current clinical interest.
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Affiliation(s)
- Shinichiro Nakada
- Department of Bioregulation and Cellular Response, Graduate School of Medicine, Osaka University, Osaka, Japan.
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60
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Abstract
UNLABELLED The p220 BRCA1 tumor suppressor protein has been implicated in multiple biochemical and biologic functions since its molecular cloning 18 years ago. Here, we discuss those functions most relevant for its tumor-suppressing activities with an emphasis on new findings. In particular, this review focuses on what is known of the activities of those BRCA1-binding partners that have tumor suppressor functions, on the reversion of mutant BRCA1 alleles concomitant with therapy resistance, on insights gained from studies of BRCA1 structure-function relationships, recent findings from animal models, and the potential role of BRCA1 in some nonhereditary tumors. From this information, a more detailed and refined picture of BRCA1 tumor suppression is beginning to emerge. Although key mysteries remain--such as why BRCA1 tumor suppression is focused on carcinomas of the breast and ovary--the pace of discovery is increasing. SIGNIFICANCE BRCA1 functions as a clinically important classical tumor suppressor in hereditary breast and ovarian cancer; here, we review progress in understanding how BRCA1 operates to suppress tumor formation.
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Affiliation(s)
- Daniel P Silver
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts, USA
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61
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Heterochromatin instability in cancer: from the Barr body to satellites and the nuclear periphery. Semin Cancer Biol 2012; 23:99-108. [PMID: 22722067 DOI: 10.1016/j.semcancer.2012.06.008] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 05/25/2012] [Accepted: 06/11/2012] [Indexed: 12/31/2022]
Abstract
In recent years it has been recognized that the development of cancer involves a series of not only genetic but epigenetic changes across the genome. At the same time, connections between epigenetic regulation, chromatin packaging, and overall nuclear architecture are increasingly appreciated. The cell-type specific organization of heterochromatin, established upon cell differentiation, is responsible for maintaining much of the genome in a repressed state, within a highly compartmentalized nucleus. This review focuses on recent evidence that in cancer the normal packaging and higher organization of heterochromatin is often compromised. Gross changes in nuclear morphology have long been a criterion for pathologic diagnosis of many cancers, but the specific nuclear components impacted, the mechanisms involved, and the implications for cancer progression have barely begun to emerge. We discuss recent findings regarding distinct heterochromatin types, including the inactive X chromosome, constitutive heterochromatin of peri/centric satellites, and the peripheral heterochromatic compartment (PHC). A theme developed here is that the higher-order organization of satellites and the peripheral heterochromatic compartment may be tightly linked, and that compromise of this organization may promote broad epigenomic imbalance in cancer. Recent studies into the potential role(s) of the breast cancer tumor suppressor, BRCA1, in maintaining heterochromatin will be highlighted. Many questions remain about this new area of cancer epigenetics, which is likely more important in cancer development and progression than widely appreciated. We propose that broad, stochastic compromise in heterochromatin maintenance would create a diversity of expression profiles, and thus a rich opportunity for one or more cells to emerge with a selective growth advantage and potential for neoplasia.
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62
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Evolutionary origin of chromatin remodeling for dosage compensation: Lessons from epigenetic modifications of X chromosomes in germ cells of Drosophila, C.elegans and Mammals. THE NUCLEUS 2012. [DOI: 10.1007/s13237-012-0054-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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63
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Abstract
Cancer cells silence autosomal tumor suppressor genes by Knudson's two-hit mechanism in which loss-of-function mutations and then loss of heterozygosity occur at the tumor suppressor gene loci. However, the identification of X-linked tumor suppressor genes has challenged the traditional theory of 'two-hit inactivation' in tumor suppressor genes, introducing the novel concept that a single genetic hit can cause loss of tumor suppressor function. The mechanism through which these genes are silenced in human cancer is unclear, but elucidating the details will greatly enhance our understanding of the pathogenesis of human cancer. Here, we review the identification of X-linked tumor suppressor genes and discuss the potential mechanisms of their inactivation. In addition, we also discuss how the identification of X-linked tumor suppressor genes can potentially lead to new approaches in cancer therapy.
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Affiliation(s)
- Runhua Liu
- Division of Immunotherapy, Department of Surgery, University of Michigan School of Medicine, Ann Arbor, MI, USA
- Department of Genetics, School of Medicine, University of Alabama at Birmingham and Comprehensive Cancer Center, Birmingham, AL, USA
| | - Mandy Kain
- Division of Immunotherapy, Department of Surgery, University of Michigan School of Medicine, Ann Arbor, MI, USA
| | - Lizhong Wang
- Division of Immunotherapy, Department of Surgery, University of Michigan School of Medicine, Ann Arbor, MI, USA
- Department of Genetics, School of Medicine, University of Alabama at Birmingham and Comprehensive Cancer Center, Birmingham, AL, USA
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64
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Rottenberg S, Vollebergh MA, de Hoon B, de Ronde J, Schouten PC, Kersbergen A, Zander SAL, Pajic M, Jaspers JE, Jonkers M, Lodén M, Sol W, van der Burg E, Wesseling J, Gillet JP, Gottesman MM, Gribnau J, Wessels L, Linn SC, Jonkers J, Borst P. Impact of intertumoral heterogeneity on predicting chemotherapy response of BRCA1-deficient mammary tumors. Cancer Res 2012; 72:2350-61. [PMID: 22396490 DOI: 10.1158/0008-5472.can-11-4201] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The lack of markers to predict chemotherapy responses in patients poses a major handicap in cancer treatment. We searched for gene expression patterns that correlate with docetaxel or cisplatin response in a mouse model for breast cancer associated with BRCA1 deficiency. Array-based expression profiling did not identify a single marker gene predicting docetaxel response, despite an increase in Abcb1 (P-glycoprotein) expression that was sufficient to explain resistance in several poor responders. Intertumoral heterogeneity explained the inability to identify a predictive gene expression signature for docetaxel. To address this problem, we used a novel algorithm designed to detect differential gene expression in a subgroup of the poor responders that could identify tumors with increased Abcb1 transcript levels. In contrast, standard analytical tools, such as significance analysis of microarrays, detected a marker only if it correlated with response in a substantial fraction of tumors. For example, low expression of the Xist gene correlated with cisplatin hypersensitivity in most tumors, and it also predicted long recurrence-free survival of HER2-negative, stage III breast cancer patients treated with intensive platinum-based chemotherapy. Our findings may prove useful for selecting patients with high-risk breast cancer who could benefit from platinum-based therapy.
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Affiliation(s)
- Sven Rottenberg
- Division of Molecular Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
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65
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Abstract
Tiling array and novel sequencing technologies have made available the transcription profile of the entire human genome. However, the extent of transcription and the function of genetic elements that occur outside of protein-coding genes, particularly those involved in disease, are still a matter of debate. In this review, we focus on long non-coding RNAs (lncRNAs) that are involved in cancer. We define lncRNAs and present a cancer-oriented list of lncRNAs, list some tools (for example, public databases) that classify lncRNAs or that scan genome spans of interest to find whether known lncRNAs reside there, and describe some of the functions of lncRNAs and the possible genetic mechanisms that underlie lncRNA expression changes in cancer, as well as current and potential future applications of lncRNA research in the treatment of cancer.
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66
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Hysolli E, Jung YW, Tanaka Y, Kim KY, Park IH. The lesser known story of X chromosome reactivation: a closer look into the reprogramming of the inactive X chromosome. Cell Cycle 2012; 11:229-35. [PMID: 22234239 DOI: 10.4161/cc.11.2.18998] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
X-chromosome inactivation (XCI) is an important mechanism employed by mammalian XX female cells to level X-linked gene expression with that of male XY cells. XCI occurs early in development as the pluripotent cells of the inner cell mass (ICM) in blastocysts successively differentiate into cells of all three germ layers. X-chromosome reactivation (XCR), the reversal of XCI, is critical for germ cell formation as a mechanism to diversify the X-chromosome gene pool. Here we review the characterization of XCR, and further explore its natural occurrence during development and the in vitro models of cellular reprogramming. We also review the key regulators involved in XCI for their role in suppressing the active histone marks and the genes in the active chromosome for their inhibition of X inactivation signals.
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Affiliation(s)
- Eriona Hysolli
- Department of Genetics, Yale Stem Cell Center, Yale School of Medicine, New Haven, CT, USA
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67
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Ellatif SKA, Gutschner T, Diederichs S. Long Noncoding RNA Function and Expression in Cancer. REGULATORY RNAS 2012:197-226. [DOI: 10.1007/978-3-642-22517-8_8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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68
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Ellatif SKA, Gutschner T, Diederichs S. Long Noncoding RNA Function and Expression in Cancer. REGULATORY RNAS 2012:197-226. [DOI: 10.1007/978-3-662-45801-3_8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
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69
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Vollebergh MA, Jonkers J, Linn SC. Genomic instability in breast and ovarian cancers: translation into clinical predictive biomarkers. Cell Mol Life Sci 2012; 69:223-45. [PMID: 21922196 PMCID: PMC11114988 DOI: 10.1007/s00018-011-0809-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 08/18/2011] [Accepted: 08/22/2011] [Indexed: 12/20/2022]
Abstract
Breast and ovarian cancer are among the most common malignancies diagnosed in women worldwide. Together, they account for the majority of cancer-related deaths in women. These cancer types share a number of features, including their association with hereditary cancer syndromes caused by heterozygous germline mutations in BRCA1 or BRCA2. BRCA-associated breast and ovarian cancers are hallmarked by genomic instability and high sensitivity to DNA double-strand break (DSB) inducing agents due to loss of error-free DSB repair via homologous recombination (HR). Recently, poly(ADP-ribose) polymerase inhibitors, a new class of drugs that selectively target HR-deficient tumor cells, have been shown to be highly active in BRCA-associated breast and ovarian cancers. This finding has renewed interest in hallmarks of HR deficiency and the use of other DSB-inducing agents, such as platinum salts or bifunctional alkylators, in breast and ovarian cancer patients. In this review we discuss the similarities between breast and ovarian cancer, the hallmarks of genomic instability in BRCA-mutated and BRCA-like breast and ovarian cancers, and the efforts to search for predictive markers of HR deficiency in order to individualize therapy in breast and ovarian cancer.
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Affiliation(s)
- Marieke A. Vollebergh
- Division of Molecular Biology, Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
- Division of Medical Oncology, Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands
| | - Jos Jonkers
- Division of Molecular Biology, Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
| | - Sabine C. Linn
- Division of Molecular Biology, Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
- Division of Medical Oncology, Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands
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70
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Abstract
BACKGROUND X inactive-specific transcript (XIST) RNA is involved in X chromosome silencing in female cells and allows X chromosome equilibration with males. X inactive-specific transcript expression has been found to be dysregulated in a variety of human cancers when compared to normal cells; meanwhile, the inactivated X chromosome has been noted to be conspicuously absent in human cancer specimens, whereas X chromosome duplications are widely noted. The specific pathways whereby changes in X chromosome status and XIST expression occur in cancer remain incompletely described. Nevertheless, a role for XIST in BRCA1-mediated epigenetic activity has been proposed. METHODS Here we review the data regarding XIST expression and X chromosome status in a variety of female, male, and non-sex-related human cancers. CONCLUSIONS It is not yet known whether X chromosome duplication, XIST dysregulation, and over-expression of X-linked genes represent important factors in tumorgenesis or are simply a consequence of overall epigenetic instability in these cancers.
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71
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BRACking news on triple-negative/basal-like breast cancers: how BRCA1 deficiency may result in the development of a selective tumor subtype. Cancer Metastasis Rev 2011; 31:131-42. [DOI: 10.1007/s10555-011-9336-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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72
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De La Fuente R, Baumann C, Viveiros MM. Role of ATRX in chromatin structure and function: implications for chromosome instability and human disease. Reproduction 2011; 142:221-34. [PMID: 21653732 PMCID: PMC3253860 DOI: 10.1530/rep-10-0380] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Functional differentiation of chromatin structure is essential for the control of gene expression, nuclear architecture, and chromosome stability. Compelling evidence indicates that alterations in chromatin remodeling proteins play an important role in the pathogenesis of human disease. Among these, α-thalassemia mental retardation X-linked protein (ATRX) has recently emerged as a critical factor involved in heterochromatin formation at mammalian centromeres and telomeres as well as facultative heterochromatin on the murine inactive X chromosome. Mutations in human ATRX result in an X-linked neurodevelopmental condition with various degrees of gonadal dysgenesis (ATRX syndrome). Patients with ATRX syndrome may exhibit skewed X chromosome inactivation (XCI) patterns, and ATRX-deficient mice exhibit abnormal imprinted XCI in the trophoblast cell line. Non-random or skewed XCI can potentially affect both the onset and severity of X-linked disease. Notably, failure to establish epigenetic modifications associated with the inactive X chromosome (Xi) results in several conditions that exhibit genomic and chromosome instability such as fragile X syndrome as well as cancer development. Insight into the molecular mechanisms of ATRX function and its interacting partners in different tissues will no doubt contribute to our understanding of the pathogenesis of ATRX syndrome as well as the epigenetic origins of aneuploidy. In turn, this knowledge will be essential for the identification of novel drug targets and diagnostic tools for cancer progression as well as the therapeutic management of global epigenetic changes commonly associated with malignant neoplastic transformation.
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Affiliation(s)
- Rabindranath De La Fuente
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, Georgia 30602, USA.
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73
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Nagel JHA, Peeters JK, Smid M, Sieuwerts AM, Wasielewski M, de Weerd V, Trapman-Jansen AMAC, van den Ouweland A, Brüggenwirth H, van IJcken WFJ, Klijn JGM, van der Spek PJ, Foekens JA, Martens JWM, Schutte M, Meijers-Heijboer H. Gene expression profiling assigns CHEK2 1100delC breast cancers to the luminal intrinsic subtypes. Breast Cancer Res Treat 2011; 132:439-48. [DOI: 10.1007/s10549-011-1588-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 05/11/2011] [Indexed: 12/24/2022]
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74
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Hu Y, Scully R, Sobhian B, Xie A, Shestakova E, Livingston DM. RAP80-directed tuning of BRCA1 homologous recombination function at ionizing radiation-induced nuclear foci. Genes Dev 2011; 25:685-700. [PMID: 21406551 PMCID: PMC3070932 DOI: 10.1101/gad.2011011] [Citation(s) in RCA: 187] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Accepted: 02/07/2011] [Indexed: 01/12/2023]
Abstract
In response to DNA double-strand breaks (DSBs), BRCA1 forms biochemically distinct complexes with certain other DNA damage response proteins. These structures, some of which are required for homologous recombination (HR)-type DSB repair, concentrate at distinct nuclear foci that demarcate sites of genome breakage. Polyubiquitin binding by one of these structures, the RAP80/BRCA1 complex, is required for efficient BRCA1 focal recruitment, but the relationship of this process to the execution of HR has been unclear. We found that this complex actively suppresses otherwise exaggerated, BRCA1-driven HR. By controlling the kinetics by which other BRCA1-interacting proteins that promote HR concentrate together with BRCA1 in nuclear foci, RAP80/BRCA1 complexes suppress excessive DSB end processing, HR-type DSB repair, and overt chromosomal instability. Since chromosomal instability emerges when BRCA1 HR function is either unbridled or absent, active tuning of BRCA1 activity, executed in nuclear foci, is important to genome integrity maintenance.
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Affiliation(s)
- Yiduo Hu
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
| | - Ralph Scully
- Department of Medicine, Harvard Medical School, Boston Massachusetts 02215, USA
- Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA
| | - Bijan Sobhian
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
| | - Anyong Xie
- Department of Medicine, Harvard Medical School, Boston Massachusetts 02215, USA
- Beth Israel Deaconess Medical Center, Boston, Massachusetts 02215, USA
| | - Elena Shestakova
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
| | - David M. Livingston
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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75
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Michalak EM, Jonkers J. Studying therapy response and resistance in mouse models for BRCA1-deficient breast cancer. J Mammary Gland Biol Neoplasia 2011; 16:41-50. [PMID: 21331759 DOI: 10.1007/s10911-011-9199-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Accepted: 02/08/2011] [Indexed: 01/09/2023] Open
Abstract
Worldwide, more than one million women are diagnosed with breast cancer every year, making it the most common malignancy of females in the developed world. Germline mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 account for 4-6% of all breast cancer cases, and mutation carriers have a lifetime risk of 80% for developing breast cancer and 40% for developing ovarian cancer. Current treatment options are limited and often do not lead to cure. In the 17 years since the discovery of BRCA1, the generation of mouse models for BRCA1 deficiency has greatly aided our understanding of it's role in tumorigenesis. In contrast to human BRCA1 mutation carriers, mice carrying heterozygous mutations in Brca1 did not develop spontaneous tumors. This led to the generation of conditional mouse models in which tissue-specific Brca1 deletion induces formation of mammary tumors that closely resemble human BRCA1-mutated breast tumors. These models have proven useful for studying BRCA1-related tumor development, drug response and resistance. BRCA1-deficient cancer cells are defective in DNA repair mediated by homologous recombination (HR) and therefore highly sensitive to DNA-damaging agents such as platinum drugs and poly(ADP-ribose) polymerase (PARP) inhibitors. However, BRCA1-mutated tumors can develop resistance to these drugs; hence improved treatment strategies are critical. Existing mouse models have already proven useful for preclinical testing of (combinations of) therapeutic agents that may be beneficial for the treatment of patients with BRCA1-mutated tumors. In this review, we discuss the progress made towards modeling BRCA1-deficient breast cancer in mice and what we have learned from preclinical studies using these models.
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76
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Hall LL, Lawrence JB. XIST RNA and architecture of the inactive X chromosome: implications for the repeat genome. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2011; 75:345-56. [PMID: 21447818 DOI: 10.1101/sqb.2010.75.030] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
XIST RNA paints and induces silencing of one X chromosome in mammalian female cells, providing a powerful model to investigate long-range chromosomal regulation. This chapter focuses on events downstream from the spread of XIST RNA across the interphase chromosome, to consider how this large noncoding RNA interacts with and silences a whole chromosome. Several lines of evidence are summarized that point to the involvement of repeat sequences in different aspects of the X-inactivation process. Although the "repeat genome" comprises close to half of the human genome, the potential for abundant repeats to contribute to genome regulation has been largely overlooked and may be underestimated. X inactivation has the potential to reveal roles of interspersed and other repeats in the genome. For example, evidence indicates that XIST RNA acts at the architectural level of the whole chromosome to induce formation of a silent core enriched for nongenic and repetitive (Cot-1) DNA, which corresponds to the DAPI-dense Barr body. Expression of repeat RNAs may contribute to chromosome remodeling, and evidence suggests that other types of repeat elements may be involved in escape from X inactivation. Despite great progress in decoding the rest of the genome, we suggest that the repeat genome may contain meaningful but complex language that remains to be better studied and understood.
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Affiliation(s)
- L L Hall
- Department of Cell Biology, University of Massachusetts Medical School, North Worcester, Massachusetts 01655, USA
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77
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Laulier C, Barascu A, Guirouilh-Barbat J, Pennarun G, Le Chalony C, Chevalier F, Palierne G, Bertrand P, Verbavatz JM, Lopez BS. Bcl-2 Inhibits Nuclear Homologous Recombination by Localizing BRCA1 to the Endomembranes. Cancer Res 2011; 71:3590-602. [DOI: 10.1158/0008-5472.can-10-3119] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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78
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Toft DJ, Cryns VL. Minireview: Basal-like breast cancer: from molecular profiles to targeted therapies. Mol Endocrinol 2011; 25:199-211. [PMID: 20861225 PMCID: PMC3035993 DOI: 10.1210/me.2010-0164] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 08/05/2010] [Indexed: 12/11/2022] Open
Abstract
The classification of breast cancer into molecular subtypes with distinctive gene expression signatures that predict treatment response and prognosis has ushered in a new era of personalized medicine for this remarkably heterogeneous and deadly disease. Basal-like breast cancer (BLBC) is a particularly aggressive molecular subtype defined by a robust cluster of genes expressed by epithelial cells in the basal or outer layer of the adult mammary gland. BLBC is a major clinical challenge because these tumors are prevalent in young woman, often relapsing rapidly. Additionally, most (but not all) basal-like tumors lack expression of steroid hormone receptors (estrogen receptor and progesterone receptor) and human epidermal growth factor receptor 2, limiting targeted therapeutic options for these predominantly triple-negative breast cancers. This minireview will focus on new insights into the molecular etiology of these poor-prognosis tumors that underlie their intrinsic genomic instability, deregulated cell proliferation and apoptosis, and invasive tumor biology. We will also review ongoing efforts to translate these fundamental insights into improved therapies for women with BLBC.
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Affiliation(s)
- Daniel J Toft
- Division of Endocrinology, Department of Medicine, Robert H. Lurie Comprehensive Cancer Center, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 6061, USA
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79
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Abstract
Autoimmune diseases appear to have multiple contributing factors including genetics, epigenetics, environmental factors, and aging. The predominance of females among patients with autoimmune diseases suggests possible involvement of the X chromosome and X chromosome inactivation. X chromosome inactivation is an epigenetic event resulting in multiple levels of control for modulation of the expression of X-linked genes in normal female cells such that there remains only one active X chromosome in the cell. The extent of this control is unique among the chromosomes and has the potential for problems when regulation is disrupted. Here we discuss the X chromosome inactivation process and how the X chromosome and X chromosome inactivation may be involved in development of autoimmune disorders.
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Affiliation(s)
- Wesley H Brooks
- Experimental HTS, Drug Discovery, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL 33612-9416, USA.
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80
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de Ruijter TC, Veeck J, de Hoon JPJ, van Engeland M, Tjan-Heijnen VC. Characteristics of triple-negative breast cancer. J Cancer Res Clin Oncol 2010; 137:183-92. [PMID: 21069385 PMCID: PMC3018596 DOI: 10.1007/s00432-010-0957-x] [Citation(s) in RCA: 189] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 10/20/2010] [Indexed: 12/19/2022]
Abstract
Background Triple-negative breast cancers (TNBC) neither express hormone receptors, nor overexpress HER2. They are associated with poor prognosis, as defined by low five-year survival and high recurrence rates after adjuvant therapy. Overall, TNBC share striking similarities with basal-like breast cancers (BBC), so a number of studies considered them being the same. The purpose of this review is to summarise the latest findings on TNBC concerning its relation and delineation to BBC, discuss the developmental pathways involved and address clinical implications for this complex type of breast cancer. Methods The recent literature from PubMed and Medline databases was reviewed. Results Not all TNBC are of the intrinsic BBC subtype (nonbasal (NB)-TNBC), nor are all BBC triple-negative (non-triple-negative (NTN)-BBC). There is increasing evidence that a triple-negative, basal-like breast cancer (TNBBC) subtype develops mainly through a BRCA1-related pathway. Somatic mutations that contribute to NTN-BBC and NB-TNBC development are possibly not related to this pathway, but may occur randomly due to increased genomic instability in these tumours. Several therapeutic options exist for TNBBC, which exhibited promising results in recent clinical trials. Cytotoxic therapies, e.g. combined treatment with anthracyclines or taxanes, achieved good tumour regression rates in the neo-adjuvant setting, but also showed considerable recurrence during the first 5 years after therapy. Targeted therapy options involve PARP1 and EGFR inhibition, although both approaches still need further investigation. Conclusions TNBC and BBC are not the same disease entity. The TNBBC subtype shows the largest homogeneity in terms of tumour development, prognosis and clinical intervention options.
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Affiliation(s)
- Tim C de Ruijter
- Division of Medical Oncology, Department of Internal Medicine, GROW School for Oncology and Developmental Biology, Maastricht University Medical Centre, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands
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81
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Hasegawa Y, Brockdorff N, Kawano S, Tsutui K, Tsutui K, Nakagawa S. The Matrix Protein hnRNP U Is Required for Chromosomal Localization of Xist RNA. Dev Cell 2010; 19:469-76. [DOI: 10.1016/j.devcel.2010.08.006] [Citation(s) in RCA: 279] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Revised: 05/06/2010] [Accepted: 06/28/2010] [Indexed: 01/12/2023]
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82
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Rapamycin synergizes cisplatin sensitivity in basal-like breast cancer cells through up-regulation of p73. Breast Cancer Res Treat 2010; 128:301-13. [DOI: 10.1007/s10549-010-1055-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Accepted: 07/07/2010] [Indexed: 02/01/2023]
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83
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Abstract
X inactivation is the process that brings about the dosage equivalence of X-linked genes in females to that of males. This complex process initiated at a very early stage of female embryonic development is orchestrated by long non-coding RNAs transcribed in both sense and antisense orientation. Recent studies present contradicting evidence for the role of small RNAs and RNase III enzyme Dicer in the X inactivation process. In this review, I discuss these results in the overall perspective of X inactivation and gene silencing.
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Affiliation(s)
- Satya K Kota
- Institute of Molecular Genetics, CNRS, UMR5535, 34293 Montpelier Cedex 5, France.
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84
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Abstract
Germline mutations in the BRCA1 and BRCA2 genes are characterized by deficient repair of DNA double-strand breaks by homologous recombination. Defective DNA double-strand break repair has been not only implicated as a key contributor to tumorigenesis in mutation carriers but also represents a potential target for therapy. The transcriptional similarities between BRCA1-deficient tumors and sporadic tumors of the basal-like subtype have led to the investigation of homologous recombination repair-directed therapy in triple-negative tumors, which demonstrates overlap with the basal-like subtype. We broaden the scope of this topic by addressing a "repair-defective" rather than "BRCA1-like" phenotype. We discuss structural and functional aspects of key repair proteins including BRCA1, BRCA2, BRCA1 interacting protein C-terminal helicase 1, and partner and localizer of BRCA2 and describe the phenotypic consequences of their loss at the cellular, tissue, and organism level. We review potential mechanisms of repair pathway dysfunction in sporadic tumors and address how the identification of such defects may guide the application of repair-directed therapies.
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85
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Rowe BP, Glazer PM. Emergence of rationally designed therapeutic strategies for breast cancer targeting DNA repair mechanisms. Breast Cancer Res 2010; 12:203. [PMID: 20459590 PMCID: PMC2879573 DOI: 10.1186/bcr2566] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Accumulating evidence suggests that many cancers, including BRCA1- and BRCA2-associated breast cancers, are deficient in DNA repair processes. Both hereditary and sporadic breast cancers have been found to have significant downregulation of repair factors. This has provided opportunities to exploit DNA repair deficiencies, whether acquired or inherited. Here, we review efforts to exploit DNA repair deficiencies in tumors, with a focus on breast cancer. A variety of agents, including PARP (poly [ADP-ribose] polymerase) inhibitors, are currently under investigation in clinical trials and available results will be reviewed.
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Affiliation(s)
- Bryan P Rowe
- Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06520-8040, USA.
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86
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Marshall H, Bhaumik M, Aviv H, Moore D, Yao M, Dutta J, Rahim H, Gounder M, Ganesan S, Saleem A, Rubin E. Deficiency of the dual ubiquitin/SUMO ligase Topors results in genetic instability and an increased rate of malignancy in mice. BMC Mol Biol 2010; 11:31. [PMID: 20429939 PMCID: PMC2873312 DOI: 10.1186/1471-2199-11-31] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2009] [Accepted: 04/29/2010] [Indexed: 01/07/2023] Open
Abstract
Background Topors is a nuclear protein that co-localizes with promyelocytic leukemia bodies and has both ubiquitin and SUMO E3 ligase activity. Expression studies implicated Topors as a tumor suppressor in various malignancies. To gain insight into the function of Topors, we generated a Topors-deficient mouse strain. Results Mice homozygous for a mutant Topors allele exhibited a high rate of perinatal mortality and decreased lifespan. In addition, heterozygotes were found to have an increased incidence of malignancy, involving a variety of tissues. Consistent with this finding, primary embryonic fibroblasts lacking Topors exhibited an increased rate of malignant transformation, associated with aneuploidy and defective chromosomal segregation. While loss of Topors did not alter sensitivity to DNA-damaging or microtubule-targeting agents, cells lacking Topors exhibited altered pericentric heterochromatin, manifested by mislocalization of HP1α and an increase in transcription from pericentric major satellite DNA. Topors-deficient cells exhibited a transcriptional profile similar to that of cells treated with histone deacetylase inhibitors, and were resistant to the anti-proliferative effects of the histone deacetylase inhibitor trichostatin A. Conclusion These results indicate a unique role for Topors in the maintenance of genomic stability and pericentric heterochromatin, as well as in cellular sensitivity to histone deacetylase inhibitors.
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Affiliation(s)
- Henderson Marshall
- Department of Pharmacology, Cancer Institute of New Jersey, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 195 Little Albany Street, New Brunswick, NJ 08901, USA
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87
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Abstract
Epigenetic regulation is important for stable maintenance of cell identity. For continued function of organs and tissues, illegitimate changes in cell identity must be avoided. Failure to do so can trigger tumour development and disease. How epigenetic patterns are established during cell differentiation has been explored by studying model systems such as X inactivation. Mammals balance the X-linked gene dosage between the sexes by silencing of one of the two X chromosomes in females. This is initiated by expression of the non-coding X-inactive specific transcript (Xist) RNA and depends on specific cellular contexts, in which essential silencing factors are expressed. Normally X inactivation is initiated in early embryogenesis, but recent reports identified instances where Xist is expressed and can initiate gene repression. Here we describe the features that characterize the cellular permissivity to initiation of X inactivation and note that these can also occur in cancer cells and in specific haematopoietic progenitors. We propose that embryonic pathways for epigenetic regulation are re-established in adult progenitor cells and tumour cells. Understanding their reactivation will deepen our understanding of tumourigenesis and may be exploited for cancer therapy.
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Affiliation(s)
- Ruben Agrelo
- Research Institute of Molecular Pathology, Vienna, Austria.
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88
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Tulchin N, Chambon M, Juan G, Dikman S, Strauchen J, Ornstein L, Billack B, Woods NT, Monteiro ANA. BRCA1 protein and nucleolin colocalize in breast carcinoma tissue and cancer cell lines. THE AMERICAN JOURNAL OF PATHOLOGY 2010; 176:1203-14. [PMID: 20075200 PMCID: PMC2832143 DOI: 10.2353/ajpath.2010.081063] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 11/24/2009] [Indexed: 12/20/2022]
Abstract
The breast and ovarian cancer susceptibility gene BRCA1 encodes a tumor suppressor. BRCA1 protein, which is involved in DNA damage response, has been thought to be found primarily in cell nuclei. In the present investigation, immunohistological studies of BRCA1 protein in frozen breast cancer tissue and MCF7 and HeLa cell lines revealed BRCA1 expression in both nucleoli and nucleoplasmic foci. Immunoelectron microscopic studies of estrogen-stimulated MCF7 cells demonstrated BRCA1 protein localization in the granular components of the nucleolus. Moreover, immunofluorescence of BRCA1 and nucleolin double-labeling showed colocalization in both nucleoli and nucleoplasmic foci in breast tumor cells and asynchronously growing MCF7 and HeLa cells. Multiparameter analysis of BRCA1 and nucleolin in relation to cell cycle position (DNA content) showed expression during G1-S and persistence of BRCA1 during G2/M. After gamma-irradiation of MCF7 cells, BRCA1 protein dispersed from nucleoli and nucleoplasmic foci to other nucleoplasmic sites, which did not colocalize with nucleolin. Small interfering RNA-mediated knockdown of BRCA1 protein resulted in decreased immunofluorescence staining, which was confirmed by Western blotting. The observed colocalization of BRCA1 and nucleolin raises new possibilities for the nucleoplasm-nucleolus pathways of these proteins and their functional significance.
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Affiliation(s)
- Natalie Tulchin
- Department of Pathology, Box 1194, Mt. Sinai School of Medicine, 1 Gustave L. Levy Place, New York, NY 10029, USA.
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89
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Dawson SJ, Provenzano E, Caldas C. Triple negative breast cancers: clinical and prognostic implications. Eur J Cancer 2010; 45 Suppl 1:27-40. [PMID: 19775602 DOI: 10.1016/s0959-8049(09)70013-9] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Triple negative breast cancers are defined by the absence of oestrogen, progesterone and HER2 expression. Most triple negative cancers display distinct clinical and pathological characteristics with a high proportion of these tumours occurring at a younger age of onset and in African-American women. Triple negative tumours typically demonstrate high histological grade and are the most common breast cancer subtype in BRCA1 carriers. In addition, many of the features of triple negative cancers are similar to those identified in the basal-like molecular subtype which has recently been characterised by gene expression profiling. Although the two groups overlap, they are not synonymous. Triple negative breast cancers are of pivotal clinical importance given the lack of therapeutic options. The prognostic significance of triple negative tumours remains unclear since the group is heterogeneous and worst prognosis seems to be mostly confined to those that express basal cytokeratins or epidermal growth factor receptor (EGFR). This review focuses on outlining the pathological, molecular, and clinical features of triple negative breast cancers, discusses its prognostic value and summarises current therapeutic approaches and future directions of research.
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Affiliation(s)
- S J Dawson
- Department of Oncology, University of Cambridge, Cambridge, UK
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90
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Lustberg MB, Ramaswamy B. Epigenetic targeting in breast cancer: therapeutic impact and future direction. ACTA ACUST UNITED AC 2010; 22:369-81. [PMID: 19890494 DOI: 10.1358/dnp.2009.22.7.1405072] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Breast carcinogenesis is a multistep process involving both genetic and epigenetic changes. Epigenetics is defined as a reversible and heritable change in gene expression that is not accompanied by alteration in gene sequence. DNA methylation and histone modifications are the two major epigenetic changes that influence gene expression in cancer. The interaction between methylation and histone modification is intricately orchestrated by the formation of repressor complexes. Several genes involved in proliferation, antiapoptosis, invasion and metastasis have been shown to be methylated in various malignant and premalignant breast neoplasms. The histone deacetylase inhibitors (HDi) have emerged as an important class of drugs to be used synergistically with other systemic therapies in the treatment of breast cancer. Since epigenetic changes are potentially reversible processes, much effort has been directed toward understanding this mechanism with the goal of finding novel therapies as well as more refined diagnostic and prognostic tools in breast cancer.
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Affiliation(s)
- M B Lustberg
- Division of Hematology and Oncology, Comprehensive Cancer Center, The Ohio State University Medical Center, USA
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91
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Abstract
Lung cancer is one of the most common cancers in the world. While historically, more men than women have died from lung cancer as a result of higher numbers of male smokers, the sex mortality ratio is now showing signs of narrowing. Tumors in women with lung cancer may be slightly different to those in men with lung cancer. This review focuses on biomarkers differentially expressed between female and male patients with lung cancer. There is variation in gene expression between men and women in some genes that encode carcinogen-metabolizing enzymes (CYP1A1, GSTM). Gastrin-releasing peptide (GRP), a bombesin-like peptide, is present in two actively transcribed alleles in women compared with men. Higher prevalence of infection with oncogenic variants human papilloma viruses (HPVs) HPV16 and HPV18 has been suggested in women. A higher frequency of G to T transversion was found in the p53 gene in lung tumors of women. KRAS mutation was found to be more frequent in women with resected non-small cell lung cancer (NSCLC) than in men with resected NSCLC. Epidermal growth factor receptor (EGFR) mutation is more frequently found in lung tumors from women, but the confounding effect of tobacco exposure may explain this difference. Lower levels of ERCC1 and BRCA1 have been reported in women with NSCLC. Lung tumors from women are more likely to express estrogen receptors than those from men. An in silico analysis of transcriptome datasets from lung cancer patients demonstrated that only seven genes (in at least two studies) had significantly different expression patterns in male versus female patients. All of these genes are localized on the sex chromosomes: one on chromosome X and six on chromosome Y. Many areas remain under debate and there are still significant gaps in our understanding, particularly how sex-linked factors relate to lung cancer risk, and to biological and clinical behaviors. Future research into lung cancer needs to address these gender differences more specifically.
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Affiliation(s)
- David Planchard
- Department of Medicine, Institut Gustave Roussy, Villejuif, France
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92
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Barakat TS, Gribnau J. X chromosome inactivation and embryonic stem cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 695:132-54. [PMID: 21222204 DOI: 10.1007/978-1-4419-7037-4_10] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
X chromosome inactivation (XCI) is a process required to equalize the dosage of X-encoded genes between female and male cells. XCI is initiated very early during female embryonic development or upon differentiation of female embryonic stem (ES) cells and results in inactivation of one X chromosome in every female somatic cell. The regulation of XCI involves factors that also play a crucial role in ES cell maintenance and differentiation and the XCI process therefore provides a beautiful paradigm to study ES cell biology. In this chapter we describe the important cis and trans acting regulators of XCI and introduce the models that have been postulated to explain initiation of XCI in female cells only. We also discuss the proteins involved in the establishment of the inactive X chromosome and describe the different chromatin modifications associated with the inactivation process. Finally, we describe the potential of mouse and human ES and induced pluripotent stem (iPS) cells as model systems to study the XCI process.
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Affiliation(s)
- Tahsin Stefan Barakat
- Department of Reproduction and Development, University Medical Center, Room Ee 09-71, Erasmus MC, 3015 GE, Rotterdam, Netherlands
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93
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Navaraj A, Finnberg N, Dicker DT, Yang W, Matthew EM, El-Deiry WS. Reduced cell death, invasive and angiogenic features conferred by BRCA1-deficiency in mammary epithelial cells transformed with H-Ras. Cancer Biol Ther 2009; 8:2417-44. [PMID: 20038817 DOI: 10.4161/cbt.8.24.10850] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
To investigate the role of tumor suppressors BRCA1 and p53 proteins in human breast tumorigenesis, we transformed immortalized human mammary epithelial cells, MCF10A, with or without BRCA1/p53 gene-specific knockdowns. Stable knockdown of BRCA1 alone in MCF10A cells led to centrosome amplification, impaired p53 protein stability, increased sensitivity towards DNA-damaging agents, defective chromosomal condensation at mitosis and elevated protein levels of cyclin D1 and c-myc. While over-expression of mutant H-Ras transformed MCF10A cells, depletion of BRCA1 dramatically enhanced the in vivo tumorigenesis that was associated with higher levels of VEGF, enhanced vascularization and less apoptosis in the BRCA1-deficient Ras-transformed tumors. The Ras-transformed BRCA1-deficient tumors exhibited features of the epithelial-to-mesenchymal transition, appeared to secrete matrix metalloproteases as visualized by in vivo bio-imaging of tumors using fluorescent probe MMP680, and were locally metastatic to lymph nodes. Our results suggest that loss of BRCA1 function may contribute to the aggressiveness of Ras-MAPK driven human breast cancer with associated increase in levels of cyclin D1 and c-myc, enhanced MAPK activity, angiogenic potential & invasiveness. This mammary xenograft tumor model may be useful as a tool to understand human breast tumor angiogenesis and metastasis, as well as to test candidate therapeutics.
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Affiliation(s)
- Arunasalam Navaraj
- Laboratory of Molecular Oncology and Cell Cycle Regulation, Department of Medicine (Hematology/Oncology), University of Pennsylvania School of Medicine, Philadelphia, PA, USA
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94
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Abstract
A substantial part of all hereditary breast cancer cases is caused by BRCA1 germline mutations. In this review, we will discuss the insights into BRCA1 functions that we obtained from mouse models with conventional and conditional mutations in Brca1. The most advanced models closely resemble human BRCA1-related breast cancer and may therefore be useful for addressing clinically relevant questions.
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95
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Understanding the functions of BRCA1 in the DNA-damage response. Biochem Soc Trans 2009; 37:597-604. [PMID: 19442256 DOI: 10.1042/bst0370597] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Inheritance of a mutation in BRCA1 (breast cancer 1 early-onset) results in predisposition to early-onset breast and ovarian cancer. Tumours in these individuals arise after somatic mutation or loss of the wild-type allele. Loss of BRCA1 function leads to a profound increase in genomic instability involving the accumulation of mutations, DNA breaks and gross chromosomal rearrangements. Accordingly, BRCA1 has been implicated as an important factor involved in both the repair of DNA lesions and in the regulation of cell-cycle checkpoints in response to DNA damage. However, the molecular mechanism through which BRCA1 functions to preserve genome stability remains unclear. In the present article, we examine the different ways in which BRCA1 might influence the repair of DNA damage and the preservation of genome integrity, taking into account what is currently known about its interactions with other proteins, its biochemical activity and its nuclear localization.
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96
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Sirchia SM, Tabano S, Monti L, Recalcati MP, Gariboldi M, Grati FR, Porta G, Finelli P, Radice P, Miozzo M. Misbehaviour of XIST RNA in breast cancer cells. PLoS One 2009; 4:e5559. [PMID: 19440381 PMCID: PMC2679222 DOI: 10.1371/journal.pone.0005559] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Accepted: 04/14/2009] [Indexed: 11/18/2022] Open
Abstract
A role of X chromosome inactivation process in the development of breast cancer have been suggested. In particular, the relationship between the breast cancer predisposing gene BRCA1 and XIST, the main mediator of X chromosome inactivation, has been intensely investigated, but still remains controversial. We investigated this topic by assessing XIST behaviour in different groups of breast carcinomas and in a panel of breast cancer cell lines both BRCA1 mutant and wild type. In addition, we evaluated the occurrence of broader defects of heterochromatin in relation to BRCA1 status in breast cancer cells. We provide evidence that in breast cancer cells BRCA1 is involved in XIST regulation on the active X chromosome, but not in its localization as previously suggested, and that XIST can be unusually expressed by an active X and can decorate it. This indicates that the detection of XIST cloud in cancer cell is not synonymous of the presence of an inactive X chromosome. Moreover, we show that global heterochromatin defects observed in breast tumor cells are independent of BRCA1 status. Our observations sheds light on a possible previously uncharacterized mechanism of breast carcinogenesis mediated by XIST misbehaviour, particularly in BRCA1-related cancers. Moreover, the significant higher levels of XIST-RNA detected in BRCA1-associated respect to sporadic basal-like cancers, opens the possibility to use XIST expression as a marker to discriminate between the two groups of tumors.
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Affiliation(s)
- Silvia M Sirchia
- Department of Medicine, Surgery and Dentistry, Medical Genetics Unit, Università degli Studi di Milano, Milano, Italy.
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97
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Rohozinski J, Anderson ML, Broaddus RE, Edwards CL, Bishop CE. Spermatogenesis associated retrogenes are expressed in the human ovary and ovarian cancers. PLoS One 2009; 4:e5064. [PMID: 19333399 PMCID: PMC2660244 DOI: 10.1371/journal.pone.0005064] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Accepted: 02/06/2009] [Indexed: 12/24/2022] Open
Abstract
Background Ovarian cancer is the second most prevalent gynecologic cancer in women. However, it is by far the most lethal. This is generally attributed to the absence of easily detectable markers specific to ovarian cancers that can be used for early diagnosis and specific therapeutic targets. Methodology/Principal Findings Using end point PCR we have found that a family of retrogenes, previously thought to be expressed only in the male testis during spermatogenesis in man, are also expressed in normal ovarian tissue and a large percentage of ovarian cancers. In man there are at least eleven such autosomal retrogenes, which are intronless copies of genes on the X chromosome, essential for normal spermatogenesis and expressed specifically in the human testis. We tested for the expression of five of the known retrogenes, UTP14C, PGK2, RPL10L, RPL39L and UBL4B in normal human ovary and ovarian cancers. Conclusions/Significance We propose that the activation of the testis specific retrogenes in the ovary and ovarian cancers is of biological significance in humans. Because these retrogenes are specifically expressed in the ovary and ovarian cancers in the female they may prove useful in developing new diagnostic and/or therapeutic targets for ovarian cancer.
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Affiliation(s)
- Jan Rohozinski
- Department of Obstetrics and Gynecology, Baylor College of Medicine, Houston, TX, USA.
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98
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Fertility in women with BRCA mutations: a case-control study. Fertil Steril 2009; 93:1805-8. [PMID: 19200971 DOI: 10.1016/j.fertnstert.2008.12.052] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2008] [Revised: 10/28/2008] [Accepted: 12/12/2008] [Indexed: 01/16/2023]
Abstract
OBJECTIVE To investigate whether or not fertility is reduced in women carrying mutations in the BRCA genes (BRCA1 and BRCA2), compared with noncarrier family members. DESIGN Matched case-control study. SETTING Academic. PATIENT(S) A total of 2,254 BRCA carriers and 764 noncarrier controls who were from the same families as the carriers, but tested negative for the BRCA mutation. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) History of fertility problems (yes/no) and prior use of fertility medications (yes/no) in cases and controls, obtained through administered questionnaire. RESULT(S) There was no difference in mean parity between carriers (1.9) and noncarriers (1.9). CONCLUSION(S) This study, which is the first epidemiologic study to specifically investigate the effect of carrying a BRCA mutation on parity and fertility, suggests that there is likely little or no effect of the BRCA gene mutation on fertility. To our knowledge previous epidemiologic studies have not investigated the effect of carrying a BRCA mutation on parity or fertility. However, we expect that if fertility differences exist, they would be toward the limits of reproductive life, thus larger studies with age-stratified analyses are needed to definitively answer this question.
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99
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Venkitaraman AR. Linking the Cellular Functions ofBRCAGenes to Cancer Pathogenesis and Treatment. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2009; 4:461-87. [DOI: 10.1146/annurev.pathol.3.121806.151422] [Citation(s) in RCA: 168] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ashok R. Venkitaraman
- Department of Oncology, University of Cambridge, and the Medical Research Council Cancer Cell Unit, Hutchison/MRC Research Center, Cambridge CB2 0XZ, United Kingdom;
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100
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Reguart N, Cardona AF, Carrasco E, Gomez P, Taron M, Rosell R. BRCA1: A New Genomic Marker for Non–Small-Cell Lung Cancer. Clin Lung Cancer 2008; 9:331-9. [PMID: 19073515 DOI: 10.3816/clc.2008.n.048] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Noemí Reguart
- Medical Oncology Service, Catalan Institute of Oncology, ICO, Hospital Germans Trias i Pujol, Badalona, Barcelona, Spain
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