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alternative lengthening of telomeres

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https://www.readbyqxmd.com/read/29321523/integrative-genomic-and-transcriptomic-analysis-of-leiomyosarcoma
#1
Priya Chudasama, Sadaf S Mughal, Mathijs A Sanders, Daniel Hübschmann, Inn Chung, Katharina I Deeg, Siao-Han Wong, Sophie Rabe, Mario Hlevnjak, Marc Zapatka, Aurélie Ernst, Kortine Kleinheinz, Matthias Schlesner, Lina Sieverling, Barbara Klink, Evelin Schröck, Remco M Hoogenboezem, Bernd Kasper, Christoph E Heilig, Gerlinde Egerer, Stephan Wolf, Christof von Kalle, Roland Eils, Albrecht Stenzinger, Wilko Weichert, Hanno Glimm, Stefan Gröschel, Hans-Georg Kopp, Georg Omlor, Burkhard Lehner, Sebastian Bauer, Simon Schimmack, Alexis Ulrich, Gunhild Mechtersheimer, Karsten Rippe, Benedikt Brors, Barbara Hutter, Marcus Renner, Peter Hohenberger, Claudia Scholl, Stefan Fröhling
Leiomyosarcoma (LMS) is an aggressive mesenchymal malignancy with few therapeutic options. The mechanisms underlying LMS development, including clinically actionable genetic vulnerabilities, are largely unknown. Here we show, using whole-exome and transcriptome sequencing, that LMS tumors are characterized by substantial mutational heterogeneity, near-universal inactivation of TP53 and RB1, widespread DNA copy number alterations including chromothripsis, and frequent whole-genome duplication. Furthermore, we detect alternative telomere lengthening in 78% of cases and identify recurrent alterations in telomere maintenance genes such as ATRX, RBL2, and SP100, providing insight into the genetic basis of this mechanism...
January 10, 2018: Nature Communications
https://www.readbyqxmd.com/read/29321190/genomic-landscape-of-pancreatic-neuroendocrine-tumours-the-international-cancer-genome-consortium
#2
Andrea Mafficini, Aldo Scarpa
Neuroendocrine tumours (NETs) may arise throughout the body and are a highly heterogeneous, relatively rare class of neoplasms difficult to study also for the lack of disease models. Despite this, knowledge on their molecular alterations has expanded in the latest years, also building from genetic syndromes causing their onset. Pancreatic NETs (PanNETs) have been among the most studied, and research so far has outlined a series of recurring features, as inactivation of MEN1, VHL, TSC1/2 genes, and hyperactivation of the PI3K/mTOR pathway...
January 10, 2018: Journal of Endocrinology
https://www.readbyqxmd.com/read/29273061/diagnosis-and-treatment-of-alt-tumors-is-trabectedin-a-new-therapeutic-option
#3
REVIEW
Luca Pompili, Carlo Leonetti, Annamaria Biroccio, Erica Salvati
Telomeres are specialized nucleoprotein structures responsible for protecting chromosome ends in order to prevent the loss of genomic information. Telomere maintenance is required for achieving immortality by neoplastic cells. While most cancer cells rely on telomerase re-activation for linear chromosome maintenance and sustained proliferation, a significant population of cancers (10-15%) employs telomerase-independent strategies, collectively referred to as Alternative Lengthening of Telomeres (ALT). ALT mechanisms involve different types of homology-directed telomere recombination and synthesis...
December 22, 2017: Journal of Experimental & Clinical Cancer Research: CR
https://www.readbyqxmd.com/read/29191871/mr-imaging-characteristics-associate-with-tumor-associated-macrophages-in-glioblastoma-and-provide-an-improved-signature-for-survival-prognostication
#4
J Zhou, M V Reddy, B K J Wilson, D A Blair, A Taha, C M Frampton, R A Eiholzer, P Y C Gan, F Ziad, Z Thotathil, S Kirs, N A Hung, J A Royds, T L Slatter
BACKGROUND AND PURPOSE: In glioblastoma, tumor-associated macrophages have tumor-promoting properties. This study determined whether routine MR imaging features could predict molecular subtypes of glioblastoma that differ in the content of tumor-associated macrophages. MATERIALS AND METHODS: Seven internally derived MR imaging features were assessed in 180 patients, and 25 features from the Visually AcceSAble Rembrandt Images feature set were assessed in 164 patients...
November 30, 2017: AJNR. American Journal of Neuroradiology
https://www.readbyqxmd.com/read/29113290/telomere-dna-damage-signaling-regulates-cancer-stem-cell-evolution-epithelial-mesenchymal-transition-and-metastasis
#5
Angelica M Lagunas, Jianchun Wu, David L Crowe
Chromosome ends are protected by telomeres that prevent DNA damage response and degradation. When telomeres become critically short, the DNA damage response is activated at chromosome ends which induces cellular senescence or apoptosis. Telomeres are protected by the double stranded DNA binding protein TRF2 and maintained by telomerase or a recombination based mechanism known as alternative lengthening of telomeres (ALT). Telomerase is expressed in the basal layer of the epidermis, and stem cells in epidermis have longer telomeres than proliferating populations...
October 6, 2017: Oncotarget
https://www.readbyqxmd.com/read/29106411/extrachromosomal-telomere-repeat-dna-is-linked-to-alt-development-via-cgas-sting-dna-sensing-pathway
#6
Yi-An Chen, Yi-Ling Shen, Hsuan-Yu Hsia, Yee-Peng Tiang, Tzu-Ling Sung, Liuh-Yow Chen
Extrachromosomal telomere repeat (ECTR) DNA is unique to cancer cells that maintain telomeres through the alternative lengthening of telomeres (ALT) pathway, but the role of ECTRs in ALT development remains elusive. We found that induction of ECTRs in normal human fibroblasts activated the cGAS-STING-TBK1-IRF3 signaling axis to trigger IFNβ production and a type I interferon response, resulting in cell-proliferation defects. In contrast, ALT cancer cells are commonly defective in sensing cytosolic DNA. We found that STING expression was inhibited in ALT cancer cell lines and transformed ALT cells...
November 6, 2017: Nature Structural & Molecular Biology
https://www.readbyqxmd.com/read/29093807/biological-and-clinical-implications-of-telomere-dysfunction-in-myeloid-malignancies
#7
REVIEW
Ashwin Kishtagari, Justin Watts
Telomeres at the ends of linear chromosomes protect the genome. Telomeres shorten with each round of cell division, placing a finite limit on cell growth. Telomere attrition is associated with cell senescence and apoptosis. Telomerase, a specialized ribonucleoprotein complex, maintains telomeres homeostasis through repeat addition of telomere sequences to the 3' telomeric overhang. Telomere biology is closely related to cancer and normal aging. Upregulation of telomerase or activation of the alternative pathway of telomere lengthening is a hallmark of cancer cells, making telomerase an attractive target for cancer therapeutics...
November 2017: Therapeutic Advances in Hematology
https://www.readbyqxmd.com/read/28969871/alternative-lengthening-of-telomeres-dna-repair-pathways-converge
#8
REVIEW
Alexander P Sobinoff, Hilda A Pickett
Telomeres shorten during each cellular division, with cumulative attrition resulting in telomeric damage and replicative senescence. Bypass of replicative senescence precipitates catastrophic telomere shortening or crisis, and is characterized by widespread genomic instability. Activation of a telomere maintenance mechanism (TMM) is necessary to stabilise the genome and establish cellular immortality through the reconstitution of telomere capping function. The alternative lengthening of telomeres (ALT) pathway is a TMM frequently activated in tumors of mesenchymal or neuroepithelial origin...
September 29, 2017: Trends in Genetics: TIG
https://www.readbyqxmd.com/read/28877996/blm-and-slx4-play-opposing-roles-in-recombination-dependent-replication-at-human-telomeres
#9
Alexander P Sobinoff, Joshua Am Allen, Axel A Neumann, Sile F Yang, Monica E Walsh, Jeremy D Henson, Roger R Reddel, Hilda A Pickett
Alternative lengthening of telomeres (ALT) is a telomere lengthening pathway that predominates in aggressive tumors of mesenchymal origin; however, the underlying mechanism of telomere synthesis is not fully understood. Here, we show that the BLM-TOP3A-RMI (BTR) dissolvase complex is required for ALT-mediated telomere synthesis. We propose that recombination intermediates formed during strand invasion are processed by the BTR complex, initiating rapid and extensive POLD3-dependent telomere synthesis followed by dissolution, with no overall exchange of telomeric DNA...
October 2, 2017: EMBO Journal
https://www.readbyqxmd.com/read/28796347/clinicopathological-analysis-of-atrx-daxx-and-notch-receptor-expression-in-angiosarcomas
#10
Gauri Panse, John Sa Chrisinger, Cheuk H Leung, Davis R Ingram, Samia Khan, Khalida Wani, Heather Lin, Alexander J Lazar, Wei-Lien Wang
AIMS: Multiple genetic alterations, including alternative lengthening of telomeres (ALT) and NOTCH mutations, have been described in angiosarcoma. Loss of α-thalassaemia/mental retardation syndrome X-linked (ATRX) and death domain-associated protein 6 (DAXX) expression is frequently associated with the ALT phenotype. Additionally, inhibition of NOTCH signalling induces the development of malignant vascular tumours in mice, indicating a tumour suppressive role of the NOTCH pathway in the pathogenesis of angiosarcoma...
August 10, 2017: Histopathology
https://www.readbyqxmd.com/read/28760773/alternative-lengthening-of-telomeres-mediated-by-mitotic-dna-synthesis-engages-break-induced-replication-processes
#11
Jaewon Min, Woodring E Wright, Jerry W Shay
Alternative lengthening of telomeres (ALT) is a telomerase-independent telomere maintenance mechanism that occurs in a subset of cancers. By analyzing telomerase-positive cells and their human TERC knockout-derived ALT human cell lines, we show that ALT cells harbor more fragile telomeres representing telomere replication problems. ALT-associated replication defects trigger mitotic DNA synthesis (MiDAS) at telomeres in a RAD52-dependent, but RAD51-independent, manner. Telomeric MiDAS is a conservative DNA synthesis process, potentially mediated by break-induced replication, similar to type II ALT survivors in Saccharomyces cerevisiae Replication stresses induced by ectopic oncogenic expression of cyclin E, G-quadruplexes, or R-loop formation facilitate the ALT pathway and lead to telomere clustering, a hallmark of ALT cancers...
October 15, 2017: Molecular and Cellular Biology
https://www.readbyqxmd.com/read/28755323/detection-of-the-alternative-lengthening-of-telomeres-pathway-in-malignant-gliomas-for-improved-molecular-diagnosis
#12
Anne Fogli, Marie-Véronique Demattei, Laetitia Corset, Catherine Vaurs-Barrière, Emmanuel Chautard, Julian Biau, Jean-Louis Kémény, Catherine Godfraind, Bruno Pereira, Toufik Khalil, Nathalie Grandin, Philippe Arnaud, Michel Charbonneau, Pierre Verrelle
Human malignant gliomas exhibit acquisition of either one of two telomere maintenance mechanisms, resulting from either reactivation of telomerase expression or activation of an alternative lengthening of telomeres (ALT) mechanism. In the present study, we analyzed 63 human malignant gliomas for the presence of ALT-specific extrachromosomal circles of telomeric DNA (C-circles) and measured telomerase expression, telomeric DNA content (Telo/Alu method), and telomeric repeat-containing RNAs (TERRA) levels. We also assessed histomolecular markers routinely used in clinical practice...
November 2017: Journal of Neuro-oncology
https://www.readbyqxmd.com/read/28716051/mir-380-5p-mediated-repression-of-tep1-and-tspyl5-interferes-with-telomerase-activity-and-favours-the-emergence-of-an-alt-like-phenotype-in-diffuse-malignant-peritoneal-mesothelioma-cells
#13
Graziella Cimino-Reale, Paolo Gandellini, Francesca Santambrogio, Marta Recagni, Nadia Zaffaroni, Marco Folini
BACKGROUND: Understanding the molecular/cellular underpinnings of diffuse malignant peritoneal mesothelioma (DMPM), a fatal malignancy with limited therapeutic options, is of utmost importance for the fruitful management of the disease. In this context, we previously found that telomerase activity (TA), which accounts for the limitless proliferative potential of cancer cells, is prognostic for disease relapse and cancer-related death in DMPM patients. Consequently, the identification of factors involved in telomerase activation/regulation may pave the way towards the development of novel therapeutic interventions for the disease...
July 17, 2017: Journal of Hematology & Oncology
https://www.readbyqxmd.com/read/28673972/fancm-brca1-and-blm-cooperatively-resolve-the-replication-stress-at-the-alt-telomeres
#14
Xiaolei Pan, William C Drosopoulos, Louisa Sethi, Advaitha Madireddy, Carl L Schildkraut, Dong Zhang
In the mammalian genome, certain genomic loci/regions pose greater challenges to the DNA replication machinery (i.e., the replisome) than others. Such known genomic loci/regions include centromeres, common fragile sites, subtelomeres, and telomeres. However, the detailed mechanism of how mammalian cells cope with the replication stress at these loci/regions is largely unknown. Here we show that depletion of FANCM, or of one of its obligatory binding partners, FAAP24, MHF1, and MHF2, induces replication stress primarily at the telomeres of cells that use the alternative lengthening of telomeres (ALT) pathway as their telomere maintenance mechanism...
July 18, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28652867/scattered-genomic-amplification-in-dedifferentiated-liposarcoma
#15
Nils Mandahl, Linda Magnusson, Jenny Nilsson, Björn Viklund, Elsa Arbajian, Fredrik Vult von Steyern, Anders Isaksson, Fredrik Mertens
BACKGROUND: Atypical lipomatous tumor (ALT), well differentiated liposarcoma (WDLS) and dedifferentiated liposarcoma (DDLS) are cytogenetically characterized by near-diploid karyotypes with no or few other aberrations than supernumerary ring or giant marker chromosomes, although DDLS tend to have somewhat more complex rearrangements. In contrast, pleomorphic liposarcomas (PLS) have highly aberrant and heterogeneous karyotypes. The ring and giant marker chromosomes contain discontinuous amplicons, in particular including multiple copies of the target genes CDK4, HMGA2 and MDM2 from 12q, but often also sequences from other chromosomes...
2017: Molecular Cytogenetics
https://www.readbyqxmd.com/read/28636942/extensive-proliferation-of-human-cancer-cells-with-ever-shorter-telomeres
#16
Rebecca A Dagg, Hilda A Pickett, Axel A Neumann, Christine E Napier, Jeremy D Henson, Erdahl T Teber, Jonathan W Arthur, C Patrick Reynolds, Jayne Murray, Michelle Haber, Alexander P Sobinoff, Loretta M S Lau, Roger R Reddel
Acquisition of replicative immortality is currently regarded as essential for malignant transformation. This is achieved by activating a telomere lengthening mechanism (TLM), either telomerase or alternative lengthening of telomeres, to counter normal telomere attrition. However, a substantial proportion of some cancer types, including glioblastomas, liposarcomas, retinoblastomas, and osteosarcomas, are reportedly TLM-negative. As serial samples of human tumors cannot usually be obtained to monitor telomere length changes, it has previously been impossible to determine whether tumors are truly TLM-deficient, there is a previously unrecognized TLM, or the assay results are false-negative...
June 20, 2017: Cell Reports
https://www.readbyqxmd.com/read/28597868/loss-of-progesterone-receptor-expression-is-an-early-tumorigenesis-event-associated-with-tumor-progression-and-shorter-survival-in-pancreatic-neuroendocrine-tumor-patients
#17
Sung Joo Kim, Soyeon An, Jae Hoon Lee, Joo Young Kim, Ki-Byung Song, Dae Wook Hwang, Song Cheol Kim, Eunsil Yu, Seung-Mo Hong
BACKGROUND: Pancreatic neuroendocrine tumors (PanNETs) are the second most common pancreatic neoplasms and there is no well-elucidated biomarker to stratify their detection and prognosis. Previous studies have reported that progesterone receptor (PR) expression status was associated with poorer survival in PanNET patients. METHODS: To validate previous studies, PR protein expression was assessed in 21 neuroendocrine microadenomas and 277 PanNETs and compared with clinicopathologic factors including patient survival...
July 2017: Journal of Pathology and Translational Medicine
https://www.readbyqxmd.com/read/28521363/a-cisplatin-derivative-tetra-pt-bpy-as-an-oncotherapeutic-agent-for-targeting-alt-cancer
#18
Xiao-Hui Zheng, Xin Nie, Yiming Fang, Zepeng Zhang, Yingnan Xiao, Zongwan Mao, Haiying Liu, Jian Ren, Feng Wang, Lixin Xia, Junjiu Huang, Yong Zhao
Background: In approximately 15% of human cancers, telomere length is maintained independently of telomerase by the homologous recombination (HR)-mediated alternative lengthening of telomeres (ALT) pathway. Whether the ALT pathway can be exploited for therapeutic treatment remains unknown. The purpose of this study is to develop oncotherapeutic agent to target ALT cancers. Methods: Surface plasmon resonance assay, antibody to G-quadruplex, and fluorescence in situ hybridization (FISH) were used to discover Tetra-Pt(bpy), a cisplatin derivative that specifically targets telomeric G-quadruplex...
October 1, 2017: Journal of the National Cancer Institute
https://www.readbyqxmd.com/read/28513547/epigenetic-regulation-of-telomere-maintenance-for-therapeutic-interventions-in-gliomas
#19
REVIEW
Elisabeth Naderlinger, Klaus Holzmann
High-grade astrocytoma of WHO grade 4 termed glioblastoma multiforme (GBM) is a common human brain tumor with poor patient outcome. Astrocytoma demonstrates two known telomere maintenance mechanisms (TMMs) based on telomerase activity (TA) and on alternative lengthening of telomeres (ALT). ALT is associated with lower tumor grades and better outcome. In contrast to ALT, regulation of TA in tumors by direct mutation and epigenetic activation of the hTERT promoter is well established. Here, we summarize the genetic background of TMMs in non-malignant cells and in cancer, in addition to clinical and pathological features of gliomas...
May 17, 2017: Genes
https://www.readbyqxmd.com/read/28500256/tzap-ing-telomeres-down-to-size
#20
Laura Garcia-Exposito, Roderick J O'Sullivan
The phenomenon of gradual telomere shortening has become a paradigm for how we understand the biology of aging and cancer. Cell proliferation is accompanied by cumulative telomere loss, and the aged cell either senesces, dies or transforms toward cancer. This transformation requires the activation of telomere elongation mechanisms in order to restore telomere length such that cell death or senescence programs are not induced. Most of the time, this occurs through telomerase reactivation. In other rare cases, the Alternative lengthening of telomeres (ALT) pathway hijacks DNA recombination-associated mechanisms to hyperextend telomeres, often to more than 50 kb...
June 2017: EMBO Reports
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