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alternative lengthening of telomeres

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https://www.readbyqxmd.com/read/28636942/extensive-proliferation-of-human-cancer-cells-with-ever-shorter-telomeres
#1
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
#2
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. Materials and 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...
June 8, 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
#3
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
#4
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
#5
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
https://www.readbyqxmd.com/read/28487353/the-chromatin-remodelling-factor-atrx-suppresses-r-loops-in-transcribed-telomeric-repeats
#6
Diu Tt Nguyen, Hsiao Phin J Voon, Barbara Xella, Caroline Scott, David Clynes, Christian Babbs, Helena Ayyub, Jon Kerry, Jacqueline A Sharpe, Jackie A Sloane-Stanley, Sue Butler, Chris A Fisher, Nicki E Gray, Thomas Jenuwein, Douglas R Higgs, Richard J Gibbons
ATRX is a chromatin remodelling factor found at a wide range of tandemly repeated sequences including telomeres (TTAGGG)n ATRX mutations are found in nearly all tumours that maintain their telomeres via the alternative lengthening of telomere (ALT) pathway, and ATRX is known to suppress this pathway. Here, we show that recruitment of ATRX to telomeric repeats depends on repeat number, orientation and, critically, on repeat transcription. Importantly, the transcribed telomeric repeats form RNA-DNA hybrids (R-loops) whose abundance correlates with the recruitment of ATRX Here, we show loss of ATRX is also associated with increased R-loop formation...
June 2017: EMBO Reports
https://www.readbyqxmd.com/read/28468887/stabilization-of-telomere-g-quadruplexes-interferes-with-human-herpesvirus-6a-chromosomal-integration
#7
Shella Gilbert-Girard, Annie Gravel, Sara Artusi, Sara N Richter, Nina Wallaschek, Benedikt B Kaufer, Louis Flamand
Human herpesvirus 6A and 6B (HHV-6A/B) can integrate their genomes into the telomeres of human chromosomes using a mechanism that remains poorly understood. To achieve a better understanding of the HHV-6 integration mechanism, we made use of BRACO-19, a compound that stabilizes G-quadruplex secondary structures and prevent telomere elongation by the telomerase complex. First, we analyzed the folding of telomeric sequences into G-quadruplex structures and their binding to BRACO-19 using G-quadruplex specific antibodies and surface plasmon resonance...
May 3, 2017: Journal of Virology
https://www.readbyqxmd.com/read/28467829/whole-genome-landscapes-of-major-melanoma-subtypes
#8
Nicholas K Hayward, James S Wilmott, Nicola Waddell, Peter A Johansson, Matthew A Field, Katia Nones, Ann-Marie Patch, Hojabr Kakavand, Ludmil B Alexandrov, Hazel Burke, Valerie Jakrot, Stephen Kazakoff, Oliver Holmes, Conrad Leonard, Radhakrishnan Sabarinathan, Loris Mularoni, Scott Wood, Qinying Xu, Nick Waddell, Varsha Tembe, Gulietta M Pupo, Ricardo De Paoli-Iseppi, Ricardo E Vilain, Ping Shang, Loretta M S Lau, Rebecca A Dagg, Sarah-Jane Schramm, Antonia Pritchard, Ken Dutton-Regester, Felicity Newell, Anna Fitzgerald, Catherine A Shang, Sean M Grimmond, Hilda A Pickett, Jean Y Yang, Jonathan R Stretch, Andreas Behren, Richard F Kefford, Peter Hersey, Georgina V Long, Jonathan Cebon, Mark Shackleton, Andrew J Spillane, Robyn P M Saw, Núria López-Bigas, John V Pearson, John F Thompson, Richard A Scolyer, Graham J Mann
Melanoma of the skin is a common cancer only in Europeans, whereas it arises in internal body surfaces (mucosal sites) and on the hands and feet (acral sites) in people throughout the world. Here we report analysis of whole-genome sequences from cutaneous, acral and mucosal subtypes of melanoma. The heavily mutated landscape of coding and non-coding mutations in cutaneous melanoma resolved novel signatures of mutagenesis attributable to ultraviolet radiation. However, acral and mucosal melanomas were dominated by structural changes and mutation signatures of unknown aetiology, not previously identified in melanoma...
May 11, 2017: Nature
https://www.readbyqxmd.com/read/28452859/tert-mediated-and-atrx-mediated-telomere-maintenance-and-neuroblastoma
#9
Xiao-Feng Duan, Qiang Zhao
Neuroblastomas (NB) are one of the most common extracranial solid tumors in children, and they frequently display high heterogeneity in the disease course. With ongoing research, more information regarding the genetic etiology and molecular mechanisms underlying these contrasting phenotypes is being uncovered. The proto-oncogene MYCN is amplified in approximately 20% of NB cases and is considered a indicator of poor prognosis and an indicator of high-risk NB. The poor prognosis of high risk NB is incompletely explained by MYCN amplification...
April 27, 2017: Journal of Pediatric Hematology/oncology
https://www.readbyqxmd.com/read/28425984/withaferin-a-kills-cancer-cells-with-and-without-telomerase-chemical-computational-and-experimental-evidences
#10
Yue Yu, Shashank P Katiyar, Durai Sundar, Zeenia Kaul, Eijiro Miyako, Zhenya Zhang, Sunil C Kaul, Roger R Reddel, Renu Wadhwa
Maintenance of telomere length is the most consistent attribute of cancer cells. Tightly connected to their capacity to overcome replicative mortality, it is achieved either by activation of telomerase or an Alternative mechanism of Lengthening of Telomeres (ALT). Disruption of either of these mechanisms has been shown to induce DNA damage signalling leading to senescence or apoptosis. Telomerase inhibitors are considered as potential anticancer drugs but are ineffective for ALT cancers (~15% of all cancers)...
April 20, 2017: Cell Death & Disease
https://www.readbyqxmd.com/read/28412741/opposite-effects-of-gcn5-and-pcaf-knockdowns-on-the-alternative-mechanism-of-telomere-maintenance
#11
Maya Jeitany, Dalal Bakhos-Douaihy, David C Silvestre, Jose R Pineda, Nicolas Ugolin, Angela Moussa, Laurent R Gauthier, Didier Busso, Marie-Pierre Junier, Hervé Chneiweiss, Sylvie Chevillard, Chantal Desmaze, François D Boussin
Cancer cells can use a telomerase-independent mechanism, known as alternative lengthening of telomeres (ALT), to elongate their telomeres. General control non-derepressible 5 (GCN5) and P300/CBP-associated factor (PCAF) are two homologous acetyltransferases that are mutually exclusive subunits in SAGA-like complexes. Here, we reveal that down regulation of GCN5 and PCAF had differential effects on some phenotypic characteristics of ALT cells. Our results suggest that GCN5 is present at telomeres and opposes telomere recombination, in contrast to PCAF that may indirectly favour them in ALT cells...
April 18, 2017: Oncotarget
https://www.readbyqxmd.com/read/28398700/differential-requirements-for-dna-repair-proteins-in-immortalized-cell-lines-using-alternative-lengthening-of-telomere-mechanisms
#12
Alaina R Martinez, Zeenia Kaul, Jeffrey D Parvin, Joanna Groden
Cancer cells require telomere maintenance to enable uncontrolled growth. Most often telomerase is activated, although a subset of human cancers are telomerase-negative and depend on recombination-based mechanisms known as ALT (Alternative Lengthening of Telomeres). ALT depends on proteins that are essential for homologous recombination, including BLM and the MRN complex, to extend telomeres. This study surveyed the requirement for requisite homologous recombination proteins, yet to be studied in human ALT cell lines, by protein depletion using RNA interference...
April 11, 2017: Genes, Chromosomes & Cancer
https://www.readbyqxmd.com/read/28371511/alternative-lengthening-of-telomeres-and-atrx-daxx-loss-can-be-reliably-detected-in-fnas-of-pancreatic-neuroendocrine-tumors
#13
Christopher J VandenBussche, Derek B Allison, Mindy K Graham, Vivek Charu, Anne Marie Lennon, Christopher L Wolfgang, Ralph H Hruban, Christopher M Heaphy
BACKGROUND: Pancreatic neuroendocrine tumors (PanNETs) frequently use the alternative lengthening of telomeres (ALT) pathway for telomere maintenance. ALT is strongly correlated with α thalassemia-mental retardation, X linked (ATRX), and death domain-associated protein 6 (DAXX) alterations and a poor prognosis in patients with primary PanNET. Because fine-needle aspiration (FNA) is a noninvasive way to sample tumors, the authors evaluated whether they could accurately detect ALT and loss of ATRX/DAXX in a primary PanNET cohort of FNAs...
April 3, 2017: Cancer
https://www.readbyqxmd.com/read/28366536/the-human-ctc1-stn1-ten1-complex-regulates-telomere-maintenance-in-alt-cancer-cells
#14
Chenhui Huang, Pingping Jia, Megan Chastain, Olga Shiva, Weihang Chai
Maintaining functional telomeres is important for long-term proliferation of cells. About 15% of cancer cells are telomerase-negative and activate the alternative-lengthening of telomeres (ALT) pathway to maintain their telomeres. Recent studies have shown that the human CTC1/STN1/TEN1 complex (CST) plays a multi-faceted role in telomere maintenance in telomerase-expressing cancer cells. However, the role of CST in telomere maintenance in ALT cells is unclear. Here, we report that human CST forms a functional complex localizing in the ALT-associated PML bodies (APBs) in ALT cells throughout the cell cycle...
June 15, 2017: Experimental Cell Research
https://www.readbyqxmd.com/read/28265354/genistein-suppresses-the-proliferation-of-telomerase-negative-cells
#15
Chuan-Chuan Lin, Meng-Hsun Hsieh, Shu-Chun Teng
In both tumor and yeast cells that lack telomerase, telomeres are maintained via an alternative recombination mechanism. In this study, we tested genistein, a potential TOP2 inhibitor required for telomere-telomere recombination, on the repression of telomere-telomere recombination. Genistein on the repression of type II recombination on a tlc1 yeast strain was examined by the telomeric DNA structures using Southern blot analysis. Telomere patterns of freshly dissected tlc1 spores containing an empty plasmid (pYES2) or a yeast TOP2 (yTOP2) plasmid were analyzed...
March 2017: Food Science & Nutrition
https://www.readbyqxmd.com/read/28240303/transient-alt-activation-protects-human-primary-cells-from-chromosome-instability-induced-by-low-chronic-oxidative-stress
#16
Elisa Coluzzi, Rossella Buonsante, Stefano Leone, Anthony J Asmar, Kelley L Miller, Daniela Cimini, Antonella Sgura
Cells are often subjected to the effect of reactive oxygen species (ROS) as a result of both intracellular metabolism and exposure to exogenous factors. ROS-dependent oxidative stress can induce 8-oxodG within the GGG triplet found in the G-rich human telomeric sequence (TTAGGG), making telomeres highly susceptible to ROS-induced oxidative damage. Telomeres are nucleoprotein complexes that protect the ends of linear chromosomes and their dysfunction is believed to affect a wide range of cellular and/or organismal processes...
February 27, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28195879/fibrin-associated-ebv-positive-large-b-cell-lymphoma-an-indolent-neoplasm-with-features-distinct-from-diffuse-large-b-cell-lymphoma-associated-with-chronic-inflammation
#17
Daniel F Boyer, Penelope A McKelvie, Laurence de Leval, Kerstin L Edlefsen, Young-Hyeh Ko, Zachary A Aberman, Alexandra E Kovach, Aneal Masih, Ha T Nishino, Lawrence M Weiss, Alan K Meeker, Valentina Nardi, Maryknoll Palisoc, Lina Shao, Stefania Pittaluga, Judith A Ferry, Nancy Lee Harris, Aliyah R Sohani
Incidental cases of localized fibrin-associated Epstein-Barr virus (EBV)+ large B-cell proliferations have been described at unusual anatomic sites and have been included in the category of diffuse large B-cell lymphoma associated with chronic inflammation (DLBCL-CI) in the WHO Classification. We describe 12 cases and review the literature to define their clinicopathologic spectrum and compare features with typical cases of DLBCL-CI. Median age was 55.5 years with a M:F ratio of 3. In all 12 cases, the lymphoma was an incidental microscopic finding involving atrial myxomas (n=3), thrombi associated with endovascular grafts (n=3), chronic hematomas (n=2), and pseudocysts (n=4)...
March 2017: American Journal of Surgical Pathology
https://www.readbyqxmd.com/read/28152565/sphere-induced-rejuvenation-of-swine-and-human-m%C3%A3-ller-glia-is-primarily-caused-by-telomere-elongation
#18
Ni Xu, Yao Chen, Kevin C Dean, Xiaoqin Lu, Xiao Liu, Wei Wang, Douglas C Dean, Henry J Kaplan, Ling Gao, Fangtian Dong, Yongqing Liu
Müller cells are the major supportive and protective glial cells in the retina with important functions in histogenesis and synaptogenesis during development, and in maintenance of mature neurons as they show to secrete various cytokines and manifest potentials of self-renewal and transdifferentiation into retinal neurons following injury in the vertebrate retinas. The swine retina has a visual streak structure similar to the human macular where cone photoreceptors are highly concentrated, thereby can serve as a better model for studying retinal diseases and for formulating cell-based therapeutics than the rodent retinas...
February 2, 2017: Stem Cells
https://www.readbyqxmd.com/read/28115389/hypo-methylation-mediates-chromosomal-instability-in-pancreatic-net
#19
I Marinoni, A Wiederkeher, T Wiedmer, S Pantasis, A Di Domenico, R Frank, E Vassella, A Schmitt, A Perren
DAXX and or ATRX loss occur in 40% of pancreatic neuroendocrine tumors (PanNETs). PanNETs negative for DAXX or ATRX show an increased risk of relapse. The tumor-associated pathways activated upon DAXX or ATRX loss and how this event may induce chromosomal instability (CIN) and alternative lengthening telomeres (ALT) are still unknown. Both DAXX and ATRX are involved in DNA methylation regulation. DNA methylation of heterochromatin and of non-coding sequences is extremely important for the maintenance of genomic stability...
March 2017: Endocrine-related Cancer
https://www.readbyqxmd.com/read/28064387/the-role-of-histone-modifications-and-telomere-alterations-in-the-pathogenesis-of-diffuse-gliomas-in-adults-and-children
#20
REVIEW
Julieann Lee, David A Solomon, Tarik Tihan
Genetic profiling is an increasingly useful tool for sub-classification of gliomas in adults and children. Specific gene mutations, structural rearrangements, DNA methylation patterns, and gene expression profiles are now recognized to define molecular subgroups of gliomas that arise in distinct anatomic locations and patient age groups, and also provide a better prediction of clinical outcomes for glioma patients compared to histologic assessment alone. Understanding the role of these distinctive genetic alterations in gliomagenesis is also important for the development of potential targeted therapeutic interventions...
March 2017: Journal of Neuro-oncology
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