1
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Abbouche L, Bythell-Douglas R, Deans AJ. FANCM branchpoint translocase: Master of traverse, reverse and adverse DNA repair. DNA Repair (Amst) 2024; 140:103701. [PMID: 38878565 DOI: 10.1016/j.dnarep.2024.103701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 05/15/2024] [Accepted: 05/30/2024] [Indexed: 07/13/2024]
Abstract
FANCM is a multifunctional DNA repair enzyme that acts as a sensor and coordinator of replication stress responses, especially interstrand crosslink (ICL) repair mediated by the Fanconi anaemia (FA) pathway. Its specialised ability to bind and remodel branched DNA structures enables diverse genome maintenance activities. Through ATP-powered "branchpoint translocation", FANCM can promote fork reversal, facilitate replication traverse of ICLs, resolve deleterious R-loop structures, and restrain recombination. These remodelling functions also support a role as sensor of perturbed replication, eliciting checkpoint signalling and recruitment of downstream repair factors like the Fanconi anaemia FANCI:FANCD2 complex. Accordingly, FANCM deficiency causes chromosome fragility and cancer susceptibility. Other recent advances link FANCM to roles in gene editing efficiency and meiotic recombination, along with emerging synthetic lethal relationships, and targeting opportunities in ALT-positive cancers. Here we review key properties of FANCM's biochemical activities, with a particular focus on branchpoint translocation as a distinguishing characteristic.
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Affiliation(s)
- Lara Abbouche
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC, Australia; Department of Medicine (St Vincent's), University of Melbourne, Fitzroy, VIC, Australia
| | - Rohan Bythell-Douglas
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC, Australia
| | - Andrew J Deans
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC, Australia; Department of Medicine (St Vincent's), University of Melbourne, Fitzroy, VIC, Australia.
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2
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Panda S, Roychowdhury T, Dutta A, Chakraborty S, Das T, Chatterjee S. ALTering Cancer by Triggering Telomere Replication Stress through the Stabilization of Promoter G-Quadruplex in SMARCAL1. ACS Chem Biol 2024. [PMID: 38959478 DOI: 10.1021/acschembio.4c00285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2024]
Abstract
Most of the human cancers are dependent on telomerase to extend the telomeres. But ∼10% of all cancers use a telomerase-independent, homologous recombination mediated pathway called alternative lengthening of telomeres (ALT). Due to the poor prognosis, ALT status is not being considered yet in the diagnosis of cancer. No such specific treatment is available to date for ALT positive cancers. ALT positive cancers are dependent on replication stress to deploy DNA repair pathways to the telomeres to execute homologous recombination mediated telomere extension. SMARCAL1 (SWI/SNF related, matrix-associated, actin-dependent regulator of chromatin, subfamily A-like 1) is associated with the ALT telomeres to resolve replication stress thus providing telomere stability. Thus, the dependency on replication stress regulatory factors like SMARCAL1 made it a suitable therapeutic target for the treatment of ALT positive cancers. In this study, we found a significant downregulation of SMARCAL1 expression by stabilizing the G-quadruplex (G4) motif found in the promoter of SMARCAL1 by potent G4 stabilizers, like TMPyP4 and BRACO-19. SMARCAL1 downregulation led toward the increased localization of PML (promyelocytic leukemia) bodies in ALT telomeres and triggered the formation of APBs (ALT-associated promyelocytic leukemia bodies) in ALT positive cell lines, increasing telomere replication stress and DNA damage at a genomic level. Induction of replication stress and hyper-recombinogenic phenotype in ALT positive cells mediated by G4 stabilizing molecules already highlighted their possible application as a new therapeutic window to target ALT positive tumors. In accordance with this, our study will also provide a valuable insight toward the development of G4-based ALT therapeutics targeting SMARCAL1.
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Affiliation(s)
- Suman Panda
- Department of Biophysics, Bose Institute, EN 80, Sector V, Bidhan Nagar, Kolkata 700091 West Bengal, India
| | - Tanaya Roychowdhury
- Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, 1275 York Ave, New York, New York 10065, United States of America
| | - Anindya Dutta
- Department of Biophysics, Bose Institute, EN 80, Sector V, Bidhan Nagar, Kolkata 700091 West Bengal, India
| | - Sourio Chakraborty
- Division of Molecular Medicine, Centenary Campus, Bose Institute, P-1/12 C.I.T. Scheme VII-M, Kolkata 700054, India
| | - Tanya Das
- Division of Molecular Medicine, Centenary Campus, Bose Institute, P-1/12 C.I.T. Scheme VII-M, Kolkata 700054, India
| | - Subhrangsu Chatterjee
- Department of Biophysics, Bose Institute, EN 80, Sector V, Bidhan Nagar, Kolkata 700091 West Bengal, India
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3
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Gaela VM, Hsia HY, Joseph NA, Tzeng WY, Ting PC, Shen YL, Tsai CT, Boudier T, Chen LY. Orphan nuclear receptors-induced ALT-associated PML bodies are targets for ALT inhibition. Nucleic Acids Res 2024; 52:6472-6489. [PMID: 38752489 PMCID: PMC11194075 DOI: 10.1093/nar/gkae389] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2023] [Revised: 04/23/2024] [Accepted: 05/08/2024] [Indexed: 06/25/2024] Open
Abstract
Orphan nuclear receptors (NRs), such as COUP-TF1, COUP-TF2, EAR2, TR2 and TR4, are implicated in telomerase-negative cancers that maintain their telomeres through the alternative lengthening of telomeres (ALT) mechanism. However, how telomere association of orphan NRs is involved in ALT activation remains unclear. Here, we demonstrate that telomeric tethering of orphan NRs in human fibroblasts initiates formation of ALT-associated PML bodies (APBs) and features of ALT activity, including ALT telomere DNA synthesis, telomere sister chromatid exchange, and telomeric C-circle generation, suggesting de novo ALT induction. Overexpression of orphan NRs exacerbates ALT phenotypes in ALT cells, while their depletion limits ALT. Orphan NRs initiate ALT via the zinc finger protein 827, suggesting the involvement of chromatin structure alterations for ALT activation. Furthermore, we found that orphan NRs and deficiency of the ALT suppressor ATRX-DAXX complex operate in concert to promote ALT activation. Moreover, PML depletion by gene knockout or arsenic trioxide treatment inhibited ALT induction in fibroblasts and ALT cancer cells, suggesting that APB formation underlies the orphan NR-induced ALT activation. Importantly, arsenic trioxide administration abolished APB formation and features of ALT activity in ALT cancer cell line-derived mouse xenografts, suggesting its potential for further therapeutic development to treat ALT cancers.
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Affiliation(s)
- Venus Marie Gaela
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 11529, Taiwan
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Hsuan-Yu Hsia
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Nithila A Joseph
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Wan-Yi Tzeng
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
- Insitute of Molecular and Cellular Biology, National Taiwan University, Taipei 106319, Taiwan
| | - Pin-Chao Ting
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
- Department and Graduate Institute of Microbiology and Immunology, National Defense Medical Center, Taipei 11490, Taiwan
| | - Yi-Ling Shen
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Chia-Tsen Tsai
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 11529, Taiwan
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Thomas Boudier
- CENTURI multi-engineering platform, Aix-Marseille Université, Marseille 13288, France
| | - Liuh-Yow Chen
- Molecular and Cell Biology, Taiwan International Graduate Program, Academia Sinica and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 11529, Taiwan
- Institute of Molecular Biology, Academia Sinica, Taipei 11529, Taiwan
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4
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Waitkus MS, Erman EN, Reitman ZJ, Ashley DM. Mechanisms of telomere maintenance and associated therapeutic vulnerabilities in malignant gliomas. Neuro Oncol 2024; 26:1012-1024. [PMID: 38285162 PMCID: PMC11145458 DOI: 10.1093/neuonc/noae016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Indexed: 01/30/2024] Open
Abstract
A majority of cancers (~85%) activate the enzyme telomerase to maintain telomere length over multiple rounds of cellular division. Telomerase-negative cancers activate a distinct, telomerase-independent mechanism of telomere maintenance termed alternative lengthening of telomeres (ALT). ALT uses homologous recombination to maintain telomere length and exhibits features of break-induced DNA replication. In malignant gliomas, the activation of either telomerase or ALT is nearly ubiquitous in pediatric and adult tumors, and the frequency with which these distinct telomere maintenance mechanisms (TMMs) is activated varies according to genetically defined glioma subtypes. In this review, we summarize the current state of the field of TMMs and their relevance to glioma biology and therapy. We review the genetic alterations and molecular mechanisms leading to telomerase activation or ALT induction in pediatric and adult gliomas. With this background, we review emerging evidence on strategies for targeting TMMs for glioma therapy. Finally, we comment on critical gaps and issues for moving the field forward to translate our improved understanding of glioma telomere maintenance into better therapeutic strategies for patients.
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Affiliation(s)
- Matthew S Waitkus
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
| | - Elise N Erman
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
| | - Zachary J Reitman
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina, USA
| | - David M Ashley
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
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5
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Yates M, Marois I, St-Hilaire E, Ronato DA, Djerir B, Brochu C, Morin T, Hammond-Martel I, Gezzar-Dandashi S, Casimir L, Drobetsky E, Cappadocia L, Masson JY, Wurtele H, Maréchal A. SMARCAL1 ubiquitylation controls its association with RPA-coated ssDNA and promotes replication fork stability. PLoS Biol 2024; 22:e3002552. [PMID: 38502677 PMCID: PMC10950228 DOI: 10.1371/journal.pbio.3002552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 02/19/2024] [Indexed: 03/21/2024] Open
Abstract
Impediments in replication fork progression cause genomic instability, mutagenesis, and severe pathologies. At stalled forks, RPA-coated single-stranded DNA (ssDNA) activates the ATR kinase and directs fork remodeling, 2 key early events of the replication stress response. RFWD3, a recently described Fanconi anemia (FA) ubiquitin ligase, associates with RPA and promotes its ubiquitylation, facilitating late steps of homologous recombination (HR). Intriguingly, RFWD3 also regulates fork progression, restart and stability via poorly understood mechanisms. Here, we used proteomics to identify putative RFWD3 substrates during replication stress in human cells. We show that RFWD3 interacts with and ubiquitylates the SMARCAL1 DNA translocase directly in vitro and following DNA damage in vivo. SMARCAL1 ubiquitylation does not trigger its subsequent proteasomal degradation but instead disengages it from RPA thereby regulating its function at replication forks. Proper regulation of SMARCAL1 by RFWD3 at stalled forks protects them from excessive MUS81-mediated cleavage in response to UV irradiation, thereby limiting DNA replication stress. Collectively, our results identify RFWD3-mediated SMARCAL1 ubiquitylation as a novel mechanism that modulates fork remodeling to avoid genome instability triggered by aberrant fork processing.
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Affiliation(s)
- Maïlyn Yates
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | - Isabelle Marois
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | - Edlie St-Hilaire
- Research Center, Maisonneuve-Rosemont Hospital, Montréal, Canada
| | - Daryl A. Ronato
- Genome Stability Laboratory, CHU de Québec Research Center, Oncology Division; Department of Molecular Biology, Medical Biochemistry and Pathology; Laval University Cancer Research Center, Québec City, Canada
| | - Billel Djerir
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | - Chloé Brochu
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | - Théo Morin
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | | | | | - Lisa Casimir
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
| | - Elliot Drobetsky
- Research Center, Maisonneuve-Rosemont Hospital, Montréal, Canada
- Medicine Department, Université de Montréal, Montréal, Canada
| | - Laurent Cappadocia
- Faculty of Sciences, Department of Chemistry, Université du Québec à Montréal, Montréal, Canada
| | - Jean-Yves Masson
- Genome Stability Laboratory, CHU de Québec Research Center, Oncology Division; Department of Molecular Biology, Medical Biochemistry and Pathology; Laval University Cancer Research Center, Québec City, Canada
| | - Hugo Wurtele
- Research Center, Maisonneuve-Rosemont Hospital, Montréal, Canada
- Medicine Department, Université de Montréal, Montréal, Canada
| | - Alexandre Maréchal
- Faculty of Sciences, Department of Biology, Université de Sherbrooke, Sherbrooke, Canada
- CHUS Research Center and Cancer Research Institute, Sherbrooke, Canada
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6
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Leuzzi G, Vasciaveo A, Taglialatela A, Chen X, Firestone TM, Hickman AR, Mao W, Thakar T, Vaitsiankova A, Huang JW, Cuella-Martin R, Hayward SB, Kesner JS, Ghasemzadeh A, Nambiar TS, Ho P, Rialdi A, Hebrard M, Li Y, Gao J, Gopinath S, Adeleke OA, Venters BJ, Drake CG, Baer R, Izar B, Guccione E, Keogh MC, Guerois R, Sun L, Lu C, Califano A, Ciccia A. SMARCAL1 is a dual regulator of innate immune signaling and PD-L1 expression that promotes tumor immune evasion. Cell 2024; 187:861-881.e32. [PMID: 38301646 PMCID: PMC10980358 DOI: 10.1016/j.cell.2024.01.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 07/23/2023] [Accepted: 01/05/2024] [Indexed: 02/03/2024]
Abstract
Genomic instability can trigger cancer-intrinsic innate immune responses that promote tumor rejection. However, cancer cells often evade these responses by overexpressing immune checkpoint regulators, such as PD-L1. Here, we identify the SNF2-family DNA translocase SMARCAL1 as a factor that favors tumor immune evasion by a dual mechanism involving both the suppression of innate immune signaling and the induction of PD-L1-mediated immune checkpoint responses. Mechanistically, SMARCAL1 limits endogenous DNA damage, thereby suppressing cGAS-STING-dependent signaling during cancer cell growth. Simultaneously, it cooperates with the AP-1 family member JUN to maintain chromatin accessibility at a PD-L1 transcriptional regulatory element, thereby promoting PD-L1 expression in cancer cells. SMARCAL1 loss hinders the ability of tumor cells to induce PD-L1 in response to genomic instability, enhances anti-tumor immune responses and sensitizes tumors to immune checkpoint blockade in a mouse melanoma model. Collectively, these studies uncover SMARCAL1 as a promising target for cancer immunotherapy.
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Affiliation(s)
- Giuseppe Leuzzi
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Alessandro Vasciaveo
- Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Systems Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Angelo Taglialatela
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Xiao Chen
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | | | | | - Wendy Mao
- Columbia Center for Translational Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Tanay Thakar
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Alina Vaitsiankova
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Jen-Wei Huang
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Raquel Cuella-Martin
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Samuel B Hayward
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Jordan S Kesner
- Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Systems Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Ali Ghasemzadeh
- Columbia Center for Translational Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Tarun S Nambiar
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Patricia Ho
- Columbia Center for Translational Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Medicine, Division of Hematology and Oncology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Alexander Rialdi
- Center for OncoGenomics and Innovative Therapeutics (COGIT), Center for Therapeutics Discovery, Department of Oncological Sciences and Pharmacological Sciences, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | - Maxime Hebrard
- Institute of Molecular and Cell Biology (IMCB), Agency for Science, Technology and Research (ASTAR), Singapore, Singapore
| | - Yinglu Li
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Jinmei Gao
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | | | | | | | - Charles G Drake
- Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA; Columbia Center for Translational Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Urology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Richard Baer
- Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA; Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Benjamin Izar
- Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Systems Biology, Columbia University Irving Medical Center, New York, NY 10032, USA; Columbia Center for Translational Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Medicine, Division of Hematology and Oncology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Ernesto Guccione
- Center for OncoGenomics and Innovative Therapeutics (COGIT), Center for Therapeutics Discovery, Department of Oncological Sciences and Pharmacological Sciences, Tisch Cancer Institute, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | | | - Raphael Guerois
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), 91198 Gif-sur-Yvette, France
| | - Lu Sun
- EpiCypher Inc., Durham, NC 27709, USA
| | - Chao Lu
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Andrea Califano
- Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Systems Biology, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Biochemistry and Molecular Biophysics, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Biomedical Informatics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Alberto Ciccia
- Department of Genetics and Development, Columbia University Irving Medical Center, New York, NY 10032, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY 10032, USA; Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA.
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7
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Mori JO, Keegan J, Flynn RL, Heaphy CM. Alternative lengthening of telomeres: mechanism and the pathogenesis of cancer. J Clin Pathol 2024; 77:82-86. [PMID: 37890990 DOI: 10.1136/jcp-2023-209005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 10/12/2023] [Indexed: 10/29/2023]
Abstract
Telomere maintenance and elongation allows cells to gain replicative immortality and evade cellular senescence during cancer development. While most cancers use telomerase to maintain telomere lengths, a subset of cancers engage the alternative lengthening of telomeres (ALT) pathway for telomere maintenance. ALT is present in 5%-10% of all cancers, although the prevalence is dramatically higher in certain cancer types, including complex karyotype sarcomas, isocitrate dehydrogenase-mutant astrocytoma (WHO grade II-IV), pancreatic neuroendocrine tumours, neuroblastoma and chromophobe hepatocellular carcinomas. ALT is maintained through a homology-directed DNA repair mechanism. Resembling break-induced replication, this aberrant process results in dramatic cell-to-cell telomere length heterogeneity, widespread chromosomal instability and chronic replication stress. Additionally, ALT-positive cancers frequently harbour inactivating mutations in either chromatin remodelling proteins (ATRX, DAXX and H3F3A) or DNA damage repair factors (SMARCAL1 and SLX4IP). ALT can readily be detected in tissue by assessing the presence of unique molecular characteristics, such as large ultrabright nuclear telomeric foci or partially single-stranded telomeric DNA circles (C-circles). Importantly, ALT has been validated as a robust diagnostic and prognostic biomarker for certain cancer types and may even be exploited as a therapeutic target via small molecular inhibitors and/or synthetic lethality approaches.
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Affiliation(s)
- Joakin O Mori
- Medicine, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA
| | - Joshua Keegan
- Pharmacology, Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA
| | - Rachel L Flynn
- Medicine, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA
- Pharmacology, Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA
| | - Christopher M Heaphy
- Medicine, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, USA
- Pathology and Laboratory Medicine, Boston Medical Center, Boston, Massachusetts, USA
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8
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Spegg V, Altmeyer M. Genome maintenance meets mechanobiology. Chromosoma 2024; 133:15-36. [PMID: 37581649 PMCID: PMC10904543 DOI: 10.1007/s00412-023-00807-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/20/2023] [Accepted: 07/26/2023] [Indexed: 08/16/2023]
Abstract
Genome stability is key for healthy cells in healthy organisms, and deregulated maintenance of genome integrity is a hallmark of aging and of age-associated diseases including cancer and neurodegeneration. To maintain a stable genome, genome surveillance and repair pathways are closely intertwined with cell cycle regulation and with DNA transactions that occur during transcription and DNA replication. Coordination of these processes across different time and length scales involves dynamic changes of chromatin topology, clustering of fragile genomic regions and repair factors into nuclear repair centers, mobilization of the nuclear cytoskeleton, and activation of cell cycle checkpoints. Here, we provide a general overview of cell cycle regulation and of the processes involved in genome duplication in human cells, followed by an introduction to replication stress and to the cellular responses elicited by perturbed DNA synthesis. We discuss fragile genomic regions that experience high levels of replication stress, with a particular focus on telomere fragility caused by replication stress at the ends of linear chromosomes. Using alternative lengthening of telomeres (ALT) in cancer cells and ALT-associated PML bodies (APBs) as examples of replication stress-associated clustered DNA damage, we discuss compartmentalization of DNA repair reactions and the role of protein properties implicated in phase separation. Finally, we highlight emerging connections between DNA repair and mechanobiology and discuss how biomolecular condensates, components of the nuclear cytoskeleton, and interfaces between membrane-bound organelles and membraneless macromolecular condensates may cooperate to coordinate genome maintenance in space and time.
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Affiliation(s)
- Vincent Spegg
- Department of Molecular Mechanisms of Disease, University of Zurich, Zurich, Switzerland
| | - Matthias Altmeyer
- Department of Molecular Mechanisms of Disease, University of Zurich, Zurich, Switzerland.
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9
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Rosso I, Jones-Weinert C, Rossiello F, Cabrini M, Brambillasca S, Munoz-Sagredo L, Lavagnino Z, Martini E, Tedone E, Garre' M, Aguado J, Parazzoli D, Mione M, Shay JW, Mercurio C, d'Adda di Fagagna F. Alternative lengthening of telomeres (ALT) cells viability is dependent on C-rich telomeric RNAs. Nat Commun 2023; 14:7086. [PMID: 37925537 PMCID: PMC10625592 DOI: 10.1038/s41467-023-42831-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 10/23/2023] [Indexed: 11/06/2023] Open
Abstract
Alternative lengthening of telomeres (ALT) is a telomere maintenance mechanism activated in ~10-15% of cancers, characterized by telomeric damage. Telomeric damage-induced long non-coding RNAs (dilncRNAs) are transcribed at dysfunctional telomeres and contribute to telomeric DNA damage response (DDR) activation and repair. Here we observed that telomeric dilncRNAs are preferentially elevated in ALT cells. Inhibition of C-rich (teloC) dilncRNAs with antisense oligonucleotides leads to DNA replication stress responses, increased genomic instability, and apoptosis induction selectively in ALT cells. Cell death is dependent on DNA replication and is increased by DNA replication stress. Mechanistically, teloC dilncRNA inhibition reduces RAD51 and 53BP1 recruitment to telomeres, boosts the engagement of BIR machinery, and increases C-circles and telomeric sister chromatid exchanges, without increasing telomeric non-S phase synthesis. These results indicate that teloC dilncRNA is necessary for a coordinated recruitment of DDR factors to ALT telomeres and it is essential for ALT cancer cells survival.
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Affiliation(s)
- Ilaria Rosso
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Corey Jones-Weinert
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- The Salk Institute for Biological Studies, La Jolla, CA, USA
| | | | - Matteo Cabrini
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Silvia Brambillasca
- IFOM ETS - The AIRC Institute of Molecular Oncology (Experimental Therapeutics Program), Milan, Italy
| | - Leonel Munoz-Sagredo
- Institute of Biological and Chemical Systems - Functional Molecular Systems (IBCS-FMS), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
- School of Medicine, Universidad de Valparaiso, Valparaiso, Chile
| | - Zeno Lavagnino
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Emanuele Martini
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- Dipartimento di Oncologia ed Emato-Oncologia, Università degli Studi di Milano, Milan, Italy
| | - Enzo Tedone
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Massimiliano Garre'
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- RCSI, Royal College of Surgeons in Ireland, Department of Chemistry, Dublin, Ireland
| | - Julio Aguado
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, St Lucia, QLD, Australia
| | - Dario Parazzoli
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy
| | - Marina Mione
- Department of Cellular, Computational and Integrative Biology - CIBIO, University of Trento, Trento, Italy
| | - Jerry W Shay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Ciro Mercurio
- IFOM ETS - The AIRC Institute of Molecular Oncology (Experimental Therapeutics Program), Milan, Italy
| | - Fabrizio d'Adda di Fagagna
- IFOM ETS - The AIRC Institute of Molecular Oncology, Milan, Italy.
- Institute of Molecular Genetics IGM-CNR "Luigi Luca Cavalli-Sforza", Pavia, Italy.
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10
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Loe TK, Lazzerini Denchi E, Tricola GM, Azeroglu B. ALTercations at telomeres: stress, recombination and extrachromosomal affairs. Biochem Soc Trans 2023; 51:1935-1946. [PMID: 37767563 DOI: 10.1042/bst20230265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 09/21/2023] [Accepted: 09/22/2023] [Indexed: 09/29/2023]
Abstract
Approximately 15% of human cancers depend on the alternative lengthening of telomeres (ALT) pathway to maintain telomeres and proliferate. Telomeres that are elongated using ALT display unique features raising the exciting prospect of tailored cancer therapies. ALT-mediated telomere elongation shares several features with recombination-based DNA repair. Strikingly, cells that use the ALT pathway display abnormal levels of replication stress at telomeres and accumulate abundant extrachromosomal telomeric DNA. In this review, we examine recent findings that shed light on the ALT mechanisms and the strategies currently available to suppress this telomere elongation mechanism.
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Affiliation(s)
- Taylor K Loe
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, U.S.A
| | - Eros Lazzerini Denchi
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, U.S.A
| | - Gianna M Tricola
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, U.S.A
| | - Benura Azeroglu
- Laboratory of Genome Integrity, National Cancer Institute, NIH, Bethesda, MD 20892, U.S.A
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11
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Liu H, Xu C, Diplas BH, Brown A, Strickland LM, Yao H, Ling J, McLendon RE, Keir ST, Ashley DM, He Y, Waitkus MS. Cancer-associated SMARCAL1 loss-of-function mutations promote alternative lengthening of telomeres and tumorigenesis in telomerase-negative glioblastoma cells. Neuro Oncol 2023; 25:1563-1575. [PMID: 36689342 PMCID: PMC10484176 DOI: 10.1093/neuonc/noad022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Telomere maintenance mechanisms are required to enable the replicative immortality of malignant cells. While most cancers activate the enzyme telomerase, a subset of cancers uses telomerase-independent mechanisms termed alternative lengthening of telomeres (ALT). ALT occurs via homology-directed-repair mechanisms and is frequently associated with ATRX mutations. We previously showed that a subset of adult glioblastoma (GBM) patients with ATRX-expressing ALT-positive tumors harbored loss-of-function mutations in the SMARCAL1 gene, which encodes an annealing helicase involved in replication fork remodeling and the resolution of replication stress. However, the causative relationship between SMARCAL1 deficiency, tumorigenesis, and de novo telomere synthesis is not understood. METHODS We used a patient-derived ALT-positive GBM cell line with native SMARCAL1 deficiency to investigate the role of SMARCAL1 in ALT-mediated de novo telomere synthesis, replication stress, and gliomagenesis in vivo. RESULTS Inducible rescue of SMARCAL1 expression suppresses ALT indicators and inhibits de novo telomere synthesis in GBM and osteosarcoma cells, suggesting that SMARCAL1 deficiency plays a functional role in ALT induction in cancers that natively lack SMARCAL1 function. SMARCAL1-deficient ALT-positive cells can be serially propagated in vivo in the absence of detectable telomerase activity, demonstrating that the SMARCAL1-deficient ALT phenotype maintains telomeres in a manner that promotes tumorigenesis. CONCLUSIONS SMARCAL1 deficiency is permissive to ALT and promotes gliomagenesis. Inducible rescue of SMARCAL1 in ALT-positive cell lines permits the dynamic modulation of ALT activity, which will be valuable for future studies aimed at understanding the mechanisms of ALT and identifying novel anticancer therapeutics that target the ALT phenotype.
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Affiliation(s)
- Heng Liu
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Cheng Xu
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Bill H Diplas
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Alexandrea Brown
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
| | - Laura M Strickland
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
| | - Haipei Yao
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Jinjie Ling
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Roger E McLendon
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Stephen T Keir
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
| | - David M Ashley
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
| | - Yiping He
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Pathology, Duke University Medical Center, Durham, North Carolina, USA
| | - Matthew S Waitkus
- The Preston Robert Tisch Brain Tumor Center, Duke University Medical Center, Durham, North Carolina, USA
- Department of Neurosurgery, Duke University Medical Center, Durham, North Carolina, USA
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12
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Reiss M, Keegan J, Aldrich A, Lyons SM, Flynn RL. The exoribonuclease XRN2 mediates degradation of the long non-coding telomeric RNA TERRA. FEBS Lett 2023; 597:1818-1836. [PMID: 37191774 PMCID: PMC10524182 DOI: 10.1002/1873-3468.14639] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2023] [Revised: 05/01/2023] [Accepted: 05/05/2023] [Indexed: 05/17/2023]
Abstract
The telomeric repeat-containing RNA, TERRA, associates with both telomeric DNA and telomeric proteins, often forming RNA:DNA hybrids (R-loops). TERRA is most abundant in cancer cells utilizing the alternative lengthening of telomeres (ALT) pathway for telomere maintenance, suggesting that persistent TERRA R-loops may contribute to activation of the ALT mechanism. Therefore, we sought to identify the enzyme(s) that regulate TERRA metabolism in mammalian cells. Here, we identify that the 5'-3' exoribonuclease XRN2 regulates the stability of TERRA RNA. Moreover, while stabilization of TERRA alone was insufficient to drive ALT, depletion of XRN2 in ALT-positive cells led to a significant increase in TERRA R-loops and exacerbated ALT activity. Together, our findings highlight XRN2 as a key determinant of TERRA metabolism and telomere stability in cancer cells that rely on the ALT pathway.
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Affiliation(s)
- Matthew Reiss
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University Chobanian & Avedisian School of Medicine, Boston, MA 02118, USA
| | - Joshua Keegan
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University Chobanian & Avedisian School of Medicine, Boston, MA 02118, USA
| | - Anne Aldrich
- Departments of Biochemistry and Cell Biology, Boston University Chobanian & Avedisian School of Medicine, Boston, MA 02118, USA
| | - Shawn M. Lyons
- Departments of Biochemistry and Cell Biology, Boston University Chobanian & Avedisian School of Medicine, Boston, MA 02118, USA
| | - Rachel Litman Flynn
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University Chobanian & Avedisian School of Medicine, Boston, MA 02118, USA
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13
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Carson LM, Flynn RL. Highlighting vulnerabilities in the alternative lengthening of telomeres pathway. Curr Opin Pharmacol 2023; 70:102380. [PMID: 37149932 PMCID: PMC10247456 DOI: 10.1016/j.coph.2023.102380] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 02/03/2023] [Accepted: 03/28/2023] [Indexed: 05/09/2023]
Abstract
The alternative lengthening of telomeres (ALT) pathway is a telomere elongation mechanism found in a small but often aggressive subset of cancers. Dependent on break-induced replication, telomere extension in ALT-positive cells relies on a baseline level of DNA replication stress to initiate elongation events. This results in an elevated level of DNA damage and presents a possible vulnerability to be exploited in the development of ALT-targeted cancer therapies. Currently, there are no treatment options that target the ALT mechanism or that are specific for ALT-positive tumors. Here, we review recent developments and promising directions in the development of ALT-targeted therapeutics, many of which involve tipping the balance towards inhibition or exacerbation of ALT activity to selectively target these cells.
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Affiliation(s)
- Lisa M Carson
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University School of Medicine, Boston, MA, 02118, USA
| | - Rachel L Flynn
- Departments of Pharmacology and Experimental Therapeutics, and Medicine, Cancer Center, Boston University School of Medicine, Boston, MA, 02118, USA.
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14
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Asada H, Tani A, Sakuma H, Hirabayashi M, Matsumoto Y, Watanabe K, Tsuboi M, Yoshida S, Harada K, Uchikai T, Goto-Koshino Y, Chambers JK, Ishihara G, Kobayashi T, Irie M, Uchida K, Ohno K, Bonkobara M, Tsujimoto H, Tomiyasu H. Whole exome and transcriptome analysis revealed the activation of ERK and Akt signaling pathway in canine histiocytic sarcoma. Sci Rep 2023; 13:8512. [PMID: 37231193 DOI: 10.1038/s41598-023-35813-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 05/24/2023] [Indexed: 05/27/2023] Open
Abstract
Histiocytic sarcoma (HS) is an incurable aggressive tumor, and no consensus has been made on the treatment due to its rare occurrence. Since dogs spontaneously develop the disease and several cell lines are available, they have been advocated as translational animal models. In the present study, therefore, we explored gene mutations and aberrant molecular pathways in canine HS by next generation sequencing to identify molecular targets for treatment. Whole exome sequencing and RNA-sequencing revealed gene mutations related to receptor tyrosine kinase pathways and activation of ERK1/2, PI3K-AKT, and STAT3 pathways. Analysis by quantitative PCR and immunohistochemistry revealed that fibroblast growth factor receptor 1 (FGFR1) is over-expressed. Moreover, activation of ERK and Akt signaling were confirmed in all HS cell lines, and FGFR1 inhibitors showed dose-dependent growth inhibitory effects in two of the twelve canine HS cell lines. The findings obtained in the present study indicated that ERK and Akt signaling were activated in canine HS and drugs targeting FGFR1 might be effective in part of the cases. The present study provides translational evidence that leads to establishment of novel therapeutic strategies targeting ERK and Akt signaling in HS patients.
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Affiliation(s)
- Hajime Asada
- Department of Veterinary Internal Medicine, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
- Department of Obstetrics and Gynecology, The University of Chicago, Chicago, IL, 60637, USA
| | - Akiyoshi Tani
- Department of Veterinary Internal Medicine, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Hiroki Sakuma
- Department of Veterinary Internal Medicine, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Miyuki Hirabayashi
- Department of Veterinary Pathology, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Yuki Matsumoto
- Anicom Specialty Medical Institute Inc., Shinjuku-ku, Tokyo, Japan
| | - Kei Watanabe
- Anicom Specialty Medical Institute Inc., Shinjuku-ku, Tokyo, Japan
| | - Masaya Tsuboi
- Veterinary Medical Center, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Shino Yoshida
- Department of Veterinary Internal Medicine, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Kei Harada
- Japan Small Animal Cancer Center, Tokorozawa, Saitama, Japan
| | - Takao Uchikai
- Anicom Specialty Medical Institute Inc., Shinjuku-ku, Tokyo, Japan
| | - Yuko Goto-Koshino
- Department of Veterinary Internal Medicine, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - James K Chambers
- Department of Veterinary Pathology, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Genki Ishihara
- Anicom Specialty Medical Institute Inc., Shinjuku-ku, Tokyo, Japan
| | | | - Mitsuhiro Irie
- Shikoku Veterinary Medical Center, Kita-gun, Kagawa, Japan
| | - Kazuyuki Uchida
- Department of Veterinary Pathology, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Koichi Ohno
- Department of Veterinary Internal Medicine, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Makoto Bonkobara
- Department of Veterinary Clinical Pathology, Nippon Veterinary and Life Science University, Musashino, Tokyo, Japan
| | - Hajime Tsujimoto
- Department of Veterinary Internal Medicine, the University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Hirotaka Tomiyasu
- Department of Veterinary Internal Medicine, the University of Tokyo, Bunkyo-ku, Tokyo, Japan.
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15
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Broderick R, Cherdyntseva V, Nieminuszczy J, Dragona E, Kyriakaki M, Evmorfopoulou T, Gagos S, Niedzwiedz W. Pathway choice in the alternative telomere lengthening in neoplasia is dictated by replication fork processing mediated by EXD2's nuclease activity. Nat Commun 2023; 14:2428. [PMID: 37105990 PMCID: PMC10140042 DOI: 10.1038/s41467-023-38029-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 04/12/2023] [Indexed: 04/29/2023] Open
Abstract
Telomerase-independent cancer proliferation via the alternative lengthening of telomeres (ALT) relies upon two distinct, largely uncharacterized, break-induced-replication (BIR) processes. How cancer cells initiate and regulate these terminal repair mechanisms is unknown. Here, we establish that the EXD2 nuclease is recruited to ALT telomeres to direct their maintenance. We demonstrate that EXD2 loss leads to telomere shortening, elevated telomeric sister chromatid exchanges, C-circle formation as well as BIR-mediated telomeric replication. We discover that EXD2 fork-processing activity triggers a switch between RAD52-dependent and -independent ALT-associated BIR. The latter is suppressed by EXD2 but depends specifically on the fork remodeler SMARCAL1 and the MUS81 nuclease. Thus, our findings suggest that processing of stalled replication forks orchestrates elongation pathway choice at ALT telomeres. Finally, we show that co-depletion of EXD2 with BLM, DNA2 or POLD3 confers synthetic lethality in ALT cells, identifying EXD2 as a potential druggable target for ALT-reliant cancers.
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Affiliation(s)
| | - Veronica Cherdyntseva
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | | | - Eleni Dragona
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | - Maria Kyriakaki
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | - Theodora Evmorfopoulou
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece
| | - Sarantis Gagos
- Laboratory of Genetics, Center of Clinical Research, Experimental Surgery and Translational Research Biomedical Research Foundation Academy of Athens (BRFAA), Athens, Greece.
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16
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Rai R, Biju K, Sun W, Sodeinde T, Al-Hiyasat A, Morgan J, Ye X, Li X, Chen Y, Chang S. Homology directed telomere clustering, ultrabright telomere formation and nuclear envelope rupture in cells lacking TRF2 B and RAP1. Nat Commun 2023; 14:2144. [PMID: 37059728 PMCID: PMC10104862 DOI: 10.1038/s41467-023-37761-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 03/30/2023] [Indexed: 04/16/2023] Open
Abstract
Double-strand breaks (DSBs) due to genotoxic stress represent potential threats to genome stability. Dysfunctional telomeres are recognized as DSBs and are repaired by distinct DNA repair mechanisms. RAP1 and TRF2 are telomere binding proteins essential to protect telomeres from engaging in homology directed repair (HDR), but how this occurs remains unclear. In this study, we examined how the basic domain of TRF2 (TRF2B) and RAP1 cooperate to repress HDR at telomeres. Telomeres lacking TRF2B and RAP1 cluster into structures termed ultrabright telomeres (UTs). HDR factors localize to UTs, and UT formation is abolished by RNaseH1, DDX21 and ADAR1p110, suggesting that they contain DNA-RNA hybrids. Interaction between the BRCT domain of RAP1 and KU70/KU80 is also required to repress UT formation. Expressing TRF2∆B in Rap1-/- cells resulted in aberrant lamin A localization in the nuclear envelope and dramatically increased UT formation. Expressing lamin A phosphomimetic mutants induced nuclear envelope rupturing and aberrant HDR-mediated UT formation. Our results highlight the importance of shelterin and proteins in the nuclear envelope in repressing aberrant telomere-telomere recombination to maintain telomere homeostasis.
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Affiliation(s)
- Rekha Rai
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA.
| | - Kevin Biju
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA
- Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
| | - Wenqi Sun
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Tori Sodeinde
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA
| | - Amer Al-Hiyasat
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA
| | - Jaida Morgan
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA
| | - Xianwen Ye
- University of Chinese Academy of Sciences, 100049, Beijing, China
- School of Life Science and Technology, ShanghaiTech University, 100 Haike Road, Shanghai, 201210, China
| | - Xueqing Li
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Yong Chen
- State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
- School of Life Science and Technology, ShanghaiTech University, 100 Haike Road, Shanghai, 201210, China
| | - Sandy Chang
- Department of Laboratory Medicine, Yale University School of Medicine, New Haven, 330 Cedar Street, CT, 06520, USA.
- Department of Pathology, Yale University School of Medicine, 330 Cedar Street, New Haven, CT, 06520, USA.
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, 330 Cedar Street, New Haven, CT, 06520, USA.
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17
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Kusuma FK, Prabhu A, Tieo G, Ahmed SM, Dakle P, Yong WK, Pathak E, Madan V, Jiang YY, Tam WL, Kappei D, Dröge P, Koeffler HP, Jeitany M. Signalling inhibition by ponatinib disrupts productive alternative lengthening of telomeres (ALT). Nat Commun 2023; 14:1919. [PMID: 37024489 PMCID: PMC10079688 DOI: 10.1038/s41467-023-37633-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Accepted: 03/24/2023] [Indexed: 04/08/2023] Open
Abstract
Alternative lengthening of telomeres (ALT) supports telomere maintenance in 10-15% of cancers, thus representing a compelling target for therapy. By performing anti-cancer compound library screen on isogenic cell lines and using extrachromosomal telomeric C-circles, as a bona fide marker of ALT activity, we identify a receptor tyrosine kinase inhibitor ponatinib that deregulates ALT mechanisms, induces telomeric dysfunction, reduced ALT-associated telomere synthesis, and targets, in vivo, ALT-positive cells. Using RNA-sequencing and quantitative phosphoproteomic analyses, combined with C-circle level assessment, we find an ABL1-JNK-JUN signalling circuit to be inhibited by ponatinib and to have a role in suppressing telomeric C-circles. Furthermore, transcriptome and interactome analyses suggest a role of JUN in DNA damage repair. These results are corroborated by synergistic drug interactions between ponatinib and either DNA synthesis or repair inhibitors, such as triciribine. Taken together, we describe here a signalling pathway impacting ALT which can be targeted by a clinically approved drug.
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Affiliation(s)
- Frances Karla Kusuma
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Aishvaryaa Prabhu
- Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore
| | - Galen Tieo
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Syed Moiz Ahmed
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Pushkar Dakle
- Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore
| | - Wai Khang Yong
- Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Elina Pathak
- Genome Institute of Singapore, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Vikas Madan
- Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore
| | - Yan Yi Jiang
- Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore
- Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, P. R. China
| | - Wai Leong Tam
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- Genome Institute of Singapore, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Dennis Kappei
- Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
- NUS Center for Cancer Research, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| | - Peter Dröge
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - H Phillip Koeffler
- Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore
- Cedars-Sinai Medical Center, Division of Hematology/Oncology, UCLA School of Medicine, Los Angeles, CA, USA
- Department of Hematology-Oncology, National University Cancer Institute of Singapore (NCIS), National University Hospital, Singapore, Singapore
| | - Maya Jeitany
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
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18
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Sohn EJ, Goralsky JA, Shay JW, Min J. The Molecular Mechanisms and Therapeutic Prospects of Alternative Lengthening of Telomeres (ALT). Cancers (Basel) 2023; 15:cancers15071945. [PMID: 37046606 PMCID: PMC10093677 DOI: 10.3390/cancers15071945] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 03/14/2023] [Accepted: 03/15/2023] [Indexed: 04/14/2023] Open
Abstract
As detailed by the end replication problem, the linear ends of a cell's chromosomes, known as telomeres, shorten with each successive round of replication until a cell enters into a state of growth arrest referred to as senescence. To maintain their immortal proliferation capacity, cancer cells must employ a telomere maintenance mechanism, such as telomerase activation or the Alternative Lengthening of Telomeres pathway (ALT). With only 10-15% of cancers utilizing the ALT mechanism, progress towards understanding its molecular components and associated hallmarks has only recently been made. This review analyzes the advances towards understanding the ALT pathway by: (1) detailing the mechanisms associated with engaging the ALT pathway as well as (2) identifying potential therapeutic targets of ALT that may lead to novel cancer therapeutic treatments. Collectively, these studies indicate that the ALT molecular mechanisms involve at least two distinct pathways induced by replication stress and damage at telomeres. We suggest exploiting tumor dependency on ALT is a promising field of study because it suggests new approaches to ALT-specific therapies for cancers with poorer prognosis. While substantial progress has been made in the ALT research field, additional progress will be required to realize these advances into clinical practices to treat ALT cancers and improve patient prognoses.
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Affiliation(s)
- Eric J Sohn
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Julia A Goralsky
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Jerry W Shay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA
| | - Jaewon Min
- Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
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19
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Sun H, Chen G, Guo B, Lv S, Yuan G. Potential clinical treatment prospects behind the molecular mechanism of alternative lengthening of telomeres (ALT). J Cancer 2023; 14:417-433. [PMID: 36860927 PMCID: PMC9969575 DOI: 10.7150/jca.80097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Accepted: 12/25/2022] [Indexed: 02/04/2023] Open
Abstract
Normal somatic cells inevitably experience replicative stress and senescence during proliferation. Somatic cell carcinogenesis can be prevented in part by limiting the reproduction of damaged or old cells and removing them from the cell cycle [1, 2]. However, Cancer cells must overcome the issues of replication pressure and senescence as well as preserve telomere length in order to achieve immortality, in contrast to normal somatic cells [1, 2]. Although telomerase accounts for the bulk of telomere lengthening methods in human cancer cells, there is a non-negligible portion of telomere lengthening pathways that depend on alternative lengthening of telomeres (ALT) [3]. For the selection of novel possible therapeutic targets for ALT-related disorders, a thorough understanding of the molecular biology of these diseases is crucial [4]. The roles of ALT, typical ALT tumor cell traits, the pathophysiology and molecular mechanisms of ALT tumor disorders, such as adrenocortical carcinoma (ACC), are all summarized in this work. Additionally, this research compiles as many of its hypothetically viable but unproven treatment targets as it can (ALT-associated PML bodies (APB), etc.). This review is intended to contribute as much as possible to the development of research, while also trying to provide a partial information for prospective investigations on ALT pathways and associated diseases.
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Affiliation(s)
- Haolu Sun
- Department of Pathophysiology, School of Basic Medical Sciences, Anhui Medical University, Hefei, 230011, China
| | - Guijuan Chen
- School of Environment and Chemical Engineering, Anhui Vocational and Technical College, Hefei, 230011, China
| | - Baochang Guo
- Rehabilitation Department of Traditional Chinese Medicine, 969 Hospital of the Joint Support Force of the Chinese People's Liberation Army, Hohhot, 010000, China
| | - Shushu Lv
- Department of Pathology, The First Affiliated Hospital of Huzhou University, Huzhou 313000, China
| | - Guojun Yuan
- School of Environment and Chemical Engineering, Anhui Vocational and Technical College, Hefei, 230011, China
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20
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de Bardet JC, Cardentey CR, González BL, Patrone D, Mulet IL, Siniscalco D, Robinson-Agramonte MDLA. Cell Immortalization: In Vivo Molecular Bases and In Vitro Techniques for Obtention. BIOTECH 2023; 12:biotech12010014. [PMID: 36810441 PMCID: PMC9944833 DOI: 10.3390/biotech12010014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 01/25/2023] [Accepted: 01/26/2023] [Indexed: 01/31/2023] Open
Abstract
Somatic human cells can divide a finite number of times, a phenomenon known as the Hayflick limit. It is based on the progressive erosion of the telomeric ends each time the cell completes a replicative cycle. Given this problem, researchers need cell lines that do not enter the senescence phase after a certain number of divisions. In this way, more lasting studies can be carried out over time and avoid the tedious work involved in performing cell passes to fresh media. However, some cells have a high replicative potential, such as embryonic stem cells and cancer cells. To accomplish this, these cells express the enzyme telomerase or activate the mechanisms of alternative telomere elongation, which favors the maintenance of the length of their stable telomeres. Researchers have been able to develop cell immortalization technology by studying the cellular and molecular bases of both mechanisms and the genes involved in the control of the cell cycle. Through it, cells with infinite replicative capacity are obtained. To obtain them, viral oncogenes/oncoproteins, myc genes, ectopic expression of telomerase, and the manipulation of genes that regulate the cell cycle, such as p53 and Rb, have been used.
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Affiliation(s)
- Javier Curi de Bardet
- Department of Neurobiology, International Center for Neurological Restoration, Havana 11300, Cuba
| | | | - Belkis López González
- Department of Allergy, Calixto Garcia General University Hospital, Havana 10400, Cuba
| | - Deanira Patrone
- Department of Experimental Medicine, Division of Molecular Biology, Biotechnology and Histology, University of Campania, 80138 Naples, Italy
| | | | - Dario Siniscalco
- Department of Experimental Medicine, Division of Molecular Biology, Biotechnology and Histology, University of Campania, 80138 Naples, Italy
- Correspondence:
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21
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Ballinger ML, Pattnaik S, Mundra PA, Zaheed M, Rath E, Priestley P, Baber J, Ray-Coquard I, Isambert N, Causeret S, van der Graaf WTA, Puri A, Duffaud F, Le Cesne A, Seddon B, Chandrasekar C, Schiffman JD, Brohl AS, James PA, Kurtz JE, Penel N, Myklebost O, Meza-Zepeda LA, Pickett H, Kansara M, Waddell N, Kondrashova O, Pearson JV, Barbour AP, Li S, Nguyen TL, Fatkin D, Graham RM, Giannoulatou E, Green MJ, Kaplan W, Ravishankar S, Copty J, Powell JE, Cuppen E, van Eijk K, Veldink J, Ahn JH, Kim JE, Randall RL, Tucker K, Judson I, Sarin R, Ludwig T, Genin E, Deleuze JF, Haber M, Marshall G, Cairns MJ, Blay JY, Thomas DM, Tattersall M, Neuhaus S, Lewis C, Tucker K, Carey-Smith R, Wood D, Porceddu S, Dickinson I, Thorne H, James P, Ray-Coquard I, Blay JY, Cassier P, Le Cesne A, Duffaud F, Penel N, Isambert N, Kurtz JE, Puri A, Sarin R, Ahn JH, Kim JE, Ward I, Judson I, van der Graaf W, Seddon B, Chandrasekar C, Rickar R, Hennig I, Schiffman J, Randall RL, Silvestri A, Zaratzian A, Tayao M, Walwyn K, Niedermayr E, Mang D, Clark R, Thorpe T, MacDonald J, Riddell K, Mar J, Fennelly V, Wicht A, Zielony B, Galligan E, Glavich G, Stoeckert J, Williams L, Djandjgava L, Buettner I, Osinki C, Stephens S, Rogasik M, Bouclier L, Girodet M, Charreton A, Fayet Y, Crasto S, Sandupatla B, Yoon Y, Je N, Thompson L, Fowler T, Johnson B, Petrikova G, Hambridge T, Hutchins A, Bottero D, Scanlon D, Stokes-Denson J, Génin E, Campion D, Dartigues JF, Deleuze JF, Lambert JC, Redon R, Ludwig T, Grenier-Boley B, Letort S, Lindenbaum P, Meyer V, Quenez O, Dina C, Bellenguez C, Le Clézio CC, Giemza J, Chatel S, Férec C, Le Marec H, Letenneur L, Nicolas G, Rouault K. Heritable defects in telomere and mitotic function selectively predispose to sarcomas. Science 2023; 379:253-260. [PMID: 36656928 DOI: 10.1126/science.abj4784] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Accepted: 11/16/2022] [Indexed: 01/20/2023]
Abstract
Cancer genetics has to date focused on epithelial malignancies, identifying multiple histotype-specific pathways underlying cancer susceptibility. Sarcomas are rare malignancies predominantly derived from embryonic mesoderm. To identify pathways specific to mesenchymal cancers, we performed whole-genome germline sequencing on 1644 sporadic cases and 3205 matched healthy elderly controls. Using an extreme phenotype design, a combined rare-variant burden and ontologic analysis identified two sarcoma-specific pathways involved in mitotic and telomere functions. Variants in centrosome genes are linked to malignant peripheral nerve sheath and gastrointestinal stromal tumors, whereas heritable defects in the shelterin complex link susceptibility to sarcoma, melanoma, and thyroid cancers. These studies indicate a specific role for heritable defects in mitotic and telomere biology in risk of sarcomas.
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Affiliation(s)
- Mandy L Ballinger
- Garvan Institute of Medical Research, Sydney 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Sydney 2010, Australia
| | - Swetansu Pattnaik
- Garvan Institute of Medical Research, Sydney 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Sydney 2010, Australia
| | - Piyushkumar A Mundra
- Garvan Institute of Medical Research, Sydney 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Sydney 2010, Australia
| | - Milita Zaheed
- Hereditary Cancer Centre, Prince of Wales Hospital, Sydney 2031, Australia
| | - Emma Rath
- Garvan Institute of Medical Research, Sydney 2010, Australia
| | - Peter Priestley
- Hartwig Medical Foundation, 1098 XH Amsterdam, Netherlands
- Hartwig Medical Foundation Australia, Sydney 2000, Australia
| | - Jonathan Baber
- Hartwig Medical Foundation, 1098 XH Amsterdam, Netherlands
- Hartwig Medical Foundation Australia, Sydney 2000, Australia
| | - Isabelle Ray-Coquard
- Department of Adult Medical Oncology, Centre Leon Berard, University Claude Bernard, 69373 Lyon, France
| | | | | | | | - Ajay Puri
- Department of Orthopedic Oncology, Tata Memorial Hospital, Mumbai, Maharashtra 400012, India
| | | | | | - Beatrice Seddon
- Sarcoma Unit, University College Hospital, London NW1 2BU, UK
| | | | - Joshua D Schiffman
- Division of Pediatric Hematology/Oncology, Department of Pediatrics, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA
| | - Andrew S Brohl
- Sarcoma Department, Moffitt Cancer Center, Tampa, FL 33612, USA
| | - Paul A James
- The Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne 3010, Australia
- Parkville Familial Cancer Centre, Peter MacCallum Cancer Centre and Royal Melbourne Hospital, Melbourne 3000, Australia
| | | | | | - Ola Myklebost
- Western Norway Familial Cancer Centre, Haukeland University Hospital, 5021 Bergen, Norway
- Department of Clinical Science, University of Bergen, 5007 Bergen, Norway
- Institute for Cancer Research, Oslo University Hospital, N-0424 Oslo, Norway
| | | | - Hilda Pickett
- Children's Medical Research Institute, The University of Sydney, Westmead 2145, Australia
| | - Maya Kansara
- Garvan Institute of Medical Research, Sydney 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Sydney 2010, Australia
| | - Nicola Waddell
- QIMR Berghofer Medical Research Institute, Brisbane 4006, Australia
| | - Olga Kondrashova
- QIMR Berghofer Medical Research Institute, Brisbane 4006, Australia
| | - John V Pearson
- QIMR Berghofer Medical Research Institute, Brisbane 4006, Australia
| | - Andrew P Barbour
- Faculty of Medicine. The University of Queensland, Brisbane 4072, Australia
| | - Shuai Li
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne 3010, Australia
- Centre for Cancer Genetic Epidemiology, Department of Public Health and Primary Care, University of Cambridge, Cambridge CB1 8RN, UK
- Precision Medicine, School of Clinical Sciences at Monash Health, Monash University, Clayton 3800, Australia
- Murdoch Children's Research Institute, Royal Children's Hospital, Parkville 3051, Australia
| | - Tuong L Nguyen
- Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne 3010, Australia
| | - Diane Fatkin
- St Vincent's Clinical School, University of New South Wales, Sydney 2010, Australia
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst 2010, Australia
- Cardiology Department, St Vincent's Hospital, Sydney 2010, Australia
| | - Robert M Graham
- St Vincent's Clinical School, University of New South Wales, Sydney 2010, Australia
- Molecular Cardiology Division, Victor Chang Cardiac Research Institute, Darlinghurst 2010, Australia
| | - Eleni Giannoulatou
- St Vincent's Clinical School, University of New South Wales, Sydney 2010, Australia
- Computational Genomics Division, Victor Chang Cardiac Research Institute, Sydney 2010, Australia
| | - Melissa J Green
- School of Psychiatry, University of New South Wales, Sydney 2052, Australia
- Neuorscience Research Australia, Sydney 2031, Australia
| | - Warren Kaplan
- Garvan Institute of Medical Research, Sydney 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Sydney 2010, Australia
| | | | - Joseph Copty
- Garvan Institute of Medical Research, Sydney 2010, Australia
| | - Joseph E Powell
- Garvan Institute of Medical Research, Sydney 2010, Australia
- UNSW Cellular Genomics Futures Institute, University of New South Wales, Sydney 2052, Australia
| | - Edwin Cuppen
- Hartwig Medical Foundation, 1098 XH Amsterdam, Netherlands
| | - Kristel van Eijk
- Department of Neurology, University Medical Centre Utrecht Brain Center, Utrecht University, 3584 CX Utrecht, Netherlands
| | - Jan Veldink
- Department of Neurology, University Medical Centre Utrecht Brain Center, Utrecht University, 3584 CX Utrecht, Netherlands
| | - Jin-Hee Ahn
- Department of Oncology, Asan Medical Centre, Seoul 05505, South Korea
| | - Jeong Eun Kim
- Department of Oncology, Asan Medical Centre, Seoul 05505, South Korea
| | - R Lor Randall
- Department of Orthopaedic Surgery, University of California, Davis Health, Sacramento, CA 95817, USA
| | - Kathy Tucker
- Hereditary Cancer Centre, Prince of Wales Hospital, Sydney 2031, Australia
| | - Ian Judson
- Sarcoma Unit, The Royal Marsden NHS Foundation Trust, London SW3 6JJ, UK
| | - Rajiv Sarin
- Cancer Genetics Unit, ACTREC, Tata Memorial Centre, Mumbai, Maharashtra 410210, India
| | - Thomas Ludwig
- Université de Brest, Inserm, EFS, UMR 1078, GGB, CHU de Brest, 29200 Brest, France
| | - Emmanuelle Genin
- Université de Brest, Inserm, EFS, UMR 1078, GGB, CHU de Brest, 29200 Brest, France
| | - Jean-Francois Deleuze
- Centre National de Recherche en Génomique Humaine, Institut de Génomique, 91057 Evry, France
| | - Michelle Haber
- Children's Cancer Institute, Lowy Cancer Research Centre, University of New South Wales, Kensington 2033, Australia
| | - Glenn Marshall
- Children's Cancer Institute, Lowy Cancer Research Centre, University of New South Wales, Kensington 2033, Australia
- Kids Cancer Centre, Sydney Children's Hospital, Randwick 2031, Australia
| | - Murray J Cairns
- School of Biomedical Sciences and Pharmacy, The University of Newcastle, Callaghan 2308, Australia
- Centre for Brain and Mental Health Research, The Hunter Medical Research Institute, Newcastle 2305, Australia
| | - Jean-Yves Blay
- Department of Adult Medical Oncology, Centre Leon Berard, University Claude Bernard, 69373 Lyon, France
| | - David M Thomas
- Garvan Institute of Medical Research, Sydney 2010, Australia
- St Vincent's Clinical School, University of New South Wales, Sydney 2010, Australia
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22
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Hodson C, van Twest S, Dylewska M, O'Rourke JJ, Tan W, Murphy VJ, Walia M, Abbouche L, Nieminuszczy J, Dunn E, Bythell-Douglas R, Heierhorst J, Niedzwiedz W, Deans AJ. Branchpoint translocation by fork remodelers as a general mechanism of R-loop removal. Cell Rep 2022; 41:111749. [PMID: 36476850 DOI: 10.1016/j.celrep.2022.111749] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 10/05/2022] [Accepted: 11/09/2022] [Indexed: 12/12/2022] Open
Abstract
Co-transcriptional R loops arise from stalling of RNA polymerase, leading to the formation of stable DNA:RNA hybrids. Unresolved R loops promote genome instability but are counteracted by helicases and nucleases. Here, we show that branchpoint translocases are a third class of R-loop-displacing enzyme in vitro. In cells, deficiency in the Fanconi-anemia-associated branchpoint translocase FANCM causes R-loop accumulation, particularly after treatment with DNA:RNA-hybrid-stabilizing agents. This correlates with FANCM localization at R-loop-prone regions of the genome. Moreover, other branchpoint translocases associated with human disease, such as SMARCAL1 and ZRANB3, and those from lower organisms can also remove R loops in vitro. Branchpoint translocases are more potent than helicases in resolving R loops, indicating their evolutionary important role in R-loop suppression. In human cells, FANCM, SMARCAL1, and ZRANB3 depletion causes additive effects on R-loop accumulation and DNA damage. Our work reveals a mechanistic basis for R-loop displacement that is linked to genome stability.
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Affiliation(s)
- Charlotte Hodson
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia
| | - Sylvie van Twest
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia
| | | | - Julienne J O'Rourke
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia
| | - Winnie Tan
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia
| | - Vincent J Murphy
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia
| | - Mannu Walia
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia
| | - Lara Abbouche
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia
| | | | - Elyse Dunn
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia
| | - Rohan Bythell-Douglas
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia
| | - Jörg Heierhorst
- Department of Medicine (St Vincent's Health), University of Melbourne, Fitzroy, VIC 3065, Australia; Molecular Genetics Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia
| | | | - Andrew J Deans
- Genome Stability Unit, St. Vincent's Institute of Medical Research, Fitzroy, VIC 3065, Australia; Department of Medicine (St Vincent's Health), University of Melbourne, Fitzroy, VIC 3065, Australia.
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23
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Zhang FL, Li DQ. Targeting Chromatin-Remodeling Factors in Cancer Cells: Promising Molecules in Cancer Therapy. Int J Mol Sci 2022; 23:12815. [PMID: 36361605 PMCID: PMC9655648 DOI: 10.3390/ijms232112815] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 10/12/2022] [Accepted: 10/19/2022] [Indexed: 03/28/2024] Open
Abstract
ATP-dependent chromatin-remodeling complexes can reorganize and remodel chromatin and thereby act as important regulator in various cellular processes. Based on considerable studies over the past two decades, it has been confirmed that the abnormal function of chromatin remodeling plays a pivotal role in genome reprogramming for oncogenesis in cancer development and/or resistance to cancer therapy. Recently, exciting progress has been made in the identification of genetic alteration in the genes encoding the chromatin-remodeling complexes associated with tumorigenesis, as well as in our understanding of chromatin-remodeling mechanisms in cancer biology. Here, we present preclinical evidence explaining the signaling mechanisms involving the chromatin-remodeling misregulation-induced cancer cellular processes, including DNA damage signaling, metastasis, angiogenesis, immune signaling, etc. However, even though the cumulative evidence in this field provides promising emerging molecules for therapeutic explorations in cancer, more research is needed to assess the clinical roles of these genetic cancer targets.
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Affiliation(s)
- Fang-Lin Zhang
- Shanghai Cancer Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Cancer Institute, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
| | - Da-Qiang Li
- Shanghai Cancer Center and Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Cancer Institute, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Department of Breast Surgery, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Shanghai Key Laboratory of Breast Cancer, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Shanghai Key Laboratory of Radiation Oncology, Shanghai Medical College, Fudan University, Shanghai 200032, China
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24
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Meeser A, Bartenhagen C, Werr L, Hellmann AM, Kahlert Y, Hemstedt N, Nürnberg P, Altmüller J, Ackermann S, Hero B, Simon T, Peifer M, Fischer M, Rosswog C. Reliable assessment of telomere maintenance mechanisms in neuroblastoma. Cell Biosci 2022; 12:160. [PMID: 36153564 PMCID: PMC9508734 DOI: 10.1186/s13578-022-00896-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 09/03/2022] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND Telomere maintenance mechanisms (TMM) are a hallmark of high-risk neuroblastoma, and are conferred by activation of telomerase or alternative lengthening of telomeres (ALT). However, detection of TMM is not yet part of the clinical routine, and consensus on TMM detection, especially on ALT assessment, remains to be achieved. METHODS Whole genome sequencing (WGS) data of 68 primary neuroblastoma samples were analyzed. Telomere length was calculated from WGS data or by telomere restriction fragment analysis (n = 39). ALT was assessed by C-circle assay (CCA, n = 67) and detection of ALT-associated PML nuclear bodies (APB) by combined fluorescence in situ hybridization and immunofluorescence staining (n = 68). RNA sequencing was performed (n = 64) to determine expression of TERT and telomeric long non-coding RNA (TERRA). Telomerase activity was examined by telomerase repeat amplification protocol (TRAP, n = 15). RESULTS Tumors were considered as telomerase-positive if they harbored a TERT rearrangement, MYCN amplification or high TERT expression (45.6%, 31/68), and ALT-positive if they were positive for APB and CCA (19.1%, 13/68). If all these markers were absent, tumors were considered TMM-negative (25.0%, 17/68). According to these criteria, the majority of samples were classified unambiguously (89.7%, 61/68). Assessment of additional ALT-associated parameters clarified the TMM status of the remaining seven cases with high likelihood: ALT-positive tumors had higher TERRA expression, longer telomeres, more telomere insertions, a characteristic pattern of telomere variant repeats, and were associated with ATRX mutations. CONCLUSIONS We here propose a workflow to reliably detect TMM in neuroblastoma. We show that unambiguous classification is feasible following a stepwise approach that determines both, activation of telomerase and ALT. The workflow proposed in this study can be used in clinical routine and provides a framework to systematically and reliably determine telomere maintenance mechanisms for risk stratification and treatment allocation of neuroblastoma patients.
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Affiliation(s)
- Alina Meeser
- Department of Experimental Pediatric Oncology, University Children's Hospital of Cologne, Kerpener Str. 62, 50937, Cologne, Germany
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany
| | - Christoph Bartenhagen
- Department of Experimental Pediatric Oncology, University Children's Hospital of Cologne, Kerpener Str. 62, 50937, Cologne, Germany
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany
| | - Lisa Werr
- Department of Experimental Pediatric Oncology, University Children's Hospital of Cologne, Kerpener Str. 62, 50937, Cologne, Germany
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany
| | - Anna-Maria Hellmann
- Department of Experimental Pediatric Oncology, University Children's Hospital of Cologne, Kerpener Str. 62, 50937, Cologne, Germany
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany
| | - Yvonne Kahlert
- Department of Experimental Pediatric Oncology, University Children's Hospital of Cologne, Kerpener Str. 62, 50937, Cologne, Germany
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany
| | - Nadine Hemstedt
- Department of Experimental Pediatric Oncology, University Children's Hospital of Cologne, Kerpener Str. 62, 50937, Cologne, Germany
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany
| | - Peter Nürnberg
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany
- Cologne Center for Genomics (CCG), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Janine Altmüller
- Cologne Center for Genomics (CCG), University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
- Core Facility Genomics, Berlin Institute of Health at Charité - Universitätsmedizin Berlin, Berlin, Germany
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), Berlin, Germany
| | - Sandra Ackermann
- Department of Experimental Pediatric Oncology, University Children's Hospital of Cologne, Kerpener Str. 62, 50937, Cologne, Germany
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany
| | - Barbara Hero
- Department of Pediatric Oncology and Hematology, University of Cologne, Cologne, Germany
| | - Thorsten Simon
- Department of Pediatric Oncology and Hematology, University of Cologne, Cologne, Germany
| | - Martin Peifer
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany
- Department of Translational Genomics, Center of Integrated Oncology Cologne-Bonn, Medical Faculty, University of Cologne, Cologne, Germany
| | - Matthias Fischer
- Department of Experimental Pediatric Oncology, University Children's Hospital of Cologne, Kerpener Str. 62, 50937, Cologne, Germany.
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany.
| | - Carolina Rosswog
- Department of Experimental Pediatric Oncology, University Children's Hospital of Cologne, Kerpener Str. 62, 50937, Cologne, Germany.
- Center for Molecular Medicine Cologne, Medical Faculty, University of Cologne, Cologne, Germany.
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25
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Gao J, Pickett HA. Targeting telomeres: advances in telomere maintenance mechanism-specific cancer therapies. Nat Rev Cancer 2022; 22:515-532. [PMID: 35790854 DOI: 10.1038/s41568-022-00490-1] [Citation(s) in RCA: 70] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/25/2022] [Indexed: 12/31/2022]
Abstract
Cancer cells establish replicative immortality by activating a telomere-maintenance mechanism (TMM), be it telomerase or the alternative lengthening of telomeres (ALT) pathway. Targeting telomere maintenance represents an intriguing opportunity to treat the vast majority of all cancer types. Whilst telomerase inhibitors have historically been heralded as promising anticancer agents, the reality has been more challenging, and there are currently no therapeutic options for cancer types that use ALT despite their aggressive nature and poor prognosis. In this Review, we discuss the mechanistic differences between telomere maintenance by telomerase and ALT, the current methods used to detect each mechanism, the utility of these tests for clinical diagnosis, and recent developments in the therapeutic strategies being employed to target both telomerase and ALT. We present notable developments in repurposing established therapeutic agents and new avenues that are emerging to target cancer types according to which TMM they employ. These opportunities extend beyond inhibition of telomere maintenance, by finding and exploiting inherent weaknesses in the telomeres themselves to trigger rapid cellular effects that lead to cell death.
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Affiliation(s)
- Jixuan Gao
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW, Australia
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW, Australia.
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26
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Brenner KA, Nandakumar J. Consequences of telomere replication failure: the other end-replication problem. Trends Biochem Sci 2022; 47:506-517. [PMID: 35440402 PMCID: PMC9106919 DOI: 10.1016/j.tibs.2022.03.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 02/28/2022] [Accepted: 03/17/2022] [Indexed: 01/14/2023]
Abstract
Telomeres are chromosome-capping structures that protect ends of the linear genome from DNA damage sensors. However, these structures present obstacles during DNA replication. Incomplete telomere replication accelerates telomere shortening and limits replicative lifespan. Therefore, continued proliferation under conditions of replication stress requires a means of telomere repair, particularly in the absence of telomerase. It was recently revealed that replication stress triggers break-induced replication (BIR) and mitotic DNA synthesis (MiDAS) at mammalian telomeres; however, these mechanisms are error prone and primarily utilized in tumorigenic contexts. In this review article, we discuss the consequences of replication stress at telomeres and how use of available repair pathways contributes to genomic instability. Current research suggests that fragile telomeres are ultimately tumor-suppressive and thus may be better left unrepaired.
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Affiliation(s)
- Kirsten A Brenner
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Jayakrishnan Nandakumar
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA.
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Bhargava R, Lynskey ML, O’Sullivan RJ. New twists to the ALTernative endings at telomeres. DNA Repair (Amst) 2022; 115:103342. [DOI: 10.1016/j.dnarep.2022.103342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/02/2022] [Accepted: 05/05/2022] [Indexed: 11/30/2022]
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Hou K, Yu Y, Li D, Zhang Y, Zhang K, Tong J, Yang K, Jia S. Alternative Lengthening of Telomeres and Mediated Telomere Synthesis. Cancers (Basel) 2022; 14:cancers14092194. [PMID: 35565323 PMCID: PMC9105334 DOI: 10.3390/cancers14092194] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 04/24/2022] [Accepted: 04/25/2022] [Indexed: 12/01/2022] Open
Abstract
Simple Summary Alternative lengthing of telomere (ALT) is an important mechanism for maintaining telomere length and cell proliferation in telomerase-negative tumor cells. However, the molecular mechanism of ALT is still poorly understood. ALT occurs in a wide range of tumor types and usually associated with a worse clinical consequence. Here, we review the recent findings of ALT mechanisms, which promise ALT could be a valuable drug target for clinical telomerase-negative tumor treatment. Abstract Telomeres are DNA–protein complexes that protect eukaryotic chromosome ends from being erroneously repaired by the DNA damage repair system, and the length of telomeres indicates the replicative potential of the cell. Telomeres shorten during each division of the cell, resulting in telomeric damage and replicative senescence. Tumor cells tend to ensure cell proliferation potential and genomic stability by activating telomere maintenance mechanisms (TMMs) for telomere lengthening. The alternative lengthening of telomeres (ALT) pathway is the most frequently activated TMM in tumors of mesenchymal and neuroepithelial origin, and ALT also frequently occurs during experimental cellular immortalization of mesenchymal cells. ALT is a process that relies on homologous recombination (HR) to elongate telomeres. However, some processes in the ALT mechanism remain poorly understood. Here, we review the most recent understanding of ALT mechanisms and processes, which may help us to better understand how the ALT pathway is activated in cancer cells and determine the potential therapeutic targets in ALT pathway-stabilized tumors.
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Affiliation(s)
- Kailong Hou
- Faculty of Life Science and Technology, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China;
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
- First People’s Hospital of Yunnan Province, 157 Jinbi Road, Kunming 650032, China
| | - Yuyang Yu
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
| | - Duda Li
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
| | - Yanduo Zhang
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
| | - Ke Zhang
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
| | - Jinkai Tong
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
| | - Kunxian Yang
- First People’s Hospital of Yunnan Province, 157 Jinbi Road, Kunming 650032, China
- Correspondence: (K.Y.); (S.J.)
| | - Shuting Jia
- Laboratory of Molecular Genetics of Aging and Tumor, Medical School, Kunming University of Science and Technology, 727 Jing Ming Nan Road, Kunming 650500, China; (Y.Y.); (D.L.); (Y.Z.); (K.Z.); (J.T.)
- Correspondence: (K.Y.); (S.J.)
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Lu R, Pickett HA. Telomeric replication stress: the beginning and the end for alternative lengthening of telomeres cancers. Open Biol 2022; 12:220011. [PMID: 35259951 PMCID: PMC8905155 DOI: 10.1098/rsob.220011] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Telomeres are nucleoprotein structures that cap the ends of linear chromosomes. Telomeric DNA comprises terminal tracts of G-rich tandem repeats, which are inherently difficult for the replication machinery to navigate. Structural aberrations that promote activation of the alternative lengthening of telomeres (ALT) pathway of telomere maintenance exacerbate replication stress at ALT telomeres, driving fork stalling and fork collapse. This form of telomeric DNA damage perpetuates recombination-mediated repair pathways and break-induced telomere synthesis. The relationship between replication stress and DNA repair is tightly coordinated for the purpose of regulating telomere length in ALT cells, but has been shown to be experimentally manipulatable. This raises the intriguing possibility that induction of replication stress can be used as a means to cause toxic levels of DNA damage at ALT telomeres, thereby selectively disrupting the viability of ALT cancers.
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Affiliation(s)
- Robert Lu
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
| | - Hilda A. Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
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30
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Epum EA, Haber JE. DNA replication: the recombination connection. Trends Cell Biol 2022; 32:45-57. [PMID: 34384659 PMCID: PMC8688190 DOI: 10.1016/j.tcb.2021.07.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 07/18/2021] [Accepted: 07/20/2021] [Indexed: 01/03/2023]
Abstract
Failure to complete DNA replication is one of the major sources of genome instability leading to aneuploidy, chromosome breakage, and chromosome rearrangements that are associated with human cancer. One of the surprising revelations of the past decade is that the completion of replication at so-called common fragile sites (CFS) occurs very late in the cell cycle - at mitosis - through a process termed MiDAS (mitotic DNA synthesis). MiDAS is strongly related to another cancer-promoting phenomenon: the activation of alternative lengthening of telomeres (ALT). Our understanding of the mechanisms of ALT and MiDAS in mammalian cells has drawn heavily from recent advances in the study of break-induced replication (BIR), especially in budding yeast. We provide new insights into the BIR, MiDAS, and ALT pathways and their shared similarities.
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31
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Barroso-González J, García-Expósito L, Galaviz P, Lynskey ML, Allen JAM, Hoang S, Watkins SC, Pickett HA, O'Sullivan RJ. Anti-recombination function of MutSα restricts telomere extension by ALT-associated homology-directed repair. Cell Rep 2021; 37:110088. [PMID: 34879271 PMCID: PMC8724847 DOI: 10.1016/j.celrep.2021.110088] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/13/2021] [Accepted: 11/10/2021] [Indexed: 01/02/2023] Open
Abstract
Alternative lengthening of telomeres (ALT) is a telomere-elongation mechanism observed in ~15% of cancer subtypes. Current models indicate that ALT is mediated by homology-directed repair mechanisms. By disrupting MSH6 gene expression, we show that the deficiency of MutSα (MSH2/MSH6) DNA mismatch repair complex causes striking telomere hyperextension. Mechanistically, we show MutSα is specifically recruited to telomeres in ALT cells by associating with the proliferating-cell nuclear antigen (PCNA) subunit of the ALT telomere replisome. We also provide evidence that MutSα counteracts Bloom (BLM) helicase, which adopts a crucial role in stabilizing hyper-extended telomeres and maintaining the survival of MutSα-deficient ALT cancer cells. Lastly, we propose a model in which MutSα deficiency impairs heteroduplex rejection, leading to premature initiation of telomere DNA synthesis that coincides with an accumulation of telomere variant repeats (TVRs). These findings provide evidence that the MutSα DNA mismatch repair complex acts to restrain unwarranted ALT. Barroso-Gonzalez et al. show that the mismatch repair complex MutSα restricts the alternative lengthening of telomeres (ALT) pathway in cancer cells. MutSα has an anti-recombination function and limits recombination between heteroduplex sequences at telomeres, in part by counteracting the Bloom helicase (BLM).
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Affiliation(s)
- Jonathan Barroso-González
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Laura García-Expósito
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Pablo Galaviz
- Bioinformatics Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
| | - Michelle Lee Lynskey
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Joshua A M Allen
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
| | - SongMy Hoang
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Simon C Watkins
- Department of Cell Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - Hilda A Pickett
- Telomere Length Regulation Unit, Children's Medical Research Institute, Faculty of Medicine and Health, University of Sydney, Westmead, NSW 2145, Australia
| | - Roderick J O'Sullivan
- Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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32
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Kent T, Clynes D. Alternative Lengthening of Telomeres: Lessons to Be Learned from Telomeric DNA Double-Strand Break Repair. Genes (Basel) 2021; 12:1734. [PMID: 34828344 PMCID: PMC8619803 DOI: 10.3390/genes12111734] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 10/22/2021] [Accepted: 10/28/2021] [Indexed: 12/25/2022] Open
Abstract
The study of the molecular pathways underlying cancer has given us important insights into how breaks in our DNA are repaired and the dire consequences that can occur when these processes are perturbed. Extensive research over the past 20 years has shown that the key molecular event underpinning a subset of cancers involves the deregulated repair of DNA double-strand breaks (DSBs) at telomeres, which in turn leads to telomere lengthening and the potential for replicative immortality. Here we discuss, in-depth, recent major breakthroughs in our understanding of the mechanisms underpinning this pathway known as the alternative lengthening of telomeres (ALT). We explore how this gives us important insights into how DSB repair at telomeres is regulated, with relevance to the cell-cycle-dependent regulation of repair, repair of stalled replication forks and the spatial regulation of DSB repair.
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Affiliation(s)
- Thomas Kent
- Molecular Haematology Unit, Radcliffe Department of Medicine, The MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK;
| | - David Clynes
- Department of Oncology, The MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford OX3 9DS, UK
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33
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Brosnan-Cashman JA, Davis CM, Diplas BH, Meeker AK, Rodriguez FJ, Heaphy CM. SMARCAL1 loss and alternative lengthening of telomeres (ALT) are enriched in giant cell glioblastoma. Mod Pathol 2021; 34:1810-1819. [PMID: 34103668 DOI: 10.1038/s41379-021-00841-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2020] [Revised: 05/25/2021] [Accepted: 05/26/2021] [Indexed: 11/09/2022]
Abstract
Subsets of high-grade gliomas, including glioblastoma (GBM), are known to utilize the alternative lengthening of telomeres (ALT) pathway for telomere length maintenance. However, the telomere maintenance profile of one subtype of GBM-giant cell GBM-has not been extensively studied. Here, we investigated the prevalence of ALT, as well as ATRX and SMARCAL1 protein loss, in a cohort of classic giant cell GBM and GBM with giant cell features. To determine the presence of ALT, a telomere-specific fluorescence in situ hybridization assay was performed on 15 cases of classic giant cell GBM, 28 additional GBMs found to have giant cell features, and 1 anaplastic astrocytoma with giant cell features. ATRX, SMARCAL1, and IDH1 protein status were assessed in a proportion of cases by immunohistochemistry and were compared to clinical-pathologic and molecular characteristics. In the overall cohort of 44 cases, 19 (43%) showed evidence of ALT. Intriguingly, of the ALT-positive cases, only 9 (47.4%) displayed loss of the ALT suppressor ATRX by immunohistochemistry. Since inactivating mutations in SMARCAL1 have been identified in ATRX wild-type ALT-positive gliomas, we developed an immunohistochemistry assay for SMARCAL1 protein expression using genetically validated controls. Of the 19 ALT-positive cases, 6 (31.5%) showed loss or mis-localization of SMARCAL1 by immunohistochemistry. Of these cases, four retained ATRX protein expression, while two cases also displayed ATRX loss. Additionally, we assessed five cases from which multiple temporal samples were available and ALT status was concordant between both tumor biopsies. In summary, we have identified a subset of giant cell GBM that utilize the ALT telomere maintenance mechanism. Importantly, in addition to ATRX loss, ALT-positive tumors harboring SMARCAL1 alterations are prevalent in giant cell GBM.
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Affiliation(s)
- Jacqueline A Brosnan-Cashman
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,American Association for Cancer Research, Publications Division, Boston, MA, USA
| | - Christine M Davis
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Bill H Diplas
- The Preston Robert Tisch Brain Tumor Center at Duke, Duke University Medical Center, Durham, NC, USA.,Department of Pathology, Duke University Medical Center, Durham, NC, USA.,Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Alan K Meeker
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.,Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Fausto J Rodriguez
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Christopher M Heaphy
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, USA. .,Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, USA. .,Department of Medicine, Boston University School of Medicine, Boston, MA, USA.
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34
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Lamm N, Rogers S, Cesare AJ. Chromatin mobility and relocation in DNA repair. Trends Cell Biol 2021; 31:843-855. [PMID: 34183232 DOI: 10.1016/j.tcb.2021.06.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 06/02/2021] [Accepted: 06/03/2021] [Indexed: 01/17/2023]
Abstract
The nucleus is a dynamic environment containing chromatin, membraneless organelles, and specialized molecular structures at the nuclear membrane. Within the spectrum of DNA repair activities are observations of increased mobility of damaged chromatin and the displacement of DNA lesions to specific nuclear environments. Here, we focus on the role that nuclear-specific filamentous actin plays in mobilizing damaged chromatin in response to DNA double-strand breaks and replication stress. We also examine nuclear pore complexes and promyelocytic leukemia-nuclear bodies as specialized platforms for homology-directed repair. The literature suggests an emerging model where specific types of DNA lesions are subjected to nuclear-derived forces that mobilize damaged chromatin and promote interaction with repair hubs to facilitate specialized repair reactions.
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Affiliation(s)
- Noa Lamm
- Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, 2145, Australia
| | - Samuel Rogers
- Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, 2145, Australia
| | - Anthony J Cesare
- Children's Medical Research Institute, University of Sydney, Westmead, New South Wales, 2145, Australia.
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35
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Raghunandan M, Geelen D, Majerova E, Decottignies A. NHP2 downregulation counteracts hTR-mediated activation of the DNA damage response at ALT telomeres. EMBO J 2021; 40:e106336. [PMID: 33595114 DOI: 10.15252/embj.2020106336] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Revised: 01/15/2021] [Accepted: 01/18/2021] [Indexed: 11/09/2022] Open
Abstract
About 10% of cancer cells employ the "alternative lengthening of telomeres" (ALT) pathway instead of re-activating the hTERT subunit of human telomerase. The hTR RNA subunit is also abnormally silenced in some ALT+ cells not expressing hTERT, suggesting a possible negative non-canonical impact of hTR on ALT. Indeed, we show that ectopically expressed hTR reduces phosphorylation of ssDNA-binding protein RPA (p-RPAS33 ) at ALT telomeres by promoting the hnRNPA1- and DNA-PK-dependent depletion of RPA. The resulting defective ATR checkpoint signaling at telomeres impairs recruitment of the homologous recombination protein, RAD51. This induces ALT telomere fragility, increases POLD3-dependent C-circle production, and promotes the recruitment of the DNA damage marker 53BP1. In ALT+ cells that naturally retain hTR expression, NHP2 H/ACA ribonucleoprotein levels are downregulated, likely in order to restrain DNA damage response (DDR) activation at telomeres through reduced 53BP1 recruitment. This unexpected role of NHP2 is independent from hTR's non-canonical function in modulating telomeric p-RPAS33 . Collectively, our study shines new light on the interference between telomerase- and ALT-dependent pathways and unravels a crucial role for hTR and NHP2 in DDR regulation at ALT telomeres.
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Affiliation(s)
- Maya Raghunandan
- Genetic and Epigenetic Alterations of Genomes, de Duve Institute, Faculty of Pharmacy and Biomedical Sciences, Université catholique de Louvain, Brussels, Belgium
| | - Dan Geelen
- Genetic and Epigenetic Alterations of Genomes, de Duve Institute, Faculty of Pharmacy and Biomedical Sciences, Université catholique de Louvain, Brussels, Belgium
| | - Eva Majerova
- Genetic and Epigenetic Alterations of Genomes, de Duve Institute, Faculty of Pharmacy and Biomedical Sciences, Université catholique de Louvain, Brussels, Belgium
| | - Anabelle Decottignies
- Genetic and Epigenetic Alterations of Genomes, de Duve Institute, Faculty of Pharmacy and Biomedical Sciences, Université catholique de Louvain, Brussels, Belgium
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Shen M, Young A, Autexier C. PCNA, a focus on replication stress and the alternative lengthening of telomeres pathway. DNA Repair (Amst) 2021; 100:103055. [PMID: 33581499 DOI: 10.1016/j.dnarep.2021.103055] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 01/25/2021] [Indexed: 12/16/2022]
Abstract
The maintenance of telomeres, which are specialized stretches of DNA found at the ends of linear chromosomes, is a crucial step for the immortalization of cancer cells. Approximately 10-15 % of cancer cells use a homologous recombination-based mechanism known as the Alternative Lengthening of Telomeres (ALT) pathway to maintain their telomeres. Telomeres in general pose a challenge to DNA replication owing to their repetitive nature and potential for forming secondary structures. Telomeres in ALT+ cells especially are subject to elevated levels of replication stress compared to telomeres that are maintained by the enzyme telomerase, in part due to the incorporation of telomeric variant repeats at ALT+ telomeres, their on average longer lengths, and their modified chromatin states. Many DNA metabolic strategies exist to counter replication stress and to protect stalled replication forks. The role of proliferating cell nuclear antigen (PCNA) as a platform for recruiting protein partners that participate in several of these DNA replication and repair pathways has been well-documented. We propose that many of these pathways may be active at ALT+ telomeres, either to facilitate DNA replication, to manage replication stress, or during telomere extension. Here, we summarize recent evidence detailing the role of PCNA in pathways including DNA secondary structure resolution, DNA damage bypass, replication fork restart, and DNA damage synthesis. We propose that an examination of PCNA and its post-translational modifications (PTMs) may offer a unique lens by which we might gain insight into the DNA metabolic landscape that is distinctively present at ALT+ telomeres.
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Affiliation(s)
- Michelle Shen
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, H3A 0C7, Canada; Jewish General Hospital, Lady Davis Institute, Montreal, Quebec, H3T 1E2, Canada
| | - Adrian Young
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, H3A 0C7, Canada; Jewish General Hospital, Lady Davis Institute, Montreal, Quebec, H3T 1E2, Canada
| | - Chantal Autexier
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, H3A 0C7, Canada; Jewish General Hospital, Lady Davis Institute, Montreal, Quebec, H3T 1E2, Canada.
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37
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Alternative paths to telomere elongation. Semin Cell Dev Biol 2020; 113:88-96. [PMID: 33293233 DOI: 10.1016/j.semcdb.2020.11.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 10/31/2020] [Accepted: 11/09/2020] [Indexed: 11/24/2022]
Abstract
Overcoming cellular senescence that is induced by telomere shortening is critical in tumorigenesis. A majority of cancers achieve telomere maintenance through telomerase expression. However, a subset of cancers takes an alternate route for elongating telomeres: recombination-based alternative lengthening of telomeres (ALT). Current evidence suggests that break-induced replication (BIR), independent of RAD51, underlies ALT telomere synthesis. However, RAD51-dependent homologous recombination is required for homology search and inter-chromosomal telomere recombination in human ALT cancer cell maintenance. Accumulating evidence suggests that the breakdown of stalled replication forks, the replication stress, induces BIR at telomeres. Nevertheless, ALT research is still in its early stage and a comprehensive view is still unclear. Here, we review the current findings regarding the genesis of ALT, how this recombinant pathway is chosen, the epigenetic regulation of telomeres in ALT, and perspectives for clinical applications with the hope that this overview will generate new questions.
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38
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Dhar S, Datta A, Brosh RM. DNA helicases and their roles in cancer. DNA Repair (Amst) 2020; 96:102994. [PMID: 33137625 DOI: 10.1016/j.dnarep.2020.102994] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 09/28/2020] [Indexed: 12/15/2022]
Abstract
DNA helicases, known for their fundamentally important roles in genomic stability, are high profile players in cancer. Not only are there monogenic helicase disorders with a strong disposition to cancer, it is well appreciated that helicase variants are associated with specific cancers (e.g., breast cancer). Flipping the coin, DNA helicases are frequently overexpressed in cancerous tissues and reduction in helicase gene expression results in reduced proliferation and growth capacity, as well as DNA damage induction and apoptosis of cancer cells. The seminal roles of helicases in the DNA damage and replication stress responses, as well as DNA repair pathways, validate their vital importance in cancer biology and suggest their potential values as targets in anti-cancer therapy. In recent years, many laboratories have characterized the specialized roles of helicase to resolve transcription-replication conflicts, maintain telomeres, mediate cell cycle checkpoints, remodel stalled replication forks, and regulate transcription. In vivo models, particularly mice, have been used to interrogate helicase function and serve as a bridge for preclinical studies that may lead to novel therapeutic approaches. In this review, we will summarize our current knowledge of DNA helicases and their roles in cancer, emphasizing the latest developments.
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Affiliation(s)
- Srijita Dhar
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Arindam Datta
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
| | - Robert M Brosh
- Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA.
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39
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Joseph SA, Taglialatela A, Leuzzi G, Huang JW, Cuella-Martin R, Ciccia A. Time for remodeling: SNF2-family DNA translocases in replication fork metabolism and human disease. DNA Repair (Amst) 2020; 95:102943. [PMID: 32971328 DOI: 10.1016/j.dnarep.2020.102943] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 07/24/2020] [Accepted: 07/26/2020] [Indexed: 02/07/2023]
Abstract
Over the course of DNA replication, DNA lesions, transcriptional intermediates and protein-DNA complexes can impair the progression of replication forks, thus resulting in replication stress. Failure to maintain replication fork integrity in response to replication stress leads to genomic instability and predisposes to the development of cancer and other genetic disorders. Multiple DNA damage and repair pathways have evolved to allow completion of DNA replication following replication stress, thus preserving genomic integrity. One of the processes commonly induced in response to replication stress is fork reversal, which consists in the remodeling of stalled replication forks into four-way DNA junctions. In normal conditions, fork reversal slows down replication fork progression to ensure accurate repair of DNA lesions and facilitates replication fork restart once the DNA lesions have been removed. However, in certain pathological situations, such as the deficiency of DNA repair factors that protect regressed forks from nuclease-mediated degradation, fork reversal can cause genomic instability. In this review, we describe the complex molecular mechanisms regulating fork reversal, with a focus on the role of the SNF2-family fork remodelers SMARCAL1, ZRANB3 and HLTF, and highlight the implications of fork reversal for tumorigenesis and cancer therapy.
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Affiliation(s)
- Sarah A Joseph
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Angelo Taglialatela
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Giuseppe Leuzzi
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Jen-Wei Huang
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Raquel Cuella-Martin
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA
| | - Alberto Ciccia
- Department of Genetics and Development, Herbert Irving Comprehensive Cancer Center, Columbia University Irving Medical Center, New York, NY, USA.
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TCGA Pan-Cancer Genomic Analysis of Alternative Lengthening of Telomeres (ALT) Related Genes. Genes (Basel) 2020; 11:genes11070834. [PMID: 32708340 PMCID: PMC7397314 DOI: 10.3390/genes11070834] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 07/15/2020] [Accepted: 07/15/2020] [Indexed: 02/06/2023] Open
Abstract
Telomere maintenance mechanisms (TMM) are used by cancer cells to avoid apoptosis, 85–90% reactivate telomerase, while 10–15% use the alternative lengthening of telomeres (ALT). Due to anti-telomerase-based treatments, some tumors switch from a telomerase-dependent mechanism to ALT; in fact, the co-existence between both mechanisms has been observed in some cancers. Although different elements in the ALT pathway are uncovered, some molecular mechanisms are still poorly understood. Therefore, with the aim to identify potential molecular markers for the study of ALT, we combined in silico approaches in a 411 telomere maintenance gene set. As a consequence, we conducted a genomic analysis of these genes in 31 Pan-Cancer Atlas studies from The Cancer Genome Atlas and found 325,936 genomic alterations; from which, we identified 20 genes highly mutated in the cancer studies. Finally, we made a protein-protein interaction network and enrichment analysis to observe the main pathways of these genes and discuss their role in ALT-related processes, like homologous recombination and homology directed repair. Overall, due to the lack of understanding of the molecular mechanisms of ALT cancers, we proposed a group of genes, which after ex vivo validations, could represent new potential therapeutic markers in the study of ALT.
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Mason-Osann E, Terranova K, Lupo N, Lock YJ, Carson LM, Flynn RL. RAD54 promotes alternative lengthening of telomeres by mediating branch migration. EMBO Rep 2020; 21:e49495. [PMID: 32337843 PMCID: PMC7271314 DOI: 10.15252/embr.201949495] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 03/19/2020] [Accepted: 03/31/2020] [Indexed: 12/15/2022] Open
Abstract
Cancer cells can activate the alternative lengthening of telomeres (ALT) pathway to promote replicative immortality. The ALT pathway promotes telomere elongation through a homologous recombination pathway known as break‐induced replication (BIR), which is often engaged to repair single‐ended double‐stranded breaks (DSBs). Single‐ended DSBs are resected to promote strand invasion and facilitate the formation of a local displacement loop (D‐loop), which can trigger DNA synthesis, and ultimately promote telomere elongation. However, the exact proteins involved in the maturation, migration, and resolution of D‐loops at ALT telomeres are unclear. In vitro, the DNA translocase RAD54 both binds D‐loops and promotes branch migration suggesting that RAD54 may function to promote ALT activity. Here, we demonstrate that RAD54 is enriched at ALT telomeres and promotes telomeric DNA synthesis through its ATPase‐dependent branch migration activity. Loss of RAD54 leads to the formation of unresolved recombination intermediates at telomeres that form ultra‐fine anaphase bridges in mitosis. These data demonstrate an important role for RAD54 in promoting ALT‐mediated telomere synthesis.
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Affiliation(s)
- Emily Mason-Osann
- Departments of Pharmacology & Experimental Therapeutics, Medicine Cancer Center, Boston University School of Medicine, Boston, MA, USA
| | - Katherine Terranova
- Departments of Pharmacology & Experimental Therapeutics, Medicine Cancer Center, Boston University School of Medicine, Boston, MA, USA
| | - Nicholas Lupo
- Departments of Pharmacology & Experimental Therapeutics, Medicine Cancer Center, Boston University School of Medicine, Boston, MA, USA
| | - Ying Jie Lock
- Departments of Pharmacology & Experimental Therapeutics, Medicine Cancer Center, Boston University School of Medicine, Boston, MA, USA
| | - Lisa M Carson
- Departments of Pharmacology & Experimental Therapeutics, Medicine Cancer Center, Boston University School of Medicine, Boston, MA, USA
| | - Rachel Litman Flynn
- Departments of Pharmacology & Experimental Therapeutics, Medicine Cancer Center, Boston University School of Medicine, Boston, MA, USA
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Hsu RYC, Lin YC, Redon C, Sun Q, Singh DK, Wang Y, Aggarwal V, Mitra J, Matur A, Moriarity B, Ha T, Aladjem MI, Prasanth KV, Prasanth SG. ORCA/LRWD1 Regulates Homologous Recombination at ALT-Telomeres by Modulating Heterochromatin Organization. iScience 2020; 23:101038. [PMID: 32344376 PMCID: PMC7186530 DOI: 10.1016/j.isci.2020.101038] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 03/26/2020] [Accepted: 04/01/2020] [Indexed: 12/23/2022] Open
Abstract
Telomeres are maintained by telomerase or in a subset of cancer cells by a homologous recombination (HR)-based mechanism, Alternative Lengthening of Telomeres (ALT). The mechanisms regulating telomere-homeostasis in ALT cells remain unclear. We report that a replication initiator protein, Origin Recognition Complex-Associated (ORCA/LRWD1), by localizing at the ALT-telomeres, modulates HR activity. ORCA's localization to the ALT-telomeres is facilitated by its interaction to SUMOylated shelterin components. The loss of ORCA in ALT-positive cells elevates the levels of two mediators of HR, RPA and RAD51, and consistent with this, we observe increased ALT-associated promyelocytic leukemia body formation and telomere sister chromatid exchange. ORCA binds to RPA and modulates the association of RPA to telomeres. Finally, the loss of ORCA causes global chromatin decondensation, including at the telomeres. Our results demonstrate that ORCA acts as an inhibitor of HR by modulating RPA binding to ssDNA and inducing chromatin compaction.
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Affiliation(s)
- Rosaline Y C Hsu
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801, USA
| | - Yo-Chuen Lin
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801, USA
| | - Christophe Redon
- Developmental Therapeutics Branch, Center for Cancer Research, NCI, NIH, Bethesda MD 20892, USA
| | - Qinyu Sun
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801, USA
| | - Deepak K Singh
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801, USA
| | - Yating Wang
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801, USA
| | - Vasudha Aggarwal
- Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Jaba Mitra
- Materials Engineering Department, UIUC, Urbana, IL 61801, USA
| | - Abhijith Matur
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801, USA
| | | | - Taekjip Ha
- Biophysics and Biophysical Chemistry, Johns Hopkins University, Baltimore, MD 21205, USA; Howard Hughes Medical Institute, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Mirit I Aladjem
- Developmental Therapeutics Branch, Center for Cancer Research, NCI, NIH, Bethesda MD 20892, USA
| | - Kannanganattu V Prasanth
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801, USA; Cancer Center at Illinois, UIUC, Urbana, IL 61801, USA
| | - Supriya G Prasanth
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, 601S Goodwin Avenue, Urbana, IL 61801, USA; Cancer Center at Illinois, UIUC, Urbana, IL 61801, USA.
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43
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Zhang JM, Zou L. Alternative lengthening of telomeres: from molecular mechanisms to therapeutic outlooks. Cell Biosci 2020; 10:30. [PMID: 32175073 PMCID: PMC7063710 DOI: 10.1186/s13578-020-00391-6] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Accepted: 02/23/2020] [Indexed: 02/06/2023] Open
Abstract
To escape replicative senescence, cancer cells have to overcome telomere attrition during DNA replication. Most of cancers rely on telomerase to extend and maintain telomeres, but 4-11% of cancers use a homologous recombination-based pathway called alternative lengthening of telomeres (ALT). ALT is prevalent in cancers from the mesenchymal origin and usually associates with poor clinical outcome. Given its critical role in protecting telomeres and genomic integrity in tumor cells, ALT is an Achilles heel of tumors and an attractive target for cancer therapy. Here, we review the recent progress in the mechanistic studies of ALT, and discuss the emerging therapeutic strategies to target ALT-positive cancers.
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Affiliation(s)
- Jia-Min Zhang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129 USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129 USA.,2Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114 USA
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Zhang JM, Yadav T, Ouyang J, Lan L, Zou L. Alternative Lengthening of Telomeres through Two Distinct Break-Induced Replication Pathways. Cell Rep 2020; 26:955-968.e3. [PMID: 30673617 PMCID: PMC6366628 DOI: 10.1016/j.celrep.2018.12.102] [Citation(s) in RCA: 167] [Impact Index Per Article: 41.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 11/09/2018] [Accepted: 12/26/2018] [Indexed: 12/11/2022] Open
Abstract
Alternative lengthening of telomeres (ALT) is a telomerase-independent but recombination-dependent pathway that maintains telomeres. Here, we describe an assay to visualize ALT-mediated telomeric DNA synthesis in ALT-associated PML bodies (APBs) without DNA-damaging agents or replication inhibitors. Using this assay, we find that ALT occurs through two distinct mechanisms. One of the ALT mechanisms requires RAD52, a protein implicated in break-induced DNA replication (BIR). We demonstrate that RAD52 directly promotes telomeric D-loop formation in vitro and is required for maintaining telomeres in ALT-positive cells. Unexpectedly, however, RAD52 is dispensable for C-circle formation, a hallmark of ALT. In RAD52-knockout ALT cells, C-circle formation and RAD52-independent ALT DNA synthesis gradually increase as telomeres are shortened, and these activities are dependent on BLM and BIR proteins POLD3 and POLD4. These results suggest that ALT occurs through a RAD52-dependent and a RAD52-independent BIR pathway, revealing the bifurcated framework and dynamic nature of this process.
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Affiliation(s)
- Jia-Min Zhang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Tribhuwan Yadav
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Jian Ouyang
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA
| | - Li Lan
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA; Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Lee Zou
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA 02129, USA; Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA.
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45
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Bhargava R, Fischer M, O'Sullivan RJ. Genome rearrangements associated with aberrant telomere maintenance. Curr Opin Genet Dev 2020; 60:31-40. [PMID: 32145504 DOI: 10.1016/j.gde.2020.02.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 01/22/2020] [Accepted: 02/02/2020] [Indexed: 02/02/2023]
Abstract
There is unequivocal evidence that telomeres are crucial for cellular homeostasis and that telomere dysfunction can elicit genome instability and potentially initiate events that culminate in cancer. Mounting evidence points to telomeres having a crucial role in driving local and systemic structural rearrangements that drive cancer. These include the classical 'breakage-fusion-bridge' (BFB) cycles and more recently identified genome re-shaping events like kataegis and chromothripsis. In this brief review, we outline the established and most recent advances describing the roles that telomere dysfunction has in the origin of these catastrophic genome rearrangements. We discuss how local and systemic structural rearrangements enable telomere length maintenance, by either telomerase or the alternative lengthening of telomeres, that is essential to sustain cancer cell proliferation.
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Affiliation(s)
- Ragini Bhargava
- University of Pittsburgh UPMC Hillman Cancer Center, Pittsburgh, PA, USA
| | - Matthias Fischer
- Department of Experimental Pediatric Oncology, Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine, University of Cologne, Cologne, Germany.
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Mechanisms that drive telomere maintenance and recombination in human cancers. Curr Opin Genet Dev 2020; 60:25-30. [PMID: 32119936 DOI: 10.1016/j.gde.2020.02.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 01/22/2020] [Accepted: 02/02/2020] [Indexed: 12/19/2022]
Abstract
Telomere maintenance is essential for the continued proliferation of mitotically active cells. Alternative Lengthening of Telomeres (ALT) is a recombination-dependent pathway of telomere maintenance analogous to break-induced replication (BIR) [1] that becomes activated in approximately 10-15% of human cancers. ALT is prevalent in tumours of mesenchymal or neuroepithelial origin, and typically confers a poor prognosis. The aggressiveness and lack of effective strategies to treat these cancers make the ALT pathway a compelling potential therapeutic target to prevent tumour formation and/or the appearance of secondary malignancies after conventional chemotherapy [2]. While the precise initiator of ALT during tumourigenesis remains elusive, substantial progress has been made in interrogating the underlying homology-directed repair mechanisms that converge at telomeres to enable telomere length maintenance. Here, we describe recent advances in our understanding of the ALT mechanism and highlight potential therapeutic targets that may offer future promise in the treatment of ALT cancers.
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Feng E, Batenburg NL, Walker JR, Ho A, Mitchell TRH, Qin J, Zhu XD. CSB cooperates with SMARCAL1 to maintain telomere stability in ALT cells. J Cell Sci 2020; 133:jcs234914. [PMID: 31974116 DOI: 10.1242/jcs.234914] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 01/13/2020] [Indexed: 01/01/2023] Open
Abstract
Elevated replication stress is evident at telomeres of about 10-15% of cancer cells, which maintain their telomeres via a homologous recombination (HR)-based mechanism, referred to as alternative lengthening of telomeres (ALT). How ALT cells resolve replication stress to support their growth remains incompletely characterized. Here, we report that CSB (also known as ERCC6) promotes recruitment of HR repair proteins (MRN, BRCA1, BLM and RPA32) and POLD3 to ALT telomeres, a process that requires the ATPase activity of CSB and is controlled by ATM- and CDK2-dependent phosphorylation. Loss of CSB stimulates telomeric recruitment of MUS81 and SLX4, components of the structure-specific MUS81-EME1-SLX1-SLX4 (MUS-SLX) endonuclease complex, suggesting that CSB restricts MUS-SLX-mediated processing of stalled forks at ALT telomeres. Loss of CSB coupled with depletion of SMARCAL1, a chromatin remodeler implicated in catalyzing regression of stalled forks, synergistically promotes not only telomeric recruitment of MUS81 but also the formation of fragile telomeres, the latter of which is reported to arise from fork stalling. These results altogether suggest that CSB-mediated HR repair and SMARCAL1-mediated fork regression cooperate to prevent stalled forks from being processed into fragile telomeres in ALT cells.
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Affiliation(s)
- Emily Feng
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Nicole L Batenburg
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - John R Walker
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Angus Ho
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Taylor R H Mitchell
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Jian Qin
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Xu-Dong Zhu
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
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48
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Sommer A, Royle NJ. ALT: A Multi-Faceted Phenomenon. Genes (Basel) 2020; 11:E133. [PMID: 32012790 PMCID: PMC7073516 DOI: 10.3390/genes11020133] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 01/17/2020] [Accepted: 01/22/2020] [Indexed: 01/13/2023] Open
Abstract
One of the hallmarks of cancer cells is their indefinite replicative potential, made possible by the activation of a telomere maintenance mechanism (TMM). The majority of cancers reactivate the reverse transcriptase, telomerase, to maintain their telomere length but a minority (10% to 15%) utilize an alternative lengthening of telomeres (ALT) pathway. Here, we review the phenotypes and molecular markers specific to ALT, and investigate the significance of telomere mutations and sequence variation in ALT cell lines. We also look at the recent advancements in understanding the different mechanisms behind ALT telomere elongation and finally, the progress made in identifying potential ALT-targeted therapies, including those already in use for the treatment of both hematological and solid tumors.
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Affiliation(s)
| | - Nicola J. Royle
- Department of Genetics and Genome Biology, University of Leicester, Leicester LE1 7RH, UK;
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49
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Alternative Lengthening of Telomeres: Building Bridges To Connect Chromosome Ends. Trends Cancer 2020; 6:247-260. [PMID: 32101727 DOI: 10.1016/j.trecan.2019.12.009] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 12/16/2019] [Accepted: 12/19/2019] [Indexed: 12/15/2022]
Abstract
Alternative lengthening of telomeres (ALT) is a mechanism of telomere maintenance that is observed in many of the most recalcitrant cancer subtypes. Telomeres in ALT cancer cells exhibit a distinctive nucleoprotein architecture shaped by the mismanagement of chromatin that fosters cycles of DNA damage and replicative stress that activate homology-directed repair (HDR). Mutations in specific chromatin-remodeling factors appear to be key determinants of the emergence and survival of ALT cancer cells. However, these may represent vulnerabilities for the targeted elimination of ALT cancer cells that infiltrate tissues and organs to become devastating tumors. In this review we examine recent findings that provide new insights into the factors and mechanisms that mediate telomere length maintenance and survival of ALT cancer cells.
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50
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Kent T, Gracias D, Shepherd S, Clynes D. Alternative Lengthening of Telomeres in Pediatric Cancer: Mechanisms to Therapies. Front Oncol 2020; 9:1518. [PMID: 32039009 PMCID: PMC6985284 DOI: 10.3389/fonc.2019.01518] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 12/17/2019] [Indexed: 12/26/2022] Open
Abstract
Achieving replicative immortality is a crucial step in tumorigenesis and requires both bypassing cell cycle checkpoints and the extension of telomeres, sequences that protect the distal ends of chromosomes during replication. In the majority of cancers this is achieved through the enzyme telomerase, however a subset of cancers instead utilize a telomerase-independent mechanism of telomere elongation-the Alternative Lengthening of Telomeres (ALT) pathway. Recent work has aimed to decipher the exact mechanism that underlies this pathway. To this end, this pathway has now been shown to extend telomeres through exploitation of DNA repair machinery in a unique process that may present a number of druggable targets. The identification of such targets, and the subsequent development or repurposing of therapies to these targets may be crucial to improving the prognosis for many ALT-positive cancers, wherein mean survival is lower than non-ALT counterparts and the cancers themselves are particularly unresponsive to standard of care therapies. In this review we summarize the recent identification of many aspects of the ALT pathway, and the therapies that may be employed to exploit these new targets.
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Affiliation(s)
- Thomas Kent
- MRC Molecular Haematology Unit, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - Deanne Gracias
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - Samuel Shepherd
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
| | - David Clynes
- Department of Oncology, MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom
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