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Latancia MT, Leandro GDS, Bastos AU, Moreno NC, Ariwoola ABA, Martins DJ, Ashton NW, Ribeiro VC, Hoch NC, Rocha CRR, Woodgate R, Menck CFM. Human translesion DNA polymerases ι and κ mediate tolerance to temozolomide in MGMT-deficient glioblastoma cells. DNA Repair (Amst) 2024; 141:103715. [PMID: 39029375 DOI: 10.1016/j.dnarep.2024.103715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 06/03/2024] [Accepted: 06/24/2024] [Indexed: 07/21/2024]
Abstract
Glioblastoma (GBM) is a highly aggressive brain tumor associated with poor patient survival. The current standard treatment involves invasive surgery, radiotherapy, and chemotherapy employing temozolomide (TMZ). Resistance to TMZ is, however, a major challenge. Previous work from our group has identified candidate genes linked to TMZ resistance, including genes encoding translesion synthesis (TLS) DNA polymerases iota (Polɩ) and kappa (Polκ). These specialized enzymes are known for bypassing lesions and tolerating DNA damage. Here, we investigated the roles of Polɩ and Polκ in TMZ resistance, employing MGMT-deficient U251-MG glioblastoma cells, with knockout of either POLI or POLK genes encoding Polɩ and Polκ, respectively, and assess their viability and genotoxic stress responses upon subsequent TMZ treatment. Cells lacking either of these polymerases exhibited a significant decrease in viability following TMZ treatment compared to parental counterparts. The restoration of the missing polymerase led to a recovery of cell viability. Furthermore, knockout cells displayed increased cell cycle arrest, mainly in late S-phase, and lower levels of genotoxic stress after TMZ treatment, as assessed by a reduction of γH2AX foci and flow cytometry data. This implies that TMZ treatment does not trigger a significant H2AX phosphorylation response in the absence of these proteins. Interestingly, combining TMZ with Mirin (double-strand break repair pathway inhibitor) further reduced the cell viability and increased DNA damage and γH2AX positive cells in TLS KO cells, but not in parental cells. These findings underscore the crucial roles of Polɩ and Polκ in conferring TMZ resistance and the potential backup role of homologous recombination in the absence of these TLS polymerases. Targeting these TLS enzymes, along with double-strand break DNA repair inhibition, could, therefore, provide a promising strategy to enhance TMZ's effectiveness in treating GBM.
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Affiliation(s)
- Marcela Teatin Latancia
- Laboratory of DNA Repair, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP 05508-000, Brazil; Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA.
| | - Giovana da Silva Leandro
- Laboratory of DNA Repair, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP 05508-000, Brazil.
| | - André Uchimura Bastos
- Laboratory of DNA Repair, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP 05508-000, Brazil.
| | - Natália Cestari Moreno
- Laboratory of DNA Repair, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP 05508-000, Brazil; Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA.
| | - Abu-Bakr Adetayo Ariwoola
- Laboratory of DNA Repair, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP 05508-000, Brazil; Department of Clinical and Experimental Oncology, Federal University of São Paulo (UNIFESP), São Paulo 04037-003, Brazil.
| | - Davi Jardim Martins
- Laboratory of DNA Repair, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP 05508-000, Brazil; Laboratory of Genomic Stability, Chemistry Institute at University, University of São Paulo, São Paulo, SP 05508-000, Brazil.
| | - Nicholas William Ashton
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA.
| | - Victória Chaves Ribeiro
- Laboratory of Genomic Stability, Chemistry Institute at University, University of São Paulo, São Paulo, SP 05508-000, Brazil.
| | - Nicolas Carlos Hoch
- Laboratory of Genomic Stability, Chemistry Institute at University, University of São Paulo, São Paulo, SP 05508-000, Brazil.
| | - Clarissa Ribeiro Reily Rocha
- Department of Clinical and Experimental Oncology, Federal University of São Paulo (UNIFESP), São Paulo 04037-003, Brazil.
| | - Roger Woodgate
- Laboratory of Genomic Integrity, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-3371, USA.
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2
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Cheng X, An J, Lou J, Gu Q, Ding W, Droby GN, Wang Y, Wang C, Gao Y, Anand JR, Shelton A, Satterlee AB, Mann B, Hsiao YC, Liu CW, Lu K, Hingtgen S, Wang J, Liu Z, Miller CR, Wu D, Vaziri C, Yang Y. Trans-lesion synthesis and mismatch repair pathway crosstalk defines chemoresistance and hypermutation mechanisms in glioblastoma. Nat Commun 2024; 15:1957. [PMID: 38438348 PMCID: PMC10912752 DOI: 10.1038/s41467-024-45979-5] [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: 12/11/2022] [Accepted: 02/08/2024] [Indexed: 03/06/2024] Open
Abstract
Almost all Glioblastoma (GBM) are either intrinsically resistant to the chemotherapeutical drug temozolomide (TMZ) or acquire therapy-induced mutations that cause chemoresistance and recurrence. The genome maintenance mechanisms responsible for GBM chemoresistance and hypermutation are unknown. We show that the E3 ubiquitin ligase RAD18 (a proximal regulator of TLS) is activated in a Mismatch repair (MMR)-dependent manner in TMZ-treated GBM cells, promoting post-replicative gap-filling and survival. An unbiased CRISPR screen provides an aerial map of RAD18-interacting DNA damage response (DDR) pathways deployed by GBM to tolerate TMZ genotoxicity. Analysis of mutation signatures from TMZ-treated GBM reveals a role for RAD18 in error-free bypass of O6mG (the most toxic TMZ-induced lesion), and error-prone bypass of other TMZ-induced lesions. Our analyses of recurrent GBM patient samples establishes a correlation between low RAD18 expression and hypermutation. Taken together we define molecular underpinnings for the hallmark tumorigenic phenotypes of TMZ-treated GBM.
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Affiliation(s)
- Xing Cheng
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, 27599, USA
- Department of Neuro-Oncology, Chongqing University Cancer Hospital, Chongqing, China
| | - Jing An
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, 27599, USA
- Institute of Cancer Prevention and Treatment, Heilongjiang Academy of Medical Sciences, Harbin Medical University, Harbin, China
| | - Jitong Lou
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC, 27599, USA
- Eli Lilly and Company, Indianapolis, IN, 46285, USA
| | - Qisheng Gu
- Shanghai Institute of Immunity and Infection, Chinese Academy of Sciences, Shanghai, China
- Department of Immunology, Université Paris Cité, Paris, France
| | - Weimin Ding
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, USA
- Oncology Center, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Gaith Nabil Droby
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, 27599, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Yilin Wang
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Chenghao Wang
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Yanzhe Gao
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Jay Ramanlal Anand
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Abigail Shelton
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Andrew Benson Satterlee
- Eshelman School of Pharmacy, Division of Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Breanna Mann
- Eshelman School of Pharmacy, Division of Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Yun-Chung Hsiao
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Chih-Wei Liu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Kun Lu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Shawn Hingtgen
- Eshelman School of Pharmacy, Division of Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Jiguang Wang
- Division of Life Science, Department of Chemical and Biological Engineering, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong SAR, China
- Hong Kong Center for Neurodegenerative Diseases, InnoHK, Hong Kong SAR, China
| | - Zhaoliang Liu
- Institute of Cancer Prevention and Treatment, Heilongjiang Academy of Medical Sciences, Harbin Medical University, Harbin, China
| | - C Ryan Miller
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, 27599, USA
- Department of Pathology, Division of Neuropathology, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Di Wu
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC, 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, USA
- Division of Oral and Craniofacial Health Science, Adams School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Cyrus Vaziri
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, 27599, USA.
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, USA.
| | - Yang Yang
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, 27599, USA.
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, 27599, USA.
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3
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Cheng X, An J, Lou J, Gu Q, Ding W, Droby G, Wang Y, Wang C, Gao Y, Shelton A, Satterlee AB, Mann BE, Hsiao YC, Liu CW, Liu K, Hingtgen S, Wang J, Liu Z, Miller R, Wu D, Vaziri C, Yang Y. Trans-Lesion Synthesis and Mismatch Repair Pathway Crosstalk Defines Chemoresistance and Hypermutation Mechanisms in Glioblastoma. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.16.562506. [PMID: 37905107 PMCID: PMC10614844 DOI: 10.1101/2023.10.16.562506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Almost all Glioblastoma (GBM) are either intrinsically resistant to the chemotherapeutical drug temozolomide (TMZ) or acquire therapy-induced mutations that cause chemoresistance and recurrence. The genome maintenance mechanisms responsible for GBM chemoresistance and hypermutation are unknown. We show that the E3 ubiquitin ligase RAD18 (a proximal regulator of TLS) is activated in a Mismatch repair (MMR)-dependent manner in TMZ-treated GBM cells, promoting post-replicative gap-filling and survival. An unbiased CRISPR screen provides a new aerial map of RAD18-interacting DNA damage response (DDR) pathways deployed by GBM to tolerate TMZ genotoxicity. Analysis of mutation signatures from TMZ-treated GBM reveals a role for RAD18 in error-free bypass of O6mG (the most toxic TMZ-induced lesion), and error-prone bypass of other TMZ-induced lesions. Our analyses of recurrent GBM patient samples establishes a correlation between low RAD18 expression and hypermutation. Taken together we define novel molecular underpinnings for the hallmark tumorigenic phenotypes of TMZ-treated GBM.
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Affiliation(s)
- Xing Cheng
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Department of Neuro-Oncology, Chongqing University Cancer Hospital & Chongqing Cancer Institute & Chongqing Cancer Hospital, Chongqing, China
| | - Jing An
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Institute of Cancer Prevention and Treatment, Heilongjiang Academy of Medical Sciences, Harbin Medical University, Harbin, China
| | - Jitong Lou
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Qisheng Gu
- Unit of Immunity and Pediatric Infectious Diseases, Institute Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
- Department of Immunology, Université Paris Cité, Paris, France
| | - Weimin Ding
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
- Oncology Center, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Gaith Droby
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Yilin Wang
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Chenghao Wang
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Yanzhe Gao
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Abigail Shelton
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Andrew Benson Satterlee
- Eshelman School of Pharmacy, Division of Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina, Chapel Hill, NC 27599
| | - Breanna Elizabeth Mann
- Eshelman School of Pharmacy, Division of Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina, Chapel Hill, NC 27599
| | - Yun-Chung Hsiao
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Chih-Wei Liu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Kun Liu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Shawn Hingtgen
- Eshelman School of Pharmacy, Division of Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina, Chapel Hill, NC 27599
| | - Jiguang Wang
- Division of Life Science, Department of Chemical and Biological Engineering, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong SAR, China
- Hong Kong Center for Neurodegenerative Diseases, InnoHK, Hong Kong SAR, China
| | - Zhaoliang Liu
- Institute of Cancer Prevention and Treatment, Heilongjiang Academy of Medical Sciences, Harbin Medical University, Harbin, China
| | - Ryan Miller
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Department of Pathology, Division of Neuropathology, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Di Wu
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
- Division of Oral and Craniofacial Health Science, Adams School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Cyrus Vaziri
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Yang Yang
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
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4
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Cheng X, An J, Lou J, Gu Q, Ding W, Droby G, Wang Y, Wang C, Gao Y, Shelton A, Satterlee AB, Mann BE, Hsiao YC, Liu CW, Liu K, Hingtgen S, Wang J, Liu Z, Miller R, Wu D, Vaziri C, Yang Y. Trans-Lesion Synthesis and Mismatch Repair Pathway Crosstalk Defines Chemoresistance and Hypermutation Mechanisms in Glioblastoma. RESEARCH SQUARE 2023:rs.3.rs-2367368. [PMID: 37886584 PMCID: PMC10602147 DOI: 10.21203/rs.3.rs-2367368/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
Almost all Glioblastoma (GBM) are either intrinsically resistant to the chemotherapeutical drug temozolomide (TMZ) or acquire therapy-induced mutations that cause chemoresistance and recurrence. The genome maintenance mechanisms responsible for GBM chemoresistance and hypermutation are unknown. We show that the E3 ubiquitin ligase RAD18 (a proximal regulator of TLS) is activated in a Mismatch repair (MMR)-dependent manner in TMZ-treated GBM cells, promoting post-replicative gap-filling and survival. An unbiased CRISPR screen provides a new aerial map of RAD18-interacting DNA damage response (DDR) pathways deployed by GBM to tolerate TMZ genotoxicity. Analysis of mutation signatures from TMZ-treated GBM reveals a role for RAD18 in error-free bypass of O6mG (the most toxic TMZ-induced lesion), and error-prone bypass of other TMZ-induced lesions. Our analyses of recurrent GBM patient samples establishes a correlation between low RAD18 expression and hypermutation. Taken together we define novel molecular underpinnings for the hallmark tumorigenic phenotypes of TMZ-treated GBM.
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Affiliation(s)
- Xing Cheng
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Department of Neuro-Oncology, Chongqing University Cancer Hospital & Chongqing Cancer Institute & Chongqing Cancer Hospital, Chongqing, China
| | - Jing An
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Institute of Cancer Prevention and Treatment, Heilongjiang Academy of Medical Sciences, Harbin Medical University, Harbin, China
| | - Jitong Lou
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Qisheng Gu
- Unit of Immunity and Pediatric Infectious Diseases, Institute Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, China
- Department of Immunology, Université Paris Cité, Paris, France
| | - Weimin Ding
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
- Oncology Center, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Gaith Droby
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Curriculum in Genetics and Molecular Biology, University of North Carolina, Chapel Hill, NC 27599
| | - Yilin Wang
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Chenghao Wang
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Yanzhe Gao
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Abigail Shelton
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Andrew Benson Satterlee
- Eshelman School of Pharmacy, Division of Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina, Chapel Hill, NC 27599
| | - Breanna Elizabeth Mann
- Eshelman School of Pharmacy, Division of Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina, Chapel Hill, NC 27599
| | - Yun-Chung Hsiao
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Chih-Wei Liu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Kun Liu
- Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Shawn Hingtgen
- Eshelman School of Pharmacy, Division of Pharmacoengineering and Molecular Pharmaceutics, University of North Carolina, Chapel Hill, NC 27599
| | - Jiguang Wang
- Division of Life Science, Department of Chemical and Biological Engineering, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Hong Kong SAR, China
- Hong Kong Center for Neurodegenerative Diseases, InnoHK, Hong Kong SAR, China
| | - Zhaoliang Liu
- Institute of Cancer Prevention and Treatment, Heilongjiang Academy of Medical Sciences, Harbin Medical University, Harbin, China
| | - Ryan Miller
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Department of Pathology, Division of Neuropathology, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Di Wu
- Department of Biostatistics, University of North Carolina, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
- Division of Oral and Craniofacial Health Science, Adams School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Cyrus Vaziri
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Yang Yang
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA
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5
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Fuchs RP, Isogawa A, Paulo JA, Onizuka K, Takahashi T, Amunugama R, Duxin JP, Fujii S. Crosstalk between repair pathways elicits double-strand breaks in alkylated DNA and implications for the action of temozolomide. eLife 2021; 10:69544. [PMID: 34236314 PMCID: PMC8289412 DOI: 10.7554/elife.69544] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 07/07/2021] [Indexed: 12/12/2022] Open
Abstract
Temozolomide (TMZ), a DNA methylating agent, is the primary chemotherapeutic drug used in glioblastoma treatment. TMZ induces mostly N-alkylation adducts (N7-methylguanine and N3-methyladenine) and some O6-methylguanine (O6mG) adducts. Current models propose that during DNA replication, thymine is incorporated across from O6mG, promoting a futile cycle of mismatch repair (MMR) that leads to DNA double-strand breaks (DSBs). To revisit the mechanism of O6mG processing, we reacted plasmid DNA with N-methyl-N-nitrosourea (MNU), a temozolomide mimic, and incubated it in Xenopus egg-derived extracts. We have shown that in this system, MMR proteins are enriched on MNU-treated DNA and we observed robust, MMR-dependent, repair synthesis. Our evidence also suggests that MMR, initiated at O6mG:C sites, is strongly stimulated in cis by repair processing of other lesions, such as N-alkylation adducts. Importantly, MNU-treated plasmids display DSBs in extracts, the frequency of which increases linearly with the square of alkylation dose. We suggest that DSBs result from two independent repair processes, one involving MMR at O6mG:C sites and the other involving base excision repair acting at a nearby N-alkylation adduct. We propose a new, replication-independent mechanism of action of TMZ, which operates in addition to the well-studied cell cycle-dependent mode of action.
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Affiliation(s)
- Robert P Fuchs
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States
| | - Asako Isogawa
- Cancer Research Center of Marseille, UMR7258, CNRS, Marseille, France
| | - Joao A Paulo
- Department of Cell Biology, Harvard Medical School, Boston, United States
| | - Kazumitsu Onizuka
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai, Japan
| | | | - Ravindra Amunugama
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States
| | - Julien P Duxin
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States
| | - Shingo Fujii
- Cancer Research Center of Marseille, UMR7258, CNRS, Marseille, France
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Moscatello C, Di Nicola M, Veschi S, Di Gregorio P, Cianchetti E, Stuppia L, Battista P, Cama A, Curia MC, Aceto GM. Relationship between MUTYH, OGG1 and BRCA1 mutations and mRNA expression in breast and ovarian cancer predisposition. Mol Clin Oncol 2020; 14:15. [PMID: 33343895 PMCID: PMC7725208 DOI: 10.3892/mco.2020.2177] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 09/29/2020] [Indexed: 12/13/2022] Open
Abstract
The aetiology of breast and ovarian cancer (BC/OC) is multi-factorial. At present, the involvement of base excision repair (BER) glycosylases (MUTYH and OGG1) in BC/OC predisposition is controversial. The present study investigated whether germline mutation status and mRNA expression of two BER genes, MUTHY and OGG1, were correlated with BRCA1 in 59 patients with BC/OC and 50 matched population controls. In addition, to evaluate the relationship between MUTYH, OGG1 and BRCA1, their possible mutual modulation and correlation among mutational spectrum, gene expression and demographic characteristics were evaluated. The results identified 18 MUTYH and OGG1 variants, of which 4 were novel (2 MUTYH and 2 OGG1) in 44 of the 59 patients. In addition, two pathogenic mutations were identified: OGG1 p.Arg46Gln, detected in a patient with BC and a family history of cancer, and MUTYH p.Val234Gly in a patient with OC, also with a family history of cancer. A significant reduced transcript expression in MUTYH was observed (P=0.033) in cases, and in association with the presence of rare variants in the same gene (P=0.030). A significant correlation in the expression of the two BER genes was observed in cases (P=0.004), whereas OGG1 and BRCA1 was significantly correlated in cases (P=0.001) compared with controls (P=0.010). The results of the present study indicated that the relationship among mutational spectrum, gene expression and demographic characteristics may improve the genetic diagnosis and primary prevention of at-risk individuals belonging to families with reduced mRNA expression, regardless of mutation presence.
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Affiliation(s)
- Carmelo Moscatello
- Department of Medical, Oral and Biotechnological Sciences, 'G. d'Annunzio' University of Chieti-Pescara, I-66100 Chieti, Italy
| | - Marta Di Nicola
- Department of Medical, Oral and Biotechnological Sciences, 'G. d'Annunzio' University of Chieti-Pescara, I-66100 Chieti, Italy
| | - Serena Veschi
- Department of Pharmacy, 'G. d'Annunzio' University of Chieti-Pescara, I-66100 Chieti, Italy
| | - Patrizia Di Gregorio
- Department of Psychological, Health and Territorial Sciences, School of Medicine and Health Sciences, 'G. d'Annunzio' University of Chieti-Pescara, I-66100 Chieti, Italy
| | - Ettore Cianchetti
- Department of Medical, Oral and Biotechnological Sciences, 'G. d'Annunzio' University of Chieti-Pescara, I-66100 Chieti, Italy
| | - Liborio Stuppia
- Immunohaematology and Transfusional Medicine Service, 'SS. Annunziata' Hospital, I-66100 Chieti, Italy
| | - Pasquale Battista
- Department of Medical, Oral and Biotechnological Sciences, 'G. d'Annunzio' University of Chieti-Pescara, I-66100 Chieti, Italy
| | - Alessandro Cama
- Department of Pharmacy, 'G. d'Annunzio' University of Chieti-Pescara, I-66100 Chieti, Italy
| | - Maria Cristina Curia
- Department of Medical, Oral and Biotechnological Sciences, 'G. d'Annunzio' University of Chieti-Pescara, I-66100 Chieti, Italy
| | - Gitana Maria Aceto
- Department of Medical, Oral and Biotechnological Sciences, 'G. d'Annunzio' University of Chieti-Pescara, I-66100 Chieti, Italy
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Serebrenik AA, Starrett GJ, Leenen S, Jarvis MC, Shaban NM, Salamango DJ, Nilsen H, Brown WL, Harris RS. The deaminase APOBEC3B triggers the death of cells lacking uracil DNA glycosylase. Proc Natl Acad Sci U S A 2019; 116:22158-22163. [PMID: 31611371 PMCID: PMC6825264 DOI: 10.1073/pnas.1904024116] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Human cells express up to 9 active DNA cytosine deaminases with functions in adaptive and innate immunity. Many cancers manifest an APOBEC mutation signature and APOBEC3B (A3B) is likely the main enzyme responsible. Although significant numbers of APOBEC signature mutations accumulate in tumor genomes, the majority of APOBEC-catalyzed uracil lesions are probably counteracted in an error-free manner by the uracil base excision repair pathway. Here, we show that A3B-expressing cells can be selectively killed by inhibiting uracil DNA glycosylase 2 (UNG) and that this synthetic lethal phenotype requires functional mismatch repair (MMR) proteins and p53. UNG knockout human 293 and MCF10A cells elicit an A3B-dependent death. This synthetic lethal phenotype is dependent on A3B catalytic activity and reversible by UNG complementation. A3B expression in UNG-null cells causes a buildup of genomic uracil, and the ensuing lethality requires processing of uracil lesions (likely U/G mispairs) by MSH2 and MLH1 (likely noncanonical MMR). Cancer cells expressing high levels of endogenous A3B and functional p53 can also be killed by expressing an UNG inhibitor. Taken together, UNG-initiated base excision repair is a major mechanism counteracting genomic mutagenesis by A3B, and blocking UNG is a potential strategy for inducing the selective death of tumors.
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Affiliation(s)
- Artur A Serebrenik
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
| | - Gabriel J Starrett
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
- Laboratory of Cellular Oncology, National Cancer Institute, Bethesda, MD 20892
| | - Sterre Leenen
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
- Department of Radiation Oncology, Radboud University Medical Center, 6500 HB Nijmegen, The Netherlands
| | - Matthew C Jarvis
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
| | - Nadine M Shaban
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
| | - Daniel J Salamango
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
| | - Hilde Nilsen
- Department of Clinical Molecular Biology, University of Oslo, 1478 Lørenskog, Norway
- Akershus University Hospital, 1478 Lørenskog, Norway
| | - William L Brown
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455
| | - Reuben S Harris
- Department of Biochemistry, Molecular Biology and Biophysics, Masonic Cancer Center, University of Minnesota, Minneapolis, MN 55455;
- Howard Hughes Medical Institute, Minneapolis, MN 55455
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8
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Rancourt A, Sato S, Satoh MS. Dose-dependent spatiotemporal responses of mammalian cells to an alkylating agent. PLoS One 2019; 14:e0214512. [PMID: 30925183 PMCID: PMC6440626 DOI: 10.1371/journal.pone.0214512] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 03/14/2019] [Indexed: 11/18/2022] Open
Abstract
Cultured cell populations are composed of heterogeneous cells, and previous single-cell lineage tracking analysis of individual HeLa cells provided empirical evidence for significant heterogeneity of the rate of cell proliferation and induction of cell death. Nevertheless, such cell lines have been used for investigations of cellular responses to various substances, resulting in incomplete characterizations. This problem caused by heterogeneity within cell lines could be overcome by investigating the spatiotemporal responses of individual cells to a substance. However, no approach to investigate the responses by analyzing spatiotemporal data is currently available. Thus, this study aimed to analyze the spatiotemporal responses of individual HeLa cells to cytotoxic, sub-cytotoxic, and non-cytotoxic doses of the well-characterized carcinogen, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Although cytotoxic doses of MNNG are known to induce cell death, the single-cell tracking approach revealed that cell death occurred following at least four different cellular events, suggesting that cell death is induced via multiple processes. We also found that HeLa cells exposed to a sub-cytotoxic dose of MNNG were in a state of equilibrium between cell proliferation and cell death, with cell death again induced through different processes. However, exposure of cells to a non-cytotoxic dose of MNNG promoted growth by reducing the cell doubling time, thus promoting the growth of a sub-population of cells. A single-cell lineage tracking approach could dissect processes leading to cell death in a spatiotemporal manner and the results suggest that spatiotemporal data obtained by tracking individual cells can be used as a new type of bioinformatics data resource that enables the examination of cellular responses to various external substances.
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Affiliation(s)
- Ann Rancourt
- Laboratory of Glycobiology and Bioimaging, Research Centre for Infectious Diseases, CHUQ, Faculty of Medicine, Laval University, Quebec, Quebec, Canada
- Laboratory of DNA Damage Responses and Bioimaging, CHUQ, Faculty of Medicine, Laval University, Quebec, Quebec, Canada
| | - Sachiko Sato
- Laboratory of Glycobiology and Bioimaging, Research Centre for Infectious Diseases, CHUQ, Faculty of Medicine, Laval University, Quebec, Quebec, Canada
| | - Masahiko S. Satoh
- Laboratory of DNA Damage Responses and Bioimaging, CHUQ, Faculty of Medicine, Laval University, Quebec, Quebec, Canada
- * E-mail:
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9
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Cui J, Wang J, Huang S, Jiang X, Li Y, Wu W, Zhang X. The G2 phase arrest induced by sterigmatocystin is dependent on hMLH1- ERK/p38-p53 pathway in human esophageal epithelium cells in vitro. Food Chem Toxicol 2018; 115:205-211. [DOI: 10.1016/j.fct.2018.03.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 03/06/2018] [Accepted: 03/09/2018] [Indexed: 01/12/2023]
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10
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Li S, Zheng Y, Tian T, Wang M, Liu X, Liu K, Zhai Y, Dai C, Deng Y, Li S, Dai Z, Lu J. Pooling-analysis on hMLH1 polymorphisms and cancer risk: evidence based on 31,484 cancer cases and 45,494 cancer-free controls. Oncotarget 2017; 8:93063-93078. [PMID: 29190978 PMCID: PMC5696244 DOI: 10.18632/oncotarget.21810] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Accepted: 09/08/2017] [Indexed: 01/18/2023] Open
Abstract
To elucidate the veritable relationship between three hMLH1 polymorphisms (rs1800734, rs1799977, rs63750447) and cancer risk, we performed this meta-analysis based on overall published data up to May 2017, from PubMed, Web of knowledge, VIP, WanFang and CNKI database, and the references of the original studies or review articles. 57 publications including 31,484 cancer cases and 45,494 cancer-free controls were obtained. The quality assessment of six articles obtained a summarized score less than 6 in terms of the Newcastle-Ottawa Scale (NOS). All statistical analyses were calculated with the software STATA (Version 14.0; Stata Corp, College Station, TX). We found all the three polymorphisms can enhance overall cancer risk, especially in Asians, under different genetic comparisons. In the subgroup analysis by cancer type, we found a moderate association between rs1800734 and the risk of gastric cancer (allele model: OR = 1.14, P = 0.017; homozygote model: OR = 1.33, P = 0.019; dominant model: OR = 1.27, P = 0.024) and lung cancer in recessive model (OR = 1.27, P = 0.024). The G allele of rs1799977 polymorphism was proved to connect with susceptibility of colorectal cancer (allele model: OR = 1.21, P = 0.023; dominate model: OR = 1.32, P <0.0001) and prostate cancer (dominate model: OR = 1.36, P <0.0001). Rs63750447 showed an increased risk of colorectal cancer, endometrial cancer and gastric cancer under all genetic models. These findings provide evidence that hMLH1 polymorphisms may associate with cancer risk, especially in Asians.
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Affiliation(s)
- Sha Li
- Clinical Research Center, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China.,Department of Pharmacy, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
| | - Yi Zheng
- Clinical Research Center, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China.,Department of Oncology, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
| | - Tian Tian
- Department of Oncology, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
| | - Meng Wang
- Department of Oncology, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
| | - Xinghan Liu
- Department of Oncology, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
| | - Kang Liu
- Department of Oncology, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
| | - Yajing Zhai
- Clinical Research Center, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China
| | - Cong Dai
- Department of Oncology, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
| | - Yujiao Deng
- Department of Oncology, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
| | - Shanli Li
- Department of Oncology, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
| | - Zhijun Dai
- Department of Oncology, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710004, China
| | - Jun Lu
- Clinical Research Center, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, China
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11
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Jia P, Chastain M, Zou Y, Her C, Chai W. Human MLH1 suppresses the insertion of telomeric sequences at intra-chromosomal sites in telomerase-expressing cells. Nucleic Acids Res 2017; 45:1219-1232. [PMID: 28180301 PMCID: PMC5388398 DOI: 10.1093/nar/gkw1170] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 10/26/2016] [Accepted: 11/09/2016] [Indexed: 11/29/2022] Open
Abstract
Aberrant formation of interstitial telomeric sequences (ITSs) promotes genome instabilities. However, it is unclear how aberrant ITS formation is suppressed in human cells. Here, we report that MLH1, a key protein involved in mismatch repair (MMR), suppresses telomeric sequence insertion (TSI) at intra-chromosomal regions. The frequency of TSI can be elevated by double-strand break (DSB) inducer and abolished by ATM/ATR inhibition. Suppression of TSI requires MLH1 recruitment to DSBs, indicating that MLH1's role in DSB response/repair is important for suppressing TSI. Moreover, TSI requires telomerase activity but is independent of the functional status of p53 and Rb. Lastly, we show that TSI is associated with chromosome instabilities including chromosome loss, micronuclei formation and chromosome breakage that are further elevated by replication stress. Our studies uncover a novel link between MLH1, telomerase, telomere and genome stability.
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Affiliation(s)
- Pingping Jia
- Department of Biomedical Sciences, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, USA
| | - Megan Chastain
- Department of Biomedical Sciences, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, USA
| | - Ying Zou
- Cytogenetics Laboratory, Department of Pathology, the University of Maryland School of Medicine, Baltimore, MD, USA
| | - Chengtao Her
- School of Molecular Biosciences, Washington State University, Pullman, WA, USA
| | - Weihang Chai
- Department of Biomedical Sciences, Elson S. Floyd College of Medicine, Washington State University, Spokane, WA, USA
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12
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Yoneshima Y, Abolhassani N, Iyama T, Sakumi K, Shiomi N, Mori M, Shiomi T, Noda T, Tsuchimoto D, Nakabeppu Y. Deoxyinosine triphosphate induces MLH1/PMS2- and p53-dependent cell growth arrest and DNA instability in mammalian cells. Sci Rep 2016; 6:32849. [PMID: 27618981 PMCID: PMC5020429 DOI: 10.1038/srep32849] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 08/16/2016] [Indexed: 12/30/2022] Open
Abstract
Deoxyinosine (dI) occurs in DNA either by oxidative deamination of a previously incorporated deoxyadenosine residue or by misincorporation of deoxyinosine triphosphate (dITP) from the nucleotide pool during replication. To exclude dITP from the pool, mammals possess specific hydrolysing enzymes, such as inosine triphosphatase (ITPA). Previous studies have shown that deficiency in ITPA results in cell growth suppression and DNA instability. To explore the mechanisms of these phenotypes, we analysed ITPA-deficient human and mouse cells. We found that both growth suppression and accumulation of single-strand breaks in nuclear DNA of ITPA-deficient cells depended on MLH1/PMS2. The cell growth suppression of ITPA-deficient cells also depended on p53, but not on MPG, ENDOV or MSH2. ITPA deficiency significantly increased the levels of p53 protein and p21 mRNA/protein, a well-known target of p53, in an MLH1-dependent manner. Furthermore, MLH1 may also contribute to cell growth arrest by increasing the basal level of p53 activity.
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Affiliation(s)
- Yasuto Yoneshima
- Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8581, Japan
- Research Institute for Diseases of the Chest, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - Nona Abolhassani
- Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8581, Japan
| | - Teruaki Iyama
- Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8581, Japan
| | - Kunihiko Sakumi
- Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8581, Japan
- Research Center for Nucleotide Pool, Kyushu University, Fukuoka 812-8581, Japan
| | - Naoko Shiomi
- National Institute of Radiological Sciences, Chiba 263-8555, Japan
| | - Masahiko Mori
- National Institute of Radiological Sciences, Chiba 263-8555, Japan
| | - Tadahiro Shiomi
- National Institute of Radiological Sciences, Chiba 263-8555, Japan
| | - Tetsuo Noda
- Cancer Institute, Japanese Foundation for Cancer Research, Tokyo 135-8550, Japan
| | - Daisuke Tsuchimoto
- Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8581, Japan
- Research Center for Nucleotide Pool, Kyushu University, Fukuoka 812-8581, Japan
| | - Yusaku Nakabeppu
- Division of Neurofunctional Genomics, Department of Immunobiology and Neuroscience, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8581, Japan
- Research Center for Nucleotide Pool, Kyushu University, Fukuoka 812-8581, Japan
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13
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Li Z, Pearlman AH, Hsieh P. DNA mismatch repair and the DNA damage response. DNA Repair (Amst) 2016; 38:94-101. [PMID: 26704428 PMCID: PMC4740233 DOI: 10.1016/j.dnarep.2015.11.019] [Citation(s) in RCA: 199] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 09/17/2015] [Accepted: 11/30/2015] [Indexed: 12/12/2022]
Abstract
This review discusses the role of DNA mismatch repair (MMR) in the DNA damage response (DDR) that triggers cell cycle arrest and, in some cases, apoptosis. Although the focus is on findings from mammalian cells, much has been learned from studies in other organisms including bacteria and yeast [1,2]. MMR promotes a DDR mediated by a key signaling kinase, ATM and Rad3-related (ATR), in response to various types of DNA damage including some encountered in widely used chemotherapy regimes. An introduction to the DDR mediated by ATR reveals its immense complexity and highlights the many biological and mechanistic questions that remain. Recent findings and future directions are highlighted.
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Affiliation(s)
- Zhongdao Li
- Genetics & Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bldg. 5 Rm. 324, 5 Memorial Dr. MSC 0538, Bethesda, MD 20892-0538, USA
| | - Alexander H Pearlman
- Genetics & Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bldg. 5 Rm. 324, 5 Memorial Dr. MSC 0538, Bethesda, MD 20892-0538, USA
| | - Peggy Hsieh
- Genetics & Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bldg. 5 Rm. 324, 5 Memorial Dr. MSC 0538, Bethesda, MD 20892-0538, USA.
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14
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Abstract
DNA damage is caused by either endogenous cellular metabolic processes such as hydrolysis, oxidation, alkylation, and DNA base mismatches, or exogenous sources including ultraviolet (UV) light, ionizing radiation, and chemical agents. Damaged DNA that is not properly repaired can lead to genomic instability, driving tumorigenesis. To protect genomic stability, mammalian cells have evolved highly conserved DNA repair mechanisms to remove and repair DNA lesions. Telomeres are composed of long tandem TTAGGG repeats located at the ends of chromosomes. Maintenance of functional telomeres is critical for preventing genome instability. The telomeric sequence possesses unique features that predispose telomeres to a variety of DNA damage induced by environmental genotoxins. This review briefly describes the relevance of excision repair pathways in telomere maintenance, with the focus on base excision repair (BER), nucleotide excision repair (NER), and mismatch repair (MMR). By summarizing current knowledge on excision repair of telomere damage and outlining many unanswered questions, it is our hope to stimulate further interest in a better understanding of excision repair processes at telomeres and in how these processes contribute to telomere maintenance.
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Affiliation(s)
- Pingping Jia
- Elson S. Floyd College of Medicine, United States
| | - Chengtao Her
- School of Molecular Biosciences, Washington State University, United States
| | - Weihang Chai
- Elson S. Floyd College of Medicine, United States; School of Molecular Biosciences, Washington State University, United States.
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15
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Luciani-Torres MG, Moore DH, Goodson WH, Dairkee SH. Exposure to the polyester PET precursor--terephthalic acid induces and perpetuates DNA damage-harboring non-malignant human breast cells. Carcinogenesis 2014; 36:168-76. [PMID: 25411358 PMCID: PMC4291052 DOI: 10.1093/carcin/bgu234] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Accurate assessment of the biological impact of xenoestrogens could assist breast cancer prevention. Effects on DNA integrity of breast epithelium, which might be missed in common chemical test screens, underscore the importance of endpoints beyond estrogen receptor interaction and cell proliferation. Identification of early perturbations induced in cells from non-cancerous breast tissue is critical for understanding possible breast cancer risk from chemical exposure. We have demonstrated previously that exposure to the ubiquitous xenoestrogens, bisphenol A (BPA) and methyl paraben, promotes the hallmarks of cancer in non-malignant human high-risk donor breast epithelial cells (HRBECs) isolated from several donors. Here we show that terephthalic acid (TPA), a major chemical precursor of polyethylene terephthalate (PET) containers used for the storage of food and beverages, increased the ERα: ERβ ratio in multiple HRBEC samples, suggesting an estrogenic effect. Although, like BPA and methyl paraben, TPA also promoted resistance to tamoxifen-induced apoptosis, unlike these chemicals instead of inducing an increased S-phase fraction, TPA treatment arrested cell proliferation. DNA-PK, ATM and members of the MRN complex, known to be involved in DNA damage sensor and effector proteins, were elevated indicating induction of DNA strand breaks. Early DNA damage checkpoint response, mediated through p53/p21, led to G1 arrest in TPA-exposed cells. Removal of TPA from the growth medium resulted in the rapid induction of BCL2, increasing the ratio of anti-: pro-apoptotic proteins, together with overexpression of Cyclin A/CDK2 proteins. Consequently, despite elevated p53pSer15 and H2AXpSer139, indicating sustained DNA damage, TPA exposed cells resumed robust growth rates seen prior to TPA exposure. The propensity for the perpetuation of DNA aberrations that activate DNA damage pathways in non-malignant breast cells justifies careful consideration of human exposure to TPA, particularly at vulnerable life stages.
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Affiliation(s)
| | - Dan H Moore
- California Pacific Medical Center Research Institute, 475 Brannan Street, San Francisco, CA 94107, USA
| | - William H Goodson
- California Pacific Medical Center Research Institute, 475 Brannan Street, San Francisco, CA 94107, USA
| | - Shanaz H Dairkee
- California Pacific Medical Center Research Institute, 475 Brannan Street, San Francisco, CA 94107, USA
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16
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Huang SY, Fang CY, Wu CC, Tsai CH, Lin SF, Chen JY. Reactive oxygen species mediate Epstein-Barr virus reactivation by N-methyl-N'-nitro-N-nitrosoguanidine. PLoS One 2013; 8:e84919. [PMID: 24376853 PMCID: PMC3869928 DOI: 10.1371/journal.pone.0084919] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Accepted: 11/20/2013] [Indexed: 12/15/2022] Open
Abstract
N-nitroso compounds (NOCs) and Epstein-Barr virus (EBV) reactivation have been suggested to play a role in the development of nasopharyngeal carcinoma (NPC). Although chemicals have been shown to be a risk factor contributing to the carcinogenesis of NPC, the underlying mechanism is not fully understood. We demonstrated recently that N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) enhances the genomic instability and tumorigenicity of NPC cells via induction of EBV reactivation. However, the mechanisms that trigger EBV reactivation from latency remain unclear. Here, we address the role of ROS in induction of EBV reactivation under MNNG treatment. EBV reactivation was induced in over 70% of EBV-positive NA cells and the promoter of Rta (Rp) was activated after MNNG treatment. Inhibitor experiments revealed ATM, p38 MAPK and JNK were activated by ROS and involved in MNNG-induced EBV reactivation. Significantly, ROS scavengers N-acetyl-L-cysteine (NAC), catalase and reduced glutathione inhibited EBV reactivation under MNNG and H₂O₂ treatment, suggesting ROS mediate EBV reactivation. The p53 was essential for EBV reactivation and the Rp activation by MNNG. Moreover, the p53 was phosphorylated, translocated into nucleus, and bound to Rp following ROS stimulation. The results suggest ROS play an important role in initiation of EBV reactivation by MNNG through a p53-dependent mechanism. Our findings demonstrate novel signaling mechanisms used by NOCs to induce EBV reactivation and provide a novel insight into NOCs link the EBV reactivation in the contribution to the development of NPC. Notably, this study indicates that antioxidants might be effective for inhibiting N-nitroso compound-induced EBV reactivation and therefore could be promising preventive and therapeutic agents for EBV reactivation-associated malignancies.
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Affiliation(s)
- Sheng-Yen Huang
- Graduate Program of Biotechnology in Medicine of National Tsing Hua University and National Health Research Institutes, Hsinchu, Taiwan
- Institute of Biotechnology, Department of Life Sciences, National Tsing Hua University, Hsinchu, Taiwan
- National Institute of Cancer Research, National Health Research Institutes, Miaoli County, Taiwan
| | - Chih-Yeu Fang
- National Institute of Cancer Research, National Health Research Institutes, Miaoli County, Taiwan
| | - Chung-Chun Wu
- National Institute of Cancer Research, National Health Research Institutes, Miaoli County, Taiwan
| | - Ching-Hwa Tsai
- Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Su-Fang Lin
- National Institute of Cancer Research, National Health Research Institutes, Miaoli County, Taiwan
| | - Jen-Yang Chen
- Graduate Program of Biotechnology in Medicine of National Tsing Hua University and National Health Research Institutes, Hsinchu, Taiwan
- Department of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan
- National Institute of Cancer Research, National Health Research Institutes, Miaoli County, Taiwan
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17
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Chen X, Zhao Y, Li GM, Guo L. Proteomic analysis of mismatch repair-mediated alkylating agent-induced DNA damage response. Cell Biosci 2013; 3:37. [PMID: 24330662 PMCID: PMC3848634 DOI: 10.1186/2045-3701-3-37] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 08/26/2013] [Indexed: 11/13/2022] Open
Abstract
Background Mediating DNA damage-induced apoptosis is an important genome-maintenance function of the mismatch repair (MMR) system. Defects in MMR not only cause carcinogenesis, but also render cancer cells highly resistant to chemotherapeutics, including alkylating agents. To understand the mechanisms of MMR-mediated apoptosis and MMR-deficiency-caused drug resistance, we analyze a model alkylating agent (N-methyl-N’-nitro-N-nitrosoguanidine, MNNG)-induced changes in protein phosphorylation and abundance in two cell lines, the MMR-proficient TK6 and its derivative MMR-deficient MT1. Results Under an experimental condition that MNNG-induced apoptosis was only observed in MutSα-proficient (TK6), but not in MutSα-deficient (MT1) cells, quantitative analysis of the proteomic data revealed differential expression and phosphorylation of numerous individual proteins and clusters of protein kinase substrates, as well differential activation of response pathways/networks in MNNG-treated TK6 and MT1 cells. Many alterations in TK6 cells are in favor of turning on the apoptotic machinery, while many of those in MT1 cells are to promote cell proliferation and anti-apoptosis. Conclusions Our work provides novel molecular insights into the mechanism of MMR-mediated DNA damage-induced apoptosis.
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18
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Sedletska Y, Culard F, Midoux P, Malinge JM. Interaction studies of muts and mutl with DNA containing the major cisplatin lesion and its mismatched counterpart under equilibrium and nonequilibrium conditions. Biopolymers 2013; 99:636-47. [DOI: 10.1002/bip.22232] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Revised: 02/04/2013] [Accepted: 03/05/2013] [Indexed: 11/12/2022]
Affiliation(s)
| | - Françoise Culard
- Centre de Biophysique Moléculaire; CNRS UPR 4301; affiliated to the University of Orléans and INSERM; rue Charles Sadron, 45071 Orléans Cedex 02; France
| | - Patrick Midoux
- Centre de Biophysique Moléculaire; CNRS UPR 4301; affiliated to the University of Orléans and INSERM; rue Charles Sadron, 45071 Orléans Cedex 02; France
| | - Jean-Marc Malinge
- Centre de Biophysique Moléculaire; CNRS UPR 4301; affiliated to the University of Orléans and INSERM; rue Charles Sadron, 45071 Orléans Cedex 02; France
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19
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Xu JL, Yin ZQ, Huang MD, Wang XF, Gao W, Liu LX, Wang RS, Huang PW, Yin YM, Liu P, Shu YQ. MLH1 polymorphisms and cancer risk: a meta-analysis based on 33 case-control studies. Asian Pac J Cancer Prev 2012; 13:901-7. [PMID: 22631669 DOI: 10.7314/apjcp.2012.13.3.901] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVE Cumulative evidence suggests that MLH1, the key component in the mismatch pathway, plays an important role in human cancers. Two potential functional polymorphisms (-93G>A and I219V) of MLH1 have been implicated in cancer risk. The aim of this meta-analysis was to summarize the evidence for associations. METHODS Eligible studies were identified by searching the electronic literature PubMed, ScienceDirect and Embase databases for relevant reports and bibliographies. Studies were included if of case-control design investigating MLH1 polymorphisms (-93G>A and I219V) and cancer risk with sufficient raw data for analysis. Odds ratios (OR) and 95% confidence intervals (95% CI) were used to evaluate the strength of associations. RESULTS Our meta-analysis from 33 published case-control studies showed the variant A allele of -93G>A polymorphism to be associated with increased risk in all genetic models (AA vs. GG: OR = 1.22, 95% CI: 1.03-1.44), especially among non-Asians (AA vs. GG: OR = 1.28, 95% CI: 1.04-1.58). For the I219V polymorphism, however, there was no main effect associated with overall cancer risk in any genetic model. CONCLUSIONS The meta-analysis suggested that the MLH1 -93G>A polymorphism may be a biomarker of cancer susceptibility. Large sample association studies and assessment of gene-to-gene as well as gene-to-environment interactions are required to confirm these findings.
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Affiliation(s)
- Jia-Li Xu
- Department of Oncology, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
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Plumb JA, Venugopal B, Oun R, Gomez-Roman N, Kawazoe Y, Venkataramanan NS, Wheate NJ. Cucurbit[7]uril encapsulated cisplatin overcomes cisplatin resistance via a pharmacokinetic effect. Metallomics 2012; 4:561-7. [PMID: 22610518 DOI: 10.1039/c2mt20054f] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The cucurbit[n]uril (CB[n]) family of macrocycles has been shown to have potential in drug delivery where they are able to provide physical and chemical stability to drugs, improve drug solubility, control drug release and mask the taste of drugs. Cisplatin is a small molecule platinum-based anticancer drug that has severe dose-limiting side-effects. Cisplatin forms a host-guest complex with cucurbit[7]uril (cisplatin@CB[7]) with the platinum atom and both chlorido ligands located inside the macrocycle, with binding stabilised by four hydrogen bonds (2.15-2.44 Å). Whilst CB[7] has no effect on the in vitro cytotoxicity of cisplatin in the human ovarian carcinoma cell line A2780 and its cisplatin-resistant sub-lines A2780/cp70 and MCP1, there is a significant effect on in vivo cytotoxicity using human tumour xenografts. Cisplatin@CB[7] is just as effective on A2780 tumours compared with free cisplatin, and in the cisplatin-resistant A2780/cp70 tumours cisplatin@CB[7] markedly slows tumour growth. The ability of cisplatin@CB[7] to overcome resistance in vivo appears to be a pharmacokinetic effect. Whilst the peak plasma level and tissue distribution are the same for cisplatin@CB[7] and free cisplatin, the total concentration of circulating cisplatin@CB[7] over a period of 24 hours is significantly higher than for free cisplatin when administered at the equivalent dose. The results provide the first example of overcoming drug resistance via a purely pharmacokinetic effect rather than drug design or better tumour targeting, and demonstrate that in vitro assays are no longer as important in screening advanced systems of drug delivery.
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Affiliation(s)
- Jane A Plumb
- Institute of Cancer Sciences, University of Glasgow, Cancer Research UK Beatson Laboratories, Garscube Estate, Glasgow, G61 1BD, UK.
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de Miranda NFCC, Hes FJ, van Wezel T, Morreau H. Role of the microenvironment in the tumourigenesis of microsatellite unstable and MUTYH-associated polyposis colorectal cancers. Mutagenesis 2012; 27:247-53. [DOI: 10.1093/mutage/ger077] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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22
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Zeller C, Brown R. Therapeutic modulation of epigenetic drivers of drug resistance in ovarian cancer. Ther Adv Med Oncol 2011; 2:319-29. [PMID: 21789144 DOI: 10.1177/1758834010375759] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Epigenetic changes in tumours are associated not only with cancer development and progression, but also with resistance to chemotherapy. Aberrant DNA methylation at CpG islands and associated epigenetic silencing are observed during the acquisition of drug resistance. However, it remains unclear whether all of the observed changes are drivers of drug resistance, causally associated with response of tumours to chemotherapy, or are passenger events representing chance DNA methylation changes. Systematic approaches that link DNA methylation and expression with chemosensitivity will be required to identify key drivers. Such drivers will be important prognostic or predicitive biomarkers, both to existing chemotherapies, but also to epigenetic therapies used to modulate drug resistance.
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Affiliation(s)
- Constanze Zeller
- Department of Oncology, IRDB, Hammersmith Hospital Campus, Imperial College London, Du Cane Road, London W12 0NN, UK
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Yamamoto A, Sakamoto Y, Masumura K, Honma M, Nohmi T. Involvement of mismatch repair proteins in adaptive responses induced by N-methyl-N'-nitro-N-nitrosoguanidine against γ-induced genotoxicity in human cells. Mutat Res 2011; 713:56-63. [PMID: 21704047 DOI: 10.1016/j.mrfmmm.2011.05.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Revised: 05/20/2011] [Accepted: 05/23/2011] [Indexed: 10/18/2022]
Abstract
As humans are exposed to a variety of chemical agents as well as radiation, health effects of radiation should be evaluated in combination with chemicals. To explore combined genotoxic effects of radiation and chemicals, we examined modulating effects of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), a direct-acting methylating agent, against genotoxicity of γ-radiation. Human lymphoblastoid TK6 cells and its mismatch-deficient derivative, i.e., MT1 cells, were treated with MNNG for 24h before they were exposed to γ-irradiation at a dose of 1.0 Gy, and the resulting genotoxicity was examined. In TK6 cells, the pretreatments with MNNG at low doses suppressed frequencies of the thymidine kinase (TK) gene mutation and micronucleus (MN) formation induced by γ-irradiation and thus the dose responses of TK and MN assays were U-shaped along with the pretreatment doses of MNNG. In contrast, the genotoxic effects of MNNG and γ-irradiation were additive in MT1 cells and the frequencies of TK mutations and MN induction increased along with the doses of MNNG. Apoptosis induced by γ-radiation was suppressed by the pretreatments in TK6 cells, but not in MT1 cells. The expression of p53 was induced and cell cycle was delayed at G2/M phase in TK6, but not in MT1 cells, by the treatments with MNNG. These results suggest that pretreatments of MNNG at low doses suppress genotoxicity of γ-radiation in human cells and also that mismatch repair proteins are involved in the apparent adaptive responses.
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Affiliation(s)
- Ayumi Yamamoto
- Division of Genetics and Mutagenesis, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya-ku, Tokyo 158-8501, Japan
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Gupta S, Sathishkumar S, Ahmed MM. Influence of cell cycle checkpoints and p53 function on the toxicity of temozolomide in human pancreatic cancer cells. Pancreatology 2010; 10:565-79. [PMID: 20980775 PMCID: PMC2992636 DOI: 10.1159/000317254] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2009] [Accepted: 06/06/2010] [Indexed: 12/11/2022]
Abstract
BACKGROUND Though an increased efficacy of carmustine and temozolomide (TMZ) has been demonstrated by inactivation of O(6)-methylguanine-DNA methyltransferase (MGMT) with O(6)-benzyl-guanine (BG) in human pancreatic tumors refractive to alkylating agents, the regulatory mechanisms have not been explored. METHODS The effects of TMZ and BG on apoptosis, cell growth, the mitotic index, cell cycle distribution, and protein expression were studied by TUNEL, cell counting, flow cytometry, and Western blot analysis, respectively. RESULTS The wt-p53 human pancreatic tumor cell line Capan-2 and p53-efficient mouse embryonic fibroblasts (MEFs) were more responsive to treatment with TMZ + BG than mutant p53 Capan-1 and p53-null MEFs. S phase delay with a subsequent G2/M arrest was observed in Capans in response to BG + TMZ. The G1-to-S transition delay in Capan-2 was associated with p53-dependent apoptosis and was distinctly different from the presumed mismatch repair (MMR) killing operative during the G2/M arrest. The effect of p53 on BG + TMZ toxicity was supported by a marked change in apoptosis when p53 function was restored/inactivated. There was an early induction of MMR proteins in p53-efficient lines. CONCLUSION p53 provokes a classic proapoptotic response by delaying G1-to-S progression, but it may also facilitate cell killing by enhancing MMR-related cell cycle arrest and cell death.
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Affiliation(s)
- Seema Gupta
- Department of Radiation Oncology, Miller School of Medicine, University of Miami, Miami, Fla., USA,Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, Fla., USA
| | | | - Mansoor M. Ahmed
- Department of Radiation Oncology, Miller School of Medicine, University of Miami, Miami, Fla., USA,Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, Fla., USA,*Mansoor M. Ahmed, PhD, Department of Radiation Oncology, 1475 NW 12th Ave (D-31) Miami, FL 33136 (USA), Tel. +1 305 243 5454, Fax +1 305 243 1854, E-Mail
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Alkyltransferase-like protein (eATL) prevents mismatch repair-mediated toxicity induced by O6-alkylguanine adducts in Escherichia coli. Proc Natl Acad Sci U S A 2010; 107:18050-5. [PMID: 20921378 DOI: 10.1073/pnas.1008635107] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
O(6)-alkylG adducts are highly mutagenic due to their capacity to efficiently form O(6)-alkylG:T mispairs during replication, thus triggering G→A transitions. Mutagenesis is largely prevented by repair strategies such as reversal by alkyltransferases or excision by nucleotide excision repair (NER). Moreover, methyl-directed mismatch repair (MMR) is known to trigger sensitivity to methylating agents via a mechanism that involves recognition by MutS of the O(6)-mG:T replication intermediates. We wanted to investigate the mechanism by which MMR controls the genotoxicity of environmentally relevant O(6)-alkylG adducts formed by ethylene oxide and propylene oxide. Recently, the alkyltransferase-like gene ybaZ (eATL) was shown to enhance repair of these slightly larger O(6)-alkylG adducts by NER. We analyzed the toxicity and mutagenesis induced by these O(6)-alkylG adducts using single-adducted plasmid probes. We show that the eATL gene product prevents MMR-mediated attack of the O(6)-alkylG:T replication intermediate for the larger alkyl groups but not for methyl. In vivo data are compatible with the occurrence of repeated cycles of MMR attack of the O(6)-alkylG:T intermediate. In addition, in vitro, the eATL protein efficiently prevents binding of MutS to the O(6)-alkylG:T mispairs formed by the larger alkyl groups but not by methyl. In conclusion, eATL not only enhances the efficiency of repair of these larger adducts by NER, it also shields these adducts from MMR-mediated toxicity.
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Preston BD, Albertson TM, Herr AJ. DNA replication fidelity and cancer. Semin Cancer Biol 2010; 20:281-93. [PMID: 20951805 PMCID: PMC2993855 DOI: 10.1016/j.semcancer.2010.10.009] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2010] [Accepted: 10/07/2010] [Indexed: 12/14/2022]
Abstract
Cancer is fueled by mutations and driven by adaptive selection. Normal cells avoid deleterious mutations by replicating their genomes with extraordinary accuracy. Here we review the pathways governing DNA replication fidelity and discuss evidence implicating replication errors (point mutation instability or PIN) in carcinogenesis.
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Affiliation(s)
- Bradley D Preston
- Department of Pathology, University of Washington, Seattle, WA 98195, USA.
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Fukui K. DNA mismatch repair in eukaryotes and bacteria. J Nucleic Acids 2010; 2010. [PMID: 20725617 PMCID: PMC2915661 DOI: 10.4061/2010/260512] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Accepted: 06/24/2010] [Indexed: 12/17/2022] Open
Abstract
DNA mismatch repair (MMR) corrects mismatched base pairs mainly caused by DNA replication errors. The fundamental mechanisms and proteins involved in the early reactions of MMR are highly conserved in almost all organisms ranging from bacteria to human. The significance of this repair system is also indicated by the fact that defects in MMR cause human hereditary nonpolyposis colon cancers as well as sporadic tumors. To date, 2 types of MMRs are known: the human type and Escherichia coli type. The basic features of the former system are expected to be universal among the vast majority of organisms including most bacteria. Here, I review the molecular mechanisms of eukaryotic and bacterial MMR, emphasizing on the similarities between them.
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Affiliation(s)
- Kenji Fukui
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan
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28
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Bai H, Madabushi A, Guan X, Lu AL. Interaction between human mismatch repair recognition proteins and checkpoint sensor Rad9-Rad1-Hus1. DNA Repair (Amst) 2010; 9:478-87. [PMID: 20188637 PMCID: PMC2860068 DOI: 10.1016/j.dnarep.2010.01.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 01/04/2010] [Accepted: 01/15/2010] [Indexed: 11/27/2022]
Abstract
In eukaryotic cells, the cell cycle checkpoint proteins Rad9, Rad1, and Hus1 form the 9-1-1 complex which is structurally similar to the proliferating cell nuclear antigen (PCNA) sliding clamp. hMSH2/hMSH6 (hMutS alpha) and hMSH2/hMSH3 (hMutS beta) are the mismatch recognition factors of the mismatch repair pathway. hMutS alpha has been shown to physically and functionally interact with PCNA. Moreover, DNA methylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment induces the G2/M cell cycle arrest that is dependent on the presence of hMutS alpha and hMutL alpha. In this study, we show that each subunit of the human 9-1-1 complex physically interacts with hMSH2, hMSH3, and hMSH6. The 9-1-1 complex from both humans and Schizosaccharomyces pombe can stimulate hMutS alpha binding with G/T-containing DNA. Rad9, Rad1, and Hus1 individual subunits can also stimulate the DNA binding activity of hMutS alpha. Human Rad9 and hMSH6 colocalize to nuclear foci of HeLa cells after exposure to MNNG. However, Rad9 does not form foci in MSH6 defective cells following MNNG treatment. In Rad9 knockdown untreated cells, the majority of the MSH6 is in cytoplasm. Following MNNG treatment, Rad9 knockdown cells has abnormal nuclear morphology and MSH6 is distributed around nuclear envelop. Our findings suggest that the 9-1-1 complex is a component of the mismatch repair involved in MNNG-induced damage response.
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Affiliation(s)
- Haibo Bai
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD 21201, USA
| | - Amrita Madabushi
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD 21201, USA
| | - Xin Guan
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD 21201, USA
| | - A-Lien Lu
- Department of Biochemistry and Molecular Biology, University of Maryland, Baltimore, MD 21201, USA
- Greenebaum Cancer Center, University of Maryland, Baltimore, MD 21201, USA
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Liu Y, Fang Y, Shao H, Lindsey-Boltz L, Sancar A, Modrich P. Interactions of human mismatch repair proteins MutSalpha and MutLalpha with proteins of the ATR-Chk1 pathway. J Biol Chem 2009; 285:5974-82. [PMID: 20029092 PMCID: PMC2820822 DOI: 10.1074/jbc.m109.076109] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
At clinically relevant doses, chemotherapeutic SN1 DNA methylating agents induce an ATR-mediated checkpoint response in human cells that is dependent on functional MutSα and MutLα. Deficiency of either mismatch repair activity renders cells highly resistant to this class of drug, but the mechanisms linking mismatch repair to checkpoint activation have remained elusive. In this study we have systematically examined the interactions of human MutSα and MutLα with proteins of the ATR-Chk1 pathway using both nuclear extracts and purified proteins. Using nuclear co-immunoprecipitation, we have detected interaction of MutSα with ATR, TopBP1, Claspin, and Chk1 and interaction of MutLα with TopBP1 and Claspin. We were unable to detect interaction of MutSα or MutLα with Rad17, Rad9, or replication protein A in the extract system. Use of purified proteins confirmed direct interaction of MutSα with ATR, TopBP1, and Chk1 and of MutLα with TopBP1. MutSα-Claspin and MutLα-Claspin interactions were not demonstrable with purified proteins, suggesting that extract interactions are indirect or depend on post-translational modification. Use of a modified chromatin immunoprecipitation assay showed that proliferating cell nuclear antigen, ATR, TopBP1, and Chk1 are recruited to chromatin in a MutLα- and MutSα-dependent fashion after N-methyl-N′-nitro-N-nitrosoguanidine treatment. However, chromatin enrichment of replication protein A, Claspin, Rad17-RFC, and Rad9-Rad1-Hus1 was not detected in these experiments. Although our failure to observe enrichment of the latter activities could be due to sensitivity limitations, these observations may indicate a novel mechanism for ATR activation.
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Affiliation(s)
- Yiyong Liu
- Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710, USA
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Cooley N, Elder RH, Povey AC. The effect of Msh2 knockdown on methylating agent induced toxicity in DNA glycosylase deficient cells. Toxicology 2009; 268:111-7. [PMID: 20025921 DOI: 10.1016/j.tox.2009.12.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 11/18/2009] [Accepted: 12/10/2009] [Indexed: 01/17/2023]
Abstract
The DNA structure recognition protein MSH2 is an important protein in DNA mismatch repair due to its role in initiating the repair process. To examine the potential interactions between mismatch repair and base excision repair (BER) we have examined the effect of MSH2 knockdown on 6-thioguanine (6-TG), temozolomide (TMZ) and methylmethane sulphonate (MMS) induced toxicity in BER proficient and deficient cell lines. An shRNA expression vector containing Msh2 target sequences was designed and used to transfect mouse embryonic fibroblasts lacking either alkylpurine DNA N-glycosylase (Mpg) or endonuclease III homologue (Nth1). Significant knockdown of Msh2 gene expression was achieved with three different target sequences, with the highest level being shown by Msh2(283). Clonal selection resulted in differing levels of knockdown in Mpg(-/-) cells: (69.0+/-12.1% from 5 cell clones). Transfection of the Msh2(283) sequence in Mpg+/+, Nth1+/+ and Nth1(-/-) cells resulted in average knockdowns of 45.1+/-40.5% (3 clones), 58.0+/-21.4% (5 clones) and 74.9+/-14.8% (3 clones), respectively. Msh2 knockdown resulted in increased resistance to 6-TG in BER (MPG and NTH1) proficient and deficient cell lines with similar levels of knockdown (84+/-4%) but increased resistance to TMZ only in Mpg+/+ and Nth1(-/-) cell lines and not Mpg(-/-) or Nth1+/+ cells as assessed by an MTT assay. Msh2 knockdown had no effect on sensitivity to MMS induced toxicity. In a clonogenic assay, Msh2 silenced Mpg+/+, Mpg(-/-), Nth1+/+ and Nth1(-/-) cells were more resistant to TMZ. These results confirm previous studies showing that MSH2 is a key protein in influencing 6-TG and O(6)-methylguanine induced toxicity but also suggest that the effect of this protein depends upon the presence of other proteins in different DNA repair pathways.
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Affiliation(s)
- N Cooley
- Centre for Occupational and Environmental Health, School of Community Based Medicine, Faculty of Medical and Human Sciences, University of Manchester, Manchester M139PL, United Kingdom
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31
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Paulitschke V, Schicher N, Szekeres T, Jäger W, Elbling L, Riemer AB, Scheiner O, Trimurtulu G, Venkateswarlu S, Mikula M, Swoboda A, Fiebiger E, Gerner C, Pehamberger H, Kunstfeld R. 3,3',4,4',5,5'-hexahydroxystilbene impairs melanoma progression in a metastatic mouse model. J Invest Dermatol 2009; 130:1668-79. [PMID: 19956188 DOI: 10.1038/jid.2009.376] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Stilbenes comprise a group of polyphenolic compounds, which exert inhibitory effects on various malignancies. The aim of this study was to evaluate the antitumor effects of a previously unreported stilbene derivative-3,3',4,4',5,5'-hexahydroxystilbene, termed M8-on human melanoma cells. Cell-cycle analysis of the metastatic melanoma cell line M24met showed that M8 treatment induces G(2)/M arrest accompanied with a dose- and time-dependent upregulation of p21 and downregulation of CDK-2 and leads to apoptosis. M8 induces the expression of phosphorylated p53, proteins involved in the mismatch repair machinery (MSH6, MSH2, and MLH1) and a robust tail moment in a comet assay. In addition, M8 inhibited cell migration in Matrigel assays. Shotgun proteomics and western analysis showed the regulation among others of paxillin, integrin-linked protein kinase, p21-activated kinase, and ROCK-1 indicating that M8 inhibits mesenchymal and amoeboid cell migration. These in vitro data were confirmed in vivo in a metastatic human melanoma severe combined immunodeficient (SCID) mouse model. We showed that M8 significantly impairs tumor growth. M8 also interfered with the metastatic process, as M8 treatment prevented the metastatic spread of melanoma cells to distant lymph nodes in vivo. In summary, M8 exerts strong antitumor effects with the potential to become a new drug for the treatment of metastatic melanoma.
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Affiliation(s)
- Verena Paulitschke
- Department of Dermatology, Medical University of Vienna, Währingergürtel 18-20, Vienna, Austria
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Msh2-dependent DNA repair mitigates a unique susceptibility of B cell progenitors to c-Myc-induced lymphomas. Proc Natl Acad Sci U S A 2009; 106:18698-703. [PMID: 19837692 DOI: 10.1073/pnas.0905965106] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
C-Myc is one of the most common targets of genetic alterations in human cancers. Although overexpression of c-Myc in the B cell compartment predisposes to lymphomas, secondary mutations are required for disease manifestation. In this article, we show that genetic deficiencies causing arrested B cell development and accumulation of B cell progenitors lead to accelerated lymphomagenesis in Emu c-myc transgenic mice. This result suggests that B cell progenitors are more prone than their mature counterparts to developing secondary oncogenic lesions that complement c-Myc in promoting transformation. To investigate the nature of these oncogenic lesions, we examined Emu c-myc mice deficient in mismatch repair function. We report that Msh2(-/-) Emu c-myc and Msh2(G674A/G674A) Emu c-myc mice rapidly succumb to pro-B cell stage lymphomas, indicating that Msh2-dependent mismatch repair function actively suppresses c-Myc-associated oncogenesis during early B cell development.
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Sun G, Jin S, Baskaran R. MMR/c-Abl-dependent activation of ING2/p73alpha signaling regulates the cell death response to N-methyl-N'-nitro-N-nitrosoguanidine. Exp Cell Res 2009; 315:3163-75. [PMID: 19766113 DOI: 10.1016/j.yexcr.2009.09.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Revised: 09/10/2009] [Accepted: 09/10/2009] [Indexed: 01/09/2023]
Abstract
Agents inducing O(6)-methylguanine (O(6)MeG) in DNA such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) are cytotoxic and a deficiency in mismatch repair (MMR) results in lack of sensitivity to this genotoxin (termed alkylation tolerance). Here, we show that ING2, a member of the inhibitor of growth family, is required for cell death induced by MNNG. We further observe that MNNG treatment increases cellular protein levels of ING2 that is dependent on intact MMR function and that MNNG-induced ING2 localizes and associates with p73alpha in the nucleus. Suppression of ING2 by short hairpin RNA (shRNA) in MMR-proficient colorectal cancer cells decreased its sensitivity to MNNG and, in addition, abrogated MNNG-induced stabilization and acetylation of p73alpha. Interestingly, suppression of p73alpha had a greater impact on MNNG-induced cell death than ING2 leading us to conclude that ING2 regulates the cell death response, in part, through p73alpha. Inhibition of c-Abl by STI571 or suppression of c-Abl expression by shRNA blocked ING2 induction and p73alpha acetylation induced by this alkylator. Similarly, suppression of MMR (MLH1) by shRNA abrogated ING2 induction/p73alpha acetylation. Taken together, these results demonstrate that MLH1/c-Abl-dependent activation of ING2>p73alpha signaling regulates cell death triggered by MNNG and further suggests that dysregulation of this event may, in part, be responsible for alkylation tolerance observed in MMR compromised cells.
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Affiliation(s)
- Guoming Sun
- Department of Microbiology and Molecular Genetics, School of Medicine, University of Pittsburgh, E1205 Biomedical Science Tower, Pittsburgh, PA 15261, USA
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Fu Z, Regan K, Zhang L, Muders MH, Thibodeau SN, French A, Wu Y, Kaufmann SH, Lingle WL, Chen J, Tindall DJ. Deficiencies in Chfr and Mlh1 synergistically enhance tumor susceptibility in mice. J Clin Invest 2009; 119:2714-24. [PMID: 19690386 DOI: 10.1172/jci37405] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Accepted: 06/24/2009] [Indexed: 01/17/2023] Open
Abstract
Genetic instability, which leads to an accumulation of various genetic abnormalities, has been considered an essential component of the human neoplasic transformation process. However, the molecular basis of genomic instability during tumorigenesis remains incompletely understood. Growing evidence indicates that checkpoint with forkhead and ring finger domains (CHFR), a recently identified mitotic checkpoint protein, plays an important role in maintaining chromosome integrity and functions as a tumor suppressor. In this study, we used high-throughput technology to conduct gene expression profiling of human colon cancers and found that loss of CHFR expression frequently occurred in colon cancers with high microsatellite instability (MSI-H). Downregulation of CHFR expression was closely associated with overexpression of Aurora A, an important mitotic kinase. Mice with deficiencies in both Chfr and Mlh1 (the gene that encodes the DNA mismatch-repair protein Mlh1) displayed dramatically higher incidence of spontaneous tumors relative to mice deficient for only one of these genes. These results suggest that defects in both Chfr and Mlh1 synergistically increase predisposition to tumorigenesis.
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Affiliation(s)
- Zheng Fu
- Department of Urology, Mayo Clinic College of Medicine, Rochester, Minnesota, USA.
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Sanyal S, De Verdier PJ, Steineck G, Larsson P, Onelöv E, Hemminki K, Kumar R. Polymorphisms in XPD, XPC and the risk of death in patients with urinary bladder neoplasms. Acta Oncol 2009; 46:31-41. [PMID: 17438703 DOI: 10.1080/02841860600812693] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
We conducted a follow-up study on 311 patients with urinary bladder neoplasms to investigate the association of polymorphisms in DNA repair and cell growth regulatory genes with the clinical outcomes of this disease. We found that patients carrying the variant allele of XPD (K751Q) polymorphism were at lower risk of death (p = 0.04) than the noncarriers. Patients that were simultaneous carriers of variant alleles from XPD (K751Q) and XPC (K939Q) polymorphisms, showed lower risk of death than the other patients (p = 0.001). The variant allele carriers of MSH6 (G39E) polymorphism showed a higher risk for highly malignant disease (TaG3 +T1) than the non-carriers (p = 0.03). The variant allele carriers of XRCC1 (R399Q) polymorphism showed lower risk for recurrence (TaG2; p = 0.05) and death (T2+; p = 0.03) after instillation and radiotherapy than the non-carriers. After radiotherapy, an inverse association of the variant allele of OGG1 (S326C) polymorphism was observed with the risk of death (T2 +; p = 0.04). A significant low-risk for stage progression (p = 0.03) was observed in patients carrying the variant allele of H-ras (H27H) polymorphism. Our results are consistent with the notion that the XPD (K751Q) polymorphism either individually or in combination with the XPC (K939Q) polymorphism modulates the risk of death in patients with urinary bladder neoplasms.
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Affiliation(s)
- Somali Sanyal
- Division of Clinical Cancer Epidemiology, Department of Oncology-Pathology, Karolinska Institute, Stockholm, Sweden
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36
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Martinez P, Siegl-Cachedenier I, Flores JM, Blasco MA. MSH2 deficiency abolishes the anticancer and pro-aging activity of short telomeres. Aging Cell 2009; 8:2-17. [PMID: 18986375 DOI: 10.1111/j.1474-9726.2008.00441.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Mutations in the mismatch repair (MMR) pathway occur in human colorectal cancers with microsatellite instability. Mounting evidence suggests that cell-cycle arrest in response to a number of cellular stresses, including telomere shortening, is a potent anticancer barrier. The telomerase-deficient mouse model illustrates the anticancer effect of cell-cycle arrest provoked by short telomeres. Here, we describe a role for the MMR protein, MSH2, in signaling cell-cycle arrest in a p21/p53-dependent manner in response to short telomeres in the context of telomerasedeficient mice. In particular, progressively shorter telomeres at successive generations of MSH2(-/-) Terc(-/--) mice did not suppress cancer in these mice, indicating that MSH2 deficiency abolishes the tumor suppressor activity of short telomeres. Interestingly, MSH2 deficiency prevented degenerative pathologies in the gastrointestinal tract of MSH2(-/-) Terc(-/-) mice concomitant with a rescue of proliferative defects. The abolishment of the anticancer and pro-aging effects of short telomeres provoked by MSH2 abrogation was independent of changes in telomere length. These results highlight a role for MSH2 in the organismal response to dysfunctional telomeres, which in turn may be important in the pathobiology of human cancers bearing mutations in the MMR pathway.
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O6-methylguanine-induced cell death involves exonuclease 1 as well as DNA mismatch recognition in vivo. Proc Natl Acad Sci U S A 2009; 106:576-81. [PMID: 19124772 DOI: 10.1073/pnas.0811991106] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Alkylation-induced O(6)-methylguanine (O(6)MeG) DNA lesions can be mutagenic or cytotoxic if unrepaired by the O(6)MeG-DNA methyltransferase (Mgmt) protein. O(6)MeG pairs with T during DNA replication, and if the O(6)MeG:T mismatch persists, a G:C to A:T transition mutation is fixed at the next replication cycle. O(6)MeG:T mismatch detection by MutSalpha and MutLalpha leads to apoptotic cell death, but the mechanism by which this occurs has been elusive. To explore how mismatch repair mediates O(6)MeG-dependent apoptosis, we used an Mgmt-null mouse model combined with either the Msh6-null mutant (defective in mismatch recognition) or the Exo1-null mutant (impaired in the excision step of mismatch repair). Mouse embryonic fibroblasts and bone marrow cells derived from Mgmt-null mice were much more alkylation-sensitive than wild type, as expected. However, ablation of either Msh6 or Exo1 function rendered these Mgmt-null cells just as resistant to alkylation-induced cytotoxicity as wild-type cells. Rapidly proliferating tissues in Mgmt-null mice (bone marrow, thymus, and spleen) are extremely sensitive to apoptosis induced by O(6)MeG-producing agents. Here, we show that ablation of either Msh6 or Exo1 function in the Mgmt-null mouse renders these rapidly proliferating tissues alkylation-resistant. However, whereas the Msh6 defect confers total alkylation resistance, the Exo1 defect leads to a variable tissue-specific alkylation resistance phenotype. Our results indicate that Exo1 plays an important role in the induction of apoptosis by unrepaired O(6)MeGs.
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38
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Siehler SY, Schrauder M, Gerischer U, Cantor S, Marra G, Wiesmüller L. Human MutL-complexes monitor homologous recombination independently of mismatch repair. DNA Repair (Amst) 2008; 8:242-52. [PMID: 19022408 DOI: 10.1016/j.dnarep.2008.10.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Revised: 09/10/2008] [Accepted: 10/21/2008] [Indexed: 12/19/2022]
Abstract
The role of mismatch repair proteins has been well studied in the context of DNA repair following DNA polymerase errors. Particularly in yeast, MSH2 and MSH6 have also been implicated in the regulation of genetic recombination, whereas MutL homologs appeared to be less important. So far, little is known about the role of the human MutL homolog hMLH1 in recombination, but recently described molecular interactions suggest an involvement. To identify activities of hMLH1 in this process, we applied an EGFP-based assay for the analysis of different mechanisms of DNA repair, initiated by a targeted double-stranded DNA break. We analysed 12 human cellular systems, differing in the hMLH1 and concomitantly in the hPMS1 and hPMS2 status via inducible protein expression, genetic reconstitution, or RNA interference. We demonstrate that hMLH1 and its complex partners hPMS1 and hPMS2 downregulate conservative homologous recombination (HR), particularly when involving DNA sequences with only short stretches of uninterrupted homology. Unexpectedly, hMSH2 is dispensable for this effect. Moreover, the damage-signaling kinase ATM and its substrates BLM and BACH1 are not strictly required, but the combined effect of ATM/ATR-signaling components may mediate the anti-recombinogenic effect. Our data indicate a protective role of hMutL-complexes in a process which may lead to detrimental genome rearrangements, in a manner which does not depend on mismatch repair.
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Liu A, Yoshioka KI, Salerno V, Hsieh P. The mismatch repair-mediated cell cycle checkpoint response to fluorodeoxyuridine. J Cell Biochem 2008; 105:245-54. [PMID: 18543256 DOI: 10.1002/jcb.21824] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The loss of DNA mismatch repair (MMR) is responsible for hereditary nonpolyposis colorectal cancer and a subset of sporadic tumors. Acquired resistance or tolerance to some anti-cancer drugs occurs when MMR function is impaired. 5-Fluorouracil (FU), an anti-cancer drug used in the treatment of advanced colorectal and other cancers, and its metabolites are incorporated into RNA and DNA and inhibit thymidylate synthase resulting in depletion of dTTP and incorporation in DNA of uracil. Although the MMR deficiency has been implicated in tolerance to FU, the mechanism of cell killing remains unclear. Here, we examine the cellular response to fluorodeoxyuridine (FdU) and the role of the MMR system. After brief exposure of cells to low doses of FdU, MMR mediates DNA damage signaling during S-phase and triggers arrest in G2/M in the first cell cycle in a manner requiring MutSalpha, MutLalpha, and DNA replication. Cell cycle arrest is mediated by ATR kinase and results in phosphorylation of Chk1 and SMC1. MutSalpha binds FdU:G mispairs in vitro consistent with its being a DNA damage sensor. Prolonged treatment with FdU results in an irreversible arrest in G2 that is independent of MMR status and leads to the accumulation of DNA lesions that are targeted by the base excision repair (BER) pathway. Thus, MMR can act as a direct sensor of FdU-mediated DNA lesions eliciting cell cycle arrest via the ATR/Chk1 pathway. However, at higher levels of damage, other damage surveillance pathways such as BER also play important roles.
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Affiliation(s)
- Angen Liu
- Genetics & Biochemistry Branch, National Institute of Diabetes & Digestive & Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA
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40
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Castro MAA, Dalmolin RJS, Moreira JCF, Mombach JCM, de Almeida RMC. Evolutionary origins of human apoptosis and genome-stability gene networks. Nucleic Acids Res 2008; 36:6269-83. [PMID: 18832373 PMCID: PMC2577361 DOI: 10.1093/nar/gkn636] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Apoptosis is essential for complex multicellular organisms and its failure is associated with genome instability and cancer. Interactions between apoptosis and genome-maintenance mechanisms have been extensively documented and include transactivation-independent and -dependent functions, in which the tumor-suppressor protein p53 works as a 'molecular node' in the DNA-damage response. Although apoptosis and genome stability have been identified as ancient pathways in eukaryote phylogeny, the biological evolution underlying the emergence of an integrated system remains largely unknown. Here, using computational methods, we reconstruct the evolutionary scenario that linked apoptosis with genome stability pathways in a functional human gene/protein association network. We found that the entanglement of DNA repair, chromosome stability and apoptosis gene networks appears with the caspase gene family and the antiapoptotic gene BCL2. Also, several critical nodes that entangle apoptosis and genome stability are cancer genes (e.g. ATM, BRCA1, BRCA2, MLH1, MSH2, MSH6 and TP53), although their orthologs have arisen in different points of evolution. Our results demonstrate how genome stability and apoptosis were co-opted during evolution recruiting genes that merge both systems. We also provide several examples to exploit this evolutionary platform, where we have judiciously extended information on gene essentiality inferred from model organisms to human.
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Affiliation(s)
- Mauro A A Castro
- Bioinformatics Unit, Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Rua Ramiro Barcelos 2600-anexo, Porto Alegre 90035-003, Brazil.
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41
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Genomic and epigenetic instability in colorectal cancer pathogenesis. Gastroenterology 2008; 135:1079-99. [PMID: 18773902 PMCID: PMC2866182 DOI: 10.1053/j.gastro.2008.07.076] [Citation(s) in RCA: 680] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2008] [Revised: 07/07/2008] [Accepted: 07/28/2008] [Indexed: 12/11/2022]
Abstract
Colorectal cancer arises as a consequence of the accumulation of genetic alterations (gene mutations, gene amplification, and so on) and epigenetic alterations (aberrant DNA methylation, chromatin modifications, and so on) that transform colonic epithelial cells into colon adenocarcinoma cells. The loss of genomic stability and resulting gene alterations are key molecular pathogenic steps that occur early in tumorigenesis; they permit the acquisition of a sufficient number of alterations in tumor suppressor genes and oncogenes that transform cells and promote tumor progression. Two predominant forms of genomic instability that have been identified in colon cancer are microsatellite instability and chromosome instability. Substantial progress has been made to identify causes of chromosomal instability in colorectal cells and to determine the effects of the different forms of genomic instability on the biological and clinical behavior of colon tumors. In addition to genomic instability, epigenetic instability results in the aberrant methylation of tumor suppressor genes. Determining the causes and roles of genomic and epigenomic instability in colon tumor formation has the potential to yield more effective prevention strategies and therapeutics for patients with colorectal cancer.
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42
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Ohno K, Ishihata K, Tanaka-Azuma Y, Yamada T. A genotoxicity test system based on p53R2 gene expression in human cells: Assessment of its reactivity to various classes of genotoxic chemicals. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2008; 656:27-35. [DOI: 10.1016/j.mrgentox.2008.07.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Revised: 05/31/2008] [Accepted: 07/05/2008] [Indexed: 01/26/2023]
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McDowell HD, Carney JP, Wilson TM. Inhibition of the 5' to 3' exonuclease activity of hEXO1 by 8-oxoguanine. ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2008; 49:388-398. [PMID: 18418867 DOI: 10.1002/em.20398] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The mismatch repair pathway is responsible for maintaining genomic stability by correcting base-base mismatches and insertion/deletion loops that arise mainly via replication errors. Additionally, the mismatch repair pathway performs a central role in the cellular response to both alkylation and reactive oxygen species induced DNA damage. An important step in mismatch processing is the recruitment of hEXO1, a 5' to 3' exonuclease, by hMSH2-hMSH6 to remove the nascent DNA strand. However, very little is currently known about the capacity of hEXO1 to exonucleolytically process damaged DNA bases. Therefore, we examined whether hEXO1 can degrade double-stranded DNA substrates containing alkylated or oxidized nucleotides. Our results demonstrated that hEXO1 is capable of degrading duplex DNA containing an O6-methylguanine (O6-meG) adduct paired with either a C or a T. Additionally, the hMSH2-hMSH6 complex stimulated hEXO1 exonuclease activity on the O6-meG/T and O6-meG/C DNA substrates. In contrast, hEXO1 exonuclease activity was significantly blocked by the presence of an 8-oxoguanine adduct in both single and double stranded DNA substrates. Further, hMSH2-hMSH6 was not able to alleviate the nucleolytic block caused by the 8-oxoguanine adduct in heteroduplex DNA.
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Affiliation(s)
- Heather D McDowell
- Department of Radiation Oncology, Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland, USA
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44
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Wagner MW, Li LS, Morales JC, Galindo CL, Garner HR, Bornmann WG, Boothman DA. Role of c-Abl kinase in DNA mismatch repair-dependent G2 cell cycle checkpoint arrest responses. J Biol Chem 2008; 283:21382-93. [PMID: 18480061 DOI: 10.1074/jbc.m709953200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Current published data suggest that DNA mismatch repair (MMR) triggers prolonged G(2) cell cycle checkpoint arrest after alkylation damage from N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) by activating ATR (ataxia telangiectasia-Rad3-related kinase). However, analyses of isogenic MMR-proficient and MMR-deficient human RKO colon cancer cells revealed that although ATR/Chk1 signaling controlled G(2) arrest in MMR-deficient cells, ATR/Chk1 activation was not involved in MMR-dependent G(2) arrest. Instead, we discovered that disrupting c-Abl activity using STI571 (Gleevec, a c-Abl inhibitor) or stable c-Abl knockdown abolished MMR-dependent p73alpha stabilization, induction of GADD45alpha protein expression, and G(2) arrest. In addition, inhibition of c-Abl also increased the survival of MNNG-exposed MMR-proficient cells to a level comparable with MMR-deficient cells. Furthermore, knocking down GADD45alpha (but not p73alpha) protein levels affected MMR-dependent G(2) arrest responses. Thus, MMR-dependent G(2) arrest responses triggered by MNNG are dependent on a human MLH1/c-Abl/GADD45alpha signaling pathway and activity. Furthermore, our data suggest that caution should be taken with therapies targeting c-Abl kinase because increased survival of mutator phenotypes may be an unwanted consequence.
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Affiliation(s)
- Mark W Wagner
- Laboratory of Molecular Stress Responses, Program in Cell Stress and Cancer Nanomedicine, Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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45
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Li LS, Morales JC, Hwang A, Wagner MW, Boothman DA. DNA mismatch repair-dependent activation of c-Abl/p73alpha/GADD45alpha-mediated apoptosis. J Biol Chem 2008; 283:21394-403. [PMID: 18480060 DOI: 10.1074/jbc.m709954200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Cells with functional DNA mismatch repair (MMR) stimulate G(2) cell cycle checkpoint arrest and apoptosis in response to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). MMR-deficient cells fail to detect MNNG-induced DNA damage, resulting in the survival of "mutator" cells. The retrograde (nucleus-to-cytoplasm) signaling that initiates MMR-dependent G(2) arrest and cell death remains undefined. Since MMR-dependent phosphorylation and stabilization of p53 were noted, we investigated its role(s) in G(2) arrest and apoptosis. Loss of p53 function by E6 expression, dominant-negative p53, or stable p53 knockdown failed to prevent MMR-dependent G(2) arrest, apoptosis, or lethality. MMR-dependent c-Abl-mediated p73alpha and GADD45alpha protein up-regulation after MNNG exposure prompted us to examine c-Abl/p73alpha/GADD45alpha signaling in cell death responses. STI571 (Gleevec, a c-Abl tyrosine kinase inhibitor) and stable c-Abl, p73alpha, and GADD45alpha knockdown prevented MMR-dependent apoptosis. Interestingly, stable p73alpha knockdown blocked MMR-dependent apoptosis, but not G(2) arrest, thereby uncoupling G(2) arrest from lethality. Thus, MMR-dependent intrinsic apoptosis is p53-independent, but stimulated by hMLH1/c-Abl/p73alpha/GADD45alpha retrograde signaling.
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Affiliation(s)
- Long Shan Li
- Laboratory of Molecular Stress Responses, Department of Oncology, Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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46
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Lee CH, Inoki K, Karbowniczek M, Petroulakis E, Sonenberg N, Henske EP, Guan KL. Constitutive mTOR activation in TSC mutants sensitizes cells to energy starvation and genomic damage via p53. EMBO J 2007; 26:4812-23. [PMID: 17962806 PMCID: PMC2099465 DOI: 10.1038/sj.emboj.7601900] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2007] [Accepted: 09/27/2007] [Indexed: 12/15/2022] Open
Abstract
Miscoordination of growth and proliferation with the cellular stress response can lead to tumorigenesis. Mammalian target of rapamycin (mTOR), a central cell growth controller, is highly activated in some malignant neoplasms, and its clinical implications are under extensive investigation. We show that constitutive mTOR activity amplifies p53 activation, in vitro and in vivo, by stimulating p53 translation. Thus, loss of TSC1 or TSC2, the negative regulators of mTOR, results in dramatic accumulation of p53 and apoptosis in response to stress conditions. In other words, the inactivation of mTOR prevents cell death by nutrient stress and genomic damage via p53. Consistently, we also show that p53 is elevated in TSC tumors, which rarely become malignant. The coordinated relationship between mTOR and p53 during cellular stress provides a possible explanation for the benign nature of hamartoma syndromes, including TSC. Clinically, this also suggests that the efficacy of mTOR inhibitors in anti-neoplastic therapy may also depend on p53 status, and mTOR inhibitors may antagonize the effects of genotoxic chemotherapeutics.
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Affiliation(s)
- Chung-Han Lee
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
| | - Ken Inoki
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
| | | | - Emmanuel Petroulakis
- Department of Biochemistry and McGill Cancer Center, McGill University, Montreal, Quebec, Canada
| | - Nahum Sonenberg
- Department of Biochemistry and McGill Cancer Center, McGill University, Montreal, Quebec, Canada
| | | | - Kun-Liang Guan
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
- Institute of Gerontology, University of Michigan, Ann Arbor, MI, USA
- Present address: Department of Pharmacology and Moores Cancer Center, University of California at San Diego, La Jolla, CA 92093, USA
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47
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Siegl-Cachedenier I, Muñoz P, Flores JM, Klatt P, Blasco MA. Deficient mismatch repair improves organismal fitness and survival of mice with dysfunctional telomeres. Genes Dev 2007; 21:2234-47. [PMID: 17785530 PMCID: PMC1950861 DOI: 10.1101/gad.430107] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Mismatch repair (MMR) has important roles in meiotic and mitotic recombination, DNA damage signaling, and various aspects of DNA metabolism including class-switch recombination, somatic hypermutation, and triplet-repeat expansion. Defects in MMR are responsible for human cancers characterized by microsatellite instability. Intriguingly, MMR deficiency has been shown to rescue survival and proliferation of telomerase-deficient yeast strains. A putative role for MMR at mammalian telomeres that could have an impact on cancer and aging is, however, unknown. Here, we studied the role of MMR in response to dysfunctional telomeres by generating mice doubly deficient for telomerase and the PMS2 MMR gene (Terc-/-/PMS2-/- mice). PMS2 deficiency prolonged the mean lifespan and median survival of telomerase-deficient mice concomitant with rescue of degenerative pathologies. This rescue of survival was independent of changes in telomere length, in sister telomere recombination, and in microsatellite instability. Importantly, PMS2 deficiency rescued cell proliferation defects but not apoptotic defects in vivo, concomitant with a decreased p21 induction in response to short telomeres. The proliferative advantage conferred to telomerase-deficient cells by the ablation of PMS2 did not produce increased tumors. Indeed, Terc-/-/PMS2-/- mice showed reduced tumors compared with PMS2-/- mice, in agreement with a tumor suppressor role for short telomeres in the context of MMR deficiencies. These results highlight an unprecedented role for MMR in mediating the cellular response to dysfunctional telomeres in vivo by attenuating p21 induction.
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Affiliation(s)
- Irene Siegl-Cachedenier
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Madrid 28029, Spain
| | - Purificación Muñoz
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Madrid 28029, Spain
| | - Juana M. Flores
- Animal Surgery and Medicine Department, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid 28040, Spain
| | - Peter Klatt
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Madrid 28029, Spain
| | - María A. Blasco
- Telomeres and Telomerase Group, Molecular Oncology Program, Spanish National Cancer Centre (CNIO), Madrid 28029, Spain
- Corresponding author.E-MAIL ; FAX +34-917328028
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48
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An Y, Jin G, Wang H, Wang Y, Liu H, Li R, Wang H, Qian J, Sun W, Wang Y, Ma H, Miao R, Hu Z, Jin L, Wei Q, Shen H, Huang W, Lu D. Polymorphisms in hMLH1 and risk of early-onset lung cancer in a southeast Chinese population. Lung Cancer 2007; 59:164-70. [PMID: 17870204 DOI: 10.1016/j.lungcan.2007.08.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 07/27/2007] [Accepted: 08/06/2007] [Indexed: 02/07/2023]
Abstract
DNA mismatch repair (MMR) plays an important role in maintaining genome stability. Defects in MMR genes have been involved in several types of sporadic and hereditary cancers. hMLH1 is considered one of central members of the MMR pathway. We conducted a hospital-based case-control study to investigate associations of common variations in the hMLH1 gene and risk of lung cancer. A total of 500 cases and 517 controls were genotyped for seven SNPs in hMLH1. Overall, the rs1799977 I219V polymorphism was marginally associated with the risk of lung cancer (P=0.055). This association was much stronger in younger patients (P=0.01; odds ratio, 5.28; 95% CI 1.45-19.21) and lung squamous cell carcinoma (P=0.006; odds ratio, 3.65; 95% CI 1.44-9.24). These findings indicate that the hMLH1 rs1799977 polymorphism may contribute to the etiology of early-onset lung cancer as well as some specific subtype of lung cancer. Larger association studies are warranted to validate our findings and mechanistic studies are needed to elucidate the underlying molecular mechanisms of the association.
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Affiliation(s)
- Yu An
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Fudan University, Handan Road, Shanghai 200433, China
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49
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Young LC, Keuling AM, Lai R, Nation PN, Tron VA, Andrew SE. The associated contributions of p53 and the DNA mismatch repair protein Msh6 to spontaneous tumorigenesis. Carcinogenesis 2007; 28:2131-8. [PMID: 17615258 DOI: 10.1093/carcin/bgm153] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
DNA mismatch repair (MMR) is a highly conserved system that repairs DNA adducts acquired during replication, as well as some forms of exogenous/endogenous DNA damage. Additionally, MMR proteins bind to DNA adducts that are not removed by MMR and influence damage-response mechanisms other than repair. Hereditary non-polyposis colorectal cancer, as well as mouse models for MMR deficiency, illustrate that MMR proteins are required for maintenance of genetic stability and tumor suppression. In both humans and mice, the phenotype associated with Msh6-associated tumorigenesis is distinct from that of Msh2. In this study, we hypothesized that Msh6-/-;p53+/- mice would display earlier tumor onset than their Msh6-/- or p53+/- counterparts, indicating that concomitant loss of these two tumor suppressors contributes to tumorigenesis via mechanisms that are only partially interrelated. We generated a Msh6-/-;p53+/- mouse model which succumbed to malignant disease at an accelerated rate and with a tumor spectrum distinct from both Msh6-/- and p53+/- models. Alteration of tumor phenotype in the Msh6-/-;p53+/- mice included a marked increase in microsatellite instability that was associated with loss of heterozygosity of the remaining p53 allele. Also, genetic instability was inversely correlated with survival. This manuscript marks the first in vivo investigation into the association between Msh6 and p53, and their combined role in the suppression of spontaneous tumorigenesis, cell survival and genomic stability. Our results support the hypothesis that p53 and Msh6 are functionally interrelated and that, with concomitant mutation, these tumor suppressors act together to accelerate tumorigenesis.
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Affiliation(s)
- Leah C Young
- Department of Medical Genetics, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
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50
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Schroering AG, Edelbrock MA, Richards TJ, Williams KJ. The cell cycle and DNA mismatch repair. Exp Cell Res 2006; 313:292-304. [PMID: 17157834 DOI: 10.1016/j.yexcr.2006.10.018] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2006] [Revised: 10/13/2006] [Accepted: 10/16/2006] [Indexed: 11/22/2022]
Abstract
The DNA mismatch repair (MMR) pathway contributes to the fidelity of DNA synthesis and recombination by correcting mispaired nucleotides and insertion/deletion loops (IDLs). We have investigated whether MMR protein expression, activity, and subcellular location are altered during discrete phases of the cell cycle in mammalian cells. Two distinct methods have been used to demonstrate that although physiological MMR protein expression, mismatch binding, and nick-directed MMR activity within the nucleus are at highest levels during S phase, MMR is active throughout the cell cycle. Despite equal MMR nuclear protein concentrations in S and G(2) phases, mismatch binding and repair activities within G(2) are significantly lower, indicating a post-translational decrease in MMR activity specific to G(2). We further demonstrate that typical co-localization of MutSalpha to late S phase replication foci can be disrupted by 2 microM N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). This concentration of MNNG does not decrease ongoing DNA synthesis nor induce cell cycle arrest until the second cell cycle, with long-term colony survival decreased by only 24%. These results suggest that low level alkylation damage can selectively disrupt MMR proofreading activity during DNA synthesis and potentially increase mutation frequency within surviving cells.
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Affiliation(s)
- Allen G Schroering
- Department of Biochemistry and Cancer Biology, Medical University of Ohio, Toledo, OH 43614-5804, USA
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