1
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Lockwood N, Martini S, Lopez-Pardo A, Deiss K, Segeren HA, Semple RK, Collins I, Repana D, Cobbaut M, Soliman T, Ciccarelli F, Parker PJ. Genome-Protective Topoisomerase 2a-Dependent G2 Arrest Requires p53 in hTERT-Positive Cancer Cells. Cancer Res 2022; 82:1762-1773. [PMID: 35247890 PMCID: PMC7612711 DOI: 10.1158/0008-5472.can-21-1785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Revised: 02/01/2022] [Accepted: 02/25/2022] [Indexed: 11/16/2022]
Abstract
Topoisomerase 2a (Topo2a)-dependent G2 arrest engenders faithful segregation of sister chromatids, yet in certain tumor cell lines where this arrest is dysfunctional, a PKCε-dependent failsafe pathway can be triggered. Here we elaborate on recent advances in understanding the underlying mechanisms associated with this G2 arrest by determining that p53-p21 signaling is essential for efficient arrest in cell lines, in patient-derived cells, and in colorectal cancer organoids. Regulation of this p53 axis required the SMC5/6 complex, which is distinct from the p53 pathways observed in the DNA damage response. Topo2a inhibition specifically during S phase did not trigger G2 arrest despite affecting completion of DNA replication. Moreover, in cancer cells reliant upon the alternative lengthening of telomeres (ALT) mechanism, a distinct form of Topo2a-dependent, p53-independent G2 arrest was found to be mediated by BLM and Chk1. Importantly, the previously described PKCε-dependent mitotic failsafe was engaged in hTERT-positive cells when Topo2a-dependent G2 arrest was dysfunctional and where p53 was absent, but not in cells dependent on the ALT mechanism. In PKCε knockout mice, p53 deletion elicited tumors were less aggressive than in PKCε-replete animals and exhibited a distinct pattern of chromosomal rearrangements. This evidence suggests the potential of exploiting synthetic lethality in arrest-defective hTERT-positive tumors through PKCε-directed therapeutic intervention. SIGNIFICANCE The identification of a requirement for p53 in stringent Topo2a-dependent G2 arrest and engagement of PKCε failsafe pathways in arrest-defective hTERT-positive cells provides a therapeutic opportunity to induce selective synthetic lethality.
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Affiliation(s)
- Nicola Lockwood
- Protein Phosphorylation Laboratory, The Francis Crick Institute, 1 Midland Road, London, UK
| | - Silvia Martini
- Protein Phosphorylation Laboratory, The Francis Crick Institute, 1 Midland Road, London, UK
| | - Ainara Lopez-Pardo
- Protein Phosphorylation Laboratory, The Francis Crick Institute, 1 Midland Road, London, UK
| | - Katharina Deiss
- Protein Phosphorylation Laboratory, The Francis Crick Institute, 1 Midland Road, London, UK
| | - Hendrika A Segeren
- Protein Phosphorylation Laboratory, The Francis Crick Institute, 1 Midland Road, London, UK
| | - Robert K Semple
- Centre for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
| | - Ian Collins
- Division of Cancer Therapeutics, The Institute of Cancer Research, London, UK
| | - Dimitra Repana
- Cancer Systems Biology Laboratory, The Francis Crick Institute, London, UK.,School of Cancer and Pharmaceutical Sciences King's College London, New Hunt's House, Guy's Campus, London, UK
| | - Mathias Cobbaut
- Protein Phosphorylation Laboratory, The Francis Crick Institute, 1 Midland Road, London, UK
| | - Tanya Soliman
- Barts Cancer Institute, Queen Mary University London, Charterhouse Square, London, UK
| | - Francesca Ciccarelli
- Cancer Systems Biology Laboratory, The Francis Crick Institute, London, UK.,School of Cancer and Pharmaceutical Sciences King's College London, New Hunt's House, Guy's Campus, London, UK
| | - Peter J Parker
- Protein Phosphorylation Laboratory, The Francis Crick Institute, 1 Midland Road, London, UK.,School of Cancer and Pharmaceutical Sciences King's College London, New Hunt's House, Guy's Campus, London, UK
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2
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Yu C, Hu J, Luyten W, Sun D, Jiang T. Identification of novel topoisomerase II alpha inhibitors by virtual screening, molecular docking, and bioassay. Chem Biol Drug Des 2021; 99:92-102. [PMID: 34310071 DOI: 10.1111/cbdd.13927] [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: 04/10/2021] [Revised: 06/21/2021] [Accepted: 07/03/2021] [Indexed: 11/27/2022]
Abstract
Breast cancer is one of the most common tumors, and its treatment still leaves room for improvement. Topoisomerase II alpha is a potential target for the treatment of human diseases such as breast cancer. In this article, we attempted to discover a novel anticancer drug. We have used the topoisomerase II alpha protein-Homo sapiens (Human) to hierarchically screen the Maybridge database. Based on their docking score, the top hit compounds have been assayed for inhibition in a topoisomerase II pBR322 DNA relaxation assay in vitro. Candidate compound 6 (CP6) was found to have the best inhibitory effect for topoisomerase II among the 20 tested compounds. In addition, CP6 had potent cytotoxicity against eight tested tumor cell lines. At the same time, CP6 was shown to have potential anti-multidrug resistance capabilities. This study identifies CP6, which can contribute to the development of new topoisomerase II inhibitors as anticancer agents.
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Affiliation(s)
- Che Yu
- Department of Nephrology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, China
| | - Jiabao Hu
- School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Walter Luyten
- Animal Physiology and Neurobiology Section, Department of Biology, KU Leuven, Leuven, Belgium
| | - Dan Sun
- Animal Physiology and Neurobiology Section, Department of Biology, KU Leuven, Leuven, Belgium.,College of Life Sciences, Nankai University, Tianjin, China
| | - Tao Jiang
- Department of Anesthesiology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China
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3
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Finardi A, Massari LF, Visintin R. Anaphase Bridges: Not All Natural Fibers Are Healthy. Genes (Basel) 2020; 11:genes11080902. [PMID: 32784550 PMCID: PMC7464157 DOI: 10.3390/genes11080902] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 08/04/2020] [Accepted: 08/05/2020] [Indexed: 02/07/2023] Open
Abstract
At each round of cell division, the DNA must be correctly duplicated and distributed between the two daughter cells to maintain genome identity. In order to achieve proper chromosome replication and segregation, sister chromatids must be recognized as such and kept together until their separation. This process of cohesion is mainly achieved through proteinaceous linkages of cohesin complexes, which are loaded on the sister chromatids as they are generated during S phase. Cohesion between sister chromatids must be fully removed at anaphase to allow chromosome segregation. Other (non-proteinaceous) sources of cohesion between sister chromatids consist of DNA linkages or sister chromatid intertwines. DNA linkages are a natural consequence of DNA replication, but must be timely resolved before chromosome segregation to avoid the arising of DNA lesions and genome instability, a hallmark of cancer development. As complete resolution of sister chromatid intertwines only occurs during chromosome segregation, it is not clear whether DNA linkages that persist in mitosis are simply an unwanted leftover or whether they have a functional role. In this review, we provide an overview of DNA linkages between sister chromatids, from their origin to their resolution, and we discuss the consequences of a failure in their detection and processing and speculate on their potential role.
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Affiliation(s)
- Alice Finardi
- Department of Experimental Oncology, IEO, European Institute of Oncology IRCCS, 20139 Milan, Italy;
| | - Lucia F. Massari
- The Wellcome Centre for Cell Biology, Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3BF, UK;
| | - Rosella Visintin
- Department of Experimental Oncology, IEO, European Institute of Oncology IRCCS, 20139 Milan, Italy;
- Correspondence: ; Tel.: +39-02-5748-9859; Fax: +39-02-9437-5991
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4
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Khoury L, Zalko D, Audebert M. Evaluation of the genotoxic potential of apoptosis inducers with the γH2AX assay in human cells. Mutat Res 2020; 852:503165. [PMID: 32265046 DOI: 10.1016/j.mrgentox.2020.503165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 02/26/2020] [Accepted: 02/28/2020] [Indexed: 11/19/2022]
Abstract
Human risk assessment of genotoxic chemicals is an important area of research. However, the specificity of in vitro mammalian genotoxicity assays is sometime low, as they yield to misleading positive results that are not observe in in vivo studies. Apoptosis can be a confounding factor in the interpretation of the results. Recently, a new strategy for genotoxicity screening, based on the combined analysis of phosphorylated histones H2AX (γH2AX) and H3 (pH3), was proposed to discriminate efficiently aneugenic from clastogenic compounds. However, γH2AX biomarker could also be induce by apoptosis. The aim of the present study was to investigate the specificity of this genotoxic biomarker. For this purpose, we analyzed 26 compounds inducing apoptosis by different mechanism of action, with the γH2AX assay in three human cell lines after 24 h treatment. Most of the tested chemicals were negative in the assay, whatever the cell line tested. The few compounds that generated positive data have also been report positive in other genotoxicity assays. The data presented here demonstrate that the γH2AX assay is not vulnerable to the generation of misleading positive results by apoptosis inducers. Currently, no formal guidelines have been approve for the γH2AX assay for regular genotoxicity studies, but we suggest that this biomarker could be used as a new standard genotoxicity assay.
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Affiliation(s)
- Laure Khoury
- Toxalim, Université de Toulouse, INRAE, INP-ENVT, INP-EI-Purpan, Université de Toulouse 3 Paul Sabatier, Toulouse, France
| | - Daniel Zalko
- Toxalim, Université de Toulouse, INRAE, INP-ENVT, INP-EI-Purpan, Université de Toulouse 3 Paul Sabatier, Toulouse, France
| | - Marc Audebert
- Toxalim, Université de Toulouse, INRAE, INP-ENVT, INP-EI-Purpan, Université de Toulouse 3 Paul Sabatier, Toulouse, France.
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5
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Cell Cycle-Dependent Control and Roles of DNA Topoisomerase II. Genes (Basel) 2019; 10:genes10110859. [PMID: 31671531 PMCID: PMC6896119 DOI: 10.3390/genes10110859] [Citation(s) in RCA: 97] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Revised: 10/25/2019] [Accepted: 10/28/2019] [Indexed: 12/13/2022] Open
Abstract
Type II topoisomerases are ubiquitous enzymes in all branches of life that can alter DNA superhelicity and unlink double-stranded DNA segments during processes such as replication and transcription. In cells, type II topoisomerases are particularly useful for their ability to disentangle newly-replicated sister chromosomes. Growing lines of evidence indicate that eukaryotic topoisomerase II (topo II) activity is monitored and regulated throughout the cell cycle. Here, we discuss the various roles of topo II throughout the cell cycle, as well as mechanisms that have been found to govern and/or respond to topo II function and dysfunction. Knowledge of how topo II activity is controlled during cell cycle progression is important for understanding how its misregulation can contribute to genetic instability and how modulatory pathways may be exploited to advance chemotherapeutic development.
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6
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Guturi KKN, Bohgaki M, Bohgaki T, Srikumar T, Ng D, Kumareswaran R, El Ghamrasni S, Jeon J, Patel P, Eldin MS, Bristow R, Cheung P, Stewart GS, Raught B, Hakem A, Hakem R. RNF168 and USP10 regulate topoisomerase IIα function via opposing effects on its ubiquitylation. Nat Commun 2016; 7:12638. [PMID: 27558965 PMCID: PMC5007378 DOI: 10.1038/ncomms12638] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2015] [Accepted: 07/19/2016] [Indexed: 12/21/2022] Open
Abstract
Topoisomerase IIα (TOP2α) is essential for chromosomal condensation and segregation, as well as genomic integrity. Here we report that RNF168, an E3 ligase mutated in the human RIDDLE syndrome, interacts with TOP2α and mediates its ubiquitylation. RNF168 deficiency impairs decatenation activity of TOP2α and promotes mitotic abnormalities and defective chromosomal segregation. Our data also indicate that RNF168 deficiency, including in human breast cancer cell lines, confers resistance to the anti-cancer drug and TOP2 inhibitor etoposide. We also identify USP10 as a deubiquitylase that negatively regulates TOP2α ubiquitylation and restrains its chromatin association. These findings provide a mechanistic link between the RNF168/USP10 axis and TOP2α ubiquitylation and function, and suggest a role for RNF168 in the response to anti-cancer chemotherapeutics that target TOP2.
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Affiliation(s)
- Kiran Kumar Naidu Guturi
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Miyuki Bohgaki
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Toshiyuki Bohgaki
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Tharan Srikumar
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Deborah Ng
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Ramya Kumareswaran
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Samah El Ghamrasni
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Justin Jeon
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Parasvi Patel
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Mohamed Saad Eldin
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Rob Bristow
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Peter Cheung
- Department of Biology, York University, Toronto, Ontario, Canada M3J 1P3
| | - Grant S Stewart
- School of Cancer Sciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Brian Raught
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Anne Hakem
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
| | - Razqallah Hakem
- Department of Medical Biophysics, Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada M5G 1L7
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7
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Żabka A, Winnicki K, Polit JT, Maszewski J. The effects of anti-DNA topoisomerase II drugs, etoposide and ellipticine, are modified in root meristem cells of Allium cepa by MG132, an inhibitor of 26S proteasomes. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2015; 96:72-82. [PMID: 26233708 DOI: 10.1016/j.plaphy.2015.07.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/03/2015] [Revised: 06/17/2015] [Accepted: 07/17/2015] [Indexed: 06/04/2023]
Abstract
DNA topoisomerase II (Topo II), a highly specialized nuclear enzyme, resolves various entanglement problems concerning DNA that arise during chromatin remodeling, transcription, S-phase replication, meiotic recombination, chromosome condensation and segregation during mitosis. The genotoxic effects of two Topo II inhibitors known as potent anti-cancer drugs, etoposide (ETO) and ellipticine (EPC), were assayed in root apical meristem cells of Allium cepa. Despite various types of molecular interactions between these drugs and DNA-Topo II complexes at the chromatin level, which have a profound negative impact on the genome integrity (production of double-strand breaks, chromosomal bridges and constrictions, lagging fragments of chromosomes and their uneven segregation to daughter cell nuclei), most of the elicited changes were apparently similar, regarding both their intensity and time characteristics. No essential changes between ETO- and EPC-treated onion roots were noticed in the frequency of G1-, S-, G2-and M-phase cells, nuclear morphology, chromosome structures, tubulin-microtubule systems, extended distribution of mitosis-specific phosphorylation sites of histone H3, and the induction of apoptosis-like programmed cell death (AL-PCD). However, the important difference between the effects induced by the ETO and EPC concerns their catalytic activities in the presence of MG132 (proteasome inhibitor engaged in Topo II-mediated formation of cleavage complexes) and relates to the time-variable changes in chromosomal aberrations and AL-PCD rates. This result implies that proteasome-dependent mechanisms may contribute to the course of physiological effects generated by DNA lesions under conditions that affect the ability of plant cells to resolve topological problems that associated with the nuclear metabolic activities.
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Affiliation(s)
- Aneta Żabka
- Department of Cytophysiology, Faculty of Biology and Environmental Protection, University of Łódź, Pomorska 141/143, 90-236 Łódź, Poland.
| | - Konrad Winnicki
- Department of Cytophysiology, Faculty of Biology and Environmental Protection, University of Łódź, Pomorska 141/143, 90-236 Łódź, Poland.
| | - Justyna Teresa Polit
- Department of Cytophysiology, Faculty of Biology and Environmental Protection, University of Łódź, Pomorska 141/143, 90-236 Łódź, Poland.
| | - Janusz Maszewski
- Department of Cytophysiology, Faculty of Biology and Environmental Protection, University of Łódź, Pomorska 141/143, 90-236 Łódź, Poland.
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8
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Li H, Liu Y, Jiao Y, Guo A, Xu X, Qu X, Wang S, Zhao J, Li Y, Cao Y. Resveratrol sensitizes glioblastoma-initiating cells to temozolomide by inducing cell apoptosis and promoting differentiation. Oncol Rep 2015; 35:343-51. [PMID: 26498391 DOI: 10.3892/or.2015.4346] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 08/20/2015] [Indexed: 11/06/2022] Open
Abstract
Glioblastoma-initiating cells play crucial roles in the origin, growth, and recurrence of glioblastoma multiforme. The elimination of glioblastoma-initiating cells is believed to be a key strategy for achieving long-term survival of glioblastoma patients due to the highly resistant property of glioblastoma-initiating cells to temozolomide. Resveratrol, a naturally occurring polyphenol, has been widely studied as a promising candidate for cancer prevention and treatment. Whether resveratrol could enhance the sensitivity of glioblastoma-initiating cells to temozolomide therapy has not yet been reported. Here, using patient-derived glioblastoma-initiating cell lines, we found that resveratrol sensitized glioblastoma-initiating cells to temozolomide both in vitro and in vivo. Furthermore, we showed that resveratrol enhanced glioblastoma-initiating cells to temozolomide-induced apoptosis through DNA double-stranded breaks/pATM/pATR/p53 pathway activation, and promoted glioblastoma-initiating cell differentiation involving p-STAT3 inactivation. Our results propose that temozolomide and resveratrol combination strategy may be effective in the management of glioblastoma patients, particularly for those patients who have been present with a high abundance of glioblastoma-initiating cells in their tumors and show slight responsiveness to temozolomide.
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Affiliation(s)
- Hao Li
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
| | - Yaodong Liu
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
| | - Yumin Jiao
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
| | - Anchen Guo
- China National Clinical Research Center for Neurological Diseases, Beijing 100050, P.R. China
| | - Xiaoxue Xu
- Medical Experiments and Testing Center, Capital Medical University, Beijing 100069, P.R. China
| | - Xianjun Qu
- Department of Pharmacology, School of Chemical Biology and Pharmaceutical Sciences, Capital Medical University, Beijing 100069, P.R. China
| | - Shuo Wang
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
| | - Jizong Zhao
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
| | - Ye Li
- Department of Pharmacology, School of Chemical Biology and Pharmaceutical Sciences, Capital Medical University, Beijing 100069, P.R. China
| | - Yong Cao
- Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, P.R. China
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9
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Design and synthesis of 2-phenylnaphthalenoids and 2-phenylbenzofuranoids as DNA topoisomerase inhibitors and antitumor agents. Eur J Med Chem 2015; 102:277-87. [DOI: 10.1016/j.ejmech.2015.07.048] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Revised: 07/23/2015] [Accepted: 07/30/2015] [Indexed: 01/25/2023]
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10
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Miyata S, Fukuda Y, Tojima H, Matsuzaki K, Kitanaka S, Sawada H. Mechanism of the inhibition of leukemia cell growth and induction of apoptosis through the activation of ATR and PTEN by the topoisomerase inhibitor 3EZ, 20Ac-ingenol. Leuk Res 2015. [DOI: 10.1016/j.leukres.2015.06.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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11
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Gou Q, Xie Y, Liu L, Xie K, Wu Y, Wang Q, Wang Z, Li P. Downregulation of MDC1 and 53BP1 by short hairpin RNA enhances radiosensitivity in laryngeal carcinoma cells. Oncol Rep 2015; 34:251-7. [PMID: 25976740 DOI: 10.3892/or.2015.3980] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2014] [Accepted: 02/10/2015] [Indexed: 02/05/2023] Open
Abstract
DNA double-strand breaks (DSBs) induced by ionizing radiation (IR) are among the most cytotoxic types of DNA damage. The DNA damage response (DDR) may be a reason for the cancer cell resistance to radiotherapy using IR. Identified as critical upstream mediators of the phosphorylation of ataxia telangiectasia-mutated (ATM) pathway, mediator of DNA damage checkpoint 1 (MDC1) and p53-binding proteins 1 (53BP1) may affect the radiosensitivity of tumor cells. In the present study, we generated two HEP-2 cell lines with a stable knockdown of MDC1 or 53BP1 with short hairpin RNA (shRNA), respectively, and investigated the effect of MDC1 and 53BP1 on cell radiosensitivity, cell cycle distribution and the formation of cell foci. Downregulation of the two proteins reduced the number of clonogenic cells that treated with IR. Accumulation of G2/M phase cells was detected after the MDC1 and 53BP1 downregulation. These results indicated that the expression of MDC1 or 53BP1 limited tumor cell sensitivity to radiotherapy and may play an important role in the DNA repair progression. Furthermore, the MDC1 foci was identified and presented in the 53BP1-inhibited cells. By contrast, the 53BP1 foci was absent from the MDC1-inhibited cells. The results confirmed that the recruitment of 53BP1 into the foci occurred in an MDC1-dependent manner.
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Affiliation(s)
- Qiheng Gou
- State Key Laboratory of Biotherapy/Collaborative Innovation Center of Biotherapy, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Yuxin Xie
- Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Lei Liu
- Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Keqi Xie
- Department of Anesthesiology, Mianyang Central Hospital, Mianyang, Sichuan 621000, P.R. China
| | - Yanxia Wu
- Laboratory of Molecular Diagnosis of Cancer, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Qianqian Wang
- Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Zhu Wang
- Laboratory of Molecular Diagnosis of Cancer, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, P.R. China
| | - Ping Li
- Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu, Sichuan 610041, P.R. China
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12
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Brownlow N, Pike T, Zicha D, Collinson L, Parker PJ. Mitotic catenation is monitored and resolved by a PKCε-regulated pathway. Nat Commun 2014; 5:5685. [PMID: 25483024 PMCID: PMC4272242 DOI: 10.1038/ncomms6685] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 10/27/2014] [Indexed: 12/15/2022] Open
Abstract
Exit from mitosis is controlled by silencing of the spindle assembly checkpoint (SAC). It is important that preceding exit, all sister chromatid pairs are correctly bioriented, and that residual catenation is resolved, permitting complete sister chromatid separation in the ensuing anaphase. Here we determine that the metaphase response to catenation in mammalian cells operates through PKCε. The PKCε-controlled pathway regulates exit from the SAC only when mitotic cells are challenged by retained catenation and this delayed exit is characterized by BubR1-high and Mad2-low kinetochores. In addition, we show that this pathway is necessary to facilitate resolution of retained catenanes in mitosis. When delayed by catenation in mitosis, inhibition of PKCε results in premature entry into anaphase with PICH-positive strands and chromosome bridging. These findings demonstrate the importance of PKCε-mediated regulation in protection from loss of chromosome integrity in cells failing to resolve catenation in G2.
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Affiliation(s)
- Nicola Brownlow
- Protein Phosphorylation Laboratory, Cancer Research UK London
Research Institute, 44 Lincolns Inn Fields, London
WC2A 3LY, UK
| | - Tanya Pike
- Protein Phosphorylation Laboratory, Cancer Research UK London
Research Institute, 44 Lincolns Inn Fields, London
WC2A 3LY, UK
| | - Daniel Zicha
- Light Microscopy, Cancer Research UK London Research
Institute, London, WC2A 3LY, UK
| | - Lucy Collinson
- Electron Microscopy, Cancer Research UK London Research
Institute, London
WC2A 3LY, UK
| | - Peter J. Parker
- Protein Phosphorylation Laboratory, Cancer Research UK London
Research Institute, 44 Lincolns Inn Fields, London
WC2A 3LY, UK
- Division of Cancer Studies, King’s College London,
New Hunt’s House, Guy’s Campus, London
SE1 1UL, UK
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13
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Design and synthesis of 2-phenylnaphthalenoids as inhibitors of DNA topoisomeraseIIα and antitumor agents. Eur J Med Chem 2014; 86:782-96. [DOI: 10.1016/j.ejmech.2014.08.073] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Revised: 08/24/2014] [Accepted: 08/31/2014] [Indexed: 01/19/2023]
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14
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Wu Z, Zhao Y, Zhang Y, Zhu L. HY-2, a novel DNA topoisomerase II inhibitor, induces G2/M cell cycle arrest in HCT-116 cells. J Chemother 2013; 26:342-7. [PMID: 24188177 DOI: 10.1179/1973947813y.0000000153] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
4beta-(Benzoylthioureido)-4'-demethyl-4-desoxypodophyllotoxin (HY-2), a synthetic aroylthiourea analog of podophyllotoxin, was identified as a novel DNA topoisomerase II inhibitor. It exhibited significant antiproliferative effect on seven cancer cell lines and induced HCT-116 cells apoptosis. DNA flow cytometric analysis revealed that HY-2 induced cell cycle arrest at G2/M phase. Western blot analysis indicated that phosphorylation of cdc2 protein was decreased after HY-2 treatment, which might be the main cause for G2/M phase arrest.
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15
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Zabka A, Polit JT, Bernasińska J, Maszewski J. DNA topoisomerase II-dependent control of the cell cycle progression in root meristems of Allium cepa. Cell Biol Int 2013; 38:355-67. [PMID: 24302674 DOI: 10.1002/cbin.10211] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 10/27/2013] [Indexed: 12/14/2022]
Abstract
The catalytic ability of DNA topoisomerases (Topo) to generate short-term DNA breaks allow these enzymes to play crucial functions in managing DNA topology during S-phase replication, transcription, and chromatin-remodelling processes required to achieve commitment for the onset and transition through mitosis. Our experiments on root meristem cells of onion (Allium cepa) were designed to gain insight into the contribution of Topo II to plant-specific progression throughout interphase and mitosis. Irrespective of the position of the cell in interphase, the immunofluorescence of Topo II revealed similar nuclear labelling pattern with well defined signals dispersed in the nucleoplasm and the cortical zone of the nucleolus. Only weak labelling was detected in metaphase and anaphase chromosomes. Experiments with two potent anti-Topo II agents, doxorubicin (DOX, an anthracycline) and a bisdioxopiperazine derivative, ICRF-193, suggest that the inhibition-mediated increase in Topo II immunofluorescence may represent a compensatory mechanism, by which an up-regulated expression of the enzyme tends to counteract the drug-induced loss of indispensable catalytic and relaxation functions. γ-H2AX immunolabelling seems to indicate that both DOX- and ICRF-193-induced alterations in cell cycle progression reflect primarily the activity of the G2/M DNA damage checkpoint. Our findings provide evidence for the plant-specific cell cycle control mechanism induced by Topo II inhibitors under DNA stress conditions.
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Affiliation(s)
- Aneta Zabka
- Department of Cytophysiology, Faculty of Biology and Environmental Protection, University of Łódź, Pomorska 141/143, 90-236, Łódź, Poland
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16
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Abstract
Chromatin structure and dynamics control all aspects of DNA biology yet are poorly understood, especially at large length scales. We developed an approach, displacement correlation spectroscopy based on time-resolved image correlation analysis, to map chromatin dynamics simultaneously across the whole nucleus in cultured human cells. This method revealed that chromatin movement was coherent across large regions (4-5 µm) for several seconds. Regions of coherent motion extended beyond the boundaries of single-chromosome territories, suggesting elastic coupling of motion over length scales much larger than those of genes. These large-scale, coupled motions were ATP dependent and unidirectional for several seconds, perhaps accounting for ATP-dependent directed movement of single genes. Perturbation of major nuclear ATPases such as DNA polymerase, RNA polymerase II, and topoisomerase II eliminated micron-scale coherence, while causing rapid, local movement to increase; i.e., local motions accelerated but became uncoupled from their neighbors. We observe similar trends in chromatin dynamics upon inducing a direct DNA damage; thus we hypothesize that this may be due to DNA damage responses that physically relax chromatin and block long-distance communication of forces.
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17
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Zhao Y, Wu Z, Zhang Y, Zhu L. HY-1 induces G(2)/M cell cycle arrest in human colon cancer cells through the ATR-Chk1-Cdc25C and Weel pathways. Cancer Sci 2013; 104:1062-6. [PMID: 23600770 DOI: 10.1111/cas.12182] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 04/03/2013] [Accepted: 04/14/2013] [Indexed: 12/18/2022] Open
Abstract
The novel aroylthiourea analogue of podophyllotoxin HY-1 (4β-[benzoyl-thioureido]-4-deoxypodophyllotoxin) was synthesized in our laboratory with the aim of developing multitargeted DNA topoisomerase II inhibitors. The compound showed significant antiproliferative effects on seven cancer cell lines and induced G2 /M phase arrest in HCT116 cells. Moreover, HY-1 showed a potent inhibitory effect on topoisomerase II-mediated kinetoplast DNA decatenation in a dose-dependent manner. Our results showed that cdc2 phosphorylation and decreased cdc2 kinase acitivity through the ATR-Chk1-Cdc25C and Weel pathways were the central mechanisms for G2 /M phase arrest in human colon cancer cells.
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Affiliation(s)
- Yu Zhao
- Institute of Nautical Medicine, Nantong University, Nantong, China
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18
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3EZ,20Ac-ingenol, a catalytic inhibitor of topoisomerases, downregulates p-Akt and induces DSBs and apoptosis of DT40 cells. Arch Pharm Res 2013; 36:1029-38. [PMID: 23595550 PMCID: PMC3731510 DOI: 10.1007/s12272-013-0108-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2013] [Accepted: 03/21/2013] [Indexed: 11/24/2022]
Abstract
We have previously reported that many ingenol compounds derived from Euphorbia kansui exhibit topoisomerase (topo) II inhibitory activity. Of these compounds, 3EZ,20Ac-ingenol inhibited topo I activity. Camptothecin, which inhibits the religation activity of topo I without interfering with the binding of topo I to DNA and induces topo I-mediated DNA cleavage, was used as a positive control. In this study, we found that 3EZ,20Ac-ingenol did not hamper the binding of topo I to DNA in the same manner as camptothecin but affected the inhibition of cleavage of one DNA strand. 3EZ,20Ac-ingenol inhibited cell proliferation by blocking cell cycle progression in the G2/M phase. To define the mechanism of inhibition of DT40 cell proliferation, the change in Akt activity was observed because Akt activity is regulated in response to DNA damage. Western blot analysis revealed that 3EZ,20Ac-ingenol downregulated the expression of p-Akt, and apoptosis was detected by the presence of DNA double-strand breaks and caspase 3 activation.
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19
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Takeda S, Noguchi M, Matsuo K, Yamaguchi Y, Kudo T, Nishimura H, Okamoto Y, Amamoto T, Shindo M, Omiecinski CJ, Aramaki H. (-)-Xanthatin up-regulation of the GADD45γ tumor suppressor gene in MDA-MB-231 breast cancer cells: role of topoisomerase IIα inhibition and reactive oxygen species. Toxicology 2013; 305:1-9. [PMID: 23313378 PMCID: PMC4030303 DOI: 10.1016/j.tox.2012.12.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2012] [Revised: 12/26/2012] [Accepted: 12/31/2012] [Indexed: 11/23/2022]
Abstract
Previously, we reported that (-)-xanthatin, a naturally occurring xanthanolide present in the Cocklebur plant, exhibits potent anti-proliferative effects on human breast cancer cells, accompanied by an induction of the growth arrest and DNA damage-inducible gene 45γ (GADD45γ), recognized recently as a novel tumor suppressor gene. However, the mechanisms mediating this activation were unknown. Topoisomerase IIα (Topo IIα) inhibition has been reported to produce a cell death response accompanied by an atypical DNA laddering fragmentation profile, similar to that noted previously for (-)-xanthatin. Therefore we hypothesized that (-)-xanthatin's GADD45γ activation was mediated through the Topo IIα pathway. Here, we identify that (-)-xanthatin does function as a catalytic inhibitor of Topo IIα, promoting DNA damage. In addition, reactive oxygen species (ROS) were elevated in cells treated with this agent. Mechanistically, it was determined that the induced levels of GADD45γ mRNA resulting from (-)-xanthatin exposures were stabilized by coordinately produced ROS, and that the consequent induction of GADD45γ mRNA, GADD45γ protein and ROS generation were abrogated by co-treatment with N-acetyl-l-cysteine. Taken together, the data support the concept that Topo IIα inhibition by (-)-xanthatin is a trigger that stimulates expression of DNA damage-inducible GADD45γ mRNA and that concomitantly produced ROS act downstream to further enhance the GADD45γ mRNA/GADD45γ protein induction process, resulting in breast cancer cell death.
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Affiliation(s)
- Shuso Takeda
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Momoko Noguchi
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Kazumasa Matsuo
- Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan
| | - Yasuhiro Yamaguchi
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Taichi Kudo
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Hajime Nishimura
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Yoshiko Okamoto
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
| | - Toshiaki Amamoto
- NEUES Corporation, Yaesu Center Building 3F, 1-6-6 Yaesu, Chuo-ku, Tokyo 103-0028, Japan
| | - Mitsuru Shindo
- Institute for Materials Chemistry and Engineering, Kyushu University, 6-1 Kasuga-koen, Kasuga 816-8580, Japan
| | - Curtis J. Omiecinski
- Center for Molecular Toxicology and Carcinogenesis, 101 Life Sciences Building, Pennsylvania State University, University Park, PA 16802, United States
| | - Hironori Aramaki
- Department of Molecular Biology, Daiichi University of Pharmacy, 22-1 Tamagawa-cho, Minami-ku, Fukuoka 815-8511, Japan
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20
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Basso E, Fiore M, Leone S, Degrassi F, Cozzi R. Effects of resveratrol on topoisomerase II-α activity: induction of micronuclei and inhibition of chromosome segregation in CHO-K1 cells. Mutagenesis 2013; 28:243-8. [PMID: 23462849 DOI: 10.1093/mutage/ges067] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In recent years, a great interest has emerged in resveratrol (RSV) activity in the prevention of various pathologies including cancer. We recently showed that RSV is able to interfere with topoisomerase II-α (TOPO2) activity in cancer cells, thus inducing a delay in S-phase progression with concomitant phosphorylation of the histone H2AX. TOPO2 is mainly active in proliferating cells and is involved in the resolution of supercoiled DNA and chromosome segregation during mitosis. Here, we studied the effects of RSV in CHO-K1 cells concerning to chromosome damage and segregation as a consequence of TOPO2 inhibition. We show an increase in micronuclei and in polyploid and endoreduplicated cells due to incorrect chromosome segregation. Furthermore, since incomplete segregation can also affect the normal distribution of mitotic figures, we checked mitosis progression showing an increase in metaphase in relation to ana-telophase after RSV treatment. On the whole, our data show that RSV affects chromosome stability and segregation in proliferating cells, probably interfering with TOPO2 activity.
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Affiliation(s)
- Emiliano Basso
- Dipartimento di Biologia, Università Roma TRE, Roma, Italy
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21
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Solhaug A, Holme JA, Haglund K, Dendele B, Sergent O, Pestka J, Lagadic-Gossmann D, Eriksen GS. Alternariol induces abnormal nuclear morphology and cell cycle arrest in murine RAW 264.7 macrophages. Toxicol Lett 2013; 219:8-17. [PMID: 23454835 DOI: 10.1016/j.toxlet.2013.02.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 02/14/2013] [Accepted: 02/19/2013] [Indexed: 12/18/2022]
Abstract
The mycotoxin alternariol (AOH), a frequent contaminant in fruit and cereal products, is known to induce DNA damage with subsequent cell cycle arrest. Here we elucidated the effects of AOH on stages of cell cycle progression using the RAW 264.7 macrophage model. AOH resulted in an accumulation of cells in the G2/M-phase (4N). Most cells exhibited a large G2 nucleus whereas numbers of true mitotic cells were reduced relative to control. Both cyclin B1 and p-cdc2 levels increased, while cyclin B1 remained in the cytoplasm; suggesting arrest in the G2/M transition point. Remarkably, after exposure to AOH for 24h, most of the cells exhibited abnormally shaped nuclei, as evidenced by partly divided nuclei, nuclear blebs, polyploidy and micronuclei (MN). AOH treatment also induced abnormal Aurora B bridges, suggesting that cytokinesis was interfered within cells undergoing karyokinesis. A minor part of the resultant G1 tetraploid (4N) cells re-entered the S-phase and progressed to 8N cells.
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Affiliation(s)
- A Solhaug
- Norwegian Veterinary Institute, Oslo, Norway.
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22
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In vitro DNA-damaging effects of intestinal and related tetrapyrroles in human cancer cells. Exp Cell Res 2012; 319:536-45. [PMID: 23246570 PMCID: PMC3569715 DOI: 10.1016/j.yexcr.2012.12.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 12/03/2012] [Accepted: 12/04/2012] [Indexed: 11/23/2022]
Abstract
Epidemiological studies report a negative association between circulating bilirubin concentrations and the risk for cancer and cardiovascular disease. Structurally related tetrapyrroles also possess in vitro anti-genotoxic activity and may prevent mutation prior to malignancy. Furthermore, few data suggest that tetrapyrroles exert anti-carcinogenic effects via induction of cell cycle arrest and apoptosis. To further investigate whether tetrapyrroles provoke DNA-damage in human cancer cells, they were tested in the single cell gel electrophoresis assay (SCGE). Eight tetrapyrroles (unconjugated bilirubin, bilirubin ditaurate, biliverdin, biliverdin-/bilirubin dimethyl ester, urobilin, stercobilin and protoporphyrin) were added to cultured Caco2 and HepG2 cells and their effects on comet formation (% tail DNA) were assessed. Flow cytometric assessment (apoptosis/necrosis, cell cycle, intracellular radical species generation) assisted in revealing underlying mechanisms of intracellular action. Cells were incubated with tetrapyrroles at concentrations of 0.5, 5 and 17μM for 24h. Addition of 300μM tertiary-butyl hydroperoxide to cells served as a positive control. Tetrapyrrole incubation mostly resulted in increased DNA-damage (comet formation) in Caco2 and HepG2 cells. Tetrapyrroles that are concentrated within the intestine, including protoporphyrin, urobilin and stercobilin, led to significant comet formation in both cell lines, implicating the compounds in inducing DNA-damage and apoptosis in cancer cells found within organs of the digestive system.
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23
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Vijayakurup V, Carmela S, Carmelo D, Corrado T, Srinivas P, Gopala S. Phenethyl caffeate benzo[kl]xanthene lignan with DNA interacting properties induces DNA damage and apoptosis in colon cancer cells. Life Sci 2012; 91:1336-44. [DOI: 10.1016/j.lfs.2012.10.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 09/26/2012] [Accepted: 10/12/2012] [Indexed: 12/31/2022]
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24
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Leone S, Basso E, Polticelli F, Cozzi R. Resveratrol acts as a topoisomerase II poison in human glioma cells. Int J Cancer 2012; 131:E173-8. [PMID: 22095529 DOI: 10.1002/ijc.27358] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Accepted: 11/04/2011] [Indexed: 01/26/2023]
Abstract
Recently, we demonstrated that Resveratrol (RSV), a well known natural stilbene, is able to induce a delay in S progression with a concomitant increase in γH2AX expression in U87 glioma cells. Furthermore, we showed that it inhibits the ability of recombinant human topoisomerase IIα to decatenate kDNA in vitro. Because proliferating tumor cells express topoisomerases at high levels and these enzymes are important targets of some of the most successful anticancer drugs, we tested whether RSV is able to poison topoisomerase IIα in glioma cells. Then, we monitored the increase of micronuclei in RSV treated U87 cells as a consequence of the conversion of TOPOII/DNA cleavable complexes to permanent DNA damage. Finally, we assayed the ability of RSV in modulating the expression of target proteins involved in DNA damage signalling, namely ATR, ATM, Chk1, Chk2 and γH2AX. Through a molecular modelling here we show that RSV binds at the TOPOII/DNA interface thus establishing several hydrogen bonds. Moreover, we show that RSV poisons TOPOIIα so inducing DNA damage; ATM, Chk2 and γH2AX are involved in the DNA damage signalling after RSV treatment.
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Affiliation(s)
- Stefano Leone
- Department of Biology, University Roma TRE, Rome, Italy
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25
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26
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Ramamoorthy M, Tadokoro T, Rybanska I, Ghosh AK, Wersto R, May A, Kulikowicz T, Sykora P, Croteau DL, Bohr VA. RECQL5 cooperates with Topoisomerase II alpha in DNA decatenation and cell cycle progression. Nucleic Acids Res 2011; 40:1621-35. [PMID: 22013166 PMCID: PMC3287182 DOI: 10.1093/nar/gkr844] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
DNA decatenation mediated by Topoisomerase II is required to separate the interlinked sister chromatids post-replication. SGS1, a yeast homolog of the human RecQ family of helicases interacts with Topoisomerase II and plays a role in chromosome segregation, but this functional interaction has yet to be identified in higher organisms. Here, we report a physical and functional interaction of Topoisomerase IIα with RECQL5, one of five mammalian RecQ helicases, during DNA replication. Direct interaction of RECQL5 with Topoisomerase IIα stimulates the decatenation activity of Topoisomerase IIα. Consistent with these observations, RECQL5 co-localizes with Topoisomerase IIα during S-phase of the cell cycle. Moreover, cells with stable depletions of RECQL5 display a slow proliferation rate, a G2/M cell cycle arrest and late S-phase cycling defects. Metaphase spreads generated from RECQL5-depleted cells exhibit undercondensed and entangled chromosomes. Further, RECQL5-depleted cells activate a G2/M checkpoint and undergo apoptosis. These phenotypes are similar to those observed when Topoisomerase II catalytic activity is inhibited. These results reveal an important role for RECQL5 in the maintenance of genomic stability and a new insight into the decatenation process.
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Affiliation(s)
- Mahesh Ramamoorthy
- Laboratory of Molecular Gerontology, Biomedical Research Center, 251 Bayview Boulevard, National Institute on Aging, NIH, Baltimore, MD 21224, USA
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27
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Mitosis in vertebrates: the G2/M and M/A transitions and their associated checkpoints. Chromosome Res 2011; 19:291-306. [PMID: 21194009 DOI: 10.1007/s10577-010-9178-z] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
In this review, I stress the importance of direct data and accurate terminology when formulating and communicating conclusions on how the G2/M and metaphase/anaphase transitions are regulated. I argue that entry into mitosis (i.e., the G2/M transition) is guarded by several checkpoint control pathways that lose their ability to delay or stop further cell cycle progression once the cell becomes committed to divide, which in vertebrates occurs in the late stages of chromosome condensation. After this commitment, progress through mitosis is then mediated by a single Mad/Bub-based checkpoint that delays chromatid separation, and exit from mitosis (i.e., completion of the cell cycle) in the presence of unattached kinetochores. When cells cannot satisfy the mitotic checkpoint, e.g., when in concentrations of spindle poisons that prohibit the stable attachment of all kinetochores, they are delayed in mitosis for many hours. In normal cells, the duration of this delay depends on the organism and ranges from ∼4 h in rodents to ∼22 h in humans. Recent live cell studies reveal that under this condition, many cancer cells (including HeLa and U2OS) die in mitosis by apoptosis within ∼24 h, which implies that biochemical studies on cancer cell populations harvested in mitosis after a prolonged mitotic arrest are contaminated with dead or dying cells.
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28
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Watanabe M, Kamada Y, Miyazaki K, Mizoguchi S, Matsuzaki K, Kitanaka S, Miyata S. 20-O-IngenolEZ, a catalytic topoisomerase II inhibitor, specifically inhibits cell proliferation and induces double-strand DNA breaks in BLM-/- cells. MEDCHEMCOMM 2011. [DOI: 10.1039/c0md00252f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Lin W, Zhang J, Zhang J, Liu X, Fei Z, Li X, Davidovic L, Tang Z, Shen L, Deng Y, Yang A, Han H, Zhang X, Yao L. RNAi-mediated inhibition of MSP58 decreases tumour growth, migration and invasion in a human glioma cell line. J Cell Mol Med 2010; 13:4608-22. [PMID: 18798870 PMCID: PMC4515075 DOI: 10.1111/j.1582-4934.2008.00499.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
MSP58, a 58-kD nuclear microspherule protein, is an evolutionarily conserved nuclear protein implicated in the regulation of gene transcription as well as in malignant transformation. An analysis of mRNA expression by real-time PCR revealed that MSP58 was significantly up-regulated in 29% of high-grade glioblastoma tissues as well as in four glioblastoma cell lines. In the present study, we further evaluated the biological functions of MSP58 in U251 glioma cell proliferation, migration, invasion and tumour growth in vivo by specific MSP58 knockdown using short hairpin RNA (shRNA). We found that MSP58 depletion inhibited glioma cell growth, primarily by inducing cell cycle arrest rather than apoptosis. MSP58 depletion also decreased the invasive capability of glioma cells and anchorage-independent colony formation in soft agar. Moreover, suppression of MSP58 expression significantly impaired the growth of glioma xenografts in nude mice. Finally, a cell cycle-associated gene array revealed potential molecular mechanisms contributing to cell cycle arrest in MSP58-depleted glioma cells. In summary, our data highlight the importance of MSP58 in glioma progression and provided a biological basis for MSP58 as a novel candidate target for treatment of glioma.
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Affiliation(s)
- Wei Lin
- Department of Biochemistry and Molecular Biology, The Fourth Military Medical University and The State Key Laboratory of Cancer Biology, Xi'an, The People's Republic of China
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30
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Bower JJ, Karaca GF, Zhou Y, Simpson DA, Cordeiro-Stone M, Kaufmann WK. Topoisomerase IIalpha maintains genomic stability through decatenation G(2) checkpoint signaling. Oncogene 2010; 29:4787-99. [PMID: 20562910 PMCID: PMC2928865 DOI: 10.1038/onc.2010.232] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Topoisomerase IIalpha (topoIIalpha) is an essential mammalian enzyme that topologically modifies DNA and is required for chromosome segregation during mitosis. Previous research suggests that inhibition of topoII decatenatory activity triggers a G(2) checkpoint response, which delays mitotic entry because of insufficient decatenation of daughter chromatids. Here we examine the effects of both topoIIalpha and topoIIbeta on decatenatory activity in cell extracts, DNA damage and decatenation G(2) checkpoint function, and the frequencies of p16(INK4A) allele loss and gain. In diploid human fibroblast lines, depletion of topoIIalpha by small-interfering RNA was associated with severely reduced decatenatory activity, delayed progression from G(2) into mitosis and insensitivity to G(2) arrest induced by the topoII catalytic inhibitor ICRF-193. Furthermore, interphase nuclei of topoIIalpha-depleted cells showed increased frequencies of losses and gains of the tumor suppressor genetic locus p16(INK4A). This study shows that the topoIIalpha protein is required for decatenation G(2) checkpoint function, and inactivation of decatenation and the decatenation G(2) checkpoint leads to abnormal chromosome segregation and genomic instability.
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Affiliation(s)
- J J Bower
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
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31
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Bower JJ, Zhou Y, Zhou T, Simpson DA, Arlander SJ, Paules RS, Cordeiro-Stone M, Kaufmann WK. Revised genetic requirements for the decatenation G2 checkpoint: the role of ATM. Cell Cycle 2010; 9:1617-28. [PMID: 20372057 DOI: 10.4161/cc.9.8.11470] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The decatenation G2 checkpoint is proposed to delay cellular progression from G2 into mitosis when intertwined daughter chromatids are insufficiently decatenated. Previous studies indicated that the ATM- and Rad3-related (ATR) checkpoint kinase, but not the ataxia telangiectasia-mutated (ATM) kinase, was required for decatenation G2 checkpoint function. Here, we show that the method used to quantify decatenation G2 checkpoint function can influence the identification of genetic requirements for the checkpoint. Normal human diploid fibroblast (NHDF) lines responded to the topoisomerase II (topo II) catalytic inhibitor ICRF-193 with a stringent G2 arrest and a reduction in the mitotic index. While siRNA-mediated depletion of ATR and CHEK1 increased the mitotic index in ICRF-193 treated NHDF lines, depletion of these proteins did not affect the mitotic entry rate, indicating that the decatenation G2 checkpoint was functional. These results suggest that ATR and CHEK1 are not required for the decatenation G2 checkpoint, but may influence mitotic exit after inhibition of topo II. A re-evaluation of ataxia telangiectasia (AT) cell lines using the mitotic entry assay indicated that ATM was required for the decatenation G2 checkpoint. Three NHDF cell lines responded to ICRF-193 with a mean 98% inhibition of the mitotic entry rate. Examination of the mitotic entry rates in AT fibroblasts upon treatment with ICRF-193 revealed a significantly attenuated decatenation G2 checkpoint response, with a mean 59% inhibition of the mitotic entry rate. In addition, a normal lymphoblastoid line exhibited a 95% inhibition of the mitotic entry rate after incubation with ICRF-193, whereas two AT lymphoblastoid lines displayed only 36% and 20% inhibition of the mitotic entry rate. Stable depletion of ATM in normal human fibroblasts with short hairpin RNA also attenuated decatenation G2 checkpoint function by an average of 40%. Western immunoblot analysis demonstrated that treatment with ICRF-193 induced ATM autophosphorylation and ATM-dependent phosphorylation of Ser15-p53 and Thr68 in Chk2, but no appreciable phosphorylation of Ser139-H2AX or Ser345-Chk1. The results suggest that inhibition of topo II induces ATM to phosphorylate selected targets that contribute to a G2 arrest independently of DNA damage.
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Affiliation(s)
- Jacquelyn J Bower
- Department of Pathology and Laboratory Medicine, University of North Carolina-Chapel Hill, Chapel Hill, NC, USA
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32
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Skladanowski A, Bozko P, Sabisz M. DNA structure and integrity checkpoints during the cell cycle and their role in drug targeting and sensitivity of tumor cells to anticancer treatment. Chem Rev 2009; 109:2951-73. [PMID: 19522503 DOI: 10.1021/cr900026u] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Andrzej Skladanowski
- Department of Pharmaceutical Technology and Biochemistry, Faculty of Chemistry, Gdansk University of Technology, Gdansk, Poland.
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Lee MT, Bachant J. SUMO modification of DNA topoisomerase II: trying to get a CENse of it all. DNA Repair (Amst) 2009; 8:557-68. [PMID: 19230795 DOI: 10.1016/j.dnarep.2009.01.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
DNA topoisomerase II (topo II) is an essential determinant of chromosome structure and function, acting to resolve topological problems inherent in recombining, transcribing, replicating and segregating DNA. In particular, the unique decatenating activity of topo II is required for sister chromatids to disjoin and separate in mitosis. Topo II exhibits a dynamic localization pattern on mitotic chromosomes, accumulating at centromeres and axial chromosome cores prior to anaphase. In organisms ranging from yeast to humans, a fraction of topo II is targeted for SUMO conjugation in mitotic cells, and here we review our current understanding of the significance of this modification. As we shall see, an emerging consensus is that in metazoans SUMO modification is required for topo II to accumulate at centromeres, and that in the absence of this regulation there is an elevated frequency of chromosome non-disjunction, segregation errors, and aneuploidy. The underlying molecular mechanisms for how SUMO controls topo II are as yet unclear. In closing, however, we will evaluate two possible interpretations: one in which SUMO promotes enzyme turnover, and a second in which SUMO acts as a localization tag for topo II chromosome trafficking.
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Affiliation(s)
- Ming-Ta Lee
- Department of Cell Biology and Neuroscience, University of California, Riverside, Riverside, CA 92521, USA
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Terry SYA, Riches AC, Bryant PE. Suppression of topoisomerase IIalpha expression and function in human cells decreases chromosomal radiosensitivity. Mutat Res 2009; 663:40-5. [PMID: 19428368 DOI: 10.1016/j.mrfmmm.2009.01.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2008] [Revised: 01/14/2009] [Accepted: 01/22/2009] [Indexed: 11/24/2022]
Abstract
The mechanism behind chromatid break formation is as yet unclear, although it is known that DNA double-strand breaks (DSBs) are the initiating lesions. Chromatid breaks formed in cells in the G2-phase of the cell-cycle disappear ('rejoin') as a function of time between radiation exposure and cell fixation. However, the kinetics of disappearance of chromatid breaks does not correspond to those of DSB rejoining, leading us to seek alternative models. We have proposed that chromatid breaks could be formed indirectly from DSB and that the mechanism involves topoisomerase IIalpha. In support of this hypothesis we have recently shown that frequencies of radiation-induced chromatid breaks are lower in two variant human promyelocytic leukaemic cell lines with reduced topoisomerase IIalpha expression. Here we report that suppression of topoisomerase IIalpha in human hTERT-RPE1 cells, either by its abrogation using specific siRNA or by inhibition of its catalytic activity with the inhibitor ICRF-193, causes a reduction in frequency of chromatid breaks in radiation-exposed cells. The findings support our hypothesis for the involvement of topoisomerase IIalpha in the formation of radiation-induced chromatid breaks, and could help explain inter-individual variation in human chromosomal radiosensitivity; elevation of which has been linked with cancer susceptibility.
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Affiliation(s)
- Samantha Y A Terry
- Bute Medical School, University of St Andrews, St Andrews, Scotland, UK.
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Terry SYA, Riches AC, Bryant PE. Suppression of topoisomerase IIalpha expression and function in human cells decreases chromosomal radiosensitivity. Mutat Res 2009. [PMID: 19428368 DOI: 10.1016/j.mrfmmm] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/30/2022]
Abstract
The mechanism behind chromatid break formation is as yet unclear, although it is known that DNA double-strand breaks (DSBs) are the initiating lesions. Chromatid breaks formed in cells in the G2-phase of the cell-cycle disappear ('rejoin') as a function of time between radiation exposure and cell fixation. However, the kinetics of disappearance of chromatid breaks does not correspond to those of DSB rejoining, leading us to seek alternative models. We have proposed that chromatid breaks could be formed indirectly from DSB and that the mechanism involves topoisomerase IIalpha. In support of this hypothesis we have recently shown that frequencies of radiation-induced chromatid breaks are lower in two variant human promyelocytic leukaemic cell lines with reduced topoisomerase IIalpha expression. Here we report that suppression of topoisomerase IIalpha in human hTERT-RPE1 cells, either by its abrogation using specific siRNA or by inhibition of its catalytic activity with the inhibitor ICRF-193, causes a reduction in frequency of chromatid breaks in radiation-exposed cells. The findings support our hypothesis for the involvement of topoisomerase IIalpha in the formation of radiation-induced chromatid breaks, and could help explain inter-individual variation in human chromosomal radiosensitivity; elevation of which has been linked with cancer susceptibility.
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Affiliation(s)
- Samantha Y A Terry
- Bute Medical School, University of St Andrews, St Andrews, Scotland, UK.
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Park I, Park KK, Park JHY, Chung WY. Isoliquiritigenin induces G2 and M phase arrest by inducing DNA damage and by inhibiting the metaphase/anaphase transition. Cancer Lett 2009; 277:174-81. [PMID: 19167809 DOI: 10.1016/j.canlet.2008.12.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Revised: 12/01/2008] [Accepted: 12/03/2008] [Indexed: 10/21/2022]
Abstract
Isoliquiritigenin, a natural flavonoid found in licorice, shallots, and bean sprouts, has been demonstrated to inhibit proliferation and to induce apoptosis in a variety of human cancer cells. We attempted to ascertain the underlying mechanism by which isoliquiritigenin induced cell cycle arrest and cytotoxicity in HeLa human cervical cancer cells. Isoliquiritigenin treatment arrested cells in both G2 and M phase. The cells arrested in interphase (G2) showed markers for DNA damage including the formation of gamma-H2AX foci and the phosphorylation of ATM and Chk2, whereas the cells arrested in M phase evidenced separate poles and mitotic metaphase-like spindles with partially unaligned chromosomes. The induction of DNA damage and blockade at the metaphase/anaphase transition implied that isoliquiritigenin might function as a topoisomerase II poison, which was further demonstrated via an in vitro topoisomerase II inhibition assay. These results show that isoliquiritigenin inhibits topoiosmerase II activity, and the resultant DNA damage and arrest in mitotic metaphase-like stage contributes to the antiproliferative effects of isoliquiritigenin.
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Affiliation(s)
- Iha Park
- Oral Cancer Research Institute, Yonsei University College of Dentistry, Seoul, Republic of Korea
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Chène P, Rudloff J, Schoepfer J, Furet P, Meier P, Qian Z, Schlaeppi JM, Schmitz R, Radimerski T. Catalytic inhibition of topoisomerase II by a novel rationally designed ATP-competitive purine analogue. BMC CHEMICAL BIOLOGY 2009; 9:1. [PMID: 19128485 PMCID: PMC2628638 DOI: 10.1186/1472-6769-9-1] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/25/2008] [Accepted: 01/07/2009] [Indexed: 01/10/2023]
Abstract
Background Topoisomerase II poisons are in clinical use as anti-cancer therapy for decades and work by stabilizing the enzyme-induced DNA breaks. In contrast, catalytic inhibitors block the enzyme before DNA scission. Although several catalytic inhibitors of topoisomerase II have been described, preclinical concepts for exploiting their anti-proliferative activity based on molecular characteristics of the tumor cell have only recently started to emerge. Topoisomerase II is an ATPase and uses the energy derived from ATP hydrolysis to orchestrate the movement of the DNA double strands along the enzyme. Thus, interfering with ATPase function with low molecular weight inhibitors that target the nucleotide binding pocket should profoundly affect cells that are committed to undergo mitosis. Results Here we describe the discovery and characterization of a novel purine diamine analogue as a potent ATP-competitive catalytic inhibitor of topoisomerase II. Quinoline aminopurine compound 1 (QAP 1) inhibited topoisomerase II ATPase activity and decatenation reaction at sub-micromolar concentrations, targeted both topoisomerase II alpha and beta in cell free assays and, using a quantitative cell-based assay and a chromosome segregation assay, displayed catalytic enzyme inhibition in cells. In agreement with recent hypothesis, we show that BRCA1 mutant breast cancer cells have increased sensitivity to QAP 1. Conclusion The results obtained with QAP 1 demonstrate that potent and selective catalytic inhibition of human topoisomerase II function with an ATP-competitive inhibitor is feasible. Our data suggest that further drug discovery efforts on ATP-competitive catalytic inhibitors are warranted and that such drugs could potentially be developed as anti-cancer therapy for tumors that bear the appropriate combination of molecular alterations.
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Affiliation(s)
- Patrick Chène
- Department of Oncology, Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Joëlle Rudloff
- Department of Oncology, Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Joseph Schoepfer
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Pascal Furet
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Peter Meier
- Global Discovery Chemistry, Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Zhiyan Qian
- Department of Oncology, Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Jean-Marc Schlaeppi
- Biologics Center, Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Rita Schmitz
- Biologics Center, Novartis Institutes for BioMedical Research, Basel, Switzerland
| | - Thomas Radimerski
- Department of Oncology, Novartis Institutes for BioMedical Research, Basel, Switzerland
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Luo K, Yuan J, Chen J, Lou Z. Topoisomerase IIalpha controls the decatenation checkpoint. Nat Cell Biol 2008; 11:204-10. [PMID: 19098900 DOI: 10.1038/ncb1828] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Accepted: 10/27/2008] [Indexed: 01/27/2023]
Abstract
Topoisomerase II (Topo II) is required to separate intertwined sister chromatids before chromosome segregation can occur in mitosis. However, it remains to be resolved whether Topo II has any role in checkpoint control. Here we report that when phosphorylated, Ser 1524 of Topo IIalpha acts as a binding site for the BRCT domain of MDC1 (mediator of DNA damage checkpoint protein-1), thereby recruiting MDC1 to chromatin. Although Topo IIalpha-MDC1 interaction is not required for checkpoint activation induced by DNA damage, it is required for activation of the decatenation checkpoint. Mutation of Ser 1524 results in a defective decatenation checkpoint. These results reveal an important role of Topo II in checkpoint activation and in the maintenance of genomic stability.
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Affiliation(s)
- Kuntian Luo
- Division of Oncology Research, Department of Oncology, Mayo Clinic, Rochester, MN 55905, USA
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Jobson AG, Cardellina JH, Scudiero D, Kondapaka S, Zhang H, Kim H, Shoemaker R, Pommier Y. Identification of a Bis-guanylhydrazone [4,4'-Diacetyldiphenylurea-bis(guanylhydrazone); NSC 109555] as a novel chemotype for inhibition of Chk2 kinase. Mol Pharmacol 2007; 72:876-84. [PMID: 17616632 DOI: 10.1124/mol.107.035832] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Chk2 is a protein kinase involved in the ATM-dependent checkpoint pathway (http://discover.nci.nih.gov/mim). This pathway is activated by genomic instability and DNA damage and results in either cell cycle arrest, to allow DNA repair to occur, or cell death (apoptosis). Chk2 is activated by ATM-mediated phosphorylation and autophosphorylation and in turn phosphorylates its downstream targets (Cdc25A, Cdc25C, BRCA1, p53, Hdmx, E2F1, PP2A, and PML). Inhibition of Chk2 has been proposed to sensitize p53-deficient cells as well as protect normal tissue after exposure to DNA-damaging agents. We have developed a drug-screening program for specific Chk2 inhibitors using a fluorescence polarization assay, immobilized metal ion affinity-based fluorescence polarization (IMAP). This assay detects the degree of phosphorylation of a fluorescently linked substrate by Chk2. From a screen of over 100,000 compounds from the NCI Developmental Therapeutics Program, we identified a bis-guanylhydrazone [4,4'-diacetyldiphenylureabis(guanylhydrazone); NSC 109555] as a lead compound. In vitro data show the specific inhibition of Chk2 kinase activity by NSC 109555 using in vitro kinase assays and kinase-profiling experiments. NSC 109555 was shown to be a competitive inhibitor of Chk2 with respect to ATP, which was supported by docking of NSC 109555 into the ATP binding pocket of the Chk2 catalytic domain. The potency of NSC 109555 was comparable with that of other known Chk2 inhibitors, such as debromohymenialdisine and 2-arylbenzimidazole. These data define a novel chemotype for the development of potent and selective inhibitors of Chk2. This class of drugs may ultimately be useful in combination with current DNA-damaging agents used in the clinic.
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Affiliation(s)
- Andrew G Jobson
- Laboratory of Molecular Pharmacology, Bldg 37, Rm 5068, National Institutes of Health, Bethesda, MD 20892-4255.
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