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Khamidullina AI, Abramenko YE, Bruter AV, Tatarskiy VV. Key Proteins of Replication Stress Response and Cell Cycle Control as Cancer Therapy Targets. Int J Mol Sci 2024; 25:1263. [PMID: 38279263 PMCID: PMC10816012 DOI: 10.3390/ijms25021263] [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: 12/07/2023] [Revised: 01/14/2024] [Accepted: 01/17/2024] [Indexed: 01/28/2024] Open
Abstract
Replication stress (RS) is a characteristic state of cancer cells as they tend to exchange precision of replication for fast proliferation and increased genomic instability. To overcome the consequences of improper replication control, malignant cells frequently inactivate parts of their DNA damage response (DDR) pathways (the ATM-CHK2-p53 pathway), while relying on other pathways which help to maintain replication fork stability (ATR-CHK1). This creates a dependency on the remaining DDR pathways, vulnerability to further destabilization of replication and synthetic lethality of DDR inhibitors with common oncogenic alterations such as mutations of TP53, RB1, ATM, amplifications of MYC, CCNE1 and others. The response to RS is normally limited by coordination of cell cycle, transcription and replication. Inhibition of WEE1 and PKMYT1 kinases, which prevent unscheduled mitosis entry, leads to fragility of under-replicated sites. Recent evidence also shows that inhibition of Cyclin-dependent kinases (CDKs), such as CDK4/6, CDK2, CDK8/19 and CDK12/13 can contribute to RS through disruption of DNA repair and replication control. Here, we review the main causes of RS in cancers as well as main therapeutic targets-ATR, CHK1, PARP and their inhibitors.
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Affiliation(s)
- Alvina I. Khamidullina
- Laboratory of Molecular Oncobiology, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov Street, 119334 Moscow, Russia; (A.I.K.); (Y.E.A.)
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov Street, 119334 Moscow, Russia
| | - Yaroslav E. Abramenko
- Laboratory of Molecular Oncobiology, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov Street, 119334 Moscow, Russia; (A.I.K.); (Y.E.A.)
| | - Alexandra V. Bruter
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov Street, 119334 Moscow, Russia
| | - Victor V. Tatarskiy
- Laboratory of Molecular Oncobiology, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov Street, 119334 Moscow, Russia; (A.I.K.); (Y.E.A.)
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Institute of Gene Biology, Russian Academy of Sciences, 34/5 Vavilov Street, 119334 Moscow, Russia
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Seligmann JF, Fisher DJ, Brown LC, Adams RA, Graham J, Quirke P, Richman SD, Butler R, Domingo E, Blake A, Yates E, Braun M, Collinson F, Jones R, Brown E, de Winton E, Humphrey TC, Parmar M, Kaplan R, Wilson RH, Seymour M, Maughan TS. Inhibition of WEE1 Is Effective in TP53- and RAS-Mutant Metastatic Colorectal Cancer: A Randomized Trial (FOCUS4-C) Comparing Adavosertib (AZD1775) With Active Monitoring. J Clin Oncol 2021; 39:3705-3715. [PMID: 34538072 PMCID: PMC8601321 DOI: 10.1200/jco.21.01435] [Citation(s) in RCA: 48] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 07/27/2021] [Accepted: 08/16/2021] [Indexed: 12/18/2022] Open
Abstract
PURPOSE Outcomes in RAS-mutant metastatic colorectal cancer (mCRC) remain poor and patients have limited therapeutic options. Adavosertib is the first small-molecule inhibitor of WEE1 kinase. We hypothesized that aberrations in DNA replication seen in mCRC with both RAS and TP53 mutations would sensitize tumors to WEE1 inhibition. METHODS Patients with newly diagnosed mCRC were registered into FOCUS4 and tested for TP53 and RAS mutations. Those with both mutations who were stable or responding after 16 weeks of chemotherapy were randomly assigned 2:1 between adavosertib and active monitoring (AM). Adavosertib (250 mg or 300 mg) was taken orally once on days 1-5 and days 8-12 of a 3-week cycle. The primary outcome was progression-free survival (PFS), with a target hazard ratio (HR) of 0.5 and 80% power with a one-sided 0.025 significance level. RESULTS FOCUS4-C was conducted between April 2017 and Mar 2020 during which time 718 patients were registered; 247 (34%) were RAS/TP53-mutant. Sixty-nine patients were randomly assigned from 25 UK hospitals (adavosertib = 44; AM = 25). Adavosertib was associated with a PFS improvement over AM (median 3.61 v 1.87 months; HR = 0.35; 95% CI, 0.18 to 0.68; P = .0022). Overall survival (OS) was not improved with adavosertib versus AM (median 14.0 v 12.8 months; HR = 0.92; 95% CI, 0.44 to 1.94; P = .93). In prespecified subgroup analysis, adavosertib activity was greater in left-sided tumors (HR = 0.24; 95% CI, 0.11 to 0.51), versus right-sided (HR = 1.02; 95% CI, 0.41 to 2.56; interaction P = .043). Adavosertib was well-tolerated; grade 3 toxicities were diarrhea (9%), nausea (5%), and neutropenia (7%). CONCLUSION In this phase II randomized trial, adavosertib improved PFS compared with AM and demonstrates potential as a well-tolerated therapy for RAS/TP53-mutant mCRC. Further testing is required in this sizable population of unmet need.
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Affiliation(s)
- Jenny F. Seligmann
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom
| | | | | | - Richard A. Adams
- Centre for Trials Research University and Velindre NHS Trust, Cardiff, United Kingdom
| | | | - Philip Quirke
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom
| | - Susan D. Richman
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom
| | - Rachel Butler
- Bristol Genetics Laboratory, Bristol, United Kingdom
| | - Enric Domingo
- MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Andrew Blake
- MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Emma Yates
- MRC Clinical Trials Unit at UCL, London, United Kingdom
| | | | - Fiona Collinson
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom
| | - Rob Jones
- School of Medicine, Cardiff University, Cardiff, United Kingdom
| | - Ewan Brown
- Western General Hospital, Edinburgh, United Kingdom
| | | | - Timothy C. Humphrey
- MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
| | - Mahesh Parmar
- MRC Clinical Trials Unit at UCL, London, United Kingdom
| | | | | | - Matthew Seymour
- Leeds Institute of Medical Research, University of Leeds, Leeds, United Kingdom
| | - Timothy S. Maughan
- MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, United Kingdom
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Erber J, Steiner JD, Isensee J, Lobbes LA, Toschka A, Beleggia F, Schmitt A, Kaiser RWJ, Siedek F, Persigehl T, Hucho T, Reinhardt HC. Dual Inhibition of GLUT1 and the ATR/CHK1 Kinase Axis Displays Synergistic Cytotoxicity in KRAS-Mutant Cancer Cells. Cancer Res 2019; 79:4855-4868. [PMID: 31405847 DOI: 10.1158/0008-5472.can-18-3959] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 06/18/2019] [Accepted: 08/06/2019] [Indexed: 11/16/2022]
Abstract
The advent of molecularly targeted therapeutic agents has opened a new era in cancer therapy. However, many tumors rely on nondruggable cancer-driving lesions. In addition, long-lasting clinical benefits from single-agent therapies rarely occur, as most of the tumors acquire resistance over time. The identification of targeted combination regimens interfering with signaling through oncogenically rewired pathways provides a promising approach to enhance efficacy of single-agent-targeted treatments. Moreover, combination drug therapies might overcome the emergence of drug resistance. Here, we performed a focused flow cytometry-based drug synergy screen and identified a novel synergistic interaction between GLUT1-mediated glucose transport and the cell-cycle checkpoint kinases ATR and CHK1. Combined inhibition of CHK1/GLUT1 or ATR/GLUT1 robustly induced apoptosis, particularly in RAS-mutant cancer cells. Mechanistically, combined inhibition of ATR/CHK1 and GLUT1 arrested sensitive cells in S-phase and led to the accumulation of genotoxic damage, particularly in S-phase. In vivo, simultaneous inhibition of ATR and GLUT1 significantly reduced tumor volume gain in an autochthonous mouse model of KrasG12D -driven soft tissue sarcoma. Taken together, these findings pave the way for combined inhibition of GLUT1 and ATR/CHK1 as a therapeutic approach for KRAS-driven cancers. SIGNIFICANCE: Dual targeting of the DNA damage response and glucose transport synergistically induces apoptosis in KRAS-mutant cancer, suggesting this combination treatment for clinical validation in KRAS-stratified tumor patients.
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Affiliation(s)
- Johanna Erber
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Dusseldorf, Center for Molecular Medicine Cologne, CECAD, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany.
| | - Joachim D Steiner
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Dusseldorf, Center for Molecular Medicine Cologne, CECAD, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Jörg Isensee
- Translational Pain Research, Department of Anesthesiology and Intensive Care Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Leonard A Lobbes
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Dusseldorf, Center for Molecular Medicine Cologne, CECAD, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - André Toschka
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Dusseldorf, Center for Molecular Medicine Cologne, CECAD, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Filippo Beleggia
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Dusseldorf, Center for Molecular Medicine Cologne, CECAD, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Anna Schmitt
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Dusseldorf, Center for Molecular Medicine Cologne, CECAD, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Rainer W J Kaiser
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, CECAD, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Florian Siedek
- Institute of Diagnostic and Interventional Radiology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Thorsten Persigehl
- Institute of Diagnostic and Interventional Radiology, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Tim Hucho
- Translational Pain Research, Department of Anesthesiology and Intensive Care Medicine, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Hans C Reinhardt
- Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Dusseldorf, Center for Molecular Medicine Cologne, CECAD, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany.
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Gao Y, Kardos J, Yang Y, Tamir TY, Mutter-Rottmayer E, Weissman B, Major MB, Kim WY, Vaziri C. The Cancer/Testes (CT) Antigen HORMAD1 promotes Homologous Recombinational DNA Repair and Radioresistance in Lung adenocarcinoma cells. Sci Rep 2018; 8:15304. [PMID: 30333500 PMCID: PMC6192992 DOI: 10.1038/s41598-018-33601-w] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 10/01/2018] [Indexed: 12/24/2022] Open
Abstract
The Cancer/Testes (CT) Antigen HORMAD1 is germ cell-restricted and plays developmental roles in generation and processing of meiotic DNA Double Strand Breaks (DSB). Many tumors aberrantly overexpress HORMAD1 yet the potential impact of this CT antigen on cancer biology is unclear. We tested a potential role of HORMAD1 in genome maintenance in lung adenocarcinoma cells. We show that HORMAD1 re-distributes to nuclear foci and co-localizes with the DSB marker γH2AX in response to ionizing radiation (IR) and chemotherapeutic agents. The HORMA domain and C-term disordered oligomerization motif are necessary for localization of HORMAD1 to IR-induced foci (IRIF). HORMAD1-depleted cells are sensitive to IR and camptothecin. In reporter assays, Homologous Recombination (HR)-mediated repair of targeted ISce1-induced DSBs is attenuated in HORMAD1-depleted cells. In Non-Homologous End Joining (NHEJ) reporter assays, HORMAD1-depletion does not affect repair of ISce1-induced DSB. Early DSB signaling events (including ATM phosphorylation and formation of γH2AX, 53BP1 and NBS1 foci) are intact in HORMAD1-depleted cells. However, generation of RPA-ssDNA foci and redistribution of RAD51 to DSB are compromised in HORMAD1-depleted cells, suggesting that HORMAD1 promotes DSB resection. HORMAD1-mediated HR is a neomorphic activity that is independent of its meiotic partners (including HORMAD2 and CCDC36. Bioinformatic analysis of TCGA data show that similar to known HR pathway genes HORMAD1 is overexpressed in lung adenocarcinomas. Overexpression of HR genes is associated with specific mutational profiles (including copy number variation). Taken together, we identify HORMAD1-dependent DSB repair as a new mechanism of radioresistance and a probable determinant of mutability in lung adenocarcinoma.
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Affiliation(s)
- Yanzhe Gao
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, 614 Brinkhous-Bullitt Building, Chapel Hill, NC, 27599, USA
| | - Jordan Kardos
- Lineberger Comprehensive Cancer Center, Curriculum in Genetics and Molecular Biology, and Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Yang Yang
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, 614 Brinkhous-Bullitt Building, Chapel Hill, NC, 27599, USA
| | - Tigist Y Tamir
- Department of Cell Biology and Physiology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - Elizabeth Mutter-Rottmayer
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, 614 Brinkhous-Bullitt Building, Chapel Hill, NC, 27599, USA
| | - Bernard Weissman
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, 614 Brinkhous-Bullitt Building, Chapel Hill, NC, 27599, USA.,Lineberger Comprehensive Cancer Center, Curriculum in Genetics and Molecular Biology, and Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Michael B Major
- Department of Cell Biology and Physiology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, USA
| | - William Y Kim
- Lineberger Comprehensive Cancer Center, Curriculum in Genetics and Molecular Biology, and Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - Cyrus Vaziri
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, 614 Brinkhous-Bullitt Building, Chapel Hill, NC, 27599, USA. .,Lineberger Comprehensive Cancer Center, Curriculum in Genetics and Molecular Biology, and Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC, 27599, USA.
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5
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Yang Y, Gao Y, Zlatanou A, Tateishi S, Yurchenko V, Rogozin IB, Vaziri C. Diverse roles of RAD18 and Y-family DNA polymerases in tumorigenesis. Cell Cycle 2018; 17:833-843. [PMID: 29683380 PMCID: PMC6056224 DOI: 10.1080/15384101.2018.1456296] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Mutagenesis is a hallmark and enabling characteristic of cancer cells. The E3 ubiquitin ligase RAD18 and its downstream effectors, the ‘Y-family’ Trans-Lesion Synthesis (TLS) DNA polymerases, confer DNA damage tolerance at the expense of DNA replication fidelity. Thus, RAD18 and TLS polymerases are attractive candidate mediators of mutagenesis and carcinogenesis. The skin cancer-propensity disorder xeroderma pigmentosum-variant (XPV) is caused by defects in the Y-family DNA polymerase Pol eta (Polη). However it is unknown whether TLS dysfunction contributes more generally to other human cancers. Recent analyses of cancer genomes suggest that TLS polymerases generate many of the mutational signatures present in diverse cancers. Moreover biochemical studies suggest that the TLS pathway is often reprogrammed in cancer cells and that TLS facilitates tolerance of oncogene-induced DNA damage. Here we review recent evidence supporting widespread participation of RAD18 and the Y-family DNA polymerases in the different phases of multi-step carcinogenesis.
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Affiliation(s)
- Yang Yang
- a Department of Pathology and Laboratory Medicine , University of North Carolina at Chapel Hill Chapel Hill , NC , USA
| | - Yanzhe Gao
- a Department of Pathology and Laboratory Medicine , University of North Carolina at Chapel Hill Chapel Hill , NC , USA
| | - Anastasia Zlatanou
- a Department of Pathology and Laboratory Medicine , University of North Carolina at Chapel Hill Chapel Hill , NC , USA
| | - Satoshi Tateishi
- b Division of Cell Maintenance , Institute of Molecular Embryology and Genetics (IMEG) , Kumamoto University , Kumamoto , Japan
| | - Vyacheslav Yurchenko
- c Life Science Research Center , University of Ostrava , Ostrava , Czech Republic
| | - Igor B Rogozin
- d National Center for Biotechnology Information, National Library of Medicine , National Institutes of Health , Bethesda , MD , USA
| | - Cyrus Vaziri
- a Department of Pathology and Laboratory Medicine , University of North Carolina at Chapel Hill Chapel Hill , NC , USA
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Welcker D, Jain M, Khurshid S, Jokić M, Höhne M, Schmitt A, Frommolt P, Niessen CM, Spiro J, Persigehl T, Wittersheim M, Büttner R, Fanciulli M, Schermer B, Reinhardt HC, Benzing T, Höpker K. AATF suppresses apoptosis, promotes proliferation and is critical for Kras-driven lung cancer. Oncogene 2018; 37:1503-1518. [DOI: 10.1038/s41388-017-0054-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 11/02/2017] [Accepted: 11/03/2017] [Indexed: 12/20/2022]
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Yang Y, Gao Y, Mutter-Rottmayer L, Zlatanou A, Durando M, Ding W, Wyatt D, Ramsden D, Tanoue Y, Tateishi S, Vaziri C. DNA repair factor RAD18 and DNA polymerase Polκ confer tolerance of oncogenic DNA replication stress. J Cell Biol 2017; 216:3097-3115. [PMID: 28835467 PMCID: PMC5626543 DOI: 10.1083/jcb.201702006] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 06/27/2017] [Accepted: 07/21/2017] [Indexed: 12/30/2022] Open
Abstract
The elevated CDK2 activity of oncogene-expressing cells induces DNA replication stress. Yang et al. show that the DNA repair protein RAD18 facilitates damage-tolerant DNA synthesis via the DNA polymerase κ in cells with aberrantly high CDK2 activity, suggesting an important new role for RAD18 in sustaining neoplastic cell survival. The mechanisms by which neoplastic cells tolerate oncogene-induced DNA replication stress are poorly understood. Cyclin-dependent kinase 2 (CDK2) is a major mediator of oncogenic DNA replication stress. In this study, we show that CDK2-inducing stimuli (including Cyclin E overexpression, oncogenic RAS, and WEE1 inhibition) activate the DNA repair protein RAD18. CDK2-induced RAD18 activation required initiation of DNA synthesis and was repressed by p53. RAD18 and its effector, DNA polymerase κ (Polκ), sustained ongoing DNA synthesis in cells harboring elevated CDK2 activity. RAD18-deficient cells aberrantly accumulated single-stranded DNA (ssDNA) after CDK2 activation. In RAD18-depleted cells, the G2/M checkpoint was necessary to prevent mitotic entry with persistent ssDNA. Rad18−/− and Polκ−/− cells were highly sensitive to the WEE1 inhibitor MK-1775 (which simultaneously activates CDK2 and abrogates the G2/M checkpoint). Collectively, our results show that the RAD18–Polκ signaling axis allows tolerance of CDK2-mediated oncogenic stress and may allow neoplastic cells to breach tumorigenic barriers.
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Affiliation(s)
- Yang Yang
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Yanzhe Gao
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Liz Mutter-Rottmayer
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Anastasia Zlatanou
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Michael Durando
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Weimin Ding
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC.,Oncology Center, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - David Wyatt
- Lineberger Comprehensive Cancer Center, Curriculumin Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Dale Ramsden
- Lineberger Comprehensive Cancer Center, Curriculumin Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC.,Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Yuki Tanoue
- Division of Cell Maintenance, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Japan
| | - Satoshi Tateishi
- Division of Cell Maintenance, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto, Japan
| | - Cyrus Vaziri
- Department of Pathology and Laboratory Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC .,Lineberger Comprehensive Cancer Center, Curriculumin Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC
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Lyckesvärd MN, Kapoor N, Ingeson-Carlsson C, Carlsson T, Karlsson JO, Postgård P, Himmelman J, Forssell-Aronsson E, Hammarsten O, Nilsson M. Linking loss of sodium-iodide symporter expression to DNA damage. Exp Cell Res 2016; 344:120-131. [PMID: 27108928 DOI: 10.1016/j.yexcr.2016.04.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 04/18/2016] [Accepted: 04/20/2016] [Indexed: 12/11/2022]
Abstract
Radiotherapy of thyroid cancer with I-131 is abrogated by inherent loss of radioiodine uptake due to loss of sodium iodide symporter (NIS) expression in poorly differentiated tumor cells. It is also known that ionizing radiation per se down-regulates NIS (the stunning effect), but the mechanism is unknown. Here we investigated whether loss of NIS-mediated iodide transport may be elicited by DNA damage. Calicheamicin, a fungal toxin that specifically cleaves double-stranded DNA, induced a full scale DNA damage response mediated by the ataxia-telangiectasia mutated (ATM) kinase in quiescent normal thyrocytes. At sublethal concentrations (<1nM) calicheamicin blocked NIS mRNA expression and transepithelial iodide transport as stimulated by thyrotropin; loss of function occurred at a much faster rate than after I-131 irradiation. KU-55933, a selective ATM kinase inhibitor, partly rescued NIS expression and iodide transport in DNA-damaged cells. Prolonged ATM inhibition in healthy cells also repressed NIS-mediated iodide transport. ATM-dependent loss of iodide transport was counteracted by IGF-1. Together, these findings indicate that NIS, the major iodide transporter of the thyroid gland, is susceptible to DNA damage involving ATM-mediated mechanisms. This uncovers novel means of poor radioiodine uptake in thyroid cells subjected to extrinsic or intrinsic genotoxic stress.
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Affiliation(s)
- Madeleine Nordén Lyckesvärd
- Sahlgrenska Cancer Center, University of Gothenburg, Göteborg, Sweden; Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg, Sweden
| | - Nirmal Kapoor
- Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg, Sweden
| | - Camilla Ingeson-Carlsson
- Sahlgrenska Cancer Center, University of Gothenburg, Göteborg, Sweden; Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg, Sweden
| | - Therese Carlsson
- Sahlgrenska Cancer Center, University of Gothenburg, Göteborg, Sweden; Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg, Sweden
| | - Jan-Olof Karlsson
- Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg, Sweden
| | - Per Postgård
- Department of Radiation Physics, University of Gothenburg, Göteborg, Sweden
| | - Jakob Himmelman
- Department of Radiation Physics, University of Gothenburg, Göteborg, Sweden
| | | | - Ola Hammarsten
- Department of Clinical Chemistry, University of Gothenburg, Göteborg, Sweden
| | - Mikael Nilsson
- Sahlgrenska Cancer Center, University of Gothenburg, Göteborg, Sweden; Department of Medical Chemistry and Cell Biology, University of Gothenburg, Göteborg, Sweden.
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9
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Do K, Wilsker D, Ji J, Zlott J, Freshwater T, Kinders RJ, Collins J, Chen AP, Doroshow JH, Kummar S. Phase I Study of Single-Agent AZD1775 (MK-1775), a Wee1 Kinase Inhibitor, in Patients With Refractory Solid Tumors. J Clin Oncol 2015; 33:3409-15. [PMID: 25964244 PMCID: PMC4606059 DOI: 10.1200/jco.2014.60.4009] [Citation(s) in RCA: 242] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
PURPOSE Wee1 tyrosine kinase phosphorylates and inactivates cyclin-dependent kinase (Cdk) 1/2 in response to DNA damage. AZD1775 is a first-in-class inhibitor of Wee1 kinase with single-agent antitumor activity in preclinical models. We conducted a phase I study of single-agent AZD1775 in adult patients with refractory solid tumors to determine its maximum-tolerated dose (MTD), pharmacokinetics, and modulation of phosphorylated Tyr15-Cdk (pY15-Cdk) and phosphorylated histone H2AX (γH2AX) levels in paired tumor biopsies. PATIENTS AND METHODS AZD1775 was administered orally twice per day over 2.5 days per week for up to 2 weeks per 21-day cycle (3 + 3 design). At the MTD, paired tumor biopsies were obtained at baseline and after the fifth dose to determine pY15-Cdk and γH2AX levels. Six patients with BRCA-mutant solid tumors were also enrolled at the MTD. RESULTS Twenty-five patients were enrolled. The MTD was established as 225 mg twice per day orally over 2.5 days per week for 2 weeks per 21-day cycle. Confirmed partial responses were observed in two patients carrying BRCA mutations: one with head and neck cancer and one with ovarian cancer. Common toxicities were myelosuppression and diarrhea. Dose-limiting toxicities were supraventricular tachyarrhythmia and myelosuppression. Accumulation of drug (t1/2 approximately 11 hours) was observed. Reduction in pY15-Cdk levels (two of five paired biopsies) and increases in γH2AX levels (three of five paired biopsies) were demonstrated. CONCLUSION This is the first report of AZD1775 single-agent activity in patients carrying BRCA mutations. Proof-of-mechanism was demonstrated by target modulation and DNA damage response in paired tumor biopsies.
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Affiliation(s)
- Khanh Do
- Khanh Do, Jennifer Zlott, Jerry Collins, Alice P. Chen, James H. Doroshow, and Shivaani Kummar, National Cancer Institute, Bethesda, MD; Deborah Wilsker, Jiuping Ji, and Robert J. Kinders, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, MD; and Tomoko Freshwater, Merck Research Laboratories-Oncology, Boston, MA
| | - Deborah Wilsker
- Khanh Do, Jennifer Zlott, Jerry Collins, Alice P. Chen, James H. Doroshow, and Shivaani Kummar, National Cancer Institute, Bethesda, MD; Deborah Wilsker, Jiuping Ji, and Robert J. Kinders, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, MD; and Tomoko Freshwater, Merck Research Laboratories-Oncology, Boston, MA
| | - Jiuping Ji
- Khanh Do, Jennifer Zlott, Jerry Collins, Alice P. Chen, James H. Doroshow, and Shivaani Kummar, National Cancer Institute, Bethesda, MD; Deborah Wilsker, Jiuping Ji, and Robert J. Kinders, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, MD; and Tomoko Freshwater, Merck Research Laboratories-Oncology, Boston, MA
| | - Jennifer Zlott
- Khanh Do, Jennifer Zlott, Jerry Collins, Alice P. Chen, James H. Doroshow, and Shivaani Kummar, National Cancer Institute, Bethesda, MD; Deborah Wilsker, Jiuping Ji, and Robert J. Kinders, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, MD; and Tomoko Freshwater, Merck Research Laboratories-Oncology, Boston, MA
| | - Tomoko Freshwater
- Khanh Do, Jennifer Zlott, Jerry Collins, Alice P. Chen, James H. Doroshow, and Shivaani Kummar, National Cancer Institute, Bethesda, MD; Deborah Wilsker, Jiuping Ji, and Robert J. Kinders, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, MD; and Tomoko Freshwater, Merck Research Laboratories-Oncology, Boston, MA
| | - Robert J Kinders
- Khanh Do, Jennifer Zlott, Jerry Collins, Alice P. Chen, James H. Doroshow, and Shivaani Kummar, National Cancer Institute, Bethesda, MD; Deborah Wilsker, Jiuping Ji, and Robert J. Kinders, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, MD; and Tomoko Freshwater, Merck Research Laboratories-Oncology, Boston, MA
| | - Jerry Collins
- Khanh Do, Jennifer Zlott, Jerry Collins, Alice P. Chen, James H. Doroshow, and Shivaani Kummar, National Cancer Institute, Bethesda, MD; Deborah Wilsker, Jiuping Ji, and Robert J. Kinders, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, MD; and Tomoko Freshwater, Merck Research Laboratories-Oncology, Boston, MA
| | - Alice P Chen
- Khanh Do, Jennifer Zlott, Jerry Collins, Alice P. Chen, James H. Doroshow, and Shivaani Kummar, National Cancer Institute, Bethesda, MD; Deborah Wilsker, Jiuping Ji, and Robert J. Kinders, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, MD; and Tomoko Freshwater, Merck Research Laboratories-Oncology, Boston, MA
| | - James H Doroshow
- Khanh Do, Jennifer Zlott, Jerry Collins, Alice P. Chen, James H. Doroshow, and Shivaani Kummar, National Cancer Institute, Bethesda, MD; Deborah Wilsker, Jiuping Ji, and Robert J. Kinders, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, MD; and Tomoko Freshwater, Merck Research Laboratories-Oncology, Boston, MA
| | - Shivaani Kummar
- Khanh Do, Jennifer Zlott, Jerry Collins, Alice P. Chen, James H. Doroshow, and Shivaani Kummar, National Cancer Institute, Bethesda, MD; Deborah Wilsker, Jiuping Ji, and Robert J. Kinders, Leidos Biomedical Research, Frederick National Laboratory for Cancer Research, Frederick, MD; and Tomoko Freshwater, Merck Research Laboratories-Oncology, Boston, MA.
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10
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Brendel C, Teichler S, Millahn A, Stiewe T, Krause M, Stabla K, Ross P, Huynh M, Illmer T, Mernberger M, Barckhausen C, Neubauer A. Oncogenic NRAS Primes Primary Acute Myeloid Leukemia Cells for Differentiation. PLoS One 2015; 10:e0123181. [PMID: 25901794 PMCID: PMC4406710 DOI: 10.1371/journal.pone.0123181] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 02/17/2015] [Indexed: 11/18/2022] Open
Abstract
RAS mutations are frequently found among acute myeloid leukemia patients (AML), generating a constitutively active signaling protein changing cellular proliferation, differentiation and apoptosis. We have previously shown that treatment of AML patients with high-dose cytarabine is preferentially beneficial for those harboring oncogenic RAS. On the basis of a murine AML cell culture model, we ascribed this effect to a RAS-driven, p53-dependent induction of differentiation. Hence, in this study we sought to confirm the correlation between RAS status and differentiation of primary blasts obtained from AML patients. The gene expression signature of AML blasts with oncogenic NRAS indeed corresponded to a more mature profile compared to blasts with wildtype RAS, as demonstrated by gene set enrichment analysis (GSEA) and real-time PCR analysis of myeloid ecotropic viral integration site 1 homolog (MEIS1) in a unique cohort of AML patients. In addition, in vitro cell culture experiments with established cell lines and a second set of primary AML cells showed that oncogenic NRAS mutations predisposed cells to cytarabine (AraC) driven differentiation. Taken together, our findings show that AML with inv(16) and NRAS mutation have a differentiation gene signature, supporting the notion that NRAS mutation may predispose leukemic cells to AraC induced differentiation. We therefore suggest that promotion of differentiation pathways by specific genetic alterations could explain the superior treatment outcome after therapy in some AML patient subgroups. Whether a differentiation gene expression status may generally predict for a superior treatment outcome in AML needs to be addressed in future studies.
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Affiliation(s)
- Cornelia Brendel
- Department of Hematology, Oncology and Immunology, Philipps University of Marburg, and University Clinic Giessen and Marburg, Marburg, Germany
| | - Sabine Teichler
- Department of Hematology, Oncology and Immunology, Philipps University of Marburg, and University Clinic Giessen and Marburg, Marburg, Germany
| | - Axel Millahn
- Department of Hematology, Oncology and Immunology, Philipps University of Marburg, and University Clinic Giessen and Marburg, Marburg, Germany
| | - Thorsten Stiewe
- Molecular Oncology, Philipps University of Marburg, Marburg, Germany
| | - Michael Krause
- Molecular Oncology, Philipps University of Marburg, Marburg, Germany
| | - Kathleen Stabla
- Department of Hematology, Oncology and Immunology, Philipps University of Marburg, and University Clinic Giessen and Marburg, Marburg, Germany
| | - Petra Ross
- Department of Hematology, Oncology and Immunology, Philipps University of Marburg, and University Clinic Giessen and Marburg, Marburg, Germany
| | - Minh Huynh
- Department of Hematology, Oncology and Immunology, Philipps University of Marburg, and University Clinic Giessen and Marburg, Marburg, Germany
| | - Thomas Illmer
- Medical Clinic I, University Clinic of Technical University Dresden, Dresden, Germany
| | - Marco Mernberger
- Molecular Oncology, Philipps University of Marburg, Marburg, Germany
| | - Christina Barckhausen
- Department of Hematology, Oncology and Immunology, Philipps University of Marburg, and University Clinic Giessen and Marburg, Marburg, Germany
| | - Andreas Neubauer
- Department of Hematology, Oncology and Immunology, Philipps University of Marburg, and University Clinic Giessen and Marburg, Marburg, Germany
- * E-mail:
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11
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Talluri S, Francis SM, Dick FA. Mutation of the LXCXE binding cleft of pRb facilitates transformation by ras in vitro but does not promote tumorigenesis in vivo. PLoS One 2013; 8:e72236. [PMID: 23936539 PMCID: PMC3735560 DOI: 10.1371/journal.pone.0072236] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Accepted: 07/12/2013] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND The Retinoblastoma protein (pRB) is a key tumor suppressor that is functionally inactivated in most cancers. pRB regulates the cell division cycle and cell cycle exit through protein-protein interactions mediated by its multiple binding interfaces. The LXCXE binding cleft region of pRB mediates interactions with cellular proteins that have chromatin regulatory functions. Chromatin regulation mediated by pRB is required for a stress responsive cell cycle arrest, including oncogene induced senescence. The in vivo role of chromatin regulation by pRB during senescence, and its relevance to cancer is not clear. METHODOLOGY/PRINCIPAL FINDINGS Using gene-targeted mice, uniquely defective for pRB mediated chromatin regulation, we investigated its role during transformation and tumor progression in response to activation of oncogenic ras. We report that the pRB(∆L) mutation confers susceptibility to escape from HrasV12 induced senescence and allows transformation in vitro, although these cells possess high levels of DNA damage. Intriguingly, LSL-Kras, Rb1 (∆L/∆L) mice show delayed lung tumor formation compared to controls. This is likely due to the increased apoptosis seen in the early hyperplastic lesions shortly following ras activation that inhibits tumor progression. Furthermore, DMBA treatment to induce sporadic ras mutations in other tissues also failed to reveal greater susceptibility to cancer in Rb1 (∆L/∆L) mice. CONCLUSIONS/SIGNIFICANCE Our data suggests that chromatin regulation by pRB can function to limit proliferation, but its loss fails to contribute to cancer susceptibility in ras driven tumor models because of elevated levels of DNA damage and apoptosis.
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Affiliation(s)
- Srikanth Talluri
- London Regional Cancer Program, Western University, London, Ontario, Canada
- Department of Biochemistry, Western University, London, Ontario, Canada
| | - Sarah M. Francis
- London Regional Cancer Program, Western University, London, Ontario, Canada
- Department of Biochemistry, Western University, London, Ontario, Canada
| | - Frederick A. Dick
- London Regional Cancer Program, Western University, London, Ontario, Canada
- Children’s Health Research Institute, Western University, London, Ontario, Canada
- Department of Biochemistry, Western University, London, Ontario, Canada
- * E-mail:
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12
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Origanti S, Cai SR, Munir AZ, White LS, Piwnica-Worms H. Synthetic lethality of Chk1 inhibition combined with p53 and/or p21 loss during a DNA damage response in normal and tumor cells. Oncogene 2013; 32:577-88. [PMID: 22430210 PMCID: PMC3381958 DOI: 10.1038/onc.2012.84] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Cell cycle checkpoints ensure genome integrity and are frequently compromised in human cancers. A therapeutic strategy being explored takes advantage of checkpoint defects in p53-deficient tumors in order to sensitize them to DNA-damaging agents by eliminating Chk1-mediated checkpoint responses. Using mouse models, we demonstrated that p21 is a key determinant of how cells respond to the combination of DNA damage and Chk1 inhibition (combination therapy) in normal cells as well as in tumors. Loss of p21 sensitized normal cells to the combination therapy much more than did p53 loss and the enhanced lethality was partially blocked by CDK inhibition. In addition, basal pools of p21 (p53 independent) provided p53 null cells with protection from the combination therapy. Our results uncover a novel p53-independent function for p21 in protecting cells from the lethal effects of DNA damage followed by Chk1 inhibition. As p21 levels are low in a significant fraction of colorectal tumors, they are predicted to be particularly sensitive to the combination therapy. Results reported in this study support this prediction.
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Affiliation(s)
- Sofia Origanti
- Department of Cell Biology and Physiology, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
- BRIGHT Institute, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
| | - Shi-rong Cai
- Department of Cell Biology and Physiology, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
- BRIGHT Institute, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
| | - Amir Z. Munir
- Department of Cell Biology and Physiology, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
- BRIGHT Institute, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
| | - Lynn S. White
- Department of Cell Biology and Physiology, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
- BRIGHT Institute, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
| | - Helen Piwnica-Worms
- Department of Cell Biology and Physiology, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
- BRIGHT Institute, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
- Department of Internal Medicine, Washington University School of Medicine, Campus Box 8228, 660 S. Euclid Ave. St. Louis, MO 63110-1093, USA
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13
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Ferreira JP, Lawhorn IEB, Peacock RWS, Wang CL. Quantitative assessment of Ras over-expression via shotgun deployment of vectors utilizing synthetic promoters. Integr Biol (Camb) 2011; 4:108-14. [PMID: 22108821 DOI: 10.1039/c1ib00082a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We sought to characterize and compare wild-type and oncogenic Ras over-expression. Because different levels of Ras over-expression can have different effects on cell phenotype, it was important to evaluate a wide range of expression. Different expression levels were achieved by using retroviral vectors equipped with different strength promoters. Cells were "shotgun" transduced with a mixture of these vectors to generate heterogeneous populations exhibiting a range of expression levels. We used flow cytometry to analyze the populations and generate high-resolution, nearly continuous Ras dose-response curves. These efforts revealed that a single-copy level of oncogenic Ras generated maximal imatinib resistance and activated MAPK pathway signaling as effectively as six-fold amplification of wild-type Ras. Although further increased expression lead to even greater signal transduction, this increased expression had minimal or decreasing effects on the proliferation rate. In addition, this study introduces a general method to quantify genetic dose-response relationships and identify gene expression ranges that produce an optimized phenotypic response.
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Affiliation(s)
- Joshua P Ferreira
- Department of Chemical Engineering, Stanford University, 381 N-S Axis, Rm 113, Stanford, CA 94305, USA
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14
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Cytokinetically quiescent (G0/G1) human multiple myeloma cells are susceptible to simultaneous inhibition of Chk1 and MEK1/2. Blood 2011; 118:5189-200. [PMID: 21911831 DOI: 10.1182/blood-2011-02-339432] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Effects of Chk1 and MEK1/2 inhibition were investigated in cytokinetically quiescent multiple myeloma (MM) and primary CD138(+) cells. Coexposure to the Chk1 and MEK1/2 inhibitors AZD7762 and selumetinib (AZD6244) robustly induced apoptosis in various MM cells and CD138(+) primary samples, but spared normal CD138(-) and CD34(+) cells. Furthermore, Chk1/MEK1/2 inhibitor treatment of asynchronized cells induced G(0)/G(1) arrest and increased apoptosis in all cell-cycle phases, including G(0)/G(1). To determine whether this regimen is active against quiescent G(0)/G(1) MM cells, cells were cultured in low-serum medium to enrich the G(0)/G(1) population. G(0)/G(1)-enriched cells exhibited diminished sensitivity to conventional agents (eg, Taxol and VP-16) but significantly increased susceptibility to Chk1 ± MEK1/2 inhibitors or Chk1 shRNA knock-down. These events were associated with increased γH2A.X expression/foci formation and Bim up-regulation, whereas Bim shRNA knock-down markedly attenuated lethality. Immunofluorescent analysis of G(0)/G(1)-enriched or primary MM cells demonstrated colocalization of activated caspase-3 and the quiescent (G(0)) marker statin, a nuclear envelope protein. Finally, Chk1/MEK1/2 inhibition increased cell death in the Hoechst-positive (Hst(+)), low pyronin Y (PY)-staining (2N Hst(+)/PY(-)) G(0) population and in sorted small side-population (SSP) MM cells. These findings provide evidence that cytokinetically quiescent MM cells are highly susceptible to simultaneous Chk1 and MEK1/2 inhibition.
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15
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Ahmad EI, Gawish HH, Al Azizi NM, Elhefni AM. The prognostic impact of K-RAS mutations in adult acute myeloid leukemia patients treated with high-dose cytarabine. Onco Targets Ther 2011; 4:115-21. [PMID: 21792317 PMCID: PMC3143910 DOI: 10.2147/ott.s12602] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background Activating point mutation of the RAS gene has been generally accepted as an oncogenic event in a variety of malignancies. It represents one of the most common genetic alterations in acute myeloid leukemia (AML). However, little is known about its clinical relevance in the treatment outcome for this leukemia. Objective This study aimed to clarify the biologic and prognostic impact of K-RAS mutations in relation to the dose of cytarabine (ara-C) used in postinduction consolidation chemotherapy in adult AML patients. Patients and methods The study comprised of 71 de novo AML patients with male/ female ratio 1.4:1; their ages ranged from 21–59 years with a median of 37 years. They were subjected to full clinical evaluation, routine laboratory investigations, cytogenetic studies by G-banding (Giemsa staining), and K-RAS mutation detection using real-time polymerase chain reaction. The patients were randomized into two groups according to the ara-C dose used in consolidation treatment, the high the dose ara-C (HDAC) group receiving 400 mg ara-C and-low-dose ara-C (LDAC) group receiving 100 mg ara-C; they were followed over a period of five years. Results Mutations in the K-RAS gene (mutRAS) were detected in 23 patients (32%) with the remaining 48 patients (68%) having wild-type RAS (wtRAS). The percent of blast cells was significantly lower in mutRAS compared to wtRAS patients (P ≤ 0.001) while M4 subtype of AML and Inv(16) frequencies were significantly higher in mutRAS compared to wtRAS patients (P = 0.015) and (P = 0.003), respectively. The patients were followed up for a median of 43 months (range 11–57 months). There was no significant difference in overall survival (OS) between mutRAS and wtRAS (P = 0.326). Within the mutRAS patients treated with HDAC, cumulative OS was significantly higher than those treated with LDAC (P = 0.001). This was not the case in the wtRAS group (P = 0.285). There was no significant difference in disease-free survival (DFS) between mutRAS and wtRAS groups (P = 0.923). mutRAS patients treated with HDAC had a statistically higher cumulative DFS than mutRAS patients treated with LDAC (P = 0.001). Patients with wtRAS also benefited from HDAC, but to a lesser extent. Among patients with wtRAS, those treated with HDAC showed higher cumulative and median DFS than patients treated with LDAC (P = 0.031). Conclusion It was concluded that adult AML patients carrying mutations in the K-RAS gene benefit from higher ara-C doses more than wtRAS patients, so pretreatment mutation detection could be an important predictor for treatment strategy and survival of adult AML patients. These findings counter the prevailing bias that oncogene mutations lead to more aggressive behavior in human malignancies.
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Affiliation(s)
- Ebtesam I Ahmad
- Clinical Pathology Department, Hematology and Oncology Unit of Internal Medicine Department, Faculty of Medicine, Zagazig University, Sharkia, Egypt
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16
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Overmeyer JH, Maltese WA. Death pathways triggered by activated Ras in cancer cells. Front Biosci (Landmark Ed) 2011; 16:1693-713. [PMID: 21196257 DOI: 10.2741/3814] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Ras GTPases are best known for their ability to serve as molecular switches regulating cell growth, differentiation and survival. Gene mutations that result in expression of constitutively active forms of Ras have been linked to oncogenesis in animal models and humans. However, over the past two decades, evidence has gradually accumulated to support a paradoxical role for Ras proteins in the initiation of cell death pathways. In this review we survey the literature pointing to the ability of activated Ras to promote cell death under conditions where cancer cells encounter apoptotic stimuli or Ras is ectopically expressed. In some of these cases Ras acts through known effectors and well defined apoptotic death pathways. However, in other cases it appears that Ras operates by triggering novel non-apoptotic death mechanisms that are just beginning to be characterized. Understanding these mechanisms and the factors that go into changing the nature of Ras signaling from pro-survival to pro-death could set the stage for development of novel therapeutic approaches aimed at manipulating pro-death Ras signaling pathways in cancer.
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Affiliation(s)
- Jean H Overmeyer
- Department of Biochemistry and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio 43614, USA
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17
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Gilad O, Nabet BY, Ragland RL, Schoppy DW, Smith KD, Durham AC, Brown EJ. Combining ATR suppression with oncogenic Ras synergistically increases genomic instability, causing synthetic lethality or tumorigenesis in a dosage-dependent manner. Cancer Res 2010; 70:9693-702. [PMID: 21098704 DOI: 10.1158/0008-5472.can-10-2286] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Previous studies indicate that oncogenic stress activates the ATR-Chk1 pathway. Here, we show that ATR-Chk1 pathway engagement is essential for limiting genomic instability following oncogenic Ras transformation. ATR pathway inhibition in combination with oncogenic Ras expression synergistically increased genomic instability, as quantified by chromatid breaks, sister chromatid exchanges, and H2AX phosphorylation. This level of instability was significantly greater than that observed following ATR suppression in untransformed control cells. In addition, consistent with a deficiency in long-term genome maintenance, hypomorphic ATR pathway reduction to 16% of normal levels was synthetic lethal with oncogenic Ras expression in cultured cells. Notably, elevated genomic instability and synthetic lethality following suppression of ATR were not due to accelerated cycling rates in Ras-transformed cells, indicating that these synergistic effects were generated on a per-cell-cycle basis. In contrast to the synthetic lethal effects of hypomorphic ATR suppression, subtle reduction of ATR expression (haploinsufficiency) in combination with endogenous levels of K-ras(G12D) expression elevated the incidence of lung adenocarcinoma, spindle cell sarcoma, and thymic lymphoma in p53 heterozygous mice. K-ras(G12D)-induced tumorigenesis in ATR(+/-)p53(+/-) mice was associated with intrachromosomal deletions and loss of wild-type p53. These findings indicate that synergistic increases in genomic instability following ATR reduction in oncogenic Ras-transformed cells can produce 2 distinct biological outcomes: synthetic lethality upon significant suppression of ATR expression and tumor promotion in the context of ATR haploinsufficiency. These results highlight the importance of the ATR pathway both as a barrier to malignant progression and as a potential target for cancer treatment.
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MESH Headings
- Animals
- Antineoplastic Agents, Hormonal/pharmacology
- Ataxia Telangiectasia Mutated Proteins
- Blotting, Western
- Cell Cycle Proteins/genetics
- Cell Cycle Proteins/metabolism
- Cell Transformation, Neoplastic/genetics
- Cells, Cultured
- Checkpoint Kinase 1
- Dose-Response Relationship, Drug
- Female
- Gene Expression Regulation, Neoplastic
- Genes, ras/genetics
- Genomic Instability
- Male
- Mice
- Mice, 129 Strain
- Mice, Inbred C57BL
- Mice, Knockout
- NIH 3T3 Cells
- Neoplasms, Experimental/genetics
- Neoplasms, Experimental/metabolism
- Neoplasms, Experimental/pathology
- Protein Kinases/genetics
- Protein Kinases/metabolism
- Protein Serine-Threonine Kinases/genetics
- Protein Serine-Threonine Kinases/metabolism
- RNA Interference
- Recombination, Genetic/drug effects
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction
- Tamoxifen/pharmacology
- Tumor Suppressor Protein p53/genetics
- Tumor Suppressor Protein p53/metabolism
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Affiliation(s)
- Oren Gilad
- Abramson Family Cancer Research Institute and Department of Cancer Biology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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18
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Meyer M, Rübsamen D, Slany R, Illmer T, Stabla K, Roth P, Stiewe T, Eilers M, Neubauer A. Oncogenic RAS enables DNA damage- and p53-dependent differentiation of acute myeloid leukemia cells in response to chemotherapy. PLoS One 2009; 4:e7768. [PMID: 19890398 PMCID: PMC2767509 DOI: 10.1371/journal.pone.0007768] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2009] [Accepted: 10/05/2009] [Indexed: 01/23/2023] Open
Abstract
Acute myeloid leukemia (AML) is a clonal disease originating from myeloid progenitor cells with a heterogeneous genetic background. High-dose cytarabine is used as the standard consolidation chemotherapy. Oncogenic RAS mutations are frequently observed in AML, and are associated with beneficial response to cytarabine. Why AML-patients with oncogenic RAS benefit most from high-dose cytarabine post-remission therapy is not well understood. Here we used bone marrow cells expressing a conditional MLL-ENL-ER oncogene to investigate the interaction of oncogenic RAS and chemotherapeutic agents. We show that oncogenic RAS synergizes with cytotoxic agents such as cytarabine in activation of DNA damage checkpoints, resulting in a p53-dependent genetic program that reduces clonogenicity and increases myeloid differentiation. Our data can explain the beneficial effects observed for AML patients with oncogenic RAS treated with higher dosages of cytarabine and suggest that induction of p53-dependent differentiation, e.g. by interfering with Mdm2-mediated degradation, may be a rational approach to increase cure rate in response to chemotherapy. The data also support the notion that the therapeutic success of cytotoxic drugs may depend on their ability to promote the differentiation of tumor-initiating cells.
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Affiliation(s)
- Mona Meyer
- Klinik für Hämatologie, Onkologie und Immunologie, Philipps Universität Marburg, Marburg, Germany
- Institut für Molekularbiologie und Tumorforschung, Philipps Universität Marburg, Marburg, Germany
| | - Daniela Rübsamen
- Institut für Molekularbiologie und Tumorforschung, Philipps Universität Marburg, Marburg, Germany
| | - Robert Slany
- Institut für Genetik, Friedrich Alexander Universität Erlangen, Erlangen, Germany
| | - Thomas Illmer
- Technische Universität Dresden, Medizinische Klinik I, Dresden, Germany
| | - Kathleen Stabla
- Klinik für Hämatologie, Onkologie und Immunologie, Philipps Universität Marburg, Marburg, Germany
| | - Petra Roth
- Klinik für Hämatologie, Onkologie und Immunologie, Philipps Universität Marburg, Marburg, Germany
| | - Thorsten Stiewe
- Klinik für Hämatologie, Onkologie und Immunologie, Philipps Universität Marburg, Marburg, Germany
| | - Martin Eilers
- Biocenter, Julius-Maximilians-Universität Würzburg, Würzburg, Germany
| | - Andreas Neubauer
- Klinik für Hämatologie, Onkologie und Immunologie, Philipps Universität Marburg, Marburg, Germany
- * E-mail:
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19
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Burhans WC, Heintz NH. The cell cycle is a redox cycle: linking phase-specific targets to cell fate. Free Radic Biol Med 2009; 47:1282-93. [PMID: 19486941 DOI: 10.1016/j.freeradbiomed.2009.05.026] [Citation(s) in RCA: 254] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 05/19/2009] [Accepted: 05/22/2009] [Indexed: 11/22/2022]
Abstract
Reactive oxygen species (ROS) regulate the strength and duration of signaling through redox-dependent signal transduction pathways via the cyclic oxidation/reduction of cysteine residues in kinases, phosphatases, and other regulatory factors. Signaling circuits may be segregated in organelles or other subcellular domains with distinct redox states, permitting them to respond independently to changes in the oxidation state of two major thiol reductants, glutathione and thioredoxin. Studies in yeast, and in complex eukaryotes, show that oscillations in oxygen consumption, energy metabolism, and redox state are intimately integrated with cell cycle progression. Because signaling pathways play specific roles in different phases of the cell cycle and the hierarchy of redox-dependent regulatory checkpoints changes during cell cycle progression, the effects of ROS on cell fate vary during the cell cycle. In G1, ROS stimulate mitogenic pathways that control the activity of cyclin-dependent kinases (CDKs) and phosphorylation of the retinoblastoma protein (pRB), thereby regulating S-phase entry. In response to oxidative stress, Nrf2 and Foxo3a promote cell survival by inducing the expression of antioxidant enzymes and factors involved in cell cycle withdrawal, such as the cyclin-dependent kinase inhibitor (CKI) p27. In S phase, ROS induce S-phase arrest via PP2A-dependent dephosphorylation of pRB. In precancerous cells, unconstrained mitogenic signaling by activated oncogenes induces replication stress in S phase, which activates the DNA-damage response and induces cell senescence. A number of studies suggest that interactions of ROS with the G1 CDK/CKI network play a fundamental role in senescence, which is considered a barrier to tumorigenesis. Adaptive responses and loss of checkpoint proteins such as p53 and p16(INK4a) allow tumor cells to tolerate constitutive mitogenic signaling and enhanced production of ROS, leading to altered redox status in many fully transformed cells. Alterations in oxidant and energy metabolism of cancer cells have emerged as fertile ground for new therapeutic targets. The present challenge is to identify redox-dependent targets relevant to each cell cycle phase, to understand how these targets control fate decisions, and to describe the mechanisms that link metabolism to cell cycle progression.
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Affiliation(s)
- William C Burhans
- Department of Molecular & Cellular Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, USA
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Silencing of the Lats2 tumor suppressor overrides a p53-dependent oncogenic stress checkpoint and enables mutant H-Ras-driven cell transformation. Oncogene 2009; 28:4469-79. [PMID: 19855428 PMCID: PMC2795787 DOI: 10.1038/onc.2009.270] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The Lats2 tumor suppressor protein has previously been implicated in promoting p53 activation in response to mitotic apparatus stress, by preventing Mdm2-driven p53 degradation. We now report that Lats2 also plays a role in an ATR-Chk1-mediated stress checkpoint in response to oncogenic H-Ras. Activated mutant H-Ras triggers the translocation of Lats2 from centrosomes into the nucleus, coupled with an increase in Lats2 protein levels. This leads to induction of p53 activity, upregulation of proapoptotic genes, downregulation of antiapoptotic genes and eventually apoptotic cell death. Many of the cells that survive apoptosis undergo senescence. However, a fraction of the cells escape this checkpoint mechanism, despite maintaining high mutant H-Ras expression. These escapers display increased genome instability, as evidenced by a substantial fraction of cells with micronuclei and cells with polyploid genomes. Interestingly, such cells exhibit markedly reduced levels of Lats2, in conjunction with enhanced hypermethylation of the Lats2 gene promoter. Our findings suggest that Lats2 might play an important role in quenching H-Ras-induced transformation, while silencing of Lats2 expression might serve as a mechanism to enable tumor progression.
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Neubauer A, Maharry K, Mrózek K, Thiede C, Marcucci G, Paschka P, Mayer RJ, Larson RA, Liu ET, Bloomfield CD. Patients with acute myeloid leukemia and RAS mutations benefit most from postremission high-dose cytarabine: a Cancer and Leukemia Group B study. J Clin Oncol 2008; 26:4603-9. [PMID: 18559876 DOI: 10.1200/jco.2007.14.0418] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PURPOSE RAS mutations occur in 12% to 27% of patients with acute myeloid leukemia (AML) and enhance sensitivity to cytarabine in vitro. We examined whether RAS mutations impact response to cytarabine in vivo. PATIENTS AND METHODS One hundred eighty-five patients with AML achieving complete remission on Cancer and Leukemia Group B study 8525 and randomly assigned to one of three doses of cytarabine postremission were screened for RAS mutations. We assessed the impact of cytarabine dose on cumulative incidence of relapse (CIR) of patients with (mutRAS) and without (wild-type; wtRAS) RAS mutations. RESULTS Thirty-four patients (18%) had RAS mutations. With 12.9 years median follow-up, the 10-year CIR was similar for mutRAS and wtRAS patients (65% v 73%; P = .31). However, mutRAS patients receiving high-dose cytarabine consolidation (HDAC; 3 g/m(2) every 12 hours on days 1, 3, and 5 or 400 mg/m(2)/d x 5 days) had the lowest 10-year CIR, 45%, compared with 68% for wtRAS patients receiving HDAC and 80% and 100%, respectively, for wtRAS and mutRAS patients receiving low-dose cytarabine (LDAC; 100 mg/m(2)/d x 5 days; overall comparison, P < .001). Multivariable analysis revealed an interaction of cytarabine dose and RAS status (P = .06). After adjusting for this interaction and cytogenetics (core binding factor [CBF] AML v non-CBF AML), wtRAS patients receiving HDAC had lower relapse risk than wtRAS patients receiving LDAC (hazard ratio [HR] = 0.67; P = .04); however, mutRAS patients receiving HDAC had greater reduction in relapse risk (HR = 0.28; P = .002) compared with mutRAS patients treated with LDAC. CONCLUSION AML patients carrying mutRAS benefit from higher cytarabine doses more than wtRAS patients. This seems to be the first example of an activating oncogene mutation favorably modifying response to higher drug doses in AML.
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Affiliation(s)
- Andreas Neubauer
- Department for Hematology, Oncology and Immunology, Philipps University, Marburg, Germany
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TULA proteins bind to ABCE-1, a host factor of HIV-1 assembly, and inhibit HIV-1 biogenesis in a UBA-dependent fashion. Virology 2008; 372:10-23. [DOI: 10.1016/j.virol.2007.10.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Revised: 07/09/2007] [Accepted: 10/11/2007] [Indexed: 11/20/2022]
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Weinberger M, Feng L, Paul A, Smith DL, Hontz RD, Smith JS, Vujcic M, Singh KK, Huberman JA, Burhans WC. DNA replication stress is a determinant of chronological lifespan in budding yeast. PLoS One 2007; 2:e748. [PMID: 17710147 PMCID: PMC1939877 DOI: 10.1371/journal.pone.0000748] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Accepted: 07/13/2007] [Indexed: 11/19/2022] Open
Abstract
The chronological lifespan of eukaryotic organisms is extended by the mutational inactivation of conserved growth-signaling pathways that regulate progression into and through the cell cycle. Here we show that in the budding yeast S. cerevisiae, these and other lifespan-extending conditions, including caloric restriction and osmotic stress, increase the efficiency with which nutrient-depleted cells establish or maintain a cell cycle arrest in G1. Proteins required for efficient G1 arrest and longevity when nutrients are limiting include the DNA replication stress response proteins Mec1 and Rad53. Ectopic expression of CLN3 encoding a G1 cyclin downregulated during nutrient depletion increases the frequency with which nutrient depleted cells arrest growth in S phase instead of G1. Ectopic expression of CLN3 also shortens chronological lifespan in concert with age-dependent increases in genome instability and apoptosis. These findings indicate that replication stress is an important determinant of chronological lifespan in budding yeast. Protection from replication stress by growth-inhibitory effects of caloric restriction, osmotic and other stresses may contribute to hormesis effects on lifespan. Replication stress also likely impacts the longevity of higher eukaryotes, including humans.
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Affiliation(s)
- Martin Weinberger
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Li Feng
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Anita Paul
- Department of Cancer Biology, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Daniel L. Smith
- Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, Virginia, United States of America
| | - Robert D. Hontz
- Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, Virginia, United States of America
| | - Jeffrey S. Smith
- Department of Biochemistry and Molecular Genetics, University of Virginia Health System, Charlottesville, Virginia, United States of America
| | - Marija Vujcic
- Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Keshav K. Singh
- Department of Cancer Genetics, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - Joel A. Huberman
- Department of Cancer Biology, Roswell Park Cancer Institute, Buffalo, New York, United States of America
| | - William C. Burhans
- Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, New York, United States of America
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Tsygankova OM, Prendergast GV, Puttaswamy K, Wang Y, Feldman MD, Wang H, Brose MS, Meinkoth JL. Downregulation of Rap1GAP contributes to Ras transformation. Mol Cell Biol 2007; 27:6647-58. [PMID: 17646383 PMCID: PMC2099240 DOI: 10.1128/mcb.00155-07] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Although abundant in well-differentiated rat thyroid cells, Rap1GAP expression was extinguished in a subset of human thyroid tumor-derived cell lines. Intriguingly, Rap1GAP was downregulated selectively in tumor cell lines that had acquired a mesenchymal morphology. Restoring Rap1GAP expression to these cells inhibited cell migration and invasion, effects that were correlated with the inhibition of Rap1 and Rac1 activity. The reexpression of Rap1GAP also inhibited DNA synthesis and anchorage-independent proliferation. Conversely, eliminating Rap1GAP expression in rat thyroid cells induced a transient increase in cell number. Strikingly, Rap1GAP expression was abolished by Ras transformation. The downregulation of Rap1GAP by Ras required the activation of the Raf/MEK/extracellular signal-regulated kinase cascade and was correlated with the induction of mesenchymal morphology and migratory behavior. Remarkably, the acute expression of oncogenic Ras was sufficient to downregulate Rap1GAP expression in rat thyroid cells, identifying Rap1GAP as a novel target of oncogenic Ras. Collectively, these data implicate Rap1GAP as a putative tumor/invasion suppressor in the thyroid. In support of that notion, Rap1GAP was highly expressed in normal human thyroid cells and downregulated in primary thyroid tumors.
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Affiliation(s)
- Oxana M Tsygankova
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6061, USA
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