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Nagle PW, Hosper NA, Barazzuol L, Jellema AL, Baanstra M, van Goethem MJ, Brandenburg S, Giesen U, Langendijk JA, van Luijk P, Coppes RP. Lack of DNA Damage Response at Low Radiation Doses in Adult Stem Cells Contributes to Organ Dysfunction. Clin Cancer Res 2018; 24:6583-6593. [PMID: 30135147 DOI: 10.1158/1078-0432.ccr-18-0533] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 06/08/2018] [Accepted: 08/17/2018] [Indexed: 11/16/2022]
Abstract
PURPOSE Radiotherapy for head and neck cancer may result in serious side effects, such as hyposalivation, impairing the patient's quality of life. Modern radiotherapy techniques attempt to reduce the dose to salivary glands, which, however, results in low-dose irradiation of the tissue stem cells. Here we assess the low-dose sensitivity of tissue stem cells and the consequences for tissue function. EXPERIMENTAL DESIGN Postirradiation rat salivary gland secretory function was determined after pilocarpine induction. Murine and patient-derived salivary gland and thyroid gland organoids were irradiated and clonogenic survival was assessed. The DNA damage response (DDR) was analyzed in organoids and modulated using different radiation modalities, chemical inhibition, and genetic modification. RESULTS Relative low-dose irradiation to the high-density stem cell region of rat salivary gland disproportionally impaired function. Hyper-radiosensitivity at doses <1 Gy, followed by relative radioresistance at doses ≥1 Gy, was observed in salivary gland and thyroid gland organoid cultures. DDR modulation resulted in diminished, or even abrogated, relative radioresistance. Furthermore, inhibition of the DDR protein ATM impaired DNA repair after 1 Gy, but not 0.25 Gy. Irradiation of patient-derived salivary gland organoid cells showed similar responses, whereas a single 1 Gy dose to salivary gland-derived stem cells resulted in greater survival than clinically relevant fractionated doses of 4 × 0.25 Gy. CONCLUSIONS We show that murine and human glandular tissue stem cells exhibit a dose threshold in DDR activation, resulting in low-dose hyper-radiosensitivity, with clinical implications in radiotherapy treatment planning. Furthermore, our results from patient-derived organoids highlight the potential of organoids to study normal tissue responses to radiation.
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Affiliation(s)
- Peter W Nagle
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.,Department of Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Nynke A Hosper
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.,Department of Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Lara Barazzuol
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.,Department of Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Anne L Jellema
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.,Department of Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Mirjam Baanstra
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.,Department of Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Marc-Jan van Goethem
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.,KVI Center for Advanced Radiation Technology, University of Groningen, Groningen, the Netherlands
| | - Sytze Brandenburg
- KVI Center for Advanced Radiation Technology, University of Groningen, Groningen, the Netherlands
| | - Ulrich Giesen
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany
| | - Johannes A Langendijk
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Peter van Luijk
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
| | - Rob P Coppes
- Department of Radiation Oncology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands. .,Department of Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands
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2
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Zhang YH, Huang T, Chen L, Xu Y, Hu Y, Hu LD, Cai Y, Kong X. Identifying and analyzing different cancer subtypes using RNA-seq data of blood platelets. Oncotarget 2017; 8:87494-87511. [PMID: 29152097 PMCID: PMC5675649 DOI: 10.18632/oncotarget.20903] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 08/16/2017] [Indexed: 12/11/2022] Open
Abstract
Detection and diagnosis of cancer are especially important for early prevention and effective treatments. Traditional methods of cancer detection are usually time-consuming and expensive. Liquid biopsy, a newly proposed noninvasive detection approach, can promote the accuracy and decrease the cost of detection according to a personalized expression profile. However, few studies have been performed to analyze this type of data, which can promote more effective methods for detection of different cancer subtypes. In this study, we applied some reliable machine learning algorithms to analyze data retrieved from patients who had one of six cancer subtypes (breast cancer, colorectal cancer, glioblastoma, hepatobiliary cancer, lung cancer and pancreatic cancer) as well as healthy persons. Quantitative gene expression profiles were used to encode each sample. Then, they were analyzed by the maximum relevance minimum redundancy method. Two feature lists were obtained in which genes were ranked rigorously. The incremental feature selection method was applied to the mRMR feature list to extract the optimal feature subset, which can be used in the support vector machine algorithm to determine the best performance for the detection of cancer subtypes and healthy controls. The ten-fold cross-validation for the constructed optimal classification model yielded an overall accuracy of 0.751. On the other hand, we extracted the top eighteen features (genes), including TTN, RHOH, RPS20, TRBC2, in another feature list, the MaxRel feature list, and performed a detailed analysis of them. The results indicated that these genes could be important biomarkers for discriminating different cancer subtypes and healthy controls.
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Affiliation(s)
- Yu-Hang Zhang
- Department of General Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, People's Republic of China.,Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
| | - Tao Huang
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
| | - Lei Chen
- College of Information Engineering, Shanghai Maritime University, Shanghai 201306, People's Republic of China
| | - YaoChen Xu
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
| | - Yu Hu
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
| | - Lan-Dian Hu
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
| | - Yudong Cai
- School of Life Sciences, Shanghai University, Shanghai 200444, People's Republic of China
| | - Xiangyin Kong
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
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3
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A coordinated DNA damage response promotes adult quiescent neural stem cell activation. PLoS Biol 2017; 15:e2001264. [PMID: 28489848 PMCID: PMC5424956 DOI: 10.1371/journal.pbio.2001264] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 03/31/2017] [Indexed: 11/24/2022] Open
Abstract
Stem and differentiated cells frequently differ in their response to DNA damage, which can determine tissue sensitivity. By exploiting insight into the spatial arrangement of subdomains within the adult neural subventricular zone (SVZ) in vivo, we show distinct responses to ionising radiation (IR) between neural stem and progenitor cells. Further, we reveal different DNA damage responses between neonatal and adult neural stem cells (NSCs). Neural progenitors (transit amplifying cells and neuroblasts) but not NSCs (quiescent and activated) undergo apoptosis after 2 Gy IR. This response is cell type- rather than proliferation-dependent and does not appear to be driven by distinctions in DNA damage induction or repair capacity. Moreover, exposure to 2 Gy IR promotes proliferation arrest and differentiation in the adult SVZ. These 3 responses are ataxia telangiectasia mutated (ATM)-dependent and promote quiescent NSC (qNSC) activation, which does not occur in the subdomains that lack progenitors. Neuroblasts arising post-IR derive from activated qNSCs rather than irradiated progenitors, minimising damage compounded by replication or mitosis. We propose that rather than conferring sensitive cell death, apoptosis is a form of rapid cell death that serves to remove damaged progenitors and promote qNSC activation. Significantly, analysis of the neonatal (P5) SVZ reveals that although progenitors remain sensitive to apoptosis, they fail to efficiently arrest proliferation. Consequently, their repopulation occurs rapidly from irradiated progenitors rather than via qNSC activation. The response of stem cells to DNA damage is poorly understood, although there is increasing evidence that they respond distinctly to differentiated cells. We have monitored the different responses of adult neural stem and progenitor cells to exposure to X-ray irradiation. We see that progenitor cells activate apoptosis, undergo rapid proliferation arrest, and premature differentiation. However, quiescent stem cells do not activate radiation-induced apoptosis. Instead the responses of the progenitor cells promote the activation of these quiescent neural stem cells, thereby replenishing the neuroblasts. These responses and quiescent stem cell activation are dependent on the ataxia telangiectasia mutated (ATM) kinase. We propose that this coordinated response functions to remove damaged progenitor cells and to aid repopulation.
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4
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Kiang JG, Garrison BR, Smith JT, Fukumoto R. Ciprofloxacin as a potential radio-sensitizer to tumor cells and a radio-protectant for normal cells: differential effects on γ-H2AX formation, p53 phosphorylation, Bcl-2 production, and cell death. Mol Cell Biochem 2014; 393:133-43. [PMID: 24802382 PMCID: PMC4122264 DOI: 10.1007/s11010-014-2053-z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 04/03/2014] [Indexed: 02/07/2023]
Abstract
Ionizing radiation increases cell mortality in a dose-dependent manner. Increases in DNA double strand breaks, γ-H2AX, p53 phophorylation, and protein levels of p53 and Bax also occur. We investigated the ability of ciprofloxacin (CIP), a widely prescribed antibiotic, to inhibit DNA damage induced by ionizing radiation. Human tumor TK6, NH32 (p53 (-/-) of TK6) cells, and human normal peripheral blood mononuclear cells (PBMCs) were exposed to 2-8 Gy (60)Co-γ-photon radiation. γ-H2AX (an indicator of DNA strand breaks), phosphorylated p53 (responsible for cell-cycle arrest), Bcl-2 (an apoptotic protein, and cell death were measured. Ionizing irradiation increased γ-H2AX amounts in TK6 cells (p53(+/+)) within 1 h in a radiation dose-dependent manner. CIP pretreatment and posttreatment effectively inhibited the increase in γ-H2AX. CIP pretreatment reduced Bcl-2 production but promoted p53 phosphorylation, caspase-3 activation and cell death. In NH32 cells, CIP failed to significantly inhibit the radiation-induced γ-H2AX increase, suggesting that CIP inhibition involves in p53-dependent mechanisms. In normal healthy human PBMCs, CIP failed to block the radiation-induced γ-H2AX increase but effectively increased Bcl-2 production, but blocked the phospho-p53 increase and subsequent cell death. CIP increased Gadd45α, and enhanced p21 protein 24 h postirradiation. Results suggest that CIP exerts its effect in TK6 cells by promoting p53 phosphorylation and inhibiting Bcl-2 production and in PBMCs by inhibiting p53 phosphorylation and increasing Bcl-2 production. Our data are the first to support the view that CIP may be effective to protect normal tissue cells from radiation injury, while enhancing cancer cell death in radiation therapy.
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Affiliation(s)
- Juliann G Kiang
- Radiation Combined Injury Program, Scientific Research Department, Armed Forces Radiobiology Research Institute, Bethesda, MD, 20889-5603, USA,
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5
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Activation of AMP-activated protein kinase in cerebella of Atm-/- mice is attributable to accumulation of reactive oxygen species. Biochem Biophys Res Commun 2012; 418:267-72. [PMID: 22260947 DOI: 10.1016/j.bbrc.2012.01.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2011] [Accepted: 01/03/2012] [Indexed: 12/13/2022]
Abstract
Ataxia telangiectasia (A-T) is an inherited disease, the most prominent feature of which is ataxia caused by degeneration of cerebellar neurons and synapses. The mechanisms underlying A-T neurodegeneration are still unclear, and many factors are likely to be involved. AMP-activated protein kinase (AMPK) is a sensor of energy balance, and research on its function in neural cells has gained momentum in the last decade. The dual roles of AMPK in neuroprotection and neurodegeneration are complex, and they need to be identified and characterized. Using an Atm (ataxia telangiectasia mutated) gene deficient mouse model, we showed here that: (a) upregulation of AMPK phosphorylation and elevation of reactive oxygen species (ROS) coordinately occur in the cerebella of Atm-/- mice; (b) hydrogen peroxide induces AMPK phosphorylation in primary mouse cerebellar astrocytes in an Atm-independent manner; (c) administration of the novel antioxidant monosodium luminol (MSL) to Atm-/- mice attenuates the upregulation of both phosphorylated-AMPK (p-AMPK) and ROS, and corrects the neuromotor deficits in these animals. Together, our results suggest that oxidative activation of AMPK in the cerebellum may contribute to the neurodegeneration in Atm-/- mice, and that ROS and AMPK signaling pathways are promising therapeutic targets for treatment of A-T and other neurodegenerative diseases.
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6
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Abstract
The embryonic ventricular and subventricular zones (VZ/SVZ) contain the neuronal stem and progenitor cells and undergo rapid proliferation. The intermediate zone (IZ) contains nonreplicating, differentiated cells. The VZ/SVZ is hypersensitive to radiation-induced apoptosis. Ablation of DNA non-homologous end-joining (NHEJ) proteins, XRCC4 or DNA ligase IV (LigIV), confers ataxia telangiectasia mutated (ATM)-dependent apoptosis predominantly in the IZ. We examine the mechanistic basis underlying these distinct sensitivities using a viable LigIV (Lig4(Y288C)) mouse, which permits an examination of the DNA damage responses in the embryonic and adult brain. Via combined analysis of DNA breakage, apoptosis, and cell-cycle checkpoint control in tissues, we show that apoptosis in the VZ/SVZ and IZ is activated by low numbers of DNA double-strand breaks (DSBs). Unexpectedly, high sensitivity in the VZ/SVZ arises from sensitive activation of ATM-dependent apoptosis plus an ATM-independent process. In contrast, the IZ appears to be hypersensitive to persistent DSBs. NHEJ functions efficiently in both compartments. The VZ/SVZ and IZ regions incur high endogenous DNA breakage, which correlates with VZ proliferation. We demonstrate a functional G(2)/M checkpoint in VZ/SVZ cells and show that it is not activated by low numbers of DSBs, allowing damaged VZ/SVZ cells to transit into the IZ. We propose a novel model in which microcephaly in LIG4 syndrome arises from sensitive apoptotic induction from persisting DSBs in the IZ, which arise from high endogenous breakage in the VZ/SVZ and transit of damaged cells to the IZ. The VZ/SVZ, in contrast, is highly sensitive to acute radiation-induced DSB formation.
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7
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Defining the ATM-mediated barrier to tumorigenesis in somatic mammary cells following ErbB2 activation. Proc Natl Acad Sci U S A 2010; 107:3728-33. [PMID: 20133707 DOI: 10.1073/pnas.0910665107] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
p53, apoptosis, and senescence are frequently activated in preneoplastic lesions and are barriers to progression to malignancy. These barriers have been suggested to result from an ATM-mediated DNA damage response (DDR), which may follow oncogene-induced hyperproliferation and ensuing DNA replication stress. To elucidate the currently untested role of DDR in breast cancer initiation, we examined the effect of oncogene expression in several murine models of breast cancer. We did not observe a detectable DDR in early hyperplastic lesions arising in transgenic mice expressing several different oncogenes. However, DDR signaling was strongly induced in preneoplastic lesions arising from individual mammary cells transduced in vivo by retroviruses expressing either PyMT or ErbB2. Thus, activation of an oncogene after normal tissue development causes a DDR. Furthermore, in this somatic ErbB2 tumor model, ATM, and thus DDR, is required for p53 stabilization, apoptosis, and senescence. In palpable tumors in this model, p53 stabilization and apoptosis are lost, but unexpectedly senescence remains in many tumor cells. Thus, this murine model fully recapitulates early DDR signaling; the eventual suppression of its endpoints in tumorigenesis provides compelling evidence that ErbB2-induced aberrant mammary cell proliferation leads to an ATM-mediated DDR that activates apoptosis and senescence, and at least the former must be overcome to progress to malignancy. This in vivo study also uncovers an unexpected effect of ErbB2 activation previously known for its prosurvival roles, and suggests that protection of the ATM-mediated DDR-p53 signaling pathway may be important in breast cancer prevention.
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8
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Kuang X, Shen J, Wong PK, Yan M. Deregulation of mTOR signaling is involved in thymic lymphoma development in Atm−/− mice. Biochem Biophys Res Commun 2009; 383:368-72. [DOI: 10.1016/j.bbrc.2009.04.019] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Accepted: 04/03/2009] [Indexed: 12/18/2022]
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9
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Efeyan A, Murga M, Martinez-Pastor B, Ortega-Molina A, Soria R, Collado M, Fernandez-Capetillo O, Serrano M. Limited role of murine ATM in oncogene-induced senescence and p53-dependent tumor suppression. PLoS One 2009; 4:e5475. [PMID: 19421407 PMCID: PMC2675057 DOI: 10.1371/journal.pone.0005475] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Accepted: 03/27/2009] [Indexed: 01/03/2023] Open
Abstract
Recent studies in human fibroblasts have provided a new general paradigm of tumor suppression according to which oncogenic signaling produces DNA damage and this, in turn, results in ATM/p53-dependent cellular senescence. Here, we have tested this model in a variety of murine experimental systems. Overexpression of oncogenic Ras in murine fibroblasts efficiently induced senescence but this occurred in the absence of detectable DNA damage signaling, thus suggesting a fundamental difference between human and murine cells. Moreover, lung adenomas initiated by endogenous levels of oncogenic K-Ras presented abundant senescent cells, but undetectable DNA damage signaling. Accordingly, K-Ras-driven adenomas were also senescent in Atm-null mice, and the tumorigenic progression of these lesions was only modestly accelerated by Atm-deficiency. Finally, we have examined chemically-induced fibrosarcomas, which possess a persistently activated DNA damage response and are highly sensitive to the activity of p53. We found that the absence of Atm favored genomic instability in the resulting tumors, but did not affect the persistent DNA damage response and did not impair p53-dependent tumor suppression. All together, we conclude that oncogene-induced senescence in mice may occur in the absence of a detectable DNA damage response. Regarding murine Atm, our data suggest that it plays a minor role in oncogene-induced senescence or in p53-dependent tumor suppression, being its tumor suppressive activity probably limited to the maintenance of genomic stability.
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Affiliation(s)
- Alejo Efeyan
- Tumor Suppression Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Matilde Murga
- Genomic Instability Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | | | - Ana Ortega-Molina
- Tumor Suppression Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Rebeca Soria
- Genomic Instability Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Manuel Collado
- Tumor Suppression Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | | | - Manuel Serrano
- Tumor Suppression Group, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
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10
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Sáenz Robles MT, Pipas JM. T antigen transgenic mouse models. Semin Cancer Biol 2009; 19:229-35. [PMID: 19505650 DOI: 10.1016/j.semcancer.2009.02.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 02/03/2009] [Accepted: 02/06/2009] [Indexed: 01/12/2023]
Abstract
The study of polyomavirus has benefited immensely from two scientific methodologies, cell culture and in vitro studies on one side and the use of transgenic mice as experimental models on the other. Both approaches allowed us to identify cellular products targeted by the viruses, the consequences of these interactions at the phenotypic and molecular level, and thus the potential roles of the targets within their normal cellular context. In particular, cell culture and in vitro reports suggest a model explaining partially how SV40 large T antigen contributes to oncogenic transformation. In most cases, T antigen induces cell cycle entry by inactivation of the Rb proteins (pRb, p130, and p107), thus activating E2F-dependent transcription and subsequent S-phase entry. Simultaneously, T antigen blocks p53 activity and therefore prevents the ensuing cell-cycle arrest and apoptosis. For the most part, studies of T antigen expression in transgenic mice support this model, but the use of T antigen mutants and their expression in different tissue and cell type settings have expanded our knowledge of the model system and raised important questions regarding tumorigenic mechanisms functioning in vivo.
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11
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Abstract
Oncogenes can induce p53 through a signaling pathway involving p19/Arf. It was recently proposed that oncogenes can also induce DNA damage, and this can induce p53 through the Atm DNA damage pathway. To assess the relative roles of Atm, Arf, and p53 in the suppression of Ras-driven tumors, we examined susceptibility to skin carcinogenesis in 7,12-dimethylbenz(a)anthracene/12-O-tetradecanoylphorbol-13-acetate (TPA)-treated Atm- and p53-deficient mice and compared these results to previous studies on Arf-deficient mice. Mice with epidermal-specific deletion of p53 showed increased papilloma number and progression to malignant invasive carcinomas compared with wild-type littermates. In contrast, Atm-deficient mice showed no increase in papilloma number, growth, or malignant progression. gamma-H2AX and p53 levels were increased in both Atm(+/+) and Atm(-/-) papillomas, whereas Arf(-/-) papillomas showed much lower p53 expression. Thus, although there is evidence of DNA damage, signaling through Arf seems to regulate p53 in these Ras-driven tumors. In spontaneous and radiation-induced lymphoma models, tumor latency was accelerated in Atm(-/-)p53(-/-) compound mutant mice compared with the single mutant Atm(-/-) or p53(-/-) mice, indicating cooperation between loss of Atm and loss of p53. Although p53-mediated apoptosis was impaired in irradiated Atm(-/-) lymphocytes, p53 loss was still selected for during lymphomagenesis in Atm(-/-) mice. In conclusion, in these models of oncogene- or DNA damage-induced tumors, p53 retains tumor suppressor activity in the absence of Atm.
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Affiliation(s)
- S. Lawrence Bailey
- Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N. Seattle WA, 90109-1024, USA
| | - Kay E. Gurley
- Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N. Seattle WA, 90109-1024, USA
| | | | - Karen S. Kelly-Spratt
- Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N. Seattle WA, 90109-1024, USA
| | - Christopher J. Kemp
- Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N. Seattle WA, 90109-1024, USA
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12
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Endoplasmic reticulum stress and unfolded protein response in Atm-deficient thymocytes and thymic lymphoma cells are attributable to oxidative stress. Neoplasia 2008; 10:160-7. [PMID: 18283338 DOI: 10.1593/neo.07935] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 11/29/2007] [Accepted: 12/03/2007] [Indexed: 01/11/2023] Open
Abstract
Both oxidative stress and endoplasmic reticulum (ER) stress have been implicated in carcinogenesis. It is well documented that cells deficient in the ataxia-telangiectasia mutated (ATM) gene undergo oxidative stress, which is critically involved in thymic lymphomagenesis in Atm-/- mice. Here we demonstrate that undifferentiated Atm-/- thymocytes show signs of ER stress and of the unfolded protein response (UPR). Using two-dimensional (2-D) gel electrophoresis and mass spectrometry (MS) analysis, we identified 22 differentially expressed proteins, including the ER stress marker glucose-regulated protein 78 (GRP78), in Atm-/- thymocytes and in Atm-/- thymic lymphoma cells relative to Atm+/+ thymocytes. The phosphorylated alpha subunit of eukaryotic translation initiation factor 2 (p-eIF2alpha), a UPR marker, was also increased in Atm-/- thymocytes. Cells of the ATL-1 line, which were derived from an Atm-/- mouse thymic lymphoma, were more sensitive to the ER stress inducer tunicamycin than were Atm+/+ thymic leukemia ASL-1 cells. Notably, treatment with hydrogen peroxide duplicated the effects of ATM deficiency in cultured thymocytes, and treatment with the novel cell-permeable thiol antioxidant N-acetylcysteine amide (AD4) reduced elevated p-eIF2alpha levels in thymocytes of Atm-/- mice. Thus, we propose that ER stress and the UPR are secondary to oxidative stress in Atm-/- thymocytes.
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Gurley KE, Kemp CJ. Ataxia-telangiectasia mutated is not required for p53 induction and apoptosis in irradiated epithelial tissues. Mol Cancer Res 2008; 5:1312-8. [PMID: 18171989 DOI: 10.1158/1541-7786.mcr-07-0223] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The ataxia-telangiectasia mutated (Atm) protein kinase is a central regulator of the cellular response to DNA damage. Although Atm can regulate p53, it is not known if this Atm function varies between tissues. Previous studies showed that the induction of p53 and apoptosis by whole-body ionizing radiation varies greatly between tissue and tumor types, so here we asked if Atm also had a tissue-specific role in the ionizing radiation response. Irradiated Atm-null mice showed impaired p53 induction and apoptosis in thymus, spleen, and brain. In contrast, radiation-induced p53, apoptosis, phosphorylation of Chk2, and G(2)-M cell cycle arrest were slightly delayed in Atm(-/-) epithelial cells of the small intestine but reached wild-type levels by 4 h. Radiation-induced p53 and apoptosis in Atm(-/-) hair follicle epithelial cells were not impaired at any of the time points examined. Thus, Atm is essential for radiation-induced apoptosis in lymphoid tissues but is largely dispensable in epithelial cells. This indicates that marked differences in DNA damage signaling pathways exist between tissues, which could explain some of the tissue-specific phenotypes, especially tumor suppression, associated with Atm deficiency.
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Affiliation(s)
- Kay E Gurley
- Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, C1-015, Seattle, WA 90109-1024, USA
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14
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Yan M, Kuang X, Scofield VL, Shen J, Lynn WS, Wong PKY. The glucocorticoid receptor is increased in Atm-/- thymocytes and in Atm-/- thymic lymphoma cells, and its nuclear translocation counteracts c-myc expression. Steroids 2007; 72:415-21. [PMID: 17418878 DOI: 10.1016/j.steroids.2007.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Revised: 01/25/2007] [Accepted: 02/21/2007] [Indexed: 01/01/2023]
Abstract
We have previously demonstrated that spontaneous DNA synthesis in immature thymocytes of Atm-/- mice is elevated, and that treatment with the glucocorticoid dexamethasone (Dex) attenuates this increased DNA synthesis and prevents the development of thymic lymphomas. Deregulation of c-myc may drive the uncontrolled proliferation of Atm-/- thymocytes, since upregulation of c-myc parallels the elevated DNA synthesis in the cells. In this study, we show that the glucocorticoid receptor (GR) is expressed at high levels in Atm-/- thymocytes and in Atm-/- thymic lymphoma cells, although serum glucocorticoid (GC) levels in Atm-/- mice are similar to those in Atm+/+ mice. In cultured Atm-/- thymic lymphoma cells treated with Dex, GR nuclear translocation occurs, resulting in suppression of DNA synthesis and c-myc expression at both the mRNA and protein levels. Interestingly, the GR antagonist RU486 also causes GR nuclear translocation, but does not affect DNA synthesis and c-myc expression in Atm-/- thymic lymphoma cells. As expected, RU486 reverses the suppressive effects of Dex on DNA synthesis and c-myc expression. Administration of Dex to Atm-/- mice decreases the elevated c-Myc protein levels in their thymocytes. These findings suggest that GC/GR signaling plays an important role in regulating c-myc expression in Atm-/- thymocytes and thymic lymphoma cells.
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Affiliation(s)
- Mingshan Yan
- The University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, 1808 Park Road 1C, Smithville, TX 78957, USA.
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Christophorou MA, Ringshausen I, Finch AJ, Swigart LB, Evan GI. The pathological response to DNA damage does not contribute to p53-mediated tumour suppression. Nature 2006; 443:214-7. [PMID: 16957739 DOI: 10.1038/nature05077] [Citation(s) in RCA: 307] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2006] [Accepted: 07/13/2006] [Indexed: 12/14/2022]
Abstract
The p53 protein has a highly evolutionarily conserved role in metazoans as 'guardian of the genome', mediating cell-cycle arrest and apoptosis in response to genotoxic injury. In large, long-lived animals with substantial somatic regenerative capacity, such as vertebrates, p53 is an important tumour suppressor--an attribute thought to stem directly from its induction of death or arrest in mutant cells with damaged or unstable genomes. Chemotherapy and radiation exposure both induce widespread p53-dependent DNA damage. This triggers potentially lethal pathologies that are generally deemed an unfortunate but unavoidable consequence of the role p53 has in tumour suppression. Here we show, using a mouse model in which p53 status can be reversibly switched in vivo between functional and inactive states, that the p53-mediated pathological response to whole-body irradiation, a prototypical genotoxic carcinogen, is irrelevant for suppression of radiation-induced lymphoma. In contrast, delaying the restoration of p53 function until the acute radiation response has subsided abrogates all of the radiation-induced pathology yet preserves much of the protection from lymphoma. Such protection is absolutely dependent on p19(ARF)--a tumour suppressor induced not by DNA damage, but by oncogenic disruption of the cell cycle.
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Affiliation(s)
- M A Christophorou
- Cancer Research Institute and Department of Cellular & Molecular Pharmacology, Comprehensive Cancer Center, University of California, San Francisco, California 94143, USA
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16
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Reliene R, Schiestl RH. Antioxidant N-acetyl cysteine reduces incidence and multiplicity of lymphoma in Atm deficient mice. DNA Repair (Amst) 2006; 5:852-9. [PMID: 16781197 DOI: 10.1016/j.dnarep.2006.05.003] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Accepted: 05/04/2006] [Indexed: 11/23/2022]
Abstract
Hereditary human disorder ataxia telangiectasia (AT) is characterized by an extremely high incidence of lymphoid malignancies, neuromotor dysfunction, immunodeficiency and radiosensitivity. Cells from AT patients show genetic instability and a continuous state of oxidative stress. We examined the effect of long-term dietary supplementation with the thiol-containing antioxidant, N-acetyl-L-cysteine (NAC), on survival and cancer formation in Atm (AT-mutated) deficient mice, used as an animal model of AT. NAC was chosen because it is well-tolerated in animals and humans. It can be used by the oral route and for long-term at high concentrations. In addition, NAC suppresses carcinogenesis-associated biological markers in Atm deficient mice, such as DNA deletions and oxidative DNA damage (R. Reliene, E. Fischer, R.H. Schiestl, Effect of N-acetyl cysteine on oxidative DNA damage and the frequency of DNA deletions in atm-deficient mice, Cancer Res. 64 (2004) 5148-5153). In this study, NAC significantly increased the lifespan and reduced both the incidence and multiplicity of lymphoma in Atm deficient mice. The life span increased from 50 to 68 weeks and the incidence of lymphoma decreased by two-fold (76.5% versus 37.5%). Moreover, in mice with lymphoma, multiplicity of tumors decreased from 4.6 to 2.8 tumors per mouse. Thus, dietary supplementation with NAC may turn out to be protective against lymphomagenesis in AT patients.
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Affiliation(s)
- Ramune Reliene
- Department of Pathology, Geffen School of Medicine and School of Public Health, UCLA, 650 Charles E. Young Drive South, Los Angeles, CA 90095, USA
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17
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Pusapati RV, Rounbehler RJ, Hong S, Powers JT, Yan M, Kiguchi K, McArthur MJ, Wong PK, Johnson DG. ATM promotes apoptosis and suppresses tumorigenesis in response to Myc. Proc Natl Acad Sci U S A 2006; 103:1446-51. [PMID: 16432227 PMCID: PMC1345703 DOI: 10.1073/pnas.0507367103] [Citation(s) in RCA: 117] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2005] [Accepted: 12/09/2005] [Indexed: 01/24/2023] Open
Abstract
Overexpression of the c-myc oncogene contributes to the development of a significant number of human cancers. In response to deregulated Myc activity, the p53 tumor suppressor is activated to promote apoptosis and inhibit tumor formation. Here we demonstrate that p53 induction in response to Myc overexpression requires the ataxia-telangiectasia mutated (ATM) kinase, a major regulator of the cellular response to DNA double-strand breaks. In a transgenic mouse model overexpressing Myc in squamous epithelial tissues, inactivation of Atm suppresses apoptosis and accelerates tumorigenesis. Deregulated Myc expression induces DNA damage in primary transgenic keratinocytes and the formation of gammaH2AX and phospho-SMC1 foci in transgenic tissue. These findings suggest that Myc overexpression causes DNA damage in vivo and that the ATM-dependent response to this damage is critical for p53 activation, apoptosis, and the suppression of tumor development.
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Affiliation(s)
- Raju V Pusapati
- Department of Carcinogenesis, University of Texas M. D. Anderson Cancer Center, Science Park Research Division, 1808 Park Road 1C, Smithville, TX 78957, USA
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18
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Dahl J, You J, Benjamin TL. Induction and utilization of an ATM signaling pathway by polyomavirus. J Virol 2005; 79:13007-17. [PMID: 16189003 PMCID: PMC1235815 DOI: 10.1128/jvi.79.20.13007-13017.2005] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Progression from G(1) to S is essential for polyomavirus DNA replication and depends on the interaction of large T with the retinoblastoma gene product pRb. This virus-induced replication pathway is accompanied by p53 activation resembling a DNA damage response (12). We sought to determine whether this pathway depends in part on activation of the ATM (ataxia telangiectasia mutated) kinase and whether the virus gains advantages from this pathway beyond that of entry into S. We show that polyomavirus infection activates the S- and G(2)-phase checkpoints in primary as well as established mouse cells. Infected cells undergo a prolonged S phase compared to uninfected serum-stimulated cells and show no evidence of a G(2)-->M transition before lytic death ensues. Infection is accompanied by increases in ATM activity in vitro and in the level of ATM-S1981-P in vivo. The incubation of infected cells with caffeine, a known ATM inhibitor, did not block entry into S but reduced the rate of viral compared to cellular DNA synthesis. Importantly, caffeine lowered the yields of viral DNA an average of 3- to 6-fold and those of infectious virus by as much as 10-fold. Virus yields were 10-fold lower in ATM (-/-) p53(-/-) than in ATM(+/+) p53(-/-) mouse embryo fibroblasts, indicating a p53-independent role of ATM in productive infection. Replacement of the normal SMC1 (structural maintenance of chromosomes, or cohesin) protein, a critical ATM substrate in the DNA repair pathway, with its phosphorylation mutant SMC1(S957AS966A) also lowered virus yields by roughly 90%. We suggest that polyomavirus activates and utilizes a component(s) of an ATM pathway of DNA repair to prolong S phase and aid its own replication.
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Affiliation(s)
- Jean Dahl
- Department of Pathology, Harvard Medical School, Boston, MA 02115, USA
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19
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Abstract
Mutations that drive uncontrolled cell-cycle progression are requisite events in tumorigenesis. But evolution has installed in the proliferative programmes of mammalian cells a variety of innate tumour-suppressive mechanisms that trigger apoptosis or senescence, should proliferation become aberrant. These contingent processes rely on a series of sensors and transducers that act in a coordinated network to target the machinery responsible for apoptosis and cell-cycle arrest at different points. Although oncogenic mutations that disable such networks can have profound and varied effects on tumour evolution, they may leave intact latent tumour-suppressive potential that can be harnessed therapeutically.
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Affiliation(s)
- Scott W Lowe
- Cold Spring Harbor Laboratory, 1 Bungtown Road, Cold Spring Harbor, New York 11724, USA.
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20
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Lumsden JM, McCarty T, Petiniot LK, Shen R, Barlow C, Wynn TA, Morse HC, Gearhart PJ, Wynshaw-Boris A, Max EE, Hodes RJ. Immunoglobulin class switch recombination is impaired in Atm-deficient mice. ACTA ACUST UNITED AC 2004; 200:1111-21. [PMID: 15504820 PMCID: PMC2211853 DOI: 10.1084/jem.20041074] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Immunoglobulin class switch recombination (Ig CSR) involves DNA double strand breaks (DSBs) at recombining switch regions and repair of these breaks by nonhomologous end-joining. Because the protein kinase ataxia telengiectasia (AT) mutated (ATM) plays a critical role in DSB repair and AT patients show abnormalities of Ig isotype expression, we assessed the role of ATM in CSR by examining ATM-deficient mice. In response to T cell–dependent antigen (Ag), Atm−/− mice secreted substantially less Ag-specific IgA, IgG1, IgG2b, and IgG3, and less total IgE than Atm+/+ controls. To determine whether Atm−/− B cells have an intrinsic defect in their ability to undergo CSR, we analyzed in vitro responses of purified B cells. Atm−/− cells secreted substantially less IgA, IgG1, IgG2a, IgG3, and IgE than wild-type (WT) controls in response to stimulation with lipopolysaccharide, CD40 ligand, or anti-IgD plus appropriate cytokines. Molecular analysis of in vitro responses indicated that WT and Atm−/− B cells produced equivalent amounts of germline IgG1 and IgE transcripts, whereas Atm−/− B cells produced markedly reduced productive IgG1 and IgE transcripts. The reduction in isotype switching by Atm−/− B cells occurs at the level of genomic DNA recombination as measured by digestion–circularization PCR. Analysis of sequences at CSR sites indicated that there is greater microhomology at the μ–γ1 switch junctions in ATM B cells than in wild-type B cells, suggesting that ATM function affects the need or preference for sequence homology in the CSR process. These findings suggest a role of ATM in DNA DSB recognition and/or repair during CSR.
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Affiliation(s)
- Joanne M Lumsden
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bldg. 10, Room 4B10, 10 Center Dr., Bethesda, MD 20892, USA.
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21
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Reliene R, Fischer E, Schiestl RH. Effect of N-acetyl cysteine on oxidative DNA damage and the frequency of DNA deletions in atm-deficient mice. Cancer Res 2004; 64:5148-53. [PMID: 15289318 DOI: 10.1158/0008-5472.can-04-0442] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Ataxia telangiectasia (AT) is a hereditary human disorder resulting in a wide variety of clinical manifestations, including progressive neurodegeneration, immunodeficiency, and high incidence of lymphoid tumors. Cells from patients with AT show genetic instability, hypersensitivity to radiation, and a continuous state of oxidative stress. Oxidative stress and genetic instability, including DNA deletions, are involved in carcinogenesis. We examined the effect of dietary supplementation with the thiol-containing antioxidant N-acetyl-l-cysteine (NAC) on levels of oxidative DNA damage and the frequency of DNA deletions in Atm-deficient (AT-mutated) mice. We confirmed that Atm-deficient mice display an increased frequency of DNA deletions (Bishop et al., Cancer Res 2000;60:395). Furthermore, we found that Atm-deficient mice have significantly increased levels of 8-OH deoxyguanosine, an indication of oxidative DNA damage. Dietary supplementation with NAC significantly reduced 8-OH deoxyguanosine level and the frequency of DNA deletions in Atm-deficient mice. These levels were similar to the levels in wild-type mice. Our findings demonstrate that NAC counteracts genetic instability and suggest that genetic instability may be a consequence of oxidative stress in Atm-deficient mice.
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Affiliation(s)
- Ramune Reliene
- Department of Pathology, Geffen School of Medicine and School of Public Health, University of California-Los Angeles, 650 Charles E. Young Drive South, Los Angeles, CA 90024, USA
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22
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Rogoff HA, Pickering MT, Frame FM, Debatis ME, Sanchez Y, Jones S, Kowalik TF. Apoptosis associated with deregulated E2F activity is dependent on E2F1 and Atm/Nbs1/Chk2. Mol Cell Biol 2004; 24:2968-77. [PMID: 15024084 PMCID: PMC371110 DOI: 10.1128/mcb.24.7.2968-2977.2004] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The retinoblastoma protein (Rb)/E2F pathway links cellular proliferation control to apoptosis and is critical for normal development and cancer prevention. Here we define a transcription-mediated pathway in which deregulation of E2F1 by ectopic E2F expression or Rb inactivation by E7 of human papillomavirus type 16 signals apoptosis by inducing the expression of Chk2, a component of the DNA damage response. E2F1- and E7-mediated apoptosis are compromised in cells from patients with the related disorders ataxia telangiectasia and Nijmegen breakage syndrome lacking functional Atm and Nbs1 gene products, respectively. Both Atm and Nbs1 contribute to Chk2 activation and p53 phosphorylation following deregulation of normal Rb growth control. E2F2, a related E2F family member that does not induce apoptosis, also activates Atm, resulting in phosphorylation of p53. However, we found that the key commitment step in apoptosis induction is the ability of E2F1, and not E2F2, to upregulate Chk2 expression. Our results suggest that E2F1 plays a central role in signaling disturbances in the Rb growth control pathway and, by upregulation of Chk2, may sensitize cells to undergo apoptosis.
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Affiliation(s)
- Harry A Rogoff
- Program in Immunology and Virology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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23
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Powers JT, Hong S, Mayhew CN, Rogers PM, Knudsen ES, Johnson DG. E2F1 Uses the ATM Signaling Pathway to Induce p53 and Chk2 Phosphorylation and Apoptosis. Mol Cancer Res 2004. [DOI: 10.1158/1541-7786.203.2.4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
The p53 tumor suppressor protein is phosphorylated and activated by several DNA damage-inducible kinases, such as ATM, and is a key effector of the DNA damage response by promoting cell cycle arrest or apoptosis. Deregulation of the Rb-E2F1 pathway also results in the activation of p53 and the promotion of apoptosis, and this contributes to the suppression of tumor development. Here, we describe a novel connection between E2F1 and the ATM DNA damage response pathway. In primary human fibroblasts lacking functional ATM, the ability of E2F1 to induce the phosphorylation of p53 and apoptosis is impaired. In contrast, ATM status has no effect on transcriptional activation of target genes or the stimulation of DNA synthesis by E2F1. Cells containing mutant Nijmegen breakage syndrome protein (NBS1), a component of the Mre11-Rad50 DNA repair complex, also have attenuated p53 phosphorylation and apoptosis in response to E2F1 expression. Moreover, E2F1 induces ATM- and NBS1-dependent phosphorylation of the checkpoint kinase Chk2 at Thr68, a phosphorylation site that stimulates Chk2 activity. Delayed γH2AX phosphorylation and absence of ATM autophosphorylation at Ser1981 suggest that E2F1 stimulates ATM through a unique mechanism that is distinct from agents that cause DNA double-strand breaks. These findings identify new roles for several DNA damage response factors by demonstrating that they also participate in the oncogenic stress signaling pathway between E2F1 and p53.
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Affiliation(s)
- John T. Powers
- 1Department of Carcinogenesis, University of Texas MD Anderson Cancer Center, Science Park-Research Division, Smithville, Texas
- 2Section of Molecular Genetics and Microbiology, University of Texas at Austin, Austin, Texas; and
| | - SungKi Hong
- 1Department of Carcinogenesis, University of Texas MD Anderson Cancer Center, Science Park-Research Division, Smithville, Texas
| | - Christopher N. Mayhew
- 3Department of Cell Biology, College of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Pamela M. Rogers
- 1Department of Carcinogenesis, University of Texas MD Anderson Cancer Center, Science Park-Research Division, Smithville, Texas
| | - Erik S. Knudsen
- 3Department of Cell Biology, College of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - David G. Johnson
- 1Department of Carcinogenesis, University of Texas MD Anderson Cancer Center, Science Park-Research Division, Smithville, Texas
- 2Section of Molecular Genetics and Microbiology, University of Texas at Austin, Austin, Texas; and
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24
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Jack MT, Woo RA, Hirao A, Cheung A, Mak TW, Lee PWK. Chk2 is dispensable for p53-mediated G1 arrest but is required for a latent p53-mediated apoptotic response. Proc Natl Acad Sci U S A 2002; 99:9825-9. [PMID: 12097646 PMCID: PMC125030 DOI: 10.1073/pnas.152053599] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
In response to genotoxic stress, mammalian cells can activate cell cycle checkpoint pathways to arrest the cell for repair of DNA damage or induce apoptosis to eliminate damaged cells. The checkpoint kinase, Chk2, has been implicated in both of these responses and is believed to function in an ataxia telangiectasia (Atm)-dependent manner. We show here that Chk2-/- mouse embryo fibroblasts (MEFs), unlike Atm-/- or p53-/- MEFs, behaved like normal MEFs in manifesting p21 induction and G(1) arrest upon exposure to gamma-irradiation. Therefore, Chk2 is not involved in p53-mediated G(1) arrest. To examine the role of Chk2 in p53-dependent apoptotic response, we used adenovirus E1A-expressing MEFs. We show that Chk2-/- cells, like p53-/- cells, did not undergo DNA damage-induced apoptosis, whereas Atm-/- cells behaved like normal cells in invoking an apoptotic response. Furthermore, this apoptosis could occur in the absence of protein synthesis, suggesting that it is preexisting, or "latent," p53 that mediates this response. We conclude that Chk2 is not involved in Atm- and p53-dependent G(1) arrest, but is involved in the activation of latent p53, independently of Atm, in triggering DNA damage-induced apoptosis.
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Affiliation(s)
- Melissa T Jack
- Cancer Biology Research Group and Department of Microbiology and Infectious Diseases, University of Calgary Health Sciences Center, Calgary, AL, Canada T2N 4N1
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25
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Woo RA, Jack MT, Xu Y, Burma S, Chen DJ, Lee PW. DNA damage-induced apoptosis requires the DNA-dependent protein kinase, and is mediated by the latent population of p53. EMBO J 2002; 21:3000-8. [PMID: 12065413 PMCID: PMC126062 DOI: 10.1093/emboj/cdf307] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Mouse embryo fibroblasts (MEFs) expressing the adenovirus E1A protein undergo apoptosis upon exposure to ionizing radiation. We show here that immediately following gamma-irradiation, latent p53 formed a complex with the catalytic subunit of the DNA-dependent protein kinase (DNA-PK(CS)). The complex formation was DNase sensitive, suggesting that the proteins came together on the DNA, conceivably at strand breaks. This association was accompanied by phosphorylation of pre-existing, latent p53 at Ser18 (corresponding to Ser15 in human p53), which was not found in DNA-PK(CS)(-/-) cells. Most significantly, DNA damage-induced apoptosis was abolished in both DNA-PK(CS)(-/-) and p53(-/-) cells. In addition, blocking synthesis of inducible p53 by cycloheximide did not abrogate apoptosis, suggesting that the latent population of p53 is sufficient for executing the apoptotic program. Finally, E1A-expressing MEFs from a p53 "knock-in" mouse where Ser18 was mutated to an alanine had an attenuated apoptotic response, indicating that phosphorylation of this site by DNA-PK is a contributing factor for apoptosis.
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Affiliation(s)
| | | | - Yang Xu
- Cancer Biology Research Group and Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada T2N 4N1,
Division of Biology and Cancer Center, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322 and Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Corresponding author e-mail:
| | - Sandeep Burma
- Cancer Biology Research Group and Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada T2N 4N1,
Division of Biology and Cancer Center, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322 and Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Corresponding author e-mail:
| | - David J. Chen
- Cancer Biology Research Group and Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada T2N 4N1,
Division of Biology and Cancer Center, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322 and Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Corresponding author e-mail:
| | - Patrick W.K. Lee
- Cancer Biology Research Group and Department of Microbiology and Infectious Diseases, University of Calgary, Calgary, Alberta, Canada T2N 4N1,
Division of Biology and Cancer Center, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0322 and Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA Corresponding author e-mail:
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26
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Petiniot LK, Weaver Z, Vacchio M, Shen R, Wangsa D, Barlow C, Eckhaus M, Steinberg SM, Wynshaw-Boris A, Ried T, Hodes RJ. RAG-mediated V(D)J recombination is not essential for tumorigenesis in Atm-deficient mice. Mol Cell Biol 2002; 22:3174-7. [PMID: 11940674 PMCID: PMC133758 DOI: 10.1128/mcb.22.9.3174-3177.2002] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Atm-deficient mice die of malignant thymic lymphomas characterized by translocations within the Tcr alpha/delta locus, suggesting that tumorigenesis is secondary to aberrant responses to double-stranded DNA (dsDNA) breaks that occur during RAG-dependent V(D)J recombination. We recently demonstrated that development of thymic lymphoma in Atm(-/-) mice was not prevented by loss of RAG-2. Thymic lymphomas that developed in Rag2(-/-) Atm(-/-) mice contained multiple chromosomal abnormalities, but none of these involved the Tcr alpha/delta locus. These findings indicated that tumorigenesis in Atm(-/-) mice is mediated by chromosomal translocations secondary to aberrant responses to dsDNA breaks and that V(D)J recombination is an important, but not essential, event in susceptibility. In contrast to these findings, it was recently reported that Rag1(-/-) Atm(-/-) mice do not develop thymic lymphomas, a finding that was interpreted as demonstrating a requirement for RAG-dependent recombination in the susceptibility to tumors in Atm-deficient mice. To test the possibility that RAG-1 and RAG-2 differ in their roles in tumorigenesis, we studied Rag1(-/-) Atm(-/-) mice in parallel to our previous Rag2(-/-) Atm(-/-) study. We found that thymic lymphomas occur at high frequency in Rag1(-/-) Atm(-/-) mice and resemble those that occur in Rag2(-/-) Atm(-/-) mice. These results indicate that both RAG-1 and RAG-2 are necessary for tumorigenesis involving translocation in the Tcr alpha/delta locus but that Atm deficiency leads to tumors through a broader RAG-independent predisposition to translocation, related to a generalized defect in dsDNA break repair.
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Affiliation(s)
- Lisa K Petiniot
- Experimental Immunology Branch, National Cancer Institute, Howard Hughes Medical Institute-NIH Research Scholars Program, National Institutes of Health, Bethesda, Maryland 20892, USA
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27
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Abstract
One of the cornerstones of the web of signaling pathways governing cellular life and differentiation is the DNA damage response. It spans a complex network of pathways, ranging from DNA repair to modulation of numerous processes in the cell. DNA double-strand breaks (DSBs), which are formed as a result of genotoxic stress or normal recombinational processes, are extremely lethal lesions that rapidly mobilize this intricate defense system. The master controller that pilots cellular responses to DSBs is the ATM protein kinase, which turns on this network by phosphorylating key players in its various branches. ATM is the protein product of the gene mutated in the human genetic disorder ataxia-telangiectasia (A-T), which is characterized by neuronal degeneration, immunodeficiency, sterility, genomic instability, cancer predisposition, and radiation sensitivity. The clinical and cellular phenotype of A-T attests to the numerous roles of ATM, on the one hand, and to the link between the DNA damage response and developmental processes on the other hand. Recent studies of this protein and its effectors, combined with a thorough investigation of animal models of A-T, have led to new insights into the mode of action of this master controller of the DNA damage response. The evidence that ATM is involved in signaling pathways other than those related to damage response, particularly ones relating to cellular growth and differentiation, reinforces the multifaceted nature of this protein, in which genome stability, developmental processes, and cancer cross paths.
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Affiliation(s)
- Y Shiloh
- Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Israel
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28
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Abstract
Genetically engineered mouse models have contributed extensively to the field of cancer research. The ability to manipulate the mouse germline affords numerous approaches toward understanding the complexities of this disease, possibly providing accurate preclinical models for therapeutic and diagnostic advances. This review highlights some of the current strategies for modeling cancer in the mouse, recent accomplishments, and key remaining challenges.
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Affiliation(s)
- Terry Van Dyke
- Department of Biochemistry and Biophysics, Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
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29
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Bhandoola A, Dolnick B, Fayad N, Nussenzweig A, Singer A. Immature thymocytes undergoing receptor rearrangements are resistant to an Atm-dependent death pathway activated in mature T cells by double-stranded DNA breaks. J Exp Med 2000; 192:891-7. [PMID: 10993919 PMCID: PMC2193292 DOI: 10.1084/jem.192.6.891] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Immature CD4(+)CD8(+) thymocytes rearrange their T cell receptor (TCR)-alpha gene locus to generate clonotypic alpha/beta TCR, after which a few cells expressing selectable TCR are signaled to further differentiate into mature T cells. Because of requirements for self-tolerance, immature CD4(+)CD8(+) thymocytes are programmed to die in the thymus in response to a variety of stimuli that do not induce death of mature T cells. We now demonstrate that, in contrast to all previously described stimuli, immature CD4(+)CD8(+) thymocytes are selectively more resistant than mature T cells to apoptotic death induced by DNA intercalating agents. Importantly, we demonstrate that DNA intercalating agents induce double-stranded DNA breaks in both immature thymocytes and mature T cells, but immature thymocytes tolerate these DNA breaks, whereas mature T cells are signaled to die by an Atm-dependent but p53-independent death mechanism. Thus, our results indicate that absence of an Atm-dependent but p53-independent pathway allows immature thymocytes to survive double-stranded DNA breaks. It is likely that the unique ability of immature thymocytes to survive DNA-damaging intercalating agents reflects their tolerance of double-stranded DNA breaks that occur normally during antigen receptor gene rearrangements.
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Affiliation(s)
- A Bhandoola
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
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30
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Petiniot LK, Weaver Z, Barlow C, Shen R, Eckhaus M, Steinberg SM, Ried T, Wynshaw-Boris A, Hodes RJ. Recombinase-activating gene (RAG) 2-mediated V(D)J recombination is not essential for tumorigenesis in Atm-deficient mice. Proc Natl Acad Sci U S A 2000; 97:6664-9. [PMID: 10841564 PMCID: PMC18695 DOI: 10.1073/pnas.97.12.6664] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The majority of Atm-deficient mice die of malignant thymic lymphoma by 4-5 mo of age. Cytogenetic abnormalities in these tumors are consistently identified within the Tcr alpha/delta locus, suggesting that tumorigenesis is secondary to aberrant responses to double-stranded DNA breaks that occur during V(D)J recombination. Since V(D)J recombination is a recombinase-activating gene (RAG)-dependent process, we generated Rag2(-/-)Atm(-/-) mice to assess the requirement for RAG-dependent recombination in thymic lymphomagenesis. In contrast to expectation, the data presented here indicate that development of malignant thymic lymphoma in Atm(-/-) mice is not prevented by loss of RAG-2 and thus is not dependent on V(D)J recombination. Malignant thymic lymphomas in Rag2(-/-)Atm(-/-) mice occurred at a lower frequency and with a longer latency as compared with Atm(-/-) mice. Importantly, cytogenetic analysis of these tumors indicated that multiple chromosomal abnormalities occurred in each tumor, but that none of these involved the Tcr alpha/delta locus. Nonmalignant peripheral T cells from TCR-transgenic Rag2(-/-)Atm(-/-) mice also revealed a substantial increase in translocation frequency, suggesting that these translocations are early events in the process of tumorigenesis. These data are consistent with the hypothesis that the major mechanism of tumorigenesis in Atm(-/-) mice is via chromosomal translocations and other abnormalities that are secondary to aberrant responses to double-stranded DNA breaks. Furthermore, these data suggest that V(D)J recombination is a critical, but not essential, event during which Atm-deficient thymocytes are susceptible to developing chromosome aberrations that predispose to malignant transformation.
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Affiliation(s)
- L K Petiniot
- Experimental Immunology Branch, Genetics Department, Biostatistics and Data Management Section, Office of the Director of the Division of Clinical Sciences, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
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Ollmann M, Young LM, Di Como CJ, Karim F, Belvin M, Robertson S, Whittaker K, Demsky M, Fisher WW, Buchman A, Duyk G, Friedman L, Prives C, Kopczynski C. Drosophila p53 is a structural and functional homolog of the tumor suppressor p53. Cell 2000; 101:91-101. [PMID: 10778859 DOI: 10.1016/s0092-8674(00)80626-1] [Citation(s) in RCA: 322] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The importance of p53 in carcinogenesis stems from its central role in inducing cell cycle arrest or apoptosis in response to cellular stresses. We have identified a Drosophila homolog of p53 ("Dmp53"). Like mammalian p53, Dmp53 binds specifically to human p53 binding sites, and overexpression of Dmp53 induces apoptosis. Importantly, inhibition of Dmp53 function renders cells resistant to X ray-induced apoptosis, suggesting that Dmp53 is required for the apoptotic response to DNA damage. Unlike mammalian p53, Dmp53 appears unable to induce a G1 cell cycle block when overexpressed, and inhibition of Dmp53 activity does not affect X ray-induced cell cycle arrest. These data reveal an ancestral proapoptotic function for p53 and identify Drosophila as an ideal model system for elucidating the p53 apoptotic pathway(s) induced by DNA damage.
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Affiliation(s)
- M Ollmann
- Exelixis, Inc., South San Francisco, California 94080, USA
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Wang S, Guo M, Ouyang H, Li X, Cordon-Cardo C, Kurimasa A, Chen DJ, Fuks Z, Ling CC, Li GC. The catalytic subunit of DNA-dependent protein kinase selectively regulates p53-dependent apoptosis but not cell-cycle arrest. Proc Natl Acad Sci U S A 2000; 97:1584-8. [PMID: 10677503 PMCID: PMC26478 DOI: 10.1073/pnas.97.4.1584] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
DNA damage induced by ionizing radiation (IR) activates p53, leading to the regulation of downstream pathways that control cell-cycle progression and apoptosis. However, the mechanisms for the IR-induced p53 activation and the differential activation of pathways downstream of p53 are unclear. Here we provide evidence that the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) serves as an upstream effector for p53 activation in response to IR, linking DNA damage to apoptosis. DNA-PKcs knockout (DNA-PKcs-/-) mice were exposed to whole-body IR, and the cell-cycle and apoptotic responses were examined in their thymuses. Our data show that IR induction of apoptosis and Bax expression, both mediated via p53, was significantly suppressed in the thymocytes of DNA-PKcs-/- mice. In contrast, IR-induced cell-cycle arrest and p21 expression were normal. Thus, DNA-PKcs deficiency selectively disrupts p53-dependent apoptosis but not cell-cycle arrest. We also confirmed previous findings that p21 induction was attenuated and cell-cycle arrest was defective in the thymoctyes of whole body-irradiated Atm-/- mice, but the apoptotic response was unperturbed. Taken together, our results support a model in which the upstream effectors DNA-PKcs and Atm selectively activate p53 to differentially regulate cell-cycle and apoptotic responses. Whereas Atm selects for cell-cycle arrest but not apoptosis, DNA-PKcs selects for apoptosis but not cell-cycle arrest.
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Affiliation(s)
- S Wang
- Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021; and Los Alamos National Laboratory, Los Alamos, NM 87545, USA
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Abstract
Cell proliferation and cell death are essential yet opposing cellular processes. Crosstalk between these processes promotes a balance between proliferation and death, and it limits the growth and survival of cells with oncogenic mutations. New insights into the mechanisms by which strong signals to proliferate and activation of cyclin-dependent kinases promote apoptosis have recently been published, and a novel cell cycle regulated caspase inhibitor, Survivin, has been described.
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Affiliation(s)
- M Guo
- Department of Neurology, University of California in Los Angeles (UCLA) Medical Center, C-128 RNRC, Los Angeles, CA 90095, USA.
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