1
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Parisi A, Struelens L, Vanhavere F. Comparison between the results of a recently-developed biological weighting function (V79-RBE 10BWF) and the in vitroclonogenic survival RBE 10of other repair-competent asynchronized normoxic mammalian cell lines and ions not used for the development of the model. Phys Med Biol 2021; 66. [PMID: 34710862 DOI: 10.1088/1361-6560/ac344e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 10/28/2021] [Indexed: 11/11/2022]
Abstract
728 simulated microdosimetric lineal energy spectra (26 different ions between 1H and 238U, 28 energy points from 1 to 1000 MeV/n) were used in combination with a recently-developed biological weighting function (Parisi et al., 2020) and 571 published in vitro clonogenic survival curves in order to: 1) assess prediction intervals for the in silico results by deriving an empirical indication of the experimental uncertainty from the dispersion in the in vitro hamster lung fibroblast (V79) data used for the development of the biophysical model; 2) explore the possibility of modeling the relative biological effectiveness (RBE) of the 10% clonogenic survival of asynchronized normoxic repair-competent mammalian cell lines other than the one used for the development of the model (V79); 3) investigate the predictive power of the model through a comparison between in silico results and in vitro data for 10 ions not used for the development of the model. At first, different strategies for the assessment of the in silico prediction intervals were compared. The possible sources of uncertainty responsible for the dispersion in the in vitro data were also shortly reviewed. Secondly, also because of the relevant scatter in the in vitro data, no statistically-relevant differences were found between the RBE10 of the investigated different asynchronized normoxic repair-competent mammalian cell lines. The only exception (Chinese Hamster peritoneal fibroblasts, B14FAF28), is likely due to the limited dataset (all in vitro ion data were extracted from a single publication), systematic differences in the linear energy transfer (LET) calculations for the employed very-heavy ions, and the use of reference photon survival curves extracted from a different publication. Finally, the in silico predictions for the 10 ions not used for the model development were in good agreement with the corresponding in vitro data.
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Affiliation(s)
- Alessio Parisi
- Radiation Protection Dosimetry and Calibration, Studiecentrum voor Kernenergie, Boeretang 200, Mol, Belgiun, Mol, 2400, BELGIUM
| | - Lara Struelens
- Radiation Protection, Dosimetry and Calibration, Belgian Nuclear Research Centre SCK.CEN, Boeretang 200, Mol, 2400, BELGIUM
| | - Filip Vanhavere
- Institute of Advanced Nuclear Systems, Belgian Nuclear Research Centre SCK.CEN, Boeretang 200, B-2400 Mol, Mol, BELGIUM
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2
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Multi-scaled Monte Carlo calculation for radon-induced cellular damage in the bronchial airway epithelium. Sci Rep 2021; 11:10230. [PMID: 33986410 PMCID: PMC8119983 DOI: 10.1038/s41598-021-89689-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Accepted: 04/21/2021] [Indexed: 12/19/2022] Open
Abstract
Radon is a leading cause of lung cancer in indoor public and mining workers. Inhaled radon progeny releases alpha particles, which can damage cells in the airway epithelium. The extent and complexity of cellular damage vary depending on the alpha particle’s kinetic energy and cell characteristics. We developed a framework to quantitate the cellular damage on the nanometer and micrometer scales at different intensities of exposure to radon progenies Po-218 and Po-214. Energy depositions along the tracks of alpha particles that were slowing down were simulated on a nanometer scale using the Monte Carlo code Geant4-DNA. The nano-scaled track histories in a 5 μm radius and 1 μm-thick cylindrical volume were integrated into the tracking scheme of alpha trajectories in a micron-scale bronchial epithelium segment in the user-written SNU-CDS program. Damage distribution in cellular DNA was estimated for six cell types in the epithelium. Deep-sited cell nuclei in the epithelium would have less chance of being hit, but DNA damage from a single hit would be more serious, because low-energy alpha particles of high LET would hit the nuclei. The greater damage in deep-sited nuclei was due to the 7.69 MeV alpha particles emitted from Po-214. From daily work under 1 WL of radon concentration, basal cells would respond with the highest portion of complex DSBs among the suspected progenitor cells in the most exposed regions of the lung epithelium.
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3
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Chatzipapas KP, Papadimitroulas P, Loudos G, Papanikolaou N, Kagadis GC. IDDRRA: A novel platform, based on Geant4-DNA to quantify DNA damage by ionizing radiation. Med Phys 2021; 48:2624-2636. [PMID: 33657650 DOI: 10.1002/mp.14817] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 02/22/2021] [Accepted: 02/23/2021] [Indexed: 01/23/2023] Open
Abstract
PURPOSE This study proposes a novel computational platform that we refer to as IDDRRA (DNA Damage Response to Ionizing RAdiation), which uses Monte Carlo (MC) simulations to score radiation induced DNA damage. MC simulations provide results of high accuracy on the interaction of radiation with matter while scoring the energy deposition based on state-of-the-art physics and chemistry models and probabilistic methods. METHODS The IDDRRA software is based on the Geant4-DNA toolkit together with new tools that were developed for the purpose of this study, including a new algorithm that was developed in Python for the design of the DNA molecules. New classes were developed in C++ to integrate the GUI and produce the simulation's output in text format. An algorithm was also developed to analyze the simulation's output in terms of energy deposition, Single Strand Breaks (SSB), Double Strand Breaks (DSB) and Cluster Damage Sites (CDS). Finally, a new tool was developed to implement probabilistic SSB and DSB repair models using MC techniques. RESULTS This article provides the first benchmarks that the user of the IDDRRA tool can use to validate the functionality of the software as well as to provide a starting point to produce different types of DNA simulations. These benchmarks incorporate different kind of particles (e-, e+, protons, electron spectrum) and DNA molecules. CONCLUSION We have developed the IDDRRA tool and demonstrated its use to study various aspects of the modeling and simulation of a DNA irradiation experiment. The tool is expandable and can be expanded by other users with new benchmarks and applications based on the user's needs and experience. New functionality will be added over time, including the quantification of the indirect damage.
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Affiliation(s)
- Konstantinos P Chatzipapas
- 3dmi Research Group, Department of Medical Physics, School of Medicine, University of Patras, Rion, 26504, Greece
| | | | - George Loudos
- Bioemission Technology Solutions (BIOEMTECH), Athens, 11472, Greece
| | - Niko Papanikolaou
- Health Science Center, University of Texas, San Antonio, TX, 78229, USA
| | - George C Kagadis
- 3dmi Research Group, Department of Medical Physics, School of Medicine, University of Patras, Rion, 26504, Greece
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4
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Matsuya Y, Kai T, Sato T, Liamsuwan T, Sasaki K, Nikjoo H. Verification of KURBUC-based ion track structure mode for proton and carbon ions in the PHITS code. Phys Med Biol 2021; 66:06NT02. [PMID: 33588391 DOI: 10.1088/1361-6560/abe65e] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The particle and heavy ion transport code system (PHITS) is a general-purpose Monte Carlo radiation transport simulation code. It has the ability to handle diverse particle types over a wide range of energy. The latest PHITS development enables the generation of track structure for proton and carbon ions (1H+, 12C6+) based on the algorithms in the KURBUC code, which is considered as one of the most verified track-structure codes worldwide. This ion track-structure mode is referred to as the PHITS-KURBUC mode. In this study, the range, radial dose distributions, and microdosimetric distributions were calculated using the PHITS-KURBUC mode. Subsequently, they were compared with the corresponding data obtained from the original KURBUC and from other studies. These comparative studies confirm the successful inclusion of the KURBUC code in the PHITS code. As results of the synergistic effect between the macroscopic and microscopic radiation transport codes, this implementation enabled the detailed calculation of the microdosimetric and nanodosimetric quantities under complex radiation fields, such as proton beam therapy with the spread-out Bragg peak.
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Affiliation(s)
- Yusuke Matsuya
- Nuclear Science and Engineering Center, Research Group for Radiation Transport Analysis, Japan Atomic Energy Agency (JAEA), 2-4 Shirakata, Tokai, Ibaraki, 319-1195, Japan
| | - Takeshi Kai
- Nuclear Science and Engineering Center, Research Group for Radiation Transport Analysis, Japan Atomic Energy Agency (JAEA), 2-4 Shirakata, Tokai, Ibaraki, 319-1195, Japan
| | - Tatsuhiko Sato
- Nuclear Science and Engineering Center, Research Group for Radiation Transport Analysis, Japan Atomic Energy Agency (JAEA), 2-4 Shirakata, Tokai, Ibaraki, 319-1195, Japan
| | - Thiansin Liamsuwan
- Faculty of Medicine and Public Health, HRH Princess Chulabhorn College of Medical Science, Chulabhorn Royal Academy, Bangkok 10210, Thailand
| | - Kohei Sasaki
- Department of Radiological Technology, Faculty of Health Sciences, Hokkaido University of Science, Maeda 7-15, Teine-ku, Sapporo 006-8585, Japan
| | - Hooshang Nikjoo
- Radiation Biophysics Group, Department of Oncology-Pathology, Karolinska Institutet, SE-17176 Stockholm, Sweden
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5
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Shuryak I, Brenner DJ. Quantitative modeling of multigenerational effects of chronic ionizing radiation using targeted and nontargeted effects. Sci Rep 2021; 11:4776. [PMID: 33637848 PMCID: PMC7910614 DOI: 10.1038/s41598-021-84156-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 02/12/2021] [Indexed: 12/22/2022] Open
Abstract
Stress response signals can propagate between cells damaged by targeted effects (TE) of ionizing radiation (e.g. energy depositions and ionizations in the nucleus) and undamaged "bystander" cells, sometimes over long distances. Their consequences, called non-targeted effects (NTE), can substantially contribute to radiation-induced damage (e.g. cell death, genomic instability, carcinogenesis), particularly at low doses/dose rates (e.g. space exploration, some occupational and accidental exposures). In addition to controlled laboratory experiments, analysis of observational data on wild animal and plant populations from areas contaminated by radionuclides can enhance our understanding of radiation responses because such data span wide ranges of dose rates applied over many generations. Here we used a mechanistically-motivated mathematical model of TE and NTE to analyze published embryonic mortality data for plants (Arabidopsis thaliana) and rodents (Clethrionomys glareolus) from the Chernobyl nuclear power plant accident region. Although these species differed strongly in intrinsic radiosensitivities and post-accident radiation exposure magnitudes, model-based analysis suggested that NTE rather than TE dominated the responses of both organisms to protracted low-dose-rate irradiation. TE were predicted to become dominant only above the highest dose rates in the data. These results support the concept of NTE involvement in radiation-induced health risks from chronic radiation exposures.
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Affiliation(s)
- Igor Shuryak
- Center for Radiological Research, Columbia University Irving Medical Center, 630 West 168th Street, VC-11-234/5, New York, NY, 10032, USA.
| | - David J Brenner
- Center for Radiological Research, Columbia University Irving Medical Center, 630 West 168th Street, VC-11-234/5, New York, NY, 10032, USA
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6
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Zhu H, McNamara AL, McMahon SJ, Ramos-Mendez J, Henthorn NT, Faddegon B, Held KD, Perl J, Li J, Paganetti H, Schuemann J. Cellular Response to Proton Irradiation: A Simulation Study with TOPAS-nBio. Radiat Res 2020; 194:9-21. [PMID: 32401689 DOI: 10.1667/rr15531.1] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Accepted: 04/11/2020] [Indexed: 12/21/2022]
Abstract
The cellular response to ionizing radiation continues to be of significant research interest in cancer radiotherapy, and DNA is recognized as the critical target for most of the biologic effects of radiation. Incident particles can cause initial DNA damages through physical and chemical interactions within a short time scale. Initial DNA damages can undergo repair via different pathways available at different stages of the cell cycle. The misrepair of DNA damage results in genomic rearrangement and causes mutations and chromosome aberrations, which are drivers of cell death. This work presents an integrated study of simulating cell response after proton irradiation with energies of 0.5-500 MeV (LET of 60-0.2 keV/µm). A model of a whole nucleus with fractal DNA geometry was implemented in TOPAS-nBio for initial DNA damage simulations. The default physics and chemistry models in TOPAS-nBio were used to describe interactions of primary particles, secondary particles, and radiolysis products within the nucleus. The initial DNA double-strand break (DSB) yield was found to increase from 6.5 DSB/Gy/Gbp at low-linear energy transfer (LET) of 0.2 keV/µm to 21.2 DSB/Gy/Gbp at high LET of 60 keV/µm. A mechanistic repair model was applied to predict the characteristics of DNA damage repair and dose response of chromosome aberrations. It was found that more than 95% of the DSBs are repaired within the first 24 h and the misrepaired DSB fraction increases rapidly with LET and reaches 15.8% at 60 keV/µm with an estimated chromosome aberration detection threshold of 3 Mbp. The dicentric and acentric fragment yields and the dose response of micronuclei formation after proton irradiation were calculated and compared with experimental results.
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Affiliation(s)
- Hongyu Zhu
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts 02114.,Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R. China.,Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing 100084, P.R. China
| | - Aimee L McNamara
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts 02114.,Harvard Medical School, Boston, Massachusetts 02114
| | - Stephen J McMahon
- Centre for Cancer Research and Cell Biology, Queens University Belfast, Belfast, United Kingdom
| | - Jose Ramos-Mendez
- Department of Radiation Oncology, University of California San Francisco, California 94143
| | - Nicholas T Henthorn
- Division of Molecular and Clinical Cancer Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Bruce Faddegon
- Department of Radiation Oncology, University of California San Francisco, California 94143
| | - Kathryn D Held
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts 02114.,Harvard Medical School, Boston, Massachusetts 02114
| | - Joseph Perl
- SLAC National Accelerator Laboratory, Menlo Park, California
| | - Junli Li
- Department of Engineering Physics, Tsinghua University, Beijing 100084, P.R. China.,Key Laboratory of Particle & Radiation Imaging (Tsinghua University), Ministry of Education, Beijing 100084, P.R. China
| | - Harald Paganetti
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts 02114.,Harvard Medical School, Boston, Massachusetts 02114
| | - Jan Schuemann
- Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts 02114.,Harvard Medical School, Boston, Massachusetts 02114
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7
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Hill MA. Radiation Track Structure: How the Spatial Distribution of Energy Deposition Drives Biological Response. Clin Oncol (R Coll Radiol) 2020; 32:75-83. [PMID: 31511190 DOI: 10.1016/j.clon.2019.08.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/04/2019] [Accepted: 07/08/2019] [Indexed: 12/22/2022]
Abstract
Ionising radiation is incredibly effective at causing biological effects. This is due to the unique way energy is deposited along highly structured tracks of ionisation and excitation events, which results in correlation with sites of DNA damage from the nanometre to the micrometre scale. Correlation of these events along the track on the nanometre scale results in clustered damage, which not only results in the formation of DNA double-strand breaks (DSB), but also more difficult to repair complex DSB, which include additional damage within a few base pairs. The track structure varies significantly with radiation quality and the increase in relative biological effectiveness observed with increasing linear energy transfer in part corresponds to an increase in the probability and complexity of clustered DNA damage produced. Likewise, correlation over larger scales, associated with packing of DNA and associated chromosomes within the cell nucleus, can also have a major impact on the biological response. The proximity of the correlated damage along the track increases the probability of miss-repair through pairwise interactions resulting in an increase in probability and complexity of DNA fragments/deletions, mutations and chromosomal rearrangements. Understanding the mechanisms underlying the biological effectiveness of ionising radiation can provide an important insight into ways of increasing the efficacy of radiotherapy, as well as the risks associated with exposure. This requires a multi-scale approach for modelling, not only considering the physics of the track structure from the millimetre scale down to the nanometre scale, but also the structural packing of the DNA within the nucleus, the resulting chemistry in the context of the highly reactive environment of the nucleus, together with the subsequent biological response.
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Affiliation(s)
- M A Hill
- MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, Oxford, UK.
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8
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Zhu LS, Wang DQ, Cui K, Liu D, Zhu LQ. Emerging Perspectives on DNA Double-strand Breaks in Neurodegenerative Diseases. Curr Neuropharmacol 2019; 17:1146-1157. [PMID: 31362659 PMCID: PMC7057204 DOI: 10.2174/1570159x17666190726115623] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 06/03/2019] [Accepted: 07/01/2019] [Indexed: 11/22/2022] Open
Abstract
DNA double-strand breaks (DSBs) are common events that were recognized as one of the most toxic lesions in eu-karyotic cells. DSBs are widely involved in many physiological processes such as V(D)J recombination, meiotic recombina-tion, DNA replication and transcription. Deregulation of DSBs has been reported in multiple diseases in human beings, such as the neurodegenerative diseases, with which the underlying mechanisms are needed to be illustrated. Here, we reviewed the recent insights into the dysfunction of DSB formation and repair, contributing to the pathogenesis of neurodegenerative dis-orders including Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), Huntington’s disease (HD) and ataxia tel-angiectasia (A-T).
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Affiliation(s)
- Ling-Shuang Zhu
- Department of Neurosurgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, China.,Department of Pathophysiology, Key Lab of Neurological Disorder of Education, Ministry, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Ding-Qi Wang
- Department of Neurosurgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, China.,Department of Pathophysiology, Key Lab of Neurological Disorder of Education, Ministry, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Ke Cui
- Department of Neurosurgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, China.,Department of Pathophysiology, Key Lab of Neurological Disorder of Education, Ministry, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Dan Liu
- Department of Pathophysiology, Key Lab of Neurological Disorder of Education, Ministry, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.,Department of Medical Genetics, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Ling-Qiang Zhu
- Department of Neurosurgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430022, China.,Department of Pathophysiology, Key Lab of Neurological Disorder of Education, Ministry, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
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9
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Shuryak I. Enhancing low-dose risk assessment using mechanistic mathematical models of radiation effects. JOURNAL OF RADIOLOGICAL PROTECTION : OFFICIAL JOURNAL OF THE SOCIETY FOR RADIOLOGICAL PROTECTION 2019; 39:S1-S13. [PMID: 31292290 DOI: 10.1088/1361-6498/ab3101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Mechanistic mathematical modeling of ionizing radiation (IR) effects has a long history spanning several decades. Models that mathematically represent current knowledge and hypotheses about how radiation damages cells and organs, leading to deleterious outcomes such as carcinogenesis, are particularly useful for estimating radiation risks at doses that are relevant for radiation protection, but are too low to provide a strong 'signal-to-noise ratio' in epidemiological or experimental studies with realistic sample sizes. Here, I discuss examples of models in several relevant areas, including radionuclide biokinetics, non-targeted IR effects, DNA double-strand break (DSB) rejoining and radiation carcinogenesis. I do not provide a detailed review of the vast modeling literature in these fields, but focus on concepts that we have implemented, such as using continuous probability distributions of exponential rates to model radionuclide biokinetics and DSB rejoining, and combining short and long time scales in carcinogenesis models. Improvements in models, including the ability to generate new hypotheses based on model predictions, may come from the introduction of additional novel concepts and from integrating multiple data types.
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Affiliation(s)
- Igor Shuryak
- Center for Radiological Research, Columbia University, New York, NY, United States of America
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10
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Taleei R. MODELLING DSB REPAIR KINETICS FOR DNA DAMAGE INDUCED BY PROTON AND CARBON IONS. RADIATION PROTECTION DOSIMETRY 2019; 183:75-78. [PMID: 30668809 DOI: 10.1093/rpd/ncy304] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Accepted: 12/26/2018] [Indexed: 06/09/2023]
Abstract
Proton and carbon therapy are the main choices of particle therapy for cancer treatment. Particle dose distribution is superior to conventional photon therapy dose distribution due to Bragg peak. However, the basic biology of cellular damage and cell death is not well understood. The aim of this work is to present a mechanistic model of double strand break (DSB) repair that predicts the repair kinetics of damage induced by particles employed in cancer therapy. Monte Carlo Track Damage Simulation (MCDS) was employed to model DNA damage. The frequency of DSB and SSB was computed for proton and carbon ions. DSBs were subjected to repair model to calculate the repair kinetics. Two distinct DSB repair models dependent on the cell cycle were proposed. The DSB repair model contains non-homologous end joining (NHEJ), homologous recombination (HR) and back up non-homologous end joining (B-NHEJ) repair processes. The DSB complexity results in the switch in the repair pathway from NHEJ to a slower process that starts with DSB end resection. DSB end resection in early S and G1 phases of the cell cycle enhances the B-NHEJ repair pathway, while in late S and G2 phases of the cell cycle promotes HR repair pathway. The repair model was transformed to a set of nonlinear differential equations. The model calculates the overall repair kinetics and protein temporal repair activity at the site of damage. The damage and repair model provides a detailed mechanistic understanding of all processes that are involved in the damage induction and repair. The number of DSB and their complexity increase as the particle energy decreases due to the proximity of particle interactions in water. The repair kinetics show a biphasic behaviour that is due to the NHEJ fast repair of simple type DSB and HR slow repair of complex type DSB.
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Affiliation(s)
- Reza Taleei
- Division of Medical Physics, Department of Radiation Oncology, University of Virginia, Charlottesville, VA
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11
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Oeck S, Szymonowicz K, Wiel G, Krysztofiak A, Lambert J, Koska B, Iliakis G, Timmermann B, Jendrossek V. Relating Linear Energy Transfer to the Formation and Resolution of DNA Repair Foci After Irradiation with Equal Doses of X-ray Photons, Plateau, or Bragg-Peak Protons. Int J Mol Sci 2018; 19:ijms19123779. [PMID: 30486506 PMCID: PMC6320817 DOI: 10.3390/ijms19123779] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 11/24/2018] [Accepted: 11/26/2018] [Indexed: 12/27/2022] Open
Abstract
Proton beam therapy is increasingly applied for the treatment of human cancer, as it promises to reduce normal tissue damage. However, little is known about the relationship between linear energy transfer (LET), the type of DNA damage, and cellular repair mechanisms, particularly for cells irradiated with protons. We irradiated cultured cells delivering equal doses of X-ray photons, Bragg-peak protons, or plateau protons and used this set-up to quantitate initial DNA damage (mainly DNA double strand breaks (DSBs)), and to analyze kinetics of repair by detecting γH2A.X or 53BP1 using immunofluorescence. The results obtained validate the reliability of our set-up in delivering equal radiation doses under all conditions employed. Although the initial numbers of γH2A.X and 53BP1 foci scored were similar under the different irradiation conditions, it was notable that the maximum foci level was reached at 60 min after irradiation with Bragg-peak protons, as compared to 30 min for plateau protons and photons. Interestingly, Bragg-peak protons induced larger and irregularly shaped γH2A.X and 53BP1 foci. Additionally, the resolution of these foci was delayed. These results suggest that Bragg-peak protons induce DNA damage of increased complexity which is difficult to process by the cellular repair apparatus.
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Affiliation(s)
- Sebastian Oeck
- Institute of Cell Biology (Cancer Research), University of Duisburg-Essen, Medical School, Virchowstrasse 173, 45122 Essen, Germany.
- Department of Therapeutic Radiology, Yale University School of Medicine, 15 York Street, New Haven, CT 06520, USA.
| | - Klaudia Szymonowicz
- Institute of Cell Biology (Cancer Research), University of Duisburg-Essen, Medical School, Virchowstrasse 173, 45122 Essen, Germany.
| | - Gesa Wiel
- Institute of Cell Biology (Cancer Research), University of Duisburg-Essen, Medical School, Virchowstrasse 173, 45122 Essen, Germany.
| | - Adam Krysztofiak
- Institute of Cell Biology (Cancer Research), University of Duisburg-Essen, Medical School, Virchowstrasse 173, 45122 Essen, Germany.
| | - Jamil Lambert
- West German Proton Therapy Centre Essen, University Hospital Essen, Am Muehlenbach 1, 45147 Essen, Germany.
| | - Benjamin Koska
- West German Proton Therapy Centre Essen, University Hospital Essen, Am Muehlenbach 1, 45147 Essen, Germany.
| | - George Iliakis
- Institute of Medical Radiation Biology; University of Duisburg-Essen; Medical School; Hufelandstr. 55, 45122 Essen, Germany.
| | - Beate Timmermann
- West German Proton Therapy Centre Essen, University Hospital Essen, Am Muehlenbach 1, 45147 Essen, Germany.
| | - Verena Jendrossek
- Institute of Cell Biology (Cancer Research), University of Duisburg-Essen, Medical School, Virchowstrasse 173, 45122 Essen, Germany.
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12
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Stewart RD. Induction of DNA Damage by Light Ions Relative to 60Co γ-rays. Int J Part Ther 2018; 5:25-39. [PMID: 31773018 DOI: 10.14338/ijpt-18-00030] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 06/21/2018] [Indexed: 12/20/2022] Open
Abstract
The specific types and numbers of clusters of DNA lesions, including both DNA double-strand breaks (DSBs) and non-DSB clusters, are widely considered 1 of the most important initiating events underlying the relative biological effectiveness (RBE) of the light ions of interest in the treatment of cancer related to megavoltage x-rays and 60Co γ-rays. This review summarizes the categorization of DNA damage, reviews the underlying mechanisms of action by ionizing radiation, and quantifies the general trends in DSB and non-DSB cluster formation by light ions under normoxic and anoxic conditions, as predicted by Monte Carlo simulations that reflect the accumulated evidence from decades of research on radiation damage to DNA. The significance of the absolute and relative numbers of clusters and the local complexity of DSB and non-DSB clusters are discussed in relation to the formation of chromosome aberrations and the loss of cell reproductive capacity. Clinical implications of the dependence of DSB induction on ionization density is reviewed with an eye towards increasing the therapeutic ratio of proton and carbon ion therapy through the explicit optimization of RBE-weighted dose.
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Affiliation(s)
- Robert D Stewart
- Department of Radiation Oncology, University of Washington School of Medicine, Seattle, WA, USA
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Hill MA. Track to the future: historical perspective on the importance of radiation track structure and DNA as a radiobiological target. Int J Radiat Biol 2018; 94:759-768. [PMID: 29219655 PMCID: PMC6113897 DOI: 10.1080/09553002.2017.1387304] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 09/22/2017] [Accepted: 09/27/2017] [Indexed: 12/04/2022]
Abstract
PURPOSE Understanding the mechanisms behind induced biological response following exposure to ionizing radiation is not only important in assessing the risk associated with human exposure, but potentially can help identify ways of improving the efficacy of radiotherapy. Over the decades, there has been much discussion on what is the key biological target for radiation action and its associated size. It was already known in the 1930s that microscopic features of radiation significantly influenced biological outcomes. This resulted in the development of classic target theory, leading to field of microdosimetry and subsequently nanodosimetry, studying the inhomogeneity and stochastics of interactions, along with the identification of DNA as a key target. CONCLUSIONS Ultimately, the biological response has been found to be dependent on the radiation track structure (spatial and temporal distribution of ionization and excitation events). Clustering of energy deposition on the nanometer scale has been shown to play a critical role in determining biological response, producing not just simple isolated DNA lesions but also complex clustered lesions that are more difficult to repair. The frequency and complexity of these clustered damage sites are typically found to increase with increasing LET. However in order to fully understand the consequences, it is important to look at the relative distribution of these lesions over larger dimensions along the radiation track, up to the micrometer scale. Correlation of energy deposition events and resulting sites of DNA damage can ultimately result in complex gene mutations and complex chromosome rearrangements following repair, with the frequency and spectrum of the resulting rearrangements critically dependent on the spatial and temporal distribution of these sites and therefore the radiation track. Due to limitations in the techniques used to identify these rearrangements it is likely that the full complexity of the genetic rearrangements that occur has yet to be revealed. This paper discusses these issues from a historical perspective, with many of these historical studies still having relevance today. These can not only cast light on current studies but guide future studies, especially with the increasing range of biological techniques available. So, let us build on past knowledge to effectively explore the future.
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Affiliation(s)
- Mark A. Hill
- CRUK/MRC Oxford Institute for Radiation Oncology, University of Oxford, Gray Laboratories, ORCRB Roosevelt Drive, Oxford, UK
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Mavragani IV, Nikitaki Z, Souli MP, Aziz A, Nowsheen S, Aziz K, Rogakou E, Georgakilas AG. Complex DNA Damage: A Route to Radiation-Induced Genomic Instability and Carcinogenesis. Cancers (Basel) 2017; 9:cancers9070091. [PMID: 28718816 PMCID: PMC5532627 DOI: 10.3390/cancers9070091] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Revised: 07/06/2017] [Accepted: 07/14/2017] [Indexed: 12/26/2022] Open
Abstract
Cellular effects of ionizing radiation (IR) are of great variety and level, but they are mainly damaging since radiation can perturb all important components of the cell, from the membrane to the nucleus, due to alteration of different biological molecules ranging from lipids to proteins or DNA. Regarding DNA damage, which is the main focus of this review, as well as its repair, all current knowledge indicates that IR-induced DNA damage is always more complex than the corresponding endogenous damage resulting from endogenous oxidative stress. Specifically, it is expected that IR will create clusters of damage comprised of a diversity of DNA lesions like double strand breaks (DSBs), single strand breaks (SSBs) and base lesions within a short DNA region of up to 15–20 bp. Recent data from our groups and others support two main notions, that these damaged clusters are: (1) repair resistant, increasing genomic instability (GI) and malignant transformation and (2) can be considered as persistent “danger” signals promoting chronic inflammation and immune response, causing detrimental effects to the organism (like radiation toxicity). Last but not least, the paradigm shift for the role of radiation-induced systemic effects is also incorporated in this picture of IR-effects and consequences of complex DNA damage induction and its erroneous repair.
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Affiliation(s)
- Ifigeneia V Mavragani
- DNA Damage Laboratory, Physics Department, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Zografou Campus, 15780 Athens, Greece.
| | - Zacharenia Nikitaki
- DNA Damage Laboratory, Physics Department, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Zografou Campus, 15780 Athens, Greece.
| | - Maria P Souli
- DNA Damage Laboratory, Physics Department, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Zografou Campus, 15780 Athens, Greece.
| | - Asef Aziz
- Department of Pediatrics and Adolescent Medicine, Mayo Clinic, Rochester, MN 55905, USA.
| | - Somaira Nowsheen
- Mayo Medical Scientist Training Program, Mayo Medical School and Mayo Graduate School, Mayo Clinic, Rochester, MN 55905, USA.
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN 55905, USA.
| | - Khaled Aziz
- Mayo Medical Scientist Training Program, Mayo Medical School and Mayo Graduate School, Mayo Clinic, Rochester, MN 55905, USA.
| | - Emmy Rogakou
- First Department of Pediatrics, "Aghia Sophia" Children's Hospital, Medical School, University of Athens, 11527 Athens, Greece.
| | - Alexandros G Georgakilas
- DNA Damage Laboratory, Physics Department, School of Applied Mathematical and Physical Sciences, National Technical University of Athens, Zografou Campus, 15780 Athens, Greece.
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15
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Nikjoo H, Emfietzoglou D, Liamsuwan T, Taleei R, Liljequist D, Uehara S. Radiation track, DNA damage and response-a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:116601. [PMID: 27652826 DOI: 10.1088/0034-4885/79/11/116601] [Citation(s) in RCA: 181] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The purpose of this paper has been to review the current status and progress of the field of radiation biophysics, and draw attention to the fact that physics, in general, and radiation physics in particular, with the aid of mathematical modeling, can help elucidate biological mechanisms and cancer therapies. We hypothesize that concepts of condensed-matter physics along with the new genomic knowledge and technologies and mechanistic mathematical modeling in conjunction with advances in experimental DNA (Deoxyrinonucleic acid molecule) repair and cell signaling have now provided us with unprecedented opportunities in radiation biophysics to address problems in targeted cancer therapy, and genetic risk estimation in humans. Obviously, one is not dealing with 'low-hanging fruit', but it will be a major scientific achievement if it becomes possible to state, in another decade or so, that we can link mechanistically the stages between the initial radiation-induced DNA damage; in particular, at doses of radiation less than 2 Gy and with structural changes in genomic DNA as a precursor to cell inactivation and/or mutations leading to genetic diseases. The paper presents recent development in the physics of radiation track structure contained in the computer code system KURBUC, in particular for low-energy electrons in the condensed phase of water for which we provide a comprehensive discussion of the dielectric response function approach. The state-of-the-art in the simulation of proton and carbon ion tracks in the Bragg peak region is also presented. The paper presents a critical discussion of the models used for elastic scattering, and the validity of the trajectory approach in low-electron transport. Brief discussions of mechanistic and quantitative aspects of microdosimetry, DNA damage and DNA repair are also included as developed by the authors' work.
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Affiliation(s)
- H Nikjoo
- Radiation Biophysics Group, Department of Oncology-Pathology, Karolinska Institutet, Box 260, P9-02, Stockholm 17176, Sweden
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17
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Nikjoo H, Taleei R, Liamsuwan T, Liljequist D, Emfietzoglou D. Perspectives in radiation biophysics: From radiation track structure simulation to mechanistic models of DNA damage and repair. Radiat Phys Chem Oxf Engl 1993 2016. [DOI: 10.1016/j.radphyschem.2016.05.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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18
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Grassberger C, Paganetti H. Methodologies in the modeling of combined chemo-radiation treatments. Phys Med Biol 2016; 61:R344-R367. [DOI: 10.1088/0031-9155/61/21/r344] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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Woods ML, Barnes CP. Mechanistic Modelling and Bayesian Inference Elucidates the Variable Dynamics of Double-Strand Break Repair. PLoS Comput Biol 2016; 12:e1005131. [PMID: 27741226 PMCID: PMC5065155 DOI: 10.1371/journal.pcbi.1005131] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 09/05/2016] [Indexed: 12/12/2022] Open
Abstract
DNA double-strand breaks are lesions that form during metabolism, DNA replication and exposure to mutagens. When a double-strand break occurs one of a number of repair mechanisms is recruited, all of which have differing propensities for mutational events. Despite DNA repair being of crucial importance, the relative contribution of these mechanisms and their regulatory interactions remain to be fully elucidated. Understanding these mutational processes will have a profound impact on our knowledge of genomic instability, with implications across health, disease and evolution. Here we present a new method to model the combined activation of non-homologous end joining, single strand annealing and alternative end joining, following exposure to ionising radiation. We use Bayesian statistics to integrate eight biological data sets of double-strand break repair curves under varying genetic knockouts and confirm that our model is predictive by re-simulating and comparing to additional data. Analysis of the model suggests that there are at least three disjoint modes of repair, which we assign as fast, slow and intermediate. Our results show that when multiple data sets are combined, the rate for intermediate repair is variable amongst genetic knockouts. Further analysis suggests that the ratio between slow and intermediate repair depends on the presence or absence of DNA-PKcs and Ku70, which implies that non-homologous end joining and alternative end joining are not independent. Finally, we consider the proportion of double-strand breaks within each mechanism as a time series and predict activity as a function of repair rate. We outline how our insights can be directly tested using imaging and sequencing techniques and conclude that there is evidence of variable dynamics in alternative repair pathways. Our approach is an important step towards providing a unifying theoretical framework for the dynamics of DNA repair processes.
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Affiliation(s)
- Mae L. Woods
- Department of Cell and Developmental Biology, University College London, London, England
| | - Chris P. Barnes
- Department of Cell and Developmental Biology, University College London, London, England
- Department of Genetics, Evolution and Environment, University College London, London, England
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20
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Low doses of X-rays induce prolonged and ATM-independent persistence of γH2AX foci in human gingival mesenchymal stem cells. Oncotarget 2016; 6:27275-87. [PMID: 26314960 PMCID: PMC4694989 DOI: 10.18632/oncotarget.4739] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 07/10/2015] [Indexed: 12/11/2022] Open
Abstract
Diagnostic imaging delivering low doses of radiation often accompany human mesenchymal stem cells (MSCs)-based therapies. However, effects of low dose radiation on MSCs are poorly characterized. Here we examine patterns of phosphorylated histone H2AX (γH2AX) and phospho-S1981 ATM (pATM) foci formation in human gingiva-derived MSCs exposed to X-rays in time-course and dose-response experiments. Both γH2AX and pATM foci accumulated linearly with dose early after irradiation (5–60 min), with a maximum induction observed at 30–60 min (37 ± 3 and 32 ± 3 foci/cell/Gy for γH2AX and pATM, respectively). The number of γH2AX foci produced by intermediate doses (160 and 250 mGy) significantly decreased (40–60%) between 60 and 240 min post-irradiation, indicating rejoining of DNA double-strand breaks. In contrast, γH2AX foci produced by low doses (20–80 mGy) did not change after 60 min. The number of pATM foci between 60 and 240 min decreased down to control values in a dose-independent manner. Similar kinetics was observed for pATM foci co-localized with γH2AX foci. Collectively, our results suggest differential DNA double-strand break signaling and processing in response to low vs. intermediate doses of X-rays in human MSCs. Furthermore, mechanisms governing the prolonged persistence of γH2AX foci in these cells appear to be ATM-independent.
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Li M, Zhao Q, Yi X, Zhong X, Song G, Chai Z, Liu Z, Yang K. Au@MnS@ZnS Core/Shell/Shell Nanoparticles for Magnetic Resonance Imaging and Enhanced Cancer Radiation Therapy. ACS APPLIED MATERIALS & INTERFACES 2016; 8:9557-64. [PMID: 27039932 DOI: 10.1021/acsami.5b11588] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Although conventional radiotherapy (RT) has been widely used in the clinic to treat cancer, it often has limited therapeutic outcomes and severe toxic effects. There is still a need to develop theranostic agents with both imaging and RT-enhancing functions to improve the accuracy and efficiency of RT. Herein we synthesize Au@MnS@ZnS core/shell/shell nanoparticles with polyethylene glycol (PEG) functionalization, yielding Au@MnS@ZnS-PEG nanoparticles with great stability in different physiological solutions and no significant cytotoxicity. It is found that Au@MnS@ZnS-PEG nanoparticles can enhance the cancer cell killing efficiency induced by RT, as evidenced by multiple in vitro assays. Owing to the existence of paramagnetic Mn(2+) in the nanoparticle shell, our Au@MnS@ZnS-PEG can be used as a contrast agent for T1-weighted magnetic resonance (MR) imaging, which reveals the efficient accumulation and retention of nanoparticles in the tumors of mice after intravenous injection. Importantly, by exposing tumor-bearing mice that were injected with Au@MnS@ZnS-PEG to X-ray irradiation, the tumor growth can be significantly inhibited. This result shows clearly improved therapeutic efficacy compared to RT alone. Furthermore, no obvious side effect of Au@MnS@ZnS-PEG is observed in the injected mice. Therefore, our work presents a new type of radiosensitizing agent, which is promising for the imaging-guided enhanced RT treatment of cancer.
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Affiliation(s)
- Meifang Li
- School of Radiation Medicine and Protection & School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Medical College of Soochow University , Suzhou, Jiangsu 215123, China
| | - Qi Zhao
- School of Radiation Medicine and Protection & School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Medical College of Soochow University , Suzhou, Jiangsu 215123, China
| | - Xuan Yi
- School of Radiation Medicine and Protection & School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Medical College of Soochow University , Suzhou, Jiangsu 215123, China
| | - Xiaoyan Zhong
- School of Radiation Medicine and Protection & School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Medical College of Soochow University , Suzhou, Jiangsu 215123, China
| | - Guosheng Song
- Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials Laboratory (FUNSOM), Soochow University , Suzhou, Jiangsu 215123, China
| | - Zhifang Chai
- School of Radiation Medicine and Protection & School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Medical College of Soochow University , Suzhou, Jiangsu 215123, China
| | - Zhuang Liu
- Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials Laboratory (FUNSOM), Soochow University , Suzhou, Jiangsu 215123, China
| | - Kai Yang
- School of Radiation Medicine and Protection & School for Radiological and Interdisciplinary Sciences (RAD-X), Collaborative Innovation Center of Radiation Medicine of Jiangsu Higher Education Institutions, Medical College of Soochow University , Suzhou, Jiangsu 215123, China
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22
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Martin RF, Feinendegen LE. The quest to exploit the Auger effect in cancer radiotherapy - a reflective review. Int J Radiat Biol 2016; 92:617-632. [PMID: 26926313 DOI: 10.3109/09553002.2015.1136854] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
To identify the emergence of the recognition of the potential of the Auger effect for clinical application, and after tracing the salient milestones towards that goal, to evaluate the status quo and future prospects. It was not until 40 years after the discovery of Auger electrons, that the availability of radioactive DNA precursors enabled the biological power, and the clinical potential, of the Auger effect to be appreciated. Important milestones on the path to clinical translation have been identified and reached, but hurdles remain. Nevertheless the potential is still evident, and there is reasonable optimism that the goal of clinical translation is achievable.
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Affiliation(s)
- Roger F Martin
- a Molecular Radiation Biology Laboratory , Peter MacCallum Cancer Centre.,b The Sir Peter MacCallum Department of Oncology , The University of Melbourne.,c School of Chemistry and Bio-21 Molecular Science and Biotechnology Institute , University of Melbourne , Melbourne , Australia
| | - Ludwig E Feinendegen
- d Heinrich-Heine-University Düsseldorf , Germany.,e Brookhaven National Laboratory , Upton , NY , USA
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23
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Taleei R, Guan F, Peeler C, Bronk L, Patel D, Mirkovic D, Grosshans DR, Mohan R, Titt U. Monte Carlo simulations of3He ion physical characteristics in a water phantom and evaluation of radiobiological effectiveness. Med Phys 2016; 43:761-76. [DOI: 10.1118/1.4939440] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Hayashi H, Hiraoka N. Accurate Measurements of Dielectric and Optical Functions of Liquid Water and Liquid Benzene in the VUV Region (1-100 eV) Using Small-Angle Inelastic X-ray Scattering. J Phys Chem B 2015; 119:5609-23. [PMID: 25835527 DOI: 10.1021/acs.jpcb.5b01567] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Using a third-generation synchrotron source (the BL12XU beamline at SPring-8), inelastic X-ray scattering (IXS) spectra of liquid water and liquid benzene were measured at energy losses of 1-100 eV with 0.24 eV resolution for small momentum transfers (q) of 0.23 and 0.32 au with ±0.06 au uncertainty for q. For both liquids, the IXS profiles at these values of q converged well after we corrected for multiple scattering, and these results confirmed the dipole approximation for q ≤ ∼0.3 au. Several dielectric and optical functions [including the optical oscillator strength distribution (OOS), the optical energy-loss function (OLF), the complex dielectric function, the complex index of refraction, and the reflectance] in the vacuum ultraviolet region were derived and tabulated from these small-angle (small q) IXS spectra. These new data were compared with previously obtained results, and this comparison demonstrated the strong reproducibility and accuracy of IXS spectroscopy. For both water and benzene, there was a notable similarity between the OOSs of the liquids and amorphous solids, and there was no evidence of plasmon excitation in the OLF. The static structure factor [S(q)] for q ≤ ∼0.3 au was also deduced and suggests that molecular models that include electron correlation effects can serve as a good approximation for the liquid S(q) values over the full range of q.
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Affiliation(s)
- Hisashi Hayashi
- ‡Department of Chemical and Biological Sciences, Faculty of Science, Japan Women's University, 2-8-1 Mejirodai, Bunkyo, Tokyo 112-8681, Japan
| | - Nozomu Hiraoka
- †National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
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Sankaranarayanan K, Nikjoo H. Genome-based, mechanism-driven computational modeling of risks of ionizing radiation: The next frontier in genetic risk estimation? MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2014; 764:1-15. [PMID: 26041262 DOI: 10.1016/j.mrrev.2014.12.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/18/2014] [Indexed: 10/24/2022]
Abstract
Research activity in the field of estimation of genetic risks of ionizing radiation to human populations started in the late 1940s and now appears to be passing through a plateau phase. This paper provides a background to the concepts, findings and methods of risk estimation that guided the field through the period of its growth to the beginning of the 21st century. It draws attention to several key facts: (a) thus far, genetic risk estimates have been made indirectly using mutation data collected in mouse radiation studies; (b) important uncertainties and unsolved problems remain, one notable example being that we still do not know the sensitivity of human female germ cells to radiation-induced mutations; and (c) the concept that dominated the field thus far, namely, that radiation exposures to germ cells can result in single gene diseases in the descendants of those exposed has been replaced by the concept that radiation exposure can cause DNA deletions, often involving more than one gene. Genetic risk estimation now encompasses work devoted to studies on DNA deletions induced in human germ cells, their expected frequencies, and phenotypes and associated clinical consequences in the progeny. We argue that the time is ripe to embark on a human genome-based, mechanism-driven, computational modeling of genetic risks of ionizing radiation, and we present a provisional framework for catalyzing research in the field in the 21st century.
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Affiliation(s)
- K Sankaranarayanan
- Radiation Biophysics Group, Department of Oncology-Pathology, Karolinska Institutet, Box 260, P9-02, Stockholm SE 17176, Sweden
| | - H Nikjoo
- Radiation Biophysics Group, Department of Oncology-Pathology, Karolinska Institutet, Box 260, P9-02, Stockholm SE 17176, Sweden.
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