Publications by authors named "Giuseppe Schettino"

44 Publications

Corrigendum: Evaluating the Propagation of Uncertainties in Biologically Based Treatment Planning Parameters.

Front Oncol 2020 27;10:603976. Epub 2021 Jan 27.

National Physical Laboratory, Medical Radiation Science, Teddington, United Kingdom.

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http://dx.doi.org/10.3389/fonc.2020.603976DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7875016PMC
January 2021

UK adaptive radiotherapy practices for head and neck cancer patients.

BJR Open 2020 11;2(1):20200051. Epub 2020 Dec 11.

Department of Medical Physics & Biomedical Engineering, University College London, London, UK.

Objective: To provide evidence on the extent and manner in which adaptive practices have been employed in the UK and identify the main barriers for the clinical implementation of adaptive radiotherapy (ART) in head and neck (HN) cancer cases.

Methods: In December 2019, a Supplementary Material 1, of 23 questions, was sent to all UK radiotherapy centres (67). This covered general information to current ART practices and perceived barriers to implementation.

Results: 31 centres responded (46%). 56% responding centres employed ART for between 10 and 20 patients/annum. 96% of respondents were using CBCT either alone or with other modalities for assessing "weight loss" and "shell gap," which were the main reasons for ART. Adaptation usually occurs at week three or four during the radiotherapy treatment. 25 responding centres used an online image-guided radiotherapy (IGRT) approach and 20 used an offline ART approach, either with or without protocol level. Nearly 70% of respondents required 2 to 3 days to create an adaptive plan and 95% used 3-5 mm adaptive planning target volume margins. All centres performed pre-treatment QA. "Limited staff resources" and "lack of clinical relevance" were identified as the two main barriers for ART implementation.

Conclusion: There is no consensus in adaptive practice for HN cancer patients across the UK. For those centres not employing ART, similar clinical implementation barriers were identified.

Advances In Knowledge: An insight into contemporary UK practices of ART for HN cancer patients indicating national guidance for ART implementation for HN cancer patients may be required.
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http://dx.doi.org/10.1259/bjro.20200051DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7749087PMC
December 2020

Effects of Gadolinium MRI Contrast Agents on DNA Damage and Cell Survival when Used in Combination with Radiation.

Radiat Res 2020 09;194(3):298-309

Patrick G. Johnson Centre for Cancer Research, Queen's University Belfast, Belfast, BT9 7AE, United Kingdom.

Gadolinium is a commonly used contrast agent for magnetic resonance imaging (MRI). The goal of this work was to determine how MRI contrast agents affect radiosensitivity for tumour cells. Using a 225kVp X-ray cabinet source, immunofluorescence and clonogenic assays were performed on six cancer cell lines: lung (H460), pancreas (MiaPaCa2), prostate (DU145), breast (MCF7), brain (U87) and liver (HEPG2). Dotarem® contrast agent, at concentrations of 0.2, 2 and 20 mM, was used to determine its effect on DNA damage and cell survival. Measurements were performed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the amount of gadolinium taken up by each cell line for each concentration. A statistically significant increase in DNA damage was seen for all cell lines at a dose of 1 Gy for concentrations of 2 and 20 mM, at 1 h postirradiation. At 24 h postirradiation, most of the DNA damage had been repaired, with approximately 90% repair for almost all doses of radiation and concentrations of Dotarem. Clonogenic results showed no statistically significant decrease in cell survival for any cell line or concentration. Uptake measurements showed cell line-specific variations in uptake, with MCF7 and HEPG2 cells having a high percentage uptake compared to other cell lines, with 151.4 ± 0.3 × 10-15 g and 194.8 ± 0.4 × 10-15 g per cell, respectively, at 2 mM Dotarem concentration. In this work, a variability in gadolinium uptake was observed between cell lines. A significant increase was seen in initial levels of DNA damage after 1 Gy irradiation for all six cancer cell lines; however, no significant decrease in cell survival was seen with the clonogenic assay. The observation of high levels of repair suggest that while initial levels of DNA damage are increased, this damage is almost entirely repaired within 24 h, and does not affect the ability of cells to survive and produce colonies.
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http://dx.doi.org/10.1667/RADE-20-00008.1DOI Listing
September 2020

Evaluating the Propagation of Uncertainties in Biologically Based Treatment Planning Parameters.

Front Oncol 2020 21;10:1058. Epub 2020 Jul 21.

National Physical Laboratory, Metrology for Medical Physics Department, Teddington, United Kingdom.

Biologically based treatment planning is a broad term used to cover any instance in radiotherapy treatment planning where some form of biological input has been used. This is wide ranging, and the simpler forms (e.g., fractionation modification/optimization) have been in use for many years. However, there is a reluctance to use more sophisticated methods that incorporate biological models either for plan evaluation purposes or for driving plan optimizations. This is due to limited data available regarding the uncertainties in these model parameters and what impact these have clinically. This work aims to address some of these issues and to explore the role that uncertainties in individual model parameters have on the overall tissue control probability (TCP)/normal tissue control probability (NTCP) calculated, those parameters that have the largest influence and situations where extra care must be taken. In order to achieve this, a software tool was developed, which can import individual clinical DVH's for analysis using a range of different TCP/NTCP models. On inputting individual model parameters, an uncertainty can be applied. Using a normally distributed random number generator, distributions of parameters can be generated, from which TCP/NTCP values can be calculated for each parameter set for the DVH in question. These represent the spread in TCP/NTCP parameters that would be observed for a simulated population of patients all being treated with that particular dose distribution. A selection of clinical DVHs was assessed using published parameters and their associated uncertainties. A range of studies was carried out to determine the impact of individual parameter uncertainties including reduction of uncertainties and assessment of what impact fractionation and dose have on these probabilities.
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http://dx.doi.org/10.3389/fonc.2020.01058DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7386327PMC
July 2020

Evaluation of a Novel Liquid Fiducial Marker, BioXmark, for Small Animal Image-Guided Radiotherapy Applications.

Cancers (Basel) 2020 May 18;12(5). Epub 2020 May 18.

Patrick G. Johnston Centre for Cancer Research, Queen's University Belfast, Belfast BT9 7AE, UK.

BioXmark (Nanovi A/S, Denmark) is a novel fiducial marker based on a liquid, iodine-based and non-metallic formulation. BioXmark has been clinically validated and reverse translated to preclinical models to improve cone-beam CT (CBCT) target delineation in small animal image-guided radiotherapy (SAIGRT). However, in phantom image analysis and in vivo evaluation of radiobiological response after the injection of BioXmark are yet to be reported. In phantom measurements were performed to compare CBCT imaging artefacts with solid fiducials and determine optimum imaging parameters for BioXmark. In vivo stability of BioXmark was assessed over a 5-month period, and the impact of BioXmark on in vivo tumour response from single-fraction and fractionated X-ray exposures was investigated in a subcutaneous syngeneic tumour model. BioXmark was stable, well tolerated and detectable on CBCT at volumes ≤10 µL. Our data showed imaging artefacts reduced by up to 84% and 89% compared to polymer and gold fiducial markers, respectively. BioXmark was shown to have no significant impact on tumour growth in control animals, but changes were observed in irradiated animals injected with BioXmark due to alterations in dose calculations induced by the sharp contrast enhancement. BioXmark is superior to solid fiducials with reduced imaging artefacts on CBCT. With minimal impact on the tumour growth delay, BioXmark can be implemented in SAIGRT to improve target delineation and reduce set-up errors.
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http://dx.doi.org/10.3390/cancers12051276DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7280978PMC
May 2020

A Novel Scaffold-Based Hybrid Multicellular Model for Pancreatic Ductal Adenocarcinoma-Toward a Better Mimicry of the Tumor Microenvironment.

Front Bioeng Biotechnol 2020 24;8:290. Epub 2020 Apr 24.

Bioprocess and Biochemical Engineering Group (BioProChem), Department of Chemical and Process Engineering, University of Surrey, Guildford, United Kingdom.

With a very low survival rate, pancreatic ductal adenocarcinoma (PDAC) is a deadly disease. This has been primarily attributed to (i) its late diagnosis and (ii) its high resistance to current treatment methods. The latter specifically requires the development of robust, realistic models of PDAC, capable of accurately mimicking the tumor niche. Advancements in the field of tissue engineering (TE) have helped the development of such models for PDAC. Herein, we report for the first time a novel hybrid, polyurethane (PU) scaffold-based, long-term, multicellular (tri-culture) model of pancreatic cancer involving cancer cells, endothelial cells, and stellate cells. Recognizing the importance of ECM proteins for optimal growth of different cell types, the model consists of two different zones/compartments: an inner tumor compartment consisting of cancer cells [fibronectin (FN)-coated] and a surrounding stromal compartment consisting of stellate and endothelial cells [collagen I (COL)-coated]. Our developed novel hybrid, tri-culture model supports the proliferation of all different cell types for 35 days (5 weeks), which is the longest reported timeframe . Furthermore, the hybrid model showed extensive COL production by the cells, mimicking desmoplasia, one of PDAC's hallmark features. Fibril alignment of the stellate cells was observed, which attested to their activated state. All three cell types expressed various cell-specific markers within the scaffolds, throughout the culture period and showed cellular migration between the two zones of the hybrid scaffold. Our novel model has great potential as a low-cost tool for studies of PDAC, as well as for treatment screening.
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http://dx.doi.org/10.3389/fbioe.2020.00290DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7193232PMC
April 2020

An open source heterogeneous 3D printed mouse phantom utilising a novel bone representative thermoplastic.

Phys Med Biol 2020 06 3;65(10):10NT02. Epub 2020 Jun 3.

University of Manchester, Manchester Academic Health Science Centre, The Christie NHS Foundation Trust, Wilmslow Road, Manchester M20 4BX, United Kingdom. Authors contributed equally. Author to whom any correspondence should be addressed.

The lack of rigorous quality standards in pre-clinical radiation dosimetry has renewed interest in the development of anthropomorphic phantoms. Using 3D printing customisable phantoms can be created to assess all parts of pre-clinical radiation research: planning, image guidance and treatment delivery. We present the full methodology, including material development and printing designs, for the production of a high spatial resolution, anatomically realistic heterogeneous small animal phantom. A methodology for creating and validating tissue equivalent materials is presented. The technique is demonstrated through the development of a bone-equivalent material. This material is used together with a soft-tissue mimicking ABS plastic filament to reproduce the corresponding structure geometries captured from a CT scan of a nude mouse. Air gaps are used to represent the lungs. Phantom validation was performed through comparison of the geometry and x-ray attenuation of CT images of the phantom and animal images. A 6.6% difference in the attenuation of the bone-equivalent material compared to the reference standard in softer beams (0.5 mm Cu HVL) rapidly decreases as the beam is hardened. CT imaging shows accurate (sub-millimetre) reproduction of the skeleton (Distance-To-Agreement 0.5 mm ± 0.4 mm) and body surface (0.7 mm ± 0.5 mm). Histograms of the voxel intensity profile of the phantom demonstrate suitable similarity to those of both the original mouse image and that of a different animal. We present an approach for the efficient production of an anthropomorphic phantom suitable for the quality assurance of pre-clinical radiotherapy. Our design and full methodology are provided as open source to encourage the pre-clinical radiobiology community to adopt a common QA standard.
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http://dx.doi.org/10.1088/1361-6560/ab8078DOI Listing
June 2020

Development and Implementation of an End-To-End Test for Absolute Dose Verification of Small Animal Preclinical Irradiation Research Platforms.

Int J Radiat Oncol Biol Phys 2020 07 10;107(3):587-596. Epub 2020 Mar 10.

Medical Physics Department, National Physical Laboratory, Teddington, United Kingdom; Department of Physics, Faculty of Engineering and Physical Sciences. University of Surrey, Guildford, United Kingdom.

Purpose: Lack of standardization and inaccurate dosimetry assessment in preclinical research is hampering translational opportunities for new radiation therapy interventions. The aim of this work was to develop and implement an end-to-end dosimetry test for small animal radiation research platforms to monitor and help improve accuracy of dose delivery and standardization across institutions.

Methods And Materials: The test is based on a bespoke zoomorphic heterogeneous mouse and WT1 Petri dish phantoms with alanine as a reference detector. Alanine measurements within the mouse phantom were validated with Monte Carlo simulations at 0.5 mm Cu x-ray reference beam. Energy dependence of alanine in medium x-ray beam qualities was taken into consideration. For the end-to-end test, treatment plans considering tissue heterogeneities were created in Muriplan treatment planning systems (TPS) and delivered to the phantoms at 5 institutions using Xstrahl's small animal irradiation platforms. Mean calculated dose to the pellets were compared with alanine measured dose.

Results: Monte Carlo simulations and in phantom alanine measurements in NPL's reference beam were in excellent agreement, validating the experimental approach. At 1 institute, initial measurements showed a larger than 12% difference between calculated and measured dose caused by incorrect input data. The physics data used by the calculation engine were corrected, and the TPS was recommissioned. Subsequent end-to-end test measurements showed differences <5%. With an anterior field, 4 of the participating institutes delivered dose within 5% to both phantoms.

Conclusions: An end-to-end dosimetry test was developed and implemented for dose evaluation in preclinical irradiation with small animal irradiation research platforms. The test was capable of detecting treatment planning commissioning errors and highlighted critical elements in dose calculation. Absolute dosimetry with alanine in relevant preclinical irradiation conditions showed reasonable levels of accuracy compared with TPS calculations. This work provides an independent and traceable dosimetric validation in preclinical research involving small animal irradiation.
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http://dx.doi.org/10.1016/j.ijrobp.2020.03.001DOI Listing
July 2020

The influence of lack of reference conditions on dosimetry in pre-clinical radiotherapy with medium energy x-ray beams.

Phys Med Biol 2020 04 23;65(8):085016. Epub 2020 Apr 23.

National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom. Author to whom any correspondence should be addressed.

Despite well-established dosimetry in clinical radiotherapy, dose measurements in pre-clinical and radiobiology studies are frequently inadequate, thus undermining the reliability and reproducibility of published findings. The lack of suitable dosimetry protocols, coupled with the increasing complexity of pre-clinical irradiation platforms, undermines confidence in preclinical studies and represents a serious obstacle in the translation to clinical practice. To accurately measure output of a pre-clinical radiotherapy unit, appropriate Codes of Practice (CoP) for medium energy x-rays needs to be employed. However, determination of absorbed dose to water (D) relies on application of backscatter factor (B) employing in-air method or carrying out in-phantom measurement at the reference depth of 2 cm in a full backscatter (i.e. 30 × 30 × 30 cm) condition. Both of these methods require thickness of at least 30 cm of underlying material, which are never fulfilled in typical pre-clinical irradiations. This work is focused on evaluation the effects of the lack of recommended reference conditions in dosimetry measurements for pre-clinical settings and is aimed at extending the recommendations of the current CoP to practical experimental conditions and highlighting the potential impact of the lack of correct backscatter considerations on radiobiological studies.
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http://dx.doi.org/10.1088/1361-6560/ab7b30DOI Listing
April 2020

The effect of radioiodine treatment on the diseased thyroid gland.

Int J Radiat Biol 2019 12 16;95(12):1718-1727. Epub 2019 Sep 16.

Biomedical Sciences, University of Hull, Hull, UK.

Radioiodine (I) therapy is the treatment mainstay for several benign and malignant thyroid disorders, however I is known to cause DNA damage and liberation of thyroidal self-antigens inducing secondary immunoreactivity. The exact mechanisms underpinning cellular death and subsequent induction of autoimmune thyroid disease following I treatment have not yet been fully elucidated. This manuscript aims to review the literature concerning the effects of I on the thyroid gland. The effects of I on malignant thyroid cells appears to depend on absorbed dose with the literature demonstrating a clear initial delay in the triggering of apoptosis in response to I-mediated cellular damage. Some studies also observed necrotic cellular death following high-dose I treatment. Liberation of thyroidal self-antigen following I treatment helps to explain phenomena such as the subsequent induction of autoimmune thyroid disease. The clinical utility of cytokines and autoantibodies for prognostication of hypothyroidism and treatment failure following I remains uncertain and further appropriately-powered studies are required to clarify their role. The potential role of other cell death mechanisms activated after treatment with I should also be explored in order to fully delineate the thyroidal response.
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http://dx.doi.org/10.1080/09553002.2019.1665206DOI Listing
December 2019

Development of an anatomically correct mouse phantom for dosimetry measurement in small animal radiotherapy research.

Phys Med Biol 2019 06 21;64(12):12NT02. Epub 2019 Jun 21.

Department of Biomedical Sciences, University of Hull, Hull, United Kingdom. Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America.

Significant improvements in radiotherapy are likely to come from biological rather than technical optimization, for example increasing tumour radiosensitivity via combination with targeted therapies. Such paradigms must first be evaluated in preclinical models for efficacy, and recent advances in small animal radiotherapy research platforms allow advanced irradiation protocols, similar to those used clinically, to be carried out in orthotopic models. Dose assessment in such systems is complex however, and a lack of established tools and methodologies for traceable and accurate dosimetry is currently limiting the capabilities of such platforms and slowing the clinical uptake of new approaches. Here we report the creation of an anatomically correct phantom, fabricated from materials with tissue-equivalent electron density, into which dosimetry detectors can be incorporated for measurement as part of quality control (QC). The phantom also allows training in preclinical radiotherapy planning and cross-institution validation of dose delivery protocols for small animal radiotherapy platforms without the need to sacrifice animals, with high reproducibility. Mouse CT data was acquired and segmented into soft tissue, bone and lung. The skeleton was fabricated using 3D printing, whilst lung was created using computer numerical control (CNC) milling. Skeleton and lung were then set into a surface-rendered mould and soft tissue material added to create a whole-body phantom. Materials for fabrication were characterized for atomic composition and attenuation for x-ray energies typically found in small animal irradiators. Finally cores were CNC milled to allow intracranial incorporation of bespoke detectors (alanine pellets) for dosimetry measurement.
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http://dx.doi.org/10.1088/1361-6560/ab215bDOI Listing
June 2019

Using the Proton Energy Spectrum and Microdosimetry to Model Proton Relative Biological Effectiveness.

Int J Radiat Oncol Biol Phys 2019 06 5;104(2):316-324. Epub 2019 Feb 5.

Department of Radiation Physics, University of Texas MD Anderson Cancer Center, Houston, Texas.

Purpose: We introduce a methodology to calculate the microdosimetric quantity dose-mean lineal energy for input into the microdosimetric kinetic model (MKM) to model the relative biological effectiveness (RBE) of proton irradiation experiments.

Methods And Materials: The data from 7 individual proton RBE experiments were included in this study. In each experiment, the RBE at several points along the Bragg curve was measured. Monte Carlo simulations to calculate the lineal energy probability density function of 172 different proton energies were carried out with use of Geant4 DNA. We calculated the fluence-weighted lineal energy probability density function (f(y)), based on the proton energy spectra calculated through Monte Carlo at each experimental depth, calculated the dose-mean lineal energy y¯ for input into the MKM, and then computed the RBE. The radius of the domain (r) was varied to reach the best agreement between the MKM-predicted RBE and experimental RBE. A generic RBE model as a function of dose-averaged linear energy transfer (LET) with 1 fitting parameter was presented and fit to the experimental RBE data as well to facilitate a comparison to the MKM.

Results: Both the MKM and LET-based models modeled the RBE from experiments well. Values for r were similar to those of other cell lines under proton irradiation that were modeled with the MKM. Analysis of the performance of each model revealed that neither model was clearly superior to the other.

Conclusions: Our 3 key accomplishments include the following: (1) We developed a method that uses the proton energy spectra and lineal energy distributions of those protons to calculate dose-mean lineal energy. (2) We demonstrated that our application of the MKM provides theoretical validation of proton irradiation experiments that show that RBE is significantly greater than 1.1. (3) We showed that there is no clear evidence that the MKM is better than LET-based RBE models.
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http://dx.doi.org/10.1016/j.ijrobp.2019.01.094DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6499683PMC
June 2019

Biological effects of static magnetic field exposure in the context of MR-guided radiotherapy.

Br J Radiol 2019 Feb 31;92(1094):20180484. Epub 2018 Oct 31.

1 Department of Physics, University of Surrey , Guildford , UK.

The clinical introduction of MRI-guided radiotherapy has prompted consideration of the potential impact of the static magnetic field on biological responses to radiation. This review provides an introduction to the mechanisms of biological interaction of radiation and magnetic fields individually, in addition to a description of the magnetic field effects on megavoltage photon beams at the macroscale, microscale and nanoscale arising from the Lorentz force on secondary charged particles. A relatively small number of scientific studies have measured the impact of combined static magnetic fields and ionising radiation on biological endpoints of relevance to radiotherapy. Approximately, half of these investigations found that static magnetic fields in combination with ionising radiation produced a significantly different outcome compared with ionising radiation alone. strength static magnetic fields appear to modestly influence the radiation response via a mechanism distinct from modification to the dose distribution. This review intends to serve as a reference for future biological studies, such that understanding of static magnetic field plus ionising radiation synergism may be improved, and if necessary, accounted for in MRI-guided radiotherapy treatment planning.
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http://dx.doi.org/10.1259/bjr.20180484DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6404846PMC
February 2019

Recommendations for clinical translation of nanoparticle-enhanced radiotherapy.

Br J Radiol 2018 Dec 17;91(1092):20180325. Epub 2018 Sep 17.

17 Department of Medical Physics and Bioengineering, University College London , London , UK.

A multi-disciplinary cooperative for nanoparticle-enhanced radiotherapy (NERT) has been formed to review the current status of the field and identify key stages towards translation. Supported by the Colorectal Cancer Healthcare Technologies Cooperative, the cooperative comprises a diverse cohort of key contributors along the translation pathway including academics of physics, cancer and radio-biology, chemistry, nanotechnology and clinical trials, clinicians, manufacturers, industry, standards laboratories, policy makers and patients. Our aim was to leverage our combined expertise to devise solutions towards a roadmap for translation and commercialisation of NERT, in order to focus research in the direction of clinical implementation, and streamline the critical pathway from basic science to the clinic. A recent meeting of the group identified barriers to and strategies for accelerated clinical translation. This commentary reports the cooperative's recommendations. Particular emphasis was given to more standardised and cohesive research methods, models and outputs, and reprioritised research drivers including patient quality of life following treatment. Nanoparticle design criteria were outlined to incorporate scalability of manufacture, understanding and optimisation of biological mechanisms of enhancement and in vivo fate of nanoparticles, as well as existing design criteria for physical and chemical enhancement. In addition, the group aims to establish a long-term and widespread international community to disseminate key findings and create a much-needed cohesive body of evidence necessary for commercial and clinical translation.
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http://dx.doi.org/10.1259/bjr.20180325DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6319829PMC
December 2018

Microbeam evolution: from single cell irradiation to pre-clinical studies.

Int J Radiat Biol 2018 08 22;94(8):708-718. Epub 2018 Jan 22.

a Centre for Cancer Research and Cell Biology , Queen's University Belfast , Belfast , UK.

Purpose: This review follows the development of microbeam technology from the early days of single cell irradiations, to investigations of specific cellular mechanisms and to the development of new treatment modalities in vivo. A number of microbeam applications are discussed with a focus on pre-clinical modalities and translation towards clinical application.

Conclusions: The development of radiation microbeams has been a valuable tool for the exploration of fundamental radiobiological response mechanisms. The strength of micro-irradiation techniques lies in their ability to deliver precise doses of radiation to selected individual cells in vitro or even to target subcellular organelles. These abilities have led to the development of a range of microbeam facilities around the world allowing the delivery of precisely defined beams of charged particles, X-rays, or electrons. In addition, microbeams have acted as mechanistic probes to dissect the underlying molecular events of the DNA damage response following highly localized dose deposition. Further advances in very precise beam delivery have also enabled the transition towards new and exciting therapeutic modalities developed at synchrotrons to deliver radiotherapy using plane parallel microbeams, in Microbeam Radiotherapy (MRT).
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http://dx.doi.org/10.1080/09553002.2018.1425807DOI Listing
August 2018

Small field dosimetry for the small animal radiotherapy research platform (SARRP).

Radiat Oncol 2017 Dec 28;12(1):204. Epub 2017 Dec 28.

Centre for Cancer Research and Cell Biology, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7AE, UK.

Background: Preclinical radiation biology has become increasingly sophisticated due to the implementation of advanced small animal image guided radiation platforms into laboratory investigation. These small animal radiotherapy devices enable state-of-the-art image guided therapy (IGRT) research to be performed by combining high-resolution cone beam computed tomography (CBCT) imaging with an isocentric irradiation system. Such platforms are capable of replicating modern clinical systems similar to those that integrate a linear accelerator with on-board CBCT image guidance.

Methods: In this study, we present a dosimetric evaluation of the small animal radiotherapy research platform (SARRP, Xstrahl Inc.) focusing on small field dosimetry. Physical dosimetry was assessed using ion chamber for calibration and radiochromic film, investigating the impact of beam focus size on the dose rate output as well as beam characteristics (beam shape and penumbra). Two film analysis tools) have been used to assess the dose output using the 0.5 mm diameter aperture.

Results: Good agreement (between 1.7-3%) was found between the measured physical doses and the data provided by Xstrahl for all apertures used. Furthermore, all small field dosimetry data are in good agreement for both film reading methods and with our Monte Carlo simulations for both focal spot sizes. Furthermore, the small focal spot has been shown to produce a more homogenous beam with more stable penumbra over time.

Conclusions: FilmQA Pro is a suitable tool for small field dosimetry, with a sufficiently small sampling area (0.1 mm) to ensure an accurate measurement. The electron beam focus should be chosen with care as this can potentially impact on beam stability and reproducibility.
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http://dx.doi.org/10.1186/s13014-017-0936-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5745702PMC
December 2017

A mechanistic study of gold nanoparticle radiosensitisation using targeted microbeam irradiation.

Sci Rep 2017 03 16;7:44752. Epub 2017 Mar 16.

Centre for Cancer Research and Cell Biology, Queen's University Belfast, 97 Lisburn Road, BT7 9AE, Belfast, UK.

Gold nanoparticles (GNPs) have been demonstrated as effective radiosensitizing agents in a range of preclinical models using broad field sources of various energies. This study aimed to distinguish between these mechanisms by applying subcellular targeting using a soft X-ray microbeam in combination with GNPs. DNA damage and repair kinetics were determined following nuclear and cytoplasmic irradiation using a soft X-ray (carbon K-shell, 278 eV) microbeam in MDA-MB-231 breast cancer and AG01522 fibroblast cells with and without GNPs. To investigate the mechanism of the GNP induced radiosensitization, GNP-induced mitochondrial depolarisation was quantified by TMRE staining, and levels of DNA damage were compared in cells with depolarised and functional mitochondria. Differential effects were observed following radiation exposure between the two cell lines. These findings were validated 24 hours after removal of GNPs by flow cytometry analysis of mitochondrial depolarisation. This study provides further evidence that GNP radiosensitisation is mediated by mitochondrial function and it is the first report applying a soft X-ray microbeam to study the radiobiological effects of GNPs to enable the separation of physical and biological effects.
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http://dx.doi.org/10.1038/srep44752DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5353761PMC
March 2017

Pro-inflammatory Signaling in a 3D Organotypic Skin Model after Low LET Irradiation-NF-κB, COX-2 Activation, and Impact on Cell Differentiation.

Front Immunol 2017 10;8:82. Epub 2017 Feb 10.

Queen's University Belfast, Centre for Cancer Research and Cell Biology , Belfast , UK.

Nearly 85% of radiotherapy patients develop acute radiation dermatitis, which is an inflammatory reaction of the skin at the treatment field and in the surrounding area. The aims of this study were to unravel the mechanisms of radiation-induced inflammatory responses after localized irradiation in a human 3D organotypic skin culture model. This could provide possible inflammatory targets for reduction of skin side effects. 3D organotypic skin cultures were set up and locally irradiated with 225 kVp X-rays, using a combination of full exposure and partial shielding (50%) of the cultures. The secretion of pro-inflammatory cytokines, the phenotype, and the differentiation markers expression of the cultures were assessed up to 10 days postirradiation. The pro-inflammatory transcription factor nuclear factor kappa B (NF-κB) and cyclooxygenase-2 (COX-2) pathways have been studied. The results showed fast activation of NF-κB, most likely triggered by DNA damage in the irradiated cells, followed by upregulation of p38 MAPK and COX-2 in the irradiated and surrounding, non-irradiated, areas of the 3D cultures. The application of the COX-2 inhibitor sc-236 was effective at reducing the COX-2 mRNA levels 4 h postirradiation. The same inhibitor also suppressed the PGE2 secretion significantly 72 h after the treatment. The expression of a pro-inflammatory phenotype and abnormal differentiation markers of the cultures were also reduced. However, the use of an NF-κB inhibitor (Bay 11-7085) did not have the predicted positive effect on the cultures phenotype postirradiation. Radiation-induced pro-inflammatory responses have been observed in the 3D skin model. The activated signaling pathways involved NF-κB transcription factor and its downstream target COX-2. Further experiments aiming to suppress the inflammatory response specific inhibitors showed that COX-2 is a suitable target for reduction of the normal skin inflammatory responses at radiotherapy, while NF-κB inhibition had detrimental effects on the 3D skin model development.
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http://dx.doi.org/10.3389/fimmu.2017.00082DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5300980PMC
February 2017

Biological mechanisms of gold nanoparticle radiosensitization.

Cancer Nanotechnol 2017 2;8(1). Epub 2017 Feb 2.

Centre for Cancer Research and Cell Biology, Queens University Belfast, 97 Lisburn Road, Belfast, BT9 7AE Northern Ireland, UK.

There has been growing interest in the use of nanomaterials for a range of biomedical applications over the last number of years. In particular, gold nanoparticles (GNPs) possess a number of unique properties that make them ideal candidates as radiosensitizers on the basis of their strong photoelectric absorption coefficient and ease of synthesis. However, despite promising preclinical evidence in vitro supported by a limited amount of in vivo experiments, along with advances in mechanistic understanding, GNPs have not yet translated into the clinic. This may be due to disparity between predicted levels of radiosensitization based on physical action, observed biological response and an incomplete mechanistic understanding, alongside current experimental limitations. This paper provides a review of the current state of the field, highlighting the potential underlying biological mechanisms in GNP radiosensitization and examining the barriers to clinical translation.
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http://dx.doi.org/10.1186/s12645-017-0026-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5288470PMC
February 2017

Standards and Methodologies for Characterizing Radiobiological Impact of High-Z Nanoparticles.

Theranostics 2016 20;6(10):1651-71. Epub 2016 Jun 20.

Radiation Dosimetry, National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK.

Research on the application of high-Z nanoparticles (NPs) in cancer treatment and diagnosis has recently been the subject of growing interest, with much promise being shown with regards to a potential transition into clinical practice. In spite of numerous publications related to the development and application of nanoparticles for use with ionizing radiation, the literature is lacking coherent and systematic experimental approaches to fully evaluate the radiobiological effectiveness of NPs, validate mechanistic models and allow direct comparison of the studies undertaken by various research groups. The lack of standards and established methodology is commonly recognised as a major obstacle for the transition of innovative research ideas into clinical practice. This review provides a comprehensive overview of radiobiological techniques and quantification methods used in in vitro studies on high-Z nanoparticles and aims to provide recommendations for future standardization for NP-mediated radiation research.
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http://dx.doi.org/10.7150/thno.15019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4955064PMC
October 2017

Investigating the Implications of a Variable RBE on Proton Dose Fractionation Across a Clinical Pencil Beam Scanned Spread-Out Bragg Peak.

Int J Radiat Oncol Biol Phys 2016 May 13;95(1):70-77. Epub 2016 Feb 13.

Centre for Cancer Research and Cell Biology, Queen's University, Belfast, UK.

Purpose: To investigate the clinical implications of a variable relative biological effectiveness (RBE) on proton dose fractionation. Using acute exposures, the current clinical adoption of a generic, constant cell killing RBE has been shown to underestimate the effect of the sharp increase in linear energy transfer (LET) in the distal regions of the spread-out Bragg peak (SOBP). However, experimental data for the impact of dose fractionation in such scenarios are still limited.

Methods And Materials: Human fibroblasts (AG01522) at 4 key depth positions on a clinical SOBP of maximum energy 219.65 MeV were subjected to various fractionation regimens with an interfraction period of 24 hours at Proton Therapy Center in Prague, Czech Republic. Cell killing RBE variations were measured using standard clonogenic assays and were further validated using Monte Carlo simulations and parameterized using a linear quadratic formalism.

Results: Significant variations in the cell killing RBE for fractionated exposures along the proton dose profile were observed. RBE increased sharply toward the distal position, corresponding to a reduction in cell sparing effectiveness of fractionated proton exposures at higher LET. The effect was more pronounced at smaller doses per fraction. Experimental survival fractions were adequately predicted using a linear quadratic formalism assuming full repair between fractions. Data were also used to validate a parameterized variable RBE model based on linear α parameter response with LET that showed considerable deviations from clinically predicted isoeffective fractionation regimens.

Conclusions: The RBE-weighted absorbed dose calculated using the clinically adopted generic RBE of 1.1 significantly underestimates the biological effective dose from variable RBE, particularly in fractionation regimens with low doses per fraction. Coupled with an increase in effective range in fractionated exposures, our study provides an RBE dataset that can be used by the modeling community for the optimization of fractionated proton therapy.
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http://dx.doi.org/10.1016/j.ijrobp.2016.02.029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4838672PMC
May 2016

Imaging and radiation effects of gold nanoparticles in tumour cells.

Sci Rep 2016 Jan 20;6:19442. Epub 2016 Jan 20.

Centre for Plasma Physics, School of Mathematics and Physics, Queen's University Belfast, Belfast, BT7 1NN, Northern Ireland, UK.

Gold nanoparticle radiosensitization represents a novel technique in enhancement of ionising radiation dose and its effect on biological systems. Variation between theoretical predictions and experimental measurement is significant enough that the mechanism leading to an increase in cell killing and DNA damage is still not clear. We present the first experimental results that take into account both the measured biodistribution of gold nanoparticles at the cellular level and the range of the product electrons responsible for energy deposition. Combining synchrotron-generated monoenergetic X-rays, intracellular gold particle imaging and DNA damage assays, has enabled a DNA damage model to be generated that includes the production of intermediate electrons. We can therefore show for the first time good agreement between the prediction of biological outcomes from both the Local Effect Model and a DNA damage model with experimentally observed cell killing and DNA damage induction via the combination of X-rays and GNPs. However, the requirement of two distinct models as indicated by this mechanistic study, one for short-term DNA damage and another for cell survival, indicates that, at least for nanoparticle enhancement, it is not safe to equate the lethal lesions invoked in the local effect model with DNA damage events.
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http://dx.doi.org/10.1038/srep19442DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4726169PMC
January 2016

Impact of fractionation on out-of-field survival and DNA damage responses following exposure to intensity modulated radiation fields.

Phys Med Biol 2016 Jan 18;61(2):515-26. Epub 2015 Dec 18.

Centre for Cancer Research and Cell Biology, Queen's University Belfast, 97 Lisburn Road, BT7 9AE, Belfast, UK.

To limit toxicity to normal tissues adjacent to the target tumour volume, radiotherapy is delivered using fractionated regimes whereby the total prescribed dose is given as a series of sequential smaller doses separated by specific time intervals. The impact of fractionation on out-of-field survival and DNA damage responses was determined in AGO-1522 primary human fibroblasts and MCF-7 breast tumour cells using uniform and modulated exposures delivered using a 225 kVp x-ray source. Responses to fractionated schedules (two equal fractions delivered with time intervals from 4 h to 48 h) were compared to those following acute exposures. Cell survival and DNA damage repair measurements indicate that cellular responses to fractionated non-uniform exposures differ from those seen in uniform exposures for the investigated cell lines. Specifically, there is a consistent lack of repair observed in the out-of-field populations during intervals between fractions, confirming the importance of cell signalling to out-of-field responses in a fractionated radiation schedule, and this needs to be confirmed for a wider range of cell lines and conditions.
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http://dx.doi.org/10.1088/0031-9155/61/2/515DOI Listing
January 2016

Variations in the Processing of DNA Double-Strand Breaks Along 60-MeV Therapeutic Proton Beams.

Int J Radiat Oncol Biol Phys 2016 May 29;95(1):86-94. Epub 2015 Jul 29.

Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, United Kingdom.

Purpose: To investigate the variations in induction and repair of DNA damage along the proton path, after a previous report on the increasing biological effectiveness along clinically modulated 60-MeV proton beams.

Methods And Materials: Human skin fibroblast (AG01522) cells were irradiated along a monoenergetic and a modulated spread-out Bragg peak (SOBP) proton beam used for treating ocular melanoma at the Douglas Cyclotron, Clatterbridge Centre for Oncology, Wirral, Liverpool, United Kingdom. The DNA damage response was studied using the 53BP1 foci formation assay. The linear energy transfer (LET) dependence was studied by irradiating the cells at depths corresponding to entrance, proximal, middle, and distal positions of SOBP and the entrance and peak position for the pristine beam.

Results: A significant amount of persistent foci was observed at the distal end of the SOBP, suggesting complex residual DNA double-strand break damage induction corresponding to the highest LET values achievable by modulated proton beams. Unlike the directly irradiated, medium-sharing bystander cells did not show any significant increase in residual foci.

Conclusions: The DNA damage response along the proton beam path was similar to the response of X rays, confirming the low-LET quality of the proton exposure. However, at the distal end of SOBP our data indicate an increased complexity of DNA lesions and slower repair kinetics. A lack of significant induction of 53BP1 foci in the bystander cells suggests a minor role of cell signaling for DNA damage under these conditions.
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http://dx.doi.org/10.1016/j.ijrobp.2015.07.2279DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4840231PMC
May 2016

Relative biological effectiveness variation along monoenergetic and modulated Bragg peaks of a 62-MeV therapeutic proton beam: a preclinical assessment.

Int J Radiat Oncol Biol Phys 2014 Sep 28;90(1):27-35. Epub 2014 Jun 28.

Centre for Cancer Research and Cell Biology, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, Belfast, UK; National Physical Laboratory, Teddington, UK.

Purpose: The biological optimization of proton therapy can be achieved only through a detailed evaluation of relative biological effectiveness (RBE) variations along the full range of the Bragg curve. The clinically used RBE value of 1.1 represents a broad average, which disregards the steep rise of linear energy transfer (LET) at the distal end of the spread-out Bragg peak (SOBP). With particular attention to the key endpoint of cell survival, our work presents a comparative investigation of cell killing RBE variations along monoenergetic (pristine) and modulated (SOBP) beams using human normal and radioresistant cells with the aim to investigate the RBE dependence on LET and intrinsic radiosensitvity.

Methods And Materials: Human fibroblasts (AG01522) and glioma (U87) cells were irradiated at 6 depth positions along pristine and modulated 62-MeV proton beams at the INFN-LNS (Catania, Italy). Cell killing RBE variations were measured using standard clonogenic assays and were further validated using Monte Carlo simulations and the local effect model (LEM).

Results: We observed significant cell killing RBE variations along the proton beam path, particularly in the distal region showing strong dose dependence. Experimental RBE values were in excellent agreement with the LEM predicted values, indicating dose-averaged LET as a suitable predictor of proton biological effectiveness. Data were also used to validate a parameterized RBE model.

Conclusions: The predicted biological dose delivered to a tumor region, based on the variable RBE inferred from the data, varies significantly with respect to the clinically used constant RBE of 1.1. The significant RBE increase at the distal end suggests also a potential to enhance optimization of treatment modalities such as LET painting of hypoxic tumors. The study highlights the limitation of adoption of a constant RBE for proton therapy and suggests approaches for fast implementation of RBE models in treatment planning.
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http://dx.doi.org/10.1016/j.ijrobp.2014.05.010DOI Listing
September 2014

Identification of a BRCA1-mRNA splicing complex required for efficient DNA repair and maintenance of genomic stability.

Mol Cell 2014 May 17;54(3):445-59. Epub 2014 Apr 17.

Centre for Cancer Research and Cell Biology, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK. Electronic address:

Mutations within BRCA1 predispose carriers to a high risk of breast and ovarian cancers. BRCA1 functions to maintain genomic stability through the assembly of multiple protein complexes involved in DNA repair, cell-cycle arrest, and transcriptional regulation. Here, we report the identification of a DNA damage-induced BRCA1 protein complex containing BCLAF1 and other key components of the mRNA-splicing machinery. In response to DNA damage, this complex regulates pre-mRNA splicing of a number of genes involved in DNA damage signaling and repair, thereby promoting the stability of these transcripts/proteins. Further, we show that abrogation of this complex results in sensitivity to DNA damage, defective DNA repair, and genomic instability. Interestingly, mutations in a number of proteins found within this complex have been identified in numerous cancer types. These data suggest that regulation of splicing by the BRCA1-mRNA splicing complex plays an important role in the cellular response to DNA damage.
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http://dx.doi.org/10.1016/j.molcel.2014.03.021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4017265PMC
May 2014

Mechanisms of DNA damage response to targeted irradiation in organotypic 3D skin cultures.

PLoS One 2014 5;9(2):e86092. Epub 2014 Feb 5.

Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, United Kingdom ; National Physical Laboratory, Teddington, London, United Kingdom.

DNA damage (caused by direct cellular exposure and bystander signaling) and the complex pathways involved in its repair are critical events underpinning cellular and tissue response following radiation exposures. There are limited data addressing the dynamics of DNA damage induction and repair in the skin particularly in areas not directly exposed. Here we investigate the mechanisms regulating DNA damage, repair, intracellular signalling and their impact on premature differentiation and development of inflammatory-like response in the irradiated and surrounding areas of a 3D organotypic skin model. Following localized low-LET irradiation (225 kVp X-rays), low levels of 53BP1 foci were observed in the 3D model (3.8±0.28 foci/Gy/cell) with foci persisting and increasing in size up to 48 h post irradiation. In contrast, in cell monolayers 14.2±0.6 foci/Gy/cell and biphasic repair kinetics with repair completed before 24 h was observed. These differences are linked to differences in cellular status with variable level of p21 driving apoptotic signalling in 2D and accelerated differentiation in both the directly irradiated and bystander areas of the 3D model. The signalling pathways utilized by irradiated keratinocytes to induce DNA damage in non-exposed areas of the skin involved the NF-κB transcription factor and its downstream target COX-2.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0086092PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3914781PMC
November 2014

Use of the γ-H2AX assay to investigate DNA repair dynamics following multiple radiation exposures.

PLoS One 2013 29;8(11):e79541. Epub 2013 Nov 29.

Dipartimento di Fisica, Università degli studi di Pavia, Pavia, Italy ; Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia, Italy.

Radiation therapy is one of the most common and effective strategies used to treat cancer. The irradiation is usually performed with a fractionated scheme, where the dose required to kill tumour cells is given in several sessions, spaced by specific time intervals, to allow healthy tissue recovery. In this work, we examined the DNA repair dynamics of cells exposed to radiation delivered in fractions, by assessing the response of histone-2AX (H2AX) phosphorylation (γ-H2AX), a marker of DNA double strand breaks. γ-H2AX foci induction and disappearance were monitored following split dose irradiation experiments in which time interval between exposure and dose were varied. Experimental data have been coupled to an analytical theoretical model, in order to quantify key parameters involved in the foci induction process. Induction of γ-H2AX foci was found to be affected by the initial radiation exposure with a smaller number of foci induced by subsequent exposures. This was compared to chromatin relaxation and cell survival. The time needed for full recovery of γ-H2AX foci induction was quantified (12 hours) and the 1:1 relationship between radiation induced DNA double strand breaks and foci numbers was critically assessed in the multiple irradiation scenarios.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0079541PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3843657PMC
September 2014

A kinetic-based model of radiation-induced intercellular signalling.

PLoS One 2013 22;8(1):e54526. Epub 2013 Jan 22.

Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland, United Kingdom.

It is now widely accepted that intercellular communication can cause significant variations in cellular responses to genotoxic stress. The radiation-induced bystander effect is a prime example of this effect, where cells shielded from radiation exposure see a significant reduction in survival when cultured with irradiated cells. However, there is a lack of robust, quantitative models of this effect which are widely applicable. In this work, we present a novel mathematical model of radiation-induced intercellular signalling which incorporates signal production and response kinetics together with the effects of direct irradiation, and test it against published data sets, including modulated field exposures. This model suggests that these so-called "bystander" effects play a significant role in determining cellular survival, even in directly irradiated populations, meaning that the inclusion of intercellular communication may be essential to produce robust models of radio-biological outcomes in clinically relevant in vivo situations.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0054526PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3551852PMC
July 2013

DNA double strand break repair: a radiation perspective.

Antioxid Redox Signal 2013 Jun 21;18(18):2458-72. Epub 2013 Mar 21.

Centre for Cancer Research & Cell Biology, Queen's University Belfast, Belfast, United Kingdom.

Significance: Ionizing radiation (IR) can induce a wide range of unique deoxyribonucleic acid (DNA) lesions due to the spatiotemporal correlation of the ionization produced. Of these, DNA double strand breaks (DSBs) play a key role. Complex mechanisms and sophisticated pathways are available within cells to restore the integrity and sequence of the damaged DNA molecules.

Recent Advances: Here we review the main aspects of the DNA DSB repair mechanisms with emphasis on the molecular pathways, radiation-induced lesions, and their significance for cellular processes.

Critical Issues: Although the main characteristics and proteins involved in the two DNA DSB repair processes present in eukaryotic cells (homologous recombination and nonhomologous end-joining) are reasonably well established, there are still uncertainties regarding the primary sensing event and their dependency on the complexity, location, and time of the damage. Interactions and overlaps between the different pathways play a critical role in defining the repair efficiency and determining the cellular functional behavior due to unrepaired/miss-repaired DNA lesions. The repair pathways involved in repairing lesions induced by soluble factors released from directly irradiated cells may also differ from the established response mechanisms.

Future Directions: An improved understanding of the molecular pathways involved in sensing and repairing damaged DNA molecules and the role of DSBs is crucial for the development of novel classes of drugs to treat human diseases and to exploit characteristics of IR and alterations in tumor cells for successful radiotherapy applications.
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http://dx.doi.org/10.1089/ars.2012.5151DOI Listing
June 2013