ISCA12 International Symposium on Chromosomal Aberrations
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International Symposium on Chromosomal Aberrations
ISCA12
1989-2019 30 years
Tuesday 27th August 2019
8.30am – 6pm
(Manchester Central Convention Complex, Windmill St, Manchester)
Organised by:
1 Dr Christophe Badie Christophe.badie@phegov.uk
Ms. Roisin McCarron Roisin.McCarron@phe.gov.ukISCA Programme
8.30am - 10.35am Chromosome Aberrations based Biodosimetry Chair: Susan Bailey
8.30: Christophe Badie – Introduction and welcome to ISCA
8.45: Christian Johannes - Radiation-induced chromosomal aberrations and the ISCA meetings
9.05: Yumiko Suto - Radiation cytogenetics in Japan: current state and perspectives
9.20: Adayabalam S. Balajee - Cytogenetic follow-up studies on humans with various exposure scenarios to
ionizing radiation
9.35: Milagrosa López Riego - Biological effectiveness of very high gamma dose rate and its implication for
biological dosimetry
9.45: Farrah Norton - The Automation of γ-H2AX Assay for the Rapid Triage of Biological Dose Estimates in
Large Scale Radiological/Nuclear Events
9.55: Ulrike Kulka - The BALANCE project - High throughput meets networking
10.05: Eric Gregoire - The analysis of complex chromosomal aberrations in case of criticality accident
10.15: Ruth Wilkins - Automated cytokinesis-block micronucleus assay for triage radiation biodosimetry
10.25: Satoshi Tashiro - Chromosomal Abnormalities in Human Lymphocytes after Computed Tomography Scan
Examination
Break: 10.35am – 11.00am
11.00am – 12.55pm High LET Radiation and Chromosome Responses Chair: Ruth Wilkins
11.00: Yun Rose Li - Global genomic landscape of radiation-induced tumours using mouse models of Trp53
deficiency
11.20: George Iliakis - Complex chromosomal aberrations generated by defined clusters of DSBs modelling DNA
lesions induced by high LET radiation
11.35: Rhona M. Anderson - Complex chromosome aberrations as biomarkers of internal exposures
11.50: Carola Hartel - Induction and persistence of chromosome aberrations in human lymphocytes after in vitro
and in vivo exposure to C-ions or photons
12.00: Maria Gomolka - Chromosomal aberrations in former uranium miners – a mFISH study
12.10: Georgia Terzoudi - Chromosomal damage induced by protons, C-ions and alpha-particles in G0-
lymphocytes as analysed by means of the premature chromosome condensation methodology
12.20: Isabella Bastiani - Dose estimation of radium-223 treated patients
12.30: Michael N Cornforth - Single and multi-parameter descriptors of chromosomal response to ionizing
radiation 2Lunch: 12.55pm – 2.00pm
(Including Poster session)
2.00pm – 3.55pm Molecular Mechanisms Chair: Stephen C. West
2.00: Stephen C. West - Unresolved recombination intermediates as a source of DNA breaks and chromosome
aberrations
2.20: Penny A Jeggo - A consideration of the fidelity of DNA double strand break repair
2.35: Serge M. Candéias - Radiation does not impair genetic stability during TCR gene rearrangement in mice
2.50: Antonio Pantelias - Experimental evidence supporting the premature chromosome condensation
hypothesis for chromosome shattering in S-phase micronuclei as the underlying mechanism for
chromothripsis
3.00: Susan M. Bailey - Chromosomal Inversions as Valuable Biodosimeters in Atomic Veterans and Astronauts
3.15: Laure Sabatier - From the quantification of chromosomal rearrangements to the deciphering of underlying
mechanisms
3.30: Marco Durante - Cytosolic DNA is induced by ionizing radiation independently of the formation of
micronuclei
Break: 3.50pm – 4.15pm
4.15pm – 6pm Molecular and Cellular Radiation Cytogenetics Chair: George Iliakis
4.15: Gene Koh - Exploring mutational signatures in human cancers using human cell line models
4.35: Reinhard Ullmann - Chronic exposure to sulphur mustard leads to changes in radiosensitivity, mutational
patterns, chromatin organization and gene expression in the keratinocyte cell line HaCaT
4.45: Yu Abe - Difficulty in dose evaluation following low-dose ionizing radiation exposure by analysing
chromosome aberrations
4.55: Eric Rutten - Extracellular vesicle-mediated bystander effects: Can extracellular vesicles from acute
myeloid cell lines induce DNA damage and chromosomal aberrations in recipient human lymphocytes
5.05: Aashish Soni - Mechanisms of formation of chromosome and chromatid aberrations
5.15: Prakash Hande - Targeting Telomerase and DNA repair in Cancer Therapy
5.25: Radhia M’kacher - DNA breaks, structural chromosomal aberrations, and the dark side of the centromere
5.35: Yanti Lusiyanti - Cytogenetic Effects on Peripheral Blood Lymphocytes in Cancer Patients after Radiation
Therapy: Chromosome Aberrations and Micronuclei
5.45: Honglu Wu - Analysis of biodosimetry data collected from International Space Station crewmembers
5.55: Christophe Badie - close
3Speakers abstracts (A-Z)
Page 5: Yu Abe - Difficulty in dose evaluation following low-dose ionizing radiation exposure by
analyzing chromosome aberrations
Page 6: Rhona M. Anderson - Complex chromosome aberrations as biomarkers of internal exposures.
Page 7: Susan M. Bailey - Chromosomal Inversions as Valuable Biodosimeters in Atomic Veterans and
Astronauts
Page 8: Adayabalam S. Balajee - Cytogenetic follow-up studies on humans with various exposure
scenarios to ionizing radiation
Page 10: Isabella Bastiani - dose estimation of RADIUM-223 treated patients
Page 11: Serge M. Candéias - Radiation does not impair genetic stability during TCR gene
rearrangement in mice.
Page 12: Michael N. Cornforth - Single and multi-parameter descriptors of chromosomal response to
ionizing radiation
Page 13: Marco Durante - Cytosolic DNA is induced by ionizing radiation independently of the
formation of micronuclei
Page 14: Akira Furukawa - Application of artificial intelligence to metaphase finder Presentation
Page 15: Maria Gomolka - Chromosomal aberrations in former uranium miners – a mFISH
study
Page 16: Eric Gregoire - The analysis of complex chromosomal aberrations in case of criticality accident
Page 17: Prakash Hande - Targeting Telomerase and DNA repair in Cancer Therapy
Page 18: Carola Hartel - Induction and persistence of chromosome aberrations in human lymphocytes
after in vitro and in vivo exposure to C-ions or photons
Page 19: George Iliakis - Complex chromosomal aberrations generated by Defined clusters of DSBs
modelling DNA Lesions induced by High LET Radiation
Page 20: Penny A Jeggo - A consideration of the fidelity of DNA double strand break repair
Page 21: Christian Johannes - Radiation-induced chromosomal aberrations and the ISCA meetings
Page 22: Gene Koh - Exploring mutational signatures in human cancers using human cell line models.
Page 23: Ulrike Kulka - The BALANCE project - High throughput meets networking
Page 24: Yun Rose Li - Global genomic landscape of radiation-induced tumors using mouse models of
Trp53 deficiency
4Page 25: Yanti Lusiyanti - Cytogenetic Effects on Peripheral Blood Lymphocytes in Cancer Patients
after Radiation Therapy: Chromosome Aberrations and Micronuclei
Page 26: Radhia M’kacher - DNA breaks, structural chromosomal aberrations, and the dark side of
the centromere
Page 27: Farrah Norton - The Automation of γ-H2AX Assay for the Rapid Triage of Biological Dose
Estimates in Large Scale Radiological/Nuclear Events
Page 28: Antonio Pantelias - Experimental evidence supporting the premature chromosome
condensation hypothesis for chromosome shattering in S-phase micronuclei as the
underlying mechanism for chromothripsis
Page 29: Milagrosa López Riego - Biological effectiveness of very high gamma dose rate and its
implication for biological dosimetry
Page 30: Eric Rutten - Extracellular vesicle-mediated bystander effects: Can extracellular vesicles
from acute myeloid cell lines induce DNA damage and chromosomal aberrations in recipient
human lymphocytes
Page 31: Laure Sabatier - From the quantification of chromosomal rearrangements to the
deciphering of underlying mechanisms
Page 32: Aashish Soni - Homologous recombination repair is more crucial for chromosomal break
repair at low doses of ionizing radiation
Page 33: Yumiko Suto - Radiation cytogenetics in Japan: current state and perspectives
Page 34: Satoshi Tashiro - Chromosomal Abnormalities in Human Lymphocytes after Computed
Tomography Scan Examination
Page 35: GeorgiaTerzoudi - Chromosomal damage induced by protons, C-ions and alpha-particles in
G0 lymphocytes as analysed by means of the premature chromosome condensation
methodology
Page 36: Reinhard Ullmann - Chronic exposure to sulfur mustard leads to changes in radiosensitivity,
mutational patterns, chromatin organization and gene expression in the keratinocyte cell
line HaCaT
Page 37: Stephen C. West - Unresolved recombination intermediates as a source of DNA breaks
and chromosome aberrations
Page 38: Ruth C. Wilkins - Automated cytokinesis-block micronucleus assay for triage radiation
Biodosimetry
Page 39: Honglu Wu - Analysis of biodosimetry data collected from International Space Station
crewmembers
5Difficulty in dose evaluation following low-dose ionizing radiation exposure by analyzing
chromosome aberrations
Yu Abe, Hideyoshi Noji2, Tomisato Miura3, Kurumi Fujioka4, Misaki Sugai1, Yumiko Kurosu5, Risa Ujiie5,
Naohiro Tsuyama1, Aki Yanagi1, Yukari Yanai1, Takashi Ohba6, Tetsuo Ishikawa7, Toshiya Inaba4, Kenji
Kamiya8, Mitsuaki A. Yoshida9, Akia Sakai1
1
Dept. of Radiation Life Sciences, Fukushima Medical University School of Medicine, Fukushima, Japan
2
Dept. of Medical Oncology, Fukushima Medical University School of Medicine, Fukushima, Japan.
3
Dept. of Bioscience and Laboratory Medicine, Hirosaki University Graduate School of Health Sciences,
Hirosaki, Japan. 4Dept. of Molecular Oncology, Research Institute for Radiation Biology and Medicine,
Hiroshima University, Hiroshima, Japan. 5Radiation Medical Science Center for the Fukushima Health
Management Survey, Fukushima Medical University, Fukushima, Japan. 6Dept. of Radiation Health
Management, Fukushima Medical University School of Medicine, Fukushima, Japan. 7Dept. of
Radiation Physics and Chemistry, Fukushima Medical University School of Medicine, Fukushima, Japan.
8
Dept. of Experimental Oncology, Research Institute for Radiation Biology and Medicine, Hiroshima
University, Hiroshima, Japan 9Dept. of Radiation Biology, Institute of Radiation Emergency Medicine,
Hirosaki University, Hirosaki, Japan
abeyu@fmu.ac.jp
Analyzing the frequency of chromosome aberrations (CAs) such as dicentric chromosomes (Dics) and
chromosome translocations (Trs) formation, at the time of radiation exposure (RE) can be used for
biological dosimetry methods. We analyzed the effect of RE from CT examination by examining Dics
and Trs, and we also investigated the cumulative number of CAs induced by three consecutive CT
examinations. Furthermore, we constructed dose-response curves (DRCs) for low- to medium-dose RE
using peripheral blood samples from five healthy individuals. Aliquots were irradiated with one of eight
gamma-ray doses of 1 Gy or less. Analysis of 12 people showed a significant increase in Dics after a
single CT examination (Scientific Rep, 2015), but did not show a significant increase in Trs (J Rad Res,
2016). Subsequently, analysis of eight people who underwent three consecutive CT examinations did
not show a cumulative increase in the frequencies of Dics or Trs (AACR, 2018). Also in the above
analyses, the frequency of Trs was higher than that of Dics regardless of CT examination. DRCs showed
a large variation between individuals in the frequency of Dics, and the slopes of the DRCs were
different in Dics analysis. Although variation was observed in the frequency of Trs, the slopes of the
DRCs were similar after adjusting for age. We observed a good correlation between the irradiation
dose and the frequency of CAs (J Rad Res, 2018). Therefore, a significant change in Trs following low-
dose RE may not be apparent, and construction universal DRCs may be difficult.
6Complex chromosome aberrations as biomarkers of internal exposures.
Rhona M. Anderson
Centre for Health Effects of Radiological and Chemical Agents, Institute of Environment, Health and
Societies, College of Health and Life Sciences, Brunel University London, Uxbridge, UK.
rhona.anderson@brunel.ac.uk
We have shown previously that human peripheral blood lymphocytes (PBL), bone marrow
mononuclear cells (BM), and CD34+ cells irradiated in vitro with a fluence of 1 high-linear energy
transfer (LET) -particle/nucleus show characteristic complex chromosome aberrations (CCA) in their
1st cell division post exposure and that a small, but measurable proportion of these will be capable of
long-term transmission. We have also shown this characteristic feature of -particle exposure to be
detectable in spherical cells irrespective of the incident LET and, the occurrence of newly arising de
novo aberrations in cells carrying clonal CCA suggesting ongoing genomic instability in these
populations. CCA are also known to be induced after exposure to low-LET X-rays, however this effect
is strongly dependent upon dose with appreciable frequencies only being detected at doses >1 Gy.
Accordingly, the detection of CCA have been proposed as useful indicators of high-LET exposure
particularly where mixed exposure or internalised contamination is suspected. We are currently
assessing this in a number of exposed and potentially exposed human populations by quantifying the
frequency, complexity and stability of chromosome aberration detected in PBL using a variety of
cytogenetic techniques and, by determining the long-term transmissibility of the damaged cells. The
potential for and challenges of using this cytogenetic data for peripheral blood and bone marrow dose
estimation and, for the evaluation of health risks associated with -particle exposure will be discussed.
7Chromosomal Inversions as Valuable Biodosimeters in Atomic Veterans and Astronauts
Susan M. Bailey1, 3 Miles J. McKennaJared1, 3 Luxton1, Erin Robinson 3, Lynn Taylor, Kerry George4,
Steven L. Simon5, Michael N. Cornforth6,3
1
Cell and Molecular Biology Program, and 2Department of Environmental and Radiological
Health Sciences, Colorado State University, Fort Collins, CO USA 3KromaTiD, Inc., Fort Collins, CO USA
4
KBRwyle, Houston, TX, USA 5Division of Cancer Epidemiology and Genetics, National Cancer Institute,
National Institutes of Health, Bethesda, MD USA 6Department of Radiation Oncology, University of
Texas Medical Branch, Galveston, TX USA
susan.bailey@colostate.edu
Large-scale structural rearrangements within the genome such as chromosomal translocations,
deletions, duplications and other copy number variants (CNVs), are known to figure prominently in
various human diseases, including cancer and neurological or developmental disorders. However, a
full appreciation of the contribution of chromosomal inversions – a reversal of orientation of material
within a chromosome – is still very limited. In principle there is no reason to believe that inversions
are inherently any less frequent, or harmful, than other structural variations, suggesting that there are
many more disease associated inversions yet to be discovered. Classical cytogenetic techniques are
capable of detecting only relatively large inversions that noticeably alter banding patterns; inversions
also remain relatively invisible to NextGen sequencing approaches, due to the presence of regions
that are refractory to analysis, and issues associated with heterogeneity across cell populations. Thus,
a paucity of methods for global, unbiased inversion discovery has restricted our overall view of the
frequency of such rearrangements, their size distribution, and the extent to which they are associated
with human disorders. Here, we demonstrate the utility of a novel approach called directional
genomic hybridization (dGH), a cytogenomics-based strand-specific methodology, for the purpose of
high-resolution inversion detection and discovery following a variety of human radiation exposure
scenarios. Furthermore, dGH single-stranded chromosome paints can be combined with telomere or
sub-telomere probes to improve discrimination of terminal inversion vs. sister chromatid exchange,
two very distinct processes that are often difficult to definitively distinguish cytologically, especially
when such rearrangements occur near chromosomal termini.
8Cytogenetic follow-up studies on humans with various exposure scenarios to ionizing radiation
Adayabalam S. Balajee
Radiation Emergency Assistance Center/Training Site*, Cytogenetic Biodosimetry Laboratory, Oak
Ridge Institute for Science and Education, Oak Ridge Associated Universities, Oak Ridge, USA.
Adayabalam.balajee@orau.org
Occupational, incidental and accidental exposures to ionizing radiation inflict a wide spectrum of DNA
lesions in the cells of various tissues/organs in humans. Among the lesions, DNA double strand break
is the most deleterious lesion, which when mis-rejoined leads to stable and unstable chromosomal
aberrations. Chromosomal aberrations are often used for estimating a person’s absorbed radiation
dose since their formation is dependent on radiation quality, dose and dose rate. Besides estimating
absorbed radiation dose, cytogenetic analysis can be effectively utilized for long-term monitoring of
stochastic health effects in radiation exposed victims since chromosomal aberrations are indicators of
genomic instability. At the REAC/TS CBL, we have been doing cytogenetic follow-up studies spanning
from 5 to 50 years on some of the radiation victims with various modes of exposure: (I) internal
radioiodine exposure, (II) diagnostic over exposure with X-rays during fluoroscopy procedure, (III)
uranium blast exposure during the Y12 criticality accident in Oak Ridge and (IV) accidental external -
rays exposure to workers in an industrial sterilization unit. A wide variety of cytogenetic assays
including multicolor fluorescence in situ hybridization (mFISH) and chromosome specific multicolor
BAND have been utilized to analyze both stable and unstable chromosome aberrations. Long-term
persistence of chromosomal aberrations observed in these cases seems to depend on radiation quality
and exposure mode. Molecular mechanisms for the persistence of simple and complex chromosome
translocations and their potential impact on stochastic effects in the exposed victims will be discussed.
9Dose estimation of radium-223 treated patients Isabella Bastiani[1] , Liz Ainsbury[2] , Joe O’Sullivan [3], Kevin Prise [3] Philip Turner [3], Rhona Anderson[1] 1 Centre for Health Effects of Radiological and Chemical Agents, College of Health and Life Science, Brunel University London, Kingston Lane, Uxbridge, London UB8 3PH 2 Centre For Radiation, Chemical & Enviromental Hazards, Public Health England, Didcot OX11 0RQ 3 Centre for Cancer Research and Cell Biology, Queen’s University Belfast, Belfast Isabella.Bastiani@brunel.ac.uk Radium-223 (223Ra) is a radiopharmaceutical that delivers high-linear energy transfer -particles to regions of bone metastatic disease. -particles have a range of
Radiation does not impair genetic stability during TCR gene rearrangement in mice.
Serge M. Candéias
Interdisciplinary Research Institute – Grenoble, Laboratory of Chemistry and Biology of Metals, UMR
5249 CEA-CNRS-UGA, 38054 Grenoble – France
serge.candeias@cea.fr
Chromosomal translocation may result from a deficient control/function of the ATM-dependent DNA
damage response checkpoint. To determine whether low dose radiation-induced genetic instability
may result from radiation-induced inactivation of this pathway, we analysed the faithfulness of T cell
receptor (TR) gene rearrangement by V(D)J recombination in mice exposed to a single dose of X-ray
radiation and in mice chronically exposed to low dose rate radiation. Mice were exposed to low (0.1
to 0.2 Gy) or intermediate (1 Gy) doses of radiation either by acute exposure to X-rays or 3 weeks
exposure to low dose -radiation. Illegitimate TR gene rearrangements were amplified by PCR from
DNA prepared from the blood and the thymus of these mice, respectively. Radiation exposure did not
increase the onset of TR gene trans-rearrangements in irradiated mice and, in mice where it happened,
trans-rearrangements remained sporadic events in developing T lymphocytes. Therefore, low
dose/low dose rate ionizing radiation exposure does not result in a widespread inactivation of the
ATM-dependent mechanisms, and the mechanisms enforcing genetic stability are not impaired by
ionizing radiation in developing lymphocytes and lymphocyte progenitors, including BM-derived
hematopoietic stem cells, in low dose exposed mice.
11Single and multi-parameter descriptors of chromosomal response to ionizing radiation
M.N. Cornforth
University of Texas Medical Branch, Department of Radiation Oncology, Galveston TX 77555-1084,
USA
mcornfor@UTMB.EDU
Virtually all biological phenomena associated with the exposure to ionizing radiations are mirrored by
changes observable at the cytogenetic level. These include the effects of total absorbed dose, dose
rate, and radiation quality. Typically, quantitative measures of these effects have the undesirable
property of dose-dependency, which can be circumvented by appeal to the concepts embodied by
mean inactivation dose. Metrics designed to provide LET-dependent “cytogenetic signatures” have
been employed with moderate degrees of success. Alternative approaches are discussed in an effort
to stimulate discourse surrounding the topic of radiation-induced chromosome damage.
12Cytosolic DNA is induced by ionizing radiation independently of the formation of micronuclei
M. Durante[1] , A.Helm[2] , M. Schork[2] , G. Taucher-Scholz[2] , B. Jakob[2] , C. Fournier[2] , N. Averbeck[2]
[1]
GSI Helmholtz Center for Heavy Ion Research, Darmstadt, Germany
Technical University of Darmstadt, Department of Condensed Matter Physics, Darmstadt, Germany;
m.durante@gsi.de
[2]
GSI Helmholtz Center for Heavy Ion Research, Darmstadt, Germany;
m.durante@gsi.de
Micronuclei (MN) are observed in the cytoplasm of mammalian cells following exposure to clastogenic
agents. MN contain chromosomal fragments derived by asymmetrical inter- or intra-changes, or whole
chromosomes. Recently, it has been shown that MN can release DNA to the cytosol, thus triggering
the cGAS-STING pathway that eventually leads to production of IFN- and immune response. This
pathway may be exploited in cancer treatment combining radiotherapy and immunotherapy.
We have quantified cytosolic DNA in mouse 4T1 mammary carcinoma cells at 24 h following exposure
to X-rays or accelerated carbon ions. Irradiated cells experienced a dose-dependent G2-block,
measured by flow cytometry. Immunofluorescence staining of dsDNA revealed an increased fraction
of cytosolic DNA in pre-mitotic cells upon irradiation. The relative number of cytosolic DNA foci
increased with dose up to values as high as 20 Gy. On the other hand, MN per irradiated cell decreased
at high doses, as a consequence of the interphase block. The morphology of the interphase cells that
do not proceed in the cell cycle is compatible with necroptosis. We conclude that, at 24 h after
irradiation, ionizing radiation can induce cytosolic DNA independently of the induction of MN.
13Application of artificial intelligence to metaphase finder Presentation
Akira Furukawa
National Institutes for Quantum and Radiological Science and Technology, Japan
furukawa.akira@qst.go.jp
Biological dosimetry is used to estimate individual absorbed radiation dose by quantifying an
appropriate biological marker. The most popular gold-standard marker is the appearance of dicentric
chromosomes in metaphase. The metaphase finder is a tool for automation of biological dosimetry
that finds metaphase cells on glass slides. The author and a software company have designed a new
system and are now preparing to produce the system commercially. This system was capable of
identifying not only normal chromosomes but also PCC cells. The metaphase finder consists of an
automated microscope, an auto-focus system, an X–Y stage, a camera, and a computer.
To enhance the accuracy of the system, an artificial intelligence (AI) with deep learning was tested.
The pre-selection of metaphases using mathematical morphology before the AI process was enabled
the AI classification of true metaphases or not. A total of 1709 images of the metaphase finder
detected as ‘metaphases’ were read into a nine-layer artificial neural network to detect true
metaphases. A total of 456 images were used for training, and the rest of the images were used for
validation. The accuracy of AI was 0.89 for metaphases and 0.90 for non-metaphases.
Now, implementation of the AI to the metaphase finder is progressing.
14Chromosomal aberrations in former uranium miners – a mFISH study
Maria Gomolka1, Susanne Schmeißer1, David Endesfelder2, Ute Roessler1, Ursula Oestreicher2, Ulrike
Kulka1,2, Sabine Hornhardt1 and Martin Bucher1
1
Section Radiation Biology, Federal Office for Radiation Protection, Neuherberg, Germany 2Section
Biological Dosimetry, Federal Office for Radiation Protection, Neuherberg, Germany
mgomolka@bfs.de
Aim of this project is to analyse internal (mainly radon) and external (mainly gamma-rays) past
exposure changes on chromosomal aberrations in blood of former uranium miners. We questioned if
individual high- and low-LET mixed exposure effects, even 40 years after the miners stopped working,
result in an increased aberration frequency as detected by multicolour fluorescence in situ
hybridisation (mFISH).
Blood samples of the German Uranium Miners Biobank were selected, including data on age, smoking,
medical history, fine dust and arsenic. Radon exposure ranged from 3 to 2479 WLM and doses for the
red bone marrow from 0.2 to 600 mGy. Data from 67 miners were included in the evaluation, in total
more than 17.000 cells. Significant correlations between exposure and chromosomal damage were
observed for the parameters aberrant cells (r= 0.28 [0.04, 0.5]; p=0.025) and total breaks in analysed
cells (r=0.25 [0, 0.47]; p=0.046). Significant correlations with these two parameters were observed for
radon exposure (mainly affecting the lung) but organ dose of the red bone marrow showed the highest
correlation. Positive although not significant correlations were detected for complex aberrations and
translocations. One individual who underwent radiation therapy 4 years ago showed a remarkable high
score in all aberration parameters.
Even several decades after occupational uranium exposure, chromosomal aberrations are increased in
dependence of the received doses. Clearly, individual dose assessment is difficult, but results are
valuable to support the validity of the job-exposure matrix and to exclude individuals from
occupational radiation risk assessment that received medical radiation doses.
15The analysis of complex chromosomal aberrations in case of criticality accident
E. Gregoire3, H. Shen1, JF Barquinero2, G. Gruel3, F. Trompier
1
Singapore Nuclear Research and Safety initiative; Singapore, 2University Autonoma of Barcelone;
Spain, 3Institut de Radioprotection et de Sureté Nucléaire, France
eric.gregoire@irsn.fr
Background
A key element for the evaluation of the risks associated with an exposure to ionizing radiation is an
accurate estimation of the absorbed dose. However, depending on the radiation quality, a given
absorbed dose could lead to the level DNA damage it can cause. A criticality accident could lead to
people exposures to neutrons, and could challenge the accuracy of the biological dose reconstruction
based on chromosome aberrations (CA).
Aims
Nowadays, the analysis of CA is considered the most robust biological indicator of these effects as the
complexity of CA can be correlated to the radiation quality.
Methods
To evaluate the level of CA complexity in case of neutron exposure, we performed exposure of human
blood samples to neutron fields (Caliban reactor; CEA Valduc, France) similar to those generated
during this kind of accident. The comparison of CA complexity have been achieved using Multicolor
fluorescence in situ hybridization (M-FISH) of chromosome spreads obtained from blood samples
exposed to 3 different radiation conditions: neutron field with a constant dose rate, pulsed neutron
field and 4 MV X-rays (LINAC; IRSN, France) of same dose.
Results
As expected, more complex aberrations were observed in the peripheral lymphocytes exposed to
neutrons compared to X-rays. The number of breaks per cell between X-ray and neutron exposure is
significantly different. In addition, we observed the increase of the level complexity of CA for neutron
exposure. Interestingly, we have also measured a higher rate of unrepaired chromosomal fragments,
leading to the hypothesis of a delay or impairment in DNA damage repair processes in this case.
16Targeting Telomerase and DNA repair in Cancer Therapy
Prakash Hande
Department of Physiology, Yong Loo Lin School of Medicine and Tembusu College, National University
of Singapore, Singapore.
phsmph@nus.edu.sg
Telomeres play a critical and opposing role in the process of carcinogenesis, serving as an obstacle e
during early stages of cell transformation and later a cancer hallmark for unlimited cell proliferation. .
Reactivation of telomerase is essential for telomere maintenance in human cancer cells ensuring
indefinite proliferation. Targeting telomere homeostasis has become one of the promising strategies
in the therapeutic management of tumours. We have recently shown that inhibition of DNA repair
factors and telomerase renders cells more sensitive to DNA damaging agents. In addition to inducing
telomere dysfunction, inhibition of telomerase decreased tumour cell viability, induced cell cycle arrest
and DNA damage. The observed therapeutic potential in the cancer cells improved when they were
combined with the inhibition of certain selective DNA repair factors and/or radiation. Interestingly,
telomerase inhibitors impede the cell survival and proliferative ability to a greater extent in
telomerase-positive cells as compared to alternative lengthening of telomeres-positive cells both in
acute and chronic treatments. In addition, our in vitro studies suggest that inhibition of DNA repair
pathways and that of telomerase could sensitise cancer cells to radiation and enhance anti-tumour
effects.
17Induction and persistence of chromosome aberrations in human lymphocytes after in vitro and in
vivo exposure to C-ions or photons
C. Hartel1, E. Nasonova12, M. Fuss1 J. Debus3 M. Durante14 S. Ritter1
1
GSI Helmholtz Center for Heavy Ion Research, Darmstadt, Germany;
2
Joint Institute for Nuclear Research (JINR), Laboratory of Radiation Biology, Dubna, Russia;
3
Heidelberg University Hospital, Department of Radiation Oncology Heidelberg, Germany;
4
Technical University of Darmstadt, Department of Condensed Matter Physics, Darmstadt,
c.hartel@gsi.de
Chromosome aberrations in lymphocytes are a predictive biomarker for cancer risk. In the present
study we compare the cytogenetic effects of high LET C-ions that are increasingly used for cancer
therapy with the effects of conventional low LET photons.
Aberrations were analyzed at different time-points in lymphocytes of prostate cancer patients treated
with C-ion boost + IMRT or IMRT alone. Additionally, in vitro dose-effect curves were generated for C-
ions of different energies and X-rays. Analyses were performed by full-genome painting (m-FISH).
In vitro, C-ions were more effective than X-rays in inducing cytogenetic damage resulting in a high RBE
that increases with LET. Moreover, the ratio of complex to simple exchanges (C-ratio) was elevated. In
patients, the yield of aberrations after C-ion boost was lower than after a comparable dose of IMRT
reflecting the lower integral normal tissue dose. Moreover, the C-ratio was not significantly elevated
in vivo. A 3-year follow-up of patients revealed a significant decrease in the yield of non-transmissible
aberrations, while the yield of transmissible aberrations (translocations) persisted, pointing to the
exposure of hematopoietic stem/progenitor cells.
In summary, in vitro, C-ions induced more aberrations and a higher frequency of complex aberrations
than X-rays. In vivo, C-ions induced fewer aberrations than photons. We explain this difference by the
lymphocytes (representing normal tissue) being mainly exposed to low LET C-ions during therapy (in
the entrance channel), while high LET C-ions are directed to the tumor volume.
18Complex chromosomal aberrations generated by defined clusters of DSBs modelling DNA lesions
induced by high LET radiation
George Iliakis, Veronika Mladenova, Simon Magin, Emil Mladenov
Institute of Medical Radiation Biology, University of Duisburg-Essen Medical School, 45122 Essen,
Germany
Georg.Iliakis@uk-essen.de
DNA double-strand-break (DSB) complexity is invoked to explain the increased efficacy of high LET
radiation and is usually defined as presence of additional lesions in the immediate proximity of the
break. DSB-clusters represent a different level of complexity that jeopardizes DSB processing in the
vicinity of the cluster by destabilizing chromatin. DSB-clusters are generated after exposure of cells to
ionizing radiation (IR), particularly high LET radiation, and have been considered as particularly
consequential in several mathematical models of IR action. We have previously shown that clusters of
DSBs generated by the I-SceI meganuclease at multiple, appropriately engineered genomic sites,
compromise c-NHEJ and markedly increase cell killing and translocation-formation compared to single-
DSBs; such translocations require Parp1 activity, which implicates alt-EJ in their formation.
Chromosome translocations cause cell killing and cancer through the joining of incongruent DNA-ends
that alter the genome. Many aspects of translocation-formation, including DSB repair-pathway choice
and permissive chromatin conditions remain incompletely characterized. Here we utilize our I-SceI-
based CHO model system to study formation of chromosome aberrations using multicolor
fluorescence in situ hybridization (M-FISH) and long-read Nanopore sequencing. M-FISH analysis of
CHO clones carrying single, paired or quadruple I-SceI sites at 24, 30 or 48 h after transfection with an
I-SceI expression vector confirms that DSB-clusters are more likely to generate chromosome
aberrations than single DSBs. The elevated resolution of M-FISH analysis allows the identification of
reciprocal chromosomal translocations that remain undetectable by standard Giemsa staining. The
number of translocations for each clone reaches its maximum 24 h after transfection and decreases
slightly at later times. Interestingly, with progressing time we observe a shift in the ratio between
chromatid- and chromosome-type aberrations. Our results demonstrate further that with increasing
clustering of DSBs the incidence of complex chromosomal rearrangements, as well as the incidence of
diverse numerical changes (polyploidy, etc.) are also increased. Furthermore, M-FISH analysis allows
the quantification of translocation formation in individual chromosomes. The information obtained
from M-FISH together with the knowledge of the exact positions of the integrated I-SceI recognition
sites within the CHO genome garnered from Nanopore sequencing on the MinION platform (Oxford
Nanopore Technologies) will be useful in the description and/or prediction of chromosomal
translocations. Our observations contribute to the mechanistic explanation for the increased efficacy
of high LET radiation and will be discussed vis-à-vis the latest results on DSB processing.
19A consideration of the fidelity of DNA double strand break repair
Penny A Jeggo
Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Brighton, U.K
p.a.jeggo@sussex.ac.uk
Canonical DNA non-homologous end-joining (c-NHEJ) and Homologous Recombination (HR) represent
the major DNA double break repair (DSB) pathways. ATM signalling also influences DSB repair by
regulating chromatin structure. I will consider factors influencing the fidelity of DSB repair in G1 and
G2 phase.
In G0/G1, c-NHEJ effects repair with two-component kinetics; 85% of DSBs are repaired with fast
kinetics whilst the remainder are rejoined more slowly. The slow process additionally requires
nucleases and susceptible to translocations. In G2, the slow process represents HR. DSBs repaired by
HR include those within transcriptionally active (TA) regions as well as DSBs repaired with slow kinetics
in G1. Nonetheless, in G2, most DSBs in non-cancer cells are repaired by c-NHEJ with fast kinetics.
Since c-NHEJ does not necessitate junctional homology, translocations or large deletions
(intrachromosomal translocations) can arise if synapsis is lost. Classical chromosomal studies using G1
cells and procedures causing premature chromosome condensation have revealed that translocations
arise with dose-squared kinetics via c-NHEJ, and can generate interstitial fragments. These derived
DSBs significantly contribute to lethality. Dose splitting in G0/G1 “spares” translocations and enhances
survival. I will discuss recent data showing that “sparing” also arises in G2 cells, likely due to c-NHEJ
usage in G2. A critical question is whether there are additional mechanisms to limit translocations
arising from c-NHEJ such as ATM-dependent chromatin changes, the nature of the c-NHEJ process (ie
the use of a nuclease-independent process) or processes to arrest transcription in the DSB vicinity.
These considerations will be discussed.
20Radiation-induced chromosomal aberrations and the ISCA meetings
Christian Johannes2, Andrzej Wojcik 1
1
Stockholm University, Sweden, 2University Duisburg-Essen, Essen, Germany
christian.johannes@uni-due.de
Since the birth of modern genetics at the beginning of the 20th century, chromosomal aberrations
stood in the focus of research because they represented an elegant method of visualising DNA damage.
Because ionising radiation is a potent inducer of chromosomal aberrations, the chromosomal
aberration test quickly became, and still remains today, an established method of quantifying
radiation-induced DNA damage. It is also widely used in chemical toxicology.
The chromosomal aberration test lived through many modifications and expansions. It started with
the analysis of Giemsa-stained structural changes in giant chromosomes of Drosophila melanogaster
and plant pollen and root meristem cells. Following the development of harvesting methods of human
cells it was expanded by the various banding techniques, premature chromosome condensation,
cytogenesis-blocked micronucleus assay, and fluorescence in situ hybridisation. The development of
computers with sufficient power and of image analysis techniques allows quantifying chromosomal
damage in a fully-, or semi-automated way.
The International Symposium on Chromosomal Aberrations (ISCA) series started in 1989 in Essen, as
the initiative of Günter Obe and Adayapalam T. Natarajan. It took place approximately every three
years, initially in Essen, then two times in Japan, to be loosely attached to meetings of the European
Radiation Research Society (ERR). The latest 11th ISCA meeting took place during the ERR 2014 on
Rhodes. The programs of the meetings give an interesting historical reflection of the development of
the field.
A short review will be given of the developments in radiation cytogenetics as they were discussed
during the ISCA meetings.
21Exploring mutational signatures in human cancers using human cell line models.
Gene Koh
gk11@sanger.ac.uk
Welcome Trust, Sanger Centre, Cambridge, U.K
A cancer genome carries the historic mutagenic activity that has occurred throughout the
development of a tumour. While driver mutations were the main focus of cancer research for a long
time, passenger mutational signatures – the imprints of DNA damage and DNA repair processes that
have been operative during tumorigenesis – are also biologically informative. In this talk, I shall
provide a synopsis of this concept and describe the insights that we have gained through experiments
in cell-based systems.
22The BALANCE project - High throughput meets networking
Ulrike Kulka1, Guy Garty2, Ulrich Giesen3, Elizabeth Ainsbury4, Leonardo Barrios Sanromá5, Joan
Francesc Barquinero5, Christina Beinke6, David Endesfelder1, Eric Grégoire7, Gaëtan Gruel7 , Valeria
Hadjidekova8, Andrew Harken2, Mercedes Moreno Domene9, Jayne Moquet4, Ursula Oestreicher1,
María Jesús Prieto9, Mikhail Repin2, Ekaterina Royba2, Anne Vral10, Demetre Zafiropoulos11, Andrzej
Wojcik12
1
BfS Federal Office for Radiation Protection, Oberschleissheim, Germany, 2CU Columbia University,
New York, US, 3PTB Physikalisch-Technische Bundesanstalt, Braunschweig, Germany, 4PHE Public
Health CRCE, Chilton, Didcot, Oxon, United Kingdom, 5UAB Universitat Autonoma de Barcelona,
Bellaterra, Spain, 6BIR Bundeswehr Institute of Radiobiology affiliated to the University of Ulm, Munich,
Germany, 7IRSN Institut de Radioprotection et de Sûreté Nucléaire, Fontenay-aux-Roses, France,
8
NCRRP National Center for Radiobiology and Radiation Protection, Bulgaria, 9SERMAS Servicio
Madrileño de Salud - Hospital General Universitario Gregorio Marañón, Madrid, Spain, 10UGent Ghent
University, Dept. Human Structure and Repair, Radiobiology Research Unit, Gent, Belgium, 11INFN
Laboratori Nazionali di Legnaro, Legnaro, Italy, 12SU Stockholm University - The Wenner-Gren Institute,
Stockholm, Sweden
ukulka@bfs.de
Background: In case of a malevolent nuclear event a large number of persons might be exposed to
ionizing radiation. In such cases a trustworthy classification of individuals according to their degree of
exposure is needed. On the long term, a biomonitoring of affected persons or person groups is
required to identify long-term consequences of radiological disasters and to assign these to individual
received radiation doses.
Aims: Within the BALANCE project, two different approaches to handle large-scale individual
retrospective dose estimations based on cytogenetic markers are compared, automated high
throughput analysis and networking between laboratories. Specific aims are 1) to establish appropriate
dose effect curves for cytogenetic biomarkers in blood lymphocytes exposed to neutrons from two
different neutron sources, 2) to enhance the performance capacity by combining existing analysis
strategies such as high throughput analysis and networking of biodosimetry laboratories and 3) to
identify critical points in the current approaches and develop a strategy how to overcome them.
Methods: The rapid automated biodosimetry tool “RABiT” is used for completely automated high
throughput processing of blood samples and dose estimates with minimal need of manpower.
Complementary to this, the network approach with distribution of blood samples between different
laboratories for conventional processing is performed.
Key results: Experiences from the establishment of dose effect curves, which allow a robust
retrospective dose estimation for the provisional classification of possibly affected persons and also
for a long-term monitoring of population groups are presented.
Conclusion: Both approaches have advantages and risks, depending on the particular situation.
23Global genomic landscape of radiation-induced tumors using mouse models of Trp53 deficiency
Yun Rose Li1,2, Kyle Halliwill1, Cassandra Adams1, Vivek Iyer2, David Adams3, Allan Balmain1
1
Helen Diller Family Comprehensive Cancer Center, University of California San Francisco, San
Francisco, CA 94109, 2Department of Radiation Oncology, University of California San Francisco, San
Francisco, CA 94109, 3Wellcome Trust Sanger Center, Cambridge, UK
yunroseli@gmail.com
Ionizing radiation (IR) is both a potent mutagen and an important forms of cancer therapy. While its
mechanism of action is not clearly elucidated, IR is thought to act by inducing DNA damage through a
combination of direct (double-strand breaks) and indirect mechanisms (oxidative stress) and its
relative potency is related to the function of tumor suppressors, particularly Trp53. To explore the
impact of IR on the evolution and landscape of the cancer genome and the impact of Trp53 deficiency,
we subjected two mouse models of Trp53 dysfunction (n=214): heterozygous loss (het) and
homozygous delta proline region deletion (delP) to either a single 50cGy dose of gamma or high-LET
(Fe-ion) radiation. We employed whole genome (WGS) and/or exome sequencing (WES) to examine
over 70 IR-related tumors and identified characteristics specific to IR quality, Trp53 genotype, and
tumor histology/site.
We found that radiation quality affected tumor latency (disease-free survival), tumor type (carcinoma,
lymphoma or sarcoma), and patterns of genomic aberrations. Fe-ion exposure is strongly associated
with large focal deletions and structural rearrangements, supporting a mechanism of direct DNA
damage. Germline Trp53 status, specifically tumors from animals with Trp53 het genotype were
enriched for non-focal rearrangements and aneuploidy compared to mice with the delP allele.
Examining global SNV and INDEL variants identified both known and novel mutation signatures,
including SNV signature 18, which has been associated with inflammation and oxidative stress and
was identified in nearly all samples. In addition, in a subset of samples, we identified a de novo SNV
and INDEL signature strongly attributed to focal regions of high mutation rate, resembling a
phenomenon of “focal” chromothripsis. Finally, we identified somatic mutations in well-known driver
genes including Kras, Apc, and Trp53. Our study provides compelling evidence in support of both a
role for direct and indirect DNA damage, identifies focal and whole chromosomal chromothripsis, and
illustrates complex interaction of Trp53 deficiency and radiation quality in the landscape of IR-
mediated tumors.
24Cytogenetic Effects on Peripheral Blood Lymphocytes in Cancer Patients after Radiation Therapy:
Chromosome Aberrations and Micronuclei
Yanti Lusiyanti1, Nastiti Rahajeng1, Sofiati Purnami1 ,Vyria As1, and Lina Choridah3
1
Center for Technology of Safety and Radiation Metrology, National Nuclear Energy Agency of
Indonesia, Jakarta, 2Department of Radiology, dr. Sardjito General Hospital, Yogyakarta, Indonesia
k_lusiyanti@batan.go.id
A preliminary evaluation on the cytogenetic biomarker on patient was done. The aim of the study
was to evaluation the individual response sensitivity of different type of cancer patients after radiation
therapy. Peripheral blood lymphocytes obtained from 11 patients that grouped to three different
cancer, breast, head and neck and extremity cancer, with range doses 10-14 Gy. Blood sample were
stimulated in vitro by phytohaemagglutinin (PHA), the cultures were processed for the dicentric and
CBMN assay and to compare the two methods. The results show that the DC assays and CBMN assay
are equivalent. The overall DC and CB MN showed significantly higher frequency in breast and head
and neck compared to extremity cancer. For further investigations, we prefer the CBMN assay,
because it is simpler through easy scoring criteria, allows high numbers of cell counts in sensitive, and
has higher statistical power. In the future, we plan to integrate cytogenetic damage during
radiochemotherapy to predict response and patient’s radiotoxicity.
25DNA breaks, structural chromosomal aberrations, and the dark side of the centromere
Radhia M’kacher1, Bruno Colicchio2, Steffen Junker3, Olivier Cariou4, Valentine Marquet5, Marguerite
Miguet6, Leonhard Heidingsfelder7, Kevin Soehnlen1, Wala Najar1-8, William M. Hempel1, Alain
Dieterlen2, Theodore Girinsky9, Catherine Yardin5, Philippe Voisin1, Patrice Carde10, Eric Jeandidier6
1
Cell Environment, DNA damage R&D, Paris, France 2IRIMAS, Institut de Recherche en Informatique,
Mathématiques, Automatique et Signal, Université de Haute-Alsace, Mulhouse 68093 France
3
Institute of Biomedicine, University of Aarhus, DK-8000 Aarhus, Denmark 4Genevolution laboratory,
78265 Porcheville, France 5Service de Cytogénétique, Génétique Médicale, et Biologie de la
Reproduction Hôpital de la Mère et de l’Enfant, CHU Dupuytren, 87042 LIMOGES, France 6Service de
génétique Groupe Hospitalier de la Région de Mulhouse et Sud Alsace Mulhouse, France 7MetaSystems
GmbH, Robert-Bosch-Str. 6 D-68804. Altlussheim, Germany, 8 Faculté de Médecine, Université Paris
Descartes 75006 Paris, France 9Department of radiation therapy, Gustave Roussy cancer campus 94808
Villeuif, France 10Department of medicine, Gustave Roussy cancer campus, Villejuif, France
radhia.mkacher@cell-environment.com
Purpose: We used a combined approach involving telomere and centromere (TC) staining with M-FISH
to reevaluate the frequency of dicentric chromosomes (DC) and compare it to the frequency of
translocations. We have also assessed the involvement of each chromosome in the rearrangements,
and the nature of breakpoints.
Materials and methods: This study was performed on blood lymphocytes from eight healthy donors
exposed to in vitro irradiation, from 50 hematological cancer patients, and 50 from congenital cases.
Chromosomal aberrations were scored by sequential analysis using TC staining followed by M-FISH.
Results: We demonstrate, the equal frequency of formation of in vitro induced DC and translocations
(44% vs 43%). Interestingly, 71.7% of the breakpoints involved in the formation of DC were localized
in pericentromeric (42.8%) and telomeric (28.8%) regions. In contrast, 60% of the breakpoints involved
in the formation of translocations were localized within the whole-arm. The involvement of the
chromosomes in the rearrangements was not related to their size. Chromosomes 17, 20, 22, 16, and
19 were the most highly involved. Analysis in cancer patients demonstrated the presence of DC in
28/50 patients and a high frequency (> 70%) of specific DC configurations, with both centromeres in
close proximity to each other and with the loss of 17p (TP53). In congenital cases, 85% of the
breakpoints were localized in the pericentromeric regions. Pericentromeric breakpoints were also
associated with a high degree of chromosomal instability.
Conclusion: This study shows the importance of pericentromeric breakpoints for the viability and
transmission of chromosomal aberrations.
26The Automation of γ-H2AX Assay for the Rapid Triage of Biological Dose Estimates in Large Scale
Radiological/Nuclear Events
Farrah Norton1, Connor Davis2 and Stephen Pecoskie3
Canadian Nuclear Laboratories, Chalk River, ON, K0J 1J0, Canada
farrah.norton@cnl.ca
Biological Dosimetry plays a key role in the medical management of patients for treatment following
an accidental radiation exposure. In the case of a mass casualty radiological or nuclear incident where
hundreds to thousands of people would require biological dose assessment, rapid triage of these
patients will be of utmost importance to produce dose assessment as quickly as possible.
In the hours to days post-event, dose estimation can be made quickly by using the H2AX
phosphorylation assay (γH2AX). The kinetics of the γH2AX response to radiation damage is well
documented and visible from minutes to three days post exposure, reaching a maximum signal at one
to two hours (1). There are currently two well-established methods for γH2AX analysis; foci counting
by microscopy and whole cell fluorescence intensity as measured by traditional flow cytometry. In
this study, we further developed an automated method for analysis of the γH2AX assay for
biodosimetry rapid triage, using an ImageStream®X Mark II Imaging Flow Cytometer (IFC) and analysed
with IDEAS® software.
The benefit of the IFC is that it combines spot counting, for the sensitivity and specificity of microscopy,
while adding the greater throughput and statistical power of flow cytometry (2). This method can be
used to quickly identify patients who have received exposure doses that require immediate medical
attention during a large scale event. This will be useful to reduce the demand on a biological dosimetry
laboratory by providing early triage of samples to reduce time spent on other standard biodosimetry
methods for no or low dose samples.
27Experimental evidence supporting the premature chromosome condensation hypothesis for
chromosome shattering in S-phase micronuclei as the underlying mechanism for chromothripsis
A. Pantelias1, I. Karachristou1, A. Georgakilas2, G. Terzoudi1
1
Laboratory of Health Physics, Radiobiology & Cytogenetics, Institute of Nuclear & Radiological
Sciences & Technology, Energy & Safety, National Centre for Scientific Research "Demokritos", Athens,
Greece 2DNA Damage Laboratory, Physics Department, National Technical University of Athens, Greece
antonio.pantelias@gmail.com
Recent studies have shown that complex chromosomal rearrangements affecting one or a few
chromosomes can arise from a single catastrophic event. This phenomenon has been termed
chromothripsis, describing its distinctive feature involving chromosome (chromo) shattering (thripsis).
While the characterization of the affected chromosomes has provided new insights into the processes
by which cancer genomes can evolve, the underlying signaling events and molecular mechanisms
remain unknown. A number of hypotheses have been proposed, including that chromothripsis is
induced in lagging chromosomes encapsulated in micronuclei. Following an aberrant mitosis,
chromosomes can find themselves in the wrong place at the wrong time and be subjected to massive
DNA breakage and rearrangement in the event of asynchrony between the main nuclei and
micronuclei. In an attempt to monitor the fate of chromosomes inside micronuclei, ionizing radiation
was used to generate aberrant mitoses. In continuation, by regulating the cell cycle kinetics of the
micronuclei in relation to their neighboring main nuclei, the impact on the encapsulated chromosomes
was observed under different experimental conditions. The results obtained support the hypothesis
that when the main nuclei enter mitosis, premature chromosome condensation induction in
micronuclei triggers shattering and chromothripsis only in chromosomes still undergoing DNA
replication.
28Biological effectiveness of very high gamma dose rate and its implication for biological dosimetry
1
Milagrosa López Riego, 1Dante Olofsson, 1Lei Cheng, 1Rubén Barrios Fernández, 2Magdalena Lipka,
1
Pamela Akuwudike, 2Halina Lisowska, 1Lovisa Lundholm, 12Andrzej Wojcik
1
Centre for Radiation Protection Research, Department of Molecular Biosciences, The Wenner-Gren
Institute, Stockholm University, Sweden, 2Department of Radiobiology and Immunology, Institute of
Biology, Jan Kochanowski University, Kielce, Poland
milagrosa.lopezriego@su.se
Background. According to the International Atomic Energy Agency (IAEA) recommendations, gamma
radiation calibration curves for biological dosimetry should be generated at a dose rate of ca 1 Gy/min.
In practice, different dose rates are used. Also, in accidental exposures, the dose rate rarely matches
that of the calibration curve.
Aim. The aim was to assess the dose rate impact on the shape of a micronucleus and gene expression
dose response relationship.
Methods. Freshly drawn blood of a single donor was exposed at 37 °C to 0, 1, 2 and 3 Gy of gamma
radiation at three dose rates: 0.4, 0.8 and 8.2 Gy/min. Whole blood cultures were set up for the
micronucleus (MN) assay. In parallel, leukocytes were isolated 24 hour post irradiation and expression
levels of FDXR, GADD45a and MDM2 genes were assessed by real time quantitative polymerase chain
reactions (qPCR). In order to validate the results in another cell system, MN assay and 53BP1 foci
frequency were also analysed in U20S-53BP1 cells.
Results/conclusions. At 0.4 and 0.8 Gy/min, neither the MN dose response curves nor the expression
levels of the 3 genes, best fitted by a linear-quadratic function and linear function, respectively,
differed significantly. At 8.25 Gy/min, significantly steeper dose response curves were observed, best
fitted to a linear function for MN and a saturating linear-quadratic function for gene expression.
Supporting results were achieved in U2OS cells. In conclusion, radiation at high dose rate is more
effective in inducing DNA damage than at medium dose rate.
Work supported by the Swedish Radiation Safety Authority SSM
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