Effect of elevated temperature and hydrocortisone addition on the proliferation of fibroblasts.

Hyperthermia along with hydrocortisone (HC) are proven teratogens that can negatively influence embryo development during early pregnancy. Proliferation of cells is one of the main developmental processes during the early embryogenesis. This study was focused on testing the effect of elevated temperature and HC addition on proliferation of cells in in vitro cultures. The V79-4 cell line was treated with HC and cultured in vitro at 37 °C or 39 °C, respectively. To reveal the effect of both factors, the proliferation of cells cultured under different conditions was evaluated using various approaches (colony formation assay, generation of growth curves, computation of doubling times, and mitotic index estimation). Our results indicate that a short-term exposure to elevated temperature slightly stimulates and a long-term exposure suppresses cell proliferation. However, HC (0.1 mg/ml) acts as a stimulator of cell proliferation. Interestingly, the interaction of HC and long-term elevated temperature (39 °C) exposure results in at least partial compensation of the negative impact of elevated temperature by HC addition and in higher proliferation if compared with cells cultured at 39 °C without addition of HC.

In Vitro Comparison of Passive and Active Clinical Proton Beams.

Nowadays, the irradiation methodology in proton therapy is switching from the use of passively scattered beams to active pencil beams due to the possibility of more conformal dose distributions. The dose rates of active pencil beams are much higher than those of passive beams. The purpose of this study was to investigate whether there is any difference in the biological effectiveness of these passive and active irradiation modes. The beam qualities of double scattering and pencil beam scanning were measured dosimetrically and simulated using the Monte Carlo code. Using the medulloblastoma cell line DAOY, we performed an in vitro comparison of the two modes in two positions along the dose-deposition curve plateau and inside the Bragg peak. We followed the clonogenic cell survival, apoptosis, micronuclei, and γH2AX assays as biological endpoints. The Monte Carlo simulations did not reveal any difference between the beam qualities of the two modes. Furthermore, we did not observe any statistically significant difference between the two modes in the in vitro comparison of any of the examined biological endpoints. Our results do not show any biologically relevant differences related to the different dose rates of passive and active proton beams.

In Vivo Validation of Alternative FDXR Transcripts in Human Blood in Response to Ionizing Radiation.

Following cell stress such as ionising radiation (IR) exposure, multiple cellular pathways are activated. We recently demonstrated that ferredoxin reductase (FDXR) has a remarkable IR-induced transcriptional responsiveness in blood. Here, we provided a first comprehensive FDXR variant profile following DNA damage. First, specific quantitative real-time polymerase chain reaction (qPCR) primers were designed to establish dose-responses for eight curated FDXR variants, all up-regulated after IR in a dose-dependent manner. The potential role of gender on the expression of these variants was tested, and neither the variants response to IR nor the background level of expression was profoundly affected; moreover, in vitro induction of inflammation temporarily counteracted IR response early after exposure. Importantly, transcriptional up-regulation of these variants was further confirmed in vivo in blood of radiotherapy patients. Full-length nanopore sequencing was performed to identify other FDXR variants and revealed the high responsiveness of FDXR-201 and FDXR-208. Moreover, FDXR-218 and FDXR-219 showed no detectable endogenous expression, but a clear detection after IR. Overall, we characterised 14 FDXR transcript variants and identified for the first time their response to DNA damage in vivo. Future studies are required to unravel the function of these splicing variants, but they already represent a new class of radiation exposure biomarkers.

Degradation of phospholipids under different types of irradiation and varying oxygen saturation.

The effects of different types of radiation on the formation of peroxide forms of 2-dioleoyl-sn-glycero-3-phosphocholine were studied under various conditions. For the irradiation, an aqueous solution of small unilamellar vesicles was prepared. Variations in parameters such as the dose rate and molecular oxygen saturation levels were evaluated. Our study suggests that the mechanism of the peroxides formation process remains unchanged under irradiation by accelerated electrons, gamma and accelerated protons. The values of radiation chemical yields of the peroxidic form depend on the type of radiation, dose rate, and the saturation of molecular oxygen. The level of oxygen saturation strongly affects the values of radiation chemical yields as well, as the dissolved oxygen is an important agent participating in peroxidation and it is a source of free radicals during the radiolysis. The values of radiation chemical yields strongly suggest that the mechanism of radiation-induced peroxidation of phosphatidylcholines does not proceed via chain reaction.

Proton-induced direct and indirect damage of plasmid DNA.

Clustered DNA damage induced by 10, 20 and 30 MeV protons in pBR322 plasmid DNA was investigated. Besides determination of strand breaks, additional lesions were detected using base excision repair enzymes. The plasmid was irradiated in dry form, where indirect radiation effects were almost fully suppressed, and in water solution containing only minimal residual radical scavenger. Simultaneous irradiation of the plasmid DNA in the dry form and in the solution demonstrated the contribution of the indirect effect as prevalent. The damage composition slightly differed when comparing the results for liquid and dry samples. The obtained data were also subjected to analysis concerning different methodological approaches, particularly the influence of irradiation geometry, models used for calculation of strand break yields and interpretation of the strand breaks detected with the enzymes. It was shown that these parameters strongly affect the results.

Determining Omics spatiotemporal dimensions using exciting new nanoscopy techniques to assess complex cell responses to DNA damage: part A--radiomics.

Recent ground-breaking developments in Omics have generated new hope for overcoming the complexity and variability of biological systems while simultaneously shedding more light on fundamental radiobiological questions that have remained unanswered for decades. In the era of Omics, our knowledge of how genes and proteins interact in the frame of complex networks to preserve genome integrity has been rapidly expanding. Nevertheless, these functional networks must be observed with strong correspondence to the cell nucleus, which is the main target of ionizing radiation. Nuclear architecture and nuclear processes, including DNA damage responses, are precisely organized in space and time. Information regarding these intricate processes cannot be achieved using high-throughput Omics approaches alone, but requires sophisticated structural probing and imaging. Based on the results obtained from studying the relationship between higher-order chromatin structure, DNA double-strand break induction and repair, and the formation of chromosomal translocations, we show the development of Omics solutions especially for radiation research (radiomics) (discussed in this article) and how confocal microscopy as well as novel approaches of molecular localization nanoscopy fill the gaps to successfully place the Omics data in the context of space and time (discussed in our other article in this issue, "Determining Omics Spatiotemporal Dimensions Using Exciting New Nanoscopy Techniques to Assess Complex Cell Responses to DNA Damage: Part B--Structuromics"). Finally, we introduce a novel method of specific chromatin nanotargeting and speculate future perspectives, which may combine nanoprobing and structural nanoscopy to observe structure-function correlations in living cells in real time. Thus, the Omics networks obtained from function analyses may be enriched by real-time visualization of Structuromics.

Determining Omics spatiotemporal dimensions using exciting new nanoscopy techniques to assess complex cell responses to DNA damage: part B--structuromics.

Recent groundbreaking developments in Omics and bioinformatics have generated new hope for overcoming the complexity and variability of (radio)biological systems while simultaneously shedding more light on fundamental radiobiological questions that have remained unanswered for decades. In the era of Omics, our knowledge of how genes and dozens of proteins interact in the frame of complex signaling and repair pathways (or, rather, networks) to preserve the integrity of the genome has been rapidly expanding. Nevertheless, these functional networks must be observed with strong correspondence to the cell nucleus, which is the main target of ionizing radiation. Information regarding these intricate processes cannot be achieved using high-throughput Omics approaches alone; it requires sophisticated structural probing and imaging. In the first part of this review, the article "Giving Omics Spatiotemporal Dimensions Using Exciting New Nanoscopy Techniques to Assess Complex Cell Responses to DNA Damage: Part A--Radiomics," we showed the development of different Omics solutions and how they are contributing to a better understanding of cellular radiation response. In this Part B we show how high-resolution confocal microscopy as well as novel approaches of molecular localization nanoscopy fill the gaps to successfully place Omics data in the context of space and time. The dynamics of double-strand breaks during repair processes and chromosomal rearrangements at the microscale correlated to aberration induction are explained. For the first time we visualize pan-nuclear nucleosomal rearrangements and clustering at the nanoscale during repair processes. Finally, we introduce a novel method of specific chromatin nanotargeting based on a computer database search of uniquely binding oligonucleotide combinations (COMBO-FISH). With these challenging techniques on hand, we speculate future perspectives that may combine specific COMBO-FISH nanoprobing and structural nanoscopy to observe structure-function correlations in living cells in real-time. Thus, the Omics networks obtained from function analyses may be enriched by real-time visualization of Structuromics.

Clustered DNA damage on subcellular level: effect of scavengers.

Clustered DNA damages are induced by ionizing radiation, particularly of high linear energy transfer (LET). Compared to isolated DNA damage sites, their biological effects can be more severe. We investigated a clustered DNA damage induced by high LET radiation (C 290 MeV u(-1) and Fe 500 MeV u(-1)) in pBR322 plasmid DNA. The plasmid is dissolved in pure water or in aqueous solution of one of the three scavengers (coumarin-3-carboxylic acid, dimethylsulfoxide, and glycylglycine). The yield of double strand breaks (DSB) induced in the DNA plasmid-scavenger system by heavy ion radiation was found to decrease with increasing scavenging capacity due to reaction with hydroxyl radical, linearly with high correlation coefficients. The yield of non-DSB clusters was found to occur twice as much as the DSB. Their decrease with increasing scavenging capacity had lower linear correlation coefficients. This indicates that the yield of non-DSB clusters depends on more factors, which are likely connected to the chemical properties of individual scavengers.

MONTE CARLO SIMULATIONS OF OUT-OF-FIELD LET SPECTRA IN WATER PHANTOM IRRADIATED BY SCANNING PENCIL PROTON BEAM.

LET spectra can be measured by track-etched detectors. However, these detectors are not able to identify the type of interacting particles. Monte Carlo simulations can provide this missing information. In this work, Monte Carlo simulations based on the EURADOS Work Group 9 experiment consisting of systematic 3D mapping of out-of-field doses and LET spectra in a prototype water phantom were performed. The simulations aimed to identify the types of particles contributing to the out-of-field LET spectra. The total absorbed dose, LET and energy spectra were calculated. The calculated dose distributions and LET spectra were compared with the ones measured by radiophotoluminiscence and track-etched detectors. The out-of-field particles and their LET values were identified. No statistically significant differences between the measured and simulated spectra were revealed in the LET range of 100-2000 keV µm-1.

EXPERIMENTAL IN VITRO DOSIMETRY OF 223RA AND 177LU.

Targeted alpha therapy with radionuclides undergoing multiple alpha-particle decays is a promising method of nuclear medicine. To study the effectiveness of alpha versus beta emitters, survival of DU145 prostate cancer cells exposed to 223Ra or 177Lu was assessed. Per decay, the cells were much more sensitive to the alpha than beta emitter. However, per unit dose the sensitivities would be comparable, contrary to the well-known evidence, if the decay energy were deposited within the sample completely and homogeneously. Measurements by Timepix detectors showed about three times higher counts of alpha particles above than below the sample. After the first alpha decay of 223Ra to 219Rn, this gas likely moves upwards and its subsequent three alpha decays occur in the upper part of the sample. Correct estimation of absorbed dose is a critical issue when analysing in vitro data and when translating their results to clinical applications.

BORON-ENHANCED BIOLOGICAL EFFECTIVENESS OF PROTON IRRADIATION: STRATEGY TO ASSESS THE UNDERPINNING MECHANISM.

Proton radiotherapy for the treatment of cancer offers an excellent dose distribution. Cellular experiments have shown that in terms of biological effects, the sharp dose distribution is further amplified, by as much as 75%, in the presence of boron. It is a matter of debate whether the underlying physical processes involve the nuclear reaction of 11B with protons or 10B with secondary neutrons, both producing densely ionizing short-ranged particles. Likewise, potential roles of intercellular communication or boron acting as a radiosensitizer are not clear. We present an ongoing research project based on a multiscale approach to elucidate the mechanism by which boron enhances the effectiveness of proton irradiation in the Bragg peak. It combines experimental with simulation tools to study the physics of proton-boron interactions, and to analyze intra- and inter-cellular boron biology upon proton irradiation.

RADIATION DAMAGE TO DNA PLASMIDS IN THE PRESENCE OF BOROCAPTATES.

Boron derivatives have great potential in cancer diagnostics and treatment. Borocaptates are used in boron neutron capture therapy and potentially in proton boron fusion therapy. This work examines modulation effects of two borocaptate compounds on radiation-induced DNA damage. Aqueous solutions of pBR322 plasmid containing increasing concentrations of borocaptates were irradiated with 60Co gamma rays or 30 MeV protons. Induction of single and double DNA strand breaks was investigated using agarose gel electrophoresis. In this model system, representing DNA without the intervention of cellular repair mechanisms, the boron derivatives acted as antioxidants. Clinically relevant boron concentrations of 40 ppm reduced the DNA single strand breakage seven-fold. Possible mechanisms of the observed effect are discussed.

Out-of-field doses in pediatric craniospinal irradiations with 3D-CRT, VMAT, and scanning proton radiotherapy: A phantom study.

PURPOSE: Craniospinal irradiation (CSI) has greatly increased survival rates for patients with a diagnosis of medulloblastoma and other primitive neuroectodermal tumors. However, as it includes exposure of a large volume of healthy tissue to unwanted doses, there is a strong concern about the complications of the treatment, especially for the children. To estimate the risk of second cancers and other unwanted effects, out-of-field dose assessment is necessary. The purpose of this study is to evaluate and compare out-of-field doses in pediatric CSI treatment using conventional and advanced photon radiotherapy (RT) and advanced proton therapy. To our knowledge, it is the first such comparison based on in-phantom measurements. Additionally, for out-of-field doses during photon RT in this and other studies, comparisons were made using analytical modeling. METHODS: In order to describe the out-of-field doses absorbed in a pediatric patient during actual clinical treatment, an anthropomorphic phantom, which mimics the 10-year-old child, was used. Photon 3D-conformal RT (3D-CRT) and two advanced, highly conformal techniques: photon volumetric-modulated arc therapy (VMAT) and active pencil beam scanning (PBS) proton RT were used for CSI treatment. Radiophotoluminescent and poly-allyl-diglycol-carbonate nuclear track detectors were used for photon and neutron dosimetry in the phantom, respectively. Out-of-field doses from neutrons were expressed in terms of dose equivalent. A two-Gaussian model was implemented for out-of-field doses during photon RT. RESULTS: The mean VMAT photon doses per target dose to all organs in this study were under 50% of the target dose (i.e., <500 mGy/Gy), while the mean 3D-CRT photon dose to oesophagus, gall bladder, and thyroid, exceeded that value. However, for 3D-CRT, better sparing was achieved for eyes and lungs. The mean PBS photon doses for all organs were up to three orders of magnitude lower compared to VMAT and 3D-CRT and exceeded 10 mGy/Gy only for the oesophagus, intestine, and lungs. The mean neutron dose equivalent during PBS for eight organs of interest (thyroid, breasts, lungs, liver, stomach, gall bladder, bladder, prostate) ranged from 1.2 mSv/Gy for bladder to 23.1 mSv/Gy for breasts. Comparison of out-of-field doses in this and other phantom studies found in the literature showed that a simple and fast two-Gaussian model for out-of-field doses as a function of distance from the field edge can be applied in a CSI using photon RT techniques. CONCLUSIONS: PBS is the most promising technique for out-of-field dose reduction in comparison to photon techniques. Among photon techniques, VMAT is a preferred choice for most of out-of-field organs and especially for the thyroid, while doses for eyes, breasts, and lungs are lower for 3D-CRT. For organs outside the field edge, a simple analytical model can be helpful for clinicians involved in treatment planning using photon RT but also for retrospective data analysis for cancer risk estimates and epidemiology in general.

Out-of-Field Doses Produced by a Proton Scanning Beam Inside Pediatric Anthropomorphic Phantoms and Their Comparison With Different Photon Modalities.

Since 2010, EURADOS Working Group 9 (Radiation Dosimetry in Radiotherapy) has been involved in the investigation of secondary and scattered radiation doses in X-ray and proton therapy, especially in the case of pediatric patients. The main goal of this paper is to analyze and compare out-of-field neutron and non-neutron organ doses inside 5- and 10-year-old pediatric anthropomorphic phantoms for the treatment of a 5-cm-diameter brain tumor. Proton irradiations were carried out at the Cyclotron Centre Bronowice in IFJ PAN Krakow Poland using a pencil beam scanning technique (PBS) at a gantry with a dedicated scanning nozzle (IBA Proton Therapy System, Proteus 235). Thermoluminescent and radiophotoluminescent dosimeters were used for non-neutron dose measurements while secondary neutrons were measured with track-etched detectors. Out-of-field doses measured using intensity-modulated proton therapy (IMPT) were compared with previous measurements performed within a WG9 for three different photon radiotherapy techniques: 1) intensity-modulated radiation therapy (IMRT), 2) three-dimensional conformal radiation therapy (3D CDRT) performed on a Varian Clinac 2300 linear accelerator (LINAC) in the Centre of Oncology, Krakow, Poland, and 3) Gamma Knife surgery performed on the Leksell Gamma Knife (GK) at the University Hospital Centre Zagreb, Croatia. Phantoms and detectors used in experiments as well as the target location were the same for both photon and proton modalities. The total organ dose equivalent expressed as the sum of neutron and non-neutron components in IMPT was found to be significantly lower (two to three orders of magnitude) in comparison with the different photon radiotherapy techniques for the same delivered tumor dose. For IMPT, neutron doses are lower than non-neutron doses close to the target but become larger than non-neutron doses further away from the target. Results of WG9 studies have provided out-of-field dose levels required for an extensive set of radiotherapy techniques, including proton therapy, and involving a complete description of organ doses of pediatric patients. Such studies are needed for validating mathematical models and Monte Carlo simulation tools for out-of-field dosimetry which is essential for dedicated epidemiological studies which evaluate the risk of second cancers and other late effects for pediatric patients treated with radiotherapy.

Gamma radiation effects on diamond field-effect biosensors with fibroblasts and extracellular matrix.

Due to high biocompatibility, miniaturization, optical transparency and low production cost together with high radiation hardness the diamond-based sensors are considered promising for radiation medicine and biomedicine in general. Here we present detection of fibroblast cell culture properties by nanocrystalline diamond solution-gated field-effect transistors (SG-FET), including effects of gamma irradiation. We show that blank nanocrystalline diamond field-effect biosensors are stable at least up to 300 Gy of γ irradiation. On the other hand, gate current of the diamond SG-FET biosensors with fibroblastic cells increases exponentially over an order of magnitude with increasing radiation dose. Extracellular matrix (ECM) formation is also detected and analyzed by correlation of electronic sensor data with optical, atomic force, fluorescence, and scanning electron microscopies.

Folding DNA into origami nanostructures enhances resistance to ionizing radiation.

We report experimental results on damage induced by ionizing radiation to DNA origami triangles which are commonly used prototypes for scaffolded DNA origami nanostructures. We demonstrate extreme stability of DNA origami upon irradiation, which is caused by (i) the multi-row design holding the shape of the origami even after severe damage to the scaffold DNA and (ii) the reduction of damage to the scaffold DNA due to the protective effect of the folded structure. With respect to damage induced by ionizing radiation, the protective effect of the structure is superior to that of a naturally paired DNA double helix. Present results allow estimating the stability of scaffolded DNA origami nanostructures in applications such as nanotechnology, pharmacy or in singulo molecular studies where they are exposed to ionizing radiation from natural and artificial sources. Additionally, possibilities are opened for scaffolded DNA use in the design of radiation-resistant and radio-sensitive materials.

Assessment of DNA damage with an adapted independent reaction time approach implemented in Geant4-DNA for the simulation of diffusion-controlled reactions between radio-induced reactive species and a chromatin fiber.

PURPOSE: Simulation of indirect damage originating from the attack of free radical species produced by ionizing radiation on biological molecules based on the independent pair approximation is investigated in this work. In addition, a new approach, relying on the independent pair approximation that is at the origin of the independent reaction time (IRT) method, is proposed in the chemical stage of Geant4-DNA. METHODS: This new approach has been designed to respect the current Geant4-DNA chemistry framework while proposing a variant IRT method. Based on the synchronous algorithm, this implementation allows us to access the information concerning the position of radicals and may make it more convenient for biological damage simulations. Estimates of the evolution of free species as well as biological hits in a segment of DNA chromatin fiber in Geant4-DNA were compared for the dynamic time step approach of the step-by-step (SBS) method, currently used in Geant4-DNA, and this newly implemented IRT. RESULTS: Results show a gain in computation time of a factor of 30 for high LET particle tracks with a better than 10% agreement on the number of DNA hits between the value obtained with the IRT method as implemented in this work and the SBS method currently available in Geant4-DNA. CONCLUSION: Offering in Geant4-DNA more efficient methods for the chemical step based on the IRT method is a task in progress. For the calculation of biological damage, information on the position of chemical species is a crucial point. This can be achieved using the method presented in this paper.

Overcoming challenges in human saliva gene expression measurements.

Saliva, as a non-invasive and easily accessible biofluid, has been shown to contain RNA biomarkers for prediction and diagnosis of several diseases. However, systematic analysis done by our group identified two problematic issues not coherently described before: (1) most of the isolated RNA originates from the oral microbiome and (2) the amount of isolated human RNA is comparatively low. The degree of bacterial contamination showed ratios up to 1:900,000, so that only about one out of 900,000 RNA copies was of human origin, but the RNA quality (average RIN 6.7 + /- 0.8) allowed for qRT-PCR. Using 12 saliva samples from healthy donors, we modified the methodology to (1) select only human RNA during cDNA synthesis by aiming at the poly(A)+-tail and (2) introduced a pre-amplification of human RNA before qRT-PCR. Further, the manufacturer's criteria for successful pre-amplification (Ct values ≤ 35 for unamplified cDNA) had to be replaced by (3) proofing linear pre-amplification for each gene, thus, increasing the number of evaluable samples up to 70.6%. When considering theses three modifications unbiased gene expression analysis on human salivary RNA can be performed.

RADIOPROTECTIVE EFFECT OF HYDROXYL RADICAL SCAVENGERS ON PROKARYOTIC AND EUKARYOTIC CELLS UNDER VARIOUS GAMMA IRRADIATION CONDITIONS.

The influence of various hydroxyl radical scavengers such as methanol, ethanol and dimethyl sulfoxide on radiation sensitivity of prokaryotic cells (bacteria Escherichia coli) and eukaryotic cells (yeast Saccharomyces cerevisiae and V79 cells-Chinese hamster pulmonary fibroblasts) irradiated by 60Co gamma radiation was investigated. The dependence of radiation sensitivity on dose rate in range from 1.8 to 100 Gy h-1 was evaluated. Survival of cells irradiated by increasing dose rates was followed using clonogenic assay. Specific protective effect was found to be a nonmonotonous function of dose rate with typical maximum at the dose rate range from 50 to 55 Gy h-1 in all studied cell types.

HOW DETECTION OF PLASMID DNA FRAGMENTATION AFFECTS RADIATION STRAND BREAK YIELDS.

A compromised detection of radiation-induced plasmid DNA fragments results in underestimation of calculated damage yields. Electrophoretic methods are easy and cheap, but they can only detect a part of the fragments, neglecting the shortest ones. These can be detected with atomic force microscopy, but at the expense of time and price. Both methods were used to investigate their capabilities to detect the DNA fragments induced by high-energetic heavy ions. The results were taken into account in calculations of radiation-induced yields of single and double strand breaks. It was estimated that the double strand break yield is twice as high when the fragments are at least partially detected with the agarose electrophoresis, compared to when they were completely omitted. Further increase by 13% was observed when the measured fragments were corrected for the fraction of the shortest fragments up to 300 base pairs, as detected with the atomic force microscopy. The effect of fragment detection on the single strand break yield was diminished.