Feasibility study on the use of gold nanoparticles in fractionated kilovoltage X-ray treatment of melanoma

Purpose: Despite the high radioresistance of melanoma, unresectable lesions can be subjected to radiation treatment with the use of gold nanoparticles (AuNPs) as a dose-enhancing agent preferentially loaded on these lesions. The modality of single high-dose treatment has been investigated to confirm its therapeutic efficiency for AuNP-treated melanoma cells. This study explores the feasibility of utilizing AuNPs in fractionated radiation therapy of melanoma for further therapeutic gain.

Materials and methods: The responses of human skin melanoma cells to 150-kVp X-ray exposure at 2 and 4?Gy were assessed by quantify gamma-H2AX expression and clonogenic survival, with or without 320 μM of 50?nm AuNP treatment in a culture medium. The influence of AuNPs on cell cycle distribution was observed before irradiation and during 3 d period after irradiation.

Results: The AuNP treatment of melanoma cells influenced the cellular response to kilovoltage X-rays to similar extents in terms of the percentage of gamma-H2AX-positive cells and the fractional loss of clonogenicity. Without radiation exposure, AuNPs reduced the portion of melanoma cells at the G₂/M phase from 11 to 7%. After irradiation, the progression of the melanoma cells treated with AuNPs toward the G₂/M phase was more rapid than that of the AuNP-free cells, and the release of the former from the G₂/M phase was slower than that of the latter. At 24?h after irradiation with AuNPs, the cell cycle was rearranged in a pattern that increased the vulnerability of the cells to radiation damage.

Conclusions: In addition to the benefit of AuNP treatment to the control of melanoma in single high-dose treatment, further therapeutic gain is expected through fractionated X-ray treatment that involves daily exposure. The AuNP-treated melanoma cells of an increased portion in the radiosensitive G₂/M phase following a fractionated dose delivery would respond to the next treatment with an enhanced chance of clonogenic death.     

Evaluation of the premature chromosome condensation scoring protocol after proton and X-ray irradiation of human peripheral blood lymphocytes at high doses range

Purpose of the study: One of the main difficulties in radiation dose assessment is cells inability to reach mitosis after exposure to acute radiation. Premature chromosome condensation (PCC) has become an important method used in biological dosimetry in case of exposure to high doses. Various ways to induce PCC including mitotic cells fusion, chemical stimulation with calyculin A or okadaic acid give wide spectrum of application. The main goal of this study was to evaluate the utility of drug-induced PCC scoring procedure by testing 2 experimental modes where 150 and 75 G2/M-PCC phase cells were analyzed after exposure to high dose proton and X-ray radiation. Another aim is to determine the differences in cellular response induced by proton and photon radiation using a HPBL in vitro model as a further extension of our previous studies involving doses up to 4.0?Gy.

Materials and methods: Total body exposure was simulated by irradiating whole blood collected from a healthy donor. Whole blood samples were exposed to two radiation types: 60?MeV protons and 250 kVp X-rays in the dose range of 5.0–20.0?Gy, the dose rate for protons was 0.075 and 0.15?Gy/s for X-rays. Post 48?h of human peripheral blood lymphocytes (HPBL) culture, calyculin A was added. After Giemsa staining, chromosome spreads were photographed and manually analyzed by scorers in the G2/M-PCC phase. In order to check the consistency of obtained results all scorers followed identical scoring criteria. Additionally, PCC index kinetics was evaluated for first 500 cells scored.

Conclusions: Here we provide a different method of results analysis. Presented dose-response curves were obtained by calculating the value of counted excess chromosome fragments. The results indicated that obtained dose estimates as adequate in the high dose range till 18.0?Gy for both studied radiation types, giving an opportunity to further improve PCC assay procedure and shorten the analysis time i.e. in case of partial-body exposure. Moreover, the study presents preliminary results of HPBL cellular response after proton irradiation at high doses range showing differences of PCC index kinetics for different cell classes and cell distribution.     

Relation between DNA double-strand breaks and energy spectra of secondary electrons produced by different X-ray energies

Purpose: In a radiological examination, low-energy X-radiation is used (<100?keV). For other radiological procedures, the energy used is several MeV. ICRP in publication 103 has currently considered that photons irrespective of their energy have the same radiation weighting factor. Nevertheless, there are topological differences at the nanoscale of X-ray energy deposition as a function of its energy spectrum, meaning that the different interactions with living matter could vary in biological efficacy.

Materials and methods: To study these differences, we characterized our irradiation conditions in terms of initial photon energies, but especially in terms of energy spectra of secondary electrons at the cell nucleus level, using Monte Carlo simulations. We evaluated signaling of DNA damage by monitoring a large number of γH2A.X foci after exposure of G0/G1-phase synchronized human primary endothelial cells from 0.25 to 5?Gy at 40?kV, 220?kV and 4?MV X-rays. Number and spatial distribution of γH2A.X foci were explored. In parallel, we investigated cell behavior through cell death and ability of a mother cell to produce two daughter cells. We also studied the missegregation rate after cell division.

Results: We report a higher number of DNA double-strand breaks signaled by γH2A.X for 40?kVp and/or 220?kVp compared to 4?MVp for the highest tested doses of 2 and 5?Gy. We observed no difference between the biological endpoint studies with 40?kVp and 220?kVp X-ray spectra. This lack of difference could be explained by the relative similarity of the calculated energy spectra of secondary electrons at the cell monolayer.

Conclusion: The energy spectrum of secondary electrons seems to be more closely related to the level of DNA damage measured by γH2A.X than the initial spectrum of photon energy or voltage settings. Our results indicate that as the energy spectrum of secondary electrons increases, the DNA damage signaled by γH2A.X decreases and this effect is observable beyond 220?kVp.     

Effect of low-dose X-ray irradiation on micronucleus formation in human embryo,newborn and child cells

Purpose: It is well known that a high-dose of ionizing radiation is sufficient to break DNA strands, which leads to elevated genotoxic risks; however, the risks associated with low doses of ionizing radiation remain unclear. In addition, there is little data about the effect of low-dose ionizing radiation on human-derived embryo, newborn and child cells. We investigated the frequency of micronucleus (MN) formation in these cells to understand the genotoxic effects of ionizing radiation.

Materials and methods: We irradiated the cells with X-rays from 0.02–2?Gy at a rate of 0.0635?Gy/min. After irradiation, we investigated the effect of low-dose X-ray irradiation on cellular viability and frequency of MN formation.

Results: Increases in MN formation were largely dose-dependent; however, there were no differences between controls and doses lower than 0.2?Gy, except in KMST-6 human transformed embryo cells.

Conclusion: We could not detect an obvious effect of low-dose X-ray irradiation at doses lower than 0.1?Gy. The embryonic cells were more sensitive to X-ray irradiation than newborn and child cells. The threshold for X-ray-induced MN formation appears to be in the range of 0.05–0.1?Gy in cultured human embryo, newborn and child cells.     

Fractionated exposure to low doses of ionizing radiation results in accumulation of DNA damage in mouse spleen tissue and activation of apoptosis in a p53/Atm-independent manner

Purpose: While the effects of high doses of ionizing radiation (IR) are relatively well characterized, the molecular mechanisms underlying cellular responses to prolonged exposure to low doses of radiation remain largely under-investigated.

Materials and methods: Here, we addressed the DNA damage and apoptotic response in the spleen tissue of C57BL/6 male mice after fractionated exposure to X-rays within the 0.1–0.5?Gy dose range.

Results: The response to initial exposure to 0.1?Gy of IR was characterized by increased DNA damage and elevated levels of apoptosis. Subsequent exposures (cumulative doses of 0.2 and 0.3?Gy) resulted in adaptive response-like changes, represented as increased proliferation and apoptotic response. Cumulative doses of 0.4 and 0.5?Gy were characterized by accumulation of DNA damage and reactivation of apoptosis and apoptosis-related proteins. Additionally, spleen cells with irreversible damage caused by radiation can undergo apoptosis via activation of p38, which does not necessarily involve the Atm/p53 pathway.

Conclusions: Fractionated exposure to low doses of X-rays resulted in accumulation of DNA damage in the murine spleen and induction of apoptotic response in p53/Atm-independent manner. Further studies are needed to understand the outcomes and molecular mechanisms underlying cellular responses and early induction of p38 in response to prolonged exposure to IR.     

Development of a guinea pig cutaneous radiation injury model using low penetrating X-rays

Purpose: A guinea pig skin model was developed to determine the dose-dependent response to soft X-ray radiation into the dermis.

Materials and methods: X-ray exposure (50 kVp) was defined to a 4.0?×?4.0?cm area on the lateral surface of a guinea pig using lead shielding. Guinea pigs were exposed to a single fraction of X-ray irradiation ranging from 25–79?Gy via an XRAD320ix Biological Irradiator with the collimator removed. Gross skin changes were measured using clinical assessments defined by the Kumar scale. Skin contracture was assessed, as well as histological evaluations.

Results: Loss of dermal integrity was shown after a single dose of soft X-ray radiation at or above 32?Gy with the central 2.0?×?2.0?cm of the exposed site being the most affected. Hallmarks of the skin injury included moist desquamation, ulceration and wound contracture, as well as alterations in epithelium, dermis, muscle and adipose. Changes in the skin were time- and radiation dose-dependent. Full-thickness injury occurred without animal mortality or gross changes in the underlying organs.

Conclusions: The guinea pig is an appropriate small animal model for the short-term screening of countermeasures for cutaneous radiation injury (CRI).     

Increased radiotoxicity in two cancerous cell lines irradiated by low and high energy photons in the presence of thio-glucose bound gold nanoparticles

Purpose: Gold nanoparticles modified by thio-glucose are believed to increase the toxicity of radiotherapy in human malignant cells. We report the effect of thio-glucose bound gold nanoparticles (Glu-G nanoparticles), 16?nm in size, on two human lung (QU-DB) and breast (MCF7) cancer cell lines combined with kilo and megavoltage X-rays.

Materials and methods: The shape and surface characteristics, the size distribution and light absorption spectrum of the prepared nanoparticles were measured by transmission electron microscopy, dynamic light scattering, and ultraviolet-visible spectrophotometry, respectively. The cell uptake was assayed using the atomic absorption spectrometry. Mitochondrial activity, colony formation, and comet assays were applied to assess and compare the enhanced radiotoxicity of 100?KV and 6?MV X-rays, when combined with Glu-G nanoparticles.

Results: Glu-G nanoparticles had no significant toxicity for MCF7 and QU-DB cells up to 100 micromolar concentration. Compared to radiation alone, the intracellular uptake of Glu-G nanoparticles resulted in increased inhibition of cell proliferation by 64.1% and 38.7% for MCF7 cells, and 64.4% and 32.4% for QU-DB cells by 100 kVp and 6?MV X-rays, respectively. Comet assay confirmed an increase of DNA damage as a result of combination of 6?MV photons with Glu-G nanoparticles.

Conclusion: Glu-G nanoparticles have remarkable potential for enhancing radiotoxicity of both low and high energy photons in MCF7 and QU-DB cells.     

X-ray radiation and developmental inhibition of Drosophila suzukii (Matsumura) (Diptera: Drosophilidae)

Purpose: Different doses of X-ray radiation were tested to assess the developmental inhibition effects on different stages of Drosophila suzukii, spotted wing drosophila (SWD). Efficacy of a potential quarantine treatment dose was evaluated for its practicality by a small scale-up validation test at a commercial facility.

Materials and methods: X-ray treatments at different doses of 50, 100, 200, and 300?Gy were carried out with eggs, larvae, pupae and adults of SWD. The trial at the commercial facility was performed with pupae at 150?Gy.

Results: X-ray radiation inhibited development of all stages of SWD, and the estimated dose to cause 99% mortality or to prevent emergence (ED₉₉) are reported here. Irradiation to eggs inhibited hatching, pupariation and adult emergence at 1962, 649 and 31?Gy, respectively. The inhibition of irradiated larvae to adult emergence was 66?Gy. Irradiation to pupae could not inhibit adult emergence completely even at 300?Gy. However, irradiation at 100?Gy and above induced complete adult sterility. Irradiation to pupae inhibited hatching of F₁ eggs at 73?Gy, while for adults, total inhibition of F₁ egg hatching was observed at 822?Gy. In the trial at the commercial facility, radiation at 150?Gy to pupae induced complete adult sterility in all combinations of cross-mating between treated or untreated males and females.

Conclusion: This study suggests that X-ray radiation can be recommended as an alternative to methyl bromide as phytosanitary treatment for quarantine purpose.     

The Rejoining of DNA Double-strand Breaks Following Irradiation with 238Pu α-particles: Evidence for a Fast Component of Repair as Measured by Neutral Filter Elution

Summary

The induction and repair of DNA double-strand breaks (DSB) following exposure to ²³⁸Pu α-particles was examined in V79-379A cells. The technique of neutral filter elution was used in these investigations at both pH 9·6 and pH 7·2. The initial dsb yield was found to be similar to that seen after 250 kVp X-ray or 2·3 MeV neutron exposure. However, the pattern of dsb rejoining after α-particle irradiation did not follow that seen after X-rays or neutrons. A very fast initial component, complete within 2 min of incubation following irradiation, removed 70 per cent of the dsb seen after 40 Gy α-particles; very little slow rejoining was seen. This contrasts sharply with the dsb rejoining seen after X-ray or neutron exposure, and presumably reflects the differences in the nature of the dsb induced and the way they are repaired.     

Preferential tumour accumulation of gold nanoparticles,visualised by magnetic resonance imaging: Radiosensitisation studies in vivo and in vitro

Purpose:?To investigate the radiosensitisation of gold nanoparticles (GNP) with an average diameter of 5 nm coated with the gadolinium chelating agent dithiolated diethylenetriaminepentaacetic gadolinium (Au@DTDTPA:Gd) in?vitro and in mice bearing tumours (MC7-L1).

Materials and methods:?In vivo, the gadolinium chelate coating allows one to perform real-time Magnetic Resonance Imaging (MRI) pharmacokinetic analysis during intravenous infusion. Experiments were performed following treatment with 10 Gy of 150 kVp X-rays. In vitro experiments were also performed with clonogenic assays to generate dose response curves for the same cells.

Results:?We observed a preferential accumulation of Au@DTDTPA:Gd in tumours; a substantial toxicity for tumour cells in?vitro, but no obvious toxicity for mice; and the absence of a synergistic effect with Au@DTDTPA:Gd and radiation in all experiments.

Conclusions:?The additional absorption of radiation and the subsequent increase in secondary electrons, attributable to the presence of gold in Au@DTDTPA:Gd, does not lead to radiosensitisation. However, this chelating agent exhibits a chemotherapeutic action which warrants further investigation. When compared to positive results obtained by others on radiosensitisation by GNP, the present study suggests that the chemotherapeutic and radiosensitising properties of GNP may depend strongly on the nature of the coating.     

Ionizing radiation does not impair the mechanisms controlling genetic stability during T cell receptor gene rearrangement in mice

Purpose: To determine whether low dose/low dose rate radiation-induced genetic instability may result from radiation-induced inactivation of mechanisms induced by the ATM-dependent DNA damage response checkpoint. To this end, we analysed the faithfulness of T cell receptor (TR) gene rearrangement by V(D)J recombination in DNA from mice exposed to a single dose of X-ray or chronically exposed to low dose rate γ radiation.

Materials and methods: Genomic DNA obtained from the blood or the thymus of wild type or Ogg1-deficient mice exposed to low (0.1) or intermediate/high (0.2–1?Gy) doses of radiation either by acute X-rays exposure or protracted exposure to low dose-rate γ-radiation was used to analyse by PCR the presence of illegitimate TR gene rearrangements.

Results: Radiation exposure does not increase the onset of TR gene trans-rearrangements in irradiated mice. In mice where it happens, trans-rearrangements remain sporadic events in developing T lymphocytes.

Conclusion: We concluded that low dose/low dose rate ionizing radiation (IR) exposure does not lead to widespread inactivation of ATM-dependent mechanisms, and therefore that the mechanisms enforcing genetic stability are not impaired by IR in developing lymphocytes and lymphocyte progenitors, including BM-derived hematopoietic stem cells, in low dose/low dose rate exposed mice.     

Neighbor effect: penumbra-dose exposed neighbor cells contribute to the enhanced survival of high-dose targeted cells

Purpose: In the last decade, new types of ‘bystander effect’ have been suggested by multiple research groups and have been challenged by others. In this study, we explored a new type of bystander effect, which has been defined in previous studies as the enhancement of the survival of high-dose targeted cells due to the penumbra-dose exposed neighbor cells. Intensity-modulated radiation therapy, which is the most widely used treatment modality, generates local regions of gradient doses between targeted and shielded cells throughout the treatment volume; therefore, we were urged to ascertain whether the new type of effect is real and to suggest a revised treatment planning.

Materials and methods: Cellular responses under non-uniform beam fields were observed in rat gliosarcoma cells, rat diencephalon cells, and mouse endothelial cells. The cells were irradiated with 200 kVp X-rays in two types: (1) all the cells in the flask were exposed to the X-ray beam (whole-beam exposure) and (2) half of the cells in the flask were exposed to the beam while the other half, or neighbor cells, were shielded from the beam (half-beam exposure). Target cells were exposed to 1, 2, 4, 6, 8, and 10?Gy, and the penumbra dose was approximately 10%–20% of the target dose.

Results: Target cells survived high-dose (>?6?Gy) radiation exposures better under half-beam exposure with the low penumbra-dose exposed neighbor cells around than under whole-beam exposure. The survival of the targeted cells from half-beam exposure was reduced when the radiation self-conditioned medium was replaced with a fresh one immediately after irradiation. Survival was further reduced when the targeted cells were harvested immediately after irradiation and incubated in new dishes with fresh culture media until the colony was counted.

Conclusion: We have collected data of good statistics by several post-irradiation treatments of targeted cells to ascertain that the new type of bystander effect is real. The low penumbra-dose exposed neighbor cells benefited the survival of the high-dose targeted cells.     

Combined treatment with X-ray irradiation and 5-aminolevulinic acid elicits better transcriptomic response of cell cycle-related factors than X-ray irradiation alone

Purpose: 5-Aminolevulinic acid (ALA) is a precursor of the photosensitizer protoporphyrin (PpIX) used in photodynamic therapy. In our previous work, PpIX enhanced the generation of reactive oxygen species by X-ray irradiation. In this study, we evaluated the potential of ALA as an endogenous sensitizer to X-ray irradiation.

Methodology: Tumor-bearing C57BL/6J mice implanted with B16-BL6 melanoma cells were subsequently treated with irradiation (3?Gy/day for 10 days; total, 30?Gy) plus local administration of 50?mg/kg ALA 24?hours prior to each irradiation (ALA-XT). Tumor-bearing mice without treatment (NT), those treated with ALA only (ALAT), and those treated with X-ray irradiation only (XT) were used as controls.

Results: ALA potentiated tumor suppression by X-ray irradiation. In microarray analyses using tumor tissue collected after 10 sessions of fractional irradiation, functional analysis revealed that the majority of dysregulated genes in the XT and ALA-XT groups were related to cell-cycle arrest. Finally, the XT and ALA-XT groups differed in the strength of expression, but not in the pattern of expression.

Conclusions: mRNA analysis revealed that the combined use of ALA and X-ray irradiation sensitized tumors to X-ray treatment. Furthermore, the present results were consistent with ALA’s tumor suppressive effects in vivo.     

Biological effects and inter-individual variability in peripheral blood lymphocytes of healthy donors exposed to 60 MeV proton radiotherapeutic beam

Purpose: The aim of our study was to investigate the amount of initial DNA damage and cellular repair capacity of human peripheral blood lymphocytes exposed to the therapeutic proton beam and compare it to X-rays.

Materials and methods: Lymphocytes from 10 healthy donors were irradiated in the Spread Out Bragg Peak of the 60?MeV proton beam or, as a reference, exposed to 250?kV X-rays. DNA damage level was assessed using the alkaline version of the comet assay method. For both sources of radiation, dose–DNA damage response (0–4?Gy) and DNA repair kinetics (0–120?min) were estimated. The observed DNA damage was then used to calculate the relative biological effectiveness (RBE) of the proton beam in comparison to that of X-rays.

Results: Dose–response relationships for the DNA damage level showed linear dependence for both proton beam and X-rays (R²?=?0.995 for protons and R²?=?0.993 for X-rays). Within the dose range of 1–4?Gy, protons were significantly more effective in inducing DNA damage than were X-rays (p?<?.05). The average RBE, calculated from the proton and X-ray doses required for the iso-effective, internally standardized tail DNA parameter (sT-DNA) was 1.28?±?0.57. Similar half-life time of residual damage and repair efficiency of induced DNA damage for both radiation types were observed. In the X-irradiated group, significant inter-individual differences were observed.

Conclusions: Proton therapy was more effective at high radiation doses. However, DNA damage repair mechanism after proton irradiation seems to differ from that following X-rays.     

A small fish model for quantitative analysis of radiation effects using visualized thymus responses in GFP transgenic medaka

Abstract

Purpose: The aim of this study was to establish a new method of real-time, in vivo detection of radiation damage and recovery.

Methods: The thymus was observed under fluorescent light in a green fluorescent protein transgenic medaka. After irradiation, medaka thymus images were analyzed to quantify the effects of radiation by measuring changes in thymus size. A single acute irradiation of X-rays (0–30?Gy) or heavy Fe ions (0–10?Gy) was delivered to the medaka. Images were captured 0, 1, 2, 3, 5, 7, 11, and 21 d after irradiation. Dose-response assessment was conducted to provide a direct measurement of the effects of the radiation.

Conclusion: A biomonitoring system to detect the effects of radiation in real time was established. Using this system, the threshold doses for the induction of thymic atrophy by acute X-rays and Fe ions were 2–5?Gy and 0.5–1?Gy, respectively. The Relative Biological Effectiveness (RBE) of Fe-ion to X-rays was estimated to be around 3. This system may be used to evaluate the risk from concurrent exposure to hazards, such as chemicals and radiation, and for aging research.     

Synchrotron-produced Ultrasoft X-rays: A Tool for Testing Biophysical Models of Radiation Action

Summary

Ultrasoft X-rays are useful for mechanistic studies of ionizing radiation damage in living cells due to the localized nature of their energy depositions. To date radiobiology experiments in this energy region have relied on characteristic X-rays (mainly Al_k and C_k) from X-ray tubes. However, limitations in the photon intensity and the available energies from X-ray tube sources prevent a definitive characterization of the relationship between photon energy and biological damage. Synchrotron radiation has the potential to avoid these limitations, since it produces X-rays with high intensity over a continuous spectrum. We have established a synchrotron-based system for radiation biology studies using the ES-0 exposure station of the Center for X-ray Lithography at the University of Wisconsin Synchrotron Radiation Center storage ring, Aladdin. A characterization of the system including spectral and intensity properties of the photon beam is presented. The first mammalian cell survival curve for synchrotron-produced ultrasoft X-rays was generated and is presented. Cell survival curves of C3H/10T1/2 cells using synchrotron radiation of 1·48 keV agree with previous data using Al_k X-rays (1·49 keV). An RBE of 1·47 ± 0·30 at the 10% survival level was measured with reference to 250 kVp X-rays.     

Oxidative and nitrative stress-related changes in human lens epithelial cells following exposure to X-rays

Purpose: There is limited understanding of the mechanistic effects of ionizing radiation (IR) exposure in cataract formation. In this study, we explored the effects of IR on reactive oxygen/nitrogen species (ROS and RNS) generation in human lens epithelial (HLE) cells as an early key event to long-term damage.

Materials and methods: HLE cell-line was exposed to X-rays at varied doses (0–5?Gy) and dose-rates. Cell lysates and supernatants were collected 20?h post-exposure and analysed for viability, cell cycling and metabolites of ROS (p, m-, o-, tyrosines, 3-chlorotyrosine (cl-tyrosine), 8-hydroxy deoxyguanosine, (8-OH-dG) and RNS (3-nitrotyrosine).

Results and conclusions: HLE cell-line exhibited a bi-phasic response in terms of cell viability, ROS and RNS profiles. At doses <0.5?Gy, ROS and RNS levels were lower than control and at higher doses (>0.5?Gy) a steady increase was observed in each metabolite. This response was observed irrespective of dose-rate. Among the associations tested, cl, p, m-tyrosine and 3-nitrotyrosine revealed changes (p?相似文献   

Acute pulmonary and splenic response in an in vivo model of whole-body low-dose X-radiation exposure

Abstract

Purpose: Diagnostic radiation is an important part of patient care in the Intensive Care Unit; however, there is little data on the acute effects of exposure to these doses. We investigated pulmonary and splenic response 30?minutes, 4?hours or 24?hours after exposure to 2?mGy, 20?mGy, 200?mGy or 4?Gy whole-body X-radiation in a Sprague Dawley rat model.

Materials and methods: Lung injury was assessed via respiratory mechanics, pulmonary edema, cellular, and proteinaceous fluid infiltrate and protein expression of oxidative stress markers. The radiation effect on the spleen was determined via proliferation, apoptosis and protein expression of oxidative stress markers.

Results: All measurements of the lung did not differ from sham animals except for an increase in catalase after high dose exposure. Stimulated splenocyte proliferation increased after sham and low dose exposure, did not change after 200?mGy exposure and was significantly lower after 4?Gy exposure. The number of apoptotic cells increased 4?hours after 4?Gy exposure. There were fewer apoptotic cells after low dose exposure compared to sham. Both catalase and MnSOD were increased after 4?Gy exposure.

Conclusion: There was no measured effect on pulmonary function while there was an impact to the spleen after low and high dose exposure.     

Cell Density Dependence of Transformation Frequencies in C3H10T1/2 Cells Exposed to X-rays

Summary

The effects of cell density on transformation frequencies were studied in C3H10T1/2 cells exposed to 0·5 and 7 Gy of 200 kVp X-rays. Initial cell density strongly influenced transformation frequency; this decreased by a factor of between 4 and 10 when the initial seeding density was changed from 50 to 2500 cells/10 cm diameter Petri dish. The data were fitted with two equations: (a) an allometric function represented on a log—log scale by a straight line and (b) a sigmoidal function with plateaux between 50 and 250 cells/dish and above 600. The two curves are compared and their probabilities discussed. Our data indicate that the region between 50 and 250 cells/dish would be the most suitable region for dose—effect measurements. A study of the growth curves at 0·5 and 8·5 Gy shows that cell growth rates are not influenced by initial cell density.     

Exploring the radiosensitizing potential of magnetotherapy: a pilot study in breast cancer cells

Abstract

Aim: To explore the influence of electromagnetic fields (EMFs) on the cell cycle progression of MDA-MB-231 and MCF-7 breast cancer cell lines and to evaluate the radiosensitizing effect of magnetotherapy during therapeutic co-exposure to EMFs and radiotherapy.

Material and methods: Cells were exposed to EMFs (25, 50 and 100?Hz; 8 and 10?mT). In the co-treatment, cells were first exposed to EMFs (50?Hz/10?mT) for 30?min and then to ionizing radiation (IR) (2?Gy) 4?h later. Cell cycle progression and free radical production were evaluated by flow cytometry, while radiosensitivity was explored by colony formation assay.

Results: Generalized G1-phase arrest was found in both cell lines several hours after EMF exposure. Interestingly, a marked G1-phase delay was observed at 4?h after exposure to 50?Hz/10?mT EMFs. No cell cycle perturbation was observed after repeated exposure to EMFs. IR-derived ROS production was enhanced in EMF-exposed MCF-7 cells at 24?h post-exposure. EMF-exposed cells were more radiosensitive in comparison to sham-exposed cells.

Conclusions: These results highlight the potential benefits of concomitant treatment with magnetotherapy before radiotherapy sessions to enhance the effectiveness of breast cancer therapy. Further studies are warranted to identify the subset(s) of patients who would benefit from this multimodal treatment.