RESUMO
The aim of the NEPTUNE (Nuclear process-driven Enhancement of Proton Therapy UNravEled) project is to investigate in detail both the physical and radiobiological phenomena that could justify an increase of the proton-induced cytogenetic effects in cells irradiated in presence of an agent containing natural boron. In this work, a double-stage silicon telescope coupled to different boron converters was irradiated at the CATANA proton therapy facility (INFN-LNS) for studying the proton boron fusion and the neutron boron capture reactions by discriminating secondary particles from primary protons. Different boron targets were developed by depositing boric acid, enriched with a higher than 99% content of 10B or 11B, on a 50⯵m thick PolyMethilMetacrylate (PMMA) substrate. The 10B target allows to evaluate the contribution of lithium and alpha particles produced by the boron neutron capture reaction triggered by secondary thermal neutrons, while the 11B target is exploited for studying the effect of the p + 11Bâ¯ââ¯3α nuclear reaction directly triggered by primary protons. Experimental results clearly show the presence of alpha particles from both the reactions. The silicon telescope is capable of discriminating, by means of the so-called "scatter plots", the contribution of alpha particles originated by thermal neutrons on 10B with respect to the ones produced by protons impinging on 11B. Although a reliable quantitative study of the alpha production rate has not been achieved yet, this work demonstrates that low energy and, therefore, high-LET particles from both the reactions can be measured.
Assuntos
Terapia por Captura de Nêutron de Boro , Terapia com Prótons , Boro , Nêutrons , PrótonsRESUMO
PURPOSE: The Geant4 Monte Carlo simulation toolkit was used to reproduce radiobiological parameters measured by irradiating three different cancerous cell lines with monochromatic and clinical proton beams. METHODS: The experimental set-up adopted for irradiations was fully simulated with a dedicated open-source Geant4 application. Cells survival fractions was calculated coupling the Geant4 simulations with two analytical radiobiological models: one based on the LEM (Local Effect Model) approach and the other on a semi-empirical parameterisation. Results was evaluated and compared with experimental data. RESULTS AND CONCLUSIONS: The results demonstrated the Geant4 ability to reproduce radiobiological quantities for different cell lines.
Assuntos
Método de Monte Carlo , Terapia com Prótons , Linhagem Celular Tumoral , Humanos , Radiobiologia , Dosagem Radioterapêutica , Reprodutibilidade dos TestesRESUMO
Among different radiotherapy techniques, proton irradiation is an established and effective method for treatment of several types of cancer, because less healthy tissue is exposed with respect to conventional radiotherapy by photons/electrons. Recently, proton therapy has been proposed for the treatment of breast cancer. In vitro studies of proton irradiated normal human breast cells can provide information about cellular radioresponse, particularly as far as healthy tissue is concerned. In this paper, a study of the effects at different time points, following proton irradiation at different doses, of human normal MCF10A breast cells is performed by Raman spectroscopy. The aim of this investigation is to detect the unwanted effects of proton treatment and to investigate the possibility of monitoring them and of making an assessment of the cellular sensitivity by means of such a technique. The obtained results seem to indicate a rather significant sensitivity of MCF10A cells to proton irradiation. In fact, even at doses as low as 0.5 Gy, biological effects are clearly detectable in Raman spectra. In particular, ratiometric analysis of the Raman spectra measured from the nucleoplasm compartment showed that DNA/RNA damage increases with time, suggesting that most cells are unable to repair DNA/RNA broken bonds. The results obtained by the Raman spectroscopy analysis exhibit a similar trend with regard to dose to those obtained by commonly used radiobiological assays (i.e. MTT, clonogenic assay, senescence, apoptosis and necrosis). The results of this study strongly suggest the possibility that the Raman technique can be used to identify molecular markers predicting radiation response.
Assuntos
Apoptose/efeitos da radiação , Mama/patologia , Proliferação de Células/efeitos da radiação , Dano ao DNA , Micronúcleos com Defeito Cromossômico/efeitos da radiação , Prótons/efeitos adversos , Análise Espectral Raman/métodos , Mama/efeitos da radiação , Células Cultivadas , Senescência Celular , Relação Dose-Resposta à Radiação , Feminino , Humanos , Necrose , Fatores de TempoRESUMO
Raman micro-spectroscopy was performed in vitro on nuclear and membrane regions of single SH-SY5Y human neuroblastoma cells after irradiation by graded X-ray doses (2, 4, 6, 8 Gy). The acquired spectra were analyzed by principal component analysis (PCA) and interval-PCA (i-PCA) methods. Biochemical changes occurring in the different regions of single cells as a consequence of the radiation exposure were observed in cells fixed immediately after the irradiation. The most relevant effects arose from the analysis of the spectra from the cell nucleus region. The observed changes were discussed in terms of the modifications in the cell cycle, resulting in an increase in the DNA-related signal, a protein rearrangement and changes in lipid and carbohydrates profiles within the nucleus. Potential markers of an apoptotic process in cell population irradiated with 6 and 8-Gy X-ray doses could have been singled out. No significant effects were found in spectra from cells fixed 24 h after the irradiation, thus suggesting the occurrence of repairing processes of the X-ray induced damage.
Assuntos
Membrana Celular/efeitos da radiação , Núcleo Celular/efeitos da radiação , Neuroblastoma/radioterapia , Análise de Célula Única/métodos , Análise Espectral Raman/métodos , Apoptose/efeitos da radiação , Ciclo Celular/efeitos da radiação , Linhagem Celular Tumoral , Relação Dose-Resposta à Radiação , Humanos , Doses de Radiação , Terapia por Raios XRESUMO
Protontherapy is hadrontherapy's fastest-growing modality and a pillar in the battle against cancer. Hadrontherapy's superiority lies in its inverted depth-dose profile, hence tumour-confined irradiation. Protons, however, lack distinct radiobiological advantages over photons or electrons. Higher LET (Linear Energy Transfer) 12C-ions can overcome cancer radioresistance: DNA lesion complexity increases with LET, resulting in efficient cell killing, i.e. higher Relative Biological Effectiveness (RBE). However, economic and radiobiological issues hamper 12C-ion clinical amenability. Thus, enhancing proton RBE is desirable. To this end, we exploited the p + 11B â 3α reaction to generate high-LET alpha particles with a clinical proton beam. To maximize the reaction rate, we used sodium borocaptate (BSH) with natural boron content. Boron-Neutron Capture Therapy (BNCT) uses 10B-enriched BSH for neutron irradiation-triggered alpha particles. We recorded significantly increased cellular lethality and chromosome aberration complexity. A strategy combining protontherapy's ballistic precision with the higher RBE promised by BNCT and 12C-ion therapy is thus demonstrated.
Assuntos
Terapia por Captura de Nêutron de Boro/métodos , Boro/uso terapêutico , Terapia Combinada/métodos , Nêutrons , Neoplasias da Próstata/radioterapia , Terapia com Prótons , Terapia com Prótons/métodos , Partículas alfa/uso terapêutico , Animais , Boroidretos/química , Boro/química , Terapia por Captura de Nêutron de Boro/instrumentação , Isótopos de Carbono/química , Morte Celular/efeitos da radiação , Linhagem Celular Tumoral , Aberrações Cromossômicas/efeitos da radiação , Terapia Combinada/instrumentação , Ciclotrons , Dano ao DNA , DNA de Neoplasias/genética , DNA de Neoplasias/metabolismo , DNA de Neoplasias/efeitos da radiação , Relação Dose-Resposta à Radiação , Corantes Fluorescentes/química , Humanos , Cariotipagem , Transferência Linear de Energia , Masculino , Neoplasias da Próstata/patologia , Terapia com Prótons/instrumentação , Eficiência Biológica Relativa , Compostos de Sulfidrila/químicaRESUMO
The case for a DNA-damaging action produced by radiofrequency (RF) signals remains controversial despite extensive research. With the advent of the Universal Mobile Telecommunication System (UMTS) the number of RF-radiation-exposed individuals is likely to escalate. Since the epigenetic effects of RF radiation are poorly understood and since the potential modifications of repair efficiency after exposure to known cytotoxic agents such as ionizing radiation have been investigated infrequently thus far, we studied the influence of UMTS exposure on the yield of chromosome aberrations induced by X rays. Human peripheral blood lymphocytes were exposed in vitro to a UMTS signal (frequency carrier of 1.95 GHz) for 24 h at 0.5 and 2.0 W/kg specific absorption rate (SAR) using a previously characterized waveguide system. The frequency of chromosome aberrations was measured on metaphase spreads from cells given 4 Gy of X rays immediately before RF radiation or sham exposures by fluorescence in situ hybridization. Unirradiated controls were RF-radiation- or sham-exposed. No significant variations due to the UMTS exposure were found in the fraction of aberrant cells. However, the frequency of exchanges per cell was affected by the SAR, showing a small but statistically significant increase of 0.11 exchange per cell compared to 0 W/kg SAR. We conclude that, although the 1.95 GHz signal (UMTS modulated) does not exacerbate the yield of aberrant cells caused by ionizing radiation, the overall burden of X-ray-induced chromosomal damage per cell in first-mitosis lymphocytes may be enhanced at 2.0 W/kg SAR. Hence the SAR may either influence the repair of X-ray-induced DNA breaks or alter the cell death pathways of the damage response.
Assuntos
Telefone Celular , Aberrações Cromossômicas/efeitos da radiação , Linfócitos/efeitos da radiação , Micro-Ondas/efeitos adversos , Raios X/efeitos adversos , Adulto , Morte Celular/efeitos da radiação , Células Cultivadas , Reparo do DNA/efeitos da radiação , Humanos , Linfócitos/citologia , Linfócitos/metabolismo , Masculino , Modelos BiológicosRESUMO
Shielding is the only practical countermeasure for the exposure to cosmic radiation during space travel. It is well known that light, hydrogenated materials, such as water and polyethylene, provide the best shielding against space radiation. Kevlar and Nextel are two materials of great interest for spacecraft shielding because of their known ability to protect human space infrastructures from meteoroids and debris. We measured the response to simulated heavy-ion cosmic radiation of these shielding materials and compared it to polyethylene, Lucite (PMMA), and aluminum. As proxy to galactic nuclei we used 1 GeV n iron or titanium ions. Both physics and biology tests were performed. The results show that Kevlar, which is rich in carbon atoms (about 50% in number), is an excellent space radiation shielding material. Physics tests show that its effectiveness is close (80-90%) to that of polyethylene, and biology data suggest that it can reduce the chromosomal damage more efficiently than PMMA. Nextel is less efficient as a radiation shield, and the expected reduction on dose is roughly half that provided by the same mass of polyethylene. Both Kevlar and Nextel are more effective than aluminum in the attenuation of heavy-ion dose.
Assuntos
Teste de Materiais/instrumentação , Aceleradores de Partículas/instrumentação , Proteção Radiológica/métodos , Astronave/instrumentação , Humanos , Doses de Radiação , RadiometriaRESUMO
We report results for chromosomal aberrations in human peripheral blood lymphocytes after they were exposed to high-energy iron ions with or without shielding at the HIMAC, AGS and NSRL accelerators. Isolated lymphocytes were exposed to iron ions with energies between 200 and 5000 MeV/nucleon in the 0.1-1-Gy dose range. Shielding materials consisted of polyethylene, lucite (PMMA), carbon, aluminum and lead, with mass thickness ranging from 2 to 30 g/cm2. After exposure, lymphocytes were stimulated to grow in vitro, and chromosomes were prematurely condensed using a phosphatase inhibitor (calyculin A). Aberrations were scored using FISH painting. The yield of total interchromosomal exchanges (including dicentrics, translocations and complex rearrangements) increased linearly with dose or fluence in the range studied. Shielding decreased the effectiveness per unit dose of iron ions. The highest RBE value was measured with the 1 GeV/nucleon iron-ion beam at NSRL. However, the RBE for the induction of aberrations apparently is not well correlated with the mean LET. When shielding thickness was increased, the frequency of aberrations per particle incident on the shield increased for the 500 MeV/nucleon ions and decreased for the 1 GeV/nucleon ions. Maximum variation at equal mass thickness was obtained with light materials (polyethylene, carbon or PMMA). Variations in the yield of chromosomal aberrations per iron particle incident on the shield follow variations in the dose per incident particle behind the shield but can be modified by the different RBE of the mixed radiation field produced by nuclear fragmentation. The results suggest that shielding design models should be benchmarked using both physics and biological data.
Assuntos
Aberrações Cromossômicas , Íons Pesados/efeitos adversos , Proteção Radiológica , Relação Dose-Resposta a Droga , Humanos , Ferro , Transferência Linear de Energia , Linfócitos/efeitos da radiação , Linfócitos/ultraestruturaRESUMO
We measured fluence and fragmentation of high-energy (1 or 5 A GeV) 56Fe ions accelerated at the Alternating Gradient Synchrotron or at the NASA Space Radiation Laboratory (Brookhaven National Laboratory, NY, USA) using solid-state CR-39 nuclear track detectors. Different targets (polyethylene, PMMA, C, Al, Pb) were used to produce a large spectrum of charged fragments. CR-39 plastics were exposed both in front and behind the shielding block (thickness ranging from 5 to 30 g/cm2) at a normal incidence and low fluence. The radiation dose deposited by surviving Fe ions and charged fragments was measured behind the shield using an ionization chamber. The distribution of the measured track size was exploited to distinguish the primary 56Fe ions tracks from the lighter fragments. Measurements of projectile's fluence in front of the shield were used to determine the dose per incident particle behind the block. Simultaneous measurements of primary 56Fe ion tracks in front and behind the shield were used to evaluate the fraction of surviving iron projectiles and the total charge-changing fragmentation cross-section. These physical measurements will be used to characterize the beam used in parallel biological experiments.
Assuntos
Íons Pesados , Ferro , Monitoramento de Radiação/instrumentação , Proteção Radiológica , Alumínio , Calibragem , Carbono , Chumbo , Transferência Linear de Energia , Plásticos , Polietileno , Polietilenoglicóis , Polimetil Metacrilato , Doses de Radiação , Espalhamento de Radiação , Voo Espacial , SíncrotronsRESUMO
The polykaryon-forming unit (PFU) assay measures the survival of multiple cycles of DNA synthesis after exposure to ionizing radiation, and it is known that there is a strong correlation between the slope of the PFU dose-response curve and the clonogenic initial slope. This suggests that DNA lesions expressed in clonogens are also important in PFU. Cells having a mutation in XRCC5 (also known as Ku80; strain xrs-6) and ATM (strain AT5BIVA) were hypersensitive in the PFU assay and in clonogens, while a strain of xrs-6 cells transfected with hamster wild-type XRCC5 cDNA displayed wild-type resistance in both assays. These data suggest that the DNA double-strand break (DSB) is an important lesion in PFU, although the relative radioresistance of PFU compared to clonogens indicates differential DSB toxicity. We propose that this results from the absence of cytokinesis-related loss of DNA fragments. Small variations in the radioresponse of PFU were observed between CHO K1 cell substrains, such that the xrs parental substrain RR-CHOK1 (carrying wild-type XRCC5) was more sensitive than an independent K1 substrain (E-CHOK1). Somatic hybridization showed that this variation is heritable and that the resistant E phenotype is dominant. In RR-CHOK1 cells there was a biphasic PFU radioresponse, which suggests that there may be transient expression at a locus selectively affecting PFU sensitivity.
Assuntos
Antígenos Nucleares , DNA Helicases , Proteínas de Ligação a DNA/deficiência , Fibroblastos/efeitos da radiação , Células Gigantes/efeitos da radiação , Proteínas Nucleares/deficiência , Ovário/efeitos da radiação , Proteínas Serina-Treonina Quinases/deficiência , Tolerância a Radiação/genética , Animais , Proteínas Mutadas de Ataxia Telangiectasia , Células CHO , Proteínas de Ciclo Celular , Linhagem Celular , Sobrevivência Celular/efeitos da radiação , Ensaio de Unidades Formadoras de Colônias , Cricetinae , Citocalasina B/farmacologia , Proteínas de Ligação a DNA/genética , Relação Dose-Resposta à Radiação , Feminino , Fibroblastos/citologia , Fibroblastos/efeitos dos fármacos , Células Gigantes/patologia , Humanos , Células Híbridas/efeitos da radiação , Autoantígeno Ku , Mutação , Proteínas Nucleares/genética , Ovário/citologia , Ovário/efeitos dos fármacos , Poliploidia , Proteínas Serina-Treonina Quinases/genética , Proteínas Supressoras de TumorRESUMO
In the polykaryon-forming unit (PFU) assay, which defines cell survival as the ability to form a cytochalasin-induced polykaryon of predetermined ploidy, the mode of PFU deletion is not known. Incubation of L5178Y-S PFU in cytochalasin resulted in polyploidy (> or =32C) and most polykaryons (>75%) ultimately underwent apoptosis, detected using chromatin condensation and externalised phosphatidylserine. However, large polykaryons carrying terminal deoxynucleotidyl transferase-mediated dUTP nick end-labelling (TUNEL)-labelled DNA strand breaks were not observed, presumably due to rapid loss of DNA. Gamma irradiation of PFU prior to cytochalasin exposure caused a reduction in the frequency of highly polyploid cells (>16C), consistent with either a supra-induction of apoptosis or a reduction in the ability of PFU to reach high ploidies. We conclude that L5178Y-S PFU are deleted by apoptosis.
Assuntos
Apoptose/fisiologia , Dano ao DNA , Células Gigantes/citologia , Animais , Anexinas/metabolismo , Citocalasina B/farmacologia , DNA/metabolismo , DNA/efeitos da radiação , Raios gama , Células Gigantes/efeitos dos fármacos , Células Gigantes/efeitos da radiação , Células Gigantes/ultraestrutura , Marcação In Situ das Extremidades Cortadas , Leucemia L5178 , Camundongos , Microscopia Eletrônica , Poliploidia , Células Tumorais CultivadasRESUMO
PURPOSE: The relationship between different forms of persistent radiation damage in irradiated cells was investigated in order to identify a common underlying mechanism. MATERIAL AND METHODS: V-79 Chinese hamster cells were irradiated with different doses of X-rays, neutrons and alpha-particles. In the progeny of surviving cells, up to 4 weeks after irradiation, delayed reproductive death, delayed micronuclei, delayed appearance of dicentric chromosomes and delayed apoptosis were investigated in parallel. RESULTS: A similar dose-response relationship was found for all endpoints, with a steep rise at low doses to a plateau at doses > 3 Gy. The target for inducing genomic instability by alpha-particles is larger than the nucleus. All chromosomes are equally involved in delayed breakage reunion events. CONCLUSION: The results indicate that non-lethal radiation damage to an extranuclear target leads to a persistent increase in clastogenic activity in the surviving irradiated cells.