Potential mechanisms involved in resistant phenotype of MCF-7 breast carcinoma cells to ionizing radiation induced apoptosis

In the present study, we investigated the mechanisms of apoptosis resistance and the roles of the phosphorylation of BRCA1, p21, the Bax/Bcl-2 protein ratio and cell cycle arrest in IR-induced apoptosis in MCF-7 cells. X-irradiation, in particular at low dose (1 Gy), but not carbon ion irradiation, had a significant antiproliferative effect on the growth of MCF-7 cells. 1 Gy X-irradiation resulted in G1 and G2 phase arrest, but 4 Gy induced a significant G1 block. In contrast, carbon ion irradiation resulted in a significant accumulation in the G2 phase. Concomitant with the phosphorylation of H2AX induced by DNA damage, carbon ion irradiation resulted in an approximately 1.9-2.8-fold increase in the phosphorylation of BRCA1 on serine residue 1524, significantly greater than that detected for X-irradiation. Carbon ion irradiation caused a dramatic increase in p21 expression and drastic decrease in Bax expression compared with X-irradiation. The data implicated that phosphorylation of BRCA1 on serine residue 1524 might, at least partially, induce p21 expression but repress Bax expression. Together, our results suggested that the phosphorylation of BRCA1 at Ser-1524 might contribute to the G2 phase arrest and might be an upstream signal involved in preventing apoptosis signal via upregulation of p21 and downregulation of the Bax/Bcl-2 ratio.     

N-乙酰基-S-烯丙基-L-半胱氨酸的合成及其抗辐射活性

以L-半胱氨酸为原料,经取代和酰化两步反应合成目标产物N-乙酰基-S-烯丙基-L-半胱氨酸(N-acetyl-S-allyl-L-cysteine,NAc-SAC)。以~(137)Csγ射线照射至不同剂量的ICR小鼠作为研究对象,通过30 d存活率实验、血相和免疫系统实验、各项脏器指数以及外周血淋巴细胞彗星实验,研究目标化合物分别在200、400、600 mg/kg给药剂量下的抗辐射活性。ICR小鼠经伽马射线照射至致死剂量7.5 Gy后,其存活率由单纯照射对照组的41.6%,分别提高到NAc-SAC给药组的58.3%、50.0%和66.7%,平均存活天数明显延长。~(137)Csγ射线照射至亚致死剂量6.0 Gy后,NAc-SAC在不同程度上增加了受照小鼠的脾指数、脾结节数(CFU-S)、骨髓DNA含量和白细胞数。彗星实验中7.0 Gy伽马射线照射联合NAc-SAC给药组小鼠外周血淋巴细胞的尾长、尾矩、Olive尾矩和尾部DNA百分含量明显低于7.0 Gy伽马射线单纯照射组(p0.01),提示NAc-SAC可明显降低辐射导致的DNA损伤。本研究表明,目标化合物NAc-SAC具有一定的抗辐射损伤作用。     

Effect of p53 on lung carcinoma cells irradiated by carbon ions or X-rays

The study is to investigate the feasibility and advantages of heavy ion beams on radiotherapy. The cellular cycle and apoptosis, cell reproductive death and p53 expression evaluated with flow cytometry, clonogenic survival assays and Western blot analysis were examined in lung carcinoma cells after exposure to 89.63 MeV/u carbon ion and 6 MV X-ray irradiations, respectively. The results showed that the number colonyforming assay of A549 was higher than that of H1299 cells in two radiation groups; A549 cellular cycle was arrested in G2/M in 12 h and the per-centage of apoptosis ascended at each time point of carbon ion radiation with doses, the expression of p53 upregulated with doses exposed to X-ray or carbon ion. The cell number in G2/M of H1299 and apoptosis were increasing at all time points with doses in 12C6+ ion irradiation group. The results suggested that the effects of carbon ions or X rays ir-radiation on lung carcinoma cells were different, 12C6+ ion irradiation could have more effect on upregulating the ex-pression of p53 than X-ray, and the upregulated expression of p53 might produce the cellular cycle G2/M arrested, apoptosis increasing; and p53 gene might affect the lung cancer cells radiosensitivity.     

Preliminary results of proton beam characterization for a facility of broad beam in vitro cell irradiation

The interaction of charged particles with living matter needs to be well understood for medical applications. Particularly, it is useful to study how ion beams interact with tissues in terms of damage, dose released and dose rate.One way to evaluate the biological effects induced by an ion beam is by the irradiation of cultured cells at a particle accelerator, where cells can be exposed to different ions at different energies and flux.In this paper, we report the first results concerning the characterization of a broad proton beam obtained with our 2 MV tandem accelerator. For broad beam in vitro cell irradiation, the beam has to be stable over time, uniform over a ∼0.5 cm² surface, and a dose rate ranging from 0.1 to 10 Gy/min must be achievable. Results concerning the level of achievement of these requirements are presented in this paper for a 1 MeV proton beam.     

Blister formation on tungsten damaged by high energy particle irradiation

In order to investigate the effect of radiation damage on hydrogen behavior in tungsten, tungsten samples with radiation damage of up to 3.5 dpa were irradiated by a mixed hydrogen-carbon ion beam. The radiation damage was produced with 700 keV negative hydrogen ion beam irradiation. The number density of blisters produced by the mixed ion beam irradiation decreased with increasing radiation damage. This was especially observed for blisters with diameters of 20 μm or less. This result showed that radiation damage produced by high-energy particle irradiation suppresses blister formation on tungsten surfaces.     

Bystander effect in human hepatoma HepG2 cells caused by medium transfers at different times after high-LET carbon ion irradiation

Although radiation-induced bystander effects have been well documented in a variety of biological systems, whether irradiated cells have the ability to generate bystander signaling persistently is still unclear and the clinical relevance of bystander effects in radiotherapy remains to be elucidated. This study examines tumor cellular bystander response to autologous medium from cell culture irradiated with high-linear energy transfer (LET) heavy ions at a therapeutically relevant dose in terms of clonogenic cell survival. In vitro experiments were performed using human hepatoma HepG2 cell line exposed to 100 keV/μm carbon ions at a dose of 2 Gy. Two different periods (2 and 12 h) after irradiation, irradiated cell conditioned medium (ICCM) and replenished fresh medium were harvested and then transferred to unirradiated bystander cells. Cellular bystander responses were measured with the different medium transfer protocols. Significant higher survival fractions of unirradiated cells receiving the media from the irradiated cultures at the different times post-irradiation than those of the control were observed. Even replenishing fresh medium for unirradiated cells which had been exposed to the ICCM for 12 h could not prevent the bystander cells from the increased survival fraction. These results suggest that the irradiated cells could release unidentified signal factor(s), which induced the increase in survival fraction for the unirradiated bystander cells, into the media sustainedly and the carbon ions triggered a cascade of signaling events in the irradiated cells rather than secreting the soluble signal factor(s) just at a short period after irradiation. Based on the observations in this study, the importance of bystander effect in clinical radiotherapy was discussed and incorporating the bystander effect into the current radiobiological models, which are applicable to heavy ion radiotherapy, is needed urgently.     

Study on DNA Damage Induced by Neon Beam Irradiation in Saccharomyces Cerevisiae

Yeast strain Saccharomyces cerevisiae was irradiated with different doses of 85 MeV/u 20Ne10+ to investigate DNA damage induced by heavy ion beam in eukaryotic microorganism. The survival rate, DNA double strand breaks (DSBs) and DNA polymorphic were tested after irradiation. The results showed that there were substantial differences in DNA between the control and irradiated samples. At the dose of 40 Gy, the yeast cell survival rate approached 50%, DNA double-strand breaks were barely detectable, and significant DNA polymorphism was observed. The alcohol dehydrogenase II gene was amplified and sequenced. It was observed that base changes in the mutant were mainly transversions of T→G and T→C. It can be concluded that heavy ion beam irradiation can lead to change in single gene and may be an effective way to induce mutation.     

Enhancement of etch rate for preparation of nano-sized ion-track membranes of poly(vinylidene fluoride): Effect of pretreatment and high-LET beam irradiation

We investigated how pretreatment and high-LET beam irradiation affected the ion-track dissolution rate in poly(vinylidene fluoride) (PVDF) films by SEM observations and conductometric analysis in order to develop the preparation methodology of nano-sized ion-track membranes. PVDF thin films irradiated with four types of ion beams were exposed to a 9 mol/dm³ KOH aqueous solution after their storage in air at 120 °C. This heating treatment was found to enhance the etch rate in the latent track, both in the inner core and outer halo regions, without changing that in the bulk, probably due to the formation of parasitic oxidation products facilitating the introduction of the etching agent to improve the etchability. Additionally, the irradiation of heavier higher-LET ions, causing each track to more activated sites (like radicals), was preferable for achieving effective etching.     

The electrical conductivity of carbon nanotube sheets by ion beam irradiation

A method for improving the electrical conductivity of carbon nanotube (CNT) sheets by ion beam irradiation is reported. CNT sheets prepared by a vacuum filtration method were irradiated by Ar and H ion beams at different temperatures. The electrical conductivity of the irradiated CNT sheets at a temperature of 800 K can be improved. The conductivity improvement can be ascribed to the formation of covalent bond crosslinks between CNTs induced by the ion beam irradiation at the elevated temperature.     

Stoichiometry evolution of polyethylene terephtalate under 3.7 MeV He irradiation

A 3.7 MeV He⁺ ion beam was simultaneously used for Polyethylene Terephtalate (PET) film degradation and characterization. To enhance the potentialities of the characterization method, a multi-detector Ion Beam Analysis (IBA) technique was used. The stoichiometry change of the PET target following the irradiation is quantified at a beam fluence varying between 7 × 10¹³ and 1.8 × 10¹⁶ He⁺ cm⁻². The damage induced in PET films by He⁺ bombarding was analyzed in-situ simultaneously through Rutherford Backscattering Spectrometry (RBS), Particle Elastic scattering Spectrometry (PES) and Hydrogen Elastic Recoil Detection (ERD).Appropriate experimental conditions for the observation of absolute changes in composition and thickness during irradiation were determined. The oxygen and carbon content evolution as a function of the ion fluence was monitored by He⁺ backscattering whereas the hydrogen content was measured by H(α, H)α collisions in which both the scattered He⁺ ions and the recoiling H could be observed. The present study reveals that, at the highest fluence 1.8 × 10¹⁶ He⁺ cm⁻², the PET films have lost approximately 15% of the carbon, more than 45% of the hydrogen and 85% of the oxygen of the amount contained in the pristine sample. The energy shift of recoiling H⁺ ions at a forward angle 45° was followed in order to study the mass loss effect.The experimental results are consistent with the bulk molecular recombination model. Based on the results, hydrogen, oxygen and carbon release cross sections are determined. For hydrogen, comparison with deuteron irradiation indicates a cross section linear dependence on the stopping power.     

DNA double-strand breaks induced along the trajectory of particles

It is well-known that the DNA damage caused by charged particles considerably differs from damage due to electromagnetic radiation. In the case of irradiation by charged particles the DNA lesions are more complex and clustered. Such clustered damage is presumed difficult to be repaired, and is potentially lethal. In this study, we utilize a 90°-scattering system and related imaging techniques to investigate the accumulation of γ-H2AX along the trajectory of charged particles. By immunostaining the γ-H2AX protein, optical images of corresponding double strand breaks were observed using a high resolution confocal microscope. We demonstrate the difference in the accumulation of γ-H2AX from irradiation by 1 MeV protons and that of 150 keV X-rays. The acquired images were arranged and reconstructed into a 3D image using ImageJ software. We discovered that the γ-H2AX foci, following irradiation by protons, have a tendency to extend in the beam direction, while those from X-ray irradiation tend to be smaller and more randomly distributed. These results can be explained by the physical model of energy deposition.     

Uranium-molybdenum nuclear fuel plates behaviour under heavy ion irradiation: An X-ray diffraction analysis

Heavy ion irradiation has been proposed for discriminating UMo/Al specimens which are good candidates for research reactor fuels. Two UMo/Al dispersed fuels (U-7 wt%Mo/Al and U-10 wt%Mo/Al) have been irradiated with a 80 MeV ¹²⁷I beam up to an ion fluence of 2 × 10¹⁷ cm⁻². Microscopy and mainly X-ray diffraction using large and micrometer sized beams have enabled to characterize the grown interaction layer: UAl₃ appears to be the only produced crystallized phase. The presence of an amorphous additional phase can however not be excluded. These results are in good agreement with characterizations performed on in-pile irradiated fuels and encourage new studies with heavy ion irradiation.     

Relationship between radiation damage anisotropy in MgO and YSZ single crystals and the Ion/Atom ratio deposition parameter in biaxially-textured MgO and YSZ thin films fabricated by ion beam assisted deposition

To elucidate the underlying physics of ion beam assisted deposition (IBAD), irradiation damage effects in magnesia (MgO) and yttria-stabilized zirconia (YSZ) were investigated. Ion irradiations were performed on MgO and YSZ single crystals of three low-index crystallographic orientations using 100 and 150 keV Ar⁺ ions over a fluence range from 1 × 10¹⁴ to 5 × 10¹⁶ Ar/cm². Damage accumulation was analyzed using Rutherford backscattering spectrometry combined with ion channeling. Damage evolution with increasing ion fluence proceeded via several characteristic stages and the total damage exhibited a strong dependence on crystallographic orientation. For both MgO and YSZ, damage anisotropy was maximal at a stage when the damage saturated, with the (1 1 0) crystallographic orientation being the most radiation damage resistant. The Ion/Atom ratio deposition parameter reported for IBAD of MgO and YSZ films was found to correlate with the damage plateau stage described above. Finally, the role of the Ion/Atom ratio is discussed in terms of radiation damage anisotropy mechanism.     

Electron transferring from titanium ion irradiated carbon nanotube arrays into vacuum under low applied fields

Field emission characteristics of carbon nanotube arrays synthesized by thermal chemical vapor deposition on iron ion pre-bombarded silicon substrate are enhanced by titanium ion irradiation. A pronounced degradation of turn-on electric field of 0.305 V/μm and threshold field, of which the lowest value is only 1.054 V/μm, about 0.482 V/μm at the dose of 5 × 10¹⁶ ions/cm² is as an expression of this enhancement. Scanning electron microscopy, Raman spectroscopy, x-ray photoelectron spectroscopy, Photoelectron spectrometer and transmission electron microscopy are measured for comparison before and after the Ti ion irradiation of the carbon nanotube arrays, and the results reveal that the formation of carbon nanorod/nanotube heterostructure during ion irradiation plays a dominative role in the promotion of the field emission properties. However, high-dose irradiating transaction on carbon nanotube arrays will exert repulsive effects on the field emission characteristics for the introduction of severe structural damage. Additionally, the longtime eminent stability behaviors under high applied fields have provided a possibility for the potential application of field emission flat panel display or electron emitters based on carbon nanotube arrays.     

Nanostructuring of BaF2 (1 1 1) surfaces by single slow highly charged ions

The creation of surface nanostructures in BaF₂ (1 1 1) surfaces was studied after irradiation with slow highly charged Xe ions from the Dresden-EBIT (electron beam ion trap). After irradiation, the crystals were investigated by scanning force microscopy (SFM). Using specific ion parameters, the topographic images show nanohillocks emerging from the surface. Additionally, we used the technique of selective chemical etching to reveal the lattice damage created by ion energy deposition below and above threshold needed for surface hillocks formation. The role of both potential and kinetic energy as well as a comparison with results for swift heavy ion irradiations of BaF₂ single crystals are presented.     

Temperature dependence of liquid Sn sputtering by low-energy He and D bombardment

Absolute sputtering yields of liquid tin from 240 to 420 °C due to irradiation by low-energy helium and deuterium have been measured. For ion energies ranging from 300 to 1000 eV, temperature enhancement of liquid tin sputtering was noted. These measurements were obtained by IIAX (the Ion-surface InterAction eXperiment) using a velocity-filtered ion beam at 45° incidence to sputter material from a liquid tin target onto deposition monitors. Sputtering yields from 500 eV ion bombardment at 45° incidence increase from 0.1 ± 0.03 and 0.019 ± 0.008 Sn particles/ion at room temperature, for He⁺ and D⁺ ions respectively, to 0.30 ± 0.12 and 0.125 ± 0.05 Sn particles/ion for 380 °C. Temperature enhanced sputtering has been seen in other liquid metals (namely lithium, tin-lithium, and gallium) using both ion beam and plasma irradiation.     

Oxygen effects on irradiated tantalum alloys

Ta and Ta-1% W are being considered to be used as target clad materials in the LANSCE proton beam line for the material test station (MTS). To investigate the embrittlement of these materials due to oxygen contamination and proton irradiation, Ta and Ta-1 wt% W (as received and with ∼400 ppm O) were exposed to a 3.5 MeV proton beam at the ion beam materials laboratory at LANL. After irradiating the samples in the proton beam, nanoindentation was performed in cross-section to investigate the hardness increase of the materials due to irradiation. The nanoindentation showed that the hardness increase due to irradiation is between 9% and 20% depending on the material. The results show good agreement with mechanical testing results on tantalum and Ta-1 wt% W after high energy proton irradiation to doses up to 23 dpa.     

New separator prepared by electron beam irradiation for high voltage lithium secondary batteries

Grafted separators, for which poly(ethylene glycol) borate acrylate (PEGBA) was grafted onto polyethylene (PE) separator, were newly prepared by electron beam irradiation. The grafted separators were characterized by FT-IR, energy dispersive X-ray spectrometer (EDS). The morphological changes of the grafted separators were investigated by scanning electron microscopy (SEM). The degree of grafting was increased with irradiation doses. The ionic conductivity of the grafted separator showed the highest value of 6.24 × 10⁻⁴ S cm⁻¹ at 10 kGy. In addition, its lithium ion transference number and electrochemical stability were enhanced to 0.53 and 4.8 V, respectively owing to anion trapping effect of the grafted unit. The Li ion cells using the grafted separator showed better cycle performances than that using conventional PE separator at various C-rates and high voltage operation conditions. It is suggested that this grafted separator can be a promising candidate for high voltage operation of lithium secondary batteries.     

Swift heavy ion induced phase transition in CdTe films deposited by spray pyrolysis in presence of electric field

CdTe polycrystalline thin films possessing hexagonal phase regions are obtained by spray deposition in presence of a high electric field. Thin film samples are irradiated with 100 MeV Ag ions using Pelletron accelerator to study the swift heavy ion induced effects. The ion irradiation results in the transformation of the metastable hexagonal regions in the films to stable cubic phase due to the dense electronic excitations induced by beam irradiation. The phase transformation is seen from the X-ray diffraction patterns. The band gap of the CdTe film changes marginally due to ion irradiation induced phase transformation. The value changes from 1.47 eV for the as deposited sample to 1.44 eV for the sample irradiated at the fluence 1×10¹³ ions/cm². The AFM images show a gradual change in the shape of the particles from rod shape to nearly spherical ones after irradiation.     

TGF-β1抑制剂增加H460肺癌细胞的放射敏感性

探索一种TGF-β1受体激酶的选择性抑制剂SB431542对H460非小细胞肺癌细胞的放射增敏作用及对其DNA损伤应答体系的干扰。采用克隆形成实验检测SB431542对H460细胞放射敏感性的影响;用移植瘤实验验证SB431542在体内对H460细胞的放射增敏作用;采用流式细胞术检测细胞周期分布和细胞凋亡;用免疫荧光检测53BP1 foci和磷酸化的DNA-PKcs foci。结果发现,SB431542可增加H460的放射敏感性。照射前用SB431542预处理H460细胞虽然快速启动了细胞的DNA损伤应答反应,但却抑制了DNA双链断裂的非同源末端链接修复,因此,导致细胞残留更多未修复的DNA双链断裂,从而产生更严重的细胞周期阻滞。研究还发现,这种增敏作用与细胞凋亡无关。体内移植瘤实验表明,与单独照射组相比,连续3次用SB431542联合5 Gy的X-射线处理明显在处理后第5~12 d之间降低了肿瘤的生长。这些结果显示,在照射前用SB431542抑制肿瘤细胞的TGF-β1通路,能降低其DNA损伤修复能力,改变细胞周期分布,降低细胞克隆形成能力,延缓肿瘤的生长,因此用SB431542抑制TGF-β1通路可作为一些类型肺癌病人放疗的有效辅助手段。