Effectiveness Of Proton Beams Research Articles

Effects of Proton Beams and X Rays on the Cell Cycle of Fluorescent Ubiquitination-Based Cell Cycle Indicator (Fucci)-Expressing Cells

Our previous study demonstrated that cisplatin had more potent sensitizing effects and yielded a significantly higher percentage of apoptotic cell death when combined with proton beams than with X-ray irradiation. Although such results may be explained by differences in the DNA repair mechanisms, other factors such as effects on cell cycle and organelles may possibly be involved. In this study, we evaluated the biological effects of protons and photons in combination with cisplatin on the cell cycle of 2 cultured cells expressing the fluorescent ubiquitination-based cell cycle indicator (Fucci). HeLa cells expressing the Fucci (HeLa/Fucci) were provided by the RIKEN BioResource Center (Tsukuba, Japan). HSG/Fucci was established in our laboratory by introducing mCherry and AmCyan1 into human HSG cells using the PiggyBac system. First, we evaluated the relative biological effectiveness (RBE) of the 2 cells using a standard colony assay. Then, to evaluate the cell cycle, appropriate numbers of cells were plated on 96-well plates to create scaffolds 6 hours before each experiment. From 1 hour before irradiation, the cells were exposed to the medium containing 0-2.5 μmol/L cisplatin and were irradiated with single doses of 0-8 Gy with X rays or proton beams under the same biological conditions. One hour after irradiation, cisplatin was washed out from the medium. The red and green fluorescence in G1 and S/G2/M phases, respectively, were observed and counted using the live cell fluorescence imaging data. Then, the effects on the cell cycle were evaluated. The RBE (D10) was 1.04 (95% CI: 1.01-1.07) for HeLa/Fucci and 1.04 (1.03-1.05) for HSG/Fucci. These data were comparable to our previous results on HSG: 1.01 (1.00-1.03). In time-lapse imaging, both X rays and proton beams increased the percentage of green S/G2/M phase cells after irradiation and delayed the cell cycle, suggesting the G2 arrest. The proportion of green cells was increased by high-dose proton irradiation, suggesting more significant arrest. Even after single administration of cisplatin, the percentage of green cells increased depending on the concentration of cisplatin, and it occurred at a later time than the G2 arrest caused by irradiation. The percentage of green cells at that time was higher when cisplatin was combined with proton beams than with X rays. Two peaks of increased green cells were observed, suggesting the different effects of cisplatin and irradiation on the cell cycle. In Fucci-expressing cells, both proton beams and X rays delayed the cell cycle, resulting in an increase in S/G2/M phase cells probably due to G2 arrest. Considering the timing of the increase in G2 arrest, potent biological effects may be obtained by delivering proton irradiation during radiosensitive cell cycle phases in chemo-proton therapy.

Proton Beams Inhibit Proliferation of Breast Cancer Cells by Altering DNA Methylation Status.

Proton beam therapy has been gaining popularity in the management of a wide spectrum of cancers. However, little is known about the effect of proton beams on epigenetic alterations. In this study, the effects of proton beams on DNA methylation were evaluated in the breast cell lines MCF-10A and MCF-7. Pyrosequencing analysis of the long interspersed element 1 (LINE1) gene indicated that a few specific CpG sites were induced to be hypermethylated by proton beam treatment from 64.5 to 76.5% and from 57.7 to 60.0% (p < 0.05) in MCF-10A and MCF-7, respectively. Genome-wide methylation analysis identified “Developmental Disorder, Hereditary Disorder, Metabolic Disease” as the top network in the MCF-7 cell line. The proliferation rate significantly decreased in proton beam-treated cells, as judged by colony formation and cell proliferation assay. Upon treatment with the proton beam, expression of selected genes (MDH2, STYXL1, CPE, FAM91A1, and GPR37) was significantly changed in accordance with the changes of methylation level. Taken together, the findings demonstrate that proton beam-induced physiological changes of cancer cells via methylation modification assists in establishing the epigenetic basis of proton beam therapy for cancer.

Study of the effects of high-energy proton beams on escherichia coli

Antibiotic-resistant bacterial infection is one of the most serious risks to public health care today. However, discouragingly, the development of new antibiotics has progressed little over the last decade. There is an urgent need for alternative approaches to treat antibiotic-resistant bacteria. Novel methods, which include photothermal therapy based on gold nano-materials and ionizing radiation such as X-rays and gamma rays, have been reported. Studies of the effects of high-energy proton radiation on bacteria have mainly focused on Bacillus species and its spores. The effect of proton beams on Escherichia coli (E. coli) has been limitedly reported. Escherichia coli is an important biological tool to obtain metabolic and genetic information and is a common model microorganism for studying toxicity and antimicrobial activity. In addition, E. coli is a common bacterium in the intestinal tract of mammals. In this research, the morphological and the physiological changes of E. coli after proton irradiation were investigated. Diluted solutions of cells were used for proton beam radiation. LB agar plates were used to count the number of colonies formed. The growth profile of the cells was monitored by using the optical density at 600 nm. The morphology of the irradiated cells was observed with an optical microscope. A microarray analysis was performed to examine the gene expression changes between irradiated samples and control samples without irradiation. E coli cells have observed to be elongated after proton irradiation with doses ranging from 13 to 93 Gy. Twenty-two were up-regulated more than twofold in proton-irradiated samples (93 Gy) compared with unexposed one.

Effect of proton beam on blood vessel formation in early developing zebrafish (Danio rerio) embryos

Proton beam therapy can kill tumor cells while saving normal cells because of its specific energy delivery properties and so is used to various tumor patients. However, the effect of proton beam on angiogenesis in the development of blood vessels has not been determined. Here we used the zebrafish model to determine in vivo whether proton beam inhibits angiogenesis. Flk-1-GFP transgenic embryos irradiated with protons (35 MeV, spread out Bragg peak, SOBP) demonstrated a marked inhibition of embryonic growth and an altered fluorescent blood vessel development in the trunk region. When cells were stained with acridine orange to evaluate DNA damage, the number of green fluorescent cell death spots was increased in trunk regions of irradiated embryos compared to non-irradiated control embryos. Proton beam also significantly increased the cell death rate in human umbilical vein endothelial cells (HUVEC), but pretreatment with N-acetyl cystein (NAC), an antioxidant, reduced the proton-induced cell death rate (p<0.01). Moreover, pretreatment with NAC abrogated the inhibition of trunk vessel development and prevented the trunk malformation caused by proton irradiation. In conclusion, proton irradiation significantly inhibited in vivo vascular development possibly due to increased vascular cell death via reactive oxygen species formation.

Effects of proton beams from the folded tandem ion accelerator on DNA damage in mouse leukocytes using the comet assay

Single cell gel electrophoresis or the comet assay is a sensitive technique to quantify different types of DNA damage, e.g. single strand breaks, double strand breaks, base damage at single cell level of any dividing or non-dividing eukaryotic cell. This paper describes the effect of 3.3 MeV proton beams from the folded tandem ion accelerator on DNA damage in mouse leukocytes using the comet assay. Images of the comets were acquired using an imaging system and quantified using the software SCGE-Pro. One of the salient findings of the study was the presence of highly damaged cells (HDC) as characterised by the presence of large DNA fragments in clusters. In addition, a large percentage of apoptotic cells was observed after proton irradiation. It has been demonstrated that low fluence proton beam irradiation caused damage to a high proportion of cells.

Branching ratios for secondary processes of water ions induced by proton beams in radiation therapy of cancer

New results are reported that can improve proton beam instrumentation in radiation medicine and cancer therapy. The destructive effects of proton beams are primarily based on direct collision ionization and radiolysis of water. Resulting fragments subsequently alter the cell cycle by damaging the DNA with different efficiency. We have therefore computed the water ion and hydronium potential energy surfaces and obtained branching ratios for proton-water processes that further involve low energy electrons, OH radicals, and metastable O/sup +/ ions. In addition, all related data available in the literature are shortly summarized and reviewed. State-selective excitation and electron capture cross sections reported in this paper allow for solving the rate equations of the ion production cascade.

陽子線治療 : その1 基礎(深部線量分布と生物学的効果比)

陽子線治療 : その1 基礎(深部線量分布と生物学的効果比)