Project description:The growing number of particle treatment facilities worldwide and patients treated with particles instead of X-rays marks the upcoming rearrangement of modern radiotherapy. Especially for tumors being difficult to access and for tumors that are resistant to conventional X-ray treatment particle radiotherapy is a beneficial technology. At the Heidelberg Ion Beam Therapy Center (HIT) patients are treated with this technology since 2009 as it offers clear benefits. Contrary to X-rays, which show an exponential dose decrease (after reaching electron equilibrium) with increasing tissue depth, charged particles deposit most of their energy to a small region within the tissue with a sharp dose fall-off after the so-called Bragg peak. This precise dose localization enables further dose escalation within the tumor while sparing healthy tissue. Besides physical advantages, particle radiotherapy offers additional biological advantages. In radiobiology, the term relative-biological effectiveness (RBE) is defined as the ratio of X-rays dose to an alternative irradiation modality dose which produce the same biological effect (e.g. survival or number of DSBs). While protons have a relative biological effectiveness (RBE) comparable to X-rays, carbon ions are more effective in inducing DNA damage(1, 2) and are therefore especially useful for radioresistant tumors. This is due to the fact, that carbon ions induce clustered and direct DNA damage, which is considered to be less dependent on cell cycle stage, oxygen level, genetic background and hinders DNA repair mechanisms(3–6). Nevertheless, their exact mode of action and cellular mechanisms are largely unknown. We show the first comprehensive proteomic and phosphoproteomic study elucidating the cellular response to treatment with protons, carbon ions and X-rays. We found that 2h after treatment with these radiations negligible regulation occurred at protein expression level. But 181 phosphorylation sites were deregulated by ionizing radiation contributing mainly to DNA damage response functionalities. Interestingly we found 55 phosphorylation sites being differentially regulated between the radiations. Here, we observed protons and carbon ions producing equal cellular response whereas X-rays show altered regulation for certain phosphorylation sites. A subset of 28 phosphorylation sites being involved in the DNA damage response or differentially regulated between the ionizing radiations was selected for result confirmation.

Project description:Background: In the event of an improvised nuclear device detonation, the prompt radiation exposure would consist of γ rays plus a neutron component that would contribute to the total dose. As neutrons cause more complex and difficult to repair damage to cells that would result in more severe health burden to affected individuals, it is paramount to be able to estimate the contribution of neutrons to an estimated dose, to provide information for those making treatment decisions. Results: Mice exposed to either 0.25 or 1 Gy of neutron or 1 or 4 Gy x-ray radiation were sacrificed at 1 or 7 days after exposure. Whole genome microarray analysis identified 7,285 and 5,045 differentially expressed genes in the blood of mice exposed to neutron or x-ray radiation, respectively. Neutron exposure resulted in mostly downregulated genes, whereas x-rays showed both down- and up-regulated genes. A total of 34 differentially expressed genes were regulated in response to all ≥1 Gy exposures at both times. Of these, 25 genes were consistently downregulated at days 1 and 7, whereas 9 genes, including the transcription factor E2f2, showed bi-directional regulation; being downregulated at day 1, while upregulated at day 7. Gene ontology analysis revealed that genes involved in nucleic acid metabolism processes were persistently downregulated in neutron irradiated mice, whereas genes involved in lipid metabolism were upregulated in x-ray irradiated animals. Most biological processes significantly enriched at both timepoints were consistently represented by either under- or over-expressed genes. In contrast, cell cycle processes were significant among down-regulated genes at day 1, but among up-regulated genes at day 7 after exposure to either neutron or x-rays. Cell cycle genes downregulated at day 1 were mostly distinct from the cell cycle genes upregulated at day 7. However, five cell cycle genes, Fzr1, Ube2c, Ccna2, Nusap1, and Cdc25b, were both downregulated at day 1 and upregulated at day 7. Conclusions: We describe, for the first time, the gene expression profile of mouse blood cells following exposure to neutrons. We have found that neutron radiation results in both distinct and common gene expression patterns compared with x-ray radiation.

Project description:In the current global scenario there is always a possibility that a terrorist group might acquire material to produce a nuclear device. In the likelihood of a detonation of an improvised nuclear device (IND) the prompt radiation would consist of both photons (gamma rays) and neutrons. As neutrons generally have a high Relative Biological Effectiveness (RBE) for most physiological endpoints, it is important to understand the impact that neutrons would have on the biodosimetry methods that are being developed for medical triage purposes. We have previously reported transcriptomic response in human and mouse blood to neutron exposure and determined its RBE compared to photons for gene induction. In this report, we studied the effect of mixed neutron-photon radiation on gene expression in human peripheral blood in order to mimic an IND type radiation observed increase in number as well as expression level of genes with increasing percentage of neutron in mixed exposures which peaked at 25% neutron exposure which was maximum neutron percentage used for the study. We identified 156 genes that responded significantly to all the neutron-photon mixed exposures. These genes were found to be mainly involved in p53 signaling and DNA damage response. The 25% neutron exposure also showed maximum enrichment of known neutron associated gene ontology terms reported in the previous studies. Analysis of upstream regulators of gene expression showed strong activation of TP53, SLC29A1, PDCD1 and suppression of ANLN, AURK and ANXA2 across all exposures. While AGT was exclusively activated by neutron specific exposures. We confirmed the expression of genes which showed increased expression as a function of increased neutron percentage using quantitative real-time RT-PCR which matched with the microarray data. Thus, the data in this current study clearly indicates that gene expression can be used to estimate the percentage of the neutron component in mixed neutron-photon exposures.

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Homo sapiens

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