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Purpose: Track structure Monte Carlo (MC) codes have achieved successful outcomes in the quantitative investigation of radiation-induced initial DNA damage. The aim of the present study is to extend a Geant4-DNA radiobiological application by incorporating a feature allowing for the prediction of DNA rejoining kinetics and corresponding cell surviving fraction along time after irradiation, for a Chinese hamster V79 cell line, which is one of the most popular and widely investigated cell lines in radiobiology. Methods: We implemented the Two-Lesion Kinetics (TLK) model, originally proposed by Stewart, which allows for simulations to calculate residual DNA damage and surviving fraction along time via the number of initial DNA damage and its complexity as inputs. Results: By optimizing the model parameters of the TLK model in accordance to the experimental data on V79, we were able to predict both DNA rejoining kinetics at low linear energy transfers (LET) and cell surviving fraction. Conclusion: This is the first study to demonstrate the implementation of both the cell surviving fraction and the DNA rejoining kinetics with the estimated initial DNA damage, in a realistic cell geometrical model simulated by full track structure MC simulations at DNA level and for various LET. These simulation and model make the link between mechanistic physical/chemical damage processes and these two specific biological endpoints.

Fluence, depth absorbed dose and linear energy transfer (LET) distributions of proton and carbon ion beams have been investigated using the Monte Carlo code Geant4 (GEometry ANd Tracking). An open source application was developed with the aim to simulate two typical transport beam lines, one used for ocular therapy and cell irradiations with protons and the other for cell irradiations with carbon ions. This tool allows evaluation of the primary and total dose averaged LET and predict their spatial distribution in voxelized or sliced geometries. In order to reproduce the LET distributions in a realistic way, and also the secondary particles' contributions due to nuclear interactions were considered in the computations. Pristine and spread-out Bragg peaks were taken into account both for proton and carbon ion beams, with the maximum energy of 62 MeV/n. Depth dose distributions were compared with experimental data, showing good agreement. Primary and total LET distributions were analysed in order to study the influence of contributions of secondary particles in regions at different depths. A non-negligible influence of high-LET components was found in the entrance channel for proton beams, determining the total dose averaged LET by the factor 3 higher than the primary one. A completely different situation was obtained for carbon ions. In this case, secondary particles mainly contributed in the tail that is after the peak. The results showed how the weight of light and heavy secondary ions can considerably influence the computation of LET depth distributions. This has an important role in the interpretation of results coming from radiobiological experiments and, therefore, in hadron treatment planning procedures.

Molecular targeted cancer therapy is a promising treatment strategy. Considering the central role of the epidermal growth factor receptor in cell proliferation and survival, there are indications that targeted agents like tyrosine kinase inhibitors, i. e., erlotinib, may enhance the antitumor treatment by radiation. The aim of this study is to analyze the inactivation effects of g-rays and to test the radiosensitizing potential of erlotinib on human lung adenocarcinoma cells in vitro. Irradiations were performed with doses ranging from 1 Gy to 8 Gy. In order to increase the radiosensitivity of CRL-5876 lung adenocarcinoma cells, the cells were treated with a clinically relevant concentration of 2 µM erlotinib. The effects of single and combined treatments were monitored using clonogenic survival, cell viability and proliferation assays at different time points. For the detection and visualization of the phosphorylated histone H2AX (γ-H2AX), an important biological marker of DNA double-strand break formation, fluorescence immunocytochemistry, was performed. The response to the treatment was monitored at four time points: 30 min, 2, 6, and 24 h. Irradiations with g-rays resulted in significant cell inactivation regarding all analyzed biological endpoints. Combined treatments revealed consistent cell inactivation. Moreover, compared to g-rays alone, elevated levels of g-H2AX foci were observed after pretreatment with erlotinib, indicating radiosensitization through impaired DNA repair. [Projekat Ministarstva nauke Republike Srbije, br. 173046 i br. 171019]

Geant4 is a software toolkit for the simulation of the passage of particles through matter. It is used by a large number of experiments and projects in a variety of application domains, including high energy physics, astrophysics and space science, medical physics and radiation protection. Over the past several years, major changes have been made to the toolkit in order to accommodate the needs of these user communities, and to efficiently exploit the growth of computing power made available by advances in technology. The adaptation of Geant4 to multithreading, advances in physics, detector modeling and visualization, extensions to the toolkit, including biasing and reverse Monte Carlo, and tools for physics and release validation are discussed here., Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 835, ISSN:0168-9002, ISSN:1872-9576

In order to contribute to the understanding of mechanisms by which regulatory proteins recognize genetic information stored in DNA, analyses of their interaction with specific nucleotides are usually performed. In this study, the electrophoretic mobility shift assay (EMSA) was applied to analyze the interaction of nuclear proteins from the liver of rats of different age i.e., young (3-month-old), middle- aged (12-month-old) and aged (24-month-old), with radioactively labelled synthetic oligonucleotide analogues, corresponding to GRE. The levels of GRE binding activity were assessed by quantitative densitometric scanning of the autoradiograms. The results showed statistically significant decreasing values of up to 78% and 49% in middle aged and old animals, respectively, compared to young animals (p < 0.05). The specificity of the nuclear proteins-GRE interaction was demonstrated by competition experiments with unlabelled GRE. In a supershift assay, using the antibody BuGR2, it was shown that the GR proteins present in nuclear extracts have a high affinity for the GRE probe. The stabilities of the protein-DNA complexes were analysed and it was concluded that they changed during ageing. .

In order to contribute to the understanding of mechanisms by which regulatory proteins recognize genetic information stored in DNA, analyses of their interaction with specific nucleotides are usually performed. In this study, the electrophoretic mobility shift assay (EMSA) was applied to analyze the interaction of nuclear proteins from the liver of rats of different age i.e., young (3-month-old), middle- aged (12-month-old) and aged (24-month-old), with radioactively labelled synthetic oligonucleotide analogues, corresponding to GRE. The levels of GRE binding activity were assessed by quantitative densitometric scanning of the autoradiograms. The results showed statistically significant decreasing values of up to 78% and 49% in middle aged and old animals, respectively, compared to young animals (p LT 0.05). The specificity of the nuclear proteins-GRE interaction was demonstrated by competition experiments with unlabelled GRE. In a supershift assay, using the antibody BuGR2, it was shown that the GR proteins present in nuclear extracts have a high affinity for the GRE probe. The stabilities of the protein-DNA complexes were analysed and it was concluded that they changed during ageing. U cilju doprinosa razumevanju mehanizama pomoću kojih regulatorni proteini prepoznaju genetičku informaciju koju nosi DNK, analiziraju se njihove interakcije sa specifičnim nukleotidima. U ovom radu je metodom EMSA analizirana interakcija jedarnih proteina iz jetri pacova iz tri starosne grupe (mladi - 3 meseca, srednje doba – 12 meseci i stari – 24 meseca) sa sintetičkim, radioaktivno obeleženim, oligonukleotidnim analogom GRE. Nivo vezujuće aktivnosti GRE je određivan kvantitativno denzitometrijskom autoradiografijom. Rezultati su pokazali da postoji statistički značajan pad vrednosti GRE-vezujuće aktivnosti do 78% kod životinja srednjeg starosnog doba i do 49 % kod starih životinja, u poređenju sa vrednostima dobijenim za mlade životinje (p LT 0.05). Specifičnost interakcije jedarnih proteina i GRE je određena eksperimentima kompeticije sa neobeleženim GRE. Korišćenjem antitela BuGR2 pokazano je da je glukokortikoidni receptor protein koji u jedarnom ekstraktu ima najveći afinitet za GRE probu. Analizirana je stabilnost kompleksa protein-DNK i zaključeno je da se menja tokom starenja.

To gain better insight into the role of glucocorticoids as modulators of cell growth, as well as to investigate the presence and characteristics of glucocorticoid receptors (GR) in mouse melanoma cells.In two different B16 mouse melanoma cell clones (B16/F10 and B16/C3) the role of synthetic glucocorticoids (triamcinolone acetonide, TA) as cell growth modulators was investigated.The inhibitory effect of TA on B16/F10 cell growth after 8 days in culture was observed. The same hormonal treatment applied on B16/C3 melanoma cells also provoked changes in the cell growth. Dot blot analysis, using monoclonal antirodent glucocorticoid receptor antibodies showed the presence of receptor protein in both cell clones. The analysis of glucocorticoid receptors in B16/F10 and B16/C3 cell cytosol by Scatchard assay and ion-exchange chromatography on DEAE-Sephadex A-50 minicolumn indicated that the changes in melanoma cell growth may be mediated by glucocorticoid receptors and may relieve changes in the GR itself.It was found that B16/C3 melanoma cells exhibited different growth pattern under TA treatment when compared to the results obtained with B16/F10 cells. Such differences may be mediated by glucocorticoid receptors.

ELI-Beamlines is one of the pillars of the pan-European project ELI (Extreme Light Infrastructure). It will be an ultra high-intensity, high repetition-rate, femtosecond laser facility whose main goal is generation and applications of high-brightness X-ray sources and accelerated charged particles in different fields. Particular care will be devoted to the potential applicability of laser-driven ion beams for medical treatments of tumors. Indeed, such kind of beams show very interesting peculiarities and, moreover, laser-driven based accelerators can really represent a competitive alternative to conventional machines since they are expected to be more compact in size and less expensive. The ELIMED project was launched thanks to a collaboration established between FZU-ASCR (ELI-Beamlines) and INFN-LNS researchers. Several European institutes have already shown a great interest in the project aiming to explore the possibility to use laser-driven ion (mostly proton) beams for several applications with a particular regard for medical ones. To reach the project goal several tasks need to be fulfilled, starting from the optimization of laser-target interaction to dosimetric studies at the irradiation point at the end of a proper designed transport beam-line. Researchers from LNS have already developed and successfully tested a high-dispersive power Thomson Parabola Spectrometer, which is the first prototype of a more performing device to be used within the ELIMED project. Also a Magnetic Selection System able to produce a small pencil beam out of a wide energy distribution of ions produced in laser-target interaction has been realized and some preliminary work for its testing and characterization is in progress. In this contribution the status of the project will be reported together with a short description of the of the features of device recently developed. Conference on Plasma Physics by Laser and Applications (PPLA), Oct 02-04, 2013, Univ Salento, Lecce, Italy