Untersuchung des Einflusses von Strahlung auf Normalgewebszellen des humanen Brustgewebes in vitro und in vivo

Die vorliegende Arbeit fokussierte sich auf die Fragestellung des karzinogenen Potentials von Photonenstrahlung im niedrigen und moderaten Dosisbereich (in vitro und in vivo) am Beispiel von Normalgewebszellen der humanen Brust. Die In-vivo-Experimente wurden zudem um diverse Neutronenqualitäten, hierbei hervorzuheben sind besonders die klinisch relevanten sekundär gestreuten Neutronen, erweitert.The present work focused on the question of the carcinogenic potential of photon radiation in the low and moderate dose range (in vitro and in vivo) using the example of normal tissue cells of the human breast. The in vivo experiments were also extended to include various neutron qualities, with particular emphasis on the clinically relevant secondary scattered neutrons

Simvastatin treatment varies the radiation response of human breast cells in 2D or 3D culture

Background Statins inhibit the cholesterol biosynthesis and are used as cholesterol-lowering agents in fat-metabolism disorders. Furthermore, several studies state that statins have supportive functions in breast cancer treatment. Therefore, simvastatin (SVA) as a potential radiosensitizer should be investigated on the basis of human breast cells. Methods First, an optimal concentration of SVA for normal (MCF10A) and cancer (MCF-7) cells was identified via growth and cytotoxicity assays that, according to the definition of a radiosensitizer in the narrower sense, enhances the effect of radiation therapy but has no cytotoxic effect. Next, in combination with radiation SVA's influence on DNA repair capacity and clonogenic survival in 2D and 3D was determined. Furthermore cell cycle distribution, expression of survivin and connective tissue growth factor (CTGF) as well as ERK1 map kinase were analysed. Results 1 μM SVA was identified as highest concentration without an influence on cell growth and cytotoxicity and was used for further analyses. In terms of early and residual γH2AX-foci, SVA affected the number of foci in both cell lines with or without irradiation. Different radiation responses were detected in 2D and 3D culture conditions. During the 2D cultivation, a radiosensitizing effect within the clonogenic survival was observable, but not in 3D. Conclusion The present study suggests that SVA may have potential for radiosensitization. Therefore, it is important to further investigate the role of SVA in relation to the extent of radiosensitization and how it could be used to positively influence the therapy of breast cancer or other entities

Radiation Sensitivity of Adipose-Derived Stem Cells Isolated from Breast Tissue

Within their niche, adipose-derived stem cells (ADSCs) are essential for homeostasis as well as for regeneration. Therefore, the interest of physicians is to use ADSCs as a tool for radiation oncology and regenerative medicine. To investigate related risks, this study analyses the radiation response of adult stem cells isolated from the adipose tissue of the female breast. To avoid donor-specific effects, ADSCs isolated from breast reduction mammoplasties of 10 donors were pooled and used for the radiobiological analysis. The clonogenic survival fraction assay was used to classify the radiation sensitivity in comparison to a more radiation-sensitive (ZR-75-1), moderately sensitive (MCF-7), and resistant (MCF10A) cell lines. Afterwards, cytotoxicity and genotoxicity of irradiation on ADSCs were investigated. On the basis of clonogenic cell survival rates of ADSCs after irradiation, we assign ADSCs an intermediate radiation sensitivity. Furthermore, a high repair capacity of double-strand breaks is related to an altered cell cycle arrest and increased expression of cyclin-dependent kinase (CDK) inhibitor p21. ADSCs isolated from breast tissue exhibit intermediate radiation sensitivity, caused by functional repair mechanisms. Therefore, we propose ADSCs to be a promising tool in radiation oncology

Comparative study of the effects of different radiation qualities on normal human breast cells

BACKGROUND: As there is a growing number of long-term cancer survivors, the incidence of carcinogenesis as a late effect of radiotherapy is getting more and more into the focus. The risk for the development of secondary malignant neoplasms might be significantly increased due to exposure of healthy tissue outside of the target field to secondary neutrons, in particular in proton therapy. Thus far, the radiobiological effects of these neutrons and a comparison with photons on normal breast cells have not been sufficiently characterised. METHODS: MCF10A cells were irradiated with doses of up to 2 Gy with neutrons of different energy spectra and X-rays for comparison. The biological effects of neutrons with a broad energy distribution ( = 5.8 MeV), monoenergetic neutrons (1.2 MeV, 0.56 MeV) and of the mixed field of gamma's and secondary neutrons ( = 70.5 MeV) produced by 190 MeV protons impinging on a water phantom, were analysed. The clonogenic survival and the DNA repair capacity were determined and values of relative biological effectiveness were compared. Furthermore, the influence of radiation on the sphere formation was observed to examine the radiation response of the potential fraction of stem like cells within the MCF10A cell population. RESULTS: X-rays and neutrons caused dose-dependent decreases of survival fractions after irradiations with up to 2 Gy. Monoenergetic neutrons with an energy of 0.56 MeV had a higher effectiveness on the survival fraction with respect to neutrons with higher energies and to the mixed gamma - secondary neutron field induced by proton interactions in water. Similar effects were observed for the DNA repair capacity after exposure to ionising radiation (IR). Both experimental endpoints provided comparable values of the relative biological effectiveness. Significant changes in the sphere formation were notable following the various radiation qualities. CONCLUSION: The present study compared the radiation response of MCF10A cells after IR with neutrons and photons. For the first time it was shown that monoenergetic neutrons with energies around 1 MeV have stronger radiobiological effects on normal human breast cells with respect to X rays, to neutrons with a broad energy distribution ( = 5.8 MeV), and to the mixed gamma - secondary neutron field given by interactions of 190 MeV protons in water. The results of the present study are highly relevant for further investigations of radiation-induced carcinogenesis and are very important in perspective for a better risk assessment after secondary neutron exposure in the field of conventional and proton radiotherapy