ESTRO 37 Abstract book

ESTRO 37

S588

Purpose or Objective Radiotherapy (RT) induces DNA-damage that either causes induction of tumor cell death or inhibition of the proliferating capacity of these cells. Furthermore, considerable evidence emerges that antineoplastic effects extend beyond these mechanisms. Those secondary effects contribute to anti-tumor responses in a local but also systemic manner via activation of the immune system: The role of dendritic cells (DCs) is well described to be essential for priming effective radiation- induced adaptive immunity. Through increased release of tumor-associated antigens (TAA) after RT, DCs are recruited and cross-presentation of TAA leads to activation of B- and T-lymphocytes, therefore playing a pivotal role in adaptive immune response and immunogenic cell death. However, there are still many hypotheses regarding the influence of RT on activation of the immune system. The aim of our experiments is to further characterize the impact of different radiation types and dosages on differentiation and functionality of DCs. Material and Methods Human CD14-positive monocytes were isolated from peripheral blood mononuclear cell samples. After cytokine stimulation with Interleukin-4 (IL-4) and granulocyte macrophage colony-stimulating factor (GM- CSF) monocytes were induced into immature DCs (iDCs) and later mature DCs (mDCs). Monocytes were irradiated with different radiation doses (1x15Gy, 5x2Gy, 1x0.5Gy) and radiation types (photons, protons, carbon ions) on day 0. Maturation to mDCs was induced on day 7 by adding tumor necrosis factor alpha (TNFα) to the culture medium. Differentiation and maturation of DCs was assessed by staining of cell surface molecules CD14, CD83, CD80, CD86, CD209 und HLA-DR via flow cytometry. Functional analysis of irradiated DCs was performed through FITC-labelled phagocytosis assay, migrational assays and IL-12 ELISA. Results No major significant changes in the immune profile during differentiation of monocytes (CD14 + , CD83 - , CD86 + , CD80 - , HLA-DR + ) into iDCs (CD83 - , CD86 - , CD80 - , HLA-DR + ) and mDCs (CD83 + , CD86 + , CD80 + , HLA-DR ++ ) were seen after treatment with different radiation doses and types compared to the untreated control group. Functional analysis showed no difference in the phagocytotic and IL- 12 secretion capacity of irradiated iDCs and mDCs compared to the control group, whereas migrational capacity was induced after proton irradiation, compared to the other irradiation types. Conclusion Our experiments reveal that after irradiation with different doses and types maturation of DCs was unchanged compared to the control group. The capability for phagocytosis was unaffected after irradiation of DCs, indicating persistent functionality of the immune system. An additional RT-induced effect of particle therapy on the immunogenic potential of DCs is possible due an increase of IL-12 secretion and migrational capacity and will be investigated further. PO-1046 Dose-dependent changes after proton and photon irradiation in zebrafish model S. Brunner 1 , T. Tokes 1 , R. Szabo 1 , Z. Szabo 1 , R. Polanek 1 , E. Beyreuther 2 , J. Pawelke 3 , K. Hideghety 4 1 ELI-ALPS- ELI-HU Non-Profit Ltd, Szeged, Hungary 2 Helmholtz-Zentrum Dresden- 3OncoRay– National Center for Radiation Research in Oncology Faculty of Medicine and University Hospital Carl Gustav Carus- Technische

Universität, Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Uni, 3 Helmholtz-Zentrum Dresden- 3OncoRay – National Center for Radiation Research in Oncology- Faculty of Medicine and University Hospital Carl Gustav Carus- Technische Universität Dresden, Faculty of Medicine and University Hospital Carl Gustav Carus- Tech, 4 ELI-ALPS- ELI-HU Non-Profit Ltd, Department of Oncotherapy- Szeged- Hungary-, Szeged, Hungary Purpose or Objective The laser-driven ionizing (LDI) beams have unique property of ultra-high dose rate, ultra-short pulses and carry the potential toward special clinical application. Our aim was to establish an in vivo zebrafish model for radiobiological research on later LDI radiation. Material and Methods 24 hours post-fertilization (hpf) zebrafish (Danio rerio) embryos were irradiated at OncoRay Institution, Dresden with escalated doses (5, 10, 15, 20 and 30 Gy) at two positions along the proton depth-dose curve (PDDC): at the plateau and at the middle of Spread Out Bragg Peak (mSOBP), furthermore, with reference conventional photon beam (n=96 in each group). The experiment were 3 times repeated, under the same conditions. On the 3 th (96 hpf) and 4 th (120 hpf) days after irradiation morphological malformations were documented (photo) and determined quantitatively. Two independent observers measured the length of the embryos, the degree of the yolk sac edema and the diameter of the eyes. Additionally, we have detected the DNA double- strand breaks immunohistochemically (gamma-H2AX) after 30 min of the irradiation at the two positions of the proton (mSOBP and plateau) and photon beams, at 5 Gy dose level. Results Dose-dependent organ developmental deteriorations could be detected morphologically at >10 Gy dose levels. The length of the embryo and the size of the eyes reduced, while the yolk sac edema increased significantly in dose dependent degree after 10 Gy, 15 Gy, 20 Gy and 30 Gy irradiation at both developmental stages. At 5 Gy dose irradiation we have found significant elevation in the number of DNA double-strand breaks, as compared to the control groups. Furthermore, data showed that after proton irradiation the degree of the DNA damage was higher, as compared to the photon irradiation. Conclusion We could establish a reliable quantitative morphological analysis of dose-dependent organ malformations using an in vivo vertebrate system. The zebrafish embryo model proved to be appropriate for complex evaluation of the irradiation-caused damages, molecular changes and for comparison of the biological effects of different radiation qualities. We could define the most optimal parameters for later radiobiological experiments with the LDI beams. Supported by : The ELI-ALPS project (GINOP-2.3.6-15- 2015-00001) is supported by the European Union and co- financed by the European Regional Development Fund, and by the German BMBF, grant nos. 03ZIK445 and 03Z1N511. The project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no 654148 Laserlab- Europe. PO-1047 Cellular responses to focused low LET proton irradiation K. Ilicic 1 , C. Greubel 2 , D. Walsh 2 , J. Reindl 2 , S. Girst 2 , C. Siebenwirth 2 , M. Sammer 2 , B. Schwarz 2 , S. Combs 1 , G.