ESTRO 38 Abstract book

S595 ESTRO 38

and increased in MI-773 treated cells further linking p53 and PlGF. In order to investigate the paracrine effect of PlGF, we have developed PlGF knock out cells using a CRISPR-Cas9 approach. These cells will be used for in vitro and in vivo experiments to study the paracrine effect of IR-induced PlGF secretion on tumor and endothelial cells and for tumor radiosensitivity. Conclusion In conclusion, PlGF, which has so far not been investigated in response to IR, might play a relevant role for the radiation response on the level of tumor angiogenesis. PO-1071 RIBE alters biological properties of the wound fluids K. Kulcenty 1 , I. Piotrowski 2 , D. Murawa 3 , W. Suchorska 2 1 Poznan University of Medical Sciences- Greater Poland Cancer Centre, Department of Electroradiology- Radiobiology Lab, Poznan, Poland ; 2 University of Medical Sciences- Greater Poland Cancer Centre, Department of Electroradiology- Radiobiology Laboratory, Poznań, Poland ; 3 Poland Baptism Monument Hospital, Department of General and Minimally Invasive Surgery, Gniezno, Poland Purpose or Objective After breast cancer surgery, more than 90% of local recurrences occur in the same quadrant as the primary cancer. Wound fluids (WF) are believed to play a role in this process by inducing an inflammatory process in the scar tissue area. Given that most local relapse occur within the scar tissue area, researchers have investigated whether localized radiotherapy, such as intraoperative radiotherapy (IORT), could be more effective than postoperative RT in inhibiting local tumor recurrence. Despite the availability of strong clinical data demonstrating the benefits of IORT, the biological basis underlying this process is still not well- understood. It is known that ionizing radiation (IR) directly affects the cells by damaging DNA and consequently changing the phenotype of the cell. In addition to a direct action, the effect of IR may also be observed in cells that were not irradiated, but were in a close proximity to irradiated cells – a phenomenon called radiation induced bystander effect (RIBE). It was also showed that RIBE significantly modifies the tumor microenvironment. Given this background we assume that postoperative fluid from patients after intraoperative radiation therapy acts through bystander effect (RIBE, radiation induced bystander effect) that induces the radiobiological response in unirradiated cells and modify their phenotype. Material and Methods To confirm this hypothesis, WF collected from patients after breast conserving surgery (BCS) alone (WF) (i.e., without IORT), after BCS followed by IORT treatment (RT- WF) or WF from BCS patients together with conditioned medium from irradiated cells (WF+RIBE) were incubated with MDA-MB-468 cells. Using microarray analysis we compared cells incubated with collected fluids. The GSEA analysis was performed to demonstrate biological processes characteristic for treated cells. RT-qPCR and flow cytometry analysis were used to confirm obtained The microarray analysis of wound fluids stimulated MDA- MB-468 cells indicated common biological processes for RT-WF and WF+RIBE group. Overrepresentation of processes involved in cell cycle regulation, DNA repair and oxidative phosphorylation was observed in RT-WF and WF+RIBE group while WF group was characterized by overrepresentation of pathways involved in INF-α response, INF-γ response, inflammatory response and IL6 JAK/STAT3 signaling pathway. results. Results

quality (i.e. particle type and energy), is an adjustable parameter; the probability that a chromosome fragment remains unrejoined, which depends on cell type but is independent of radiation quality and thus can be adjusted basing on photon data, is the second parameter. Results Up to now, the model has been tested against experimental data on V79 cells and AG01522 cells exposed to protons, C-ions and He-ions of different energy, as well as photons for comparison. The good agreement between simulations and data allowed validating the model; furthermore, a database of CL yields was produced that allows predicting cell survival curves for different ions, in principle for any LET value. By fitting these curves, tables of alpha and beta coefficients were produced for different ion types and energies for both considered cell types, and the corresponding RBE were calculated. The RBE values predicted this way were in good agreeement with experimental data taken from the literature, Since these tables can be read by a radiation transport codes, an interface was developed between BIANCA and FLUKA, which allows producing “biological” profiles for hadrontherapy beams. Conclusion These results show that BIANCA can produce RBE values to be used in hadrontherapy. PO-1070 Identification of biologically active factors in ionizing radiation regulated secretome M. Pruschy 1 1 University of Zurich, Applied Radiobiology, Zurich, Switzerland Purpose or Objective Ionizing radiation (IR) leads to DNA damage and genome instability. In addition, IR also leads to stress responses in tumor cells by activating signal transduction pathways and inducing secretion of numerous auto- and paracrine factors. As part of an exhaustive IR-dependent secretome analysis, which was previously performed in our laboratory, placental growth factor (PlGF) was identified to be secreted in response to IR. It is a homodimeric protein, belongs to vascular endothelial growth factor (VEGF)-family and binds to VEGFR1. PlGF expression is low to undetectable in most tissues in healthy subjects, but becomes significantly upregulated in disease. Material and Methods PlGF expression and secretion were analyzed across multiple cancer cell lines and at different time points after irradiation with increasing doses of IR (0, 5 and 10Gy) by qRT-PCR and ELISA, respectively. Two medulloblastoma cell lines (p53 wildtype vs. p53-mutated) were chosen for further experiments with siRNA and the HIF1-alpha inhibitor BAY 87-2243 under normoxic and hypoxic (1% O 2 ) conditions to investigate the downstream targets of BAY 87-2243. Results PlGF expression and secretion was already upregulated at 4h and 24h, respectively, in p53 wild-type cancer cells. Interestingly, only minimal or delayed PLGF expression could be detected in p53-mutated cell lines. PlGF is also upregulated under hypoxic condition. Therefore, cells were treated with the HIF1-alpha inhibitor BAY 87-2243 under normoxic and hypoxic condition (1% O 2 ). Interestingly, BAY 87-2243 attenuated PlGF-secretion only in p53-mutated cells. These results suggest that PlGF is differentially regulated by either p53 or HIF1-alpha. To further link p53 and PlGF, p53 wildtype cells were treated with p53 inhibitor Pifithrin-α or MDM-2 inhibitor MI-773. PlGF secretion was decreased after Pifithrin treatment Poster: Radiobiology track: Radiation-induced signalling pathways