ESTRO 38 Abstract book

S188 ESTRO 38

Purpose or Objective Type I interferon (IFN-I) and IL-22 modulate regeneration of the thymus and intestinal epithelial cells (IECs) after cytotoxic stress like irradiation. Radiation-induced damage to thymic tissues and IECs is a crucial aspect during the pathogenesis of inadequate immune reconstitution and acute graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT) with myeloablative total body irradiation (TBI), respectively. IL-22 and IFN-I reduce severity of acute GVHD after allo-HSCT with myeloablative TBI. However, the role of biologically related type III interferon (IFN-III), also known as interferon lambda (IFN- λ) or IL-28, in this context is unclear. We therefore studied the role of the IFN-III pathway in thymic regeneration and GVHD after TBI and allo-HSCT. Material and Methods Co-housed wild-type (WT) and IFN-III receptor-deficient (IL-28 receptor-alpha-deficient/IL-28Ra -/- ) mice were analyzed in models of TBI-induced thymus damage and a model of GVHD after allo-HSCT with myeloablative TBI. PASylated IFN-III (PASylated IL-28A) was generated to prolong plasma half-life of IFN-III. Pharmacological activity and effects of PASylated IL-28A on radiation- induced thymus damage and the course of GVHD after allo- HSCT with myeloablative TBI were tested. Results Course and severity of GVHD after myeloablative TBI and allo-HSCT in IL-28 receptor-alpha-deficient mice were comparable and not significantly different comparedto WT mice. Also, activation of the IFN-III pathway with PASylated IL-28A did not significantly modulate GVHD after allo-HSCT with TBI. Furthermore, IL28Ra -/- mice and WT mice showed similar thymus regeneration after radiation, which could also not be significantly modulated by IFN-III receptor activation using PASylated IL-28A. Conclusion We have analyzed the role of IFN-III signaling during radiation-mediated acute tissue injury. We found that despite molecular and biological homologies with IFN-I and IL-22, IFN-III signaling did not regulate thymus regeneration after irradiation or the course of GVHD after myeloablative TBI and allo-HSCT. OC-0379 Radiation response mechanisms of mesenchymal stem cells in dependence on their tissue of origin N. Nicolay 1,2 , A. Rühle 2 , R. Lopez Perez 2 , R. Saffrich 3 , S. Sisombath 2 , T. Trinh 4 , J. Debus 4,5 , P.E. Huber 2,4 1 University of Freiburg Medical Center, Radiation Oncology, Freiburg, Germany ; 2 German Cancer Research Center, Molecular Radiation Oncology, Heidelberg, Germany ; 3 German Red Cross Blood Donor Service, Transfusion Medicine and Immunology, Mannheim, Germany ; 4 Heidelberg University Hospital, Radiation Oncology, Heidelberg, Germany ; 5 German Cancer Research Center, Clinical Cooperation Unit Radiation Oncology, Heidelberg, Germany Purpose or Objective Human mesenchymal stem cells (MSCs) aid the regeneration of tissue damage caused by ionizing radiation (IR), and early clinical results indicate a potential of MSC- based therapies for the treatment of IR-induced toxicities. While MSCs can be harvested from different tissues, the influence of the tissue source on the radiation response of MSCs remains largely unknown. Material and Methods Human MSCs were harvested from adipose tissue (adMSCs), bone marrow (bmMSCs) and umbilical cord Wharton’s jelly (wjMSCs) from 9 voluntary donors and characterized according to the established defining criteria: Cellular adhesion was measured, and multi- lineage differentiation was assessed after IR. Proliferation and survival of MSCs were examined after IR, and IR-

Purpose or Objective Mitochondria are structures within eukaryotic cells having their own genome. The mtDNA encodes for structural subunits of the OXPHOS chain, rRNAs and tRNAs. Although, variations in the mtDNA are very common (every individual carries variations), mtDNA variations can potentially lead to a stress-induced decrease in mitochondrial function. The main functions of mitochondria are ATP and ROS production, molecular properties important for radiotherapy (RT), suggesting that there is a role for mtDNA variations in RT response. We hypothesize that mtDNA variants are associated with RT response, and influence the DNA damage/repair capacity and/or induced ROS damage. Material and Methods Patient study: Random forest modeling has been shown to perform well in situations where there are large numbers of predictor variables with complex interactions. We used this method to study the association between mtDNA variations of lung cancer patients and their dyspnea score as an outcome of radiation-induced lung toxicity (RILT). In our analysis, 137 patients with 3-month dyspnea score of 0 were marked to be not sensitive to RT and 41 patients with a change of at least 2 in the dyspnea score (3-month vs baseline) were marked as radiosensitive. In vitro study: Primary fibroblasts were obtained from either healthy controls or mitochondrial patients, with a m.11778G>A mutation causative for a mild phenotype mitochondrial disease. Assays were performed using galactose containing medium in order to exhibit the mitochondrial phenotype of the cell lines. Results Here, we performed a number of modeling efforts where each time we restricted the features to only a chosen subset of all mtDNA variants. We used a three-fold cross- validation (CV) on our data set and repeated the CV 100 times with random shuffling. We found predictive value when we restricted the features to all tRNA and rRNA variants together with the non-synonymous variants that: 1. are on genes COI, COII, COIII, and CYBT (AUC = 0.61±0.04) 2. are at positions that are at least 50% conserved (AUC = 0.59±0.04) In our proof-of-concept study, trends in mitochondrial metabolism show that less mitochondrial spare capacity was present for the m.11778 G>A cells compared to the controls. Additionally, preliminary results show an upregulation of RT stress-induced genes ( NFKB , NRF2 ). DNA damage (yH2AX foci) and apoptosis (cleaved PARP) were increased, although this needs to be further validated; also other stress response pathways are currently explored. Conclusion Our data showed that mtDNA variation could be a valuable biomarker for RILT. Furthermore, we have preliminary data indicating that RT-induced stress response pathways are differently expressed in cells with a mild mtDNA phenotype. OC-0378 Regeneration after radiation and T cell- induced tissue injury is not enhanced by type III interferon J. fischer 1 , C. Lin 2 , S. Heidegger 2 , A. Wintges 2 , M. Schlapschy 3 , M. Beudert 3 , S.E. Combs 1 , F. Bassermann 2 , A. Skerra 3 , T. Haas 2 , H. Poeck 2 1 Klinikum rechts der Isar- Technische Universität München, Department of Radiation Oncology, Munich, Germany; 2 Klinikum rechts der Isar- Technische Universität München, Klinik und Poliklinik für Innere Medizin III, Munich, Germany; 3 Technische Universität München, Munich Center for Integrated Protein Science CIPS-M and Lehrstuhl für Biologische Chemie, Freising, Germany