ESTRO 2022 - Abstract Book

S114

Abstract book

ESTRO 2022

differences were found in mouse weight or any of the haematological and biochemical markers analysed, suggesting that the combination of atovaquone and anti-PD-L1 was not associated with toxicity. Conclusion Atovaquone synergises with anti-PD-L1, favouring the development of a memory anti-tumour immune response, and without causing any toxicity. Our results support future testing of atovaquone in combination with immune checkpoint blockade and radiotherapy.

MO-0138 cGAS localization to micronuclei is dictated by nuclear chromatin status pre-DNA damage

S. Harding 1 , K. MacDonald 2 , S. Nicholson 1 , M. Tageldein 2 , C. Arrowsmith 1,3

1 Princess Margaret Cancer Centre, University Health Network, Toronto, Canada; 2 University of Toronto, Medical Biophysics, Toronto, Canada; 3 Structural Genomics Consortium, University of Toronto, Toronto, Canada Purpose or Objective Micronuclei (MN) are small DNA structures in the cytoplasm that arise from DNA fragments or whole chromosomes that remain distinct from the main nucleus after DNA damage. Recent evidence has found that MN can become repositories for the pattern recognition receptor cyclic GMP-AMP synthase (cGAS) that drives activation of stimulator of interferon genes (STING) and cytokine signalling. Despite their recognized importance to radiobiology few studies have focused on the functional properties of MN and their role as organizing centres of cellular signalling. In this work we explore molecular features of MN that emerge from different forms of DNA damage, especially ionizing radiation, and ask how these features associate with cGAS recruitment and activation of cytokine transcription. Materials and Methods Using established cell lines (MCF10A, HeLa-S3 and U2OS) treated with multiple DNA damaging agents (ionizing radiation (IR), methyl methanesulfonate, hydroxyurea, etc.) we profile cGAS recruitment and transcription in MN using immunofluorescence. In a small molecule screen, we ask how histone modifying enzymes influence MN properties and the recruitment of cGAS to MN. Results We find that heterogeneous recruitment of cGAS to MN is determined by the type of DNA damage that leads to MN formation. Rupture of the MN envelope is necessary but not sufficient for recruitment of cytosolic cGAS. Instead, we find that nuclear chromatin status at the time of DNA damage induction and MN formation is a primary determinant of cGAS localization and subsequent cytokine signalling through the cGAS-STING pathway. Conclusion DNA damage induced MN are not monolithic. Heterogeneity in MN properties emerges because of the nuclear chromatin state at the time of DNA damage. Together our findings begin to uncover the unique place of MN in cellular signalling and argue for their role as central integrators of the cellular response to DNA damages. 1 German Cancer Research Center (DKFZ), Heidelberg, Germany, German Cancer Consortium (DKTK), partner site Dresden, Dresden, Germany; 2 OncoRay – National Center for Radiation Research in Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Helmholtz-Zentrum Dresden - Rossendorf, Dresden, Germany; 3 Department of Radiotherapy and Radiation Oncology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany; 4 National Center for Tumor Diseases (NCT), Partner Site Dresden, Germany: German Cancer Research Center (DKFZ), Heidelberg, Germany, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany, and Helmholtz Association / Helmholtz-Zentrum Dresden - Rossendorf (HZDR), Dresden, Germany; 5 Institute of Pathology, Faculty of Medicine and University Hospital Carl Gustav Carus,Technische Universität Dresden, Dresden, Germany; 6 Department of Otorhinolaryngology, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany; 7 Department of Oral and Maxillofacial Surgery, Faculty of Medicine and University Hospital Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany; 8 German Cancer Research Center (DKFZ), Heidelberg, Germany, German Cancer Consortium (DKTK), partner site Berlin, Berlin, Germany; 9 Charité University Medicine Berlin, Department of Radiooncology and Radiotherapy, Berlin, Germany; 10 German Cancer Research Center (DKFZ), Heidelberg, Germany, German Cancer Consortium (DKTK), partner site Essen, Essen, Germany; 11 Department of Radiation Therapy, University Hospital, Medical Faculty, University of Duisburg-Essen, Essen, Germany; 12 German Cancer Research Center (DKFZ), Heidelberg, Germany, German Cancer Consortium (DKTK), partner site Frankfurt, Frankfurt, Germany; 13 Department of Radiotherapy and Oncology, Goethe-University Frankfurt, Frankfurt, Germany; 14 German Cancer Research Center (DKFZ), Heidelberg, Germany, German Cancer Consortium (DKTK), partner site Freiburg, Freiburg, Germany; 15 Department of Radiation Oncology, Medical Center, Medical Faculty, University of Freiburg, Freiburg, Germany; 16 German Cancer Research Center (DKFZ), Heidelberg, Germany, German Cancer Consortium (DKTK), partner site Heidelberg, Heidelberg, Germany; MO-0139 PORT-C improves LRC in a subset of patients with intermediate-risk HNSCC: A matched pair analysis S. Patil 1,2 , A. Linge 1,2,3,4 , H. Hiepe 1,2,3 , M. Grosser 5 , F. Lohaus 1,2,3,4 , V. Gudziol 4,6 , A. Nowak 4,7 , I. Tinhofer 8,9 , V. Budach 8,9 , M. Guberina 10,11 , M. Stuschke 10,11 , P. Balermpas 12,13 , C. Rödel 12,13 , H. Schäfer 14,15 , A. Grosu 14,15 , A. Abdollahi 16,17,18,19,20 , J. Debus 16,17,18,19,21 , C. Belka 22,23,24 , S. Pigorsch 22,25 , S.E. Combs 22,25,26 , S. Boeke 27,28 , D. Zips 27,28 , M. Baumann 1,2,3 , M. Krause 1,2,3,4 , S. Löck 1,2,3,4