ESTRO 2022 - Abstract Book

S520

Abstract book

ESTRO 2022

TCGA analysis revealed higher expression of CAF associated markers in HNSCC samples compared to normal tissue samples ( Fig.1A ) and higher expression in HPV- compared to HPV+ patients ( Fig.1B ). After RT, HNSCC-derived CAFs increase their cell size ( Fig.1C,D ), modulate expression of CAF-associated ( Fig1E,F ) and immune modulatory markers ( Fig.1G ). Our first results on patient-derived CAFs confirm that also human HNSCC derived CAFs are affected by RT ( Fig.1H,I ).

Fig.1 Radiotherapy affects HNSCC derived CAFs A) Expression in HNSCC tissues vs normal tissues B) Expression in HPV- and HPV+ HNSCC. CAFs from HNSCC patient-derived xenografts were irradiated and 3 days later stained for microscopy ( α SMA (magenta), DAPI (blue) and total actin (green)). C. Cell surface area was determined with ImageJ D) The dots represent the mean cell area per HNSCC-derived CAF E) qPCR analysis, 3 days after irradiation F) FACS analysis 3 days after irradiation G) FACS analysis, 3 days after irradiation. H) CAFs isolated from HNSCC patients were subjected to radiation, 3 days later their cell area was determined with microscopy followed by ImageJ analysis. Each dot represents a cell, with mean and SD indicated. I) FACS analysis, 3 days after irradiation. Conclusion Our in silico analyses confirm the significant presence of CAFs in HNSCC, suggesting that CAFs contribute to the malignant phenotype of HNSCC. Our data show that RT modulates the phenotype of murine and human HNSCC-derived CAFs. It affects their morphology and the expression of markers that are important in steering anti-tumor responses. Current research focuses on the effect of RT on the function of CAFs in vivo and their subsequent effect to modulate the anti-tumour immune response and efficacy of immunotherapy.

OC-0595 Human mesenchymal stromal cells increase glioblastoma radioresistance by cellular networks

M. Strack 1 , A. Rühle 1 , D.H. Heiland 2 , O. Schnell 2 , A. Grosu 1 , N.H. Nicolay 1

1 University Medical Center Freiburg, Department of Radiation Oncology, Freiburg, Germany; 2 University Medical Center Freiburg, Department of Neurosurgery, Freiburg, Germany Purpose or Objective Previous studies have identified the presence of multipotent mesenchymal stromal cells (MSCs) in the glioblastoma (GBM) microenvironment as an adverse feature regarding patient survival. We aimed to analyze whether MSCs contribute to the poor radiation response of glioblastoma cells (GBCs). Materials and Methods An immortalized GBM cell line (U251) and two primary GBCs, isolated from surgical samples of a primary and a recurrent GBM, were directly co-cultured with human bone-marrow derived MSCs from three different donors to model intercellular interactions in vitro . To examine the influence of MSCs on the radiosensitivity of GBCs, colony forming, proliferation and metabolic viability assays were performed. A modified Boyden chamber migration assay was carried out to investigate whether radiotherapy can mitigate the GBCs’ ability to chemotactically attract MSCs. Cell cycle distribution and levels of cleaved caspase-3 were quantified by flow cytometry after irradiation with 2 und 4Gy, and the expression and localization of the radioresistance-related Growth Associated Protein 43 (GAP43) was analyzed based on immunofluorescence stainings. An siRNA-based knockdown was established in GBCs to evaluate whether GAP43- silencing may attenuate MSC-associated radioprotection.

Results