ESTRO 2022 - Abstract Book

S519

Abstract book

ESTRO 2022

Conclusion OXPHOS inhibition decreases oxygen consumption in several tumor cell lines in vitro and decreases diffusion limited hypoxia in vivo. Furthermore, the hypoxia related marker CAIX can be used to visualize hypoxic areas in syngeneic mouse models using the SPECT-radiotracer [In 111 ]-DTPA-mCAIX. In the future, this technique could be used to distinguish hypoxic from non-hypoxic tumors before or during OXPHOS inhibition treatment and thereby help optimizing this strategy to relieve tumor hypoxia and improve immuno- and radiotherapy efficacy in preclinical models.

OC-0594 Head and Neck Squamous Cell Carcinoma derived CAFs alter their phenotype after ionizing radation

M. Ansems 1 , V. Mekers 1 , A. Beerkens 2 , M. Dotinga 1 , K. Strepi 2 , J. Honings 3 , W. Weijs 4 , G.J. Adema 1 , J.H. Kaanders 1 , J. Bussink 2 1 Radboudumc, Radiation Oncology, Nijmegen, The Netherlands; 2 Radboudumc, Radiation Oncology, Nijmegen , The Netherlands; 3 Radboudumc, Otorhinolaryngology-Head and Neck Surgery, Nijmegen, The Netherlands; 4 Radboudumc, Oral and Maxillofacial Surgery, Nijmegen, The Netherlands Purpose or Objective Despite advances in treatment strategies of Head and Neck Squamous Cell Carcinoma (HNSCC), the chance of cure for recurrent HNSCC is poor. To increase the success rate of treatment strategies more knowledge regarding the interplay between cancer cells and other cell types in the tumour is essential. In particular cancer associated fibroblasts (CAFs) require special attention, since they make up the majority of cells in the tumour microenvironment of HNSCC. Currently, the majority of HNSCC patients will be treated with radiotherapy (RT). Despite the abundance of CAFs, the effect of RT on their function in HNSCC is largely unknown. Materials and Methods The significance of CAFs in HNSCC was analysed using the TCGA database. The expression of CAF associated markers in HNSCC samples was compared to the expression in normal tissue samples and in HPV+ vs HPV- patients. The impact of ionizing radiation on murine and human HNSCC-derived CAFs was determined by RNA, flow cytometry and microscopic analyses.

Results