ESTRO 2024 - Abstract Book

S5222

Radiobiology - Microenvironment

ESTRO 2024

Hala Awada 1,2 , Charlotte Degorre 1 , Anne Christin Parplys 3,4 , Ophélie Renoult 1 , Kerstin Borgman 3 , Laure Sabatier 5 , Claire Pecqueur 1 , François Paris 1,6 1 Nantes Université, CRCI2NA, INSERM, CNRS, F-44000, Nantes, France. 2 Anti-Tumor Therapeutic Targeting Laboratory, Faculty of Sciences, Lebanese University, Beirut, Hadath, Lebanon. 3 Laboratory of Radiobiology & Experimental Radiooncology, Department of Radiotherapy and Radiation Oncology, Centre of Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany. 4 Department Viral Zoonoses - One Health, Heinrich Pette Institute, Leibniz Institute for Experimental Virology, Hamburg, Germany. 5 Fundamental Research Division, PROCyTox, French Alternative Energies and Atomic Energy Commission (CEA), Paris-Saclay University, Fontenay-aux-roses, France. 6 Institut de Cancérologie de l'Ouest, 44800, Saint-Herblain, France Radiation therapy (RT) remains the mainstay of glioblastoma (GBM) treatment combined with surgery and concomitant or adjuvant Temozolomide chemotherapy. However, despite aggressive treatment, all GBM recur within a year at the primary irradiated site of the tumor (1). This is commonly explained by radioresistant residual GBM cells (2), yet the potential role of irradiated tumor microenvironment in this process remains unexplored. Notably, various RT-induced changes in stroma cells, including senescence, are increasingly described as modulators of the tumor response (3). Senescence is a cellular aging process characterized by terminal cell cycle arrest and hypersecretory phenotype, called SASP (4). Interestingly, senescent endothelial cells were detected in GBM patient biopsies at recurrence (5) but their involvement in tumor behavior remains unknown. Here, we investigated the potential impact of radiation-induced senescent (RIS) endothelial cells on GBM cells treated by RT. Purpose/Objective:

Material/Methods:

Murine GBM GL261 cells were engrafted in mouse brain with or without a previous stereotactic whole brain irradiation. To demonstrate the presence of radiation-induced senescent endothelial cells, immunostainings for senescence markers and endothelial cells were done on mouse brains sections two months post irradiation. Besides, human microvascular endothelial cells (HMVEC-L) were irradiated at 15Gy and then cultured for 21 days to induce senescence. Then, to study their effect on tumor cells, the supernatant of RIS endothelial cells was collected and added to glioblastoma cells irradiated at 5 or 15Gy. CXCL5/8 levels were assessed by RT-Q-PCR and Elisa and their expression in GBM patient biopsies was confirmed by immunostaining comparing primary to recurrent tumors. The impact of CXCL5/8 chemokines on genomic instability and replicative stress was respectively assessed by micronuclei, aneuploidy and by DNA fiber assays.

Results:

First, brain immunostaining revealed the presence of β-galactosidase and p21waf1 senescence markers in the irradiated tumor microenvironment with the endothelial compartment being particularly susceptible. Secondly, SASP of RIS endothelial cells enhanced genomic instability of irradiated U251 and primary GBM cells, through aberrant DNA elongation, micronuclei generation and aneuploidy induction. Orthotopic injection of SASP preconditioned irradiated GBM cells increased mouse morbidity, confirming the acquired aggressiveness of GBM cancer cells. Two chemokines from SASP of RIS endothelial cells, CXCL5 and CXCL8, were specifically identified around vessels of GBM relapsing patient biopsies, and correlated with worst prognosis in TCGA database. Blocking strategies against CXCL5/8 in SASP or CXCR2, their shared receptor on GBM cells, was sufficient to reduce significantly the induced genomic instability and aggressiveness of tumor cells.