Mechanistic insights of radiation-induced endothelial senescence impelling glioblastoma genomic instability at relapse

Despite aggressive clinical protocol, all glioblastoma (GBM) recur at the initial site within the irradiated peritumoral microenvironment. Whereas irradiated microenvironment has been recently proposed to accelerate GBM relapse, molecular and cellular mechanisms remain unknown. Here, using relevant in vitro and in vivo models, we decipher how radiation-induced endothelial senescence drives the emergence of aggressive GBM cells. Secretome (SASP) of radiation-induced senescent (RIS) endothelium enhances genomic instability and intratumoral heterogeneity in irradiated GBM cells. In-depth molecular studies revealed that CXCL5 and CXCL8, from the SASP, activate CXCR2 receptor on tumor cells leading to increased DNA hyper-replication, micronuclei formation and aneuploidy. Importantly, through CXCL5/8-CXCR2 axis activation, this SASP increases GBM aggressiveness in vivo . Both chemokines were detected in relapsing, but not primary, GBM biopsies and positively correlated with worst patient outcome. In conclusion, we identify new molecular and preclinical insights of relapsing GBM aggressiveness where RIS vascular niches fuel aggressive tumor emergence.