OS07.5.A GLIOBLASTOMA VESSEL CO-OPTION AND TRANSITION TO A RESISTANT CELL STATE ARE INDUCED BY CHEMORADIATION

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Abstract BACKGROUND Glioblastoma (GB) is one of the deadliest types of human cancer. Despite a very aggressive treatment regime, including resection of the tumor, radiation, and chemotherapy, the recurrence rate is more than 90%. Recurrence is mostly caused by the regrowth of highly invasive and resistant cells that have spread from the tumor bulk and are not removed by resection. To develop an effective therapeutic approach, we need to better understand the underlying molecular and cellular mechanisms of GB chemoradiation resistance and tumor spreading. MATERIAL AND METHODS To dynamically follow the changes occurring in GB post-therapy and investigate its relationship with vascular microenvironment, we employed multiple bulk and single-cell RNA-Seq analyses, phosphoproteome, in vitro and in vivo real-time imaging, organotypic cultures and functional assays, digital pathology, and spatial transcriptomics on patient material or preclinical models of GB. RESULTS We demonstrated that chemoradiation and the brain vasculature induce a transition to a functional cell state, which we named VC-Resist. This cell state is midway through the transcriptomic axis between proneural and mesenchymal GB cells and is closer to the AC/MES-like state. Better cell survival, G2M-arrest, activation of senescence/stemness pathways make this GB cell state more resistant to therapy. Notably, these persister GB cells are highly vessel co-opting, allowing homing to the perivascular niche, which, in turn, increases their transition to this cell state and resistance to therapy. Molecularly, the transition to the VC-Resist cell state is driven by FGF-FGFR1 signaling, which leads to the activation of DNA damage repair and YAP1 pathways. CONCLUSION These findings demonstrate that the perivascular niche and GB cell plasticity jointly generate a vicious loop that leads to resistance to therapy and brain infiltration during GB recurrence. SUPPORT This work was supported by the European Research Council (ERC) under the European Union’s Horizon 2020 (Grant Agreement No. 805225), the INSERM-CNRS ATIP-Avenir grant, the NanoTheRad grant from Paris-Saclay University, Fondation ARC pour la recherche sur le cancer, Campus France and Canceropole Ile-de-France (2022-1-EMERG-06-ICR-1).

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