CNSC-53. SHARED REGULATION OF QUIESCENCE PATHWAYS BETWEEN NEURAL AND GLIOMA STEM CELLS REVEALS TGF-Β SIGNALLING AS A THERAPEUTIC TARGET IN GLIOBLASTOMA

Abstract Glioblastoma has poor outcomes because the disease invariably recurs after frontline treatment, in part due to chemotherapy-resistant, quiescent glioma stem cells that reconstitute the tumour after treatment stops. Currently, no treatment methods specifically target these cells, as their lack of markers and plasticity make them challenging to study directly in human tumours. Critically, if the molecular programs governing quiescence are conserved between neural stem cells and glioma stem cells, the knowledge and tools developed in neural stem cell biology could be leveraged to dissect and target the quiescent population in glioma. We explored this potential by combining pseudotime trajectory reconstruction, single-cell RNA-sequencing, and functional assays in patient-derived glioma stem cell lines and organoids. We showed that while glioma stem cells are more resistant to entering deeper states of quiescence than neural stem cells, they partly share gene expression programs during activation. Building on this, we functionally interrogated a range of pathways known to regulate quiescence in adult neural stem cells in vivo and found that many exerted similar effects in glioma stem cells in vitro, underscoring shared regulatory logic and revealing tractable therapeutic targets. Notably, inhibiting TGF-β signalling, but not BMP signalling, prevented glioma stem cells from entering quiescence in both the 2d cultures and organoids. We also observed higher expression of TGF-β ligands than canonical BMPs in patient tumours based on single-nucleus RNA-sequencing analysis. Together these results indicate that autocrine or paracrine production of TGF-β ligands, though not BMP ligands, may be critical in mediating quiescence in glioblastoma. TGF-β pathways have already been targeted by agents in early-phase clinical trials (NCT01220271) making them tractable candidates for interventions aimed at exhausting the quiescent glioma stem cell pool in patients. In combination with the current standard-of-care treatment, this may improve response and prolong patient survival.