Randhawa, Kamaldeep2024-07-292024-07-292024-07-29http://hdl.handle.net/10393/46425https://doi.org/10.20381/ruor-30458Glioblastoma (GB) is the most lethal neurological malignancy of the central nervous system, with a median survival of 18 months despite intense treatment involving maximal surgical resection, ionizing radiation (IR), and temozolomide (TMZ). The inevitability of GB recurrence is in part driven by a population of self-renewing cancer stem cells known as brain tumor stem cells (BTSCs) that can evade conventional treatment modalities. Targeting the signaling pathways that sustains BTSCs holds promise for combating GB recurrence. Notably, the elevated expression of the cytokine receptor Oncostatin M Receptor (OSMR) and the frequent co-occurrence of the mutant Epidermal Growth Factor Receptor (EGFR) gene, Epidermal Growth Factor Receptor variant III (EGFRvIII), within BTSCs, contribute to the establishment of highly tumorigenic and treatment-resistant cells. However, the mechanisms by which the OSMR/EGFRvIII complex sustains BTSCs and promotes tumourigenesis remain largely unknown. In this study, we identified a novel binding partner of OSMR, Chloride Intracellular Channel 1 (CLIC1), in patient-derived BTSCs through a Mammalian Membrane Two-Hybrid High Throughput (MaMTH-HTS) screen and endogenous validation with proximity ligation assay analysis. Functional assays demonstrated that CLIC1 affects the viability, proliferation, and self-renewal of BTSCs in vitro, and tumour progression in vivo. Mechanistically, the functional capacity of BTSCs to form tumours upon intracranial injection is mediated by the EGFRvIII/STAT3 pathway, as genetic deletion of CLIC1 resulted in impaired STAT3 activation and reduced EGFRvIII levels. Finally, we demonstrated that OSMR is required for CLIC1 function at the plasma membrane. Our data suggest that CLIC1 is potentially a viable therapeutic target for suppressing OSMR/EGFRvIII/STAT3 oncogenic signalling and depleting the resistant BTSCs in GB. This work provides new insights into the molecular underpinnings of GB but also lays the foundation for future research aimed at developing targeted therapies against CLIC1 and its associated pathways to improve treatment outcomes for patients of GB.enGlioblastomaChloride intracellular channel 1Oncostatin M ReceptorSelf-renewalTumourigenesisThesis