SRS37 - Myeloid-GSC interactions at the invasive edge of live human glioblastoma

Abstract Introduction Glioblastoma remains incurable in part due to the complex interactions between malignant and non-malignant cells in the tumour microenvironment. In particular there is a lack of understanding regarding the crosstalk between brain-resident myeloid cells and infiltrated tumour cells. These dynamics are poorly captured in conventional non-human models. We therefore developed a live human brain tissue platform to directly visualise tumour-myeloid interactions ex vivo at the invasive edge. Methods Using intraoperative navigation, tumour bulk and invading edge tissues were resected en bloc during debulking surgery, sectioned into 300 µm slices, and maintained in culture. Immunofluorescence staining (SOX2, Nestin, and Iba1) combined with spatial point pattern analysis and live viral labelling imaging enabled interrogation of tumour–immune architecture and cell morphology and motility. Results The invasive edge showed a distinct architecture: reduced cellularity, fewer SOX2⁺ cells, and Nestin⁺ cells with elongated, neurite-like processes preserved for three weeks. Tumour-myeloid interactions revealed density-independent clustering of Iba1⁺ microglia around SOX2+ cells at the invasive edge (n = 5, P < 0.01). Live imaging showed that tumour cells migrated with significantly greater displacement and velocity than microglia (P < 0.01), displaying key mechanisms of tumour cell infiltration. Conclusions We provide the first ex vivo human model that directly captures tumour–myeloid interactions at the invasive edge. Our findings highlight a paradoxical niche where tumour cells are both more motile and yet still surrounded by clustering microglia, revealing a previously unappreciated feature of invasion. Our system opens new opportunities to dissect mechanisms of tumour infiltration and immune evasion.