TMOD-25. Investigating neuroimmune-tumor interactions and oncological therapy responses in human brain organoid model of diffuse midline glioma

Abstract INTRODUCTION Currently, there are no effective treatment options for diffuse midline glioma (DMG) and the highly aggressive and infiltrative brain tumor is universally fatal with a median survival of less than a year. There is a critical unmet need for clinically relevant models that provide insight into the mechanisms of DMG infiltration and cell-cell interactions within the tumor microenvironment to advance new therapeutic approaches. We recently published an all-human cell brain organoid model of DMG that contains microglia - the brain’s innate immune cells - as an immune component. METHODS We combined human embryonic stem cell-derived neuronal progenitor and GFP-labelled myeloid precursor cells to form microglia-containing brain-organoids (MiCBO). To monitor DMG cell infiltration into the brain organoid, microglia movement, and the interaction between the two cell types, we fused TdT+ DMG spheroids with MiCBO (MiCBO-TF) and followed their migration and interactions via live-cell imaging and immunofluorescence stainings. Additionally, we applied a number of oncological agents in addition to radiotherapy to the MiCBO-TF system and evaluated the efficacy and safety of therapy combinations with confocal imaging, a cell proliferation assay, and histology. RESULTS Our MiCBO contain highly motile and mobile microglia that interact with DMG cells through palpating, hunting, and engulfing behaviors. The presence of astrocytes, mature neurons, and GABAergic interneurons was confirmed. The inclusion of microglia increased the DMG cell infiltration into the MiCBO significantly. A high dose of temozolomide, a standard-of-care chemotherapy prescribed for glioblastoma patients, did not show any reduction in tumor infiltration. Avapritinib, a PDGFRA inhibitor that has previously shown efficacy in a glioblastoma mouse model, and a combination of drugs targeting fatty acid synthesis together with the PI3K pathway significantly reduced DMG infiltration. CONCLUSIONS Our innovative MiCBO-DMG fusion model is a biologically complex, reproducible, and scalable platform for DMG mechanism investigation and therapy screening.