MODL-42. BLOOD-BRAIN TUMOR BARRIER ORGANOID MODEL FOR THERAPEUTIC DELIVERY TO GLIOBLASTOMA Free

The integrity of the blood-brain barrier (BBB) is compromised in brain tumors, leading to the formation of the blood-brain tumor barrier (BTB). While the BTB is generally more permeable than the BBB, it is nevertheless heterogeneously restrictive to the entry of therapeutic agents to brain tumors. Modeling the BTB accurately is crucial for understanding its physiological properties and developing effective treatments. Our lab has previously introduced a 3D in vitro human BBB organoid platform that reproduces key BBB markers and predicts compound permeability across the BBB in vivo. Here, we describe incorporating human GBM stem cells (GSC) into the organoid to form BTB organoids, presenting a novel scalable multicellular human brain tumor organoid model that simulates the BTB to facilitate therapeutic development in neuro-oncology. This model involves the self-assembly of essential BTB components, including human brain microvascular endothelial cells, astrocytes, brain pericytes and patient-derived GSCs, co-cultured under ultralow attachment conditions. Immunofluorescence microscopy results show reduced ZO-1 and Mfsd2a expression in the BTB compared to the control BBB organoids, indicating tight junction disruption and BBB breakdown by the GSCs. Correspondingly, we observe increased dextran permeability in the BTB organoids compared to the control BBB organoids, which is dependent on the GSC count per organoid. Electron and confocal microscopy reveal disorganized neovascular structures and invasive GSC behavior in the BTB organoids. Lastly, using a known GBM-targeting peptide (BTP-7), as well as a known BBB-penetrating adeno-associated virus (AAV.CPP.16) as proofs-of-concept, we demonstrate the efficacy of using the BTB organoids for modeling therapeutic delivery to brain tumors. In summary, the BTB organoid platform provides a tractable in vitro system reflecting the brain tumor microenvironment, enabling the study of GBM cell properties, investigation of barrier behavior, and modeling therapeutic delivery to brain tumors.