DMG-62. Investigating microglia/tumor interactions in neuroimmune-competent human brain organoids

Abstract Introduction Diffuse midline glioma (DMG) is a highly aggressive and infiltrative tumor with no effective treatment options to date, leading to a poor prognosis of less than a year median survival. Mechanistic understanding of DMG tumor cells’ interaction with cellular constituents of the tumor microenvironment, especially the brain’s immune cells - microglia, is critical for the development of new therapeutic approaches. We developed a clinically relevant, all-human cell, immunocompetent brain organoid/DMG fusion model for studying microglia-tumor interactions at the cellular and molecular levels. Methods Human embryonic stem cell-derived neuronal progenitor and GFP-labelled myeloid precursor cells were combined to form microglia-containing brain-organoids (MiCBO) after self-assembly and co-development over eight weeks. The fusion with RFP-labelled DMG spheroids (MiCBO-TF) enables the investigation of the motility and mobility of both tumor cells and microglia as well as the tumor-microglia interactions on a single-cell level using advanced live fluorescent imaging. Immunohistochemistry staining was used to examine the composition of the MiCBOs and the infiltration of DMG cells into the MiCBO. Candidate onco-therapy drug compounds, either as monotherapies or in combination with radiation, were evaluated in the MiCBO-TF system for efficacy and safety. Results Our MiCBOs contain viable, highly mobile and motile microglia. In addition, the presence of mature neurons and astrocytes was confirmed. DMG cell infiltration is significantly higher in the presence of microglia. The microglia display significantly higher velocity and movements after contact with tumor cells. The interaction patterns between tumor cells and microglia vary across different regions within the MiCBO-TF. Conclusion Our innovative MiCBO-DMG fusion model provides a physiologically-relevant tool for studying cell-cell interactions during tumor invasion in a human brain tissue context. It is reproducible, modular and adaptable for drug screenings to identify and develop therapeutics that modulate neuroimmune/tumor interactions to suppress tumor progression.