TMOD-13. Human pluripotent stem cell-derived cerebellar organoids as a robust platform for studying medulloblastoma pathogenesis

Abstract Medulloblastoma (MB) is a highly malignant pediatric brain tumor of the cerebellum characterized by extensive molecular, biological, and clinical heterogeneity. Current genetically engineered mouse models have only partially replicated this diversity, and harbor species-specific limitations owing to fundamental differences between mouse and human development. Therapeutic strategies that accommodate MB heterogeneity are required to improve patient outcomes but necessitate biologically faithful models that are predominantly lacking. To this end, we have established human pluripotent stem cell-derived cerebellar organoids that recapitulate early human cerebellar development and enable deep mechanistic studies into MB oncogenesis. Transcriptomic profiling and immunophenotyping of our organoids throughout developmental timepoints revealed cellular compositions and differentiation trajectories reminiscent of cerebellar development in vivo. As our cerebellar organoids faithfully reproduce putative lineages of origin for distinct MB subgroups, we’ve endogenously Cre-tagged stem cell lines and generated various expression constructs to manipulate known driver genes in specific cellular compartments to generate accurate human cerebellar organoid-based disease models. We furthered the utility of this ex vivo human system by establishing a cerebellar organoid/patient-derived xenograft (PDX) co-culture platform that fosters the sustainability of MB PDXs in culture. Upon co-culturing with cerebellar organoids, we observed sustained viability and proliferation of MB PDXs, both of which are unprecedented in standard in vitro cultures. Further, we observed differential electrophysiological properties in PDX-harboring organoids compared to standalone organoids and identified putative signaling pathways crucial for cellular crosstalk between tumor and their supporting microenvironment. Our ongoing multi-faceted MB modeling strategies leveraging cerebellar organoids engender new experimental opportunities otherwise incompatible with pre-existing approaches, providing an efficient platform for advancing disease biology and identifying therapeutic vulnerabilities.