CNSC-50. A SYNAPSE-OPTIMIZED HUMAN ORGANOID TUMOR TRANSPLANTATION MODEL OF GLIOBLASTOMA UNCOVERS DISTINCT MODES OF NEURON-TUMOR INTERACTIONS IN THE TUMOR CORE AND PERIPHERY

Abstract Functional integration of glioblastoma (GBM) cells into neural circuits has emerged as an important mechanism promoting tumor progression. Studies on rodent models revealed that neuron-tumor synapses (NTS) transmit excitatory glutamatergic signals, predominantly via AMPA receptors, leading to increased tumor proliferation. Notably, synaptogenic potential is enriched in neurodevelopmental tumor cell states at the invasive tumor margin, where GBM cells interface with a relatively intact neuronal microenvironment. To model and characterize this process in a human-specific manner, we developed a synapse-optimized human organoid tumor transplantation (so-HOTT) model of GBM by transplanting tumor cells derived from the tumor core and periphery into cortical organoids. Using rationally selected media supplements that accelerate neuronal maturation, we coaxed the formation of NTS in so-HOTT over a 4-week time period. Machine learning-based automated synapse quantification confirmed that so-HOTT exhibits increased co-localization of pre- and postsynaptic markers with both core and peripheral tumor cells. Single-cell RNA sequencing also revealed that so-HOTT activates genes involved in postsynaptic assembly and organization, while benchmarking to our GBM meta-atlas indicated that so-HOTT mimics the preferential expression of ionotropic glutamatergic receptors by primary tumors. Cell-cell communication analysis using CellChat further showed that so-HOTT enriches for intercellular interactions important for synaptic communication. Several of these interactions are more enriched in GBM cells derived from the tumor periphery than in the core, suggesting that so-HOTT preserves known differences in synaptogenic properties between these two regions. Using an AAV1-Cre-based anterograde trans-synaptic tracing system, we further demonstrate that bona fide NTS are present in so-HOTT. To further validate that these NTS are functional, we are currently performing calcium imaging of so-HOTT. We envision that this model will be a valuable tool for perturbing and investigating key regulators of neuron-tumor interactions, thereby allowing the identification of novel therapeutic targets that can disrupt this critical communication channel.