Monje, Michelle

Abstract Glioblastoma (GBM) is a lethal, treatment-resistant brain cancer characterized by diffuse brain invasion, complex neuron-glioma signaling, and cellular, molecular, and spatial heterogeneity. Surgery is the current mainstay of treatment, aimed at maximizing tumor cytoreduction, decompressing the brain to improve neurological function, and providing material for analyses to inform prognostication and adjuvant treatment selection. To accurately model GBM surgical resection and tissue sampling in preclinical animal models, we developed the Maximal Safe Intracranial Surgery (MSIS) system. MSIS integrated a miniaturized neurosurgical resection device and enabled a safe, tunable, and reproducible approach for intracranial tumor resection, multi-regional biopsy, and longitudinal tissue sampling in murine models, with stereotactic, sterile, and high-viability tissue collection. MSIS was applied across five distinct orthotopic brain tumor models to reproducibly generate histologically and radiologically representative models of post-surgical GBM. Similar to humans, increasing the extent of resection correlated with improved animal survival, and recurrent growth patterns varied significantly by model type. Transcriptional profiles of matched primary vs. post-surgical recurrent tumors revealed enrichment of margin-associated transcriptional states consistent with neuron-glioma signaling. Overall, the MSIS system offers opportunities to model the standard-of-care, dissect the spatial and temporal dynamics of GBM, and pair therapeutic discovery with contextual tumor pathobiology.

Abstract Pediatric high-grade gliomas (pHGG) are aggressive primary brain neoplasms with a dismal prognosis, making them the leading cause of brain tumor-related deaths in children. pHGGs occur in specific anatomical locations at specific ages underscoring their origin in neurodevelopment and the critical importance of the brain tumor microenvironment. Many pHGGs originate from oligodendroglial precursor cells (OPC) and, like OPCs, neuronal activity promotes pHGG proliferation. Neuronal activity drives pHGG growth through the secretion of activity-regulated mitogens and electrochemical communication with pHGG cells that integrate into neural circuits. In turn, pHGG increases neuronal excitability and remodels functional neural circuits. The interconnected network of glioma cells and neurons is fundamental to pHGG progression. We developed a two-color in vivo imaging method to study neuron-glioma cell interactions over time in freely behaving mice enabling us to record the frequency, pattern, and synchronicity of calcium transients in neurons, glioma cells, and their coactivity, giving us a comprehensive view of the changes in neuron-glioma circuit dynamics over time. Our imaging paradigm offers a unique ability to study neuron-glioma interactions at the systems level. We have observed increasing neuronal activity and synchronicity throughout the disease. We have also observed that different gliomas exhibit unique patterns of calcium transients and show increased levels of activity and synchronicity as the tumor progresses. We verified our findings through longitudinal in vivo local field potential recordings, finding an increase in all power bands, especially in high-gamma activity over time. Using single nuclei RNA sequencing of mice harboring murine H3K27M-­altered DMG, we observed gene expression changes indicating an increase in synaptogenesis and axonogenesis processes in glioma-associated neurons. Performing in vitro neurite outgrowth assays, we observed increased axonogenesis in hiPSC-derived neurons in the presence of pHGGs compared to other neurons, confirming our snRNA-seq findings. Based on this data, we hypothesize that as gliomas progress, the neuron-glioma malignant circuitry evolves through synaptogenesis and axonogenesis to promote glioma progression.

Abstract Pediatric high-grade gliomas (pHGG) are aggressive primary brain neoplasms with a dismal prognosis, making them the leading cause of brain tumor-related deaths in children. pHGGs occur in specific anatomical locations at specific ages underscoring their origin in neurodevelopment and the critical importance of the brain tumor microenvironment. Many pHGGs originate from oligodendroglial precursor cells (OPCs) and, like OPCs, neuronal activity promotes the proliferation of pHGGs. Neuronal activity drives pHGG growth through electrochemical communication with pHGG cells. In turn, pHGGs increase neuronal excitability and remodel functional neural circuits. The interconnected network of glioma cells and neurons is fundamental to pHGG progression. Using single-nuclei RNA sequencing of mice harboring murine H3K27M-altered Diffused Midline Glioma (DMG), we observed gene expression changes indicating an increase in axonogenesis processes in glioma-associated neurons (GANs), primarily driven by EphA signaling. EphA4, EphA5, and EphA7 are overexpressed in GANs while the ligand, EphrinA1, is overexpressed in H3K27M gliomas. Performing in vitro neurite outgrowth and co-culture assays, we observed increased axonogenesis in neurons in the presence of DMG cells and DMG-conditioned media. We developed a two-color in vivo imaging method to study neuron-glioma interactions over time in freely behaving mice enabling us to record the frequency, pattern, and synchronicity of calcium transients in neurons, glioma cells, and their coactivity, giving us a comprehensive view of the changes in neuron-glioma circuit dynamics over time. We have observed increasing neuronal activity and synchronicity throughout the disease. We have also observed that gliomas also exhibit increased levels of activity and synchronicity as the tumor progresses. We verified our findings through longitudinal in vivo local field potential recordings, finding an increase in all power bands, especially in high-gamma activity over time. Ongoing experiments will test how glioma-induced axonogenesis contributes to the observed evolution of malignant circuit dynamics over time. Taken together, our data shows as gliomas progress, the neuron-glioma malignant circuitry evolves through axonogenesis driven by EphA signaling.