CNSC-14. T-TYPE CALCIUM CHANNELS REGULATE NEURON-GLIOBLASTOMA INTERACTIONS AND PROMOTE TUMOR GROWTH

Abstract Glioblastoma (GBM) is the most common primary malignant brain tumor with a dismal median survival of 15 months. Glioblastoma utilizes calcium signaling to regulate communication between tumor cells and the neuronal microenvironment. T-type calcium channels (TTCCs) are voltage gated calcium channels expressed in various types of neurons throughout the brain regulating glutamatergic synaptic transmission. We analyzed spatial transcriptomics of human GBM tumors and found that TTCCs are expressed in infiltrating tumor regions and enriched for neuronal development spatial patterns and exhibit neurodevelopmental signatures. Analysis of single cells transcriptomic of human GBM tumors demonstrated that TTCCs are enriched in neuronal subtypes. To complement publicly available data,we treated Glioblastoma Stem cells (GSCs) with an FDA-approved repurposed TTCC blocker, mibefradil, and found downregulation of genes associated with neuron processes such as synapse organization, postsynaptic density and glutamatergic synapses. Treatment of GSCs with mibefradil abrogated cell proliferation in the presence of glutamate. We examined the effects of neuronal Cav3.2 on GBM growth. Genetic Cav3.2 knockout (Cav3.2 KO) in the microenvironment of mice xenografted with syngeneic cell lines (GL261 and CT2A) exhibited significant tumor volume reduction as well as increased survival compared to WT mice in both cell lines. Cav3.2 KO tumors exhibited a decrease in proliferation (Ki67+) and neuronal connections (VGlut1) measured by immunofluorescence compared to WT mice. Cav3.2KO neuron-GBM co-cultures exhibited a significant decrease in proliferation compared to WT neuron-GBM co-cultures. Cav3.2KO neuron-GBM co-cultures exhibited a decrease in synaptic connections and a decrease in neuronal projections to GBM cells compared to WT neuron-GBM co-cultures. Transcriptomic analysis of tumors from Cav3.2KO tumors revealed deregulation of genes associated synaptic transmission, glutamatergic synapses and postsynaptic specialization. Altogether, our findings indicate a role of Cav3.2 in regulating tumors and neurons and promoting GBM progression.