CNSC-11. T-TYPE CALCIUM CHANNELS DRIVE GLIOBLASTOMA GROWTH BY PROMOTING NEURONAL INTERACTIONS

Abstract

Abstract Glioblastoma (GBM) is the most common primary malignant brain tumor with a dismal median survival of 15 months. Calcium signaling regulates a plethora of cellular processes making it an ideal target for therapeutic intervention. T-type calcium channels (TTCCs) are low voltage gated calcium channels expressed in various types of neurons throughout the brain regulating glutamatergic synaptic transmission. Our group identified T-type calcium channels as upregulated in GBM cells, stem cells and human tumors. Utilizing an FDA repurposed TTCC blocker mibefradil we demonstrated that inhibition of TTCCs decreases GBM malignancy parameters. To further elucidate the mechanisms of action of TTCC, we treated glioma stem cells (GSCs) with mibefradil followed by RNA-sequencing. Analysis of the transcriptome revealed that mibefradil downregulated genes associated with neuronal processes including synapse organization, postsynaptic density and glutamatergic synapses. The effects of TTCC inhibition on neuronal processes led us to examine the role of neuronal TTCC in promoting GBM growth. Genetic loss of TTCC, Cav3.2 via knockout (KO) in the microenvironment of mice xenografted with syngeneic cell lines exhibited delayed tumor progression. Cav3.2 KO mice exhibited a 5.5-fold reduction in tumor volume as measured by MRI and an increase in survival compared to WT mice. Cav3.2 KO tumors exhibited a decrease in proliferation measured by Ki67+ cells compared to WT mice. Cav3.2KO tumors exhibit fewer connections between tumor cells and neurons as measured by immunofluorescence. To further test the roles of neuronal Cav3.2 in GBM, we isolated WT and Cav3.2KO neurons for neuron-GBM co-cultures. Cav3.2KO neuron-GBM co-cultures exhibited a significant decrease in proliferation compared to WT neuron-GBM co-cultures. Additionally, 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. These data uncover a new role for TTCC Cav3.2 in promoting neuron-GBM interactions and GBM growth.