Microenvironment T-type calcium channels regulate neuronal and glial processes in tumor cells to promote glioblastoma growth

BACKGROUND: Glioblastoma (GBM) is the most common primary malignant brain tumor. The aim of this study was to elucidate the role of microenvironment and intrinsic T-type calcium channels (Cav3) in regulating GBM. METHODS: We grafted syngeneic GBM cells into Cav3.2 knockout (KO) mice to assess the role of microenvironment T-type calcium channels on GBM growth. We grafted syngeneic GBM cells into the hippocampus along the Schaffer collaterals and performed electrophysiology. We used neurons from wild type (WT) and Cav3.2KO mice in co-culture with GBM stem cells (GSCs) to assess the effects of Cav3.2 on neuron/GSC synaptic connections and tumor cell growth. We performed single-cell RNA sequencing (scRNA-seq) of tumors from WT and Cav3.2KO mice to elucidate the regulation of tumors by the microenvironment. RESULTS: Cav3.2KO in the microenvironment led to significant reduction of GBM growth and prolongation of animal survival. Neuronal Cav3.2 promoted GSC growth in co-culture and neuron/GBM functional synaptic connections in vivo. scRNA-seq showed that microenvironment Cav3.2 regulates neuronal and glial biological processes. Microenvironment Cav3.2 downregulated numerous genes associated with regulating the oligodendrocyte precursor-like cell state in GBM tumors. Treatment of GSCs with the Cav3 blocker mibefradil downregulated genes associated with neuronal processes. The Cav3 blocker drug mibefradil synergized with temozolomide (TMZ) and radiation to reduce in vivo tumor growth and prolong animal survival. CONCLUSIONS: The data reveal a role for microenvironment Cav3 in promoting GBM progression through regulating neuronal and glial processes. Targeting both intrinsic and microenvironment Cav3 with the inhibitor mibefradil significantly enhanced the anti-GBM effects of TMZ and radiation.