Abstract
PURPOSE: The goal of this study was to investigate the role and therapeutic targeting of T-type calcium channels in medulloblastoma, a common and deadly pediatric brain tumor that arises in the cerebellum. METHODS: T-type calcium channel expression was assessed in publicly available bulk and single cell RNA-seq datasets. The effects of T-type calcium channel blocker mibefradil on cell growth, death and invasion were assessed with cell counting, alamar blue, trypan blue and transwell assays. Proteomic-based drug target and signaling pathway mapping was performed with Reverse Phase Protein Arrays (RPPA). Co-expression modules of single cell RNA-seq data were generated using high dimensional weighted gene co-expression network analysis (hdWGCNA). Orthotopic xenografts were used for therapeutic studies with the T-Type calcium channel blocker mibefradil. RESULTS: T-type calcium channels were upregulated in more than 30% of medulloblastoma tumors and patients with high expression associated with a worse prognosis. T-type calcium channels had variable expression across all the subgroups of medulloblastoma at the bulk RNA-seq and single-cell RNA-seq level. Mibefradil treatment or siRNA mediated silencing of T-type calcium channels inhibited tumor cell growth, viability and invasion. RPPA-based protein/phosphoprotein signal pathway activation mapping of T-type calcium channel inhibition and single cell hdWGCNA identified altered cancer signaling pathways. Oral administration of mibefradil inhibited medulloblastoma xenograft growth and prolonged animal survival. CONCLUSION: Our results represent a first comprehensive multi-omic characterization of T-type calcium channels in medulloblastoma and provide preclinical data for repurposing mibefradil as a treatment strategy for these relatively common pediatric brain tumors.