Targetable T-type Calcium Channels Drive Glioblastoma

Abstract

Glioblastoma stem-like cells (GSC) promote tumor initiation, progression and therapeutic resistance. Here we show how GSC can be targeted by the FDA approved drug mibefradil which inhibits the T-type calcium channel Cav3.2. This calcium channel was highly expressed in human GBM specimens and enriched in GSC. Analyses of the TCGA and REMBRANDT databases confirmed upregulation of Cav3.2 in a subset of tumors and showed that overexpression associated with worse prognosis. Mibefradil treatment or RNAi-mediated attenuation of Cav3.2 was sufficient to inhibit the growth, survival and stemness of GSC, and also sensitized them to temozolomide (TMZ) chemotherapy. Proteomic and transcriptomic analyses revealed that Cav3.2 inhibition altered cancer signaling pathways and gene transcription. Cav3.2 inhibition suppressed GSC growth in part by inhibiting pro-survival AKT/mTOR pathways and stimulating pro-apoptotic survivin and BAX pathways. Further, Cav3.2 inhibition decreased expression of oncogenes (PDGFA, PDGFB, and TGFB1) and increased expression of tumor suppressor genes (TNFRSF14 and HSD17B14). Oral administration of mibefradil inhibited growth of GSC-derived GBM murine xenografts, prolonged host survival and sensitized tumors to TMZ treatment. Our results offer a comprehensive characterization of Cav3.2 in GBM tumors and GSC, and provide a preclinical proof of concept for repurposing mibefradil as a mechanism-based treatment strategy for GBM.

T-Type Cav3.1 Channels Mediate Progression and Chemotherapeutic Resistance in Glioblastoma

“…Recently, Zhang and colleagues have shown that the Ca v 3.2 isoform is highly expressed in GBM stem cells (GSC; ref. 20) In this study, treatment with the TTCC blocker, mibefradil, downregulated GSC proliferation and stemness markers, and the authors concluded that Ca v 3.2 is involved in the maintenance of undifferentiated stem cells, in agreement with ref. 21.…”

“…Zhang and colleagues recently reported that the Ca v 3.2 TTCC isoform is highly expressed in GSC, human GBM cell lines, and specimens. The authors also performed an in silico genomic analysis of TCGA data that revealed overexpression of Ca v 3.2 in 13 of 136 GBM samples, and that these cases presented a trend toward shorter survival (20). Here we analyzed the TCGA database with identical z-scores, and observed that 20 of 136 tumors overexpressed Ca v 3.1; patients with alterations in Ca v 3.1 also showed a tendency toward shorter overall survival, even if devoid of statistical significance (Fig.…”

“…Particularly, the role of TTCC in GBM progression has received considerable attention in recent years. Thus, the effects of pharmacologic blockers on halting proliferation and inducing apoptosis of GBM cells in vitro led to the development of murine GBM xenografts, in which TTCC pharmacologic blockers reduced tumor growth (18)(19)(20). Although currently available blockers cannot discriminate between TTCC isoforms and are also reported to exert off-target actions, some authors have linked TTCC isoform detection with drug effects in what can be considered as a loose target identification.…”

T-Type Calcium Channels: A Potential Novel Target in Melanoma

“…At present, it is possible to arrest cancer cell proliferation and induce cell death by inhibiting TTCCs on a wide range of cancer cells. Conversely, the use of TTCC pharmacological blockers has proven effective in reducing the viability of tumor cells grown in vitro [19,20,22,30,31,84] and in preclinical tumor growth mice models [22,30,31,85,86]. There are a variety of agents that could affect TTCCs with varying degrees of specificity.…”

Voltage-gated ion channels mediate the electrotaxis of glioblastoma cells in a hybrid PMMA/PDMS microdevice

“…VGCCs are known to play important roles in glioma biology such as cell proliferation, apoptosis, and sensitization to ionizing radiation 27,75,76 . VGCCs can be categorized as high voltage activated (HVA) or low voltage activated (LVA) types [77][78][79] .…”