T-type Cav3.1 channels mediate progression and chemotherapeutic resistance in glioblastoma.

T-type Ca2+ channels (TTCC) have been identified as key regulators of cancer cell cycle and survival. In vivo studies in glioblastoma (GBM) murine xenografts have shown that drugs able to block TTCC in vitro (such as tetralol derivatives mibefradil/NNC-55-096, or different 3,4-dihydroquinazolines) slow tumor progression. However, currently available TTCC pharmacological blockers have limited selectivity for TTCC, and are unable to distinguish between TTCC isoforms. Here we analyzed the expression of TTCC transcripts in human GBM cells and show a prevalence of Cav3.1 mRNAs. Infection of GBM cells with lentiviral particles carrying shRNA against Cav3.1 resulted in GBM cell death by apoptosis. We generated a murine GBM xenograft via subcutaneous injection of U87-MG GBM cells and found that tumor size was reduced when Cav3.1 expression was silenced. Furthermore, we developed an in vitro model of temozolomide-resistant GBM that showed increased expression of Cav3.1 accompanied by activation of macroautophagy. We confirmed a positive correlation between Cav3.1 and autophagic markers in both GBM cultures and biopsies. Of note, Cav3.1 knockdown resulted in transcriptional downregulation of p62/SQSTM1 and deficient autophagy. Together, these data identify Cav3.1 channels as potential targets for slowing GBM progression and recurrence based on their role in regulating autophagy.