T-type Ca2+ Channels: T for Targetable.

In the past decade, T-type Ca2+ channels (TTCC) have been unveiled as key regulators of cancer cell biology and thus have been proposed as chemotherapeutic targets. Indeed, in vitro and in vivo studies indicate that TTCC pharmacologic blockers have a negative impact on the viability of cancer cells and reduce tumor size, respectively. Consequently mibefradil, a TTCC blocker approved in 1997 as an antihypertensive agent but withdrawn in 1998 because of drug-drug interactions, was granted 10 years later the orphan drug status by the FDA to investigate its efficacy against brain, ovary, and pancreatic cancer. However, the existence of different channel isoforms with distinct physiologic roles, together with the lack of selective pharmacologic agents, has hindered a conclusive chemotherapeutic evaluation. Here, we review the available evidence on TTCC expression, value as prognostic markers, and effectiveness of their pharmacologic blockade on cancer cells in vitro and in preclinical models. We additionally summarize the status of clinical trials using mibefradil against glioblastoma multiforme. Finally, we discuss the future perspectives and the importance of further development of multidisciplinary research efforts on the consideration of TTCCs as biomarkers or targetable molecules in cancer. Cancer Res; 78(3); 603-9. ©2018 AACR. ©2018 American Association for Cancer Research.