Herbal alkaloid tetrandrine: from an ion channel blocker to inhibitor of tumor proliferation

The herbal alkaloid tetrandrine blocks voltage-gated Ca2+ channels, intracellular Ca2+ pumps and large-conductance Ca2+-activated K+ (BK) channels. Recent work has focused on the signaling pathways that underlie tetrandrine-mediated inhibition of tumor cell proliferation and cytotoxicity. Because K+ channels play an important role in the regulation of cell cycle progression, apoptosis and immunoreactions, this article focuses on tetrandrine-mediated responses of cell proliferation and cytotoxicity, and speculates on possible correlations with the tetrandrine-induced BK channel block.