Cepharanthine, a novel selective ANO1 inhibitor with potential for lung adenocarcinoma therapy.

Anoctamin-1 (ANO1), also known as transmembrane protein 16A (TMEM16A), is identified as a Ca2+-activated Cl- channel that is expressed in many organs and tissues. It is involved in numerous major physiological functions and especially in tumor growth. By screening 530 natural compounds, we identified cepharanthine as a potent blocker of ANO1 channels with an IC50 of 11.2 ± 0.9 μM and Emax of 92.7 ± 1.7%. The Lys384, Arg535, Thr539, and Glu624 in ANO1 are critical for the inhibitory effect of cepharanthine. Similar to its effect on ANO1, cepharanthine inhibits ANO2, the closest analog of TMEM16A. In contrast, up to 30 μM of cepharanthine showed limited inhibitory effects on recombinant ANO6 and bestrophin-1-encoded Ca2+-activated Cl- currents, but it showed no effects on endogenous volume-regulated anion currents (VRAC). Cepharanthine could also potently suppress endogenous ANO1 currents, significantly inhibit cell proliferation and migration, and induce apoptosis in LA795 lung adenocarcinoma cells. Moreover, animal experiments have shown that cepharanthine can dramatically inhibit the growth of xenograft tumors in mice. The high specificity provided by cepharanthine could be an important foundation for future studies of the physiological role of ANO1 channels, and these findings may reveal a new mechanism of its anticancer effect.