Anoctamin 1 (ANO1) is a
calcium-activated chloride channel found in various cell types and is overexpressed in
non-small cell lung cancer (NSCLC), a major cause of
cancer-related mortality. With the rising interest in development of druggable compounds for NSCLC, there has been a corresponding rise in interest in ANO1, a novel
drug target for NSCLC. However, as ANO1 inhibitors that have been discovered simultaneously exhibit both the functions of an inhibition of ANO1 channel as well as a reduction of ANO1
protein levels, it is unclear which of the two functions directly causes the anticancer effect. In this study,
verteporfin, a chemical compound that reduces ANO1
protein levels was identified through high-throughput screening.
Verteporfin did not inhibit ANO1-induced
chloride secretion but reduced ANO1
protein levels in a dose-dependent manner with an IC50 value of ~300 nM. Moreover,
verteporfin inhibited neither P2Y receptor-induced intracellular Ca2+ mobilization nor
cystic fibrosis transmembrane conductance regulator (CFTR) channel activity, and molecular docking studies revealed that
verteporfin bound to specific sites of ANO1
protein. Confirming that
verteporfin reduces ANO1
protein levels, we then investigated the molecular mechanisms involved in its effect on NSCLC cells. Interestingly,
verteporfin decreased ANO1
protein levels, the EGFR-STAT3 pathway as well as ANO1
mRNA expression.
Verteporfin reduced the viability of ANO1-expressing cells (PC9, and
gefitinib-resistant PC9) and induced apoptosis by increasing
caspase-3 activity and PARP-1 cleavage. However, it did not affect hERG channel activity. These results show that the anticancer mechanism of
verteporfin is caused via the down-regulation of ANO1.