Downregulation of Ca2+-activated Cl- channel TMEM16A by the inhibition of histone deacetylase in TMEM16A-expressing cancer cells.

The Ca(2+)-activated Cl(-) channel transmembrane proteins with unknown function 16 A (TMEM16A; also known as anoctamin 1 or discovered on gastrointestinal stromal tumor 1) plays an important role in facilitating the cell growth and metastasis of TMEM16A-expressing cancer cells. Histone deacetylase (HDAC) inhibitors (HDACi) are useful agents for cancer therapy, but it remains unclear whether ion channels are epigenetically regulated by them. Using real-time polymerase chain reaction, Western blot analysis, and whole-cell patch-clamp assays, we found a significant decrease in TMEM16A expression and its functional activity was induced by the vorinostat, a pan-HDACi in TMEM16A-expressing human cancer cell lines, the prostatic cancer cell line PC-3, and the breast cancer cell line YMB-1. TMEM16A downregulation was not induced by the chemotherapy drug paclitaxel in either cell type. Pharmacologic blockade of HDAC3 by 1 μM T247 [N-(2-aminophenyl)-4-[1-(2-thiophen-3-ylethyl)-1H-[1],[2],[3]triazol-4-yl]benzamide], a HDAC3-selective HDACi, elicited a large decrease in TMEM16A expression and functional activity in both cell types, and pharmacologic blockade of HDAC2 by AATB [4-(acetylamino)-N-[2-amino-5-(2-thienyl)phenyl]-benzamide; 300 nM] elicited partial inhibition of TMEM16A expression (∼40%) in both. Pharmacologic blockade of HDAC1 or HDAC6 did not elicit any significant change in TMEM16A expression, respectively. In addition, inhibition of HDAC3 induced by small interfering RNA elicited a large decrease in TMEM16A transcripts in both cell types. Taken together, in malignancies with a frequent gene amplification of TMEM16A, HDAC3 inhibition may exert suppressive effects on cancer cell viability via downregulation of TMEM16A.