Transcriptional repression of HER2 by Cl^- channel blockade in human breast cancer cells

抄録

Recent studies indicated that the intracellular concentration of chloride ions (Cl^-) regultes the gene expression in several types of cells. Our previous study showed that the Ca²⁺-activated Cl^- channel ANO1 (also known as TMEM16A) regulates human epidermal growth factor receptor 2 (HER2) transcription in breast cancer YMB-1 cells. However, the mechanism of Cl^--dependent HER2 gene expression remain to be elucidated. In the present study, we further found the involvement of ClC-3 Cl^- channels in HER2 transcription in breast cancer MDA-MB-453 cells. Pharmacological blockade and siRNA-mediated inhibition of ClC-3 but not ANO1 markedly repressed HER2 transcription in MDA-MB-453 cells. It has been reported that changes in intracellular Cl^- concentration positively or negatively regulates PI3K/AKT/mTOR and STAT3 signaling pathways. Treatments with an AKT inhibitor AZD 5363 (1 μM) and an mTOR inhibitor everolimus (10 nM) significantly enhanced the HER2 transcription in MDA-MB-453 cells. Moreover, treatment with a STAT3 inhibitor 5,15-DPP (10 μM) inhibited it. AKT and mTOR inhibitors also significantly enhanced the HER2 transcription in YMB-1 cells. Collectively, our results demonstrate that intracellular Cl^- regulation by ANO1/ClC-3 Cl^- channels participates HER2 transcription mediating PI3K/AKT/mTOR and/or STAT3 signaling pathway(s) in HER2-positive breast cancer cells, and ANO1/ClC-3 blockers are emerging therapeutic options for patients with resistance to anti-HER2 therapies.