The impact of metformin and salinomycin on transforming growth factor ß-induced epithelial-to-mesenchymal transition in non-small cell lung cancer cell lines.

ABSTRACT

The epithelial-to-mesenchymal transition (EMT) is highly involved in the development of metastases. EMT transforms epithelial carcinoma cells into mesenchymal-like cells, characterized by increased cell migration and invasiveness. Transforming growth factor ß (TGFß) appears to be crucial in this process. Metformin and salinomycin have demonstrated an EMT inhibitory effect. The current experiments indicate that these substances specifically inhibit TGFß-induced EMT in non-small cell lung cancer (NSCLC) cell lines. The NSCLC cell lines A549 and HCC4006 were stimulated with TGFß for 48 h to induce EMT. Metformin or salinomycin was added simultaneously with TGFß to inhibit TGFß-induced EMT. Western blot analyses of E-cadherin and vimentin were performed to detect changes in EMT marker expression, and a wound healing assay was conducted to determine the potential effects on cell migration. The effects of the two drugs on cell viability were also investigated using MTS tetrazolium dye assays. The results revealed that cells undergoing EMT by application of TGFß exhibited a downregulation of E-cadherin and an upregulation of vimentin protein expression on western blot analyses, and an increased capacity for cell migration. Simultaneous application of TGFß and metformin specifically inhibited EMT and increased E-cadherin expression. At the higher dose tested, salinomycin also inhibited EMT, despite an increase in vimentin expression in the two cell lines. Furthermore, metformin and salinomycin, at the two concentrations tested, inhibited cell migration. These findings demonstrate that metformin and salinomycin are able to block EMT and inhibit EMT-induced cell migration. Thus, these two substances are novel EMT inhibiting drugs that have the potential to specifically control EMT and metastatic spread in NSCLC.