MicroRNA-191, regulated by HIF-2α, is involved in EMT and acquisition of a stem cell-like phenotype in arsenite-transformed human liver epithelial cells

Inorganic arsenic is widely distributed in the environment, and epidemiologic data show a strong association between arsenic exposure and risk of liver cancer. An understanding of the mechanisms underlying development of liver cancer and metastasis would be useful in reducing the incidence and mortality of liver cancer. MicroRNAs (miRs) act as regulators in liver cancer. Here, we show that acute or chronic exposure of human liver epithelial L-02 cells to arsenite increased expression of miR-191. There were decreased levels of BASP-1 and E-cadherin and increased levels of WT-1 and N-cadherin, indicating that arsenite induced epithelial-mesenchymal transition (EMT). Moreover, arsenite increased EpCAM and CD90 mRNA levels, showing the acquisition of stem cell-like properties by these cells. Suppression of miR-191 resulted in repression of EMT and reduced expression of stem-cell markers. Further, a miR-191 inhibitor blocked spheroid formation and production of side population cells. Luciferase reporter assays indicated that miR-191 was a target of HIF-2α, and inhibition of miR-191 decreased the neoplastic and metastatic properties of arsenite-transformed L-02 cells. Thus, in arsenite-transformed liver epithelial cells, transcriptional activation of the miR-191 promoter by HIF-2α is involved in EMT and in the acquisition of a stem cell-like phenotype.