miR-93 and PTEN: Key regulators of doxorubicin-resistance and EMT in breast cancer.

It is not well established whether miR-93 is involved in drug resistance and epithelial-mesenchymal transition (EMT) in breast cancer, and its underlying mechanism remains uncertain. In the present study, the expression differences of miR-93 between paired breast cancer tissues confirmed it is involved in the progression of breast cancer. Such a difference was also observed in doxorubicin-resistant and -sensitive cells. Overexpressed miR-93 in sensitive cells revealed increases in cellular proliferation and the expression levels of drug-resistant-related genes, and a decrease in sensitivity to doxorubicin. This demonstrated the relationship between miR-93 and breast cancer drug resistance. Simultaneously, EMT was confirmed in miR-93 overexpressing sensitive cells. This indicated the triadic relationship among miR-93, EMT and drug resistance in breast cancer. We applied the Dual-luciferase Reporter assay to expose the direct interaction between miR-93 and PTEN, which suggested that miR-93 contributes to inducing EMT and drug resistance of breast cancer cells by targeting PTEN.