miR-489 downregulation or gain of Smad3 is apotential modulator of both chemoresistance and EMT-like properties in breast cancers. The expression of miR-489 was decreased in chemoresistance MCF-7/ADM cells compared with chemosensitive cells. Upregulation of miR-489 enhanced the chemosensitivity. This evidence concerns the gene SMAD3 and breast carcinoma.