Down-regulation of miR-129-5p via the Twist1-Snail feedback loop stimulates the epithelial-mesenchymal transition and is associated with poor prognosis in breast cancer

The epithelial to mesenchymal transition (EMT) plays a pivotal role in breast cancer progression. We found that overexpression of miR-129-5p reversed EMT, whereas depletion of miR-129-5p induced EMT in breast cancer cells. We demonstrated that Twist1 is a direct target of miR-129-5p. Both Twist1 and Snail transcriptionally suppressed miR-129-5p expression. Levels of miR-129-5p were low in breast cancer tissues. miR-129-5p down-regulation correlated with advanced clinical stage and poor prognosis in patients with breast cancer. miR-129-5p expression negatively correlated with Twist1 and Snail expression. Thus, miR-129-5p down-regulation fosters EMT in breast cancer by increasing Twist1-Snail and activating a negative feedback loop.