miR-655 suppresses epithelial-to-mesenchymal transition by targeting Prrx1 in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is a highly aggressive breast cancer subtype that lacks effective targeted therapies. The epithelial-to-mesenchymal transition (EMT) is a key contributor in the metastatic process. In this study, we found that miR-655 was down-regulated in TNBC, and its expression levels were associated with molecular-based classification and lymph node metastasis in breast cancer. These findings led us to hypothesize that miR-655 overexpression may inhibit EMT and its associated traits of TNBC. Ectopic expression of miR-655 not only induced the up-regulation of cytokeratin and decreased vimentin expression but also suppressed migration and invasion of mesenchymal-like cancer cells accompanied by a morphological shift towards the epithelial phenotype. In addition, we found that miR-655 was negatively correlated with Prrx1 in cell lines and clinical samples. Overexpression of miR-655 significantly suppressed Prrx1, as demonstrated by Prrx1 3'-untranslated region luciferase report assay. Our study demonstrated that miR-655 inhibits the acquisition of the EMT phenotype in TNBC by down-regulating Prrx1, thereby inhibiting cell migration and invasion during cancer progression.