MiR-206 suppresses epithelial mesenchymal transition by targeting TGF-β signaling in estrogen receptor positive breast cancer cells

Background: Previous reports have shown a mutual negative feedback loop between microRNA (miR)-206 and estrogen receptor (ER) expression. Furthermore, decreased miR-206 expression in breast cancer (BC) is associated with the advanced clinical stage and lymph node metastasis. However, its role and the mechanism underlying the migration and invasion of ER positive BC remain unclear. Results: In this study, miR-206 was stably transfected into ER positive cell lines MCF-7 and T47D to investigate the effect of miR-206. The results showed that miR-206 overexpression markedly impaired the migration and invasive abilities of these cells, followed by suppression of the epithelial mesenchymal transition (EMT). Mechanistic analyses showed that miR-206 inhibited the autocrine production of transforming growth factor (TGF)-beta as well as the downstream expression of neuropilin-1 (NRP1) and SMAD2, responsible for the decreased migration, invasion, and EMT in these cells. Conclusions: Our data demonstrate that miR-206 inhibits TGF-beta transcription and autocrine production, as well as downstream target genes of EMT. Restoring miR-206 expression may provide an effective therapeutic strategy for ER positive BC.