miR-367 promotes epithelial-to-mesenchymal transition and invasion of pancreatic ductal adenocarcinoma cells by targeting the Smad7-TGF-β signalling pathway

Background: Aberrant Smad7 expression contributes to the invasion and metastasis of pancreatic cancer cells. However, the potential mechanism underlying aberrant Smad7 expression in human pancreatic ductal adenocarcinoma (PDAC) remains largely unknown. Methods: Bioinformatic prediction programmes and luciferase reporter assay were used to identify microRNAs regulating Smad7. The association between miR-367 expression and the overall survival of PDAC patients was evaluated by Kaplan-Meier analysis. The effects of miR-367 and Smad7 on the invasion and metastasis of pancreatic cancer cells were investigated both in vitro and in vivo. Results: We found that miR-367 downregulated Smad7 expression by directly targeting its 30-UTR in human pancreatic cancer cells. High level of miR-367 expression correlated with poor prognosis of PDAC patients. Functional studies showed that miR-367 promoted pancreatic cancer invasion in vitro and metastasis in vivo through downregulating Smad7. In addition, we showed that miR-367 promoted epithelial-to-mesenchymal transition by increasing transforming growth factor-beta (TGF-beta)-induced transcriptional activity. Conclusions: The present study identified and characterised a signalling pathway, the miR-367/Smad7-TGF-beta pathway, which is involved in the invasion and metastasis of pancreatic cancer cells. Our results suggest that miR-367 may be a promising therapeutic target for the treatment of human pancreatic cancer.