miR-324-5p inhibits gallbladder carcinoma cell metastatic behaviours by downregulation of transforming growth factor beta 2 expression

Increasing studies have demonstrated that microRNAs (miRNAs) are associated with the metastasis of gallbladder carcinoma (GBC). Recently, miR-324-5p has been reported to be a tumour-suppressive miRNA in many types of malignant cancer. However, the biological function and molecular mechanism of miR-324-5p in GBC still remain largely unknown. Here, we found that miR-324-5p expression was notably down-regulated in both GBC tissues and cells compared with that in normal controls. Downregulated miR-324-5p expression was negatively associated with the status of local invasion and lymph node metastasis and predicted a poor prognosis in GBC patients. Further functional assays revealed that restoration of miR-324-5p significantly suppressed GBC cell migration, invasion and epithelial-mesenchymal transition (EMT) in vitro and impeded the metastasis of GBC cells in vivo. Moreover, RNA immunoprecipitation (RIP) and dual-luciferase reporter assay confirmed that the transforming growth factor beta 2 (TGFB2) was a direct target gene of miR-324-5p in GBC cells. Mechanically, small interfering RNA (siRNA)-mediated knockdown of TGFB2 partially phenocopied the inhibitory effects of miR-324-5p overexpression on GBC cell metastatic phenotypes. In summary, our findings demonstrated that miR-324-5p targets TGFB2 expression to inhibit GBC cell metastatic behaviors, and implying miR-324-5p as a potential biomarker for diagnostic and therapeutic strategies in GBC.