The Study On Functions And Mechanisms Of MiR-148a And MiR-409in The Metastasis Of Gastric Cancer

Emerging evidence has shown that aberrantly expressed microRNAs (miRNAs) are highly associated with tumour initiation, development and progression. However, little is known about the potential role of miRNAs in gastric cancer (GC) metastasis. In this study, we firstly investigate the role and related mechanism of miR-148a in gastric cancer (GC) metastasis. We found that miR-148a expression was suppressed by more than4folds in GC compared with their corresponding non-tumorous tissues, and the downregulated miR-148a was negatively associated with TNM stage and lymph-node metastasis. Functional assays demonstrated that overexpression of miR-148a suppressed GC cell migration and invasion in vitro and lung metastasis formation in vivo. In addition, we confirmed that ROCK1was a direct and functional target of miR-148a. overexpression of miR-148a in GC cells could reduce the mRNA and protein levels of ROCK1, whereas miR-148a silencing significantly increased ROCK1expression. Luciferase assays confirmed that miR-148a could directly bind to the two sites of3’untranslated region of ROCK1. Moreover, in GC tissues, we observed an inverse correlation between miR-148a and ROCK1expression. Knockdown of ROCK1significantly inhibited GC cell migration and invasion. We further found that ROCK1was involved in miR-148a-induced suppression of GC cell migration and invasion.Secondly, we investigated the role and mechanism of another miRN A in GC, and found that miR-409-3p was down-regulated in GC, and its expression was negatively associated with TNM stage and lymph node metastasis. Enforced expression of miR-409in GC cells significantly reduced their migration and invasion in vitro and their capacity to develop distal pulmonary metastases and peritoneal dissemination in vivo. Moreover, we found that miR-409exerted its function predominantly through the mature miR-409-3p but not miR-409-5p. Microarray and bioinformatics analysis identified the pro-metastatic gene Radixin (RDX) as a potential miR-409target. Further studies confirmed that miR-409-3p suppressed the expression of RDX by directly binding to its3’untranslated region. Silencing of RDX by siRNAs phenocopied the effects of miR-409overexpression, whereas restoration of RDX in miR-409overexpressed GC cells reversed the suppressive effects of miR-409.Taken together, by understanding the functions and molecular mechanisms of miR-148a and miR-409in GC, we found two novel anti-metastatic genes, miR-148a and miR-409, which respectively through targeting ROCK1and RDX inhibited GC cell migration and invasion. These results suggest that patients with downregulated miR-148a or miR-409are prone to lymph node metastasis and tumour progression. miR-148a and miR-409may have a therapeutic potential to suppress GC metastasis.