MicroRNA-125b suppresses the epithelial–mesenchymal transition and cell invasion by targeting ITGA9 in melanoma

Increasing evidence has shown that aberrant miRNAs contribute to the development and progression of human melanoma. Previous studies have shown that miR-125b functions as a suppressor in malignant melanoma. However, the molecular function and mechanism by which miR-125b influences melanoma growth and invasion are still unclear. In this study, we aimed to investigate the role of miR-125b in melanoma progression and metastasis. We found that miR-125b expression is significantly downregulated in primary melanoma, and an even greater downregulation was observed in metastatic invasion. Restored expression of miR-125b in melanoma suppressed cell proliferation and invasion both in vitro and in vivo. Furthermore, our findings demonstrate that upregulating miR-125b significantly inhibits malignant phenotypes by repressing the expression of integrin alpha9 (ITGA9). Finally, our data reveal that upregulated expression of ITGA9 in melanoma tissues is inversely associated with miR-125b levels. Together, our results demonstrate that upregulation of ITGA9 in response to the decrease in miR-125b in metastatic melanoma is responsible for melanoma tumor cell migration and invasion.