MiR-507 inhibits the migration and invasion of human breast-cancer cells through Flt-1 suppression

Vascular endothelial growth factor receptor-1/fms-related tyrosine kinase-1 (VEGFR-1/Flt-1) is a tyrosine kinase receptor that binds placental growth factor (PlGF). Flt-1 is also highly expressed in breast-cancer tissues and breast-cancer cell lines. However, the molecular mechanism by which Flt-1 promotes breast-cancer invasion and metastasis by binding to PlGF-1 is unclear. In this study, we discovered that PlGF-1 and Flt-1 played a key role in the migration and invasion of breast cancer. Flt-1 promoted the migration and chemotaxis of breast-cancer cells by binding to PlGF-1. In addition, Flt-1 was confirmed to be a direct target gene of miR-507. miR-507 up-regulation inhibited the invasion and metastasis of breast-cancer cells in vitro and in vivo. Flt-1 overexpression rescued the invasion partially caused by the ectopic expression of miR-507. miR-507 expression in breast-cancer tissues and cell lines was lower than that in adjacent non-neoplastic tissues and normal cells. Clinical analysis indicated that miR-507 was negatively correlated with tumor differentiation, lymphatic metastasis, and the expression of Flt-1 in breast cancer. Furthermore, we showed that miR-507 down-regulation was due to the hypermethylation of its promotor region. Our results indicated that miR-507 represented potential therapeutic targets in breast cancer by modulating Flt-1.