miR-9 functions as a tumor suppressor in ovarian serous carcinoma by targeting TLN1.

microRNAs (miRNAs) are important regulators of gene expression during tumorigenesis. The downregulation of microRNA-9 (miR-9) has been reported in ovarian serous carcinoma (OSC), indicating a role for miR-9 in this type of cancer. In this study, we investigated the biological significance of miR-9 in OSC in vitro. Using 3 OSC cell lines, SKOV3, CAOV3 and OVCAR3, which underexpresss miR-9, we demonstrate that the exogenous miR-9 transfection inhibits OSC cell proliferation, migration and invasion. In addition, we demonstrate that the focal adhesion protein, talin 1 (TLN1), whose expression has been associated with OSC development and progression to metastasis, is a direct target of miR-9. TLN1 knockdown mimicked the effects of miR-9 overexpression. Moreover, the activation of the TLN1-modulated FAK/AKT pathway was inhibited by the increased miR-9 levels. These results suggest that miR-9 plays a role as a tumor suppressor in OSC by suppressing TLN1 expression.