MicroRNA-302b Suppresses Human Epithelial Ovarian Cancer Cell Growth by Targeting RUNX1

Background: The microRNA (miR)-302 family functions as a tumor suppressor in human cancer. However, its role in epithelial ovarian carcinoma (EOC) remains unknown. Here, we investigated the role of miR-302b and its target gene RUNX1 in EOC. Methods: The expression levels of miR-302b and RUNX1 were assessed by quantitative real-time PCR and western blotting. The effects of ectopic expression of miR-302b were evaluated by the MTT assay, colony forming assay and flow cytometry. RUNX1 was identified as a target of miR-302b and their interaction was confirmed by luciferase activity assays, RUNX1 silencing and overexpression of a RUNX1 mutant construct lacking the 3 ' UTR. The effect of miR-302b on the suppression of tumor growth was investigated in vivo in a xenograft mouse model. Results: MiR-302b levels were markedly decreased in EOC specimens. Ectopic expression of miR-302b in EOC cells inhibited cell proliferation and colony formation, induced G0/G1 arrest, and promoted apoptosis. RUNX1 was identified as a direct target of miR-302b, and knockdown of RUNX1 inhibited cell growth in a manner similar to miR-302b overexpression, whereas introduction of a 3 ' UTR mutant of RUNX1 reversed the suppressive effect of miR-302b. Furthermore, miR-302b overexpression led to the inactivation of the STAT3 signaling pathway in EOC cells and inhibited tumor growth in a xenograft mouse model. Conclusions: MiR-302b functions as a tumor suppressor in EOC by targeting RUNX1 and modulating the activity of the STAT3 signaling pathway. Copyright (C) 2014 S. Karger AG, Basel