MicroRNA-545 suppresses progression of ovarian cancer through mediating PLK1 expression by a direct binding and an indirect regulation involving KDM4B-mediated demethylation.

Background: Ovarian cancer (OC) is a life-threatening gynecological malignancy where dysregulation of microRNAs (miRNAs) is frequently implicated. This study focuses on the function of miR-545 on OC development and the molecules involved.
Methods: miR-545 expression in OC tissues and cell lines was determined, and its link to the survival of patients was analyzed. Altered expression of miR-545 was induced to determine its role in proliferation, apoptosis, migration and invasion of OC cells and the angiogenesis ability of human umbilical vein endothelial cells (HUVECs). The targeting mRNAs of miR-545 were predicted and validated through luciferase assays. Gain-of-function studies of KDM4B and PLK1 were performed to explore their involvements in OC development. In vivo experiments were conducted by inducing xenograft tumors in nude mice.
Results: Poor expression of miR-545 was found in OC tissues and cells compared to the normal ones and it indicated unfavorable prognosis in patients. Overexpression of miR-545 suppressed growth, migration, invasion and angiogenesis of OC cells as well as the angiogenesis ability of HUVECs. miR-545 was found to target mRNAs of KDM4B and PLK1, while KDM4B promoted the transcription of the PLK1 promoter through demethylation of H3K9me3. Either overexpression of KDM4B or PLK1 partially blocked the inhibitory effects of miR-545 mimic on OC cell growth, especially the former one. The in vitro results were reproduced in vivo.
Conclusion: This study evidenced that miR-545 suppresses progression of OC through mediating PLK1 expression by a direct binding and an indirect regulation involving KDM4B-mediated demethylation.