Functional studies showed that circPLEKHM3 acts as a competing endogenous RNA (ceRNA) for miR-9 to up-regulate BRCA1, DNAJB6 and KLF4, which subsequently contribute to the activation of the epithelial–mesenchymal transition (EMT), AKT1/P27kip1 and Wnt/β-catenin signaling pathways, and consequently suppress tumorigenesis and progression in ovarian cancer. This evidence concerns the gene KLF4 and ovarian cancer.