Our results show that YAP1 is a direct downstream target of miR-509-3p, and is both a major effector of miR-509-3p-mediated attenuation of migration and invasion, and an important effector in spheroid formation in ovarian cancer cells that contain higher levels of YAP1. YAP1, on 11q22, is frequently subject to copy number gains, mutations, and inappropriate expression in diverse types of cancer, and is considered an oncogene in ovarian and other cancers [34, 54–60]. This evidence concerns the gene YAP1 and ovarian cancer.