CDK13 and posterior cortical atrophy: To further validate the role of the formation of CDK13-circCDK13-miR-212-5p/miR-449a-E2F5 regulatory axis in PCa cell proliferation, we performed loss- and gain-of-function experiments in which circCDK13 and E2F5 were forcedly expressed or depleted in PC3 and 22RV1 cells.