PDCD4 and breast cancer: To explore the biological function of the hsa_circ_0053063-miR-330-3p-PDCD4 axis and verify that hsa_circ_0053063 could increase PDCD4 protein level by absorbing miR-330-3p in BC, we performed rescue assays in MDA-MB-231 and MDA-MB-468 cell lines.