MicroRNA-125b and microRNA-205 overexpression and microRNA-424 expression silencing increase aggressiveness in MCF-7aro cells. (A) Primary mammospheres (PMs) formation assay. MCF-7aro, Res-Let, Res-Ana and MCF-7aro cells transfected by microRNA (miR)-125b-5p or miR-205-5p mimic, miR-424-3p inhibitor or their negative controls were cultured in nonadherent mammosphere culturing conditions. (B) Second-generation mammospheres generated from the PMs shown in (A). Data given in (A) and (B) are the mean ± SD of three independent experiments. (C) Growth kinetics of MCF-7aro, Res-Ana and Res-Let cells in steroid-free medium. (D) Growth kinetics in steroid-free conditions of MCF-7aro cells transiently transfected with either the negative control of mimics, miR-125b-5p or miR-205-5p or (E) the negative control of inhibitor or miR-424-3p inhibitor. (C), (D) and (E) show the results representative of at least three independent experiments. *P < 0.05, **P < 0.01 and ***P < 0.001 (Student’s t-test).