With a series of experiments, we eventually elucidated that miR-30a targeted the 3'UTR of SOX4 and formed a double-negative loop with SOX4 to inhibit EMT and stem cell-like phenotypes in breast cancer via blockade of TGF-β/SMAD signaling pathway both in vitro and in vivo. The gene discussed is TGFB1; the disease is breast cancer.