SMAD3 and breast cancer: Similarly, breast cancer derived MSCs (BC-MSCs) promote EMT and maintain a stable mesenchymal state of BC cells via paracrine mechanisms or induce BC cells to autocrine TGF-β1, zinc finger E-box-binding protein 1(ZEB1)/miR-200 regulatory loop, TGF-β-Smad3 signaling pathway may be involved in this process [76, 77].