SMAD4 and breast cancer: To further investigate the molecular mechanisms of OLA1 regulated EMT resulting in drug resistance to breast cancer, biomarkers in TGF-β/Smad pathway including TGFβ1, TGFβ2, SMAD3, and SMAD4 were characterized in the following cell lines: MCF-7 and MCF-7-PTR, and MDA-MB-231 cells with or without OLA1 knockdown.