In addition to Snail, Slug is another other important TGF-β responsive transcription factor that promotes EMT in breast cancer.21,28 Like Snail, Slug expression increased in a time-dependent manner after TGF-β stimulation with robust expression observed within 3 h in both BT-549 and HCC1937 cells (Fig. 4a). This evidence concerns the gene SNAI1 and breast cancer.