TGF-β/Smad signaling plays an important role in the progression of EMT in breast cancer, in which phosphorylation of Smad2 triggers the formation of a complex between Smad2 and Smad4, resulting in nuclear translocation of the Smad2/Smad4 complex and subsequent gene transcription (12, 33, 34). Here, SMAD2 is linked to breast cancer.