TGFB1 and breast cancer: Furthermore, leptin was reported to stimulate the secretion of TGFβ, which leads to the activation of SMAD family member 2 (Smad2), Smad3, and Smad4 transcription factors, the repression of cadherin 1 (CDH1) coding for E-cadherin, and an increased CSC phenotype in breast cancer cells [203].