LEP and breast cancer: One of the first studies that explored the effect of leptin on EMT in mammary cancer cells was carried out by Yan et al. This study showed that in MCF7 cells, leptin stimulation induces a fibroblastoid morphology evidenced by the decrease in the expression of epithelial markers (occludin, E-cadherin) and an increase in mesenchymal markers (fibronectin, N-cadherin, and vimentin) [6].