LEP and breast cancer: The effect of leptin over cell growth has been determined in MCF-7, MDA-MB231, SK-BR-3, T47D, and ZR-75-1 breast cancer cell lines, mediated by diverse signaling pathways when a single stimulus of the protein is applied and is incubated between 24 and 96 h [21, 27, 37, 38, 48, 49].