Leptin upregulation of VEGF/VEGFR-2 is mediated by leptin-induced JAK/STAT3-Notch expression while also showing that leptin regulation of VEGF/VEGFR2 in breast cancer involves the activation of Src and Gbr2/Gab2/STAT3, suggesting crosstalk with Rho-GTPases. This evidence concerns the gene GAB2 and breast carcinoma.