Leptin-inhibition effects on levels of human and mouse VEGF/VEGFR2 and leptin/OB-Rb in SCID mice. Human and mouse vascular endothelial growth factor (hVEGF and mVEGF) and human and mouse leptin (hLeptin and mLeptin) concentrations in tumor lysates and plasma, and western blot results for human VEGF and vascular endothelial growth factor receptor type 2 (VEGFR2) (mouse and human) and for human leptin receptor (OB-Rb) in MCF-7 breast cancer (BC) (a,c) and MDA-MB231 BC (b,d), respectively. β-Actin was used as a loading control for western blot analysis. *P < 0.05 and **P < 0.01, significant difference in mice treated with pegylated leptin peptide receptor antagonist 2 (PEG-LPrA2) with respect to control mice receiving pegylated scrambled peptide, respectively. Data (mean ± standard error) show representative results (n = 10 tumors/treatment). MT, mammary tumor.