Proliferation, angiogenesis, and inflammation-related molecules in estrogen receptor positive and negative breast cancer xenografts. (a) Estrogen-receptor-positive MCF-7 breast cancer (BC) and (b) estrogen-receptor-negative MDA-MB231 BC from control (pegylated scrambled peptide) and pegylated leptin peptide receptor antagonist 2 (PEG-LPrA2)-treated SCID mice. Pictures show representative results from immunohistochemical analysis of pro-proliferative and pro-angiogenic molecules (n = 5; magnification x100). Arrows indicate stronger staining of the antigens in tumors from controls than tumors from PEG-LPrA2-treated mice. IL-1R tI, interleukin-1 receptor type I; OB-R, leptin receptor; PCNA, proliferating cell nuclear antigen; VEGF, vascular endothelial growth factor; VEGFR2, vascular endothelial growth factor receptor type 2.