Down-regulation of vascular endothelial growth factor expression by anti-Her2/neu single chain antibodies.

HER-2/neu is overexpressed in 25-30% of breast tumors. Signaling through HER-2/neu leads to an increase in the production of vascular endothelial growth factor (VEGF) and enhances angiogenesis. We evaluated the effects of three specific anti-HER2/neu single chain-Fv (scFv) antibodies on the expression level of VEGF in HER2/neu-expressing breast cancer cell lines. A nonimmunized human scFv library was panned against three epitopes of HER2/neu. BT-474 human breast cancer cell line was treated with three specific anti-HER2/neu scFv antibodies and the amount of VEGF gene transcript was determined by quantitative real-time PCR. The expression of VEGF protein was analyzed by western blot. All three scFv antibodies along with their combination inhibited VEGF expression at both the gene and protein levels. Our results show that anti-HER2/neu recombinant antibodies can be considered as anti-angiogenic agents in HER2/neu-positive breast cancers.