Vascular endothelial growth factor receptor-3 (VEGFR-3) plays a major role in lymph-angiogenesis, tumor growth and metastatic tumor cell dissemination. The receptor is over-expressed on lymphatic vessels in the vicinity of tumors and on the tumor vasculature and therefore may be an excellent target for an effective cancer intervention. We generated and characterized single chain antibody fragments (scFv) recognizing VEGFR-3 by phage display technology and expression in P. pastoris and analyzed selected antibodies in vitro and in vivo. The scFvs were functionalized by the introduction of cysteines at the C-terminal end of the proteins. The scFvs are species cross-specific and bind to recombinant human and mouse VEGFR-3. ScFv AFC5 showed specific tumor accumulation in an hVEGFR-3 expressing F9 terato-carcinoma mouse model, which was also used for tumor visualization by combined single proton emission computed tomography (SPECT/CT) and immunohistochemical analysis. This antibody also inhibited binding of hVEGF-C to its receptor and reduced proliferation of human lymphatic endothelial cells. Thus, the generated VEGFR-3 specific scFv antibodies represent a valuable tool for novel cancer therapies and diagnostic applications.

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