KDR and neoplasm: In order to explore the possibility of VEGFR scintigraphy of primary tumors and their metastasis, some authors analyzed the binding properties of 123I-labelled VEGF165 (123I-VEGF165) and 123I-VEGF121 (that are the predominant VEGF human isoforms) to human umbilical vein endothelial cells, several human tumor cell lines, a variety of primary human tumors, and some adjacent non-neoplastic tissues, as well as normal human peripheral blood cells in vitro.