The angiogenic receptor KDR is widely distributed in human tissues and tumours and relocates intracellularly on phosphorylation. An immunohistochemical study

AIMS: Angiogenesis is an important factor in tumour growth and metastasis. Vascular endothelial growth factor receptor 2 (VEGFR-2) or KDR plays a crucial role in angiogenesis. The aim of this study was to raise and characterize antibodies against phosphorylated KDR which could be used for studies on human tissues to assess KDR activation and novel inhibitors of KDR activation in clinical trials. METHODS AND RESULTS: Three monoclonal antibodies and one rabbit polyclonal antiserum were produced. The specificity of the antibodies was confirmed by ELISA. One of the mouse antibodies and the rabbit polyclonal antiserum reacted with a 200-kDa band on a Western blot of human umbilical vein endothelial cell (HUVEC) lysates, the molecular weight of KDR. Immunohistochemical staining showed that phosphorylated KDR is present in a wide variety of normal tissues including liver, colon and placenta, and is not restricted to endothelium. It was also present in a number of human tumours including breast carcinomas, colonic carcinomas and non-Hodgkin's lymphomas. The pattern of staining was membranous, cytoplasmic and nuclear. CONCLUSIONS: This study has shown that phosphorylated KDR is present in a wide variety of tumour and tissue types and is not confined to endothelium.