Functional expression of vascular endothelial growth factor receptor Flt-1on squamous cell carcinoma of the head and neck

Vascular endothelial growth factor (VEGF) is one of the most potent factors in tumor-induced neoangiogenesis. After binding to its specific receptors KDR and FLT-1 on the endothelial cell surface cell proliferation and migrat ion are stimulated. Recently there has been some evidence for the expressio n of these receptors on tumor cells. We investigated the protein and mRNA e xpression of KDR and FLT-1 in native tissues and tumor cell cultures from s quamous cell carcinomas of the head and neck (HNSCC) and analyzed their in vitro functional significance for tumor cell proliferation and migration. A part from the expected expression of VEGF receptors on endothelial cells we observed a tumor cell-specific localization of FLT-1 in 29 tumors and KDR in 16 of 37 tumors analyzed. Functional studies in vitro revealed that the addition of VEGF to HNSCC cells inhibited the proliferation and migration o f these cells in a dose-dependent manner. Our data suggest a potential nega tive regulatory loop for VEGF and FLT1 when tumor cells have an insufficien t blood supply.