Regulation of vascular endothelial growth factor production and angiogenesis by the cytoplasmic tail of tissue factor

Tissue factor (TF), a transmembrane receptor for coagulation factor VII/VII a, is aberrantly expressed in human cancers. We demonstrated a significant correlation between TF and vascular endothelial growth factor (VEGF) produc tion in 13 human malignant melanoma cell lines (r(2) = 0.869, P < 0.0001). Two of these cell lines, RPMI-7951, a high TF and VEGF producer, and WM-115 , a low TF and VEGF producer, were grown s.c. in severe combined immunodefi cient mice. The high-producer cell line generated solid tumors characterize d by intense vascularity, whereas the low producer generated relatively ava scular tumors, as determined by immunohistologic staining of tumor vascular endothelial cells with anti-von Willebrand factor antibody. To investigate the structure-function relationship of TF and VEGF, a low-producer melanom a cell line (HT144) was transfected with a TF cDNA containing the full-leng th sequence, a cytoplasmic deletion mutant lacking the coding sequence for the distal three serine residues (potential substrates for protein kinase C ), or an extracellular domain mutant, which has markedly diminished functio n for activation of factor X, Cells transfected with the full-length sequen ce produced increased levels of both TF and VEGF, Transfectants with the fu ll length sequence and the extracellular domain mutant produced approximate ly equal levels of VEGF mRNA, However, cells transfected with the cytoplasm ic deletion mutant construct produced increased levels of TF, but little or no VEGF, Thus, the cytoplasmic tail of TF plays a role in the regulation o f VEGF expression in some tumor cells.