Tumor-derived adhesion factor (TAF) was previously identified as a cell adhesion molecule secreted by human bladder carcinoma cell line EJ-1.

Although the significance of vascular endothelial growth factor (VEGF) and its receptors in angiogenesis is well established, the signal transduction cascades activated by VEGF and their involvement in mediating the mitogenic response of endothelial cells to VEGF are incompletely characterized. Here we demonstrate that VEGF activates mitogen-activated protein (MAP) kinases, including the extracellular signal-regulated protein kinase (ERK) and p38 MAP kinase, phosphatidylinositol 3-kinase (PI 3-kinase), and p70 S6 kinase in human umbilical vein endothelial cells (HUVEC). The activation of these enzymes was assayed by kinase phosphorylation and by kinase activity towards substrates. Studies with PI 3-kinase inhibitors revealed that activation of p70 S6 kinase was mediated by PI 3-kinase. Selective inhibition of ERK, PI 3-kinase, and p70 S6 kinase with the inhibitors PD098059, LY294002, and rapamycin, respectively, inhibited VEGF-stimulated HUVEC proliferation. In marked contrast, the p38 MAP kinase inhibitor SB203580 not only failed to inhibit but actually enhanced HUVEC proliferation; this effect was associated with the phosphorylation of Rb protein. Rb phosphorylation resulted from a decrease in the level of the cdk inhibitor p27KiP1. These results indicate that the activities of ERK, PI 3-kinase, and p70 S6 kinase are essential for VEGF-induced HUVEC proliferation. p38 MAP kinase suppresses endothelial cell proliferation by regulating cell-cycle progression.

Perlecan, a widespread heparan sulfate proteoglycan, functions as a bioactive reservoir for growth factors by stabilizing them against misfolding or proteolysis. These factors, chiefly members of the fibroblast growth factor (FGF) gene family, are coupled to the N-terminal heparan sulfate chains, which augment high affinity binding and receptor activation. However, rather little is known about biological partners of the protein core. The major goal of this study was to identify novel proteins that interact with the protein core of perlecan. Using the yeast two-hybrid system and domain III of perlecan as bait, we screened ϳ0.