Jitka Vera Olander

Tumor vascular permeability factor stimulates endothelial cell growth and angiogenesis.

Vascular permeability factor (VPF) is an Mr 40-kD protein that has been purified from the conditioned medium of guinea pig line 10 tumor cells grown in vitro, and increases fluid permeability from blood vessels when injected intradermally. Addition of VPF to cultures of vascular endothelial cells in vitro unexpectedly stimulated cellular proliferation. VPF promoted the growth of new blood vessels when administered into healing rabbit bone grafts or rat corneas. The identity of the growth factor activity with VPF was established in four ways: (a) the molecular weight of the activity in preparative SDS-PAGE was the same as VPF (Mr approximately 40 kD); (b) multiple isoforms (pI greater than or equal to 8) for both VPF and the growth-promoting activity were observed; (c) a single, unique NH2-terminal amino acid sequence was obtained; (d) both growth factor and permeability-enhancing activities were immunoadsorbed using antipeptide IgG that recognized the amino terminus of VPF. Furthermore, 125I-VPF was shown to bind specifically and with high affinity to endothelial cells in vitro and could be chemically cross-linked to a high-molecular weight cell surface receptor, thus demonstrating a mechanism whereby VPF can interact directly with endothelial cells. Unlike other endothelial cell growth factors, VPF did not stimulate [3H]thymidine incorporation or promote growth of other cell types including mouse 3T3 fibroblasts or bovine smooth muscle cells. VPF, therefore, appears to be unique in its ability to specifically promote increased vascular permeability, endothelial cell growth, and angio-genesis.

Specific binding of vascular permeability factor to endothelial cells.

Vascular permeability factor (VPF), also known as vascular endothelial cell growth factor, has recently been purified from guinea pig, human, and bovine sources. We show that various fetal or adult endothelial cell strains originating from either capillary or large vessels possess specific high affinity and saturable binding sites for guinea pig tumor-derived [125I]VPF. Two classes of sites with KDs of approximately 10 pM and 1 nM were detected for all endothelial cell types examined. Guinea pig [125I]VPF binding to endothelial cells was inhibited by human VPF (ID50 = 0.8 ng/ml) and by suramin (ID50 = 75 micrograms/ml) but not by heparin. Cross-linking experiments revealed specific [125I]VPF-receptor complexes of two types. Most of the complexes migrated very slowing in SDS-PAGE, indicating that they were of very high molecular weight and probably highly cross-linked. A portion of the molecules migrated as 270 kDa complexes, indicating that the molecular weight of the endothelial cell VPF receptor is about 230 kDa.