| Abstract: | Two polypeptides from secretory products of human hepatoma cells were isolated and characterized on the basis of their stimulation of maintenance and growth of human endothelial cells in serum-free cell culture. Both factors were purified to homogeneity by a combination of reverse-phase, ion exchange, and molecular filtration high performance liquid chromatography. One factor (endothelial cell growth factor (ECGF-2a) had Mr approximately 6,500 and pI near 6. The second (ECGF-2b) had Mr = 27,000 and a pI below 4.0. Both ECGF-2a and ECGF-2b exhibited single NH2-terminal sequences. The first 25 NH2-terminal residues of ECGF-2a and the first 49 residues of ECGF-2b were determined by gas-phase microsequencing. All clearly determined residues of ECGF-2a were identical with human pancreatic secretory trypsin inhibitor. All assignable residues of ECGF-2b were identical with urinary glycoprotein proteinase inhibitor (HI-30/EDC1). Both proteins are absent or at low levels in normal plasma and urine, but appear during acute inflammatory disease and cancer. Amino acid composition of ECGF-2a and ECGF-2b was also similar to human pancreatic secretory inhibitor and HI-30/EDC1, respectively. Both ECGF-2a and ECGF-2b inhibited bovine pancreatic trypsin (2 micrograms/ml) by 50% at 750 ng/ml. ECGF-2a and ECGF-2b stimulated endothelial cell number at a half-maximal dose of 50 ng/ml (8 nM) and 80 to 130 ng/ml (5 to 9 nM) protein, respectively. When assayed under identical conditions, no effect of either factor on human smooth muscle cells, human hepatoma cells, or human, rat, and mouse fibroblasts could be detected. |
