Characterization of a Mr 20,000 basic fibroblast growth factor-like protein secreted by normal and transformed fetal bovine aortic endothelial cells

Abstract

A mitogenic and plasminogen activator (PA)-inducing activity for endothelial cells has been identified in serum-free culture medium of normal AG 7680 and transformed tumorigenic GM 7373 fetal bovine aortic endothelial (FBAE) cells. The activity binds to heparin-Sepharose and it is quenched by polyclonal antihuman placental basic fibroblast growth factor (bFGF) antibodies. In the serum-free conditioned medium of FBAE cells, the anti-bFGF antiserum recognizes an immunorective M r 20,000 molecule which co-purifies with the mitogenic and PA-inducing activity on a heparin-Sepharose column. The partially purified M r 20,000 bFGF-like molecule competes with the typical M r 18,000 125I-bFGF form for the binding to high-affinity bFGF receptors in intact GM 7373 cells. Immunoprecipitation of biosynthetically labeled GM 7373 cells with anti-bFGF antiserum confirms the presence of a M r 20,000 bFGF-like molecule in the conditioned medium of these cells and identifies the typical M r 16,000 and M r 18,000 bFGF forms and two high-molecular-weight immunoreactive M r 22,000 and M r 25,000 bFGF forms in their cell extract. Immunoreactive M r 20,000 bFGF is detectable also in the conditioned medium of transformed nontumorigenic FBAE GM 7372 cells and of adult bovine aortic endothelial cells, but not in the culture medium of nonendothelial cell types, including rat and mouse fibroblasts, human hepatoma, and human endometrial adenocarcinoma cells. The results indicate that bovine endothelial cells secrete a M r 20,000 bFGF-like molecule which shares several biological, biochemical, and immunological characteristics with the typical cell-associated M r 18,000 bFGF.