Inhibition of cell migration and angiogenesis by the amino-terminal fragment of 24kD basic fibroblast growth factor

The 24-kDa form of basic fibroblast growth factor inhibits the migration of endothelial cells and mammary carcinoma cells while continuing to promote cell proliferation. This molecule consists of the 18-kDa fibroblast growth factor sequence plus an additional 55 amino acids at the amino-terminal end. Antibody neutralization studies suggested that the inhibition of migration is associated with these 55 amino acids, whereas the promotion of proliferation localizes to the 18-kDa domain. To determine whether 24kD basic fibroblast growth factor could be modified to eliminate its effect on cell proliferation but retain its inhibition of migration, portions of the carboxyl-terminal end of 24kD fibroblast growth factor were deleted, and the products were tested on MCF-7 and endothelial cells. A protein consisting of the 55 amino acids of the amino-terminal end and the first 31 amino acids of 18kD basic fibroblast growth factor (ATE+31) inhibited migration by 80% but did not promote cell growth. Arginine to alanine substitutions within the first 21 amino acids of the carboxyl-terminal end substantially reduced the efficacy of ATE+31, whereas substitutions in the remaining part of the molecule had no effect. Competition binding experiments showed that ATE+31 does not compete with 24kD basic fibroblast growth factor for binding to fibroblast growth factor receptor 1. In an in vivo matrigel plug assay, 150 nm ATE+31 peptide reduced angiogenesis by 80%. These studies demonstrate that the amino-terminal end of 24kD basic fibroblast growth factor is responsible for an activity that inhibits the migration rates of cultured cells as well as the angiogenic response in vivo.