Dual activities of 22-24 kDa basic fibroblast growth factor: Inhibition ofmigration and stimulation of proliferation

Basic fibroblast growth factor (FGF2) is synthesized as four isoforms with molecular weights of 24, 22.5, 22, and 18 kDa, with each of the three highe r molecular weight forms (hmwFGF2) produced by the initiation of translatio n at one of three upstream CUG codons. We have shown that bovine arterial e ndothelial cells export the high molecular weight forms of FGF2 (hmwFGF2) i n a 17 beta-estradiol-dependent manner (Piotrowicz et at., 1997, J Biol Che m 272:7042-7047). To determine whether the hmwFGF2 forms affected cell beha vior after release, we evaluated the effect of recombinant hmwFGF2 on the g rowth and migration of endothelial cells and mammary carcinoma cells (MCF-7 ). Treatment with the recombinant protein resulted in the inhibition of end othelial cell migration by 45% and MCF-7 cell migration by 70%. HmwFGF2-dep endent inhibition was observed when endothelial cell migration was stimulat ed by 18 kDa FGF2 or vascular endothelial growth, and MCF cell migration wa s stimulated with insulinlike growth factor. in each case, inclusion of an antibody against the 55 amino acid amino terminal end of 24 kDa FGF2 abroga ted the inhibition of migration, while antibodies to the 18 kDa FGF2 domain had no effect. When endothelial cells were cultured under conditions which promoted export of hmwFGF2, a 40% decrease in motility was observed which was reversed by the antibodies to the 24 kDa FGF2. Thus, both recombinant a nd endogenously produced hmwFGF2 are capable of inhibiting migration. in co ntrast to the ubiquitous effect on migration, hmwFGF2 had no effect on endo thelial cell growth but stimulated MCF-7 growth equally as well as the 18 k Da FGF2 (threefold). Antibodies to the 18 kDa domain of 24 kDa FGF2 blocked the growth-promoting activity of hmwFGF2, but those to the amino terminal end were ineffective. These data suggest that hmwFGF2 has dual activities, an inhibitory effect on cell migration and a growth-stimulating effect. The two activities can be localized to different parts of hmwFGF2: inhibitory activity to the amino terminal 55 amino acids (which are absent from the 18 kDa FGF2) and growth-promoting activity to the 18 kDa domain. Therefore, t he ratio of hmwFGF2 and 18 kDa FGF2 in the extracellular space may provide a mechanism of control for angiogenesis and mammary tumor development. J Ce ll Physiol 178:144-153, 1999. (C) 1999 Wiley-Liss, Inc.