Fibroblast growth factors are key proteins in many intercellular signaling networks. They normally remain attached to the extracellular matrix, which confers on them a considerable stability. The unrestrained accumulation of fibroblast growth factors in the extracellular milieu, either due to uncontrolled synthesis or enzymatic release, contributes to the pathology of many diseases. Consequently, the neutralization of improperly mobilized fibroblast growth factors is of clear therapeutic interest. In pursuing described rules to identify potential inhibitors of these proteins, gentisic acid, a plant pest-controlling compound, an aspirin and vegetarian diet common catabolite, and a component of many traditional liquors and herbal remedies, was singled out as a powerful inhibitor of fibroblast growth factors. Gentisic acid was used as a lead to identify additional compounds with better inhibitory characteristics generating a new chemical class of fibroblast growth factor inhibitors that includes the agent responsible for alkaptonuria. Through low and high resolution approaches, using representative members of the fibroblast growth factor family and their cell receptors, it was shown that this class of inhibitors may employ two different mechanisms to interfere with the assembly of the signaling complexes that trigger fibroblast growth factor-driven mitogenesis. In addition, we obtained evidence from in vivo disease models that this group of inhibitors may be of interest to treat cancer and angiogenesis-dependent diseases.The fibroblast growth factors (FGFs) 4 constitute one of the largest families of polypeptide growth factors. There are 22FGFs in humans and mice that differ significantly in both size (17-20 kDa) and sequence, although each contains a core homology region encompassing 120 -130 residues. Phylogenetic analyses suggest that the FGF genes can be arranged into seven subfamilies. All FGFs bind to heparin with high affinity (K d between 1-2 nM), except for the members of the FGF-19 subfamily (i.e.: FGF-15, -19, -21, and -23) that have little or no affinity for these glycosaminoglycans (1). Apart from the family comprising FGF-11 to FGF-14, FGFs exert their diverse biological actions by binding to a series of membrane tyrosine kinase receptors (FGFRs) that are encoded by four genes (2-4). For this reason the FGF family is currently considered to be constituted by 18 members.FGFs were first isolated in the 1980s from bovine brain extracts due to their mitogenic and angiogenic activities (5). The affinity of FGFs for heparin was recognized very soon after their discovery (6), although the physiological substrate for FGF in normal conditions is heparan sulfate, a proteoglycan whose glycoside moiety is a glycosaminoglycan like heparin. Although initially conceived as FGF traps and protectors, it was later shown that these proteoglycans also participate in FGF signaling, although they are not absolutely required (4,7,8).In addition to the effects on cell replication and angiogenesis observed initially, FGFs r...
