PHOSPHOROTHIOATE OLIGODEOXYNUCLEOTIDES BIND TO BASIC FIBROBLAST GROWTH-FACTOR, INHIBIT ITS BINDING TO CELL-SURFACE RECEPTORS, AND REMOVE ITFROM LOW-AFFINITY BINDING-SITES OIL EXTRACELLULAR-MATRIX

We studied the interactions of phosphorothioate oligodeoxynucleotides and heparin-binding growth factors. By means of a gel mobility shift a ssay, we demonstrated that phosphodiester and phosphorothioate homopol ymers bound to basic fibroblast growth factor (bFGF). Binding of a pro be phosphodiester oligodeoxynucleotide could also be shown for other p roteins of the FGF family, including acidic fibroblast growth factor ( aFGF), Kaposi's growth factor (FGF-4) as well as for the bFGF-related vascular endothelial growth factor, VEGF. No binding to epidermal grow th factor (EGF) was observed. In addition, using a radioreceptor assay , we have shown that phosphorothioate homopolymers of cytidine and thy midine blocked binding of not only I-125-bFGF, but also of I-125-PDGF to NIH 3T3 cells, whereas phosphodiester oligodeoxynucleotides were in effective. The extent of blockade of binding was dependent on the chai n length of the phosphorothioate oligodeoxynucleotide. Furthermore, we have examined the effects of 18-mer phosphorothioate oligodeoxynucleo tides of different sequences on I-125-bFGF binding to low and high aff inity sites on both NIR 3T3 fibroblasts and DU-145 prostate cancer cel ls. Despite the fact that we have observed inhibition of bFGF binding by the 18-mer phosphorothioate oligodeoxynucleotides for both the high and low affinity classes of bFGF receptor, the inhibition was sequenc e-selective only for the high affinity receptors. We have also demonst rated that phosphorothioate homopolymers of cytidine and thymidine rel ease bFGF bound to low affinity receptors in extracellular matrix (ECM ). Finally, the most potent phosphorothioate oligodeoxynucleotides use d in these experiments (e.g. SdC28) were inhibitors of bFGF-induced DN A synthesis in NIH 3T3 cells.