In addition, our study emphasizes that PTK787 effectively counteracts PDGF-BB-induced signalling in tumor cells despite a relatively low inhibitory effect for PDGFRs [IC50=580 nM vs. VEGFR-1 IC50, 77 nM; VEGFR-2 IC50, 37 nM (24)]. This evidence concerns the gene KDR and neoplasm.