Keratinocyte growth factor (KGF), a member of the fibroblast growth factor family, is a mesenchymally derived mediator of epithelial cell proliferation and migration. In a previous study, we reported that KGF enhanced the motility of human breast cancer cells. The objective of the present study was to examine the influence of specific and non-specific KGF inhibitors on KGF-induced motility and proliferation in ER-positive MCF-7 cells.In the present study three KGF inhibitors were employed [Heparin, Innohep, a low molecular weight heparin (LMWH) and KGFR2 beta (IIIb)/Fc, a chimeric KGFR fragment]. Heparin and LMWH bind to low affinity sites on KGF and produce non-specific inhibition, while KGFR2 beta (IIIb)/Fc, a soluble chimera of an extracellular KGFR fragment, is a more specific KGF inhibitor. Cellular motility was measured using two methods: culture wounding over a period of 48 hours; and secondly, time-lapse videomicroscopy (TLVM).In these experiments KGF was found to produce a dose-dependent enhancement of MCF-7 cell motility over a dosage range of 5 to 500 ng/ml. In the TLVM experiments, Heparin (30 ng/ml), LMWH (30 ng/ml) and KGFR2 beta (IIIb)/Fc (50 micrograms/ml) completely inhibited KGF-induced motility of MCF-7 cells during the initial 2-hour observation period. In the culture wounding assay, LMWH produced a greater reduction in KGF-induced motility than heparin at 48 hours post-treatment.The results of this study indicate that KGF-mediated enhancement of breast cancer cells motility and proliferation is inhibited by both specific and non-specific KGF inhibitors. LMWH appears to produce an inhibition of KGF with a much longer duration of action than Heparin. Our results suggest that KGF inhibition may be a potential new therapeutic approach for the treatment of metastatic breast cancer.