Receptor binding and mitogenic properties of mouse fibroblast growth factor 3. Modulation of response by heparin

fgf3 has been implicated in the embryonic and fetal development of the mouse and as an oncogene in murine breast cancer. We describe a procedure to purify the product of the mouse fgf3 gene and show it to be a potent mitogen for some epithelial cell lines. Using a receptor binding competition assay, Fgf3 was shown to bind with high affinity to the IIIb isoforms of Fgf receptor (FgfR) 1 and FgfR2 (ID50 = approximately 0.8 nM) and with a lower affinity to the IIIc variant of FgfR2 (ID50 = approximately 9 nM). No competition for the binding of 125I-Fgf1 was observed for FgfR1 (IIIc), FgfR3 (IIIb and IIIc), or FgfR4. Mitogenicity assays using BaF3 cells containing individual Fgf receptors showed a pattern of response in agreement with the receptor binding results. A comparison of two mammary epithelial cell lines showed a marked difference of potency and dependence upon heparin in their response to mouse Fgf3, suggesting a complex interaction between the ligand and its low and high affinity receptors.