FGF-8 (FGF-8b) is a heparin binding growth factor belonging to the FGF family. Proteins of this family play a central role during prenatal development and postnatal growth and regeneration of a variety of tissues, by promoting cellular proliferation and differentiation. There are 4 known alternate spliced forms of FGF8; FGF8A, FGF-8B, FGF-8E and FGF-8F. The human and murine FGF8 A and B are identical unlike human and mouse FGF8 E and F are 98% identical. FGF-8 targets mammary carcinoma cells and other cells expressing the FGF receptors. Recombinant human FGF-8 (FGF-8b) is a 22.5 kDa protein consisting of 194 amino acid residues.