The 4FR6D3 antibody recognizes human CD334, also known as fibroblast growth factor 4, FGFR4 and TKF. CD334 is a member of the fibroblast growth factor receptor family and a cell surface tyrosine kinase containing three immunoglobulin-like domains. FGFR4 has a predicted molecular weight of approximately 88 kD and is widely expressed in many tissues including the intestine, muscle, heart, cornea, retina, and pancreas, with highest expression in lung and kidney.CD334 binds acidic fibroblast growth factors (FGF8, GFG1, FGF19, FGF6, and FGF2); ligand binding induces mitogenesis and differentiation. CD334 has been shown to interact with STAT1 and STAT3 and is over-expressed in gynecological tumors suggesting a possible role for this receptor in breast and ovarian tumorigenesis. Unique alleles (Arg388) in FGFR4 have been shown to be associated with cancer progression and increased tumor cell motility. The 4FR6D3 antibody has been shown to be useful for flow cytometry.