FGF-3 is a member of the fibroblast growth factor family. The mouse FGF-3, originally named Int-2, was identified as a proto-oncogene that is activated by nearby integration of mouse mammary tumor viruses in virus-induced tumors. The amplification of the FGF-3 gene has been found in many cancer types including squamous cell carcinoma, epithelial ovarian tumors, breast cancer, and bladder cancer. FGF-3 is also associated with tumor metastasis and recurrence in human hepatocellular carcinoma. Like many other FGF proteins, FGF-3 plays important roles during embryonic development. FGF-3 is required for normal inner ear development including placode induction, maintenance, and otic vesicle formation. The role of FGF-3 in ear development is conserved amongst different vetebrates including mouse, chicken, and zebrafish. It has been shown that FGF-3, FGF-8, and FGF-10 play redundant and unique roles in ear development. FGF-3 is also important for early hindbrain patterning. The hindbrain boundary cells-derived FGF-3 regulates the expression of multiple markers at hindbrain boundaries. The involvement of FGF-3 in cardiovascular development also has been reported and is described to be in two forms. The two forms of FGF-3 describe a secreted form that induces proliferation and another form that localizes in the nucleus and inhibits cell proliferation. The nuclear isoform binds rpS2 and this binding has been suggested to interfere with ribosomal biogenesis.