Fibroblast growth factor 8B (FGF-8B) is a member of the fibroblast growth factor (FGF) family and is an isoform of FGF-8. Cytokines in the FGF family possess broad mitogenic and cell survival activities (Folkman andamp; Klagsbrun; Kimelman andamp; Kirschner) and are involved in a variety of biological processes, including cell proliferation, differentiation, survival, and apoptosis (Folkman andamp; Klagsbrun; Klagsbrun; Rifkin andamp; Moscatelli). FGF-8B signals through FGF receptors (FGFRs) to activate PI3K and MAPK pathways. FGF-8B is broadly associated with mitogenic and cell survival activities, and regulates gastrulation, epithelial-mesenchymal transition, and later on mesenchymal to epithelial differentiation during embryonic development. FGF-8B has also been found in peripheral blood leukocytes and healthy bone marrow samples (Mattila andamp; Härkönen). FGF-8B has mitogenic effects on somatic cells in the germinal epithelium and is expressed in adult mouse ovarian cells and tissues, which suggests that it regulates maturation of oocytes and seminiferous epithelium in testis (Valve et al.).