Acid fibroblast growth factor (FGF acid), also known as FGF-1, ECGF, and HBGF-1, is a secretory mitogen that can stimulate the proliferation of all cells from the mesoderm and neuroectoderm, ectoderm, and endoderm. It plays a role in development, regeneration, and angiogenesis. Internalized FGF acid can be transferred to the cytoplasm with the help of Hsp90, and then migrate to the nucleus through its two nuclear localization signals. PKC δ Phosphorylated FGF acid can trigger active output into the cytoplasm, where dephosphorylation and degradation occur. Within cells, FGF acid acts as a survival factor by inhibiting p53 activity and promoting apoptosis signaling.