Acts as a carrier protein that release fibroblast-binding factors (FGFs) from the extracellular matrix (EM) storage and thus enhance the mitogenic activity of FGFs. Enhances FGF2 signaling during tissue repair, angiogenesis and in tumor growth. Found in a complex with FGFBP1, FGF1 and FGF2. Interacts with FGF1, FGF2, FGF7, FGF10, FGF22 and HSPG2. Extracellular and plasma membrane-associated. Colocalizes with HSPG2 in the pericellular environment of squamous cell carcinomas. Expressed in the suprabasal region of the epidermis, in hair follicles, the basement membrane at the dermo-epidermal junction (occasionally extending into the basement membrane of dermal blood vessels), wounded skin and several invasive squamous cell carcinomas (at protein level). Expressed in normal and wounded skin and various squamous cell carcinomas. Up-regulated in epithelial cells after skin injury. Keratinocyte mitogens. Expression is significantly up-regulated in carcinogen-induced skin tumors, various squamous cell carcinomas, some colon cancer cell lines and tumors. Belongs to the fibroblast growth factor-binding protein family.