HGF and neoplasm: For example, the HGF secreted by CAFs acts on tumor cells stimulating them not only to proliferate, invade and metastasize but also to produce a variety of HGF-inducers, such as bFGF, IL-1β, TGF-α, PDGF and prostaglandin E2 (PGE2), that act on stromal fibroblasts.