The physiology of alpha-fetoprotein

Despite 40 years of research investigation the biologic role of alpha-fetop rotein (AFP) is still largely unknown. As an oncofetal antigen it is believ ed to serve an important role in carcinogenesis and normal development. Sin ce the mid-1960's this tumor-associated fetal protein has been clinically u seful as a birth defect screening agent and tumor marker. Despite extensive description of the synthetic, structural, and physiochemical properties of this 70-kDa glycoprotein, the functional capacity of this oncofetal protei n has only been described by in vitro studies to date. Attention has largel y focused on ligand carrier/transport functions, immunoregulation, growth r egulatory properties, and transcriptional enhancement and/or suppression. T he latter includes regeneration, differentiation, transformation and regene ration in oncogenic and ontogenetic growth processes. Therefore, AFPs origi nal conceptual role only as a fetal substitute for albumin is no longer ten able.