Alpha-Fetoprotein

Alpha-fetoprotein (AFP) is a major protein in the serum and amniotic fluid of developing mammalian fetuses, but is normally absent in the serum of adult mammals. The AFP gene, a member of the serum albumin gene family, is present in mammals but does not appear to be present in other vertebrates. The AFP gene is expressed abundantly in the yolk sac and fetal liver, and then becomes silenced at birth. This gene is normally silent in the adult liver, but it can be reactivated in the regenerating liver and liver cancer as well as other types of tumors. In addition, elevated maternal serum AFP levels in pregnant women have been found to be associated with neural tube defects in the developing fetus. Based on these observations, AFP has become an important diagnostic biomarker. These clinically relevant features of AFP expression have led to considerable interest in the regulation and function of AFP since its discovery over 50 years ago.