[Molecular heterogeneity of alpha-fetoprotein in ovarian or extragonadal yolk sac tumor].

The molecular heterogeneity of alpha-fetoprotein (AFP) in yolk sac tumor (YST) was investigated. The study included 14 sera from YST, 78 sera from primary hepatocellular carcinoma (PHC), 5 fetal yolk sac (YS) culture fluids and 4 fetal liver culture fluids. The microheterogeneity of AFP was assessed by differences in reaction with AFP carbohydrate chain and lectins, and concanavalin A (Con A), Lens culinaris hemagglutinin (LCH) and phytohemagglutinin E (PHA-E) affinity crossed-line immunoelectrophoresis was used to fractionate AFP. It was found that AFP in YST or YS had similar subfraction patterns and differed clearly from AFP in PHC or fetal liver. Characteristic features of AFP subfraction in YST or YS were the presence of a LCH weakly-reactive subfraction and a high proportion of both Con A non-reactive and PHA-E strongly-reactive subfractions. The LCH weakly-reactive subfraction was specifically found in YST or YS, but was not found at all in PHC or in fetal liver. This variant is known to exist in amniotic fluid at an early stage of gestation, and is assumed to have a carbohydrate chain with both fucose and bisecting N-acetyl-glucosamine. The present findings therefore suggest that glycosylation of AFP in YST takes place by retro-genetic differentiation toward fetal yolk sac, but not toward fetal liver, and these studies confirm the suggested yolk sac origin of ovarian, as well as extragonadal, yolk sac tumor.