EXPRESSION OF SERUM-ALBUMIN AND OF ALPHA-FETOPROTEIN IN MURINE NORMALAND NEOPLASTIC PRIMITIVE EMBRYONIC STRUCTURES

Alphafetoprotein (AFP), a major serum protein synthesized during the e mbryo-fetal and postnatal period (in the yolk sac, then in the liver), is also an oncoprotein. The intracellular presence of AFP and of seru m albumin (SA) in normal and neoplastic neural crest and neural tube d erivatives was previously demonstrated. In this work we have studied t he comparative expression of AFP and SA in primitive neuroectoblastic structures of mouse embryos (6 and 7 days ''post coitum'') and mouse t eratocarcinomas (derived from the PCC4 cell line). Using immunofluores cence technique, antibodies to SA gave a positive reaction in embryos of 7 days, while AFP was not detected during this period. By mRNA in s itu hybridization, SA mRNA gave a strong signal in both 6 and 7 day em bryos, whereas AFP mRNA gave a weak signal only in 7-day embryos. The distribution of SA and AFP and their mRNAs was investigated in primiti ve neuroectoblastic structures of the teratocarcinomas by in situ hybr idization and immunostaining. Only SA protein was detectable by immuno staining. SA mRNA gave a strong signal in differentiating structures a s well as in undifferentiated cell clusters. AFP mRNA was observed onl y in differentiating structures. Dot-blot hybridization indicated that the level of SA transcripts was at least 6-fold higher than that of A FP transcripts in the teratocarcinomas investigated. In teratocarcinom a-bearing mice injected intraperitoneally with I-125-radiolabeled SA a nd AFP, significant accumulations of both SA and AFP were demonstrated in the tumors, SA being about 3-fold higher than that of AFP after no rmalization to quantity of uptake in liver. External in vivo photoscan ning confirmed this relationship of accumulated radiolabeled proteins. The last observation could be useful in vivo for diagnosis of teratoc arcinoma. We conclude that the expression of SA relative to AFP and th e external cellular uptake of SA relative to AFP are similar in normal embryonic developing tissues and in the corresponding morphologically neoplastic tissues of the teratocarcinomas. The same SA:AFP relations hip constitutes an oncofetal marker of primitive neuroectoblastic stru ctures. (C) 1995 Wiley-Liss, Inc.