AFPを見直そう

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Rat alpha-fetoprotein(AFP)cDNA spanning the complete coding region was cloned and expressed in Escherichia coli as well as in yeast, in 1988. The recombinant AFPs(rAFPs)were purified and characterized. The yeast rAFP was found to be indistinguishable from authentic AFP in the Ouchterlony immunodiffusion test, radioimmunoassay and estradiol-binding assay while E.coli rAFP was less reactive in these tests. The explanation for the difference in the properties of AFPs might be that yeast cells produced mature AFP by processing the signal peptide properly but E. coli rAFP lacked the N-terminal 53 amino acid residues of preAFP, and/or the characteristics of the transformed cell regarding the carbohydrate chain synthesis were reflected. In the past, human serum AFP is considered to be only one of the most reliable tumor marker of the yolk sac tumor and hepatocellular carcinoma in a Gynecologic field, which can be used to monitor the effectiveness of therapy and to detect recurrences. It is well known that the carbohydrate chain synthesis inside a cell gets catalyzed by a set of glycosyltransferase, and those enzymes are considered to be cell typespecific. We have focused on the heterogeneity in carbohydrate chain of AFP, and demonstrated that a AFP producing tumor having similar histologic characteristics and originating from different organs or tissues could be distinguished in carbohydrate chain heterogeneity of AFP. Furthermore, in an Obstetric field, we have determined the percentage of AFP variants that react with lectins as a way to find out whether the analysis of the carbohydrate chain microheterogeneities of maternal serum or amniotic fluid AFP could be useful for prenatal screening of fetal chromosomal abnormalities. With receiver operating characteristics(ROC) analyses using 22 trisomy 21-affected pregnancies and 227 unaffected pregnancies, the percentage of AFP L3 in maternal serum was revealed to exist a greater area under the curve than those of MoM AFP and MoM uE3, and it was revealed to have a tendency of larger area than that of MoM hCG. Therefore, this potentially valuable marker with the use of an automatic analyzer for measuring AFP L3 was tested. It is revealed that the analysis of the carbohydrate chain microheterogeneities of maternal serum AFP by an automatic analyzer is extremely useful for prenatal trisomy 21 screening.
2001-09-01

AFPを見直そう

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