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Development- and tissue-specific alpha-fetoprotein (AFP) gene expression is controlled by various transcription factors including hepatocyte nuclear factors (HNFs), and a number of cis-acting elements. We recently identified multiple CCAAT/enhancer binding protein (C/EBP) binding sites in the enhancer of the human AFP gene. In this study, we have identified and functionally characterized seven C/EBPalpha-binding sites in the promoter and enhancer regions. An electrophoretic mobility shift assay (EMSA) and DNase I footprinting analysis identified two and five C/EBPalpha-binding sites located in the promoter and enhancer regions, respectively. Chromatin immunoprecipitation analyses showed that C/EBPalpha binds both enhancer and promoter regions of the AFP gene in human AFP-producing hepatoma and stomach cancer cells, but not in non-AFP-producing cells. Reporter transfection assays showed that transcription was stimulated by C/EBPalpha binding to each of the elements. These results indicate that C/EBPalpha regulates AFP gene expression through direct binding to multiple sites in the human AFP gene in cultured human cells.

Objective: Alpha-fetoprotein (AFP) is a major fetal serum protein, the biologic role of which has not been not fully elucidated. Recently, existence of a novel AFP mRNA isoform (del.1 AFP mRNA isoform), which is transcribed from the intron A (the intron between exons 1 and 2), has been reported in murine yolk sac and fetal liver. In the present study, we intended to identify the human homologue of the murine AFP mRNA isoform in the yolk sac tumor., Methods: To investigate the existence of the mRNA isoform (which we termed the "AFP-C mRNA isoform"), reverse transcription-polymerase chain reaction (RT-PCR) was used. Moreover, the expression analysis of the AFP-C cDNA isoform using the AFP-negative human cell line was carried out., Results: RT-PCR revealed the existence of the AFP-C mRNA isoform in the yolk sac tumor and human hepatocellular carcinoma cells. The expression analysis clarified that the molecular size of the AFP-C was approximately 65 kd, and that the protein was not secreted, in contrast to the traditional AFP., Conclusion: From these results, the existence of the AFP-C mRNA isoform has been demonstrated for the first time in humans. The AFP-C located in cytoplasm possibly plays physiologic/pathogenic roles distinct from those of the traditional AFP in the yolk sac tumor and hepatocellular carcinoma.

Serum alpha-fetoprotein (AFP) levels in hepatocellular carcinoma (HCC) patients and expression of the protein in cultured HCC cell lines are highly variable. These observations may arise from features correlated with tissue-specific expression of the gene. Extremely strong and potent liver-specific enhancer activity is confined from -4.1 to -3.3 kb upstream to the human AFP gene in contrast with that of the rodent which exists in three widely separated regions. To understand the tissue-specific expression of AFP, we examined cis-acting elements in the enhancer. Results revealed binding sites for selected liver-enriched transcription factors (LETFs) in both domains A (-4120 to -3756 bp) and B (-3492 to -3300 bp) of the gene. These sites included: one hepatocyte nuclear factor (HNF)-1 and HNF-4, two HNF-3, and two C/EBP binding sites in domain A. An adjacent domain B contained one HNF-3 site and three C/EBP sites plus a previously identified HNF-1 site. Each of these elements alone has the ability to stimulate heterogeneous promoter activity in a dose-dependent manner when transfected into AFP producing cells. A comparative study showed that the presence of two HNF-1 and one HNF-4 site is a characteristic feature of human but not rodent AFP enhancer. The mRNA levels of the liver-enriched transcription factors (LETFs) were variable in individual HCC cell lines and together with silencer activities may underlie differential expression of the AFP gene.

Glucocorticoids inhibit rodent alpha-fetoprotein (AFP) gene activity but stimulate expression of the human homologue. Like human, activity of the AFP promoter from other primates was stimulated by the synthetic glucocorticoid dexamethasone (Dex) in various cell lines. A glucocorticoid responsive element (GRE) is located within 180 bp upstream of the transcription initiation site of all AFP genes examined. Comparative analysis of the GRE in the two different groups of promoters revealed a common 3' hexamer, 5'-TGTCCT-3', but the 5' hexamers were different. This difference converts the rodent GRE to a DR-1 motif. DR-1 is a binding site for members of the nuclear receptor superfamily including the orphan receptor hepatocyte nuclear factor-4 (HNF-4). The presence of DR-1 in the rodent but not human may underlie the opposite actions of Dex on the AFP promoter. We tested this hypothesis using a transient transfection assay. In hepatoma cells that expressed GR and HNF-4, reporter-activity was inhibited by Dex. The same construct in nonhepatoma cells was strongly induced by over expression of HNF-4 and the induced activity was inhibited by Dex. The findings show that Dex induction of human AFP is mediated by a GRE. But Dex repression of the rodent promoter requires a DR-1 motif that interacts with GR and HNF-4., (Copyright 2001 Academic Press.)

Thirty-six monoclonal antibodies (MAbs) against human alpha-fetoprotein (AFP) were analyzed for the location of their epitopes by reacting them with a set of yeast recombinant AFP proteins using ELISA. Recombinant AFP proteins containing either one, two or all three domains, i.e. domain I, domain III, domain I-II, domain II-III and domain I-II-III, were produced and secreted into the culture medium of yeast cells harboring the expression plasmids. Epitopes of 13 MAbs were localized on domain I and 17 others were on domain III. However, the exact location of the epitopes of the remaining 6 MAbs could not be defined. The epitope of an antibody, namely AFY6, which was located in domain I, was successfully mapped on an octapeptide, C175KAENAVE182, using synthesized overlapping octapeptides., (Copyright 2001 S. Karger AG, Basel)

The carbohydrate structure of glycoproteins is considered to be tissue-specific or cell type-specific, but there have been no reports on the differences of the carbohydrate structure of alpha-fetoproteins (AFPs) produced by histologically identical tumors in different tissues. The lectin affinity electrophoresis of hepatoid adenocarcinomas and yolk sac tumors from different organs suggested that either the tumor heterogeneity or the tissue specificity is possibly involved, the lectin reactivity of the AFP sugar chain structure produced by the tumors in different tissues.

Experimental autoimmune thyroiditis was induced in transgenic mice (TG-3) producing human alpha-fetoprotein (AFP) and in control mice by immunization of porcine thyroid peroxidase (TPO). Development of thyroiditis accompanied with mononuclear cell infiltration was observed in 6 out of 8 treated control mice. In contrast, the development was significantly suppressed in TG-3 mice and mild histologic change was observed in only 1 out of 8 TG-3 mice (p < 0. 05). Serum anti-TPO antibody titers gradually increased in TG-3 mice as well as in control mice and there were no significant differences. In vitro phytohemagglutinin response of splenocytes from TG-3 mice was lower than that from control mice. Significantly reduced numbers of CD4+ and CD8+ splenocytes, total thymocytes, and CD4+ thymocytes were found in the nontreated TG-3 mice as compared with those in control mice. These results suggest that ubiquitously produced AFP modulates in vivo T cell development and/or T cell-dependent immune responses.

Aims: To investigate a potential diagnostic use of alpha fetoprotein (alpha FP) isoform analysis by lectin affinity electrophoresis to distinguish between endodermal sinus tumours arising in the vagina in infants from those at other sites., Methods: alpha FP in the serum of a patient with a vaginal endodermal sinus tumour was analysed for its isoforms by lectin affinity electrophoresis. The isoforms were compared with that of cord serum, sera of hepatoid adenocarcinoma of the uterus, and endodermal sinus tumour of the ovary., Results: The isoforms of alpha FP obtained by lectin affinity electrophoresis in the serum of the patient with vaginal endodermal sinus tumour differed from the isoforms of alpha FP in the cord serum of normal neonates, and sera of patients with hepatoid adenocarcinoma of the uterus or endodermal sinus tumour of the ovary., Conclusions: Endodermal sinus tumour arising in the vagina could be distinguished from that in the ovary by the lectin affinity electrophoresis, and a potential diagnostic use of alpha FP isoform analysis by the lectin affinity electrophoresis for the detection of the endodermal sinus tumour in infants was demonstrated.

The expression of the ATBF1 gene in developing brain was analyzed in mice from 13 days of gestation to 28 days after birth using RNase protection and in situ hybridization methods. The level of ATBF1 transcripts was the highest on embryonic day 13-15 and then progressively decreased to a hardly detectable level on postnatal day 28. Throughout the period examined, ATBF1 mRNA was expressed consistently in the basal telencephalon, diencephalon, and mesencephalon, with the highest levels in the inferior colliculus and thalamus. On the other hand, no significant expression was observed in cerebellum, neocortex, hippocampus, and olfactory bulb. These results illustrate significant regional differences in the ATBF1 expression and suggest a role of the ATBF1 gene in the formation of some specific cell populations in developing central nervous system.

Transgenic mouse which produces human alpha-fetoprotein (AFP) ubiquitously was used to study carbohydrate structures of AFP produced by various tissues as well as that in the serum. A series of tissues from the transgenic mouse were cultured in vitro and the AFP produced was analyzed by affinity electrophoreses with 4 kinds of lectins. Variable electrophoretic profiles of them suggested that the fine structures of the carbohydrate of human AFPs expressed in the mouse tissues were different. The characterization of human AFP produced by mouse hepatoma which developed in offspring between the AFP transgenic mouse and hepatoma-developing transgenic mouse indicated that the hepatoma AFP was distinct from the liver AFP and that the malignancy-specific phenotypic alteration was common to human and mouse.

A high serum alpha-fetoprotein (AFP) level was found in a patient with endometrial adenocarcinoma of the uterus, which appeared to be hepatoid on histological examination. The AFP of this unusual patient was purified by immunoaffinity chromatography and characterized. The electrophoretic profiles on sodium dodecyl sulfate-polyacrylamide get electrophoresis both before and after glycopeptidase F treatment were indistinguishable from those of a hepatoma AFP. This indicates that the patient's AFP was also composed of a single polypeptide chain of Mr 67,000 and an N-linked sugar chain of Mr 3,000. Amino acid sequence analyses of this AFP, and of AFP from hepatoma and umbilical cord serum indicated that the N-terminal sequences were essentially the same. The sequence, Arg-Thr-Leu-His-Arg-Asn-Glu-Tyr-Gly-Ile, was slightly different from previous reports, but matched that deduced from the cDNA sequence. AFP isoforms due to microheterogeneity of the sugar chain were analyzed by lectin affinity electrophoresis using a series of lectins. The AFP isoform profiles were distinct from those of proteins derived from cord serum, hepatoma, yolk sac tumor and gastric cancer. The reverse-transcription of RNA from the tumor tissue followed by a polymerase chain reaction using primers with AFP-specific sequences gave a product of the size and nucleotide sequence expected for AFP. mRNAs possessing the requisite sequences for albumin and transferrin syntheses were also detected in the tumor. The expression of these hepatocyte-specific proteins supported the hepatoid nature of this tumor.

Experimental arthritis was induced in the knee joint of transgenic mice expressing human alpha-fetoprotein by immunization with methylated bovine serum albumin in Freund's complete adjuvant. In the control experiment with normal C57BL/6 mice, definite arthritis was observed in 55.6% (5/9) of the mice, but in only 21.1% (4/19) of the transgenic mice. This result suggested that human alpha-fetoprotein functioned as an immunosuppressant to ameliorate the development of the immune disease.

Rat alpha-fetoprotein (RAFP) shows two discrete electrophoretic variants, slow and fast, with molecular weights of 72,500 and 69,500, respectively. To elucidate the structural basis of this heterogeneity, we developed the expression system of RAFP cDNA and its mutants with the use of cultured mouse fibroblasts and a retrovirus vector. This produced recombinant wild-type and three mutant proteins and has several advantages over the use of Escherichia coli or Saccharomyces cerevisiae. The mutants were designed to lack either one or both of the two possible glycosylation sites on RAFP. Electrophoretic analyses relating to the glycosylation states of the recombinant proteins as well as of natural RAFP produced by rat cells before and after digestion with glycopeptidase F indicated that the slow variant has carbohydrate units located at Asn-93 and Asn-229 and the fast one has one at Asn-229.

alpha-Fetoprotein (AFP) binds a series of endogenous fatty acids. To identify the fatty acid binding site, this protein, purified from umbilical cord blood by immunoaffinity chromatography, was covalently labeled using 12-(9-anthroyloxy) stearic acid conjugated with Woodward's reagent K. After digestion with lysyl endopeptidase, the fatty acid-labeled peptide was isolated. Amino acid sequence analysis showed that this peptide consisted of the amino acid residue 210-227. The fact that no appreciable PTH-amino acid was detected at 14th cycle on the degradation suggested that Lys223 was modified with the fatty acid. The finding that lysyl endopeptidase did not cleave off at the Lys223 supported this suggestion. These results indicate that the carboxyl group of the bound fatty acid is located close to Lys223 in human AFP.

Erythroagglutinating phytohemagglutinin (E-PHA)-reactive alpha-fetoprotein (AFP)-P4 and E-PHA weakly-reactive AFP-P3 of sera from cord blood at term and from patients with hepatocellular carcinomas showed a mobility of monosialo-AFP in two-dimensional extended agarose gel-E-PHA affinity electrophoresis. Asialo-AFP had as high an affinity for E-PHA as that of monosialo-AFP-P4, while disialo-AFP, AFP-P2, revealed a negligible affinity for E-PHA. For Allomyrina dichotoma lectin (allo A), asialo-AFP had no affinity with a mobility of AFP-A1s, monosialo-AFP-P4 had the highest affinity with a mobility of AFP-A3, and monosialo-AFP-P3 had an intermediate affinity with a mobility of AFP-A2s. The affinity of AFP-P4 for E-PHA was reduced by galactosidase digestion, indicating the presence of galactose residues, one sialylated and the other exposed.(ABSTRACT TRUNCATED AT 250 WORDS)

Human serum alpha-fetoprotein (AFP) is elevated in not only hepatocellular carcinoma (HCC) but also benign liver diseases. AFP produced in HCC and benign liver diseases was separated into several isoforms corresponding to different sugar chain structures by several types of lectin affinity electrophoresis, and the HCC-specific AFP isoform was discriminated from those of benign liver diseases. Because a small amount of HCC-specific AFP isoform was detected in cord serum AFP, the whole sugar chain structures of human cord serum AFP were determined, as follows: Neu5Ac alpha 2-->Gal beta 1-->4GlcNAc beta 1-->2Man alpha 1-->6(Neu5Ac alpha 2 -->6Gal beta 1-->4GlcNAc beta 1-->2Man alpha 1-->3)Man beta 1-->4R1 and R2, Gal beta 1-->4GlcNAc beta 1-->2Man alpha 1-->6(Neu5Ac alpha 2-->6Gal beta 1 -->4GlcNAc beta 1-->2Man alpha 1-->3)Man beta 1-->4R1 and R2, and Neu5Ac alpha 2-->3Gal beta 1-->4GlcNAc beta 1-->2Man alpha 1-->6(Neu5Ac alpha 2 -->6Gal beta 1-->4GlcNAc beta 1-->2Man alpha 1-->3)Man beta 1-->4R1 and R2 in the ratio of 81.6:8.9:9.5. R1 and R2 denote GlcNAc beta 1-->4GlcNAcOT (subscript OT represents an NaB3H4-reduced oligosaccharide) and GlcNAc beta 1-->4(Fuc alpha 1-->6)GlcNAcOT, respectively, and the ratio between R1 and R2 in the respective fractions was approximately 19:1. In contrast, the sugar chain structure of HCC highly specific AFP isoform was found to comprise a monosialyl-biantennary sugar chain with additional fucosylation of the proximal N-acetylglucosamine. Fucosylation of AFP produced in fetal liver increased in inverse proportion to the gestation period, in weeks, indicating that fucosylation of AFP in HCC may be related to the dedifferentiation of human hepatocytes through malignant transformation.

Transgenic mice were produced by the microinjection of the cDNA of human alpha-fetoprotein (AFP) under control of the enhancer/promoter of the human beta-actin gene. Among the 4 mouse lines where the transgene were stable transmitted to the progeny, 3 produced human AFP. The expression was not developmental stage-specific nor tissue-specific as predicted from the properties of enhancer/promoter. The serum human AFP levels of adult mice were 30-600-fold higher than those of mouse AFP. These mice could be useful for the studies of possible biological functions of AFP during development as well as in malignancies.

Rat alpha-fetoprotein (AFP) has been demonstrated to bind estrogen, whereas human AFP lacks the activity. We constructed four chimeric molecules from cDNAs encoding these AFPs with the use of two restriction sites common to them and expressed them as well as rat and human AFP cDNA in yeast. The recombinant molecules were purified, characterized, and found to have the predicted structures. Analyses of estrogen binding indicated that a rat AFP sequence composed of residues 423-506 that contains 31 rat-specific amino acids is essential for the activity.

The molecular basis for electrophoretic variations of rat alpha-fetoprotein was studied. Stepwise deglycosylations of proteins and radiolabeling of the sugars indicated that the number of such chains per molecule is two and one for the slow and fast variants, respectively.

Human alpha-fetoprotein (AFP) was expressed in Saccharomyces cerevisiae, with a plasmid containing the cDNA sequence for human AFP fused with the rat AFP signal peptide. The recombinant AFP was purified from the yeast lysate by DEAE-cellulose and immunoaffinity chromatography. The amino acid composition and the molecular weight of the recombinant AFP were similar to those of hepatoma AFP. N-terminal amino acids sequence analysis indicated that the signal peptide had been processed. The recombinant and hepatoma AFP reacted identically in Ouchterlony immunodiffusion and radioimmunoassay tests. These observations indicated that the yeast recombinant protein had the properties of native AFP.

The slices of testicular tumors isolated from patients with high serum alpha-fetoprotein (AFP) levels were cultivated in vitro, and the synthesis of some serum proteins, including AFP, was demonstrated. The tumors were produced from yolk sac in rats by fetectomy. The tumors consisted of the various histological structures, such as of teratoma, yolk sac tumor, and very immature tumor. The tumors with yolk sac histology were able to produce AFP. The tumors induced in rats were transplantable, but the well-differentiated histology disappeared after transplantation. The capacity of AFP synthesis in transplanted tumors seemed to be maintained for generations in female rats but not in male rats.

This study reports the use of radiolabeled antibody to AFP and CEA for the detection and localization of AFP- or CEA-producing tumors. Thirty-one patients received 131I-labeled anti-AFP or anti-CEA antibodies. Photoscans were taken at 24 and 48 hours after injection of radioantibodies. In three of six patients with CEA-producing tumors, radioimmunodetection with anti-CEA antibody showed positive scans. In AFP-producing tumors, 7 of 15 patients had positive findings on immunoscintigraphy using polyclonal anti-AFP antibody, and two of nine patients had positive findings when monoclonal antibodies were used. Analysis of radioantibody in the blood after injection showed both complex and free antibody with immunoreactivity in the circulation, and smaller complexes were seen to form after administration of monoclonal antibodies.

Twenty-two hybridoma clones which produced monoclonal antibodies to AFP were established by the fusion of myeloma cells and spleen cells of mice immunized with AFP. Antibodies secreted in the ascites of mice in which the tumor was transplanted intraperitoneally were used in the radioimmunoassay of AFP by the sandwich method; these antibodies were also used in the immunoaffinity purification of AFP. The results indicated that some antibodies had several advantages over the conventional polyclonal antibodies from antiserum in these procedures.

Serum levels of alpha-fetoprotein were determined in 33 patients with testicular germ cell tumors and were normal in 11 patients with seminoma and in one patient with matured teratoma; high levels were observed in 19 of 21 patients with embryonal carcinoma, teratocarcinoma, or a mixed type of these germ cell tumors. Tissues from the testicular germ cell tumors were cultivated with 14C-labeled leucine. After incubation, the culture media were subjected to immunoelectrophoretic and autoradiographic analyses. The results were: (i) Radioactive alpha-fetoprotein, albumin, transferrin, and alpha1-globulin appeared in the culture media of embryonal carcinomas obtained from two infants. (ii) Radioactive albumin and alpha1-globulin appeared in the culture media of a mixed type tumor metastasized from testis to retroperitoneal region. (iii) No such radioactive proteins appeared in the culture media of primary seminomas.

Alpha-Fetoproteins of several animals were purified and their molecular weights, amino acid compositions and peptide maps were compared, demonstrating the close similarities. These data indicated that the alpha-fetoproteins of mammalian species have closely related antigenical and chemical structures. Rabbits and horses were immunized with human alpha-fetoprotein, and it was observed that the animals produced antibodies reaction not only with human alpha-fetoprotein but with their homologous alpha-fetoproteins. The results were interpreted as the breakdown of the tolerance to their own alpha-fetoprotein.

The carbohydrate moiety of alpha-fetoprotein purified from human yolk sac tumors grown in nude mice was quantitatively released from the polypeptide chain as oligosaccharides by hydrazinolysis. The oligosaccharides were separated into a neutral and two acidic oligosaccharides by paper electrophoresis. By sequential exoglycosidase digestion in combination with per-O-methylation study and periodate oxidation, their structures were determined to be: Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(GlcNAc beta 1 leads to 4) (Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4(Fuc alpha 1 leads to 6)GlcNAcOT, Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(GlcNAc beta 1 leads to 4) (Sia alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4(Fuc alpha 1 leads to 6)GlcNAcOT; and Sia alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(GlcNAc beta 1 leads to 4) (Sia alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4 GlcNAc beta 1 leads to 4(Fuc alpha 1 leads to 6)GlcNAcOT, in which Gal is galactose, GlcNac is N-acetylglucosamine, Man is mannose, Fuc is fucose, Sia is sialic acid, and Subscript OT is the NaB3H4-reduced oligosaccharide.

Human of rat alpha-foetoprotein (AFP) was highly purified from ascitic fluid or serum of hepatoma bearers. The purification was carried out mainly by means of immunoadsorbent chromatography using Sepharose coupled to specific anti-AFP antibody with BrCN activation, and by Sephadex gel filtration. Horses were immunized with the purified AFP and the specific antibody was isolated from the antiserum by means of an immunoadsorbent coupled to purified AFP. The specific antibody was found to bind specifically with AFP-producing tumour cells. The antibody was applied for radio immunodetection of the tumour. 125I-labelled antibody was administered to patients or rats with hepatoma, and radioactivity localized in the tumours was scintiscanned with a scintillation camera. In this way, the location of the tumour was detected in about 50% of the hepatoma bearers. The cytotoxicity of the antibody was clearly demonstrated both in vitro and in vivo in animal experiments. The antibody was administered to patients with advanced hepatoma. Although no improvement of the disease was demonstrated, serum AFP levels decreased greatly and in some cases low AFP levels were maintained for long periods suggesting that the antibody suppressed AFP-producing hepatoma cells. No significant side effects were observed in patients who had been administered with the horse antibody.

Twenty-two hybridoma clones which produced monoclonal antibodies to human alpha-fetoprotein (AFP) were established by the fusion of myeloma cells and spleen cells of mice immunized with AFP. Hybridomas were transplanted i.p. and antibodies were purified from the ascites of tumor-bearing mice. Antibodies were used for the purification of AFP by immuno-affinity chromatography and increased amounts of AFP were isolated in higher yields. Antibodies were used in the AFP radioimmunoassays and successful result was obtained when used in the sandwich technique. Antibodies were also tested in the radioimmunodetection of AFP-producing tumors and positive images of tumors were obtained in several cases.

We have attempted to determine the carbohydrate moiety of human alphafetoprotein (AFP) produced by a yolk sac tumor. AFP was obtained from the cystic fluid of human yolk sac tumors grown in nude mice and was purified using an immunoadsorbent column coupled with monoclonal anti-AFP antibody. Then, the carbohydrate chain of the purified AFP was quantitatively released from the polypeptide chain. The resulting oligosaccharide was labeled and, by sequential exoglycosidase digestion in combination with methylation analysis and periodate oxidation, the structure was determined to be: Sia alpha 2----6Gal beta 1----4GlcNAc beta 1----2Man alpha 1----6 (GlcNAc beta 1----4) (Sia alpha 2----6Gal beta 1----4GlcNAc beta 1----2Man alpha 1----3) Man beta 1----4GlcNAc beta 1----4 (Fuc alpha 1----6) GlcNAcOT Compared with the known structure of the sugar, chain of human hepatic AFP, it was found that the sugar chain of yolk sac AFP contained an additional sugar, N-acetylglucosamine (bisect GlcNAc) linked to the beta-mannose. In the light of recent knowledge, this result indicates that the Concanavalin A (Con-A) binding site of the sugar chain is blocked by this GlcNAc in human yolk sac AFP. This fact forms the basis for the clinical use of the Con-A binding test to determine the origin of AFP in patients.

Murine alpha-fetoprotein was synthesized in a wheat germ cell-free system in the presence of radioactive amino acids under the direction of alpha-fetoprotein messenger RNA isolated from mouse yolk sacs. The radiolabeled alpha-fetoprotein was isolated by immunoabsorption, and the amino acid residues at the NH2 terminus were determined by radioactive sequencing techniques. In a comparison to the NH2-terminal sequence of circulating alpha-fetoprotein, the in vitro-synthesized alpha-fetoprotein was found to contain an extra peptide 20 amino acids long linked at the NH2 terminus, the sequence of which is: (formula: see text). The molecular size, the hydrophobic nature, and the other properties of the peptide are consistent with the "leader" or "signal" piece found in the precursors of many other secretory proteins. This suggests that alpha-fetoprotein, the synthesis of which is limited primarily to fetal development, is produced in the form of the precursor as are secretory proteins in the adult tissues.

Studies were undertaken to evaluate whether the intraperitoneal administration of horse antibody to rat alpha-fetoprotein (HabRatAFP) would inhibit or prevent the growth of AH-66 tumor cells inoculated into Donryu male rats. In animals inoculated with tumor subcutaneously there was 100% tumor growth in uninjected control animals and the administration of HabRatAFP prevented tumor growth in 7/24 (29%) of the animals. When animals were inoculated with tumor intraperitoneally, the inhibition of tumor growth by HabRatAFP only occurred at tumor-cell doses of 50,000, 10,000, and 5,000. In these three groups, 15/35 (43%) of those animals treated with HabRatAFP did not develop tumor whereas 1/36 (3%) of the normal horse-serum treated animals did not develop tumor. The majority of those animals which were cured of their tumors by HabRatAFP treatment resisted tumor rechallenge. Studies were done to elucidate the mechanisms responsible for the anti-tumor effect of HabRatAFP, AH-66 tumor cells which were placed into millipore chambers, implanted intraperitoneally, were killed by the intraperitoneal administration of HabRatAFP. Studies were conducted to see if treatment with HabRatAFP to rat AFP might increase the immunogenicity of an inoculum of X-irradiated tumor cells. In one experiment, no animals which received only X-irradiated tumor cells resisted tumor rechallenge with 5 X 10(6) tumor cells whereas 6/11 (54.5%) of those animals which received X-irradiated tumor cells and treatment with HabRatAFP resisted tumor rechallenge.

Rat alpha-fetoprotein (AFP) cDNA spanning the complete coding region was cloned and expressed in Escherichia coli as well as in yeast, Saccharomyces cerevisiae. The recombinant AFPs (rAFPs) were purified and characterized. The molecular weights determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis were 65,000 for E. coli rAFP and 69,000 for yeast rAFP. Amino acid and N-terminal sequence analyses indicated 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. 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. These observations indicated that the rAFP expressed in yeast emulated the properties of authentic AFP.

Production of rat alpha-fetoprotein by transplantable ascites hepatoma was studied by radioimmunoassay method. alpha-Fetoprotein was detected in sera from rats bearing 22 out of 50 ascites hepatoma cell lines that were previously negative for the presence of alpha-fetoprotein by the Ouchterlony test. alpha-Fetoprotein was also detected with high prevalency in Morris hepatomas and sublines of Yoshida sarcoma by this assay system.