Hiroko Taga

Establishment of assay kits for the determination of microheterogeneities of alpha-fetoprotein using lectin-affinity electrophoresis

Diagnostic kits for determination of alpha-fetoprotein (AFP) carbohydrate chain microheterogeneity were developed using lectin affinity electrophoresis with Lens culinaris agglutinin-A (LCA-A) and erythro-agglutinating phytohemagglutinin-E4 (PHA-E4). Separated AFP bands by electrophoresis were detected with high sensitivity by antibody-affinity blotting and immunoenzymatic amplification. Densitometry was used to apportion lectin reactive AFPs. The within-run S.D. for proportions of AFP bands was below 3%. Band intensity was linearly related to AFP concentration between 2 and 200 ng/ml. Profiles of lectin reactive AFPs were compared in serum samples from 55 patients having liver diseases. The average values of lectin reactive AFPs for chronic hepatitis and liver cirrhosis patients were both below 13%, but those of hepatocellular carcinoma patients were above 25%. Correlation of data with disease states suggests that the methods can greatly facilitate the discrimination between benign and malignant liver diseases.

Early Diagnosis of Hepatocellular Carcinoma with Lectin Electrophoresis of Serum Alpha-Fetoprotein

A sensitive procedure involving lectin affinity electrophoresis of alpha-fetoprotein (AFP) was established. AFPs electrophoresed on lectin-containing gels were blotted on nitrocellulose membrane which was precoated with the specific antibody to AFP and stained with peroxidase-labeled anti-AFP antibody. This method could detect as little as 4 micrograms/l of purified AFP dissolved in buffer, or 50 micrograms/l in serum specimens. A number of patients with liver disease have been followed for long periods in Nihon University Hospital, Tokyo. Serum specimens were collected serially and stored frozen. We have reinvestigated retrospectively 6 series of serum specimens by the lectin-immunoblotting technique and found 3 cases that revealed a hepatocellular carcinoma-specific AFP variant at a very early stage, in advance of any other evidence of hepatocellular carcinoma by clinical examination.

Datura stramonium Agglutinin-Reactive α-Fetoprotein Isoforms in Hepatocellular Carcinoma and Other Tumors

By means of Datura stramonium agglutinin (DSA) affinity electrophoresis, human alpha-fetoprotein (AFP) was resolved into five bands, AFP-D1, D2, D3, D4 and D5, in order of decreasing mobility. AFP-D1, which had no affinity for DSA, comprised more than 84% of the intensity of total AFP bands. The percentage of AFP-D2 increased marginally in hepatitis and liver cirrhosis with or without hepatocellular carcinoma. AFP-D3 increased characteristically in hepatocellular carcinoma and AFP-D4, which had the highest affinity for DSA, increased up to 12% in other tumors, mostly of gastrointestinal origin. AFP-D5 showed no consistent changes among the benign and malignant diseases. The assay of AFP-D3 and D4 proved useful as a highly specific marker of hepatocellular carcinoma and other tumors, respectively.

Affinity and kinetic studies for the evaluation of lectin-reactive α-fetoprotein with a biosensor based on surface plasmon resonance

Abstract Affinity and kinetic analyses for the evaluation of lectin-reactive α -fetoprotein (AFP) were performed using a biosensor based on surface plasmon resonance (SPR). Human AFP, purified from HCC (hepatocellular carcinoma) patients, was immobilized on the surface of a sensor chip. The interaction of this bound AFP with three lectins, Lens culinaris agglutinin [LCA], concanavalin A [Con-A] and erythroagglutinating phytohemagglutinin [E-PHA]) were monitored in real-time with the change in the SPR response. These three lectins produced an increase in the SPR response, indicating that all three bound specifically to the immobilized AFP. The association ( k ass ) and the dissociation ( k diss ) rate constants clearly differed among the three lectin-AFP interactions. These affinity and kinetic analyses of the sugar binding specificities of lectins, employing a biosensor based on SPR, are expected to serve as a new technique with the potential for simple rapid evaluation of lectin-reactive AFP.

Lectin Reactivity of Alpha-Fetoprotein in a Case of Renal Cell Carcinoma

The increased serum level of alpha-fetoprotein (AFP) in a case of renal cell carcinoma, a rare condition of AFP production by mesoderm-derived cells, was evaluated for its lectin reactivity by affinity electrophoresis, followed by the antibody-affinity transfer to nitrocellulose membranes for visualization of separated AFP bands. The AFP of this case was characterized by relative increases of concanavalin A-nonreactive AFP-C1 (60.4%), erythroagglutinating phytohemagglutinin-reactive AFP-P4 (37.8%) and AFP-P5 (46.3%) and Allomyrina dichotoma lectin-nonreactive AFP-A1s (66.7%), and by the total absence of lentil lectin-reactive components, AFP-L2 and AFP-L3. Thus, the lectin-reactive pattern of AFP markedly deviated not only from that of cord serum, but also from those of other malignancies and of fetal kidney cells in culture.

Lectin-dependent modulation of interaction between human alpha-fetoprotein and its monoclonal antibodies epitope mapping

The effect of lentil lectin (LCA) on the binding of mouse monoclonal antibody (MoAb) against human α-fetoprotein (AFP) to LCA-nonreactive AFP-L1 and LCA-reactive AFP-L3 was studied on a panel of 30 MoAbs provided by the TD-2 Workshop of ISOBM for epitope mapping. LCA inhibited the binding of MoAbs 93 and 98 to AFP-L3 but not to AFP-L1, indicating that there was a competition between the MoAbs and LCA for the AFP sugar chain. With MoAbs 100, 109, 118, and 120, LCA rather increased the binding to AFP-L3 over that to AFP-L1. These modulating effects of LCA on the MoAb binding to AFP-L3 were abolished by periodate treatment of the AFP preparations without affecting the binding of MoAb to AFP. Concanavalin A had similar inhibiting and enhancing effects on MoAb binding, but equally to AFP-L1 and AFP-L3, both of which are fully reactive with concanavalin A. The results suggested that MoAbs 93 and 98 recognized epitopes closely related to sugar chain, and their binding to AFP-L3 was inhibited by the bound LCA due to steric hindrance. The enhanced binding of some MoAbs to AFP-L3 over AFP-L1 with LCA, or both glycoforms of AFP with concanavalin A, may be explained by postulating an allosteric mechanism mediated by the oligosaccharide-lectin interaction.

Increased serum levels of monosialo-alpha-fetoprotein in hepatocellular carcinoma and other malignancies.

Serum alpha-fetoprotein (AFP) from cord blood and from patients with hepatitis, cirrhosis, hepatocellular carcinoma, gastrointestinal tumors and yolk sac tumor was analyzed by extended agarose gel electrophoresis coupled with our sensitive detection method of antibody-affinity blotting. AFP was separated into AFP-A, AFP-B and AFP-C from the anode to the cathode, corresponding to disialo-, monosialo- and asialo-AFP, respectively, as revealed by the results of neuraminidase digestion of serum AFP. AFP-Af, which migrated ahead of AFP-A as band or leading smear and varied widely in intensity, was eliminated in calculating the proportions of other band intensities. Disialo-AFP was the major component and monosialo-AFP the minor one in benign conditions, the latter being 4.2 +/- 6.0% in chronic hepatitis and 9.0 +/- 8.9% in cirrhosis. Monosialo-AFP in hepatocellular carcinoma was increased significantly, the proportion being 29.9 +/- 11.2%. AFP in other malignancies was further characterized by the appearance of asialo-AFP.

The effect of estriol on the production of alpha-fetoprotein by the liver in adult mice

A single intraperitoneal injection with a 10 mg estriol (E3) in aqueous suspension induced a large and prolonged elevation of serum alpha-fetoprotein (AFP) in adult mice. E3 also raised the mitotic activity of hepatocytes in the absence of liver injury. Although both the AFP concentration and hepatocyte proliferation reached the peak on day 5 after E3 administration, a high level (about 12500 ng/ml) of serum AFP persisted for a long period after hepatocyte proliferation declined. Five mg E3 showed a remarkable threshold effect on AFP elevation and 3 mg E3 on hepatocyte proliferation. Immunohistochemical studies indicated AFP production by hepatocytes in adult mice after the E3 administration.

The Significance of the Determination of AFP· Isoform in the Early Diagnosis of Hepatocellular Carcinoma (HCC)

To evaluate the significance of the determination of the AFP-isoform in the early diagnosis of hepatocellular carcinoma (HCC), the AFP-isoform was determined in 48 patients with HCC and in 53 patients with liver cirrhosis, using the lectin electrophoresis of AFP by antibody-affinity blotting technique. 1. The HCC-type AFP-isoform was detected in 44 of the 48 patients with HCC, 2. In about 30% of the patients with HCC, the HCC-type AFP-isoform appeared 3-10 months before the graphic diagnosis of HCC, 3. In about 60% of the patients with liver cirrhosis found to have the HCC-type AFP-isoform, HCC developed within one year. Thus, the serial determination of the AFP-isoform in patients with liver cirrhosis was considered very useful for the early diagnosis of HCC.