[A new tumor marker--novel gamma-GTP isoenzyme]

The authors discussed the clinical significance and some properties of the novel gamma-GTP isoenzyme (novel gamma-GTP) which was reported to be specific for sera of hepatocellular carcinoma (HCC) in our previous publications. One or more of specific bands (novel gamma-GTP) such as bands II, II' and I' were electrophoretically detectable in 109 (55%) of 200 patients with HCC, but only in 3% of 279 patients with other hepatobiliary diseases. Novel gamma-GTP was found in 38% of HCC patients with AFP levels below 400 ng/ml. The incidence of novel gamma-GTP was independent of the clinical stage as classified by liver scanning. Even in stage I, where filling defects were not seen, the incidence was 52%. It is concluded that novel gamma-GTP is useful in diagnosis of HCC patients with low levels of AFP or at a relatively early stage. Some properties of gamma-GTP purified from HCC tissues were investigated and compared with those of the normal kidney enzyme. The enzymes from HCC and kidney were identical in enzymatic and immunological properties, whereas a considerable difference was observed in electrophoresis, Con A affinity, effect of neuraminidase and isoelectric point. Respective bands II, II' and I' could be differentiated in Con A affinity and neuraminidase reaction. These results support the possibility that novel gamma-GTP in sera of HCC patients is largely due to a difference in carbohydrate moiety of gamma-GTPs.