[Binding of human chorionic gonadotropin with insufficient terminal sugar to peanut agglutinin]

We have studied the binding of human chorionic gonadotropin (hCG) in sera and urine of normal pregnant women and patients with trophoblastic diseases to the lectin from peanut (Arachis hypogaea, PNA). As the basic experiments, purified standard hCG and its alpha and beta subunits were examined for binding to a PNA-Sepharose column. Both standard hCG and hCG-beta adsorbed to the PNA-Sepharose only when they were treated with neuraminidase, whereas hCG-alpha was still not adsorbed even after treatment with neuraminidase. The major proportions of hCG in sera and urine from normal pregnancy and hydatidiform mole were not adsorbed to the PNA-Sepharose column. On the other hand, the proportions of PNA binding fraction in sera and urine from choriocarcinoma were significantly elevated in 4 of 6 cases. The PNA binding fraction was significantly higher in serum than in urine of each individual. The PNA binding fractions were extracted and purified from urine of 2 patients with choriocarcinoma, and were quantitatively found to be asialo-hCG. These results suggest that PNA-Sepharose affinity chromatography is an effective tool to use in detecting incompletely sialylated hCG and hCG-beta and may be a useful index for the clinical diagnosis of choriocarcinoma.