Structural differences found in the asparagine-linked sugar chains of human chorionic gonadotropins purified from the urine of patients with invasive mole and with choriocarcinoma

Abstract

Paper electrophoresis of the oligosaccharide fraction obtained by hydrazinolysis of human chorionic gonadotropin (HCG), which was purified from the urine of two patients with invasive mole, gave fractionation patterns different from those of normal and hydatidiform mole HCGs. Structural study of the oligosaccharides in each fraction revealed that the triantennary complex-type asparagine-linked sugar chains, specifically found in choriocarcinoma HCGs, were included in the two HCG samples. However, the unusual biantennary complex type sugar chains, which are also specific for the tumor HCGs, were not detected at all. This result indicated that abnormal expression of N-acetylglucosaminyl-transferase IV during the development of choriocarcinoma occurs in two steps: (a) ectopic expression of the regular N-acetylglucosaminyltransferase IV; and (b) modification of the substrate specificity of the enzyme.