The abnormal occurrence and the differentiation-dependent distribution of N-acetyl and N-glycolyl species of the ganglioside GM2 in human germ cell tumors. A study with specific monoclonal antibodies

Abstract

Human primary germ cell tumors were analyzed for the presence of the ganglioside GM2 using three specific monoclonal antibodies which can distinguish the molecular species of the sialic acid moiety: the antibody MK1-16 is specific for N-acetyl GM2, MK2-34 is specific for N-glycolyl GM2, and MK1-17 detects both N-acetyl and N-glycolyl GM2. When the occurrence of the GM2 antigen was tested in 107 cases of human germ cell tumors by the immunohistochemical technique using these antibodies, seminoma was characterized as having the highest frequency of N-acetyl GM2 (89.4%, 42 of 47 cases) among germ cell tumors, followed by embryonal carcinoma (40.0%), and teratocarcinoma (26.6%). Compared with this, yolk sac tumors and choriocarcinoma had a much lower positive incidence of the N-acetyl GM2 antigen. On the other hand, the N-glycolyl GM2 antigen was not found at all in 47 cases of seminoma (0%), and the positive incidence was very low in embryonal carcinoma (6.6%), although considerably higher incidences were obtained with choriocarcinoma (25.0%), yolk sac tumor (22.2%), and teratocarcinoma (13.3%). The presence and molecular species of the GM2 antigens in these human germ cell tumors were also ascertained chemically by the thin-layer chromatography (TLC) immunostaining of the ganglioside fractions prepared from primary germ cell tumors. These results indicate that seminoma specifically contains N-acetyl GM2 and no N-glycolyl GM2, suggesting that N-acetyl GM2 could be a good marker for seminoma. On the other hand, non-seminomatous germ cell tumors were characterized by the presence of N-glycolyl GM2, one of the Hanganutziu-Deicher antigens (H-D antigens). Moreover, the positive occurrence of N-glycolyl GM2 correlated very well with the degree of differentiation of non-seminomatous germ cell tumors, i.e., the differentiated tumors such as yolk sac tumors, choriocarcinoma, and teratocarcinoma had a higher positive incidence of N-glycolyl GM2 type H-D antigen but a lower positive incidence of N-acetyl GM2 when compared with embryonal carcinoma, the most undifferentiated tumors among non-seminomatous germ cell tumors.