Purification of a tumor-specific PNA-binding glycoprotein, gp200, from a human embryonal carcinoma cell line

A 200-kDa peanut agglutinin (PNA)-binding glycoprotein, gp200, has been purified and partially characterized from the human embryonal carcinoma cell line, HT-E (833k). Tissue distribution analysis of this molecule by lectin blotting with PNA of detergent-extracted proteins from human cell lines and tissues demonstrated expression limited to nonseminomatous germ cell tumors. The 200-kDa protein was purified with lectin affinity and gel filtration chromatography. Purification to apparent homogeneity was demonstrated by one- and two-dimensional gel electrophoresis. Characterization of gp200 revealed it to be a surface integral membrane glycoprotein; however, gp200 could also be purified from the culture media of EC cells, suggesting gp200 has an extracellular role. The carbohydrate groups of gp200 are N-linked and partially sialylated and contain terminal galactose residues. These initial studies suggest that the PNA-defined glycoprotein, gp200, is a candidate for a nonseminomatous germ cell tumor marker.