Free alpha subunits of glycoprotein hormone with dissimilar carbohydrates produced by pathologically different...

The two kinds of glycoprotein hormone alpha subunit ectopically produced by an undifferentiated carcinoma of the left femoral region (TM-alpha) and an adenocarcinoma of the right external genitalia (FS-alpha) were examined for amino acid composition, isoelectric focusing, molecular weight, the ability to combine with standard hCG beta and affinity with lectins (Con A, Ricin and PNA). Both TM-alpha and FS-alpha exhibited immunoantigenicity similar to standard hCG alpha. Furthermore, there were no significant differences in the amino acid compositions of TM-alpha, FS-alpha or standard hCG alpha. In isoelectric focusing, while standard hCG alpha exhibited a neutral charge, both TM-alpha and FS-alpha exhibited strong negative charges. FS-alpha was as sensitive to sialidase as standard hCG alpha, whereas most of the TM-alpha exhibited resistance to sialidase. TM-alpha contains sialidase-insensitive peripheral material with a negative charge. The affinity with Ricin-Sepharose indicated that most of the FS-alpha and some of the TM-alpha may contain terminal sialic acid and the penultimate structure, Gal beta 1----4G1cNAc; the affinity with PNA-Sepharose indicated that both may also contain terminal sialic acid and the penultimate structure, Gal beta 1----3GalNAc. These observations suggest that dissimilar glycosylation processes are present in the carcinoma ectopic biosynthesis of glycoprotein hormone alpha subunit.