Molecular characterization of tumor associated antigen in mice exposed to a hepatocarcinogen

The present investigation is aimed to identify and characterize tumor-associated antigen (TAA) in animals exposed to hepatocarcinogen. Swiss albino mice showed an enhanced expression of an approximately 58 kDa glycoprotein in liver cells upon exposure to a potential hepatocarcinogen N-nitrosodibutylamine (DBN). Carcinogenesis induction in mice was monitored by assays of γ-glutamyl transpeptidase (GGT), acetylcholine esterase (AChE), glutathione-S-transferase (GST) activities and the level of glutathione (GSH) in liver. DBN treated animals showed cell distortion and extensive necrosis as observed by histological examination. The over-expressed TAA was purified by ion-exchange chromatography and further characterized by SDS-PAGE. The carbohydrate contents and glycan linkage to the polypeptide backbone was analyzed by using the DIG glycan differentiation and de-glycosylation kits. The glycoprotein has glycan chains that are N-linked via asparagines to the polypeptide backbone. It was also observed that the molecule is rich in sialic acid residues with a significantly high carbohydrate to protein ratio (≥2:1). The over-expressed high molecular weight glycoprotein TAA was found to be highly immunogenic and could eventually be used to induce immune response in order to counter tumor regression. (Mol Cell Biochem 271: 177–188, 2005)