Selective isolation and analysis of glycoprotein fractions and their glycomes from hepatocellular carcinoma sera.

As one of the most important post-translational modifications, the discovery, isolation, and identification of glycoproteins are becoming increasingly important. In this study, a Con A-magnetic particle conjugate-based method was utilized to selectively isolate the glycoproteins and their glycomes from the healthy donor and hepatocellular carcinoma (HCC) case sera. The isolated glycoproteins and their N-linked glycans were identified by LC-ESI-MS/MS and MALDI-TOF/TOF-MS, respectively. A total of 93 glycoproteins from the healthy donors and 85 glycoproteins from the HCC cases were identified. There were 34 different glycoproteins shown between the healthy donors (21/34) and the HCC cases (13/34). Twenty-eight glycans from the healthy donors and 30 glycans from the HCC cases were detected and there were 22 different glycans shown between the healthy donors (10/22) and HCC cases (12/22). Among these glycoproteins, 50 were known to be N-linked glycoproteins and three novel glycopeptides from two predicted potential glycoproteins were discovered. Moreover, lectin blotting, Western blotting and lectin/glyco-antibody microarrays were applied to definitely elucidate the change of selective protein expressions and their glycosylation levels, the results indicated that the differences of the identified glycoproteins between the healthy donors and HCC cases were caused by the change of both protein expression and their glycosylation levels.