title: Label-free glycopeptide quantification for biomarker discovery in human sera.
abstract: Glycan moieties of glycoproteins modulate many biological processes in mammals, such as immune response, inflammation, and cell signaling. Numerous studies show that many human diseases are correlated with quantitative alteration of protein glycosylation. In some cases, these changes can occur for certain types of glycans over specific sites in a glycoprotein rather than on the global abundance of the glycoprotein. Conventional analytical techniques that analyze the abundance of glycans cleaved from glycoproteins cannot reveal these subtle effects. Here we present a novel statistical method to quantify the site-specific glycosylation of glycoproteins in complex samples using label-free mass spectrometric techniques. Abundance variations between sites of a glycoprotein as well as different glycoforms, that is, glycopeptides with different glycans attached to the same site, can be detected using these techniques. We applied our method to an esophageal cancer study based on blood serum samples from cancer patients in an attempt to detect potential biomarkers of site-specific N-linked glycosylation. A few glycoproteins, including vitronectin, showed significantly different site-specific glycosylations within cancer/control samples, indicating that our method is ready to be used for the discovery of glycosylated biomarkers.
authors.affiliation: School of Informatics & Computing, Indiana University , 901 East 10th Street, Bloomington, Indiana 47408, United States.
authors.forename: Anoop
authors.initials: A
authors.lastname: Mayampurath
authors.forename: Ehwang
authors.initials: E
authors.lastname: Song
authors.forename: Abhinav
authors.initials: A
authors.lastname: Mathur
authors.forename: Chuan-Yih
authors.initials: CY
authors.lastname: Yu
authors.forename: Zane
authors.initials: Z
authors.lastname: Hammoud
authors.forename: Yehia
authors.initials: Y
authors.lastname: Mechref
authors.forename: Haixu
authors.initials: H
authors.lastname: Tang
mesh_terms: D000704:Analysis of Variance; D014408:Biomarkers, Tumor / Q000097:blood*; D002853:Chromatography, Liquid; D004938:Esophageal Neoplasms / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics / Q000502:physiology*; D006020:Glycopeptides / Q000032:analysis*; D006031:Glycosylation; D006801:Humans; D015233:Models, Statistical; D011134:Polysaccharides / Q000737:chemistry; D040901:Proteomics / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D014408:Biomarkers, Tumor; D006020:Glycopeptides; D011134:Polysaccharides
keywords: biomarker discovery; glycoproteomics; label-free quantification; site-specific glycosylation