title: Methods for the absolute quantification of N-glycan biomarkers.
abstract: BACKGROUND
  Many treatment options especially for cancer show a low efficacy for the majority of patients demanding improved biomarker panels for patient stratification. Changes in glycosylation are a hallmark of many cancers and inflammatory diseases and show great potential as clinical disease markers. The large inter-subject variability in glycosylation due to hereditary and environmental factors can complicate rapid transfer of glycan markers into the clinical practice but also presents an opportunity for personalized medicine.
  
  
  METHODS
  This review discusses opportunities of glycan biomarkers in personalized medicine and reviews the methodology for N-glycan analysis with a specific focus on methods for absolute quantification.
  
  
  CONCLUSIONS
  The entry into the clinical practice of glycan markers is delayed in large part due to a lack of adequate methodology for the precise and robust quantification of protein glycosylation. Only absolute glycan quantification can provide a complete picture of the disease related changes and will provide the method robustness required by clinical applications.
  
  
  CONCLUSIONS
  Glycan biomarkers have a huge potential as disease markers for personalized medicine. The use of stable isotope labeled glycans as internal standards and heavy-isotope labeling methods will provide the necessary method precision and robustness acceptable for clinical use. This article is part of a Special Issue entitled "Glycans in personalized medicine" Guest Editor: Professor Gordan Lauc.
authors.affiliation: CIC biomaGUNE, Paseo Miramon 182, 20009 San Sebastian, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Etxebarria
authors.affiliation: CIC biomaGUNE, Paseo Miramon 182, 20009 San Sebastian, Spain; CIBER-BBN, Paseo Miramon 182, 20009 San Sebastian, Spain. Electronic address: nreichardt@cicbiomagune.es.
authors.forename: Niels-Christian
authors.initials: NC
authors.lastname: Reichardt
mesh_terms: D015415:Biomarkers; D054794:Glycomics / Q000379:methods*; D006801:Humans; D011134:Polysaccharides / Q000235:genetics / Q000378:metabolism; D057285:Precision Medicine / Q000379:methods*
chemical_list: D015415:Biomarkers; D011134:Polysaccharides
keywords: Cancer; Glycan standards; Isotopic dilution; Mass spectrometry; Personalized medicine