Glycosylation of serum haptoglobin as a marker of gastric cancer: an overview for clinicians.

Introduction: Gastric cancer (GC) is one of the leading causes of cancer-related death worldwide because of difficulties in early diagnosis. Aberrant glycosylation in serum proteins has been associated with many human diseases. Serum haptoglobin, a highly sialylated glycoprotein with four N-glycosylation sites, has gained considerable attention due to its potential as a signature molecule to display aberrant glycosylation in inflammatory disorders and various types of cancer. In particular, the relevance of haptoglobin glycosylation in GC has been investigated in a multifaceted way.Areas covered: The screening of haptoglobin glycosylation could offer an alternative approach toward GC diagnosis and detection. In this report, various assay platforms such as glycan profiling, site-specific glycopeptide profiling, and intact protein profiling are introduced for the detection of abnormal glycosylation of serum haptoglobin.Expert opinion: Although aberrant glycosylation of serum haptoglobin is associated with gastric cancer patients and might be a promising marker of GC screening, the development of a diagnosis platform to increase specificity and sensitivity for clinical use is still an analytical challenge. However, the continuous advancement of analytical technologies and methods will spur the paradigm shift from traditional serum markers, enabling the effective mining of human glycoproteome for GC diagnostic markers.