Gastrointestinal (GI) cancer is the most common group of malignancies and many of its
types are among the most deadly. Various glycoconjugates have been used in clinical
practice as serum biomarker for several GI tumors, however, with limited diagnose
application. Despite the good accessibility by endoscopy of many GI organs, the lack of
reliable serum biomarkers often leads to late diagnosis of malignancy and consequently
low 5-year survival rates. Recent advances in analytical techniques have provided novel
glycoproteomic and glycomic data and generated functional information and putative
biomarker targets in oncology. Glycosylation alterations have been demonstrated in a
series of glycoconjugates (glycoproteins, proteoglycans, and glycosphingolipids) that
are involved in cancer cell adhesion, signaling, invasion, and metastasis formation. In
this review, we present an overview on the major glycosylation alterations in GI cancer
and the current serological biomarkers used in the clinical oncology setting. We further
describe recent glycomic studies in GI cancer, namely gastric, colorectal, and pancreatic
cancer. Moreover, we discuss the role of glycosylation as a modulator of the function
of several key players in cancer cell biology. Finally, we address several state-of-the-art
techniques currently applied in this field, such as glycomic and glycoproteomic analyses,
the application of glycoengineered cell line models, microarray and proximity ligation
assay, and imaging mass spectrometry, and provide an outlook to future perspectives
and clinical applications
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