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Short O-GalNAc glycans: regulation and role in tumor development and clinical perspectives

Joanne Chia1, Germaine Goh1, Frederic Bard2

  • 1Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, 138673, Singapore.

Biochimica Et Biophysica Acta
|March 13, 2016
PubMed
Abstract

Insights

Cancer cells exhibit altered O-GalNAc glycans (Tn and TF antigens), not due to incomplete processes but activated regulatory pathways. Understanding this regulation, particularly the GALA pathway, is key for cancer diagnostics and therapeutics.

Area of Science:

  • Biochemistry
  • Cancer Biology
  • Glycobiology

Background:

  • Cancer development involves genetic modifications and altered cellular states, notably changes in glycosylation.
  • Tumor cells frequently over-express O-GalNAc glycans, specifically Tn and TF antigens, though the mechanisms remain unclear.
  • Simple explanations like altered glycosylation enzyme levels do not fully account for the observed antigen overexpression.

Purpose of the Study:

  • To elucidate the regulatory mechanisms of O-GalNAc glycosylation initiation and extension.
  • To introduce the GALA pathway, a novel concept involving enzyme compartmentation in regulating Tn antigen levels.
  • To discuss the implications of O-GalNAc glycans and their regulatory enzymes (GALNTs) in cancer and explore diagnostic/therapeutic potential.

Main Methods:

  • Focus on the initiating enzymes of O-GalNAc glycosylation, polypeptide N-acetylgalactosaminyltransferases (ppGalNAcTs or GALNTs).
  • Description of the GALA pathway, detailing changes in GALNTs compartmentation within the secretory pathway.
  • Analysis of the roles of O-GalNAc glycans and GALNTs in tumorigenic processes.

Main Results:

  • Contrary to previous hypotheses, elevated short O-glycans in tumors indicate activated regulatory pathways, not incomplete glycosylation.
  • High Tn antigen levels signify a substantial shift in the O-glycoproteome, rather than a mere shortening of glycans.
  • These significant glycan alterations are driven by underlying membrane trafficking events.

Conclusions:

  • The study challenges the notion of incomplete glycosylation as the cause of short O-glycans in tumors.
  • Activation of specific regulatory pathways, including the GALA pathway, is responsible for altered O-glycan expression.
  • A deeper mechanistic understanding of O-GalNAc glycan regulation is crucial for developing effective biomarkers, antibodies, and therapeutic vaccines for cancer.
Keywords:
CancerGALNTsMembrane traffickingO-GalNAc glycosylation

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