Importance of altered glycoprotein-bound N- and O-glycans for epithelial-to-mesenchymal transition and adhesion of cancer cells.

Aberrant glycosylation of cell surface glycoproteins acquired during malignant progression is a common characteristic of human cancer cells. Several biological processes and molecular mechanisms relevant for tumour progression are accompanied by altered mRNA expression levels of certain glycosyltransferases resulting in unusual ratios of common glycoconjugates present in a cancer cell's glycocalyx or even in the development of unusual, cancer-characterizing carbohydrates. This mini-review aims to give a concise overview on the current knowledge of the functional relevance of altered O- and N-glycans during two critical steps of tumour progression: (I) epithelial-to-mesenchymal transition of primary tumour cells during intravasation and (II) adhesion of circulating tumour cells towards the vascular wall during extravasation at a distant metastatic site. Characteristic lectin binding patterns reflecting these glycosylation changes and the resulting prognostic impact of certain lectin binding sites in different neoplasias are reviewed as well.