Abnormal glycosylation is a hallmark of cancer. Several tumor-associated carbohydrate antigens (TACAs, including Tn (GalNAcα1-O-Ser/Thr), STn (Neu5Acα2-6GalNAcα1-O-Ser/Thr) and T (Galβ1,3-GalNAcα1-O-Ser/Thr antigens (1,2), are highly expressed in cancerous cells compared to normal tissues (1,2). Antibodies targeting these antigens can act as biomarkers for cancerous cells (3) and have been used as platforms for diagnostics, therapeutics, and anti-cancer vaccines (4-6).
The Tn, STn and T antigens are often found as components of mucin protein, which are upregulated in cancerous cells (7). Mucins are large glycoproteins, either secreted from or membrane-bound in epithelial cells, in which O-linked oligosaccharides account for more than 50% of the molecule by weight (8). They are upregulated in cancerous cells and their localization changes from being on the apical side of normal epithelium to symmetrically distributed in malignantly transformed epithelium. Mucins are often abnormally glycosylated in cancerous cells and tissues (3, 7-9).