Figure 5.

Tn and STn antigens on tumor cells. Tn and STn antigens are tumor-associated carbohydrate antigens. They are not expressed on normal, nontransformed tissues. Defects in Cosmc or T-synthase can result in Tn/STn expression, although, to date, only defects in Cosmc have been observed in human tumors or cancer cell lines. Tn/STn expression is found on the majority of carcinomas and its expression correlates with progression of disease. However, the role for Tn/STn expression in tumorigenesis is unknown. Loss of O-glycosylation could lead to surface receptor dysregulation, changes in cell–cell and cell–matrix contacts, and/or immunoregulation. Subsequent changes in gene expression, signal transduction, and/or physicochemical interactions could facilitate tumor initiation, progression, and/or metastasis.