Sialyl-Tn antigen on O-glycosylated mucins (Sialyl-Tn (STn) antigen)

Sialyl-Tn antigen is a carbohydrate structure (Neu5Acα2,6GalNAc-α-O-Ser/Thr) formed by sialylation of the Tn antigen on mucin-type O-glycoproteins. Normally, O-glycans on mucins undergo extensive elongation and modification in the Golgi apparatus, but in various cancers or genetic defects, glycosylation is truncated, leading to exposure of STn antigen[3][4][2][5]. Expression of STn on mucins significantly alters cellular properties, such as reducing adhesion, promoting immune evasion, and facilitating metastasis. STn is rarely found in healthy tissues but is a prominent marker and functional driver in carcinoma cells[2][4][5]. The antigen has been explored both diagnostically (biomarker for aggressive disease) and as a therapeutic target (vaccines, antibody-drug conjugates)[3]. The biosynthesis is regulated mainly by sialyltransferases (primarily ST6GalNAc-I) acting on the Tn antigen, and defects in glycosyltransferase enzymes or chaperones (notably Cosmc) lead to STn expression on mucin core proteins such as MUC1, MUC2, and others[2][3][6]. While most work has focused on cancer, STn antigen is also detected in other diseases exhibiting abnormal O-glycosylation, such as IgA nephropathy and rare genetic syndromes[3]. In summary, Sialyl-Tn antigen is a disease-associated, truncated, sialylated glycan epitope found on O-glycosylated mucins in carcinoma and select pathologies, serving as a target for experimental immunotherapies and a reliable biomarker for cancer progression[3][5][4].

Other names

Sialyl-Tn antigenSTn antigenNeu5Acα2,6GalNAc-α-Ser/ThrSialylated Tn antigen

Immunotherapeutic targeting (antibody-mediated recognition of STn on tumor cells) Induction of immune responses against STn-positive cancer cells (vaccine mechanism)