Sialyl-Tn antigen on mucin-type glycoproteins (STn antigen)

The Sialyl-Tn antigen (STn antigen) is a carbohydrate epitope formed by the sialylation (α2-6 linkage) of N-acetylgalactosamine (GalNAc) α1-O-linked to serine or threonine residues on mucin-type glycoproteins (Neu5Acα2-6GalNAcα1-O-Ser/Thr)[2][3][1]. It represents one of the simplest forms of O-glycan and is normally rare or absent in healthy adult tissues but becomes abundantly expressed on the surface of several epithelial cancer cells, making it a classical oncofetal antigen[2]. This aberrant expression contributes to tumor progression, immune evasion, and poor prognosis, particularly in cancers such as breast, colorectal, bladder, pancreas, and ovary[2][3][1]. STn antigen's restricted cancer-associated pattern and cell-surface exposure make it a prominent tumor marker, therapeutic target for experimental anti-STn antibodies and vaccines, and a potential biomarker for cancer diagnosis, prognosis, and therapeutic monitoring[2][1]. Challenges with targeting STn include suboptimal immunogenicity, antibody specificity, inter- and intra-tumoral expression heterogeneity, and the technical complexities of targeting glycan epitopes therapeutically[1][2].

Other names

Sialyl-Tn antigenSialyl-Tn (STn)CD175sNeu5Acα2-6GalNAcα1-O-Ser/Thr (chemical structure notation)Oncofetal sialyl-Tn antigen

Monoclonal antibodies: bind to STn antigen exposed on tumor cells, enabling immune-mediated elimination (antibody-dependent cell-mediated cytotoxicity, complement activation) or direct targeting for immunotherapeutic intervention[1][2] - Cancer vaccines: elicit immune response against tumor cells expressing STn, potentially leading to tumor destruction[2]