Sialyl-Tn antigen on Mucin-1 (STn-MUC1)

The Sialyl-Tn antigen on Mucin-1 (STn-MUC1) is a cancer-associated *O*-glycan structure (Neu5Acα2-6GalNAcα1-O-Ser/Thr) attached to the peptide backbone of the transmembrane mucin glycoprotein Mucin-1 (MUC1). Under normal conditions, MUC1 carries extended and highly branched glycans, modulating epithelial barrier and cell protection functions. In many cancers, including up to 90% of breast and 70–90% of major adenocarcinomas, aberrant glycosylation leads to truncated glycans such as STn, exposing neoepitopes that drive immune evasion, promote tumor invasiveness, and correlate with poor prognosis[4][5][6][7][8]. The STn-MUC1 antigen is nearly absent from normal adult cells, making it a priority target for cancer immunotherapy. Efforts include the development of STn-MUC1-specific monoclonal antibodies (e.g., L2A5), vaccines, and antibody-drug conjugates[4][5]. STn-MUC1 interaction with immune cell surface receptors (e.g., Siglec-9, MGL) shapes local immunosuppression and can induce immune checkpoint ligand expression (PD-L1), further supporting its relevance in therapeutic and diagnostic oncology[6][8].

Other names

Sialyl-Tn-MUC1sTn antigen on Mucin-1Sialyl-Thomsen-nouveau antigen on MUC1Sialyl-Tn-MUC1 glycopeptide

Antibody-mediated targeting for cancer therapy (immune-targeted destruction of STn-MUC1 expressing tumor cells) Vaccine-induced cytotoxic T cell activation against STn-MUC1-positive cancer Inhibition of immune checkpoint upregulation (via anti-STn antibodies preventing STn interaction with Siglec-9 and consequent PD-L1 upregulation)