Sialyl-Tn antigen (STn) (STn)

Sialyl-Tn (STn) is a truncated O-glycan consisting of a sialic acid residue α2,6-linked to N-acetylgalactosamine (GalNAc) attached to serine or threonine residues on proteins, particularly tumor-associated mucins like MUC1 [mdpi.com, https://www.mdpi.com/1422-0067/17/3/273]. It is a well-characterized tumor-associated carbohydrate antigen (TACA) that is overexpressed in over 80% of human carcinomas, including breast, ovarian, and gastric cancers, but is rarely found in normal adult tissues [nih.gov, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4813192/]. The expression of STn is typically driven by the upregulation of the sialyltransferase ST6GalNAc-I or mutations in the COSMC chaperone, which leads to the premature termination of O-glycan chains [nih.gov, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4531092/]. STn plays a significant role in cancer progression by promoting cell migration, invasion, and immune evasion through interactions with receptors like Siglecs on immune cells [frontiersin.org, https://www.frontiersin.org/articles/10.3389/fonc.2021.661003/full]. Therapeutically, STn has been targeted by cancer vaccines such as Theratope, monoclonal antibodies like B72.3, and antibody-drug conjugates (ADCs) designed to induce anti-tumor immune responses or deliver cytotoxic payloads directly to malignant cells [harvard.edu, https://dash.harvard.edu/handle/1/33029773].

Other names

Neu5Acα2-6GalNAcα-O-Ser/ThrCD175sSialyl-TnsTnSialyl-Tn antigenTAG-72 epitope

Immunotherapy via vaccine-induced antibody production (e.g., Theratope), antibody-dependent cellular cytotoxicity (ADCC), and targeted delivery of cytotoxic agents through antibody-drug conjugates (ADCs) [mdpi.com, https://www.mdpi.com/1422-0067/17/3/273]. It also involves the inhibition of immune evasion by blocking the interaction between STn and sialic acid-binding lectins (Siglecs) on immune cells [frontiersin.org, https://www.frontiersin.org/articles/10.3389/fonc.2021.661003/full].