The STn is a cancer-associated short O-glycan typically absent in normal healthy tissues, which arises from the early sialylation of the Thomsen-nouveau (Tn) antigen due to the overexpression of the enzyme ST6GalNAc-I and/or disruption of the core 1 O-glycan elongation in various cancers, including bladder, colon, ovarian and breast9–15. This evidence concerns the gene ST6GALNAC1 and cancer.