B4GALNT1 and cancer: The immediate product of the GalNAc-Ts is also known as the Tn (GalNAcα1-O-Ser/Thr) antigen (if sialylated the STn (NeuAcα2-3GalNAcα1-O-Ser/Thr) antigen), and while this structure in normal cells is masked by elongation of the glycan structures by a number of other glycosyltransferases, expression of Tn (and STn) is a hallmark of cancer cells7, 8.