Notably, compared to MUC1 expressed by healthy cells, cancer-derived MUC1 is aberrantly glycosylated, exhibiting GalNAcα1-Ser/Thr modification (Tn antigen) and other truncated O-glycans due to a lack of core 1 β3-galactosyltransferase (T-synthase) activity [14,15,16]. Here, MUC1 is linked to cancer.