MUC1 and cancer: However, in cancer-related MUC1, its structure was found to have changed—overexpressed due to loss polarity in epithelial cells, and the carbohydrate side chain becomes uncomplete and forms new carbohydrate side chains (Thomsen-Friedenreich (TF or T), Tn, and sialyl-Tn (STn)) and exposure of the core peptide (Figure 1B) [3,29,30].