C1GALT1 and breast cancer: Previously, David et al. found that the expression level of Tn antigen in breast cancer was strongly influenced by GALNTs subcellular localization, and there was no lack of C1GALT1 activity in hundreds of human breast cancer samples with high expression of Tn antigen, but they found that GALNTs relocalization from the Golgi to the ER induced high expression of Tn antigen and promoted cell migration and invasion [82].