C1GALT1 and cancer: The APDTRP is an immunogenic epitope found in the tandem repeat sequence present in MUC1 and the APDT*RP, whose structure in the bound state with an antitumor antibody was recently reported28, is the basis for development of several cancer vaccines29, and it is a natural substrate for C1GalT1 in the context of MUC128,30.