MUC1 and cancer: Furthermore, tumor associated MUC1 has drastically shorter O-glycans in the tandem repeat region of MUC1 made of 20-amino acid residues (APDTRPAPGSTAPPAHGVTS) (Gendler et al., 1990), which leads to the exposure of the protein core, rendering it a highly attractive antigen for anti-cancer immune-therapy (Gendler et al., 1988; Hanisch et al., 1989).