MUC-1/CD227

MUC-1 (CD227) is a large type I transmembrane mucin bearing a variable number tandem repeat domain densely decorated with O-linked glycans, extending far above the cell surface. In normal secretory epithelia MUC-1 is polarized to the apical membrane with heavily glycosylated repeats, but tumor cells lose polarity and express aberrantly glycosylated forms recognized as tumor-associated epitopes such as Tn and sialyl-Tn. MUC-1 is overexpressed in breast, pancreatic, ovarian, and lung cancers and circulates as a soluble antigen, supporting both diagnostic assays and MUC1-directed CAR-T and antibody development. The cytoplasmic tail of MUC-1 interacts with beta-catenin and other signaling proteins.