Polymorphic epithelial mucin, encoded by the MUC1 gene, is present at the apical surface of
glandular epithelial cells. It is over-expressed and aberrantly glycosylated in most breast
tumors, resulting in an antigenically distinct molecule and a potential target for
immunotherapy. This transmembrane protein, when produced by tumor cells, is often
cleaved into the circulation, where it is detectable as a tumor marker (CA 15.3) by various
antibodies, allowing for early detection of recurrences and evaluation of treatment efficacy …