Département de médecine oncologique, Institut Curie, 26, rue d’Ulm, 75231 Paris Cedex 05, France
Polymorphic epithelial mucin (PEM), encoded by the MUC1 gene, is present at the apical surface of glandular epithelial cells. It is both overexpressed and aberrantly glycosylated in the majority of breast tumours, resulting in an antigenically distinct molecule and a potential target for immunotherapy trials. This transmembrane protein is cleaved into the circulation where it is detectable as a tumour marker (CA15.3) by a variety of antibodies, allowing for early detection of recurrences as well as evaluation of treatment efficacy. We shall review here the molecular structure of this protein at the basis for its immunogenicity and discuss preclinical and clinical trials in progress using immunogens based on MUC1. We shall also briefly review the altered immune reactivity in cancer patients.