Breast cancer associated mucin: a review

Breast mucins are expressed by malignant epithelial cells and they elicit an immune reaction. The up-regulation of mucin expression is association with tumour invasion, this mucin called MUC-1 reduces the cell-cell interaction facilitating cell detachment. The MUC-1 gene product, known as polymorphic epithelial mucin is a transmembrane high molecular weight glycoprotein. The molecule of MUC-1 has a central polypeptidic core with a carbohydrate linked in O-linkage to serines and threonines. The carbohydrate side chain epitope of MUC-1 molecule produced by breast cancer cells is heavily sialylated, giving their physical properties and increasing their immunogenicity. The development of monoclonal antibodies (MAb) has led to study the MUC-1 in subcellular extracts, tissues and culture supernatants from breast cancer and also colorectal carcinoma. The pattern of tumour cell staining with labeled MAb varies according with the grade of malignancy; these MAb bind either to peptide sequence and/or to the glycosylated epitopes. MUC-1 has a clinical relevance because serum concentrations may be useful for monitoring the response to therapy and progress of disease. MUC-1 epitope masking has been described since specific antibodies can combine with them forming immune complexes. Finally, mucins have been considered to develop vaccines against cancer, targeting specific carbohydrate and mucin epitopes.