Mucin 1 protein (MUC1)

Mucin 1 protein is a high molecular weight transmembrane glycoprotein encoded by the MUC1 gene. It is heavily O-glycosylated along its extracellular domain with variable numbers of tandem repeats rich in serine and threonine residues. Normally expressed at the apical surface of many glandular epithelial cells—including those lining the respiratory tract, gastrointestinal tract, reproductive organs—it forms part of mucus that protects against pathogens by acting as a physical barrier. The cytoplasmic tail participates actively in intracellular signaling pathways that regulate cell proliferation, survival/apoptosis balance, motility/migration/invasion potential—functions often hijacked during oncogenesis. Overexpression or abnormal localization/glycosylation is strongly associated with several carcinomas where it contributes to tumor progression through enhanced growth signals and evasion from immune surveillance. Clinically relevant epitopes such as CA 15–3 serve as biomarkers for diagnosis/prognosis/monitoring especially in breast cancer patients; novel therapies are under investigation aiming at direct inhibition or immune targeting of aberrant forms present on malignant cells.

Other names

Tumor-associated mucin 1 proteinPolymorphic epithelial mucin (PEM)Epithelial membrane antigen (EMA)CA 15-3CD227KL-6CanAg tumor antigen

Inhibition of cell signaling pathways mediated by the cytoplasmic tail of MUC1 (e.g., MAPK/ERK, PI3K/Akt); Disruption or modulation of cell adhesion and antiadhesion properties; Targeting aberrant glycoforms as immunotherapeutic antigens.