Reflections on MUC1 glycoprotein: the hidden potential of isoforms in carcinogenesis

Mucin 1 ( MUC 1) has been described as the renaissance molecule due to the large set of functions it displays in both normal and neoplastic cells. This membrane‐tethered glycoprotein is overexpressed and aberrantly glycosylated in most epithelial cancers, being involved in several processes related with malignant phenotype acquisition. With a highly polymorphic structure, both in the polypeptide and glycan counterparts, MUC 1 variability has been associated with susceptibility to several diseases, including cancer. Biochemical features and biological functions have been characterized upon the full‐length MUC 1 protein, remaining to clarify the real impact on cell dynamics of the plethora of MUC 1 isoforms. This review aims to encompass a detailed characterization of MUC 1 role in carcinogenesis, highlighting recent findings in cell differentiation and uncovering new evidences of MUC 1 isoforms involvement in malignant phenotype.