[3] Mucin short variant S1 is a glycoprotein with extensive O-linked glycosylation of its extracellular domain.

Mucins line the apical surface of epithelial cells in the lungs, stomach, intestines, eyes and several other organs.

[5] Overexpression of MUC1 is often associated with colon, breast, ovarian, lung and pancreatic cancers.

[6] Joyce Taylor-Papadimitriou identified and characterised the antigen during her work with breast and ovarian tumors.

These repeats are rich in serine, threonine and proline residues which permits heavy o-glycosylation.

[7] Multiple alternatively spliced transcript variants that encode different isoforms of this gene have been reported, but the full-length nature of only some has been determined.

[10] This tight, non-covalent association is not broken by treatment with urea, low pH, high salt or boiling.

[14] In the cell nucleus, the protein MUC1 regulates the activity of transcription factor complexes that have a documented role in tumor-induced changes of host immunity.

[15] MUC1 has been shown to interact with: The ability of chemotherapeutic drugs to access the cancer cells is inhibited by the heavy glycosylation in the extracellular domain of MUC1.

The glycosylation creates a highly hydrophilic region which prevents hydrophobic chemotherapeutic drugs from passing through.

Association of MUC1 with p53 in cancer results in inhibition of p53-mediated apoptosis and promotion of p53-mediated cell cycle arrest.

This method would activate the immune system by training T-cells to search out and destroy cells that display a specific molecule (or marker) of MUC1.

[34] Because MUC1 is overexpressed (and differently glycosylated) in many cancers it has been investigated as a drug target, e.g. for the MUC1 vaccine ONT-10, which has had a phase 1 clinical study.

[35] This article incorporates text from the United States National Library of Medicine, which is in the public domain.