MUC1 is a member of the mucin family and encodes membrane-bound glycosylated phosphoproteins. Mucins are arranged on the apical surface of the lung, stomach, intestine, eyes, and several other organ epithelial cells. Mucin protects the body from infection by pathogens and oligosaccharides in the extracellular domain, thereby preventing pathogens from reaching the cell surface. Overexpression of MUC1 is often associated with colon cancer, breast cancer, ovarian cancer, lung cancer and pancreatic cancer. Proteins play a protective role by binding to pathogens and play a role in cell signaling ability. Overexpression of this protein, abnormal intracellular localization and changes in glycosylation are associated with cancer. In the nucleus, protein MUC1 regulates the activity of transcription factor complexes, which have a proven role in tumor-induced changes in host immunity. The ability of chemotherapeutic drugs to enter cancer cells is inhibited by heavy chain glycosylation in the MUC1 extracellular domain. Glycosylation produces highly hydrophilic regions that prevent the passage of hydrophobic chemotherapeutic agents. This prevents the drug from reaching the targets that are normally present in the cell. Likewise, glycosylation has been shown to bind to growth factors. This allows cancer cells that produce large amounts of MUC1 to concentrate growth factors near their receptors, increasing receptor activity and cancer cell growth. MUC1 also prevents the interaction of immune cells with cancer cell surface receptors by steric hindrance. This inhibits the anti-tumor immune response. Gatipotuzumab is a humanized monoclonal antibody that recognizes tumor-specific epitopes of MUC1 and is capable of distinguishing between tumor MUCl and non-tumor MUCl epitopes. Phase II clinical trials of ovarian cancer are currently underway.
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