Mucin-1 (MUC1) is also known as Tumor-associated epithelial membrane antigen (EMA), Polymorphic epithelial mucin (PEM), Peanut-reactive urinary mucin (PUM), PEMT, Krebs von den Lungen-6 (KL-6), CD antigen CD227, Episialin, H23AG. MUC1 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. Mucins protect the body from infection by pathogen binding to oligosaccharides in the extracellular domain, preventing the pathogen from reaching the cell surface. Except protective function by binding to pathogens, MUC1 also functions in a cell signaling capacity. Overexpression of MUC1 is often associated with colon, breast, ovarian, lung and pancreatic cancers.