Mucin 6, oligomeric mucus/gel-forming, also known as MUC6. The MUC6 gene encodes gastric mucin, a secreted glycoprotein that plays an essential role in epithelial cytoprotection from acid, proteases, pathogenic microorganisms, and mechanical trauma in the gastrointestinal tract. Normal gastric mucosa also expresses MUC1, MUC4, MUC5AC, and MUC6, with MUC1, MUC5AC, and MUC6 being the most prominent. MUC6 is expressed in mucopeptic cells of the neck region of the body and in pyloric glands of the antrum. It may provide a mechanism for modulation of the composition of the protective mucus layer related to acid secretion or the presence of bacteria and noxious agents in the lumen. MUC6 also play an important role in the cytoprotection of epithelial surfaces and are used as tumor markers in a variety of cancers and participates in epithelial organogenesis.