Mucin macromolecules in normal, adenomatous, and carcinomatous colon: evidence for the neotransformation.

Mucins are high molecular-weight glycoproteins having oligosaccharides attached to serine or threonine residues of the mucin core protein backbone by O-glycosidic linkages. They are major components of mucus, covering the luminal surfaces of epithelial respiratory, gastrointestinal and reproductive tracts, and responsible for its viscoelastic properties. The core proteins of mucins are encoded by different mucin genes. Aberrations in the cell surface carbohydrates including mucins have been regarded as a universal characteristic of the malignant transformation of cells. These alterations are considered to be relevant to the abnormal behaviour of cancer cells, such as altered cell adhesion or metastasis, and to the avoidance of immunological defence.