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Progression and Metastasis of Mammary Carcinomas: Potential Role of the Muc1 Glycoprotein.

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Our goal is to understand the function of the tumor-associated mucin, MUC 1, in the progression of cancer in the mammary gland. MUC1 is highly expressed by the majority of cancers and, in particular, by 92 of primary and metastatic breast cancers. The MUC 1 protein is a large, rod-like molecule that projects far from the cell surface as a long filament. The protein core is extensively glycosylated through 0-glycosidic linkage to serine and threonine, with as much as 50 to 90 of its molecular mass made up of oligosaccharide side chains. This contributes significantly to the rigidity of the molecule. MUC 1 is expressed on normal epithelial tissues at low levels. Appearance of MUC 1 correlates closely with epithelial differentiation in various organs and is detected well before the organs are functional. The presence of the large, highly extended molecule of MUC 1 on the surface of epithelia suggests that it may act as a physical barrier protecting the cells. MUC 1 may be involved in epithelial morphogenesis, perhaps acting to mask adhesive molecules present on the cell surface and aiding in the formation of a lumen. When epithelial tissues become cancerous, MUC 1 expression is increased formation of a lumen. When epithelial tissues become cancerous, MUC 1 expression is increased at least ten fold, and the glycosylation and spatial distribution of the protein at the cell surface are altered. MUC 1 in normal polarized epithelia is expressed only at the apical side of lumens and ducts. However, in many adenocarcinomas polarization is lost, and the protein is found over the entire surface of the cells.

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  • Medicine and Medical Research

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