Mucin Gene Expression in Lung Cancer Tissues

TABLE I PROBES USED FOR IDENTIFYING MUCIN GENE EXPRESSION Sirs, Epithelial mucins are large complex glycoproteins consisting of a non-globular protein backbone to which oligosaccharides are attached (1-3). The polypeptidic structure has a molecular weight ranging from 40 kD to 100 kD and it has a high percentage of serine, threonine, arginine, glycine and proline. Carbohydrates form the main component of mucin and the most important glycans are N-acetylgalactosamine, Nacetylglucosamine, galactose, fucose and sialic-acid (4, 5). Comparison of amino acid and sugar composition has revealed extensive heterogeneity among mucins from different sources. The heterogeneity in amino acid composition may reflect the fact that at least four different genes exist which code for different apomucins. These genes have been termed MUC-l (6, 7), MUC-2 (8), MUC-3 (9) and MUC-4 (10)and they have been isolated from human breast, pancreas, intestine and tracheobronchial tissues, respectively. Sequence analysis of the cDNA showed that the apomucins are similar in structure. In fact, the proteins consist ofthree different regions: an extracellular amino terminus domain; a transmembrane domain and an intracellular carboxyl terminus domain. The most striking feature of the molecule is the