{"type":"root","children":[{"type":"paragraph","children":[{"type":"text","value":"Mucin 4 (MUC4) is a high-molecular weight glycoprotein and can range in molecular weight from 550 to 930 kDa. MUC4 is primarily expressed in epithelial tissues (i.e trachea, GI tract, lung, cervix, salivary glands), where it contributes to the production of mucin, a gel-like substance that forms protective barriers on the surfaces of epithelial cells. MUC4 is involved in cell-cell and cell-matrix interactions through its extracellular domains, which contain adhesive motifs such as EGF-like domains and SEA domains. These domains facilitate the binding of MUC4 to cell surface receptors and extracellular matrix proteins, mediating cell adhesion, migration, and signaling processes. Aberrant expression of MUC4 has been implicated in the pathogenesis and progression of various types of cancer. Overexpression of MUC4 is observed in several malignancies, including pancreatic cancer, breast cancer, ovarian cancer, lung cancer, and others. In cancer cells, MUC4 promotes tumor growth, invasion, metastasis, and resistance to chemotherapy through multiple mechanisms, including modulation of cell adhesion, signaling pathways, and immune responses."}]}]}