General Description
Tenascin (TN) is a high molecular weight, multifunctional, extracellular matrix glycoprotein, expressed in association with mesenchymal-epithelial interactions during development and in the neovasculature and stroma of undifferentiated tumors. Human TN has 3 subunits of 190, 200 and 220 kD. TN has been independently discovered in a variety of species and tissue types, often in the basement membrane or intercellular spaces. The expression of TN is associated with development and growth, both normal and pathological, with restricted distribution in normal adult tissue. It is synthesized by fibroblasts, chondroblasts, osteocytes, smooth muscle cells and glial cells. Human and chicken TN contain an RGD sequence which may function in cell adhesion and it seems likely that TN mediates cell attachment through an RGD-dependent integrin receptor. Mouse TN does not contain an RGD sequence in the third type III repeat implicated in cell attachment, or in any other positions.
Biochem/physiol Actions
Tenascin (TN) is up-regulated by epithelial transforming growth factor β (TGF-β) in mesenchyme. TN in the stroma of cancerous tissue contributes to tumorigenesis and progression of metastasis. High molecular weight TN isoform, a stromal marker of breast cancer, over-expresses implicating cell proliferation and invasion. TN has a potential role in tissue restoration. Intracytoplasmic TN immunoreactivity has been detected in malignant melanomas and in lung carcinomas. TN expression, when reacted with monoclonal antibody, determines its localization in tumor cells and its association with epithelial-mesenchymal and neuronal-glial cell interactions.
