[Relationship of an extracellular matrix protein, tenascin and breast diseases]

Tenascin is an extracellular matrix glycoprotein consisting of six disulfide-linked subunits with molecular masses of 190-250 kDa. Molecular analysis of the tenascin gene revealed that it contains a region homologous to epidermal growth factor genes, repetitive sequences of the type III fibronectin and the fibrinogen gene. Culture studies have shown that tenascin has multiple functions including cell attachment and detachment, promotion and inhibition of neural crest cell migration, cell growth stimulation and hemagglutination. Immunohistochemically, tenascin shows a characteristic and spatially restricted distribution. In mouse mammary glands, tenascin protein is demonstrated in the dense mesenchyme present around growing epithelia during embryogenesis and oncogenesis. Tenascin is expressed in normal human adult breast tissue and benign conditions, although it is expressed more abundantly in breast cancer tissue. Prominent tenascin staining is found in dense cancer-mesenchymal junctions. The staining positivity is significantly correlated with metastasis to regional lymph nodes and tumor grade. Tenascin positive patients have a significantly poorer prognosis compared with tenascin-negative patients. Although the biological functions of tenascin in breast cancer tissue have not yet been clearly elucidated, tenascin staining in surgical tissue specimens might be useful when applied to detect a subgroup of breast cancer patients who have a poorer prognosis.