The distribution of fibronectin, laminin and tetranectin in human breast cancer with special attention to the extracellular matrix.

Since Coman in 1944 observed that decreased adhesiveness is a characteristic of malignant cells and Grobstein 10 years later demonstrated that epithelial and mesenchymal cells influence each other when separated by a cell-impermeable filter, components of the extracellular matrix have been suspected of playing an active role in cancer growth. Breast cancer is frequently characterized by an increase in connective tissue fibroblastic cells and extracellular matrix, the nature and molecular composition of which is gradually being revealed. Two of the most studied and hence best known components of extracellular matrix are fibronectin and laminin. They are called adhesive or structural glycoproteins, because they are part of the stabilizing scaffold, which links connective tissue cells to each other (fibronectin) and connects connective tissues with parenchymatous cells via basement membranes (laminin). Both molecules harbour a variety of specific binding sites, which allow them to participate actively in basic dynamic processes such as cell modulation, -attachment, -spreading and -migration. Tetranectin is a recently discovered protein of human plasma and nucleated cells, which is suspected of participating in tissue degradation and proteolysis through its specific binding to plasminogen, a member of the plasminogen activation system. The immunohistochemical studies of fibronectin, laminin and tetranectin, on which this thesis is based, were undertaken in order to investigate if qualitative or quantitative changes of these proteins between benign and malignant breast tissue would reflect the net effect of the different inherent characteristics of breast cancer cells known from experimental studies (i.e. unanchored growth, proteolysis, metastatic spread and de novo production of extracellular matrix components). A significant increase in stromal fibronectin was a consistent finding in all infiltrating carcinomas, permitting the discrimination between such tumors and benign proliferative lesions as well as between carcinomas with a sarcomatoid appearance and true breast carcinomas. However, as a possible consequence of tumor heterogeneity this stromal reactivity pattern varied and tended to disappear focally along the invasive front of tumors with a high metastatic potential. A concurrent increase in the tumor cell expression of FN was found in poorly differentiated tumors, which could either be due to increased fibronectin production by the more anaplastic tumor cells or internalization of exogenous fibronectin bound to its receptor. Whereas most of the extracellular fibronectin in breast cancer is thought to be produced by the stromal fibroblasts, extracellular laminin is considered a product of the epithelial tumor cells.(ABSTRACT TRUNCATED AT 400 WORDS)