Basement Membrane Changes in Breast Cancer Detected by Immunohistochemical Staining for Laminin1

The distribution of the basement membrane glycoprotein laminin was studied by the immunoperoxidase technique in benign and malignant human breast tissue and in axillary lymph nodes from patients with breast cancer. An antiserum prepared against rat laminin was used. The specificity of this antiserum against human laminin was studied using the FL cell line of human epithelial-like cells derived from normal amniotic mem brane. The antiserum reacted with these cells in immunoperox idase staining and precipitated metabolically labeled secreted polypeptides which comigrated with polypeptides with molec ular weights of 400,000 and 200,000 of rat laminin in sodium dodecyl sulfate:polyacrylamide gel electrophoresis. The neoplastic cells in malignant breast tissues showed strong cytoplasmic staining for laminin, and a positive reaction was also found in lymph node métastases. In some cases in which only micrometastases were present, these cells also stained strongly for laminin. In nonmalignant breast tissues, the epithelial cells of the ducts were positive for laminin, but the staining was weaker than in the carcinomas. Pretreatment of the fixed tissue sections with trypsin markedly enhanced the staining of basement membranes for laminin. In trypsin-treated sections of normal breast tissue and benign lesions, the laminin staining delineated continuous basement membranes. In car cinomas representing the more differentiated types, basement membranes presumably produced by the tumor cells could be revealed by laminin staining, but they were thinner and discon tinuous. The poorly differentiated carcinomas lacked organized basement membranes detectable by laminin staining. Our studies suggest that staining for laminin may be a useful adjunct test for detection of micrometatases in lymph nodes. The correlation of disintegration of the laminin-containing base ment membranes of tumors with increasingly anaplastic ap pearance supports the notion that basement membranes may play a role in tumor invasion. noncollagenous glycoproteins. Among the latter, a noncollagenous glycoprotein component of the basement membrane, termed laminin, has been identified. Laminin has been isolated from basement membranes formed by a mouse tumor (31), from the extracellular matrix of cultured murine endodermal cells (5, 6, 28), and from a rat yolk sac tumor with abundant hyalin (33). Laminin is composed of disulfide-linked polypeptide chains with molecular weights of about 200,000 and 400,000 (6, 23, 28, 31). Laminin is biochemically and immunologically different from fibronectin, another extracellular ma trix glycoprotein, and from type IV collagen (6, 28, 31). Basement membrane proteins may be involved in cellular adhesion to basement membranes and extracellular matrix. Fibronectin mediates the attachment of a variety of cell types (25), whereas type IV collagen(s) and laminin may be primarily involved in the attachment of epithelial cells (3, 15, 30, 32). Malignant cells often display aberrations in their relationship to basement membrane components. For instance, they often lack cell surface fibronectin(s) and, at least in one case, the laminin that their normal counterparts have at the cell surface (12). Basement membranes are thought to form a protective bar rier against the initial infiltration of tissue by malignant cells, and the exceptional ability of metastatic cells to attach to the basement membrane of endothelial cells may play a role in the spread of tumors via circulation (16, 19, 32). These observa tions emphasize the need for further studies on the relationship of tumor cells to basement membranes. As laminin has been demonstrated recently by immunofluorescence in cultured hu man breast carcinoma cells (10), we found it of interest to examine the distribution of laminin in malignant and nonmalig nant breast tissue with special reference to the basement membranes. We show here that immunocytochemical staining of laminin reveals marked differences in the organization of basement membranes in normal breast tissue and breast can cer.