Expression of Laminin Receptor in Normal and Carcinomatous Human Tissues as Defined by a Monoclonal Antibody

It has been hypothesized that epithelial and endothelial cells interact with the laminin component of basement membranes via a cell surface laminin receptor molecule. It has also been proposed that the expression of this molecule may be involved in the invasion of carcinoma cells from their tissue of origin and their subsequent penetration through blood vessel basement membranes. We report here the use of a monoclonal antibody, LR-3, to define the expression of laminin receptor in normal, dysplastic, and carcinomatous human tissues. Monoclonal antibody LR-3 is shown by immunoblotting to recognize the M_r 67,000 laminin receptor protein, to bind to the carcinoma cells, and to constitute approximately 0.1% of total cellular protein. Numerous normal human epithelial and endothelial cell types, as well as pulmonary macrophages, are shown to express laminin receptor to varying degrees. Selected human mammary carcinomas and colon carcinomas are shown to bind more monoclonal antibody LR-3 than normal or dysplastic counterparts. A monoclonal antibody to laminin receptor now makes possible the study of the role of laminin receptor in tumor cell metastases and in the differentiation and function of various normal human epithelial and endothelial cell types.