Laminin, a glycoprotein (Mr 850 - 1.000 kD, composed of 3 glycosylated polypeptide chains at 440 and 225 kD each), is produced by various human epithelial and mesenchymal cells, forming an extracellular matrix of thin filaments. In normal tissues, laminin is consistently present in all basal laminas surrounding muscle, nerve, fat, and decidua cells, separating epithelial and endothelial cells from adjacent connective tissues. It has also been found within the cytoplasm of certain cells in the breast, endometrium, and liver. Laminin plays crucial roles in cellular activities such as adhesion, spreading, differentiation, polarization, proliferation, locomotion, tissue invasion, and chemotactic responses.