Isolation and Characterization of Laminin-10/11 Secreted by Human Lung Carcinoma Cells

Abstract

A panel of human tumor cell lines was screened for selective expression of laminin α5 chain, a newly identified laminin subunit comprising laminin- 10 (α5β1γ1) and -11 (α5β2γ1). The lung adenocarcinoma cell line A549 was found to express the α5 chain at relatively high levels but no detectable amounts of other α chains. The laminin variants containing α5 chain were purified from the conditioned medium of A549 cells by immunoaffinity chromatography using the anti-laminin monoclonal antibody 4C7 which was shown recently to recognize the laminin α5 chain (Tiger, C.-F., Champliaud, M.-F., Pedrosa-Domellof, F., Thornell, L.-E., Ekblom, P., and Gullberg, D. (1997) J. Biol. Chem. 272, 28590-28595). The purified laminin variants consisted of three chains with molecular masses of 350, 220, and 210 kDa. The 350-kDa chain was specifically recognized by another anti-α5 chain monoclonal antibody capable of recognizing denatured α5 chain on immunoblots, whereas the 210-kDa chain was recognized by an anti-γ1 chain antibody. The purified α5 chain-containing laminin variants (hereafter referred to as laminin-10/11) were highly active in mediating adhesion of A549 cells to the substratum with potency as high as that of laminin-5 and significantly higher than those of laminin-1, laminin-2/4, or fibronectin. Adhesion to substrata coated with laminin-10/11 was specifically inhibited by anti-integrin antibodies directed against the integrin α3 or β1 subunit but not by those against α2 or α6 subunit, indicating that laminin-10/11 is specifically recognized by integrin α3β1. Given the wide distribution of laminin-10/11 in the basement membrane of various tissue types and dominant expression of integrin α3β1 in most epithelial cells, specific interaction of laminin-10/11 with integrin α3β1 may play an important role in in vivo regulation of proliferation and differentiation of epithelial cells through the basement membrane.