A panel of human tumor cell lines was screened for selective expression of
laminin alpha5 chain, a newly identified
laminin subunit comprising
laminin-10 (alpha5 beta1 gamma1) and -11 (alpha5 beta2 gamma1). The
lung adenocarcinoma cell line A549 was found to express the alpha5 chain at relatively high levels but no detectable amounts of other alpha chains. The
laminin variants containing alpha5 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 alpha5 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-alpha5 chain
monoclonal antibody capable of recognizing denatured alpha5 chain on immunoblots, whereas the 210-kDa chain was recognized by an anti-gamma1 chain antibody. The purified alpha5 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 alpha3 or beta1 subunit but not by those against alpha2 or alpha6 subunit, indicating that
laminin-10/11 is specifically recognized by
integrin alpha3 beta1. Given the wide distribution of
laminin-10/11 in the basement membrane of various tissue types and dominant expression of
integrin alpha3 beta1 in most epithelial cells, specific interaction of
laminin-10/11 with
integrin alpha3 beta1 may play an important role in in vivo regulation of proliferation and differentiation of epithelial cells through the basement membrane.