Role of laminin-binding integrin in the invasion of basement membrane matrices by fibrosarcoma cells.

Laminin is a large glycoprotein that is found in basement membranes and promotes cell adhesion and migration. In human fibrosarcoma cells we detected the presence of an integrin complex, with a Mr of 140,000/120,000 under nonreducing conditions, that bound specifically to laminin-Sepharose columns. Immunoprecipitation with monoclonal antibodies characterized this complex as alpha 6 beta 1. Attachment of the fibrosarcoma cells to laminin substrates was completely inhibited in the presence of anti-alpha 6 beta 1 antibody, while attachment to fibronectin and type IV collagen was unaffected. When seeded onto reconstituted basement membrane, the fibrosarcoma cells spread out, migrated, and invaded the matrix. In the presence of anti-beta 1 or anti-alpha 6 beta 1 antibodies, initial invasion through the matrix was inhibited. The results indicate that the HT1080 cells express the alpha 6 beta 1 complex and that it mediates their attachment to laminin. Furthermore, this receptor appears to be important during initial attachment and subsequent invasion of basement membrane-like matrices.