Role of cell surface metalloprotease MT1-MMP in epithelial cell migration over laminin-5

Laminin-5 (Ln-5) is an extracellular matrix substrate for cell adhesion and migration, which is found in many epithelial basement membranes. Mechanism s eliciting migration on Ln-5 need to be elucidated because of their releva nce to tissue remodeling and cancer metastasis. We showed that exogenous ad dition of activated matrix metalloprotease (MMP) 2 stimulates migration ont o Ln-5 in breast epithelial cells via cleavage of the gamma 2 subunit. To i nvestigate the biological scope of this proteolytic mechanism, we tested a panel of cells, including colon and breast carcinomas, hepatomas, and immor talized hepatocytes, selected because they migrated or scattered constituti vely in the presence of Ln-5. We found that constitutive migration was inhi bited by BB94 or TIMPs, known inhibitors of MMPs. Limited profiling by gela tin zymography and Western blotting indicated that the ability to constitut ively migrate on Ln-5 correlated with expression of plasma membrane bound M T1-MMP metalloprotease, rather than secretion of MMP2, since MMP2 was not p roduced by three cell lines (one breast and two colon carcinomas) that cons titutively migrated on Ln-5. Moreover, migration on Ln-5 was reduced by MT1 -MMP antisense oligonucleotides both in MMP2+ and MMP2- cell lines. MT1-MMP directly cleaved Ln-5, with a pattern similar to that of MMP2. The hemopex in-like domain of MMP2, which interferes with MMP2 activation, reduced Ln-5 migration in MT1-MMP+,MMP2+ cells, but not in MT1-MMP+, MMP2- cells. These results suggest a model whereby expression of MT1-MMP is the primary trigg er for migration over Ln-5, whereas MMP2, which is activated by MT1-MMP, ma y play an ancillary role, perhaps by amplifying the MT1-MMP effects. Codist ribution of MT1-MMP with Ln-5 in colon and breast cancer tissue specimens s uggested a role for this mechanism in invasion. Thus, Ln-5 cleavage by MMPs may be a widespread mechanism that triggers migration in cells contacting epithelial basement membranes.