Post-Translational Modification of the Membrane Type 1 Matrix Metalloproteinase (MT1-MMP) Cytoplasmic Tail Impacts Ovarian Cancer Multicellular Aggregate Dynamics

Membrane type 1 matrix metalloproteinase (MT1-MMP, MMP-14) is a transmembrane collagenase highly expressed in metastatic ovarian cancer and correlates with poor survival. Accumulating evidence shows that the cytoplasmic tail of MT1-MMP is subjected to phosphorylation, and this post-translational modification regulates enzymatic activity at the cell surface. To investigate the potential role of MT1-MMP cytoplasmic residue Thr567 phosphorylation in regulation of metastasis-associated behaviors, ovarian cancer cells that express low endogenous levels of MT1-MMP were engineered to express wild-type MT1-MMP, a phospho-mimetic mutant (T567E) or a phospho-deficient mutant (T567A). Results show that Thr567 modulation influences behavior of both individual cells and multi-cellular aggregates (MCAs). The acquisition of either wild-type or mutant MT1-MMP expression results in altered cohesion of epithelial sheets and the formation of more compact MCAs relative to parental cells. Cells expressing MT1-MMP-T567E phospho-mimetic mutants exhibit enhanced cell migration. Furthermore, MCAs formed from MT1-MMP-T567E-expressing cells adhere avidly to both intact ex vivo peritoneal explants and 3-dimensional collagen gels. Interaction of these MCAs with peritoneal mesothelium disrupts mesothelial integrity, exposing the sub-mesothelial collagen matrix on which MT1-MMP-T567E MCAs rapidly disperse. Together, these findings suggest that post-translational regulation of the Thr567 in the MT1-MMP cytoplasmic tail may function as a regulatory mechanism to impact ovarian cancer metastatic success.