Functional imaging of pericellular proteolysis in cancer cell invasion

Proteolytic interactions between cells and extracellular matrix (ECM) are involved in many physiological and pathological processes, such as embryogenesis, wound healing, immune response, and cancer. The visualization of cell-mediated proteolysis towards ECM is thus required to understand basic mechanisms of tissue formation and repair, such as the breakdown and structural remodelling of ECM, inflammatory changes of tissue integrity, and the formation of proteolytic trails by moving cells. A panel of synergistic techniques for the visualization of pericellular proteolysis in live and fixed samples allow monitoring the of proteolytic tumor cell invasion in three-dimensional (3D) fibrillar collagen matrices in vitro. These include the quantification of collagenolysis by measuring the release of collagen fragments, the detection of protease expression and local activity by dequenching of fluorogenic substrate, and the staining of cleavage-associated neoepitopes together with changes in matrix structure. In combination, these approaches allow the high-resolution mapping of pericellular proteolysis towards ECM substrata including individual focal cleavage sites and the interplay between cell dynamics and alterations in the tissue architecture.