Synergistic metalloproteinase-based remodeling of matrix by pancreatic tumor and stromal cells

The process by which tumor cells mechanically invade through the surrounding stroma into peripheral tissues is an essential component of metastatic dissemination. Matrix metalloproteinase (MMP)-mediated extracellular matrix (ECM) degradation plays an important role in this invasive process. Defining the contribution and interaction between these MMPs during invasion remains a key interest in the development of targeted anti-metastatic therapies. In this study we have utilized multiple different stromal fibroblasts and tumor cells to define the relative contributions between cancer cells and stromal cells during MMP-dependent matrix remodeling and pancreatic (PDAC) tumor cell invasion. We find that tumor cells co-cultured with the conditioned medium from stromal fibroblasts exhibited a substantial increase in invadopodial-based matrix degradation and transwell invasion. This increase is dependent on pro-MMP2 expressed and secreted by stromal fibroblasts. Further, the pro-MMP2 from the stromal fibroblasts is activated by MT1-MMP expressed on the tumor cells. Depletion of MT1-MMP, the known activator of MMP2, in tumor cells largely blocked matrix remodeling, even in the presence of stromal cell medium. In summary, these findings implicate an important interplay between MT1-MMP from tumor cells and MMP2 from fibroblasts as a key component for ECM remodeling and invasion.