MMP9 and neoplasm: It is produced and secreted by tumor cells and stroma cells; under hypoxic conditions, it activates endothelial cell proliferation and migration (through the overexpression of MMP-2 and MMP-9) and induces vascular permeability that boosts hypoxia, which enhances recruitment of stromal cells, endothelial cells, immune and inflammatory cells, from the surrounding tissues [25].