PLG and neoplasm: The uPA system, including uPA, plasminogen activator inhibitor (PAI)-1, PAI-2, and uPA-associated receptor (uPAR), regulates the production and function of uPA to modulate the conversion from plasminogen to plasmin, which promotes the proteolytic cleavage of extracellular matrix (ECM) surrounding the tumor with matrix metalloproteinases (MMPs), facilitating the detachment of tumor cells from an original site and the initiation of invasive and metastasis (84) (Figure 3).