PLAU and cancer: Metastasis of cancer cells involves various cytophysiological changes (e.g. EMT) and the degradation of the extracellular matrix (ECM) by increasing and activating extracellular proteases, such as MMPs, urokinase-type plasminogen activator (u-PA), or serine proteinase, which has been regarded as important in cancer invasion and metastasis processes [30].