PLAU and cancer: Metastasis of cancer cells involves various cytophysiological changes and the degradation of the extracellular matrix(ECM) by increasing the expression and activation of extracellular proteases, such as metalloproteinases (MMPs), urokinase-type plasminogen activator (u-PA), or serine proteinase, has been regarded as important in cancer invasion and metastatic processes [23].