**3.12 Urokinase-type plasminogen activator**

Urokinase-type plasminogen activator (uPA) is an important component participating in degradation of extracellular matrix and plays an important role in invasion and metastasis of tumor cells. Super-expression of uPA receptor (uPAR or PLAUR) is detected in many malignant tumor cells. Zhou (Zhou *et al,* 2009) used a retroviral vector carrying siRNA expressing target PLAUR to treat transplanted oral squamous cell carcinoma for 30 days, and found that the mean tumor size of the intervention group was 1382mm3 versus 4181mm3 in the NS control group. The number of apoptotic cells in the intervention group was significantly greater than that in the control group (32.7 vs 2.7, P<0.01). The expression level of u-PAR, MMP2, MMP9, VEGFD, VEGFC and VEGFR-3 in the intervention group decreased significantly, and proliferation-related Ki-67 was inhibited.
