RNAi targeting urokinase-type plasminogen activator receptor inhibits metastasis and progression of oral squamous cell carcinoma in vivo

Abstract

It has been admitted that urokinase-type plasminogen activator receptor (u-PAR) is overexpressed in many human malignant tumors including oral squamous cell carcinoma (OSCC) and plays an important role in a variety of cancer key cellular events as a versatile signaling orchestrator. In our study, a retroviral vector expressing u-PAR-specific siRNA was injected into OSCC xenografts of nude mice to observe its inhibitory effects on OSCC. Our data demonstrate that siRNA targeting u-PAR markedly suppressed tumor growth, reduced the expression of proliferation-related gene, Ki-67 and increased cell apoptosis, accompanying with the efficient and specific inhibition of endogenous u-PAR expression in OSCC. More importantly, the mRNA and protein expression of MMP-2, MMP-9, VEGF-C, VEGF-D and VEGFR-3 that are intimately involved in oral cancer invasion and metastasis, was simultaneously downregulated significantly as determined by quantitative real-time RT-PCR, Western blot and immunohistochemistry; and Gelatin and fibrin zymography showed that MMP-9, MMP-2 and u-PA enzymatic activities were significantly reduced in u-PAR-specific siRNA group, compared to those in control groups. In addition, the expression of MDR-1 gene related to drug resistance was obviously inhibited by silencing of u-PAR. These findings suggest that RNAi targeting u-PAR could effectively inhibit the metastasis and progression of OSCC in vivo. Thus, it may be used as a potent and specific therapy for oral cancer, especially in inhibiting and preventing cancer cell invasion and metastasis. © 2009 UICC.