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. ' UICCKey words: RNA interference; urokinase-type plasminogen activator receptor; oral squamous cell carcinoma; metastasis; cancer progression Oral squamous cell carcinoma (OSCC) accounts for about 80% of all oral malignant tumors. The 5-year survival rate for patients with OSCC was still poor, approximately 56%, despite advances in chemotherapy, radiotherapy and surgical therapy in the past 20 years.1,2 The relatively high mortality of OSCC is predominantly associated with widespread lymphatic and distant metastasis.

Hypoxia Inducible Factor 1α and Hypoxia Inducible Factor 2α Play Distinct and Functionally Overlapping Roles in Oral Squamous Cell Carcinoma

“…This may explain why knockdown of HIF-2α had no effect on cell proliferation at either 5% O 2 or 1% O 2 , whereas knockdown of HIF-1α significantly inhibited the cell proliferation at 1% O 2 . uPAR, a serine proteinase receptor, activates plasminogen and matrix metalloproteinase, and finally facilitates matrix remodeling and cell migration (24). We observed that the hypoxic induction of uPAR was regulated by HIF-1α, but not HIF-2α, in OSCC cells, indicating a prometastatic role of HIF-1α in OSCC.…”

The importance of oncogenic transcription factors for oral cancer pathogenesis and treatment

“…92,93 Recent evidence suggests that the RNAi-mediated downregulation of HIF-1a affects vascular endothelial GF expression as well as tumor cell proliferation, angiogenesis, apoptosis, and xenograft growth of OSCC. 68 Similarly, indirect targeting of CK2 by RNAi in HNSCC modulates the DNA-binding activity of NF-kB and p53/ p63, 13 which subsequently induces cell death.…”

Apoptosis-inducing activity and tumor-specificity of antitumor agents against oral squamous cell carcinoma

“…RNAi targeting urokinase-type plasminogen activator receptor (u-PAR) induced apoptosis as well as oral cancer invasion and metastasis [55]. Stable transfection of intracellular fragment of Notch induced G0-G1 cell cycle arrest and apoptosis in human tongue cancer cell line (Tca8113), accompanied by down-regulation of Wnt-b-catenin, increase of p21 and p53 expression, and decrease in Skp2 (S-phase kinase-associated protein 2) and Bcl-2 (B-cell lymphocytic-leukaemia protooncogene 2) expression [56].…”