Antitumor effect utilizing antiangiogenic activity by RNAi as new gene knock-down method

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It has been known that tumors require ongoing angiogenesis to support their growth. Inhibition of angiogenesis by production of antiangiogenic factors should be a viable approach for cancer gene therapy. Similarly, inhibition of angiogenic factor has an impact to suppress the tumor growth. Vascular endothelial growth factor (VEGF) is a key regulator of tumor angiogenesis and many studies have shown that VEGF is upregulated in many human tumors. We have planned to inhibit vascular VEGF receptors using RNA interference (RNAi). RNAi is. a powerful tool to silence gene expression post-transcriptionally. The strategy to regulate the tumor angiogenesis with RNAi technique targeted VEGF in tumor cell. We investigated the silencing effect of small. interfering RNA (siRNA) duplexes targeting the gene VEGF-receptor (VEGFR) in vascular endothelial cell to inhibit its activity of angiogenesis and evaluated its effect against to the tumor progression in vivo model. We optimized the RNAi target sequence.of VEGFR-1. Transfection of VEGFR-1 siRNA to vascular endothelial cell specialy reduced VEGFR-1 mRNA level and inhibit the proliferation of transfected cell. The vector that express short hairpin RNAs (shRNA) working as the siRNA duplexes to VEGFR-1 gene was constructed. These vectors specially reduced VEGFR-1 expression. Further, the RNAi target sequence to VEGFR-2 was optimized and the shRNA targeted to VEGFR-2 expression vector was constructed. We investigated this powerful utility in in vivo model. The experiment showed that VEGFR-2-shRNA inhibited tumor progression. So we plan to evaluate the inhibitory effect in in vivo model of VEGFR-1-shRNA and mix of two kind of shRNA.