Silence of VEGFR2 expression mediated by PEI/siRNA complexes

The aim of this paper is to report the study on gene silencing efficiency of siRNA targeted against mouse VEGFR2 (siVEGFR2) in vitro mediated by polyethyleneimine (PEI) and its anti-tumor effect in vivo.  CY3-labeled siRNA was compounded into PEI and transfected into MS1 cells.  Confocal microscopy was used to image the subcellular distribution of siRNA in MS1 cells.  Semi-quantitative RT-PCR and Western blotting were used to evaluate VEGFR2 gene silencing induced by siVEGFR2/PEI complexes.  A tumor-bearing nude mice model was established to compare the anti-tumor effect after delivered by local and systemic routes.  siVEGFR2/PEI complex-transfected cells exhibited much fluorescence in cytoplasm with no evidence of nuclear accumulation.  The expression levels of VEGFR2 mRNA and protein in PEI-transfected cells were significantly down-regulated compared with that in blank group, the silencing efficiency were 28.2% and 23.6% respectively.  The tumor sizes in mice intratumorally injected with siVEGFR2/PEI complexes (189.429 ± 17.562 mm³) were reduced definitely compared to that in mice injected with siVEGFR2/PEI complexes via vein route (315.507 ± 20.491 mm³), or to saline groups (365.844 ± 20.713 mm³).  The study demonstrated that PEI could effectively transfect siRNA into cells and silence the VEGFR2 gene expression.  Intratumoral delivery is more suitable  for non-targeted modified PEI/siRNA complexes to inhibit the tumor growth in vivo.  The present data lay a solid foundation to further study on the gene silencing mechanism for PEI-medicated RNAi and its anti-tumor  efficiency in vivo.