siRNA targeting VEGF inhibits hepatocellular carcinoma growth and tumor angiogenesis in vivo

Background/Aims We have investigated whether siRNA targeted against VEGF inhibits functional properties of endothelial cells in vitro and HCC tumor growth and blood vessel formation in vivo. Methods The influence of siRNA-VEGF on endothelial cell proliferation, apoptosis and tube formation were analyzed in vitro. Antitumoral effects were examined in an orthotopic tumor model after ex vivo transfer or intraperitoneal treatment of siRNA, respectively. Intratumoral microvessel density was assessed by CD31 staining. Results VEGF expression was inhibited in Hepa129 by 70% and in SVEC4-10 by 48% within two days after transfection. In vitro, endothelial cell proliferation and tube formation was reduced by 23% and 38%, respectively. Interference with VEGF signaling was demonstrated by reduced pAKT in hepatoma cells. Tumor growth was inhibited by ex vivo transfer or intraperitoneal application of siRNA-VEGF by 83% or 63% in orthotopic tumors within 14 days. VEGF protein was reduced in both models by 29% and 44%. Microvessel density dropped to 34% for tumors from ex vivo transfected cells and 39% for systemic treated tumors. Conclusions The results show that VEGF knockdown can be associated with reduced endothelial cell proliferation and tube formation in vitro and decreased tumor growth and microvessel density in vivo.