Vector-based RNA interference against vascular endothelial growth factor-A significantly limits vascularization and growth of prostate cancer in vivo

RNA interference technology is emerging as a very potent tool to obtain a cellular knockdown of a desired gene. In this work we used vector-based RNA interference to inhibit vascular endothelial growth factor (VEGF) expression in prostate cancer in vitro and in vivo. We demonstrated that transduction with a plasmid carrying a small interfering RNA targeting all isoforms of VEGF, dramatically impairs the expression of this growth factor in the human prostate cancer cell line PC3. As a consequence, PC3 cells loose their ability to induce one of the fundamental steps of angiogenesis, namely the formation of a tube-like network in vitro. Most importantly, our "therapeutic" vector is able to impair tumor growth rate and vascularization in vivo. We show that a single injection of naked plasmid in developing neoplastic mass significantly decreases microvessel density in an androgen-refractory prostate xenograft and is able to sustain a long-term slowing down of tumor growth. In conclusion, our results confirm the basic role of VEGF in the angiogenic development of prostate carcinoma, and suggest that the use of our vector-based RNA interference approach to inhibit angiogenesis could be an effective tool in view of future gene therapy applications for prostate cancer.