Soluble Flt-1 gene delivery using PEI-g-PEG-RGD conjugate for anti-angiogenesis.

Vascular endothelial growth factor (VEGF), a potent angiogenic molecule specific for vascular endothelial cells, is overexpressed in most tumors and closely associated with tumor growth and metastasis. It has been shown that a soluble fragment of VEGF receptor Flt-1 (sFlt-1) has anti-angiogenic properties by way of its antagonist activity against VEGF. In the present study, we demonstrated that the stable expression of sFlt-1 by endothelial cell targeted non-viral gene delivery inhibited the angiogenesis of endothelial cells. A targeted polymeric gene delivery system, PEI-g-PEG-RGD, was developed by incorporating the alphanubeta3/alphanubeta5 integrin-binding RGD peptide, ACDCRGDCFC (single-letter amino acid code), into the cationic polymer, polyethylenimine (PEI) via a hydrophilic polyethylene glycol (PEG) spacer. The functional analysis of therapeutic gene encoding sFlt-1/carrier complex was performed with an endothelial cell proliferation assay. The complex of sFlt-1 gene with PEI-g-PEG-RGD conjugate efficiently inhibited the proliferation of cultured endothelial cells, representing that expressed sFlt-1 predominantly bound to exogenous VEGF and blocked the binding of VEGF to the full-length Flt-1 receptor. These findings suggest that the combination of targeted gene carrier and sFlt-1 possesses the potential to be an efficient tool for the anti-angiogenic gene therapy to treat cancer.