Cationic lipid-based delivery system for systemic cancer gene therapy

A cationic lipid-based gene delivery system composed of N-[(1-(2,3-dioleylo xy)propyl)]-N-N-N-trimethylammonium chloride and cholesterol, at a 4:1 mola r ratio, was developed For systemic administration. Plasmid biodistribution and expression were characterized in syngeneic mouse tumor model squamous cell carcinoma VII cells. A reporter gene expression plasmid was used for b iodistribution of plasmid and expression. The results showed that lungs and primary tumors were transfected. Fluorescence microscopy showed that fluor escent-labeled transfection complexes were passively targeted to the tumor vasculature and that the endothelial cells internalized the plasmid. Transg ene expression was characterized based on duration of expression and dosing schedule. In vivo gene transfer with an interleukin-12 expression plasmid yielded protein levels in blood, lungs, and primary tumor after intravenous administration. Efficacy studies showed that 15 mu g of interleukin-12 pla smid was sufficient to produce a gene-specific inhibition of primary tumor growth. These results characterize the vascularity of the tumor model, char acterize the in vivo gene transfer properties of the plasmid-based gene del ivery system, and show that the transgene expression level was sufficient t o elicit a biological response by inhibiting tumor growth.