An improved polyethylenemine/DNA vector formulation that exhibits highly efficient in vitro and in vivo gene delivery

Polyethylenimine is a branched chain polycation that is capable of mediating endosome release as well as acting as both a DNA-binding agent and a point of ligand attachment. Our previous studies have demonstrated that the highest amount of transduction we could obtain was at an amine to phosphate ratio of 8/1, resulting in variable transduction efficiencies as high as 30∼40% with high toxicity. We report here that we have now reformulated how PEI and DNA are combined and have developed a novel PEI/DNA vector formulation that achieves reproducible transduction levels as high as 90% in cultured bladder, brain, breast, kidney, lung, and prostate cancer cell lines. More interestingly, transduction efficiencies as high as 99% could be achieved in leukemia cell lines, which are usually very difficult to transduce with most viral and non-viral vectors. This level of transduction also demonstrated very low toxicity, since we were able to utilize amine/ phosphate ratios of 3/1 or less. Efficient transduction was also obtained in vivo. An intralesional injection of just 6∼12 micrograms of vector into a subcutaneous tumor generated 10⁸ RLU/gram of tissue. In addition, a similar dose of vector given 7 times over a 14-day period resulted in a >50% reduction in tumor size when the tumor suppressor p53 gene was delivered. As a result, we have developed a simple and efficient gene delivery vector based on a novel PEI/DNA formulation that could now be used in the development of a safe and simple gene delivery vector for the treatment of cancer in the clinical setting.