Liver Targeting of Plasmid DNA with a Cationized Pullulan for Tumor Suppression

The objective of this study is to prepare a novel gene carrier from pullulan, a polysaccharide with an inherent affinity for the liver and evaluate the feasibility in gene transfection in the mice liver. Pullulan with a weight-average molecular weight of 22,800 was cationized by the chemical introduction of spermine (spermine-pullulan). The cationized pullulan derivative was complexed with a plasmid DNA and intravenously injected for in vivo gene transfection. The level of gene expression by the spermine-pullulan in the liver depended on the extent of spermine introduced and the highest level was observed for the spermine-pullulan with an introduction extent of 5.60. When a plasmid DNA coding NK4 of a hepatocyte growth factor (HGF)/scatter factor antagonist complexed with the spermine-pullulan was intravenously injected to mice 1 day before the inoculation of RLmale1 tumor cells, the tumor-bearing mice survived for a longer time period, while the GPT level and the number of tumor cells grown in the liver were low compared with those of free plasmid DNA injection. These findings indicate that the liver targeting of NK4 plasmid DNA by complexation with the spermine- pullulan specifically enhanced the liver expression level, resulting in augmented suppression effect on tumor growth therein.