Development of siRNA Delivery System by Lipid Nanoparticles Modified with Functional Materials for Cancer Treatment.

Nucleic acid drugs can control gene expression and function in a manner different from that of conventional compounds. On the other hand, nucleic acids can be easily degraded in the in vivo circumstances. In addition, nucleic acids cannot penetrate cell membranes. Therefore, a drug delivery system (DDS) is essential to protect nucleic acid molecules until they reach the target cell and to release them efficiently inside the cell. In order to apply nucleic acid drugs to new cancer therapeutic strategies, the author has been developing a DDS that enables functional control of vascular endothelial cells that consist of the tumor microenvironment. The aim of my study is to develop lipid nanoparticles (LNPs) were modified with functional molecules that control their pharmacokinetics in vivo and intracellular fate to delivered small interfering RNA (siRNA) to tumor vasculature. By imparting pH-responsive membrane fusion properties to lipid nanoparticles, I have developed a system that responds to acidification in endosomes within cells and subsequently efficiently releases siRNA into the cytoplasm via membrane fusion, where siRNA molecules exhibit their function. In addition, by developing a method for presenting functional molecules, such as peptides, saccharides and so on, that recognize target cells on the surface of LNPs, I succeeded in establishing LNPs which internalize more efficiently into specific cells than off-target cells. Finally, by integrating these technologies, I developed an in vivo siRNA DDS that enables in vivo control of genes of interest in tumor vascular endothelial cells and succeeded in cancer therapy by regulating vascular function.