Efficient Gene Silencing In Prostate Cancer By Sirna In Novel "Aptamer Leading Cationic Liposome" Targeting Delivery System

Prostate cancer is one of the most common malignant tumor in male reproductive system, and the men’s health is threatened severely by the increasing incidence in recent years. At present, surgical treatment、endocrine treatment、radiotherapy and chemotherapy are the commonly traditional treatments. But the treatment effort is very limited, long-term alleviation or cure is hard to achieve and even have serious side effects. Nowadays, with the rapid development of molecular biology and biochemistry, how to really know and treat diseases from their molecular level has gradually become the focal point of human beings. With the research of the disease pathogenesis, people realize that the only way to cure the malignant tumor, is focus on the aspect of cancer development mechanism. Therefore, to structure a novel, safety, high efficiency gene therapy method of prostate cancer is very important for both clinical significance and application value. RNA interference (RNAi) is a specific gene silencing phenomenon that induced by a small interfering RNAs to isogeny mRNA.Because of its specificity、high performance and duration, its investigation and application has become a hot spot for molecular biology. At the same time, the technology also develop a new pathway for gene therapy of correlated clinic diseases.LPD (liposome-protamine-calf thymus DNA) is a novel cationic liposomes for siRNA delivery. They composed of nucleic acids, a polycationic peptide and cationic liposome, and were prepared in a self-assembling process. Unlike the common liquid structure of liposomes, the novel delivery system was prepared by condensing the siRNA and calf thymus DNA with protamine into a compact complex.Drug delivery is still a problem of gene therapy for prostate cancer in vivo. In this study, we focus on two aspects-targeting delivery and safely encapsulation, oligonucleotide aptamer as a ligand specifically targeting to prostate-specific membrane antigen (PSMA) was synthesized by a novel method of transcription with chemical modification, using the reverse evaporation technique for the preparation of liposomes, encapsulating the exact silence effect siRNA, and connect both oligonucleotide aptamer and liposome-siRNA complexes with specific chemical method in order to build a novel "aptamer-liposomes" siRNA targeting delivery system capable of PSMA-specific binding. Using Plk-1as a target, stability, targeting and validity of the novel targeting delivery system were evaluated in cell level in vitro. As a result, novel delivery system,which had a particle size of151±6.1nm, and the average zeta potential was40±5.8mV, comparing with antibody, could more specifically bind to LNCap cells and was sequentially internalized into them. Confocal microscope studies demonstrated that, our system showed a much better accumulation and distribution in the tumor cells. RT-PCR experiments proved that it can silence the expression of specific targeted Plk-1gene.The subject could provide theoretical and experimental basis of siRNA for prostate cancer treatment in vivo, while provide new ideas to the targeted cancer gene therapy.