An Experimental Research About PEI-PEG-Angiopep Mediated Thymidine Kinase Target To Glioma For Treatment

Gene therapy is one of the effective methods for glioma treatment. Thymidine kinase(TK) can transform ganciclovir into cytotoxic substances Ganciclovir Triphosphate(GCV-TP). Then, GCV-TK can disturb DNA replication resulting in cell death. In addition, GCV/TK treatment also showed a bystander effect.So far, major TK delivery vehicles are virus and stem cells. However, virus system has security issues and stem cell has limitations in application. Both defects limited the application of gene therapy for glioma. Polyethyleneimine(PEI) is widely used in cell transfection as gene delivery vehicle, which could be used in gene therapy. In addition, modified PEI may also have potential in targeted delivery process.In this study, we found that TK/GCV treatment could effectively inhibit the proliferation of HEK293 T and SHG44 cells, which showed time and concentration dependent manners. The IC50 of GCV in TK-positive HEK293 T and SHG44 cells were 53.0 μM and 15.49 μM, which were higher than TK-negative cells. So the presence of TK can directly regulate the sensitivity of tumor cells against GCV. In addition, when TK-positive and TK-negative SHG44 cells were mix-cultured, all cells dead after GCV treatment. This result indicated TK had a bystander effect. We also found TK could inhibit tumor growth in vivo after GCV treatment.In order to avoid the security issues of virus system, we constructed a PEI-PEG gene delivery system. Results showed PEI-PEG could effectively deliver TK to tumor cells. The expression of TK could transform GCV to GCV-TP resulting in glioma cells death. In order to fulfill brain targeted gene delivery, we further modified PEI-PEG with a brain targeting group(Angiopep) and a glial cell specific promoter(GFAP). These modifications enabled a brain targeted gene delivery and a glial cell specific gene expression, which had greater potential in clinic glioma treatment. A U87MG-Luc orthotopic glioma models was also established to further validate our gene therapy strategy in vivo.