(640e) Comparison of In Vivo and In Vitro Delivery of Oligonucleotide Containing Lipopolyplexes for Cancer Therapy

Transferrin (Tf) conjugated lipopolyplexes (LPs) carrying oligonucleotides (ONs) such as antisense ODN and siRNA were synthesized and evaluated in Tf receptor positive cells and in a murine cancer xenograft model. In vitro, Tf-LP was more effective in down regulation of Bcl-2 in cells than non-targeted LP and free ON. The LPs were then evaluated in athymic mice carrying subcutaneous xenograft tumors by i.v. injection. Both treatment groups showed Bcl-2 down regulation by immunohistochemical staining and Western blotting. However, the Tf-LP was less effective than free ON, in contrast to the findings in vitro, probably due to the limited diffusion rate of LPs following extravasation. To investigate this possibility, an in vitro 3D cell cluster model was created by microcapsule technique and treated with both LPs and free ONs. The results indicated limited penetration of LPs into the cell cluster. The therapeutic efficacies of Tf-LP-ODN and free ODN were determined in the xenograft cancer model. Tf-LP-ODN showed slower plasma clearance, higher AUC, and greater accumulation in the tumor compared to free ODN. Tf-LP-ODN was found to be more effective in tumor growth inhibition and prolongation of survival than free ODN. This was associated with increased spleen weight and IL-12 production in the plasma. These results suggested a role of CpG effect to the immune system in the therapeutic response with the Tf-LPs.