Transferrin receptor targeted lipopolyplexes for delivery of antisense oligonucleotide G3139 in a murine K562 xenograft model

Purpose: Transferrin (Tf) conjugated lipopolyplexes (LPs) carrying G3139, an antisense oligonucleotide for Bcl-2, were synthesized and evaluated in Tf receptor positive K562 erythroleukemia cells and then in a murine K562 xenograft model. Materials and Methods: Particle size and Zeta potentials of transferrin conjugated lipopolyplexs containing G3139 (Tf-LP-G3139) were measured by Dynamic Light Scattering and ZetaPALS. In vitro and in vivo sample's Bcl-2 downregulation was analyzed using Western blot and tumor tissue samples also exhibited by immunohistochemistry method. For athymic mice bearing with K562 xenograft tumors, tumor growth inhibition and survival rate were investigated. Nanoparticle distribution in 3-D cell cluster was observed by Laser scan confocal microscopy. IL-12 production in the plasma was measured by ELISA kit. Results: In vitro, Tf-LP-G3139 was more effective in inducing down regulation of Bcl-2 in K562 cells than non-targeted LP-G3139, free G3139 and mismatched control ODN-G4126 in the same formulation. In vivo Tf-LP-G3139 was less effective than free G3139 in Bcl-2 down regulation. 3-D cell cluster model diffusion results indeed indicated limited penetration of the LPs into the cell cluster. Finally, the therapeutic efficacies of Tf-LP-G3139 and free G3139 were determined in the K562 xenograft model. Tf-LP-G3139 showed slower plasma clearance, higher AUC, and greater accumulation in the tumor compared to free G3139. In addition, Tf-LP-G3139 was found to be more effective in tumor growth inhibition and prolonging mouse survival than free G3139. This was associated with increased spleen weight and IL-12 production in the plasma. Conclusion: The role of the immune system in the therapeutic response obtained with the Tf-LPs is necessary and in vitro 3-D cell cluster model can be a potential tool to evaluate the nanoparticle distribution.