Effect of PEG anchor in PEGylation of folate-modified cationic liposomes with PEG-derivatives on systemic siRNA delivery into the Tumor

In this study, we prepared small interfering RNA (siRNA)/cationic liposome complexes (lipoplexes) modified with folate (FA)-polyethylene glycol (PEG, MW 2000, 3400 or 5000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) to facilitate their uptake into tumor cells via folate receptor (FR), and with PEG(1600)-cholesterol (PEG(1600)-Chol) or PEG(2000)-chondroitin sulfate conjugate (PEG(2000)-CS), to enhance their systemic stability. Among the FA-PEG-modified siRNA lipoplexes, 0.5 mol% FA-PEG(5000)-DSPE-modified lipoplexes with 2.5 mol% PEG(2000)-CS or PEG(1600)-Chol (LP-0.5F(5)/2.5P(2)-CS and LP-0.5F(5)/2.5P(1.6)-CL, respectively) exhibited selective growth inhibition of human nasopharyngeal carcinoma KB cells through transduction with polo-like kinase 1 (PLK1) siRNA. Furthermore, the LP-0.5F(5)/2.5P(2)-CS and LP-0.5F(5)/2.5P(1.6)-CL lipoplexes exhibited decreased agglutination with erythrocytes through PEGylation, and markedly decreased the accumulation of siRNA in murine lungs after systemic injection. Finally, systemic injection of LP-0.5F(5)/2.5P(2)-CS and LP-0.5F(5)/2.5P(1.6)-CL lipoplexes resulted in accumulation of siRNA in KB tumor xenografts. These findings suggest that PEGylation of FA-PEG(5000)-DSPE-modified siRNA lipoplexes with PEG(2000)-CS or PEG(1600)-Chol might improve their systemic stability without the loss of selective transfection activity in tumor cells.

Automated summary

In this study, modified siRNA/cationic liposome complexes with enhanced stability and selective uptake into tumor cells were prepared. The modified complexes showed selective growth inhibition of human nasopharyngeal carcinoma cells and reduced accumulation in mouse lungs. These findings suggest the potential of PEGylated siRNA/cationic liposome complexes as an effective tool for tumor therapy.