Efficient Oncogene Silencing and Metastasis Inhibition via Systemic Delivery of siRNA

Abstract

The selective delivery of small interfering RNA (siRNA) to metastatic tumors remains a challenging task. We have developed a nanoparticle (NP) formulation composed of siRNA, a carrier DNA, a polycationic peptide, and cationic liposomes. The NP was obtained by a self-assembling process, followed by surface modification with a polyethylene glycol (PEG)-conjugated ligand, anisamide. The NP was PEGylated and a ligand was presented to target sigma receptor-expressing murine melanoma cells, B16F10. The lung metastasis model was established by intravenous (i.v.) injection of the B16F10 cells into C57BL/6 mice. A mixture of siRNA against MDM2, c-myc, and vascular endothelial growth factor (VEGF) co-formulated in the targeted NP caused simultaneous silencing of each of the oncogenes in the metastatic nodules. Two consecutive i.v. injections of siRNA in the targeted NP significantly reduced the lung metastasis (approximately 70-80%) at a relatively low dose (0.45 mg/kg), whereas free siRNA and the nontargeted NP showed little effect. This targeted NP formulation significantly prolonged the mean survival time of the animals by 30% as compared to the untreated controls. At the therapeutic dose, the targeted NP showed little local and systemic immunotoxicity and did not decrease the body weight or damage the major organs.

The Polyethyleneglycol Dilemma: Advantage and Disadvantage of PEGylation of Liposomes for Systemic Genes and Nucleic Acids Delivery to Tumors

“…56,57) Huang and coworkers demonstrated that a PEGylated liposome-polycation-dNA nanoparticle (LPD) modified with anisamide on top of PEG efficiently delivered siRNA to lung carcinomas with high expression levels of sigma receptors, which resulted in luciferase gene silencing in metastatic tumors compared with nontargeted PEGylated LPd. 58,59) Antibodies have been widely investigated as ligands for the tumor targeting of liposomes due to their high specificity and affinity for target molecules.…”

Therapeutic targeting in the silent era: advances in non-viral siRNA delivery

“…In a mouse model of metastasis, a mixture of siRNA against the cancer associated proteins MDM2, c-myc, and VEGF, co-formulated in the targeted formulation, administered intravenously caused simultaneous silencing of each of the genes. Importantly, the targeted nanoparticles at the therapeutic dose used, showed little local and systemic immunotoxicity, body weight alterations or damage to the major organs [78] .…”

“…Banerief et al [77] first demonstrated the use of the selective sigma ligand namely anisamide to mediate efficient targeting of liposomal drugs to sigma receptor-expressing prostate cancer cells in vitro and in vivo. Since then there have been several articles reporting the application of anisamide targeting nanoparticles for the cell specific delivery of therapeutic siRNA [78][79][80] .…”

“…As these ABCD formulations are nearly neutral or even negative in charge, the remarkable gene silencing data when administered systemically must be a result of active cell-specific targeting. Li and colleagues developed a nanoparticle formulation for successfully systemic delivery of siRNA into xenograft [122,80] and metastatic tumours [78,79] which produced anti-cancer effects. In this system, the nucleic acids (siRNAs and carrier DNA), a polycationic peptide (protamine) and a cationic liposome, were initially prepared in a condensed core.…”

“…In this system, the nucleic acids (siRNAs and carrier DNA), a polycationic peptide (protamine) and a cationic liposome, were initially prepared in a condensed core. The resulting core was then modified by PEG-lipid containing the tumour targeting ligand, anisamide (see above) [78][79][80] . The resulting targeted nanoparticles silenced the epidermal growth factor receptor (EGFR) in the tumour and induced ~15% tumour cell apoptosis without any indication of immunotoxicity [122] .…”