Nanoparticle-mediated anti-Her2/neu siRNA delivery for breast cancer therapy in vitro

Objectives Our three-component streptavidin nanoparticle has been shown in vitro and in vivo to target the Her2 epitopes on breast cancer cells while the tat transferring peptide can carry the radiolabeled DNA through the cell membrane without entrapment. These properties may be useful for the delivery of siRNA to tumor cells.

Methods The siRNA nanoparticle consisted of the anti-Her2/neu siRNA, the tat peptide and the Herceptin anti-Her2 antibody, each biotinylated and linked via streptavidin. The siRNA duplex was biotinylated on the sense strand for attachment. Controls consisted of a scrambled RNA duplex nanoparticle, free siRNA delivered by Oligofectamine, and Herceptin alone. The Her2+ BT-474 cells were incubated for 72 h at 0.5 and 5 nM and the surviving fraction, defined as the ratio of cells capable of forming colonies compared to cells incubated with PBS, was measured. Specific gene silencing was also measured by FACS.

Results The siRNA was largely protected from nuclease degradation within the nanoparticle. The anti-Her2/neu siRNA nanoparticle significantly (p < 0.01) inhibited survival compared to all controls at 5 nM, including Oligofectamine delivered free siRNA. The same significant decrease for the study nanoparticle compared to all controls was also observed in the Her2 gene expression at 5 nM. No significant differences in either survival fraction or gene expression was observed at 0.5 nM.

Conclusions The delivery nanoparticle with tumor targeting provided by the antibody and tumor cell accumulation without entrapment by the transferring tat peptide appears to deliver siRNA effectively into tumor cell in vitro and inhibits gene expression by an siRNA mechanism. Since the nanoparticle is designed for in vivo use, its ability to deliver siRNA following IV administration remains to be determined