Targeted Delivery of PLK1-siRNA by ScFv Suppresses Her2⁺ Breast Cancer Growth and Metastasis 

Yan-dan Yao, Tian-meng Sun, Song-yin Huang, Shuang Dou, Ling Lin, Jia-ning Chen, Jian-bin Ruan, Cheng-qiong Mao, Feng-yan Yu, Mu-sheng Zeng, Jian-ye Zang, Qiang Liu, Feng-xi Su, Peter Zhang, Judy Lieberman, Jun Wang, Erwei Song.Targeted Delivery of PLK1-siRNA by ScFv Suppresses Her2⁺ Breast Cancer Growth and Metastasis. Sci. Transl. Med.2012, 4(130):130ra48.

A major obstacle to developing small interfering RNAs (siRNAs) as cancer drugs is their intracellular delivery to disseminated cancer cells. Fusion proteins of single-chain fragmented antibodies (ScFvs) and positively charged peptides deliver siRNAs into specific target cells. However, the therapeutic potential of ScFv-mediated siRNA delivery has not been evaluated in cancer. Here, we tested whether Polo-like kinase 1 (PLK1) siRNAs complexed with a Her2-ScFv-protamine peptide fusion protein (F5-P) could suppress Her2(+) breast cancer cell lines and primary human cancers in orthotopic breast cancer models. PLK1-siRNAs transferred by F5-P inhibited target gene expression, reduced proliferation, and induced apoptosis of Her2(+) breast cancer cell lines and primary human cancer cells in vitro without triggering an interferon response. Intravenously injected F5-P/PLK1-siRNA complexes concentrated in orthotopic Her2(+) breast cancer xenografts and persisted for at least 72 hours, leading to suppressed PLK1 gene expression and tumor cell apoptosis. The intravenously injected siRNA complexes retarded Her2(+) breast tumor growth, reduced metastasis, and prolonged survival without evident toxicity. F5-P-mediated delivery of a cocktail of PLK1, CCND1, and AKT siRNAs was more effective than an equivalent dose of PLK1-siRNAs alone. These data suggest that F5-P could be used to deliver siRNAs to treat Her2(+) breast cancer.