Theranostics 2017; 7(17):4204-4216. doi:10.7150/thno.21516 This issue

Research Paper

pH-Sensitive Nano-Complexes Overcome Drug Resistance and Inhibit Metastasis of Breast Cancer by Silencing Akt Expression

Jieying Yin1,2*, Tianqun Lang1,3*, Dongmei Cun2, Zhong Zheng1, Yan Huang1,2, Qi Yin1✉, Haijun Yu1, Yaping Li1✉

1. State Key Laboratory of Drug Research & Center of Pharmaceutics, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China;
2. School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China;
3. University of Chinese Academy of Sciences, Beijing 100049, China.
* These authors contributed equally to this work.

This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY-NC) license ( See for full terms and conditions.
Yin J, Lang T, Cun D, Zheng Z, Huang Y, Yin Q, Yu H, Li Y. pH-Sensitive Nano-Complexes Overcome Drug Resistance and Inhibit Metastasis of Breast Cancer by Silencing Akt Expression. Theranostics 2017; 7(17):4204-4216. doi:10.7150/thno.21516. Available from

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Graphic abstract

The therapy of breast cancer is encumbered by drug resistance and metastasis, which can be due to a defective PI3K/AKT/mTOR signaling pathway. This study was aimed at improving the anti-cancer effect of the chemotherapeutic agent paclitaxel (PTX) on the drug resistant and metastatic breast cancer by co-delivering PTX and a siRNA, siAkt, directed at silencing the Akt expression.

Methods: The pH-sensitive amphiphilic polymer, poly [(1,4-butanediol)-diacrylate-β-N, N-diisopropylethylenediamine]-polyethyleneimine (BDP) was synthesized. The PTX-loaded BDP micelle/siAkt nano-complex (PMA) was prepared and characterized. The cellular uptake, cytotoxicity, RNA interference efficiency, biodistribution, pharmacokinetics, pharmacodynamics, and biocompatibility of PMA in the murine metastatic breast cancer 4T1 cells and the 4T1 tumor-bearing mice were evaluated.

Results: PMA was stable at the neutral as well as tumor extracellular pH and released the drugs in the intra-endo/lysosome acidic environment. In 4T1 cells, the RNA interference against the Akt gene down-regulated the expression of Akt and P-glycoprotein and up-regulated the expression of Caspase-3. The down-regulated P-gp inhibits the efflux of PTX thereby increasing its intracellular concentration, improving the cytotoxicity, and inhibiting the migration and invasion of 4T1 cells. In the 4T1 tumor-bearing mice, co-delivery of PTX and siAkt by PMA achieved a tumor inhibiting rate of 94.1% and suppressed 96.8% lung metastases. PMA did not cause pathological lesions in normal organs.

Conclusion: PMA, by virtue of overcoming drug resistance and simultaneously restraining lung metastasis, might be an efficient drug delivery system for the therapy of breast cancer.