Oral Nanomedicine Based on Multicomponent Microemulsions for Drug-Resistant Breast Cancer Treatment

The aim of this study is to demonstrate the enhanced therapeutic efficacy of anticancer drugs on drug-resistant breast cancer using multicomponent microemulsions (ECG-MEs) as an oral delivery system. The etoposide-loaded ECG-MEs were composed of coix seed oil and ginsenoside Rh2 (G-Rh2), both of which possess not only the synergistic antitumor effect with etoposide, but also have excipient-like properties. Orally administrated ECG-MEs were demonstrated to be able to accumulate at the tumor site following crossing the intestines as intact vehicles into the blood circulation. The spatiotemporal controlled release characteristics of ECG-MEs brought about the efficient P-gp inhibition by the initially released G-Rh2 and the increased intracellular accumulation of the sequentially released etoposide. The combination antitumor activity of etoposide, G-Rh2 and coix seed oil using ECG-MEs was verified on the xenograft drug-resistant breast tumor mouse models. In addition, the safety evaluation studies indicated that treatment with ECG-MEs did not cause any significant toxicity in vivo. These findings suggest that ECG-MEs as an oral formulation may offer a promising strategy to treat the drug-resistant breast cancer.