Coencapsulated Doxorubicin and Bromotetrandrine Lipid Nanoemulsions in Reversing Multidrug Resistance in Breast Cancer in Vitro and in Vivo

Multidrug resistance has remained a major cause of treatment failure in chemotherapy due to the presence of P-glycoproteins (P-gp) that actively pump drugs from inside the cell to the outside. P-gp inhibitors were developed and coadministered with chemotherapeutic drugs to overcome the effect of efflux pumps thus enhancing the chemosensitivity of therapeutics. Our study aimed at developing a lipid nanoemulsion system for the coencapsulation of doxorubicin (DOX) and bromotetrandrine (W198) to reverse multidrug resistance (MDR) in breast cancer. W198 was a potent P-gp inhibitor, and DOX was selected as a model compound which is a common substrate for P-gp. Coencapsulated DOX and W198 lipid nanoemulsions (DOX/W198-LNs) displayed significantly enhanced cytotoxicity in DOX-resistant human breast cancer cells (MCF-7/ADR) compared with DOX loaded lipid nanoemulsions (DOX-LNs) (p < 0.05), which is due to the enhanced intracellular uptake of DOX in MCF-7/ADR cells. The biodistribution study was performed using a nude mice xenograft model, which demonstrates enhanced tumor uptake of DOX in the DOX/W198-LN treated group. Compared with DOX solution, DOX/W198-LNs showed reduced cardiac toxicity and gastrointestinal injury in rats. Taken together, DOX/W198-LNs represent a promising formulation for overcoming MDR in breast cancer.