ABSTRACT
Multidrug resistance (MDR) due to P-glycoprotein (P-gp) overexpression is a major obstacle to successful leukemia chemotherapy. The combination of anticancer chemotherapy with a chemosensitizer of P-gp inhibitor is promising to overcome MDR, generate synergistic effects, and maximize the treatment effect. Herein, we co-encapsulated a chemotherapeutic drug of mitoxantrone (MTO) and a P-gp inhibitor of ß-elemene (ßE) in solid lipid nanoparticles (MTO/ßE-SLNs) for reversing MDR in leukemia. The MTO/ßE-SLNs with about 120 nm particle size possessed good colloidal stability and sustained release behavior. For the cellular uptake study, doxorubicin (DOX) was used as a fluorescence probe to construct SLNs. The results revealed that MTO/ßE-SLNs could be effectively internalized by both K562/DOX and K562 cells through the pathway of caveolate-mediated endocytosis. Under the optimized combination ratio of MTO and ßE, the in vitro cytotoxicity study indicated that MTO/ßE-SLNs showed a better antitumor efficacy in both K562/DOX and K562 cells than other MTO formulations. The enhanced cytotoxicity of MTO/ßE-SLNs was due to the increased cellular uptake and blockage of intracellular ATP production and P-gp efflux by ßE. More importantly, the in vivo studies revealed that MTO/ßE-SLNs could significantly prolong the circulation time and increase plasma half-life of both MTO and ßE, accumulate into tumor and exhibit a much higher anti-leukemia effect with MDR than other MTO formulations. These findings suggest MTO/ßE-SLNs as a potential combined therapeutic strategy for overcoming MDR in leukemia.
