Reversion of multidrug resistance by a pH-responsive cyclodextrin-derived nanomedicine in drug resistant cancer cells.

Multidrug resistance (MDR) is one of the major problems responsible for inefficiency of cancer chemotherapy. Currently, there is still unmet demand for innovative strategies as well as effective and safe sensitizers to overcome MDR. In this study, we developed a nanosensitizer based on a pH-responsive nanoparticle (NP) derived from acetalated α-cyclodextrin (Ac-aCD). This pH-responsive NP could be effectively endocytosed by MDR cancer cells, and intracellularly transported by endolysosomal compartments. Ac-aCD NP was able to dramatically potentiate the activity of anticancer drugs including paclitaxel, docetaxel, cis-diamminedichloroplatinum, camptothecin, and doxorubicin. This sensitizing capability of Ac-aCD NP on MDR cells was resulted from the combined effects of decreased Pgp expression, attenuated Pgp ATPase activity, and the reduced intracellular ATP level. Ac-aCD NP exerted these diverse biological functions by intracellularly released α-cyclodextrin molecules, which were produced due to hydrolysis of Ac-aCD in acidic subcellular organelle. On the other hand, treatment with Ac-aCD NP showed no significant effects on the integrity of the plasma membrane, cytoskeleton, cell cycle, mitochondrial membrane potential, and apoptosis. These findings suggest that this pH-responsive NP has great potential for effective therapy of resistant cancers by combining with chemotherapeutic agents. It may also serve as a pharmacologically active nanocarrier for intracellular delivery of a plethora of antitumor drugs.