title: Sensitization of multidrug-resistant malignant cells by liposomes co-encapsulating doxorubicin and chloroquine through autophagic inhibition.
abstract: Adenosine triphosphate (ATP)-binding cassette (ABC) transporters play a key role in the development of multidrug resistance (MDR) in cancer cells. P-glycoprotein (P-gp) and multidrug resistance-associated protein 1 (MRP1) are important proteins in this superfamily which are widely expressed on the membranes of multidrug resistance (MDR) cancer cells. Besides, upregulation of cellular autophagic responses is considered a contributing factor for MDR in cancer cells. We designed a liposome system co-encapsulating a chemotherapeutic drug (doxorubicin hydrochloride, DOX) and a typical autophagy inhibitior (chloroquine phosphate, CQ) at a weight ratio of 1:2 and investigated its drug resistance reversal mechanism. MTT assay showed that the IC50of DOX/CQ co-encapsulated liposome in DOX-resistant human breast cancer cells (MCF7/ADR) was 4.7 ± 0.2 μM, 5.7-fold less than that of free DOX (26.9 ± 1.9  μM), whereas it was 19.5-fold in doxorubicin-resistant human acute myelocytic leukemia cancer cells (HL60/ADR) (DOX/CQ co-encapsulated liposome 1.2 ± 0.1 μM, free DOX 23.4 ± 2.8 μM). The cellular uptake of DOX increased upon addition of free CQ, indicating that CQ may interact with P-gp and MRP1; however, the expressions of P-gp and MRP1 remained unchanged. In contrast, the expression of the autophagy-related protein LC3-II increased remarkably. Therefore, the mechanism of MDR reversal may be closely related to autophagic inhibition. Evaluation of anti-tumor activity was achieved in an MCF-7/ADR multicellular tumor spheroid model and transgenic zebrafish model. DOX/CQ co-encapsulated liposome exerted a better anti-tumor effect in both models than that of liposomal DOX or DOX alone. These findings suggest that encapsulating CQ with DOX in liposomes significantly improves the sensitivity of DOX in DOX-resistant cancer cells.
authors.affiliation: b College of Pharmaceutical Sciences, Zhejiang University , Hangzhou , China.
authors.forename: Menghua
authors.initials: M
authors.lastname: Gao
authors.affiliation: b College of Pharmaceutical Sciences, Zhejiang University , Hangzhou , China.
authors.forename: Yuzhen
authors.initials: Y
authors.lastname: Xu
authors.affiliation: a Ministry of Education (MOE) Key Laboratory of Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University , Hangzhou , China and.
authors.forename: Liyan
authors.initials: L
authors.lastname: Qiu
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002738:Chloroquine / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D008081:Liposomes / Q000737:chemistry; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000473:pathology; D010316:Particle Size; D013329:Structure-Activity Relationship; D013499:Surface Properties; D015027:Zebrafish
chemical_list: D000970:Antineoplastic Agents; D008081:Liposomes; D004317:Doxorubicin; D002738:Chloroquine
keywords: Autophagy; chloroquine; doxorubicin; liposome; multidrug resistance