title: Small interfering RNA targeting the subunit ATP6L of proton pump V-ATPase overcomes chemoresistance of breast cancer cells.
abstract: One of the mechanisms of multiple drug resistance (MDR) is inappropriate sequestration of basic chemotherapeutic agents in acidic endo-lysosomes of cells. The protonation, sequestration, and secretion (PSS) model indicates that drug distribution can be affected by intracellular pH such as lysosomal pH. The vacuolar-H(+)-ATPase (V-ATPase) plays an important role in regulation of intracellular pH by pumping protons into acidic endosomes via an ATP-driven process. In this study, ATP6L, the 16kDa subunit of V-ATPase, was knocked-down by anti-ATP6L small interfering RNA (siRNA) to study the effect on chemosensitivity in the human drug-resistant breast cancer cells MCF-7/ADR. Introduction of anti-ATP6L small interfering RNA duplex into drug-resistant cancer cells significantly inhibited the expression of ATP6L mRNA and protein, as detected by qRT-PCR and Western blot. Inhibition of ATP6L expression by siRNA in MCF-7/ADR sensitized the cells to the cytotoxicity of basic chemotherapeutic agents like doxorobicin, 5-fluorourocil and vincristine. This effect was mediated by a significant increase in lysosomal pH and retention of anticancer drugs into nuclei of cells. These results support the role of tumor acidity in resistance to chemotherapy and provide a rationale for the use of tumor pH modifier agents as coadjuvants in novel anticancer therapies.
authors.affiliation: National Laboratory for Oncogenes and Related Genes, Cancer Institute, Shanghai Jiao Tong University School of Medicine, No. 25/2200 Xietu Road, Shanghai 200032, PR China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: You
authors.forename: Jie
authors.initials: J
authors.lastname: Jin
authors.forename: Huiqun
authors.initials: H
authors.lastname: Shu
authors.forename: Bin
authors.initials: B
authors.lastname: Yu
authors.forename: Angelo
authors.initials: A
authors.lastname: De Milito
authors.forename: Francesco
authors.initials: F
authors.lastname: Lozupone
authors.forename: Yun
authors.initials: Y
authors.lastname: Deng
authors.forename: Ning
authors.initials: N
authors.lastname: Tang
authors.forename: Genfu
authors.initials: G
authors.lastname: Yao
authors.forename: Stefano
authors.initials: S
authors.lastname: Fais
authors.forename: Jianren
authors.initials: J
authors.lastname: Gu
authors.forename: Wenxin
authors.initials: W
authors.lastname: Qin
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000201:enzymology*; D002453:Cell Cycle; D045744:Cell Line, Tumor; D002470:Cell Survival; D019008:Drug Resistance, Neoplasm; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008247:Lysosomes / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000502:physiology*
chemical_list: C541389:ATP6V0C protein, human; D000970:Antineoplastic Agents; D034741:RNA, Small Interfering; D025262:Vacuolar Proton-Translocating ATPases