title: Synergistic anti-tumour effects of tetrandrine and chloroquine combination therapy in human cancer: a potential antagonistic role for p21.
abstract: OBJECTIVE
  Tetrandrine, a bisbenzylisoquinoline alkaloid isolated from the Chinese medicinal herb Stephaniae tetrandrae, has a long history in Chinese clinical applications to treat diverse diseases. Tetrandrine induced apoptosis or, at low concentrations, autophagy of human hepatocellular carcinoma cells. Here we have tested the effects of inhibitors of autophagy such as chloroquine, on the response to low concentrations of tetrandrine in cancer cells.
  
  
  METHODS
  Cultures of several cancer cell lines, including Huh7, U251, HCT116 and A549 cells, were exposed to tetrandrine, chloroquine or a combination of these compounds. Cell viability and content of reactive oxygen species (ROS) were measured and synergy assessed by calculation of the combination index. Western blot and RT-PCR assays were also used along with fluorescence microscopy and histochemical techniques.
  
  
  RESULTS
  Combinations of tetrandrine and chloroquine were more cytotoxic than the same concentrations used separately and these effects showed synergy. Such effects involved increased ROS generation and were dependent on caspase-3 but independent of Akt activity. Blockade of tetrandrine-induced autophagy with 3-methyladenine or bafilomycin-A1 induced apoptosis in cancer cells. Lack of p21 protein (p21(-/-) HCT116 cells) increased sensitivity to the apoptotic effects of the combination of tetrandrine and chloroquine. In a tumour xenograft model in mice, combined treatment with tetrandrine and chloroquine induced ROS accumulation and cell apoptosis, and decreased tumour growth.
  
  
  CONCLUSIONS
  The combinations of tetrandrine and chloroquine exhibited synergistic anti-tumour activity, in vitro and in vivo. Our results suggest a novel therapeutic strategy for tumour treatment.
authors.affiliation: College of Life Sciences, Wuhan University, Wuhan, China.
authors.forename: Liufeng
authors.initials: L
authors.lastname: Mei
authors.forename: Yicheng
authors.initials: Y
authors.lastname: Chen
authors.forename: Zhimeng
authors.initials: Z
authors.lastname: Wang
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Jiali
authors.initials: J
authors.lastname: Wan
authors.forename: Chunrong
authors.initials: C
authors.lastname: Yu
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.forename: Wenhua
authors.initials: W
authors.lastname: Li
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects; D044182:Benzylisoquinolines / Q000494:pharmacology*; D053148:Caspase 3 / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002738:Chloroquine / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D045325:HCT116 Cells; D006367:HeLa Cells; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008297:Male; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors; D014162:Transfection; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D044182:Benzylisoquinolines; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D017382:Reactive Oxygen Species; C009438:tetrandrine; D002738:Chloroquine; C505407:CASP3 protein, human; D053148:Caspase 3