title: HMGB1-mediated autophagy promotes docetaxel resistance in human lung adenocarcinoma.
abstract: BACKGROUND
  Docetaxel resistance remains a major obstacle in the treatment of non-small cell lung cancer (NSCLC). High-mobility group box 1 (HMGB1) has been shown to promote autophagy protection in response to antitumor therapy, but the exact molecular mechanism underlying HMGB1-mediated autophagy has not been clearly defined.
  
  
  METHODS
  Lung adenocarcinoma (LAD) cells were transfected with pcDNA3.1-HMGB1 or HMGB1 shRNA, followed by docetaxel treatment. Cell viability and proliferation were tested by MTT assay and colony formation assay, respectively. Annexin V flow cytometric analysis and western blot analysis of activated caspase3 and cleaved PARP were used to evaluate apoptosis, while immunofluorescence microscopy and transmission electron microscopy were applied to assess autophagy activity. The formation of the Beclin-1-PI3K-III complex was examined by immunoprecipitation analysis. NOD/SCID mice were inoculated with docetaxel-resistant SPC-A1/DTX cells transfected with control or HMGB1 shRNA.
  
  
  RESULTS
  HMGB1 translocated from the nucleus to the cytoplasm in LAD cells exposed to docetaxel and acted as a positive regulator of autophagy, which inhibited apoptosis and increased drug resistance. Suppression of HMGB1 restored the sensitivity of LAD cells to docetaxel both in vivo and in vitro. Mechanistic investigation revealed that HMGB1 promoted the formation of the Beclin-1-PI3K-III complex through activating the mitogen-activated protein kinase (MEK)-extracellular signal-regulated kinase (ERK) signaling pathway, thereby regulating autophagosome formation.
  
  
  CONCLUSIONS
  Our results demonstrated that HMGB1-regulated autophagy is a significant contributor to docetaxel resistance in LAD cells. Suppression of HMGB1 or limiting HMGB1 cytosolic translocation diminished autophagic protection in response to docetaxel in LAD cells.
authors.forename: Banzhou
authors.initials: B
authors.lastname: Pan
authors.forename: Dongqin
authors.initials: D
authors.lastname: Chen
authors.forename: Jiayuan
authors.initials: J
authors.lastname: Huang
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.forename: Bing
authors.initials: B
authors.lastname: Feng
authors.affiliation: Department of Medical Oncology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing 210002, P,R, China. songhaizhu@163.com.
authors.forename: Haizhu
authors.initials: H
authors.lastname: Song
authors.forename: Longbang
authors.initials: L
authors.lastname: Chen
mesh_terms: D000230:Adenocarcinoma / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology* / Q000648:ultrastructure; D000077192:Adenocarcinoma of Lung; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects*; D000071186:Beclin-1; D045744:Cell Line, Tumor; D019610:Cytoprotection / Q000187:drug effects; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D000077143:Docetaxel; D015536:Down-Regulation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D055785:Gene Knockdown Techniques; D024243:HMGB1 Protein / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology* / Q000648:ultrastructure; D020935:MAP Kinase Signaling System / Q000187:drug effects; D000076222:Mechanistic Target of Rapamycin Complex 1; D008565:Membrane Proteins / Q000378:metabolism; D016688:Mice, Inbred NOD; D016513:Mice, SCID; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D021381:Protein Transport / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D043823:Taxoids / Q000494:pharmacology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; D000077143:Docetaxel; D024243:HMGB1 Protein; D000076222:Mechanistic Target of Rapamycin Complex 1; D008565:Membrane Proteins; D046912:Multiprotein Complexes; D019869:Phosphatidylinositol 3-Kinases; D058570:TOR Serine-Threonine Kinases; D043823:Taxoids; C491997:BECN1 protein, human