title: [Mechanism underlying pancreatic cancer cell resistance to mTOR inhibitor RAD001 via c-Raf/ERK1/2 activation].
abstract: OBJECTIVE
  To investigate the molecular mechanism of pancreatic cancer cell resistance to mammalian target of rapamycin (mTOR) inhibitor RAD001, and explore a feasible therapeutic strategy to overcome the resistance in patients with pancreatic cancer.
  
  
  METHODS
  Western blotting was conducted to find out whether RAD001 induced c-Raf-ERK feedback activation and to identify whether RAD001 in combination with c-Raf inhibitor sorafenib could effectively block the feedback activation of c-Raf and downstream proteins. Sulphorhodamine B (SRB) colorimetric assay and colony formation were used to detect the effect of the combination treatment on cell growth and proliferation; finally, the effect on mouse subcutaneous xenografts was examined to confirm the efficacy of the combination treatment in vivo.
  
  
  RESULTS
  RAD001 effectively inhibited the expressions of mTORC1 and its downstream proteins, and induced the feedback activation of c-Raf. Whereas, RAD001 combined with c-Raf inhibitor sorafenib eliminated RAD001-induced activation of c-Raf-ERK pathway and reversed pancreatic cancer cell resistance to RAD001; compared with the RAD001 alone, sorafenib had a synergistical inhibitory effect with RAD001. And the tumor growth inhibitory effect of the combination was also proved in mouse subcutaneous xenografts in vivo.
  
  
  CONCLUSIONS
  RAD001-induced c-Raf-ERK feedback activation contributes to pancreatic cancer cell resistance to RAD001. Targeting of c-Raf may improve the therapeutic efficacy of RAD001 in patients with pancreatic cancer.
authors.affiliation: Department of Hepatobiliary & Pancreas Surgery, First Hospital, Jilin University, Changchun 130021, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Wei
authors.forename: Ping
authors.initials: P
authors.lastname: Zhang
authors.forename: Jun
authors.initials: J
authors.lastname: Qi
authors.forename: Meng
authors.initials: M
authors.lastname: Wang
authors.forename: Guangyi
authors.initials: G
authors.lastname: Wang
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D000068338:Everolimus; D006801:Humans; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D009362:Neoplasm Metastasis; D010190:Pancreatic Neoplasms / Q000473:pathology*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors*
chemical_list: D000068338:Everolimus; D019908:Proto-Oncogene Proteins c-raf; D058570:TOR Serine-Threonine Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020123:Sirolimus