title: Effects and Mechanisms of Metformin on the Proliferation of Esophageal Cancer CellsIn VitroandIn Vivo.
abstract: OBJECTIVE
  The purpose of this study was to observe the effects of metformin on human esophageal cancer cell and to investigate its possible mechanisms.
  
  
  METHODS
  Cell viability was detected by using a Cell Counting Kit-8, while cell cycle and apoptosis were assessed by flow cytometry and western blot was used to measure the expression of the related proteins. RNAi was used to knockout pyruvate kinase muscle isozyme 2 (PKM2). An Eca109 tumor model was established to evaluate the antitumor effectin vivo. Immunohistochemistry was determined based on the expression of PKM2 and Bim in tumor tissues. Tunnel was used to assess tumor cell apoptosis.
  
  
  RESULTS
  Esophageal cancer cells viability was reduced after metformin treatment. The cell cycle was arrested in the G0/G1 phase, apoptosis was induced, caspase 3 was activated, caspase 9 was downregulated, and the pro-apoptotic protein Bim increased. Further study revealed that metformin could suppress the expression of insulin-like growth factor 1 receptor and its downstream proteins, phosphoinositide 3-kinase (PI3K), protein kinase B (AKT/PKB), phosphorylation of AKT (pAKT), mammalian target of rapamycin (mTOR), p70S6K, and PKM2. Insulin-like growth factor 1 partly reversed metfromin-induced apoptosis and attenuated the repression effect of metfomin to PI3K, pAKT, and PKM2. Knockout PKM2 resulted in the activation of caspase 3, down-regulation of caspase 9, and increased expression of Bim. In the Eca109 xenograft model, metformin significantly reduced tumor growth. Furthermore, we found that metformin treatment increased the rate of apoptosis, down-regulation of PKM2, and up-regulation of Bim in tumor tissues.
  
  
  CONCLUSIONS
  Metformin restrained esophageal cancer cell proliferation partly by suppressing the PI3K/AKT/mTOR pathway.
authors.affiliation: Department of Biochemistry, North of Sichuan Medical University, Nanchong, China.
authors.forename: Jian-Cai
authors.initials: JC
authors.lastname: Tang
authors.affiliation: School of Basic Medical Sciences, North of Sichuan Medical University, Nanchong, China.
authors.forename: Rui
authors.initials: R
authors.lastname: An
authors.affiliation: School of Basic Medical Sciences, North of Sichuan Medical University, Nanchong, China.
authors.forename: Yi-Qing
authors.initials: YQ
authors.lastname: Jiang
authors.affiliation: Pathogenic Biology and Immunology Experiment Teaching Center, North of Sichuan Medical University, Nanchong, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002352:Carrier Proteins / Q000235:genetics; D059447:Cell Cycle Checkpoints / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004195:Disease Models, Animal; D004938:Esophageal Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000235:genetics; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D013002:Somatomedins / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D013963:Thyroid Hormones / Q000235:genetics; D023041:Xenograft Model Antitumor Assays; D000097810:Thyroid Hormone-Binding Proteins
chemical_list: D000970:Antineoplastic Agents; D002352:Carrier Proteins; D008565:Membrane Proteins; D008687:Metformin; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D013002:Somatomedins; D058570:TOR Serine-Threonine Kinases; D013963:Thyroid Hormones; D000097810:Thyroid Hormone-Binding Proteins
keywords: Apoptosis; Bcl-2-interacting mediator of cell death; Cell proliferation; Metformin; PKM2 protein