title: Metformin induces apoptosis of pancreatic cancer cells.
abstract: OBJECTIVE
  To assess the role and mechanism of metformin in inducing apoptosis of pancreatic cancer cells.
  
  
  METHODS
  The human pancreatic cancer cell lines ASPC-1, BxPc-3, PANC-1 and SW1990 were exposed to metformin. The inhibition of cell proliferation and colony formation via apoptosis induction and S phase arrest in pancreatic cancer cell lines of metformin was tested.
  
  
  RESULTS
  In each pancreatic cancer cell line tested, metformin inhibited cell proliferation in a dose dependent manner in MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assays). Flow cytometric analysis showed that metformin reduced the number of cells in G1 and increased the percentage of cells in S phase as well as the apoptotic fraction. Enzymelinked immunosorbent assay (ELISA) showed that metformin induced apoptosis in all pancreatic cancer cell lines. In Western blot studies, metformin induced poly-ADP-ribose polymerase (PARP) cleavage (an indicator of caspase activation) in all pancreatic cancer cell lines. The general caspase inhibitor (VAD-fmk) completely abolished metformin-induced PARP cleavage and apoptosis in ASPC-1 BxPc-3 and PANC-1, the caspase-8 specific inhibitor (IETD-fmk) and the caspase-9 specific inhibitor (LEHD-fmk) only partially abrogated metformin-induced apoptosis and PARP cleavage in BxPc-3 and PANC-1 cells. We also observed that metformin treatment dramatically reduced epidermal growth factor receptor (EGFR) and phosphorylated mitogen activated protein kinase (P-MAPK) in both a time- and dose-dependent manner in all cell lines tested.
  
  
  CONCLUSIONS
  Metformin significantly inhibits cell proliferation and apoptosis in all pancreatic cell lines. And the metformin-induced apoptosis is associated with PARP cleavage, activation of caspase-3, -8, and -9 in a time- and dose-dependent manner. Hence, both caspase-8 and -9-initiated apoptotic signaling pathways contribute to metformin-induced apoptosis in pancreatic cell lines.
authors.affiliation: Department of Gastroenterology, Changhai Hospital, Second Military Medical University, Shanghai 200433, China.
authors.forename: Luo-Wei
authors.initials: LW
authors.lastname: Wang
authors.forename: Zhao-Shen
authors.initials: ZS
authors.lastname: Li
authors.forename: Duo-Wu
authors.initials: DW
authors.lastname: Zou
authors.forename: Zhen-Dong
authors.initials: ZD
authors.lastname: Jin
authors.forename: Jun
authors.initials: J
authors.lastname: Gao
authors.forename: Guo-Ming
authors.initials: GM
authors.lastname: Xu
mesh_terms: D000230:Adenocarcinoma / Q000378:metabolism / Q000473:pathology*; D017209:Apoptosis / Q000187:drug effects*; D053181:Caspase 8 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008687:Metformin / Q000494:pharmacology*; D010190:Pancreatic Neoplasms / Q000378:metabolism / Q000473:pathology*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin; C512478:EGFR protein, human; D066246:ErbB Receptors; D053181:Caspase 8; D053453:Caspase 9