AIM: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.CONCLUSION: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. AIM: 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. 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) 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. CONCLUSION: 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. Heart, both caspase-8 and-9-initiated apoptotic signaling pathways to metformin-induced apoptosis in pancreatic cell lines.