title: AMPK/mTOR-mediated inhibition of survivin partly contributes to metformin-induced apoptosis in human gastric cancer cell.
abstract: Recent studies demonstrated that metformin exerts anti-neoplastic effect in a spectrum of malignancies. However, the mechanism whereby metformin affects various cancers, including gastric cancer, is poorly elucidated. Considering apoptosis plays critical role in tumorigenesis, we, in the present study, investigated the in vitro apoptotic effect of metformin on human gastric cancer cell and the underlying mechanism. Three differently-differentiated gastric cancer cell lines, MKN-28, SGC-7901 and BGC-823, along with one noncancerous gastric cell line GES-1 were used. We found that metformin treatment selectively induces apoptosis in the 3 cancer cell lines, but not the noncancerous one, as confirmed by flow cytometry, Caspase-Glo assay and western blotting against PARP and cleaved caspase 3. Moreover, the apoptotic effect of metformin seems to correlate negatively with the differentiation degree of gastric cancer. Metformin-induced apoptosis may be partially mediated through inhibition of anti-apoptotic survivin. Additionally, AMPK and mTOR, 2 important regulatory molecules responsible for metformin action, were investigated for their possible involvements in metformin-induced apoptosis of gastric cancer cell. AMPK knockdown by siRNA restores metformin-inhibited survivin expression and partially abolishes metformin-induced apoptosis. Similarly, forced overexpression of mTOR downstream effector p70S6K1 relieves metformin-induced inhibition of survivin and partly attenuates metformin-induced apoptosis. More importantly, survivin overexpression alleviates metformin-induced apoptosis. Xenograft nude mouse experiment also confirmed that AMPK/mTOR-mediated decrease of suvivin is in vivo implicated in metformin-induced apoptosis. Taken together, these evidences suggest that AMPK/mTOR-mediated inhibition of survivin may partly contribute to metformin-induced apoptosis of gastric cancer cell.
authors.affiliation: a Department of General Surgery ; The Affiliated Shanghai Shuguang Hospital of Shanghai University of Traditional Chinese Medicine , Shanghai , China.
authors.forename: Gang
authors.initials: G
authors.lastname: Han
authors.forename: Hangjun
authors.initials: H
authors.lastname: Gong
authors.forename: Yidong
authors.initials: Y
authors.lastname: Wang
authors.forename: Shaowen
authors.initials: S
authors.lastname: Guo
authors.forename: Kun
authors.initials: K
authors.lastname: Liu
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D004195:Disease Models, Animal; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism*; D008297:Male; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D010766:Phosphorylation; D034622:RNA Interference; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000077022:Survivin; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
chemical_list: D000970:Antineoplastic Agents; C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; D000077022:Survivin; D008687:Metformin; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases
keywords: AMPK; AMPK, Adenosine Monophosphate Activated Protein Kinase; PARP, Poly Adenosine Diphosphate Ribose Polymerase; apoptosis; gastric cancer; mTOR; mTOR, Mammalian Target of Rapamycin; metformin; siRNA, Small interfering Ribonucleic Acid; survivin