title: Metformin inhibits estrogen-dependent endometrial cancer cell growth by activating the AMPK-FOXO1 signal pathway.
abstract: Metformin is an oral biguanide commonly used for treating type II diabetes and has recently been reported to possess antiproliferative properties that can be exploited for the prevention and treatment of a variety of cancers. The mechanisms underlying this effect have not been fully elucidated. Our study shows a marked loss of AMP-activated protein kinase (AMPK) phosphorylation and nuclear human Forkhead box O1 (FOXO1) protein in estrogen-dependent endometrial cancer (EC) tumors compared to normal control endometrium. Metformin treatment suppressed EC cell growth in a time-dependent manner in vitro; this effect was cancelled by cotreatment with an AMPK inhibitor, compound C. Metformin decreased FOXO1 phosphorylation and increased FOXO1 nuclear localization in Ishikawa and HEC-1B cells, with non-significant increase in FOXO1 mRNA expression. Moreover, compound C blocked the metformin-induced changes of FOXO1 and its phosphorylation protein, suggesting that metformin upregulated FOXO1 activity by AMPK activation. Similar results were obtained after treatment with insulin. In addition, transfection with siRNA for FOXO1 cancelled metformin-inhibited cell growth, indicating that FOXO1 mediated metformin to inhibit EC cell proliferation. A xenograft mouse model further revealed that metformin suppressed HEC-1B tumor growth, accompanied by downregulated ki-67 and upregulated AMPK phosphorylation and nuclear FOXO1 protein. Taken together, these data provide a novel mechanism of antineoplastic effect for metformin through the regulation of FOXO1, and suggest that the AMPK-FOXO1 pathway may be a therapeutic target to the development of new antineoplastic drugs.
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Jingfang
authors.initials: J
authors.lastname: Zou
authors.affiliation: Departments of Pathology, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Liangli
authors.initials: L
authors.lastname: Hong
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Chaohuan
authors.initials: C
authors.lastname: Luo
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Li
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Yuzhang
authors.initials: Y
authors.lastname: Zhu
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Tianliang
authors.initials: T
authors.lastname: Huang
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Yongneng
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Huier
authors.initials: H
authors.lastname: Yuan
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Yaqiu
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Tengfei
authors.initials: T
authors.lastname: Wen
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Wanling
authors.initials: W
authors.lastname: Zhuang
authors.affiliation: The Laboratory of Molecular Cardiology, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Bozhi
authors.initials: B
authors.lastname: Cai
authors.affiliation: The Laboratory of Molecular Cardiology, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Departments of Pathology, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Jiexiong
authors.initials: J
authors.lastname: Huang
authors.affiliation: Departments of Internal Medicine, The First Affiliated Hospital of Shantou University Medical College, Shantou, China.
authors.forename: Jidong
authors.initials: J
authors.lastname: Cheng
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000818:Animals; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004195:Disease Models, Animal; D016889:Endometrial Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D004789:Enzyme Activation; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D000071161:Forkhead Box Protein O1 / Q000378:metabolism*; D006801:Humans; D008687:Metformin / Q000494:pharmacology*; D051379:Mice; D008875:Middle Aged; D010766:Phosphorylation; D015398:Signal Transduction / Q000187:drug effects*; D023041:Xenograft Model Antitumor Assays
chemical_list: D004967:Estrogens; C085126:FOXO1 protein, human; D000071161:Forkhead Box Protein O1; D008687:Metformin; D055372:AMP-Activated Protein Kinases
keywords: 
  AMPK
  ; FOXO1; estrogen-dependent endometrial cancer; metformin; proliferation