title: Effects of metformin on breast cancer cell proliferation, the AMPK pathway and the cell cycle.
abstract: OBJECTIVE
  The aim of this study was to compare the effects and mechanisms of action of metformin on estrogen receptor (ER)-positive and ER-negative breast cancer cell lines.
  
  
  METHODS
  The anti-proliferative effects of metformin, and of the direct activator of adenosine monophosphate-activated protein kinase (AMPK), A-769662, on MCF-7 (ER-positive) and MDA-MB-231 (ER-negative) breast cancer cell lines were evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, a yellow tetrazole) assays. Fluorescence-activated cell sorting was also used to examine the effect of metformin on the cell cycle. Finally, phosphorylation of the metformin target AMPK, and of its potential downstream targets including acetyl-CoA carboxylase (ACC), p53, p70-S6K and Raptor, was examined using immunoblotting.
  
  
  RESULTS
  Metformin and A-769662 caused significant, concentration-dependent suppression of cell proliferation with G1 cell cycle arrest in both MCF-7 and MDA-MB-231 cells. The proliferation suppression effect was more profound in MCF-7 cells. A concentration-dependent phosphorylation of AMPK was detected following metformin treatment, as was phosphorylation of ACC in both cell lines, but not p53, p70-S6k or Raptor.
  
  
  CONCLUSIONS
  Metformin acts as a growth inhibitor in both ER-positive and ER-negative breast cancer cells in vitro, and arrests cells in G1 phase, particularly in the ER-positive MCF-7 cells. The effect is likely to be mediated by AMPK activation, in part by inhibition of fatty acid synthesis via ACC phosphorylation.
authors: Academic Unit of Surgical Oncology, Department of Oncology, The Medical School, University of Sheffield, Sheffield, S10 2RX, UK, s.hadad@sheffield.ac.uk.
authors: S M
authors: SM
authors: Hadad
authors: D G
authors: DG
authors: Hardie
authors: V
authors: V
authors: Appleyard
authors: A M
authors: AM
authors: Thompson
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology*; D002453:Cell Cycle / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002469:Cell Separation; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007150:Immunohistochemistry; D008687:Metformin / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D007004:Hypoglycemic Agents; D008687:Metformin; D055372:AMP-Activated Protein Kinases