Metformin Inhibits TGF-β1-Induced Epithelial-to-Mesenchymal Transition via PKM2 Relative-mTOR/p70s6k Signaling Pathway in Cervical Carcinoma Cells

Int J Mol Sci. 2016 Nov 30;17(12):2000. doi: 10.3390/ijms17122000.

Abstract

Background: Epithelial-to-mesenchymal transition (EMT) plays a prominent role in tumorigenesis. Metformin exerts antitumorigenic effects in various cancers. This study investigated the mechanisms of metformin in TGF-β1-induced Epithelial-to-mesenchymal transition (EMT) in cervical carcinoma cells.

Methods: cells were cultured with 10 ng/mL TGF-β1 to induce EMT and treated with or without metformin. Cell viability was evaluated by CCK-8 (Cell Counting Kit 8, CCK-8) assay; apoptosis were analyzed by flow cytometry; cell migration was evaluated by wound-healing assay. Western blotting was performed to detect E-cadherin, vimentin, signal transducer and activator of transcription 3 (STAT3), snail family transcriptional repressor 2 (SNAIL2), phosphorylation of p70s6k (p-p70s6k) and -Pyruvate kinase M2 (PKM2) Results: TGF-β1 promoted proliferation and migration, and it attenuated apoptosis compared with cells treated with metformin with or without TGF-β1 in cervical carcinoma cells. Moreover, metformin partially abolished TGF-β1-induced EMT cell proliferation and reversed TGF-β1-induced EMT. In addition, the anti-EMT effects of metformin could be partially in accord with rapamycin, a specific mTOR inhibitor. Metformin decreased the p-p70s6k expression and the blockade of mTOR/p70s6k signaling decreased PKM2 expression.

Conclusion: Metformin abolishes TGF-β1-induced EMT in cervical carcinoma cells by inhibiting mTOR/p70s6k signaling to down-regulate PKM2 expression. Our study provides a novel mechanistic insight into the anti-tumor effects of metformin.

Keywords: PKM2; epithelial-mesenchymal transition; mammalian target of rapamycin; metformin.

MeSH terms

  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Movement / drug effects
  • Cell Proliferation / drug effects
  • Cell Survival / drug effects
  • Epithelial-Mesenchymal Transition / drug effects*
  • Female
  • Humans
  • Hypoglycemic Agents / pharmacology*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Metformin / pharmacology*
  • Ribosomal Protein S6 Kinases, 70-kDa / genetics
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism*
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism*
  • Thyroid Hormones / genetics
  • Thyroid Hormones / metabolism*
  • Transforming Growth Factor beta1 / pharmacology*
  • Uterine Cervical Neoplasms

Substances

  • Carrier Proteins
  • Hypoglycemic Agents
  • Membrane Proteins
  • Thyroid Hormones
  • Transforming Growth Factor beta1
  • thyroid hormone-binding proteins
  • Metformin
  • MTOR protein, human
  • Ribosomal Protein S6 Kinases, 70-kDa
  • TOR Serine-Threonine Kinases