Mammalian Target of Rapamycin (mTOR) Regulates Transforming Growth Factor-β1 (TGF-β1)-Induced Epithelial-Mesenchymal Transition via Decreased Pyruvate Kinase M2 (PKM2) Expression in Cervical Cancer Cells

Med Sci Monit. 2017 Apr 27:23:2017-2028. doi: 10.12659/msm.901542.

Abstract

BACKGROUND Epithelial-mesenchymal transition (EMT) plays an important role in cancer tumorigenesis. Transforming growth factor β1 (TGF-β1) can induced EMT, which could increase tumor migration and invasion. Moreover, recent studies have been proven that mammalian target of rapamycin (mTOR) is a critical regulator of EMT. We investigated the mechanisms of mTOR in transforming growth factor β1 (TGF-β1)-induced EMT in cervical cancer cells. MATERIAL AND METHODS HeLa and SiHa cells were treated with 10 ng/ml TGF-β1 to induce EMT. Then, they were treated with or without rapamycin. CCK8 assay was performed to determine cell proliferation. Cell migration was detected by wound-healing assay; apoptosis was analyzed by flow cytometry; mTOR inhibitors inhibited mTOR pathway to assess the expression of E-cadherin, Vimentin STAT3, Snail2, p-p70s6k, and PKM2 expression. RESULTS TGF-β1 promoted proliferation and migration, and attenuated apoptosis in cervical carcinoma cells. Rapamycin abolished TGF-β1-induced EMT cell proliferation and migration and reversed TGF-β1-induced EMT. E-cadherin were suppressed, whereas Vimentin and PKM2 were increased in HeLa and SiHa cells after stimulation with TGF-β1. Moreover, mTOR was activated in the process of TGF-β1-induced EMT. Rapamycin inhibited the phosphorylation of p70s6k. Furthermore, inhibition of the mTOR pathway decreased PKM2 expression. CONCLUSIONS Inhibition of the mTOR pathway abolished TGF-β1-induced EMT and reduced mTOR/p70s6k signaling, which downregulated PKM2 expression. Our results provide novel mechanistic insight into the anti-tumor effects of inhibition of mTOR.

MeSH terms

  • Apoptosis / drug effects
  • Cadherins / metabolism
  • Carrier Proteins / biosynthesis
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Line, Tumor
  • Cell Movement / drug effects
  • Cell Proliferation / drug effects
  • Epithelial-Mesenchymal Transition / drug effects*
  • Female
  • HeLa Cells
  • Humans
  • Membrane Proteins / biosynthesis
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Ribosomal Protein S6 Kinases, 70-kDa / metabolism
  • Signal Transduction / drug effects
  • Sirolimus / pharmacology
  • TOR Serine-Threonine Kinases / antagonists & inhibitors
  • TOR Serine-Threonine Kinases / genetics
  • TOR Serine-Threonine Kinases / metabolism*
  • Thyroid Hormone-Binding Proteins
  • Thyroid Hormones / biosynthesis
  • Thyroid Hormones / genetics
  • Thyroid Hormones / metabolism*
  • Transforming Growth Factor beta1 / pharmacology*
  • Uterine Cervical Neoplasms / drug therapy
  • Uterine Cervical Neoplasms / metabolism*
  • Uterine Cervical Neoplasms / pathology

Substances

  • Cadherins
  • Carrier Proteins
  • Membrane Proteins
  • Thyroid Hormones
  • Transforming Growth Factor beta1
  • MTOR protein, human
  • Ribosomal Protein S6 Kinases, 70-kDa
  • TOR Serine-Threonine Kinases
  • Sirolimus