Suppression of AGR2 in a TGF-β-induced Smad regulatory pathway mediates epithelial-mesenchymal transition

BMC Cancer. 2017 Aug 15;17(1):546. doi: 10.1186/s12885-017-3537-5.

Abstract

Background: During cancer progression, epithelial cancer cells can be reprogrammed into mesenchymal-like cells with increased migratory potential through the process of epithelial-mesenchymal transition (EMT), representing an essential step of tumor progression towards metastatic state. AGR2 protein was shown to regulate several cancer-associated processes including cellular proliferation, survival and drug resistance.

Methods: The expression of AGR2 was analyzed in cancer cell lines exposed to TGF-β alone or to combined treatment with TGF-β and the Erk1/2 inhibitor PD98059 or the TGF-β receptor specific inhibitor SB431542. The impact of AGR2 silencing by specific siRNAs or CRISPR/Cas9 technology on EMT was investigated by western blot analysis, quantitative PCR, immunofluorescence analysis, real-time invasion assay and adhesion assay.

Results: Induction of EMT was associated with decreased AGR2 along with changes in cellular morphology, actin reorganization, inhibition of E-cadherin and induction of the mesenchymal markers vimentin and N-cadherin in various cancer cell lines. Conversely, induction of AGR2 caused reversion of the mesenchymal phenotype back to the epithelial phenotype and re-acquisition of epithelial markers. Activated Smad and Erk signaling cascades were identified as mutually complementary pathways responsible for TGF-β-mediated inhibition of AGR2.

Conclusion: Taken together our results highlight a crucial role for AGR2 in maintaining the epithelial phenotype by preventing the activation of key factors involved in the process of EMT.

Keywords: AGR2; E-cadherin; EMT; Metastasis; TGF-β; Vimentin.

MeSH terms

  • Cadherins / metabolism
  • Cell Adhesion / genetics
  • Cell Line, Tumor
  • Cell Movement / genetics
  • Epithelial-Mesenchymal Transition / drug effects*
  • Epithelial-Mesenchymal Transition / genetics*
  • Gene Expression Regulation, Neoplastic / drug effects
  • Gene Knockdown Techniques
  • Humans
  • Mucoproteins
  • Oncogene Proteins
  • Proteins / genetics*
  • Signal Transduction / drug effects*
  • Smad Proteins / metabolism*
  • Transforming Growth Factor beta / pharmacology*
  • Vimentin / metabolism

Substances

  • AGR2 protein, human
  • Cadherins
  • Mucoproteins
  • Oncogene Proteins
  • Proteins
  • Smad Proteins
  • Transforming Growth Factor beta
  • Vimentin