FoxO3a inhibiting expression of EPS8 to prevent progression of NSCLC: A new negative loop of EGFR signaling

EBioMedicine. 2019 Feb;40:198-209. doi: 10.1016/j.ebiom.2019.01.053. Epub 2019 Feb 7.

Abstract

Background: The resistance to EGF receptor (EGFR) tyrosine kinase inhibitors (TKI) is a major challenge in the treatment of non-small cell lung cancer (NSCLC). Understanding the molecular mechanisms behind resistance is therefore an important issue. Here we assessed the role of EGFR pathway substrate 8 (EPS8) and Forkhead box O 3a (FoxO3a) as potentially valuable targets in the resistance of NSCLC .

Methods: The expression levels of EPS8 and FoxO3a in patients with NSCLC (n = 75) were examined by immunohistochemistry staining, while in cells were detected by qPCR and western blot. The effects of EPS8 and FoxO3a on resistance, migration and invasion, cell cycle arrest were detected by MTT, transwell and flow cytometry, respectively. Chromatin immunoprecipitation and luciferase reporter assays were performed to determine the mechanisms of EPS8 expression and FoxO3a regulation.

Findings: We observed that the expression of EPS8 inversely correlated with FoxO3a in NSCLC cell lines and NSCLC patients. FoxO3a levels were significantly decreased in tumor tissues compared with para-carcinoma tissues, while EPS8 is opposite. Besides, they play reverse roles in the resistance to gefitinib, the migration and invasion abilities, the cell cycle arrest in vitro and the tumor growth in vivo. Mechanistically, FoxO3a inhibits EPS8 levels by directly binding its gene promoter and they form a negative loop in EGFR pathway.

Interpretation: Targeting FoxO3a and EPS8 in EGFR signaling pathway prevents the progression of NSCLC, which implied that the negative loop they formed could served as a therapeutic target for overcoming resistance in NSCLC.

Funds: National Natural Science Foundation of China, Science and Technology Project of Henan, Outstanding Young Talent Research Fund of Zhengzhou University and the National Scholarship Fund.

Keywords: EGFR pathway substrate 8 (EPS8); Epidermal growth factor receptor (EGFR); Forkhead box O 3a (FoxO3a); Gefitinib; Non-small cell lung cancer (NSCLC); Tumor resistance.

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics*
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Apoptosis / drug effects
  • Carcinoma, Non-Small-Cell Lung / genetics*
  • Carcinoma, Non-Small-Cell Lung / metabolism*
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Cell Cycle / drug effects
  • Cell Cycle Checkpoints / drug effects
  • Cell Cycle Checkpoints / genetics
  • Cell Line, Tumor
  • Cell Movement
  • Cell Proliferation
  • Disease Models, Animal
  • Drug Resistance, Neoplasm / genetics
  • ErbB Receptors / metabolism
  • Female
  • Forkhead Box Protein O3 / metabolism*
  • Gefitinib / pharmacology
  • Gene Expression Regulation, Neoplastic*
  • Genes, Reporter
  • Heterografts
  • Humans
  • Immunohistochemistry
  • Lung Neoplasms / genetics*
  • Lung Neoplasms / metabolism*
  • Lung Neoplasms / pathology
  • Mice
  • Models, Biological
  • Phosphorylation
  • Protein Kinase Inhibitors / pharmacology
  • Signal Transduction / drug effects

Substances

  • Adaptor Proteins, Signal Transducing
  • EPS8 protein, human
  • FOXO3 protein, human
  • Forkhead Box Protein O3
  • Protein Kinase Inhibitors
  • ErbB Receptors
  • Gefitinib