Epidermal growth factor-like domain-containing protein 7 (EGFL7) enhances EGF receptor-AKT signaling, epithelial-mesenchymal transition, and metastasis of gastric cancer cells

PLoS One. 2014 Jun 19;9(6):e99922. doi: 10.1371/journal.pone.0099922. eCollection 2014.

Abstract

Epidermal growth factor-like domain-containing protein 7 (EGFL7) is upregulated in human epithelial tumors and so is a potential biomarker for malignancy. Indeed, previous studies have shown that high EGFL7 expression promotes infiltration and metastasis of gastric carcinoma. The epithelial-mesenchymal transition (EMT) initiates the metastatic cascade and endows cancer cells with invasive and migratory capacity; however, it is not known if EGFL7 promotes metastasis by triggering EMT. We found that EGFL7 was overexpressed in multiple human gastric cancer (GC) cell lines and that overexpression promoted cell invasion and migration as revealed by scratch wound and transwell migration assays. Conversely, shRNA-mediated EGFL7 knockdown reduced invasion and migration. Furthermore, EGFL7-overexpressing cells grew into larger tumors and were more likely to metastasize to the liver compared to underexpressing CG cells following subcutaneous injection in mice. EGFL7 overexpression protected GC cell lines against anoikis, providing a plausible mechanism for this enhanced metastatic capacity. In excised human gastric tumors, expression of EGFL7 was positively correlated with expression levels of the mesenchymal marker vimentin and the EMT-associated transcription repressor Snail, and negatively correlated with expression of the epithelial cell marker E-cadherin. In GC cell lines, EGFL7 knockdown reversed morphological signs of EMT and decreased both vimentin and Snail expression. In addition, EGFL7 overexpression promoted EGF receptor (EGFR) and protein kinase B (AKT) phospho-activation, effects markedly suppressed by the EGFR tyrosine kinase inhibitor AG1478. Moreover, AG1478 also reduced the elevated invasive and migratory capacity of GC cell lines overexpressing EGFL7. Collectively, these results strongly suggest that EGFL7 promotes metastasis by activating EMT through an EGFR-AKT-Snail signaling pathway. Disruption of EGFL7-EGFR-AKT-Snail signaling may a promising therapeutic strategy for gastric cancer.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenocarcinoma / genetics*
  • Adenocarcinoma / metabolism
  • Adenocarcinoma / secondary
  • Adult
  • Aged
  • Aged, 80 and over
  • Animals
  • Calcium-Binding Proteins
  • Cell Line, Tumor
  • Cell Movement
  • EGF Family of Proteins
  • Endothelial Growth Factors / antagonists & inhibitors
  • Endothelial Growth Factors / genetics*
  • Endothelial Growth Factors / metabolism
  • Epithelial-Mesenchymal Transition / drug effects
  • ErbB Receptors / antagonists & inhibitors
  • ErbB Receptors / genetics*
  • ErbB Receptors / metabolism
  • Female
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Liver Neoplasms / genetics*
  • Liver Neoplasms / metabolism
  • Liver Neoplasms / secondary
  • Male
  • Mice
  • Mice, Nude
  • Middle Aged
  • Neoplasm Invasiveness
  • Neoplasm Transplantation
  • Proto-Oncogene Proteins c-akt / genetics*
  • Proto-Oncogene Proteins c-akt / metabolism
  • Quinazolines / pharmacology
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • Signal Transduction
  • Snail Family Transcription Factors
  • Stomach Neoplasms / genetics*
  • Stomach Neoplasms / metabolism
  • Stomach Neoplasms / pathology
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Tyrphostins / pharmacology
  • Vimentin / genetics
  • Vimentin / metabolism

Substances

  • Calcium-Binding Proteins
  • EGF Family of Proteins
  • EGFL7 protein, human
  • Endothelial Growth Factors
  • Quinazolines
  • RNA, Small Interfering
  • Snail Family Transcription Factors
  • Transcription Factors
  • Tyrphostins
  • Vimentin
  • RTKI cpd
  • ErbB Receptors
  • Proto-Oncogene Proteins c-akt

Grants and funding

This work was supported by National Natural Science Foundation of China (No. 81001080) and the Open-End Fund for the Valuable and Precision Instruments of Central South University (No. JJ3121). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.