Reduced expression of EI24 confers resistance to gefitinib through IGF-1R signaling in PC9 NSCLC cells

Lung Cancer. 2015 Nov;90(2):175-81. doi: 10.1016/j.lungcan.2015.08.019. Epub 2015 Sep 3.

Abstract

Objectives: Lung cancer is the commonly diagnosed cancer and is the leading cause of cancer-related mortality worldwide. The most prevalent form of lung cancer is NSCLC, comprising 80% of all lung cancer cases, and epidermal growth factor receptor (EGFR) is frequently mutated in NSCLC. EI24 is a p53-responsive gene and plays an important role in tumor suppression. In the current study, we found that reduced expression of EI24 conferred resistance to EGFR-tyrosine-kinase inhibitor (TKI) in NSCLC cells.

Materials and methods: The correlation between EI24 expression and EGFR-TKI drug resistance in EGFR-driven tumors were determined from microarray datasets. The phospho-protein expression profiles of receptor tyrosine kinases and protein kinases were examined using antibody arrays method in PC9 cells expressing shRNAs targeting EI24 and gefitinib-resistant PC9-GR cells expressing exogenous EI24.

Results and conclusions: The EGFR-TKI resistant clones had reduced expression of EI24 mRNA compared to the sensitive clones, and EI24 knockdown rendered sensitive cells resistant to EGFR-TKI. Receptor tyrosine kinase screening revealed the involvement of a kinase switch in EI24-mediated regulation of drug sensitivity. We found that EI24 modulates the insulin growth factor-1 receptor (IGF-1R) pathway through the induction of IGF-1. Combination treatment with EGFR and IGF-1R inhibitors significantly reduced the viability of EI24 knockdown-induced resistant cell lines compared to single-agent treatments. We also showed that low EI24 and high IGF-1R expressions in lung cancer patients were correlated with reduced overall survival. Taken together, these results suggest a potential role for EI24 as a biomarker of drug resistance, and indicate that combination therapy with EGFR and IGF-1R inhibitors would be effective in NSCLC patients with low EI24 expression.

Keywords: Drug resistance; EGFR-TKI; EI24; IGF-1R; NSCLC.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Apoptosis Regulatory Proteins / genetics*
  • Carcinoma, Non-Small-Cell Lung / drug therapy*
  • Carcinoma, Non-Small-Cell Lung / genetics*
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm / drug effects
  • Drug Resistance, Neoplasm / genetics
  • ErbB Receptors / genetics
  • Gefitinib
  • Humans
  • Insulin / genetics
  • Lung Neoplasms / drug therapy*
  • Lung Neoplasms / genetics*
  • Mutation / drug effects
  • Mutation / genetics
  • Nuclear Proteins / genetics*
  • Protein Kinase Inhibitors / pharmacology
  • Protein-Tyrosine Kinases / genetics
  • Quinazolines / pharmacology*
  • RNA, Messenger / genetics
  • Receptor, IGF Type 1 / genetics*
  • Signal Transduction / drug effects

Substances

  • Antineoplastic Agents
  • Apoptosis Regulatory Proteins
  • EI24 protein, human
  • Insulin
  • Nuclear Proteins
  • Protein Kinase Inhibitors
  • Quinazolines
  • RNA, Messenger
  • EGFR protein, human
  • ErbB Receptors
  • Protein-Tyrosine Kinases
  • Receptor, IGF Type 1
  • Gefitinib