MiR-21 overexpression is associated with acquired resistance of EGFR-TKI in non-small cell lung cancer

Lung Cancer. 2014 Feb;83(2):146-53. doi: 10.1016/j.lungcan.2013.11.003. Epub 2013 Nov 13.


Background and purpose: With the increasing use of epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) in patients with advanced non-small cell lung cancer (NSCLC), its acquired resistance has become a major clinical problem. Recent studies revealed that miR-21 was involved into the resistance of cytotoxic agents. The aim of this study was to investigate its role in the acquired resistance of NSCLC to EGFR-TKI.

Methods: EGFR-TKI-sensitive human lung adenocarcinoma cell line PC9 and the acquired resistant cell line, PC9R, were used. Lentiviral vectors were used to infect PC9 or PC9R to regulate the miR-21 expression. The expression of targeted proteins PTEN and PDCD4 was controlled by RNA interference. MicroRNA array, RT-PCR and TaqMan MicroRNA Assays were used to detect miR-21 expression. The MTT and Annexin V assays were used to determine proliferation and apoptosis. Western Blot and immunohistochemistry were used to analyze target protein expression (PTEN, PDCD4, Akt, p-Akt). We also constructed PC9R xenograft tumor model to observe the relationship between miR-21 and EGFR-TKI resistance in vivo and validated it in the clinical serum specimens of NSCLC patients treated with EGFR-TKI.

Result: MiR-21 was overexpressed in the EGFR-TKI resistant cell line PC9R relative to PC9. The level of miR-21 was reversely correlated with the expression of PTEN and PDCD4 and positive correlated with PI3K/Akt pathway. Inhibiting miR-21 with lentivirus vector induces apoptosis in PC9R cell line and inhibiting miR-21with ASO suppressed tumor growth in nude mice treated with EGFR-TKI. Furthermore, serum miR-21 expression in NSCLC patients treated with EGFR-TKI was significantly higher at the time of acquiring resistance than at baseline (p<0.01).

Conclusion: miR-21 is involved in acquired resistance of EGFR-TKI in NSCLC, which is mediated by down-regulating PTEN and PDCD4 and activating PI3K/Akt pathway.

Keywords: Acquired resistance; EGFR-TKI; Non-small cell lung cancer; PDCD4; PI3K/Akt; PTEN; miR-21.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis Regulatory Proteins / genetics
  • Carcinoma, Non-Small-Cell Lung / genetics
  • Carcinoma, Non-Small-Cell Lung / therapy*
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Drug Resistance, Neoplasm / genetics
  • ErbB Receptors / antagonists & inhibitors
  • ErbB Receptors / genetics
  • Female
  • Gefitinib
  • Humans
  • Lung Neoplasms / genetics
  • Lung Neoplasms / therapy*
  • Mice
  • Mice, Inbred BALB C
  • Mice, Nude
  • MicroRNAs / genetics
  • MicroRNAs / metabolism*
  • PTEN Phosphohydrolase / genetics
  • Protein Kinase Inhibitors / pharmacology
  • Protein Kinase Inhibitors / therapeutic use*
  • Quinazolines / pharmacology
  • Quinazolines / therapeutic use*
  • RNA Interference
  • RNA-Binding Proteins / genetics
  • Transgenes / genetics
  • Tumor Burden / drug effects
  • Xenograft Model Antitumor Assays


  • Apoptosis Regulatory Proteins
  • MIRN21 microRNA, human
  • MicroRNAs
  • PDCD4 protein, human
  • Protein Kinase Inhibitors
  • Quinazolines
  • RNA-Binding Proteins
  • EGFR protein, human
  • ErbB Receptors
  • PTEN Phosphohydrolase
  • Gefitinib