Downregulated ABCG2 enhances sensitivity to topoisomerase I inhibitor in epidermal growth factor receptor tyrosine kinase inhibitor-resistant non-small cell lung cancer

J Thorac Oncol. 2010 Nov;5(11):1726-33. doi: 10.1097/JTO.0b013e3181f0b6af.

Abstract

Introduction: Understanding the mechanisms of drug resistance to epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI) is essential to develop novel chemotherapies for non-small cell lung cancer (NSCLC). Therefore, we analyzed the expression and function of ATP-binding cassette (ABC) transporters in EGFR TKI-resistant NSCLC.

Methods: In three newly established AG1478-resistant NSCLC cell lines, we evaluated the expression profile of ABC transporters and genotyping of ABCG2 by real-time polymerase chain reaction and elucidated their function by Hoechst dye efflux analyses. The growth-inhibitory effect of the topoisomerase I inhibitor Hoechst 33342, which is extruded by ABCG2, was also investigated in these cells using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay.

Results: In AG1478-resistant cells, significantly less ABCG2 was expressed, and the ratios of the cells with a strong ability to extrude Hoechst dye were remarkably smaller than in the parent cells. Because of the ABCG2 downregulation and loss of function due to C421A/C421A homozygosity, PC-14AG50R was thus considered to be more sensitive to Hoechst 33342 than the parental cells. All AG1478-resistant cells were more sensitive to the combination of Hoechst 33342 and AG1478 than to single agent.

Conclusions: Resistance to EGFR TKI in NSCLC is associated with the downregulation of ABCG2 expression. A topoisomerase I inhibitor alone or in combination with EGFR TKI might offer a promising strategy for treating NSCLC that is resistant to EGFR TKI.

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily G, Member 2
  • ATP-Binding Cassette Transporters / genetics*
  • Adenocarcinoma / drug therapy
  • Adenocarcinoma / genetics
  • Adenocarcinoma / pathology
  • Benzimidazoles / therapeutic use
  • Carcinoma, Non-Small-Cell Lung / drug therapy*
  • Carcinoma, Non-Small-Cell Lung / genetics
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Cell Proliferation
  • DNA Topoisomerases, Type I / chemistry*
  • DNA Topoisomerases, Type I / metabolism
  • DNA, Neoplasm / genetics
  • Down-Regulation
  • Drug Resistance, Neoplasm*
  • Enzyme Inhibitors / therapeutic use
  • ErbB Receptors / antagonists & inhibitors*
  • ErbB Receptors / genetics
  • ErbB Receptors / metabolism
  • Genotype
  • Humans
  • Lung Neoplasms / drug therapy*
  • Lung Neoplasms / genetics
  • Lung Neoplasms / pathology
  • Mutation / genetics
  • Neoplasm Proteins / genetics*
  • Polymerase Chain Reaction
  • Protein Tyrosine Phosphatases / antagonists & inhibitors
  • Quinazolines
  • Radiation-Sensitizing Agents / therapeutic use
  • Tumor Cells, Cultured
  • Tyrphostins / therapeutic use*

Substances

  • ABCG2 protein, human
  • ATP Binding Cassette Transporter, Subfamily G, Member 2
  • ATP-Binding Cassette Transporters
  • Benzimidazoles
  • DNA, Neoplasm
  • Enzyme Inhibitors
  • Neoplasm Proteins
  • Quinazolines
  • Radiation-Sensitizing Agents
  • Tyrphostins
  • RTKI cpd
  • EGFR protein, human
  • ErbB Receptors
  • Protein Tyrosine Phosphatases
  • DNA Topoisomerases, Type I
  • bisbenzimide ethoxide trihydrochloride