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Aberrant regulation of the MRP3 gene in non-small cell lung carcinoma

Christopher M Mahaffey1, Nichole C Mahaffey, William Holland

  • 1School of Natural Sciences, University of California, Merced, California, USA. christopher.mahaffey@ucdmc.ucdavis.edu

Journal of Thoracic Oncology : Official Publication of the International Association for the Study of Lung Cancer
|November 18, 2011
PubMed
Abstract

Insights

Nuclear factor erythroid-2-related factor 2 (Nrf2) directly upregulates multidrug-resistant protein-3 (MRP3) in non-small cell lung cancer (NSCLC). Keap1/Nrf2 mutations correlate with higher MRP3 RNA levels in NSCLC tumors.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Genetics

Background:

  • Multidrug-resistant protein-3 (MRP3) is a transporter protein involved in drug efflux.
  • Aberrant MRP3 expression is linked to drug resistance in non-small cell lung carcinoma (NSCLC).
  • The transcription factor nuclear factor erythroid-2-related factor 2 (Nrf2) and its repressor Keap1 are key regulators of cellular defense mechanisms.

Purpose of the Study:

  • To investigate the direct regulation of MRP3 by Nrf2 in NSCLC.
  • To determine the correlation between MRP3 expression and the mutational status of Nrf2, Keap1, and p53 in NSCLC.
  • To elucidate the role of these genetic alterations in drug resistance.

Main Methods:

  • Chromatin immunoprecipitation (ChIP) assays to assess Nrf2 binding to the MRP3 promoter.
  • Analysis of MRP3 RNA and protein expression in NSCLC cell lines.
  • Mutation analysis of Keap1, Nrf2, and p53 in NSCLC patient tumor specimens.

Main Results:

  • Nrf2 directly binds to a specific site on the MRP3 promoter, leading to its upregulation.
  • Elevated Nrf2 protein levels correlated with increased MRP3 RNA expression in NSCLC cell lines.
  • Mutations in Keap1/Nrf2 were significantly associated with higher MRP3 RNA levels in patient tumors (p < 0.05).
  • p53 mutations were present in 33% of cases, and all Keap1 mutant-positive tumors also had p53 mutations (p = 0.0019).

Conclusions:

  • Nrf2 directly regulates MRP3 gene expression in NSCLC.
  • Keap1/Nrf2 mutations are linked to increased MRP3 expression in NSCLC, potentially contributing to drug resistance.
  • The interplay between Nrf2, Keap1, and p53 mutations warrants further investigation in the context of NSCLC therapy.

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