Nrf2 induces cisplatin resistance through activation of autophagy in ovarian carcinoma

Int J Clin Exp Pathol. 2014 Mar 15;7(4):1502-13. eCollection 2014.

Abstract

Cisplatin resistance is a major problem affecting ovarian carcinoma treatment. NF-E2-related factor 2 (Nrf2), a nuclear transcription factor, plays an important role in chemotherapy resistance. However, the underlying mechanism by which Nrf2 mediates cisplatin chemoresistance is unclear.

Methods: The human ovarian carcinoma cell line, A2780, and its cisplatin-resistant variant, A2780cp were cultivated. Cell viability was determined with WST-8 assay. Western blot was applied to detect the expression of Nrf2, Nrf2 target genes, and autophagy-related proteins. RNA interference was used to knock down target genes. Annexin V and propidium iodide (PI) staining was utilized to quantify apoptosis. The ultrastructural analysis of autophagosomes was performed by transmission electron microscopy (TEM).

Results: Nrf2 and its targeting genes, NQO1 and HO-1, are overexpressed in A2780cp cells compared with A2780 cells. Knocking down Nrf2 sensitized A2780cp cells to cisplatin treatment and decreased autophagy-related genes, Atg3, Atg6, Atg12 and p62 in both mRNA and protein levels. Furthermore, we demonstrated that in both cell lines cisplatin could induce the formation of autophagosomes and upregulate the expression of autophagy-related genes Atg3, Atg6 and Atg12. Treatment with an autophagy inhibitor, 3-Methyladenine (3-MA), or beclin 1 siRNA enhanced cisplatin-induced cell death in A2780cp cells, suggesting that inhibition of autophagy renders resistant cells to be more sensitive to cisplatin. Taken together, Nrf2 signaling may regulate cisplatin resistance by activating autophagy.

Conclusions: Nrf2-activated autophagy may function as a novel mechanism causing cisplatin-resistance.

Keywords: Nrf2; Ovarian carcinoma; autophagy; chemoresistance; cisplatin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives
  • Adenine / pharmacology
  • Adenocarcinoma / drug therapy*
  • Adenocarcinoma / physiopathology
  • Antineoplastic Agents / therapeutic use*
  • Autophagy / drug effects
  • Autophagy / physiology*
  • Autophagy-Related Protein 12
  • Autophagy-Related Proteins
  • Biomarkers, Tumor / physiology
  • Cell Line, Tumor
  • Cisplatin / therapeutic use*
  • Drug Resistance, Neoplasm / physiology*
  • Female
  • Heme Oxygenase-1 / physiology
  • Humans
  • NAD(P)H Dehydrogenase (Quinone) / physiology
  • NF-E2-Related Factor 2 / physiology*
  • Ovarian Neoplasms / drug therapy*
  • Ovarian Neoplasms / physiopathology
  • RNA-Binding Proteins / physiology
  • Signal Transduction / physiology
  • Small Ubiquitin-Related Modifier Proteins / physiology
  • Ubiquitin-Conjugating Enzymes / physiology

Substances

  • ATG12 protein, human
  • Antineoplastic Agents
  • Autophagy-Related Protein 12
  • Autophagy-Related Proteins
  • Biomarkers, Tumor
  • NF-E2-Related Factor 2
  • NFE2L2 protein, human
  • P62 protein, human
  • RNA-Binding Proteins
  • Small Ubiquitin-Related Modifier Proteins
  • 3-methyladenine
  • HMOX1 protein, human
  • Heme Oxygenase-1
  • NAD(P)H Dehydrogenase (Quinone)
  • NQO1 protein, human
  • Ubiquitin-Conjugating Enzymes
  • ATG3 protein, human
  • Adenine
  • Cisplatin