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Oncogenic Ras downregulates mdr1b expression through generation of reactive oxygen species

Semo Jun1, Seok Won Kim2, Byeol Kim1

  • 1Departments of Premedical Sciences, College of Medicine, Chosun University, Gwangju 61452, Korea.

The Korean Journal of Physiology & Pharmacology : Official Journal of the Korean Physiological Society and the Korean Society of Pharmacology
|May 13, 2020
PubMed

Insights

Oncogenic H-Ras (V12) downregulates mdr1b expression and increases doxorubicin sensitivity in NIH3T3 cells. This effect involves reactive oxygen species (ROS) and ERK activation, suggesting potential therapeutic targets.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Oncology

Background:

  • The multidrug resistance gene 1b (mdr1b) plays a crucial role in drug efflux and multidrug resistance.
  • Oncogenic mutations in signaling pathways, such as H-Ras, can alter cellular responses to chemotherapy.
  • Understanding the interplay between oncogenic signaling and drug resistance mechanisms is vital for cancer treatment.

Purpose of the Study:

  • To investigate the impact of oncogenic H-Ras (V12) on rat mdr1b expression in NIH3T3 cells.
  • To elucidate the underlying molecular mechanisms, including the role of reactive oxygen species (ROS) and the ERK pathway.
  • To explore the correlation between H-Ras expression, mdr1b regulation, and sensitivity to doxorubicin toxicity.

Main Methods:

  • Utilized NIH3T3 cells stably expressing oncogenic H-Ras (V12).
  • Assessed mdr1b promoter activity and mRNA expression.
  • Employed antioxidants (N-acetylcysteine) and NADPH oxidase inhibitors (diphenylene iodonium) to investigate ROS involvement.
  • Used ERK inhibitors (PD98059, U0126) to examine the role of the ERK pathway.
  • Evaluated doxorubicin-induced cell death and apoptosis.

Main Results:

  • Constitutive H-Ras (V12) expression significantly downregulated mdr1b promoter activity and mRNA levels.
  • H-Ras (V12) expression correlated positively with sensitivity to doxorubicin toxicity.
  • Antioxidant and NADPH oxidase inhibition treatments enhanced H-Ras-mediated mdr1b downregulation and protected against doxorubicin-induced cell death.
  • ERK pathway inhibition increased mdr1b promoter activity and reduced doxorubicin-induced apoptosis.

Conclusions:

  • Oncogenic H-Ras (V12) downregulates mdr1b expression, at least partly, through ROS production and subsequent ERK activation.
  • This mechanism contributes to increased sensitivity to doxorubicin toxicity.
  • Targeting ROS production or ERK signaling may represent a strategy to overcome H-Ras-mediated drug resistance.
Keywords:
Extracellular signal-regulated MAP kinasesGenesMultidrug resistanceP-glycoprotein 2RasReactive oxygen species

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