Oncogenic Ras downregulates mdr1b expression through generation of reactive oxygen species

Semo Jun; Seok Won Kim; Byeol Kim; In-Youb Chang; Seon-Joo Park

doi:10.4196/kjpp.2020.24.3.267

Oncogenic Ras downregulates mdr1b expression through generation of reactive oxygen species

Korean J Physiol Pharmacol. 2020 May 1;24(3):267-276. doi: 10.4196/kjpp.2020.24.3.267.

Authors

Semo Jun¹, Seok Won Kim², Byeol Kim¹, In-Youb Chang³, Seon-Joo Park¹

Affiliations

¹ Departments of Premedical Sciences, College of Medicine, Chosun University, Gwangju 61452, Korea.
² Departments of Neurosurgery, College of Medicine, Chosun University, Gwangju 61452, Korea.
³ Departments of Anatomy, College of Medicine, Chosun University, Gwangju 61452, Korea.

Abstract

In the present study, we investigated the effect of oncogenic H-Ras on rat mdr1b expression in NIH3T3 cells. The constitutive expression of H-Ras^V12 was found to downregulate the mdr1b promoter activity and mdr1b mRNA expression. The doxorubicin-induced mdr1b promoter activity of the H-Ras^V12 expressing NIH3T3 cells was markedly lower than that of control NIH3T3 cells. Additionally, there is a positive correlation between the level of H-Ras^V12 expression and a sensitivity to doxorubicin toxicity. To examine the detailed mechanism of H-Ras^V12-mediated down-regulation of mdr1b expression, antioxidant N-acetylcysteine (NAC) and NADPH oxidase inhibitor diphenylene iodonium (DPI) were used. Pretreating cells with either NAC or DPI significantly enhanced the oncogenic H-Ras-mediated down-regulation of mdr1b expression and markedly prevented doxorubicin-induced cell death. Moreover, NAC and DPI treatment led to a decrease in ERK activity, and the ERK inhibitors PD98059 or U0126 enhanced the mdr1b-Luc activity of H-Ras^V12-NIH3T3 and reduced doxorubicin-induced apoptosis. These data suggest that Ras^V12 expression could downregulate mdr1b expression through intracellular reactive oxygen species (ROS) production, and ERK activation induced by ROS, is at least in part, contributed to the downregulation of mdr1b expression.

Keywords: Extracellular signal-regulated MAP kinases; Genes; Multidrug resistance; P-glycoprotein 2; Ras; Reactive oxygen species.