Mitoquinone (MitoQ), a redox-active mitochondrially targeted chemotherapy, activates autophagy through the production of reactive oxygen species (ROS) in breast cancer cells. Studies have also shown a concomitant activation of Nrf2 and the antioxidant response with MitoQ treatment. Nrf2 (nuclear factor (erythroid-derived 2)-like 2) is a transcription factor that regulates the antioxidant response element. Drugs that stimulate Nrf2 are ideal for the treatment of diseases induced by oxidative stress; however, over-activation of Nrf2 may promote tumor growth and diminish the effects of redox active chemotherapies. Therefore, understanding the relationship between autophagy and oxidative stress is crucial for determining the fate of cancer cells exposed to redox-active oncology agents. The aim of this study was to evaluate microRNA (miRNA) as a link between oxidative stress and autophagy through modulation of Nrf2 activity. microRNA are endogenous small (18-22 base pairs long) double stranded RNA that bind to the 3’ UTR of target mRNA. miRNA function through translational repression via mRNA recycling and degradation. To this aim we set out on finding miRNA that suppress the antioxidant response, modulated by Nrf2, in cancer cells after redox therapy with the goal of inducing a death response. After 24 hours of non-target pool or Nrf2 silencing, using small interfering RNAs, MDA-MB-231 cells were treated with DMSO or MitoQ for 18 hours. RNA was extracted and miRNAs were identified using Illumina RNA sequencing. DEseq revealed 97 miRNAs that were differentially expressed at α < 0.05. Biologically significant miRNAs were then distinguished by using a Log2 fold change cut off of -1.0 < and < 1.0, which identified 39 microRNAs. Since miRNA should be high when their target is low we were predominantly interested in the 15 miRNAs that were down-regulated (DMSO:MitoQ). 7 of the 15 down-regulated miRNAs were also down-regulated in the presence of Nrf2 silencing in both the DMSO and MitoQ treatments. We are currently investigating these 7 miRNAs in terms of the specific effect they have on the Nrf2 pathway during redox therapy.

Citation Format: Francesca Mascia, Kaytee L. Pokrzywinski, V. Ashutosh Rao. microRNA regulation of Nrf2 and the antioxidant response in breast cancer cells following redox therapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1090.