Understanding the relationship between autophagy and excessive oxidative stress is crucial for determining the fate of cancer cells exposed to redox-active chemotherapeutic agents. Previous studies have shown that Mitoquinone (MitoQ), a redox active, mitochondrialy targeted ubiquinone derivative, can induce autophagy through the generation of excess reactive oxygen species and stimulate the antioxidant response involving nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in breast cancer cells. Nrf2 is a transcription factor that is up-regulated during oxidative stress and activates the antioxidant response element, which in turn regulates antioxidant expression. The aim of this study was to evaluate microRNA (miRNA) as a link between oxidative stress and autophagy through modulation of Nrf2 activity. miRNA are endogenous 18-22 bp double stranded RNA that become active when bound to the 3′ UTR of target messenger RNA (mRNA). The primary goal was to suppress Nrf2 activity with miRNA so that oxidative stress, in the absence of antioxidants, can result in apoptosis rather than autophagy. miRNA expression was evaluated using Illumina RNA sequencing analyses in MDA-MB-231 human breast cancer cells after treatment with DMSO or MitoQ (5 μM), in the presence and absence of Nrf2 silencing RNA (siRNA). Preliminary results show that Nrf2 is the most active at or before 18hrs of treatment (tested up to 72hrs) accompanied by a significant increase in nuclear Nrf2 levels. We are currently evaluating the transcriptome to identify key miRNAs that were up-regulated during Nrf2 suppression and down-regulated during Nrf2 activation. Nrf2 activity was also assessed using a stably transfected GFP modified MDA-MB-231 cell line containing the 3′ UTR region of Nrf2. Prior to obtaining the transcriptome, preliminary Nrf2-miRNA tests were performed with miR-93 as this miRNA has been shown to regulate Nrf2 expression in other studies on human breast cancer cell lines. We are currently assessing the effect of miR-93 on Nrf2 regulation, autophagy and apoptosis to decipher how miR-93 and other microRNA regulate Nrf2 signaling following excessive oxidative stress.

Citation Format: Kaytee L. Pokrzywinski, V. Ashutosh Rao. microRNA regulation of Nrf2: A link between autophagy and oxidative stress. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr LB-291. doi:10.1158/1538-7445.AM2015-LB-291