miR-200a Regulates Nrf2 Activation by Targeting Keap1 mRNA in Breast Cancer Cells

Abstract

NF-E2-related factor 2 (Nrf2) is an important transcription factor that activates the expression of cellular detoxifying enzymes. Nrf2 expression is largely regulated through the association of Nrf2 with Kelch-like ECH-associated protein 1 (Keap1), which results in cytoplasmic Nrf2 degradation. Conversely, little is known concerning the regulation of Keap1 expression. Until now, a regulatory role for microRNAs (miRs) in controlling Keap1 gene expression had not been characterized. By using miR array-based screening, we observed miR200a silencing in breast cancer cells and demonstrated that upon re-expression, miR-200a targets the Keap1 3-untranslated region (3-UTR), leading to Keap1 mRNA degradation. Loss of this regulatory mechanism may contribute to the dysregulation of Nrf2 activity in breast cancer. Previously, we have identified epigenetic repression of miR-200a in breast cancer cells. Here, we find that treatment with epigenetic therapy, the histone deacetylase inhibitor suberoylanilide hydroxamic acid, restored miR-200a expression and reduced Keap1 levels. This reduction in Keap1 levels corresponded with Nrf2 nuclear translocation and activation of Nrf2-dependent NAD(P)H-quinone oxidoreductase 1 (NQO1) gene transcription. Moreover, we found that Nrf2 activation inhibited the anchorage-independent growth of breast cancer cells. Finally, our in vitro observations were confirmed in a model of carcinogen-induced mammary hyperplasia in vivo. In conclusion, our study demonstrates that miR-200a regulates the Keap1/Nrf2 pathway in mammary epithelium, and we find that epigenetic therapy can restore miR200a regulation of Keap1 expression, therefore reactivating the Nrf2-dependent antioxidant pathway in breast cancer.

Toll-Like Receptor Signaling Induces Nrf2 Pathway Activation through p62-Triggered Keap1 Degradation

“…The latter might play a critical role in maintaining Nrf2 pathway activation for an extended period of time, which is beneficial for tissue repair since It is well established that Keap1 regulates the Nrf2 signaling pathway, but the regulation of Keap1 itself is less well documented. Recent studies showed that Keap1 is subjected to posttranscription regulation: its mRNA level was affected by microRNA 200a through its 3= untranslated region (32,33). Another study reported that Keap1 overexpression in HepG2 cells inhibits Nrf2 activity (34).…”

MicroRNA Pharmacoepigenetics: Posttranscriptional Regulation Mechanisms behind Variable Drug Disposition and Strategy to Develop More Effective Therapy

“…BCRP/ABCG2, another important efflux transporter in ADME and MDR, is also regulated by a number of miRNAs via direct or indirect mechanisms ( Table 2). The MDR of S1 colon carcinoma cell line is Zhao et al, 2008;Guttilla et al, 2012;Wei et al, 2014a Let-7 Reporter assay, mRNA/protein expression, and function study Zhao et al, 2011 miR-18a Reporter assay, protein expression, association and function study Liu et al, 2009 miR-18a/b, -19b, -20b, -193b, -206 Reporter assay, protein expression Castellano et al, 2009;Leivonen et al, 2009b miR-145 Reporter assay, mRNA and protein expression, and function study Spizzo et al, 2010 miR-22 Reporter assay, protein expression, and function study Pandey and Picard, 2009;Xiong et al, 2010 miR-206 Reporter assay, protein expression, and function study Adams et al, 2007;Kondo et al, 2008 miR-27a via zinc finger and BTB domain containing 10 (ZBTB10) Li et al, 2010a miR-219-5p Reporter assay, mRNA/protein expression, association and function Huang et al, 2015 miR-135b Reporter assay, mRNA and protein expression Aakula et al, 2015 NFE2L2/Nrf2 miR-144 Reporter assay, mRNA and protein expression, and function study Sangokoya et al, 2010 miR-28 Reporter assay, mRNA and protein expression Yang et al, 2011 miR-200a (Activation) via Kelch-like ECH-associated protein 1 (Keap1) Eades et al, 2011;Yang et al, 2014 miR-153, -27a, -142-5p, -144 Reporter assay, mRNA and protein expression, and function study Narasimhan et al, 2012Narasimhan et al, , 2014 Protein expression, and function study Singh et al, 2013 miR-507, -634, -450, -129-5p Reporter assay, mRNA and protein expression, and function study Yamamoto et al, 2014 miR-34a mRNA and protein expression Huang et al, 2014 miR-340 Reporter assay, mRNA and protein expression, and function study Shi et al, 2014a miR-141 via Kelch-like ECH-associated protein 1 (Keap1) …”

Keap1–Nrf2 signalling in pancreatic cancer

“…Beyond translation, Keap1 is silenced through mechanisms such as microRNA repression (i.e. miR-141, miR-200a) (Eades et al, 2011), or autophagosome regulation (i.e. p62/SQSTM1) , resulting in ineffective Nrf2 repression.…”