The Keap1-Nrf2 system in cancers: Stress response and anabolic metabolism

Department of Respiratory Medicine, Tohoku University Graduate School of Medicine Sendai, Japan.
Frontiers in Oncology 12/2012; 2(article 200):200. DOI: 10.3389/fonc.2012.00200
Source: PubMed


The Keap1-Nrf2 [Kelch-like ECH-associated protein 1-nuclear factor (erythroid-derived 2)-like 2] pathway plays a central role in the protection of cells against oxidative and xenobiotic stresses. Nrf2 is a potent transcription activator that recognizes a unique DNA sequence known as the antioxidant response element (ARE). Under normal conditions, Nrf2 binds to Keap1 in the cytoplasm, resulting in proteasomal degradation. Following exposure to electrophiles or reactive oxygen species, Nrf2 becomes stabilized, translocates into the nucleus, and activates the transcription of various cytoprotective genes. Increasing attention has been paid to the role of Nrf2 in cancer cells because the constitutive stabilization of Nrf2 has been observed in many human cancers with poor prognosis. Recent studies have shown that the antioxidant and detoxification activities of Nrf2 confer chemo- and radio-resistance to cancer cells. In this review, we provide an overview of the Keap1-Nrf2 system and discuss its role under physiological and pathological conditions, including cancers. We also introduce the results of our recent study describing Nrf2 function in the metabolism of cancer cells. Nrf2 likely confers a growth advantage to cancer cells through enhancing cytoprotection and anabolism. Finally, we discuss the possible impact of Nrf2 inhibitors on cancer therapy.

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Available from: Yoichiro Mitsuishi, Mar 05, 2015
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    • "Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in defending tissues against elevated oxidative species and toxic damage [12] [13]. In resting cells, the activity of Nrf2 is tightly controlled by Kelch-like ECH-associated protein 1 (Keap1) in the cytoplasm [14]. "
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    ABSTRACT: Arsenic produces liver disease through the oxidative stress. While lutein can alleviate cytotoxic and oxidative injury, nuclear factor erythroid 2-related factor 2 (Nrf2) pathway plays a critical role in defending oxidative species. However, the mechanisms by which lutein protects the liver against the effect of arsenic are not known. Therefore, this study aims to investigate the mechanisms involved in the action of lutein using mice model in which hepatotoxicity was induced by arsenic. We found that mice treatment with lutein could reverse changes in morphological and liver indexes and result in a significant improvement in hepatic function comparing with arsenic trioxide group. Lutein treatment improved the activities of antioxidant enzymes and attenuated increasing of ROS and MDA induced by arsenic trioxide. Lutein could increase the mRNA and protein expression of Nrf2 signaling related genes (Nrf2, Nqo1, Ho-1, and Gst). These findings provide additional evidence that lutein may be useful for reducing reproductive injury associated with oxidative stress by the activation of Nrf2 signaling. Our findings suggest a possible mechanism of antioxidant lutein in preventing the hepatotoxicity, which implicate that a dietary lutein may be a potential treatment for liver diseases, especially for arsenicosis therapy.
    Full-text · Article · Feb 2015
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    • "While NRF2 decreases tumor susceptibility in most carcinogenesis models, constitutive activation of NRF2 may enhance tumor cell proliferation and/or confer drug resistance in lung, pancreatic as well as colorectal cancer cells (Arlt et al. 2013; Bryan et al. 2013; Duong et al. 2014b; Homma et al. 2009; Hong et al. 2010; Lister et al. 2011; Mitsuishi et al. 2012; Niture et al. 2014; Singh et al. 2008; Storr et al. 2013; Yamadori et al. 2012). Indeed, NRF2 is up-regulated in many types of tumors through somatic mutations that block KEAP1-dependent regulation of NRF2 stability (Mitsuishi et al. 2012; Niture et al. 2014; Storr et al. 2013). Targeting NRF2 either by RNA interference or by small molecules inhibited tumor growth and increased efficacy of chemotherapy (Singh et al. 2008) or EGF-driven proliferation (Yamadori et al. 2012) in non-small cell lung cancer models and reduced the proliferation and drug-resistance in human lung cancer cells (Homma et al. 2009) or human pancreatic cancer cells (Arlt et al. 2013; Duong et al. 2014b; Hong et al. 2010; Lister et al. 2011). "
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    ABSTRACT: NRF2 is a nuclear transcription factor activated in response to oxidative stress and related with metabolizing of xenotoxic materials and ABC transporter mediated drug resistance. We studied the expression of mRNAs under the siRNA-mediated knockdown of NRF2 and tBHQ-treated condition in AsPC-1 metastatic pancreatic cancer cell line to understand the AsPC-1 specific role(s) of NRF2 and further to investigate the relationship between drug resistance and metastatic plasticity and mobility of AsPc1. Here we show that the genes of aldo–keto reductases, cytochrome P450 family, aldehyde dehydrogenase, thioredoxin reductase, ABC transporter and epoxide hydrolase responsible for drug metabolism or oxidative stress concisely responded to NRF2 stabilization and knockdown of NRF2. In addition the expression of PIR, a candidate of oncogene and KISS1, a suppressor of metastasis were affected by NRF2 stabilization and knockdown. Our result provide comprehensive understanding of NRF2 target genes of drug response, oxidative stress response and metastasis in AsPc-1 metastatic pancreatic cancer cell line. Electronic supplementary material The online version of this article (doi:10.1007/s13258-014-0253-2) contains supplementary material, which is available to authorized users.
    Full-text · Article · Jan 2015 · Genes & genomics
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    • "The activation of NRF2 using pharmacological interventions or genetic approaches can prevent oxidative stress-associated diseases, such as inflammatory diseases and cancer [27], [28], [31]. Whereas, a constitutive increase in NRF2 expression can promote cancer cell survival in the stressful tumor environment and in the presence of chemotherapeutic agents [33], [41], [42]. In the present study, we investigated NRF2 as a potential molecular determinant of the efficacy of Pba-based PDT in human breast carcinoma MDA-MB-231 cells and colon carcinoma HT29 cells. "
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    ABSTRACT: Photodynamic therapy (PDT) has emerged as an effective treatment for various solid tumors. The transcription factor NRF2 is known to protect against oxidative and electrophilic stress; however, its constitutive activity in cancer confers resistance to anti-cancer drugs. In the present study, we investigated NRF2 signaling as a potential molecular determinant of pheophorbide a (Pba)-based PDT by using NRF2-knockdown breast carcinoma MDA-MB-231 cells. Cells with stable NRF2 knockdown showed enhanced cytotoxicity and apoptotic/necrotic cell death following PDT along with increased levels of singlet oxygen and reactive oxygen species (ROS). A confocal microscopic visualization of fluorogenic Pba demonstrated that NRF2-knockdown cells accumulate more Pba than control cells. A subsequent analysis of the expression of membrane drug transporters showed that the basal expression of BCRP is NRF2-dependent. Among measured drug transporters, the basal expression of breast cancer resistance protein (BCRP; ABCG2) was only diminished by NRF2-knockdown. Furthermore, after incubation with the BCRP specific inhibitor, differential cellular Pba accumulation and ROS in two cell lines were abolished. In addition, NRF2-knockdown cells express low level of peroxiredoxin 3 compared to the control, which implies that diminished mitochondrial ROS defense system can be contributing to PDT sensitization. The role of the NRF2-BCRP pathway in Pba-PDT response was further confirmed in colon carcinoma HT29 cells. Specifically, NRF2 knockdown resulted in enhanced cell death and increased singlet oxygen and ROS levels following PDT through the diminished expression of BCRP. Similarly, PDT-induced ROS generation was substantially increased by treatment with NRF2 shRNA in breast carcinoma MCF-7 cells, colon carcinoma HCT116 cells, renal carcinoma A498 cells, and glioblastoma A172 cells. Taken together, these results indicate that the manipulation of NRF2 can enhance Pba-PDT sensitivity in multiple cancer cells.
    Full-text · Article · Sep 2014 · PLoS ONE
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