Cancer related mutations in NRF2 impair its recognition by Keap1-Cul3 E3 ligase and promote malignancy

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 105; no. 36; pp. 13568 - 13573
• Main Authors: Shibata, Tatsuhiro, Ohta, Tsutomu, Tong, Kit I, Kokubu, Akiko, Odogawa, Reiko, Tsuta, Koji, Asamura, Hisao, Yamamoto, Masayuki, Hirohashi, Setsuo
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 09.09.2008; National Acad Sciences
• Subjects: Active Transport, Cell Nucleus; Amino acids; Antineoplastic Agents - pharmacology; Base Sequence; Biological Sciences; Cancer; Cell Line, Tumor; Cell lines; Cells; Cullin Proteins - metabolism; Down-Regulation - drug effects; Enzymes; Gene expression regulation; Gene Expression Regulation, Neoplastic - drug effects; Genes; Genetic mutation; Humans; Intracellular Signaling Peptides and Proteins - metabolism; Kelch-Like ECH-Associated Protein 1; Lung neoplasms; Models, Molecular; Mutation; Mutation - genetics; Neoplasms - genetics; Neoplasms - metabolism; NF-E2-Related Factor 2 - chemistry; NF-E2-Related Factor 2 - genetics; NF-E2-Related Factor 2 - metabolism; Oxidative Stress; Protein Binding; Protein Structure, Tertiary; Small interfering RNA; Studies; Substrate Specificity; Transcription, Genetic - genetics; Tumor cell line; Tumors
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0806268105

The nuclear factor E2-related factor 2 (Nrf2) is a master transcriptional activator of genes encoding numerous cytoprotective enzymes that are induced in response to environmental and endogenously derived oxidative/electrophilic agents. Under normal, nonstressed circumstances, low cellular concentrations of Nrf2 are maintained by proteasomal degradation through a Keap1-Cul3-Roc1-dependent mechanism. A model for Nrf2 activation has been proposed in which two amino-terminal motifs, DLG and ETGE, promote efficient ubiquitination and rapid turnover; known as the two-site substrate recognition/hinge and latch model. Here, we show that in human cancer, somatic mutations occur in the coding region of NRF2, especially among patients with a history of smoking or suffering from squamous cell carcinoma; in the latter case, this leads to poor prognosis. These mutations specifically alter amino acids in the DLG or ETGE motifs, resulting in aberrant cellular accumulation of Nrf2. Mutant Nrf2 cells display constitutive induction of cytoprotective enzymes and drug efflux pumps, which are insensitive to Keap1-mediated regulation. Suppression of Nrf2 protein levels by siRNA knockdown sensitized cancer cells to oxidative stress and chemotherapeutic reagents. Our results strongly support the contention that constitutive Nrf2 activation affords cancer cells with undue protection from their inherently stressed microenvironment and anti-cancer treatments. Hence, inactivation of the Nrf2 pathway may represent a therapeutic strategy to reinforce current treatments for malignancy. Congruously, the present study also provides in vivo validation of the two-site substrate recognition model for Nrf2 activation by the Keap1-Cul3-based E3 ligase.