Molecular Mechanisms of Chemoprevention: NRF2 Signaling

Summary

Principal Investigator: Thomas W Kensler
Abstract: Cancer prevention involving reduction or elimination of human exposure to environmental carcinogens may not always be possible. Inhibition of the development of cancer by the administration of anticarcinogenic agents may offer practical alternatives for reducing human cancer burden. However, the successful utilization of chemopreventive interventions will require solid mechanistic understanding of the action(s) of these agents. We have identified the Keap1-Nrf2-ARE signaling pathway as a target for chemoprevention. The Nrf2 transcription factor regulates an integrated cell survival response that can be triggered by multiple classes of cancer chemopreventive agents (e.g., dithiolethiones, isothiocyanates, triterpenoids). In this project, we will use both pharmacologic and genetic approaches to further probe the molecular mechanisms of action of these chemopreventive agents, assess their efficacy in animal models with close relevance to human carcinogenesis and use these interventions to validate intermediate biomarkers. With a continuing focus on the roles of infection with hepatitis B virus and co-exposure to the fungal toxin aflatoxin on human risk for hepatocellular carcinoma, we will purse three aims. First, we will utilize advanced methods of isotope-dilution mass spectrometry for the quantitation of aflatoxin biomarkers in liver, blood, urine and feces in order to develop for the first time a comprehensive mass balance for the fate of the ultimate carcinogen, exo-aflatoxin-epoxide, in rats. The predictive value of these biomarkers for individual risk of liver cancer will be assessed. Biomarkers will be quantified longitudinally during a bioassay for protection against hepatocarcinogenesis by the exceptionally potent triterpenoid activator of Nrf2 signaling, CDDO-Im. We will also evaluate the predictive value of monitoring DNA circulating in plasma for mutations in target oncogenes using quantitative short oligonucleotide mass spectrometry. In the second aim, we will evaluate the similarities and distinctions of chemical class, species and genetic activation of Keap1-Nrf2 signaling by comparing the gene expression patterns in rat and mouse liver following treatment with lead compounds of 3 different chemical classes of Nrf2 activators at doses equi-effective for inhibition of aflatoxin-induced preneoplastic lesions and by comparing the gene expression patterns in liver of mice in which either Nrf2 or its repressor Keap1 have been genetically disrupted. The impact of these genetic and pharmacologic interventions on aflatoxin disposition will be determined using the mass spectrometry-based analysis of its biomarkers. Third, we will capitalize on our novel observation that Nrf2 signaling influences tissue regeneration and repair by examining the post initiation effects of triterpenoids during aflatoxin-induced hepatocarcinogenesis in the rat and in a murine model recapitulating major human risk factors for HCC, namely, aflatoxin exposure and infection with HBV. Collectively, these studies will further the goal of effectively using activators of Nrf2 signaling as protective agents in human populations exposed to environmental toxicants. PUBLIC HEALTH RELEVANCE: Cancer prevention involving reduction or elimination of human exposure to environmental carcinogens may not always be possible. The overriding goal of our work remains to provide the mechanistic framework to facilitate the efficient translation of the most effective of the small molecule activators of Nrf2 signaling into use as protective agents in human populations exposed to environmental toxicants such as aflatoxins. To facilitate this goal we need better understanding of the molecular mechanisms of action of our chemopreventive agents, further validation of intermediate biomarkers, and assessment of efficacy in animal models with close relevance to human carcinogenesis.
Funding Period: 1985-09-01 - 2015-02-28
more information: NIH RePORT

Top Publications

  1. ncbi Identification of novel transcriptional networks in response to treatment with the anticarcinogen 3H-1,2-dithiole-3-thione
    Yong Huang
    W Harry Feinstone Center for Genomic Research, University of Memphis, Memphis, Tennessee 38152, USA
    Physiol Genomics 24:144-53. 2006
  2. pmc Analyzing microarray data with transitive directed acyclic graphs
    Vinhthuy Phan
    Department of Computer Science, The University of Memphis, Memphis, TN 38152, USA
    J Bioinform Comput Biol 7:135-56. 2009
  3. pmc Genetic mutations associated with cigarette smoking in pancreatic cancer
    Amanda Blackford
    Department of Oncology, The Sol Goldman Pancreatic Cancer Research Center, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21231, USA
    Cancer Res 69:3681-8. 2009
  4. pmc Genetic versus chemoprotective activation of Nrf2 signaling: overlapping yet distinct gene expression profiles between Keap1 knockout and triterpenoid-treated mice
    Melinda S Yates
    Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
    Carcinogenesis 30:1024-31. 2009
  5. pmc Disruption of Nrf2 impairs the resolution of hyperoxia-induced acute lung injury and inflammation in mice
    Narsa M Reddy
    Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA
    J Immunol 182:7264-71. 2009
  6. pmc Targeting NRF2 signaling for cancer chemoprevention
    Mi Kyoung Kwak
    College of Pharmacy, Yeungnam University, 214 1 Dae Dong, Gyeongsan si, Gyeongsangbuk do 712 749, South Korea
    Toxicol Appl Pharmacol 244:66-76. 2010
  7. pmc Nrf2: friend or foe for chemoprevention?
    Thomas W Kensler
    Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, MD 21205, USA
    Carcinogenesis 31:90-9. 2010
  8. pmc When NRF2 talks, who's listening?
    Nobunao Wakabayashi
    Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pennsylvania 15261, USA
    Antioxid Redox Signal 13:1649-63. 2010
  9. pmc Aflatoxin: a 50-year odyssey of mechanistic and translational toxicology
    Thomas W Kensler
    Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
    Toxicol Sci 120:S28-48. 2011
  10. pmc Tricyclic compounds containing nonenolizable cyano enones. A novel class of highly potent anti-inflammatory and cytoprotective agents
    Tadashi Honda
    Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
    J Med Chem 54:1762-78. 2011

Research Grants

Detail Information

Publications36

  1. ncbi Identification of novel transcriptional networks in response to treatment with the anticarcinogen 3H-1,2-dithiole-3-thione
    Yong Huang
    W Harry Feinstone Center for Genomic Research, University of Memphis, Memphis, Tennessee 38152, USA
    Physiol Genomics 24:144-53. 2006
    ..000331) pathways. These findings showed a profound impact of D3T on lipid metabolism and anti-inflammatory/immune-suppressive response, indicating a broader cytoprotective effect of this compound than previously expected...
  2. pmc Analyzing microarray data with transitive directed acyclic graphs
    Vinhthuy Phan
    Department of Computer Science, The University of Memphis, Memphis, TN 38152, USA
    J Bioinform Comput Biol 7:135-56. 2009
    ..The advantages and overall utility of the method in elaborating drug structure activity relationships are exemplified in a controlled study with real and simulated data...
  3. pmc Genetic mutations associated with cigarette smoking in pancreatic cancer
    Amanda Blackford
    Department of Oncology, The Sol Goldman Pancreatic Cancer Research Center, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21231, USA
    Cancer Res 69:3681-8. 2009
    ..Pancreatic carcinomas from cigarette smokers harbor more mutations than do carcinomas from never smokers. The types and patterns of these mutations provide insight into the mechanisms by which cigarette smoking causes pancreatic cancer...
  4. pmc Genetic versus chemoprotective activation of Nrf2 signaling: overlapping yet distinct gene expression profiles between Keap1 knockout and triterpenoid-treated mice
    Melinda S Yates
    Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
    Carcinogenesis 30:1024-31. 2009
    ..Additionally, analysis of pharmacologic activation suggests that Nrf2 is the primary mediator of CDDO-Im activity, though other cell-signaling targets are also modulated following an oral dose of 30 micromol/kg...
  5. pmc Disruption of Nrf2 impairs the resolution of hyperoxia-induced acute lung injury and inflammation in mice
    Narsa M Reddy
    Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21205, USA
    J Immunol 182:7264-71. 2009
    ....
  6. pmc Targeting NRF2 signaling for cancer chemoprevention
    Mi Kyoung Kwak
    College of Pharmacy, Yeungnam University, 214 1 Dae Dong, Gyeongsan si, Gyeongsangbuk do 712 749, South Korea
    Toxicol Appl Pharmacol 244:66-76. 2010
    ....
  7. pmc Nrf2: friend or foe for chemoprevention?
    Thomas W Kensler
    Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, MD 21205, USA
    Carcinogenesis 31:90-9. 2010
    ..This review provides a synopsis of KEAP1-NRF2 signaling, compares the impact of genetic versus pharmacologic activation and considers both the attributes and concerns of targeting the pathway in chemoprevention...
  8. pmc When NRF2 talks, who's listening?
    Nobunao Wakabayashi
    Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pennsylvania 15261, USA
    Antioxid Redox Signal 13:1649-63. 2010
    ..This review highlights recent observations on the molecular interactions and their functional consequences between NRF2 and the arylhydrocarbon receptor (AhR), NF-κB, p53, and Notch1 signaling pathways...
  9. pmc Aflatoxin: a 50-year odyssey of mechanistic and translational toxicology
    Thomas W Kensler
    Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
    Toxicol Sci 120:S28-48. 2011
    ....
  10. pmc Tricyclic compounds containing nonenolizable cyano enones. A novel class of highly potent anti-inflammatory and cytoprotective agents
    Tadashi Honda
    Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
    J Med Chem 54:1762-78. 2011
    ..Notably, TCE 31 reduces hepatic tumorigenesis induced with aflatoxin in rats. Further preclinical studies and detailed mechanism studies on 31 are in progress...
  11. ncbi Nrf2: control of sensitivity to carcinogens
    Stephen L Slocum
    Department of Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
    Arch Toxicol 85:273-84. 2011
    ....
  12. ncbi Present and future directions of translational research on aflatoxin and hepatocellular carcinoma. A review
    Gerald N Wogan
    Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
    Food Addit Contam Part A Chem Anal Control Expo Risk Assess 29:249-57. 2012
    ..This strategy could serve as a template for the development, validation and application of molecular and biochemical markers for other carcinogens and cancers as well as other chronic diseases resulting from environmental exposures...
  13. ncbi Aldo-keto reductase-7A protects liver cells and tissues from acetaminophen-induced oxidative stress and hepatotoxicity
    Munzir M E Ahmed
    State Key Laboratory of Stress Cell Biology and Department of Biomedical Sciences, School of Life Sciences, Xiamen University, Xiamen, China
    Hepatology 54:1322-32. 2011
    ..In contrast, depletion of Akr7a5 in vitro in cultured AML12 cells or depletion of Akr7a1 in vivo in rat liver greatly increased APAP-induced hepatotoxicity...
  14. pmc Notes from the field: "green" chemoprevention as frugal medicine
    Jed W Fahey
    Department of Pharmacology and Chemical Biology, E1352 Thomas E Starzl Biomedical Science Tower, 200 Lothrop Street, University of Pittsburgh, Pittsburgh, PA 15261
    Cancer Prev Res (Phila) 5:179-88. 2012
    ..2012 aacr...
  15. pmc Lactone metabolite common to the carcinogens dioxane, diethylene glycol, and N-nitrosomorpholine: aqueous chemistry and failure to mediate liver carcinogenesis in the F344 rat
    Niangoran Koissi
    Department of Chemistry and Biochemistry, University of Maryland Baltimore County, Baltimore, MD 21250, United States
    Chem Res Toxicol 25:1022-8. 2012
    ..In 8 rats administered 1 (1.32 g, 12 weeks) alone, no increase above background foci was detected. This study does not support compound 1 as a common carcinogen...
  16. pmc Validation of the multiple sensor mechanism of the Keap1-Nrf2 system
    Kai Takaya
    Department of Medical Biochemistry, Tohoku University Graduate School of Medicine, 2 1 Seiryo cho, Aoba ku, Sendai 980 8575, Japan
    Free Radic Biol Med 53:817-27. 2012
    ....
  17. pmc Keap1-nrf2 signaling: a target for cancer prevention by sulforaphane
    Thomas W Kensler
    Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
    Top Curr Chem 329:163-77. 2013
    ....
  18. pmc Transgenic expression of aflatoxin aldehyde reductase (AKR7A1) modulates aflatoxin B1 metabolism but not hepatic carcinogenesis in the rat
    Bill D Roebuck
    Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
    Toxicol Sci 109:41-9. 2009
    ..These results imply that the prevention of protein adducts mediated by AKR are not critical to protection against AFB(1) tumorigenicity...
  19. pmc Chemical genomics of cancer chemopreventive dithiolethiones
    Quynh T Tran
    Department of Mathematical Sciences, University of Memphis, Memphis, TN 38152, USA
    Carcinogenesis 30:480-6. 2009
    ..Together, these findings provide new insight into the actions of clinically relevant and lead dithiolethione analogues...
  20. ncbi 3H-1,2-dithiole-3-thione targets nuclear factor kappaB to block expression of inducible nitric-oxide synthase, prevents hypotension, and improves survival in endotoxemic rats
    Asok R Karuri
    W Harry Feinstone Center for Genomic Research, University of Memphis, TN 38152, USA
    J Pharmacol Exp Ther 317:61-7. 2006
    ..In conclusion, this study identifies new drug classes and targets that may improve the prevention and treatment of septic shock, as well as chronic diseases associated with the NFkappaB and iNOS pathways...
  21. ncbi Quantitative analysis and chronic dosimetry of the aflatoxin B1 plasma albumin adduct Lys-AFB1 in rats by isotope dilution mass spectrometry
    Peter F Scholl
    Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, 615 North Wolfe Street, Baltimore, Maryland 21205 2103, USA
    Chem Res Toxicol 19:44-9. 2006
    ....
  22. ncbi Potent protection against aflatoxin-induced tumorigenesis through induction of Nrf2-regulated pathways by the triterpenoid 1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole
    Melinda S Yates
    Johns Hopkins University, Baltimore, Maryland, USA
    Cancer Res 66:2488-94. 2006
    ..The unparalleled potency of CDDO-Im in vivo highlights the chemopreventive promise of targeting Nrf2 pathways with triterpenoids...
  23. ncbi Nrf2-mediated induction of cytoprotective enzymes by 15-deoxy-Delta12,14-prostaglandin J2 is attenuated by alkenal/one oxidoreductase
    Xiang Yu
    Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, MD, USA
    J Biol Chem 281:26245-52. 2006
    ..Collectively, these results demonstrate that 15d-PGJ2 can be catabolized by Aor, thereby attenuating subsequent Nrf2 signaling and possibly inflammatory and apoptotic processes also influenced by 15d-PGJ2...
  24. ncbi In vivo modulation of the Parkinsonian phenotype by Nrf2
    Neal C Burton
    Department of Environmental Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD 21205, USA
    Neurotoxicology 27:1094-100. 2006
    ..The in vivo activation of the Nrf2 pathway in the brain may be an important strategy to mitigate the effects of oxidative stress in neurodegenerative disorders and neurological disease...
  25. ncbi Cell survival responses to environmental stresses via the Keap1-Nrf2-ARE pathway
    Thomas W Kensler
    Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
    Annu Rev Pharmacol Toxicol 47:89-116. 2007
    ..This review highlights the key elements in this adaptive response to protection against acute and chronic cell injury provoked by environmental stresses...
  26. ncbi Quantification of aflatoxin-B1-N7-Guanine in human urine by high-performance liquid chromatography and isotope dilution tandem mass spectrometry
    Patricia A Egner
    Department of Environmental Health Sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland 21205, USA
    Chem Res Toxicol 19:1191-5. 2006
    ....
  27. ncbi Lysosomes and trivalent arsenic treatment in acute promyelocytic leukemia
    Sutisak Kitareewan
    Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, NH 03755, USA
    J Natl Cancer Inst 99:41-52. 2007
    ..When resistance to all-trans-retinoic acid develops, an effective treatment is arsenic trioxide (arsenite), which also induces this degradation. We investigated the mechanism of arsenite-induced PML/RAR alpha degradation...
  28. ncbi Chemopreventive promise of targeting the Nrf2 pathway
    Melinda S Yates
    Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
    Drug News Perspect 20:109-17. 2007
    ..However, additional studies are needed to characterize Keap1-Nrf2-ARE signaling in humans to further develop exceptionally potent activators of the pathway and further understand the potential consequences of altering this system...
  29. ncbi Keap1 eye on the target: chemoprevention of liver cancer
    Melinda Sue Yates
    Department of Pharmacology and Molecular Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
    Acta Pharmacol Sin 28:1331-42. 2007
    ..However, appropriately designed clinical trials will aid in this process, which can have profound impact on the incidence of HCC...
  30. ncbi Quantitative correlation of drug bioactivation and deoxyadenosine alkylation by acylfulvene
    James F Neels
    Department of Medicinal Chemistry and The Cancer Center, University of Minnesota, Minneapolis 55455, USA
    Chem Res Toxicol 20:1513-9. 2007
    ....
  31. ncbi Protective interventions to prevent aflatoxin-induced carcinogenesis in developing countries
    John D Groopman
    Department of Environmental Health Sciences, Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD 21205, USA
    Annu Rev Public Health 29:187-203. 2008
    ..Therefore, many diverse and appropriate strategies for disease prevention are needed to decrease the incidence of aflatoxin carcinogenesis in developing countries...
  32. pmc Nrf2 signaling: an adaptive response pathway for protection against environmental toxic insults
    William O Osburn
    Johns Hopkins University Bloomberg School of Public Health, Department of Environmental Health Sciences, 615 North Wolfe Street, Baltimore, MD 21205, USA
    Mutat Res 659:31-9. 2008
    ....
  33. ncbi Quantification of urinary aflatoxin B1 dialdehyde metabolites formed by aflatoxin aldehyde reductase using isotope dilution tandem mass spectrometry
    Denise N Johnson
    Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA
    Chem Res Toxicol 21:752-60. 2008
    ..This urinary detection of the alcohol products directly contributes to the goal of mass balancing the fate of the bioreactive 8,9-epoxides of AFB 1 in vivo...
  34. pmc Genetic or pharmacologic amplification of nrf2 signaling inhibits acute inflammatory liver injury in mice
    William O Osburn
    Department of Environmental Health Sciences, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
    Toxicol Sci 104:218-27. 2008
    ..Taken together, these results clearly illustrate that targeted cytoprotection of hepatocytes through Nrf2 signaling during inflammation prevents the amplification of inflammatory responses in the liver...
  35. pmc A novel acetylenic tricyclic bis-(cyano enone) potently induces phase 2 cytoprotective pathways and blocks liver carcinogenesis induced by aflatoxin
    Karen Liby
    Dartmouth Medical School, Hanover, NH 03755, USA
    Cancer Res 68:6727-33. 2008
    ....
  36. pmc Genetic or pharmacologic activation of Nrf2 signaling fails to protect against aflatoxin genotoxicity in hypersensitive GSTA3 knockout mice
    Kevin H Kensler
    Johns Hopkins Bloomberg School of Public Health, 615 N Wolfe Street, Baltimore, Maryland 21205
    Toxicol Sci 139:293-300. 2014
    ..The inability to rescue GSTA3 knockout mice from aflatoxin genotoxicity through the Nrf2 transcriptional program indicates that Gsta3 is unilaterally responsible for the detoxication of aflatoxin in mice. ..

Research Grants30

  1. Gender Disparity in Bladder Cancer and Chemopreventive Intervention
    Yuesheng Zhang; Fiscal Year: 2013
    ..Impact: The proposed studies are expected to lead to the elucidation of the molecular basis of the gender disparity in BC and the development of new strategy for effective prevention of this disease. ..