The overall goals of the proposed studies are to assess the underlying mechanisms and the functional significance of induction of the phase 2 response by cancer chemopreventive agents. An extraordinary variety of chemical agents protect animals against the neoplastic effects of many different types of carcinogens. Many of these chemoprotectors exert their anticarcinogenic effects by selectively inducing (by enhanced transcription) phase 2, antioxidative and anti-inflammatory genes that serve to detoxify the biomolecule damaging forms of electrophiles and oxidants, thereby enhancing cell survival. Most of these protective genes are induced through a common enhancer, the Antioxidant Response Element (ARE), by interactions with the transcription factor Nrf2. Nrf2, in turn, is sequestered by the represser Keapl, which regulates the fate of Nrf2 in cells. In this project we seek to use molecular, genetic and chemical approaches to test the hypothesis that Keapl is the major sensor for agents that activate the Nrf2-dependent cytoprotective genes.
Aim 1 is designed to characterize the structural properties and reaction kinetics of Keapl, as well as the spatio-temporal dynamics of Keapl-Nrf2 interactions in vitro and in living cells by fluorescence resonance energy transfer spectroscopy. Subequent aims will investigate the downstream consequences of Keapl-Nrf2 activation.
Aim 2 will define the role of this pathway in modulating oxidative stress in vitro and in vivo through the use of models employing wild-type, Nrf2-disrupted, Keapl-disrupted and double knockout cells and mice.
Aim 3 will use these genetic models to probe the pharmacodynamic action of a exceptionally potent class of chemopreventive agents, triterpenoids, and to assess the central role of Nrf2 in their actions.
Aim 4 will characterize the interactions of Nrf2 signaling with other pathways affecting adpative responses affecting cell fate. In particular, cross regulation of the aryl hydrocarbon receptor and the Notch signaling pathways will be probed and functional consequences of transactivation assessed. These studies will firmly establish the role of induction of the phase 2 response in chemoprevention. Knowledge of the mechanisms by which chemopreventive agents interact with Keapl as a sentinel sensor, thereby facilitating signaling by Nrf2 for induction of cell survival genes, will facilitate the identification and utilization of more selective compounds and enhance their effectiveness in humans.
|Yang, Li; Palliyaguru, Dushani L; Kensler, Thomas W (2016) Frugal chemoprevention: targeting Nrf2 with foods rich in sulforaphane. Semin Oncol 43:146-153|
|Slocum, Stephen L; Skoko, John J; Wakabayashi, Nobunao et al. (2016) Keap1/Nrf2 pathway activation leads to a repressed hepatic gluconeogenic and lipogenic program in mice on a high-fat diet. Arch Biochem Biophys 591:57-65|
|Chartoumpekis, Dionysios V; Palliyaguru, Dushani L; Wakabayashi, Nobunao et al. (2015) Notch intracellular domain overexpression in adipocytes confers lipodystrophy in mice. Mol Metab 4:543-50|
|Wakabayashi, Nobunao; Chartoumpekis, Dionysios V; Kensler, Thomas W (2015) Crosstalk between Nrf2 and Notch signaling. Free Radic Biol Med 88:158-167|
|Johnson, Natalie M; Egner, Patricia A; Baxter, Victoria K et al. (2014) Complete protection against aflatoxin B(1)-induced liver cancer with a triterpenoid: DNA adduct dosimetry, molecular signature, and genotoxicity threshold. Cancer Prev Res (Phila) 7:658-65|
|Skoko, John J; Wakabayashi, Nobunao; Noda, Kentaro et al. (2014) Loss of Nrf2 in mice evokes a congenital intrahepatic shunt that alters hepatic oxygen and protein expression gradients and toxicity. Toxicol Sci 141:112-9|
|Zhang, Yongshu; Xia, Jixiang; Li, Qinglin et al. (2014) NRF2/long noncoding RNA ROR signaling regulates mammary stem cell expansion and protects against estrogen genotoxicity. J Biol Chem 289:31310-8|
|Kensler, Kevin H; Slocum, Stephen L; Chartoumpekis, Dionysios V et al. (2014) Genetic or pharmacologic activation of Nrf2 signaling fails to protect against aflatoxin genotoxicity in hypersensitive GSTA3 knockout mice. Toxicol Sci 139:293-300|
|Wakabayashi, Nobunao; Skoko, John J; Chartoumpekis, Dionysios V et al. (2014) Notch-Nrf2 axis: regulation of Nrf2 gene expression and cytoprotection by notch signaling. Mol Cell Biol 34:653-63|
|Kensler, Thomas W; Egner, Patricia A; Agyeman, Abena S et al. (2013) Keap1-nrf2 signaling: a target for cancer prevention by sulforaphane. Top Curr Chem 329:163-77|
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