Animals have evolved defense systems for surviving in a chemically diverse environment. Such systems should demonstrate plasticity, such as adaptive immunity, enabling a response to even unknown chemicals. The antioxidant transcription factor Nrf2 is activated in response to various electrophiles and induces cytoprotective enzymes that detoxify them. We report here the discovery of a multiple sensing mechanism for Nrf2 activation using zebrafish and 11 Nrf2-activating compounds. First, we showed that six of the compounds tested specifically target Cys-151 in Keap1, the ubiquitin ligase for Nrf2, while two compounds target Cys-273. Second, in addition to Nrf2 and Keap1, a third factor was deemed necessary for responding to three of the compounds. Finally, we isolated a zebrafish mutant defective in its response to seven compounds but not in response to the remaining four. These results led us to categorize Nrf2 activators into six classes and hypothesize that multiple sensing allows enhanced plasticity in the system.Nrf2 is a transcription factor that transactivates cytoprotective genes through a common DNA regulatory element, called the antioxidant response element or electrophile response element (18, 24). Nrf2 target genes are multifarious and encode phase 2 detoxifying enzymes, antioxidant proteins, enzymes for glutathione biosynthesis, ABC transporters, scavenger receptors, transcription factors, proteases, chaperone proteins, and so forth (23). Under basal conditions, Nrf2 is rapidly degraded by proteasomes, and little induction of target genes is observed. This degradation is controlled by Keap1, an Nrf2-specific adaptor protein for the Cul3 ubiquitin ligase complex (12,20). Nrf2-activating compounds block Keap1-dependent Nrf2 ubiquitination, leading to the stabilization and nuclear translocation of Nrf2 and subsequent induction of Nrf2 target genes.A number of Nrf2 activators have been found but, interestingly, no common structures were identified among them (23). Talalay and coworkers classified Nrf2-activating compounds into the following 10 distinct classes based on their chemical structures (7): diphenols, Michael reaction acceptors, isothiocyanates, thiocarbamates, trivalent arsenicals, 1,2-dithiole-3-thiones, hydroperoxides, vicinal dimercaptans, heavy metals, and polyenes. A current pursuit is unraveling how cells detect these chemical compounds and transduce their signals into the activation of Nrf2. Keap1 has many highly reactive cysteine residues that have the potential to sense electrophilic Nrf2 activators by forming covalent adducts with them. We and others have therefore proposed the model that Nrf2-activating compounds directly modify the sulfhydryl groups of Keap1 cysteines by oxidation, reduction, or alkylation, which alters the conformation of Keap1 and ceases the ubiquitination of Nrf2 (7,24). In fact, mass spectrometry (MS) studies revealed that some Nrf2-activating compounds can covalently react with cysteines in mouse or human Keap1. For example, dexamethasone 21-mesylate with ; iodo...

Obesity increases the risk of cancers, including hepatocellular carcinomas (HCC). However, the precise molecular mechanisms through which obesity promotes HCC development are still unclear. Recent studies have shown that gut microbiota may influence liver diseases by transferring its metabolites and components. Here, we show that the hepatic translocation of obesity-induced lipoteichoic acid (LTA), a Gram-positive gut microbial component, promotes HCC development by creating a tumor-promoting microenvironment. LTA enhances the senescenceassociated secretory phenotype (SASP) of hepatic stellate cells (HSC) collaboratively with an obesityinduced gut microbial metabolite, deoxycholic acid, to upregulate the expression of SASP factors and COX2 through Toll-like receptor 2. Interestingly, COX2-mediated prostaglandin E 2 (PGE 2) production suppresses the antitumor immunity through a PTGER4 receptor, thereby contributing to HCC progression. Moreover, COX2 overexpression and excess PGE 2 production were detected in HSCs in human HCCs with noncirrhotic, nonalcoholic steatohepatitis (NASH), indicating that a similar mechanism could function in humans. SIGNIFICANCE: We showed the importance of the gut-liver axis in obesity-associated HCC. The gut microbiota-driven COX2 pathway produced the lipid mediator PGE 2 in senescent HSCs in the tumor microenvironment, which plays a pivotal role in suppressing antitumor immunity, suggesting that PGE 2 and its receptor may be novel therapeutic targets for noncirrhotic NASH-associated HCC.

The outcome of treatment-refractory and/or relapsed pediatric T cell acute lymphoblastic leukemia (T-ALL) is extremely poor, and the genetic basis for this is not well understood. Here we report comprehensive profiling of 121 cases of pediatric T-ALL using transcriptome and/or targeted capture sequencing, through which we identified new recurrent gene fusions involving SPI1 (STMN1-SPI1 and TCF7-SPI1). Cases positive for fusions involving SPI1 (encoding PU.1), accounting for 3.9% (7/181) of the examined pediatric T-ALL cases, showed a double-negative (DN; CD4CD8) or CD8 single-positive (SP) phenotype and had uniformly poor overall survival. These cases represent a subset of pediatric T-ALL distinguishable from the known T-ALL subsets in terms of expression of genes involved in T cell precommitment, establishment of T cell identity, and post-β-selection maturation and with respect to mutational profile. PU.1 fusion proteins retained transcriptional activity and, when constitutively expressed in mouse stem/progenitor cells, induced cell proliferation and resulted in a maturation block. Our findings highlight a unique role of SPI1 fusions in high-risk pediatric T-ALL.

To search for genes that promote hematopoietic development from human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs), we overexpressed several known hematopoietic regulator genes in hESC/iPSC-derived CD34 ؉ CD43 ؊ endothelial cells (ECs) enriched in hemogenic endothelium (HE). Among the genes tested, only Sox17, a gene encoding a transcription factor of the SOX family, promoted cell growth and supported expansion of CD34 ؉ CD43 ؉ CD45 ؊/low cells expressing the HE marker VE-cadherin. SOX17 was expressed at high levels in CD34 ؉ CD43 ؊ ECs compared with low levels in CD34 ؉ CD43 ؉ CD45 ؊ pre-hematopoietic progenitor cells (pre-HPCs) and CD34 ؉ CD43 ؉ CD45 ؉ HPCs. Sox17-overexpressing cells formed semiadherent cell aggregates and generated few hematopoietic progenies. However, they retained hemogenic potential and gave rise to hematopoietic progenies on inactivation of