Enantioselective synthesis of chiral amides by carbene insertion into amide N-H bond.

Chiral amides are important structure in many natural products and pharmaceuticals, yet their efficient synthesis from simple amide feedstock remains challenge due to its weak Lewis basicity. Herein, we describe our study of the enantioselective synthesis of chiral amides by N-alkylation of primary amides taking advantage of an achiral rhodium and chiral squaramide co-catalyzed carbene N-H insertion reaction. This method features mild condition, rapid reaction rate (in all cases 1 min) and a wide substrate scope with high yield and excellent enantioselectivity. Further product transformations show the synthetic potential of this reaction. Mechanistic studies reveal that the non-covalent interactions between the catalyst and reaction intermediate play a critical role in enantiocontrol.

Heterogeneity of Phase II Enzyme Ligands on Controlling the Progression of Human Gastric Cancer Organoids as Stem Cell Therapy Model.

Gastric cancer (GC) organoids are frequently used to examine cell proliferation and death as well as cancer development. Invasion/migration assay, xenotransplantation, and reactive oxygen species (ROS) production were used to examine the effects of antioxidant drugs, including perillaldehyde (PEA), cinnamaldehyde (CA), and sulforaphane (SFN), on GC. PEA and CA repressed the proliferation of human GC organoids, whereas SFN enhanced it. Caspase 3 activities were also repressed on treatment with PEA and CA. Furthermore, the tumor formation and invasive activities were repressed on treatment with PEA and CA, whereas they were enhanced on treatment with SFN. These results in three-dimensional (3D)-GC organoids showed the different cancer development of phase II enzyme ligands in 2D-GC cells. ROS production and the expression of TP53, nuclear factor erythroid 2-related factor (NRF2), and Jun dimerization protein 2 were also downregulated on treatment with PEA and CA, but not SFN. NRF2 knockdown reversed the effects of these antioxidant drugs on the invasive activities of the 3D-GC organoids. Moreover, ROS production was also inhibited by treatment with PEA and CA, but not SFN. Thus, NRF2 plays a key role in the differential effects of these antioxidant drugs on cancer progression in 3D-GC organoids. PEA and CA can potentially be new antitumorigenic therapeutics for GC.

Jdp2 is a spatiotemporal transcriptional activator of the AhR via the Nrf2 gene battery.

BACKGROUND: Crosstalk between the aryl hydrocarbon receptor (AhR) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signaling is called the "AhR-Nrf2 gene battery", which works synergistically in detoxification to support cell survival. Nrf2-dependent phase II gene promoters are controlled by coordinated recruitment of the AhR to adjacent dioxin responsive element (DRE) and Nrf2 recruitment to the antioxidative response element (ARE). The molecular interaction between AhR and Nrf2 members, and the regulation of each target, including phase I and II gene complexes, and their mediators are poorly understood. METHODS: Knockdown and forced expression of AhR-Nrf2 battery members were used to examine the molecular interactions between the AhR-Nrf2 axis and AhR promoter activation. Sequential immunoprecipitation, chromatin immunoprecipitation, and histology were used to identify each protein complex recruited to their respective cis-elements in the AhR promoter. Actin fiber distribution, cell spreading, and invasion were examined to identify functional differences in the AhR-Jdp2 axis between wild-type and Jdp2 knockout cells. The possible tumorigenic role of Jdp2 in the AhR-Nrf2 axis was examined in mutant Kras-Trp53-driven pancreatic tumors. RESULTS: Crosstalk between AhR and Nrf2 was evident at the transcriptional level. The AhR promoter was activated by phase I ligands such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) through the AhR-Jdp2-Nrf2 axis in a time- and spatial transcription-dependent manner. Jdp2 was a bifunctional activator of DRE- and ARE-mediated transcription in response to TCDD. After TCDD exposure, Jdp2 activated the AhR promoter at the DRE and then moved to the ARE where it activated the promoter to increase reactive oxygen species (ROS)-mediated functions such as cell spreading and invasion in normal cells, and cancer regression in mutant Kras-Trp53-driven pancreatic tumor cells. CONCLUSIONS: Jdp2 plays a critical role in AhR promoter activation through the AhR-Jdp2-Nrf2 axis in a spatiotemporal manner. The AhR functions to maintain ROS balance and cell spreading, invasion, and cancer regression in a mouse model of mutant Kras-Trp53 pancreatic cancer. These findings provide new insights into the roles of Jdp2 in the homeostatic regulation of oxidative stress and in the antioxidation response in detoxification, inflammation, and cancer progression.

Enantioselective Synthesis of Chiral Amides by a Phosphoric Acid Catalyzed Asymmetric Wolff Rearrangement.

The enantioselective addition of potent nucleophiles to ketenes poses challenges due to competing background reactions and poor stereocontrol. Herein, we present a method for enantioselective phosphoric acid catalyzed amination of ketenes generated from α-aryl-α-diazoketones. Upon exposure to visible light, the diazoketones undergo Wolff rearrangement to generate ketenes. The phosphoric acid not only accelerates ketene capture by amines to form a single configuration of aminoenol intermediates but also promotes an enantioselective proton-transfer reaction of the intermediates to yield the products. Mechanistic studies elucidated the reaction pathway and explained how the catalyst expedited the transformation and controlled the enantioselectivity.

Independent Signaling of Hepatoma Derived Growth Factor and Tumor Necrosis Factor-Alpha in Human Gastric Cancer Organoids Infected by Helicobacter pylori.

We prepared three-dimensional (3-D) organoids of human stomach cancers and examined the correlation between the tumorigenicity and cytotoxicity of Helicobacter pylori (H. pylori). In addition, the effects of hepatoma-derived growth factor (HDGF) and tumor necrosis factor (TNFα) on the growth and invasion activity of H. pylori-infected gastric cancer organoids were examined. Cytotoxin-associated gene A (CagA)-green fluorescence protein (GFP)-labeled H. pylori was used to trace the infection in gastric organoids. The cytotoxicity of Cag encoded toxins from different species of H. pylori did not affect the proliferation of each H. pylori-infected cancer organoid. To clarify the role of HDGF and TNFα secreted from H. pylori-infected cancer organoids, we prepared recombinant HDGF and TNFα and measured the cytotoxicity and invasion of gastric cancer organoids. HDGF controlled the growth of each organoid in a species-specific manner of H. pylori, but TNFα decreased the cell viability in H. pylori-infected cancer organoids. Furthermore, HDGF controlled the invasion activity of H. pylori-infected cancer organoid in a species-dependent manner. However, TNFα decreased the invasion activities of most organoids. We found different signaling of cytotoxicity and invasion of human gastric organoids in response to HDGF and TNFα during infection by H. pylori. Recombinant HDGF and TNFα inhibited the development and invasion of H. pylori-infected gastric cancer differently. Thus, we propose that HDGF and TNFα are independent signals for development of H. pylori-infected gastric cancer. The signaling of growth factors in 3-D organoid culture systems is different from those in two-dimensional cancer cells.

A Spiro Phosphamide Catalyzed Enantioselective Proton Transfer of Ylides in a Free Carbene Insertion into N-H Bonds.

Free carbene readily causes multiple side reactions due to its high energy, thus its asymmetric transformation is very difficult. We present here our findings of high-pKa Brønsted acid catalysts that enable free carbene insertion into N-H bonds of amines to prepare chiral α-amino acid derivatives with high enantioselectivity. Under irradiation with visible light, diazo compounds produce high-energy free carbenes that are captured by amines to form free ylide intermediates, and then the newly designed high-pKa Brønsted acids, chiral spiro phosphamides, promote the proton transfer of ylides to afford the products. Computational and kinetic studies uncover the principle for the rational design of proton-transfer catalysts and explain how the catalysts accelerate this transformation and provide stereocontrol.

Stem Cell Biomarkers and Tumorigenesis in Gastric Cancer.

Stomach cancer has a high mortality, which is partially caused by an absence of suitable biomarkers to allow detection of the initiation stages of cancer progression. Thus, identification of critical biomarkers associated with gastric cancer (GC) is required to advance its clinical diagnoses and treatment. Recent studies using tracing models for lineage analysis of GC stem cells indicate that the cell fate decision of the gastric stem cells might be an important issue for stem cell plasticity. They include leucine-rich repeat-containing G-protein-coupled receptor 5 (Lgr5+), Cholecystokinin receptor 2 (Cckr2+), and axis inhibition protein 2 (Axin2+) as the stem cell markers in the antrum, Trefoil Factor 2 (TFF2+), Mist1+ stem cells, and Troy+ chief cells in the corpus. By contrast, Estrogen receptor 1 (eR1), Leucine-rich repeats and immunoglobulin-like domains 1 (Lrig1), SRY (sex determining region Y)-box 2 (Sox2), and B lymphoma Mo-MLV insertion region 1 homolog (Bmi1) are rich in both the antrum and corpus regions. These markers might help to identify the cell-lineage identity and analyze the plasticity of each stem cell population. Thus, identification of marker genes for the development of GC and its environment is critical for the clinical application of cancer stem cells in the prevention of stomach cancers.

Biomarkers of Cancer Stem Cells for Experimental Research and Clinical Application.

The use of biomarkers in cancer diagnosis, therapy, and prognosis has been highly effective over several decades. Studies of biomarkers in cancer patients pre- and post-treatment and during cancer progression have helped identify cancer stem cells (CSCs) and their related microenvironments. These analyses are critical for the therapeutic application of drugs and the efficient targeting and prevention of cancer progression, as well as the investigation of the mechanism of the cancer development. Biomarkers that characterize CSCs have thus been identified and correlated to diagnosis, therapy, and prognosis. However, CSCs demonstrate elevated levels of plasticity, which alters their functional phenotype and appearance by interacting with their microenvironments, in response to chemotherapy and radiotherapeutics. In turn, these changes induce different metabolic adaptations of CSCs. This article provides a review of the most frequently used CSCs and stem cell markers.

Generation of Human Stomach Cancer iPSC-Derived Organoids Induced by Helicobacter pylori Infection and Their Application to Gastric Cancer Research.

There is considerable cellular diversity in the human stomach, which has helped to clarify cell plasticity in normal development and tumorigenesis. Thus, the stomach is an interesting model for understanding cellular plasticity and for developing prospective anticancer therapeutic agents. However, many questions remain regarding the development of cancers in vivo and in vitro in two- or three-dimensional (2D/3D) cultures, as well as the role of Helicobacter pylori (H. p.) infection. Here, we focus on the characteristics of cancer stem cells and their derived 3D organoids in culture, including the formation of stem cell niches. We define the conditions required for such organoid culture in vitro and examine the ability of such models for testing the use of anticancer agents. We also summarize the signaling cascades and the specific markers of stomach-cancer-derived organoids induced by H. p. infection, and their stem cell niches.

Dimethyl sulfoxide stimulates the AhR-Jdp2 axis to control ROS accumulation in mouse embryonic fibroblasts.

The aryl hydrocarbon receptor (AhR) is a ligand-binding protein that responds to environmental aromatic hydrocarbons and stimulates the transcription of downstream phase I enzyme-related genes by binding the cis element of dioxin-responsive elements (DREs)/xenobiotic-responsive elements. Dimethyl sulfoxide (DMSO) is a well-known organic solvent that is often used to dissolve phase I reagents in toxicology and oxidative stress research experiments. In the current study, we discovered that 0.1% DMSO significantly induced the activation of the AhR promoter via DREs and produced reactive oxygen species, which induced apoptosis in mouse embryonic fibroblasts (MEFs). Moreover, Jun dimerization protein 2 (Jdp2) was found to be required for activation of the AhR promoter in response to DMSO. Coimmunoprecipitation and chromatin immunoprecipitation studies demonstrated that the phase I-dependent transcription factors, AhR and the AhR nuclear translocator, and phase II-dependent transcription factors such as nuclear factor (erythroid-derived 2)-like 2 (Nrf2) integrated into DRE sites together with Jdp2 to form an activation complex to increase AhR promoter activity in response to DMSO in MEFs. Our findings provide evidence for the functional role of Jdp2 in controlling the AhR gene via Nrf2 and provide insights into how Jdp2 contributes to the regulation of ROS production and the cell spreading and apoptosis produced by the ligand DMSO in MEFs.

Therapeutic Strategies Targeting Tumor Suppressor Genes in Pancreatic Cancer.

The high mortality of pancreatic cancer is attributed to the insidious progression of this disease, which results in a delayed diagnosis and advanced disease stage at diagnosis. More than 35% of patients with pancreatic cancer are in stage III, whereas 50% are in stage IV at diagnosis. Thus, understanding the aggressive features of pancreatic cancer will contribute to the resolution of problems, such as its early recurrence, metastasis, and resistance to chemotherapy and radiotherapy. Therefore, new therapeutic strategies targeting tumor suppressor gene products may help prevent the progression of pancreatic cancer. In this review, we discuss several recent clinical trials of pancreatic cancer and recent studies reporting safe and effective treatment modalities for patients with advanced pancreatic cancer.

Deletion of Jdp2 enhances Slc7a11 expression in Atoh-1 positive cerebellum granule cell progenitors in vivo.

BACKGROUND: The cerebellum is the sensitive region of the brain to developmental abnormalities related to the effects of oxidative stresses. Abnormal cerebellar lobe formation, found in Jun dimerization protein 2 (Jdp2)-knockout (KO) mice, is related to increased antioxidant formation and a reduction in apoptotic cell death in granule cell progenitors (GCPs). Here, we aim that Jdp2 plays a critical role of cerebellar development which is affected by the ROS regulation and redox control. OBJECTIVE: Jdp2-promoter-Cre transgenic mouse displayed a positive signal in the cerebellum, especially within granule cells. Jdp2-KO mice exhibited impaired development of the cerebellum compared with wild-type (WT) mice. The antioxidation controlled gene, such as cystine-glutamate transporter Slc7a11, might be critical to regulate the redox homeostasis and the development of the cerebellum. METHODS: We generated the Jdp2-promoter-Cre mice and Jdp2-KO mice to examine the levels of Slc7a11, ROS levels and the expressions of antioxidation related genes were examined in the mouse cerebellum using the immunohistochemistry. RESULTS: The cerebellum of Jdp2-KO mice displayed expression of the cystine-glutamate transporter Slc7a11, within the internal granule layer at postnatal day 6; in contrast, the WT cerebellum mainly displayed Sla7a11 expression in the external granule layer. Moreover, development of the cerebellar lobes in Jdp2-KO mice was altered compared with WT mice. Expression of Slc7a11, Nrf2, and p21Cip1 was higher in the cerebellum of Jdp2-KO mice than in WT mice. CONCLUSION: Jdp2 is a critical regulator of Slc7a11 transporter during the antioxidation response, which might control the growth, apoptosis, and differentiation of GCPs in the cerebellar lobes. These observations are consistent with our previous study in vitro.

Redox control in the pathophysiology of influenza virus infection.

Triggered in response to external and internal ligands in cells and animals, redox homeostasis is transmitted via signal molecules involved in defense redox mechanisms through networks of cell proliferation, differentiation, intracellular detoxification, bacterial infection, and immune reactions. Cellular oxidation is not necessarily harmful per se, but its effects depend on the balance between the peroxidation and antioxidation cascades, which can vary according to the stimulus and serve to maintain oxygen homeostasis. The reactive oxygen species (ROS) that are generated during influenza virus (IV) infection have critical effects on both the virus and host cells. In this review, we outline the link between viral infection and redox control using IV infection as an example. We discuss the current state of knowledge on the molecular relationship between cellular oxidation mediated by ROS accumulation and the diversity of IV infection. We also summarize the potential anti-IV agents available currently that act by targeting redox biology/pathophysiology.

Author Correction: Jdp2-deficient granule cell progenitors in the cerebellum are resistant to ROS-mediated apoptosis through xCT/Slc7a11 activation.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Jdp2-deficient granule cell progenitors in the cerebellum are resistant to ROS-mediated apoptosis through xCT/Slc7a11 activation.

The Jun dimerization protein 2 (Jdp2) is expressed predominantly in granule cell progenitors (GCPs) in the cerebellum, as was shown in Jdp2-promoter-Cre transgenic mice. Cerebellum of Jdp2-knockout (KO) mice contains lower number of Atoh-1 positive GCPs than WT. Primary cultures of GCPs from Jdp2-KO mice at postnatal day 5 were more resistant to apoptosis than GCPs from wild-type mice. In Jdp2-KO GCPs, the levels of both the glutamate‒cystine exchanger Sc7a11 and glutathione were increased; by contrast, the activity of reactive oxygen species (ROS) was decreased; these changes confer resistance to ROS-mediated apoptosis. In the absence of Jdp2, a complex of the cyclin-dependent kinase inhibitor 1 (p21Cip1) and Nrf2 bound to antioxidant response elements of the Slc7a11 promoter and provide redox control to block ROS-mediated apoptosis. These findings suggest that an interplay between Jdp2, Nrf2, and p21Cip1 regulates the GCP apoptosis, which is one of critical events for normal development of the cerebellum.