Search

Background & Aims: Hepatitis B virus (HBV) infection is a major health concern worldwide. Although currently used nucleos(t)ide analogs efficiently inhibit viral replication, viral proteins transcribed from the episomal viral covalently closed circular DNA (cccDNA) minichromosome continue to be expressed long-term. Because high viral RNA or antigen loads may play a biological role during this chronicity, the elimination of viral products is an ultimate goal of HBV treatment. HBV regulatory protein X (HBx) was recently found to promote transcription of cccDNA with degradation of Smc5/6 through the interaction of HBx with the host protein DDB1. Here, this protein–protein interaction was considered as a new molecular target of HBV treatment. Methods: To identify candidate compounds that target the HBx–DDB1 interaction, a newly constructed split luciferase assay system was applied to comprehensive compound screening. The effects of the identified compounds on HBV transcription and cccDNA maintenance were determined using HBV minicircle DNA, which mimics HBV cccDNA, and the natural HBV infection model of human primary hepatocytes. Results: We show that nitazoxanide (NTZ), a thiazolide anti-infective agent that has been approved by the FDA for protozoan enteritis, efficiently inhibits the HBx–DDB1 protein interaction. NTZ significantly restores Smc5 protein levels and suppresses viral transcription and viral protein production in the HBV minicircle system and in human primary hepatocytes naturally infected with HBV. Conclusions: These results indicate that NTZ, which targets an HBV-related viral–host protein interaction, may be a promising new therapeutic agent and a step toward a functional HBV cure. Keywords: Drug Screening, Minicircle, Primary Hepatocyte Infection

In the original publication [...]

To accurately measure the surface tension of liquid titanium free of contamination from chemical reaction with the supporting materials and dissolution of atmospheric oxygen, the measurement was performed by using electromagnetic levitation (EML) and electrostatic levitation (ESL) in consideration of the influence of oxygen partial pressure of the measurement atmosphere, PO2. When liquid titanium was maintained at 2000 K under Ar–He gas with PO2 of 10 Pa flowing at 2 L·min−1 using EML, the surface tension decreased with time due to the dissolution of atmospheric oxygen into the sample. When the PO2 of the gas was decreased to 10−2 Pa, the oxygen content and the surface tension were confirmed to not vary, even after 120 min. Even though PO2 further decreased to 10−11 Pa under Ar–He–H2 gas, the surface tension slightly increased with time due to gas phase equilibrium between H2 and H2O that allowed for a continuous dissolution of atmospheric oxygen into the liquid titanium. The surface tension of liquid titanium measured by ESL, which prevents contamination of the sample from supporting materials and the high 10−5 Pa vacuum inhibits the dissolution of oxygen, showed almost the same value as that measured under Ar–He gas at PO2 of 10−2 Pa by EML. From the measurement results of EML and ESL, the surface tension of the 99.98 mass % pure liquid titanium, free from any contaminations from chemical reactions, with the supporting material and dissolved oxygen was expressed as σ99.98%=1613−0.2049T−1941 (10−3 N·m−1).

Circular RNA (circRNA) is a type of non-coding RNA that forms a covalently closed continuous loop. The expression pattern of circRNA varies among cell types and tissues, and many circRNAs are aberrantly expressed in various cancers. Aberrantly expressed circRNAs have been shown to play crucial roles in carcinogenesis, functioning as microRNA sponges or new templates for protein translation. Recent research has shown that circRNAs are enriched in exosomes. Exosomes are secretory vesicles that mediate intercellular communication through the delivery of cargo, including proteins, lipids, DNA, and RNA. Exosome-mediated crosstalk between cancer cells and the tumor microenvironment promotes the epithelial-mesenchymal transition, angiogenesis, and immune escape, and thus may contribute to cancer invasion and metastasis. In this review, we discuss the biological functions of exosomal circRNAs and their significance in cancer progression. Additionally, we discuss the potential clinical applications of exosomal circRNAs as biomarkers and in cancer therapy.

Aging and inflammation: aging cells express interferon-stimulated genes in a non-canonical pathway Aging cells express many kinds of inflammation-related genes called SASP (senescence-associated secretary-phenotype), which are involved in aging-associated phenotypes. However, the underlying molecular mechanisms how such inflammatory gene expression is induced in aging cells are unclear. A team led by Motoyuki Otsuka at the University of Tokyo found that using senescent human fibroblasts interferon-stimulated genes do not express in a canonical interferon-related intracellular signaling pathway. Normally, interferon-stimulated genes are expressed through the phosphorylation of STAT proteins triggered by interferon stimulation. In contrast, in senescent cells, interferon-stimulated genes were highly expressed without interferon stimulation and the representative STAT phosphorylation was not induced. These findings indicate that the interferon-stimulated genes in aging cells are expressed in a mechanism different from a canonical interferon-related pathway. Further research into these phenomena may develop a way to intervene the senescence-associated phenotypes in aging.

Abstract Telomere maintenance by telomerase activity supports the infinite growth of cancer cells. MST-312, a synthetic telomerase inhibitor, gradually shortens telomeres at non-acute lethal doses and eventually induces senescence and apoptosis of telomerase-positive cancer cells. Here we report that MST-312 at higher doses works as a dual inhibitor of telomerase and DNA topoisomerase II and exhibits acute anti-proliferative effects on cancer cells and xenografted tumours in vivo. Our cell-based chemical fingerprinting approach revealed that cancer cells with shorter telomeres and lower expression of lamin A, a nuclear architectural protein, exhibited higher sensitivity to the acute deleterious effects of MST-312, accompanied by formation of telomere dysfunction-induced foci and DNA double-strand breaks. Telomere elongation and lamin A overexpression attenuated telomeric and non-telomeric DNA damage, respectively, and both conferred resistance to apoptosis induced by MST-312 and other DNA damaging anticancer agents. These observations suggest that sufficient pools of telomeres and a nuclear lamina component contribute to the cellular robustness against DNA damage induced by therapeutic treatment in human cancer cells.

Drosophila is an excellent model to study both development and tumorigenesis. Here the authors uncover an innate mechanism for a steroid hormone-induced block to tumorigenesis during metamorphosis of Drosophila.

Cancer cells adopt multiple strategies to escape tumor surveillance by the host immune system and aberrant amino acid metabolism in the tumor microenvironment suppresses the immune system. Among the amino acid‐metabolizing enzymes is an L‐amino‐acid oxidase called interleukin‐4 induced 1 (IL4I1), which depletes essential amino acids in immune cells and is associated with a poor prognosis in various cancer types. Although IL4I1 is involved in immune metabolism abnormalities, its effect on the therapeutic efficacy of immune checkpoint inhibitors is unknown. In this study, we established murine melanoma cells overexpressing IL4I1 and investigated their effects on the intratumor immune microenvironment and the antitumor efficacy of anti‐programmed death‐ligand 1 (PD‐L1) antibodies (Abs) in a syngeneic mouse model. As a result, we found that IL4I1‐overexpressing B16‐F10‐derived tumors showed resistance to anti‐PD‐L1 Ab therapy. Transcriptome analysis revealed that immunosuppressive genes were globally upregulated in the IL4I1‐overexpressing tumors. Consistently, we showed that IL4I1‐overexpressing tumors exhibited an altered subset of lymphoid cells and particularly significant suppression of cytotoxic T cell infiltration compared to mock‐infected B16‐F10‐derived tumors. After treatment with anti‐PD‐L1 Abs, we also found a more prominent elevation of tumor‐associated macrophage (TAM) marker, CD68, in the IL4I1‐overexpressing tumors than in the mock tumors. Consistently, we confirmed an enhanced TAM infiltration in the IL4I1‐overexpressing tumors and a functional involvement of TAMs in the tumor growth. These observations indicate that IL4I1 reprograms the tumor microenvironment into an immunosuppressive state and thereby confers resistance to anti‐PD‐L1 Abs. [ABSTRACT FROM AUTHOR]

The surface tension of liquid zirconium was measured using the oscillating droplet method with electromagnetic levitation while considering the effect of oxygen dissolution from the measurement atmosphere. When liquid zirconium was maintained at approximately 2300 K under the flow of an Ar-He gas at 2 L·min-1 with an oxygen partial pressure (Po2) of 10-2 Pa, the oxygen content (CO) remained stable even after 15 min, resulting in a constant surface tension. However, under the flow of an Ar-He-H2-CO2 gas, CO increased with time even when Po2 was 10-4 and 10-6 Pa. This was attributed to the gasphase equilibrium between H2 and CO2, which facilitated the continuous dissolution of atmospheric oxygen into liquid zirconium. Liquid zirconium was free from any contaminations due to chemical reactions with the supporting material or atmospheric oxygen, and its surface tension was expressed as σ = 1495 - 0.1153 (T - 2128) [10-3 N·m-1]. [ABSTRACT FROM AUTHOR]

Influences of temperature and oxygen adsorption on the surface tension of liquid silicon were investigated by the oscillating droplet method using the electromagnetic levitation technique. Oxygen partial pressure in the vicinity of the liquid surface was controlled by the theoretically derived Ratto, Ricci, and Arato model and the effectiveness of which was experimentally confirmed from the in situ observation of oxidation and reduction behaviors of the droplet surface in this study. The surface tension of liquid silicon was decreased with increasing oxygen partial pressure in the vicinity of the liquid surface due to oxygen adsorption at low temperature, whereas the surface tension converged to a pure state value at high temperature regardless of the oxygen partial pressure due to a decrease in the equilibrium constant of oxygen adsorption reaction. As a result, "boomerang shape" temperature dependence of surface tension was observed; the gradient of the temperature dependence of surface tension was gradually increased with elevating temperature and then became a constant value at high temperature. The influences of oxygen adsorption and temperature on surface tension were successfully derived from the measurement result by using the Szyszkowski equation. Furthermore, the changes in enthalpy and entropy for oxygen adsorption on liquid silicon were also estimated. [ABSTRACT FROM AUTHOR]

Abstract G-quadruplex (G4) is a higher-order nucleic acid structure that is formed by guanine-rich sequences. G4 stabilization by small-molecule compounds called G4 ligands often causes cytotoxicity, although the potential medicinal impact of this effect has not been fully established. Here we demonstrate that a synthetic G4 ligand, Y2H2-6M(4)-oxazole telomestatin derivative (6OTD), limits the growth of intractable glioblastoma (grade IV glioma) and glioma stem cells (GSCs). Experiments involving a human cancer cell line panel and mouse xenografts revealed that 6OTD exhibits antitumor activity against glioblastoma. 6OTD inhibited the growth of GSCs more potently than it did the growth of differentiated non-stem glioma cells (NSGCs). 6OTD caused DNA damage, G1 cell cycle arrest, and apoptosis in GSCs but not in NSGCs. These DNA damage foci tended to colocalize with telomeres, which contain repetitive G4-forming sequences. Compared with temozolomide, a clinical DNA-alkylating agent against glioma, 6OTD required lower concentrations to exert anti-cancer effects and preferentially affected GSCs and telomeres. 6OTD suppressed the intracranial growth of GSC-derived tumors in a mouse xenograft model. These observations indicate that 6OTD targets GSCs through G4 stabilization and promotion of DNA damage responses. Therefore, G4s are promising therapeutic targets for glioblastoma.