Direct Targeting of β-Catenin by a Small Molecule Stimulates Proteasomal Degradation and Suppresses Oncogenic Wnt/β-Catenin Signaling.

The Wnt/β-catenin signaling pathway plays a major role in tissue homeostasis, and its dysregulation can lead to various human diseases. Aberrant activation of β-catenin is oncogenic and is a critical driver in the development and progression of human cancers. Despite the significant potential of targeting the oncogenic β-catenin pathway for cancer therapy, the development of specific inhibitors remains insufficient.

Small-Molecule Reactivation of Mutant p53 to Wild-Type-like p53 through the p53-Hsp40 Regulatory Axis.

TP53 is the most frequently mutated gene in human cancer, and small-molecule reactivation of mutant p53 function represents an important anticancer strategy. A cell-based, high-throughput small-molecule screen identified chetomin (CTM) as a mutant p53 R175H reactivator. CTM enabled p53 to transactivate target genes, restored MDM2 negative regulation, and selectively inhibited the growth of cancer cells harboring mutant p53 R175H in vitro and in vivo.

Control of signaling-mediated clearance of apoptotic cells by the tumor suppressor p53.

The inefficient clearance of dying cells can lead to abnormal immune responses, such as unresolved inflammation and autoimmune conditions. We show that tumor suppressor p53 controls signaling-mediated phagocytosis of apoptotic cells through its target, Death Domain1α (DD1α), which suggests that p53 promotes both the proapoptotic pathway and postapoptotic events. DD1α appears to function as an engulfment ligand or receptor that engages in homophilic intermolecular interaction at intercellular junctions of apoptotic cells and macrophages, unlike other typical scavenger receptors that recognize phosphatidylserine on the surface of dead cells.

Basal transcription is regulated by lipopolysaccharide and glucosamine via the regulation of DNA binding of RNA polymerase II in RAW264.7 cells.

Aims: The objective of this study is to investigate glucosamine (GlcN) as a transcriptional regulator of iNOS and other genes in association with the dynamic O-GlcNAcylation of RNA polymerase II (RNAPII).

Main Methods: The LPS- and/or GlcN-stimulated transcriptional activities of various Gal4-binding site/TATA-box-containing reporter constructs were measured.

Key Findings: Basal transcriptional activities of nuclear factor-κB (NF-κB) and nitric oxide synthase (iNOS) reporter plasmids are inhibited by GlcN in RAW264.

CDIP1-BAP31 complex transduces apoptotic signals from endoplasmic reticulum to mitochondria under endoplasmic reticulum stress.

Resolved endoplasmic reticulum (ER) stress response is essential for intracellular homeostatic balance, but unsettled ER stress can lead to apoptosis. Here, we show that a proapoptotic p53 target, CDIP1, acts as a key signal transducer of ER-stress-mediated apoptosis. We identify B-cell-receptor-associated protein 31 (BAP31) as an interacting partner of CDIP1.

O-GlcNAc transferase inhibits LPS-mediated expression of inducible nitric oxide synthase through an increased interaction with mSin3A in RAW264.7 cells.

O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT), which catalyzes the addition of a single β-N-GlcNAc unit to target proteins, has been shown to act as a transcriptional regulator. In the current study, we discovered that OGT exerted inhibitory effects on the LPS-driven activation of NF-κB and inducible nitric oxide synthase (iNOS). In response to LPS, OGT exhibited an increased interaction with the transcriptional corepressor mammalian Sin3A (mSin3A).

O-GlcNAcylation and p50/p105 binding of c-Rel are dynamically regulated by LPS and glucosamine in BV2 microglia cells.

Background And Purpose: Previously, we demonstrated that glucosamine (GlcN) exerts a suppressive effect on LPS-induced inducible NOS (iNOS) through the inhibition of NF-κB activation in BV2 mouse microglial cells. The purpose of the present study was to examine the mechanisms by which GlcN inhibits NF-κB activation.

Experimental Approach: BV2 cells were stimulated with LPS with or without GlcN.

Glucosamine inhibits lipopolysaccharide-stimulated inducible nitric oxide synthase induction by inhibiting expression of NF-kappaB/Rel proteins at the mRNA and protein levels.

Expression of inducible nitric oxide synthase (iNOS) protein by lipopolysaccharide (LPS) in BV2 microglia cells increased in a biphasic manner. Glucosamine (GlcN) selectively suppressed the late- but not early-stage iNOS response to LPS. Prolonged induction of iNOS expression by LPS was inhibited by cycloheximide, suggesting that de novo protein synthesis was required.

DDR1 receptor tyrosine kinase promotes prosurvival pathway through Notch1 activation.

DDR1 (discoidin domain receptor tyrosine kinase 1) kinase s highly expressed in a variety of human cancers and occasionally mutated in lung cancer and leukemia. It is now clear that aberrant signaling through the DDR1 receptor is closely associated with various steps of tumorigenesis, although little is known about the molecular mechanism(s) underlying the role of DDR1 in cancer. Besides the role of DDR1 in tumorigenesis, we previously identified DDR1 kinase as a transcriptional target of tumor suppressor p53.

Glucosamine exerts a neuroprotective effect via suppression of inflammation in rat brain ischemia/reperfusion injury.

We investigated the neuroprotective effect of glucosamine (GlcN) in a rat middle cerebral artery occlusion model. At the highest dose used, intraperitoneal GlcN reduced infarct volume to 14.3% ± 7.

Induction of glioma apoptosis by microglia-secreted molecules: The role of nitric oxide and cathepsin B.

Microglia contributes significantly to brain tumor mass, particularly in astrocytic gliomas. Here, we examine the cytotoxic effects of soluble components secreted from microglia culture on glioma cells. Microglia conditioned culture medium (MCM) actively stimulated apoptotic death of glioma cells, and the effects of MCM prepared from LPS- or IFN-gamma-activated microglia were more pronounced.

C6 glioma cell insoluble matrix components enhance interferon-gamma-stimulated inducible nitric-oxide synthase/nitric oxide production in BV2 microglial cells.

Microglia are the primary central nervous system immune effector cells. Microglial activation is linked to interactions with extracellular cytokines and the extracellular matrix (ECM). Astrocytomas are characterized by their diffuse nature, which is regulated by insoluble ECM components produced by the tumor cells that are largely absent from normal central nervous system tissue.

Ionising radiation induces changes associated with epithelial-mesenchymal transdifferentiation and increased cell motility of A549 lung epithelial cells.

Radiotherapy remains a major therapeutic option for patients with advanced lung cancer. Nevertheless, the effects of irradiation on malignant biological behaviours (e.g.

IL-1beta, an immediate early protein secreted by activated microglia, induces iNOS/NO in C6 astrocytoma cells through p38 MAPK and NF-kappaB pathways.

In the present study we sought to examine cell-cell interactions by investigating the effects of factors released by stimulated microglia on inducible nitric oxide (NO) synthase (iNOS) induction in astrocytoma cells. After examining the temporal profiles of proinflammatory molecules induced by lipopolysaccharide (LPS) stimulation in BV2 microglial cells, iNOS and IL-1beta were observed to be the first immediate-response molecules. Removal of LPS after 3 hr stimulation abrogated NO release, whereas a full induction of IL-1beta was retained in BV2 cells.

Insoluble matrix components of glioma cells suppress LPS-mediated iNOS/NO induction in microglia.

This study examines the influence of insoluble matrix components of glioma (astrocytoma) cells on LPS-mediated inducible nitric oxide (NO)/NO synthase (iNOS) induction in microglia cells. Insoluble matrix components prepared from C6 rat glioma cells strongly suppressed iNOS induction and subsequent NO release induced by LPS. Matrices prepared from several glioma cell lines displayed similar inhibitory effects on LPS-induced NO/iNOS induction, whereas matrices from primary cultured rat astrocytes had a minimal influence.

Dominant-negative Rac increases both inherent and ionizing radiation-induced cell migration in C6 rat glioma cells.

Rho-like GTPases, including Cdc42, Rac1 and RhoA, regulate distinct actin cytoskeleton changes required for cell adhesion, migration and invasion. In the present study, we examined the role of Rac signaling in inherent migration, as well as radiation-induced migration, of rat glioma cells. Stable overexpression of dominant-negative Rac1N17 in a C6 rat glioma cell line (C6-RacN17) promoted cell migration, and ionizing radiation further increased this migration.

Ionizing radiation induces astrocyte gliosis through microglia activation.

The aim of this study was to investigate the role of microglia in radiation-induced astrocyte gliosis. We found that a single dose of 15 Gy radiation to a whole rat brain increased immunostaining of glial fibrillary acidic protein in astrocytes 6 h later, and even more so 24 h later, indicating the initiation of gliosis. While irradiation of cultured rat astrocytes had little effect, irradiation of microglia-astrocyte mixed-cultures displayed altered astrocyte phenotype into more processed, which is another characteristic of gliosis.

TGF-beta1 represses activation and resultant death of microglia via inhibition of phosphatidylinositol 3-kinase activity.

Overactivation of microglial cells may cause severe brain tissue damage in various neurodegenerative diseases. Therefore, the overactivation of microglia should be repressed by any means. The present study investigated the potential mechanism and signaling pathway for the repressive effect of TGF-beta1, a major anti-inflammatory cytokine, on overactivation and resultant death of microglial cells.

LY294002 inhibits interferon-gamma-stimulated inducible nitric oxide synthase expression in BV2 microglial cells.

The current study examined the potential involvement of phosphatidylinositol 3 phosphate kinase (PI3K) in interferon-gamma (IFN-gamma)-stimulated nitric oxide (NO) generation in BV2 murine microglial cells. We found that LY294002, a PI3K inhibitor, markedly reduced IFN-gamma-induced morphological changes, NO production, and cell death. The inhibitory effect of LY294002 on NO generation may be mediated through specific inhibition of signal transducer and activator-1 (STAT1) and NF-kappaB, which are activated by IFN-gamma.