SUZ12 inhibition attenuates cell proliferation of glioblastoma via post-translational regulation of CDKN1B.

BACKGROUND: Human gliomas are aggressive brain tumors characterized by uncontrolled cell proliferation. Differential expression of Polycomb repressive complex 2 (PRC2) has been reported in various subtypes of glioma. However, the role of PRC2 in uncontrolled growth in glioma and its underlying molecular mechanisms remain to be elucidated. OBJECTIVE: We aimed to investigate the functional role of PRC2 in human glioblastoma cell growth by silencing SUZ12, the non-catalytic core component of PRC2. METHODS: Knockdown of SUZ12 was achieved by infecting T98G cells with lentivirus carrying sequences specifically targeting SUZ12 (shSUZ12). Gene expression was examined by quantitative PCR and western analysis. The impact of shSUZ12 on cell growth was assessed using a cell proliferation assay. Cell cycle distribution was analyzed by flow cytometry, and protein stability was evaluated in cycloheximide-treated cells. Subcellular localization was examined through immunofluorescence staining and biochemical cytoplasmic-nuclear fractionation. Gene expression analysis was also performed on human specimens from normal brain and glioblastoma patients. RESULTS: SUZ12 knockdown (SUZ12 KD) led to widespread decrease in the PRC2-specific histone mark, accompanied by a slowdown of cell proliferation through G1 arrest. In SUZ12 KD cells, the degradation of CDKN1B protein was reduced, resulting from alterations in the MYC-SKP2-CDKN1B axis. Furthermore, nuclear localization of CDKN1B was enhanced in SUZ12 KD cells. Analysis of human glioblastoma samples yielded increased expression of EZH2 and MYC along with reduced CDKN1B compared to normal human brain tissue. CONCLUSION: Our findings suggest a novel role for SUZ12 in cell proliferation through post-translational regulation of CDKN1B in glioblastoma.

Autistic-like social deficits in hippocampal MeCP2 knockdown rat models are rescued by ketamine.

Autism or autism spectrum disorder (ASD) is a behavioral syndrome characterized by persistent deficits in social interaction, and repetitive patterns of behavior, interests, or activities. The gene encoding Methyl-CpG binding protein 2 (MeCP2) is one of a few exceptional genes of established causal effect in ASD. Although genetically engineered mice studies may shed light on how MeCP2 loss affects synaptic activity patterns across the whole brain, such studies are not considered practical in ASD patients due to the overall level of impairment, and are technically challenging in mice. For the first time, we show that hippocampal MeCP2 knockdown produces behavioral abnormalities associated with autism-like traits in rats, providing a new strategy to investigate the efficacy of therapeutics in ASD. Ketamine, an N-Methyl-D-aspartate (NMDA) blocker, has been proposed as a possible treatment for autism. Using the MeCP2 knockdown rats in conjunction with a rat model of valproic acid (VPA)-induced ASD, we examined gene expression and ASD behaviors upon ketamine treatment. We report that the core symptoms of autism in MeCP2 knockdown rats with social impairment recovered dramatically following a single treatment with ketamine. [BMB Reports 2022; 55(5): 238-243].

A novel role for bone-derived cells in ankylosing spondylitis: Focus on IL-23.

The main aim of this study are to explore the role of bone-derived cells (BdCs) in ankylosing spondylitis (AS) and determine the underlying molecular mechanisms of IL-23 production. Primary BdCs were isolated from diced bone of facet joints obtained during surgery from seven AS patients and seven disease control (Ct) patients. Osteoblastic activity of BdCs was assessed by measuring their alkaline phosphatase activity and by alizarin red staining. Osteoblast and endoplasmic reticulum (ER) stress-related genes were assessed by quantitative PCR, immunoblotting, immunofluorescence, and immunohistochemistry. In addition, expression of IL-23 in response to BIX (selective BIP inducer X)-induced ER stress was evaluated by qPCR and ELISA. Protein interaction and binding to IL-23 promoter were confirmed by Immunoprecipitation and Chromatin immunoprecipitation, respectively. Transcript levels of genes involved in osteoblast function, as well as of the ER stress marker were higher in the AS group than the Ct group, and elevated RUNX2, BiP and IL-23 expression were observed in the BdCs, serum, and bone biopsies from the AS group. BIX-induced ER stress stimulated osteoblastic activity and IL-23 secretion by upregulating RUNX2 expression. Furthermore, in AS BdCs, RUNX2 interacted with C/EBPß to bind to IL-23 promoter and RUNX2 knockdown suppressed IL-23 secretion. These finding may provide a molecular mechanism involved in sustained ER stress in AS BdCs stimulates the activation of RUNX2 and C/EBPß genes, leading to IL-23 production.

PCGF2 negatively regulates arsenic trioxide-induced PML-RARA protein degradation via UBE2I inhibition in NB4 cells.

Arsenic trioxide (ATO) is a therapeutic agent for acute promyelocytic leukemia (APL) which induces PML-RARA protein degradation via enhanced UBE2I-mediated sumoylation. PCGF2, a Polycomb group protein, has been suggested as an anti-SUMO E3 protein by inhibiting the sumoylation of UBE2I substrates, HSF2 and RANGAP1, via direct interaction. Thus, we hypothesized that PCGF2 might play a role in ATO-induced PML-RARA degradation by interacting with UBE2I. PCGF2 protein was down-regulated upon ATO treatment in human APL cell line, NB4. Knockdown of PCGF2 in NB4 cells, in the absence of ATO treatment, was sufficient to induce sumoylation-, ubiquitylation- and PML nuclear body-mediated degradation of PML-RARA protein. Moreover, overexpression of PCGF2 protected ATO-mediated degradation of ectopic and endogenous PML-RARA in 293T and NB4 cells, respectively. In 293T cells, UBE2I-mediated PML-RARA degradation was reduced upon PCGF2 co-expression. In addition, UBE2I-mediated sumoylation of PML-RARA was reduced upon PCGF2 co-expression and PCGF2-UBE2I interaction was confirmed by co-immunoprecipitation. Likewise, endogenous PCGF2-UBE2I interaction was detected by co-immunoprecipitation and immunofluorescence assays in NB4 cells. Intriguingly, upon ATO-treatment, such interaction was disrupted and UBE2I was co-immunoprecipitated or co-localized with its SUMO substrate, PML-RARA. Taken together, our results suggested a novel role of PCGF2 in ATO-mediated degradation of PML-RARA that PCGF2 might act as a negative regulator of UBE2I via direct interaction.

Lobarstin enhances chemosensitivity in human glioblastoma T98G cells.

BACKGROUND/AIM: Lobarstin is a metabolite occurring from the Antarctic lichen Stereocaulon alpnum. Human glioblastoma is highly resistant to chemotherapy with temozolomide. Lobarstin was examined for its effect on glioblastoma. MATERIALS AND METHODS: Temozolomide-resistant T98G cells were subjected to toxicity test with temozolomide and/or lobarstin. DNA damage and recovery was assessed by the alkaline comet assay and expression of DNA repair genes was examined by RT-PCR and western blot analysis. RESULTS: Lobarstin alone at 40 µM was toxic against T98G, but had no effect in primary human fibroblasts. Co-treatment of lobarstin with temozolomide yielded enhanced toxicity. Temozolomide-alone or with lobarstin co-treatment gave similar extent of DNA damage. However, the recovery was reduced in co-treated cells. Expression of DNA repair genes, O(6)-methylguanine-DNA methyltransferase, poly(ADP-ribose) polymerase 1 and ligase 3 were reduced in lobarstin-treated cells. CONCLUSION: Enhanced sensitivity to temozolomide by lobarstin co-treatment may be attributed to reduced DNA repair.

Korean red ginseng extract induces proliferation to differentiation transition of human acute promyelocytic leukemia cells via MYC-SKP2-CDKN1B axis.

ETHNOPHARMACOLOGICAL RELEVANCE: Korean red ginseng has been used as traditional medicine in East Asia. Recent scientific research revealed multiple effects of Korean red ginseng, including anticancer activity. To evaluate the effect of Korean red ginseng extract (KRGE) in acute promyelocytic leukemia (APL) and elucidate its molecular mechanism. MATERIALS AND METHODS: NB4 cells were treated with 1mg/ml KRGE for 48 h and examined for cell proliferation and differentiation. Cell cycle distribution of KRGE-treated cells was analyzed and the expression level of G1 phase regulators was determined. MYC was overexpressed by retroviral transduction and its effect on SKP2 and CDKN1B gene expression, cell proliferation, cell cycle and differentiation was evaluated in KRGE-treated cells. RESULTS: KRGE alone was sufficient to induce granulocytic differentiation accompanied with growth inhibition. KRGE treatment resulted in cell cycle arrest at the G1 phase with augmented Cdkn1b proteins without changes in transcript levels. Cycloheximide treatment revealed reduced degradation of Cdkn1b protein by KRGE. In addition, KRGE treatment reduced expression of MYC and SKP2 genes, both at mRNA and protein levels. Upon ectopic expression of MYC, the effect of KRGE was reversed with lesser reduction and induction of SKP2 gene and Cdkn1b protein, respectively. Taken together, these results suggest a sequential molecular mechanism from MYC reduction, SKP2 reduction, Cdkn1b protein stabilization, G1 phase arrest to granulocytic differentiation by KRGE in human APL. CONCLUSIONS: KRGE induces leukemic proliferation to differentiation transition in APL through modulation of the MYC-SKP2-CDKN1B axis.

Inhibition of PCGF2 enhances granulocytic differentiation of acute promyelocytic leukemia cell line HL-60 via induction of HOXA7.

This study tested the hypothesis that Polycomb Repressive Complex 1 (PRC1) may play a negative role in the granulocytic differentiation of acute promyelocytic leukemia (APL) cells. We first examined the expression of PRC1 genes during all-trans retinoic acid (ATRA)-mediated differentiation of human HL-60 cells, and identified PCGF2 as a gene down-regulated by ATRA in a time-dependent manner. Upon gene silencing of PCGF2 with lentiviral short hairpin RNA, granulocytic differentiation was induced as assessed by differentiation marker gene expression, nitroblue tetrazolium staining, Wright-Giemsa staining, and cell cycle analysis. We next identified HOXA7 as a homeobox gene up-regulated by ATRA and successfully induced granulocytic differentiation by overexpression of HOXA7. We next tested the relationship between PCGF2 and HOXA7 by quantifying the changes in HOXA7 and PCGF2 expression upon PCGF2 gene silencing and HOXA7 overexpression, respectively. HOXA7 expression was up-regulated by PCGF2 gene silencing, while PCGF2 expression remained unchanged by ectopic HOXA7 expression, suggesting PCGF2 as acting upstream of HOXA7. Finally, chromatin immunoprecipitation assay was performed with HOXA7 chromatin. We observed gene-specific reduction in direct binding of Pcgf2 protein to HOXA7 chromatin upon PCGF2 gene silencing. Taken together, these results support the notion that down-regulation of PCGF2 is sufficient to induce granulocytic differentiation of HL-60 cells via de-repression of HOXA7 gene expression. In conclusion, we report that PCGF2, a PRC1 gene, played a negative role in the granulocytic differentiation of human APL cells.

A newly identified CG301269 improves lipid and glucose metabolism without body weight gain through activation of peroxisome proliferator-activated receptor alpha and gamma.

OBJECTIVE: Peroxisome proliferator-activated receptor (PPAR)-α/γ dual agonists have been developed to alleviate metabolic disorders. However, several PPARα/γ dual agonists are accompanied with unwanted side effects, including body weight gain, edema, and tissue failure. This study investigated the effects of a novel PPARα/γ dual agonist, CG301269, on metabolic disorders both in vitro and in vivo. RESEARCH DESIGN AND METHODS: Function of CG301269 as a PPARα/γ dual agonist was assessed in vitro by luciferase reporter assay, mammalian one-hybrid assay, and analyses of PPAR target genes. In vitro profiles on fatty acid oxidation and inflammatory responses were acquired by fatty acid oxidation assay and quantitative (q)RT-PCR of proinflammatory genes. In vivo effect of CG301269 was examined in db/db mice. Total body weight and various tissue weights were measured, and hepatic lipid profiles were analyzed. Systemic glucose and insulin tolerance were measured, and the in vivo effect of CG301269 on metabolic genes and proinflammatory genes was examined by qRT-PCR. RESULTS: CG301269 selectively stimulated the transcriptional activities of PPARα and PPARγ. CG301269 enhanced fatty acid oxidation in vitro and ameliorated insulin resistance and hyperlipidemia in vivo. In db/db mice, CG301269 reduced inflammatory responses and fatty liver, without body weight gain. CONCLUSIONS: We demonstrate that CG301269 exhibits beneficial effects on glucose and lipid metabolism by simultaneous activation of both PPARα and PPARγ. Our data suggest that CG301269 would be a potential lead compound against obesity and related metabolic disorders.

A nonthiazolidinedione peroxisome proliferator-activated receptor α/γ dual agonist CG301360 alleviates insulin resistance and lipid dysregulation in db/db mice.

Activation of peroxisome proliferator-activated receptors (PPARs) have been implicated in the treatment of metabolic disorders with different mechanisms; PPARα agonists promote fatty acid oxidation and reduce hyperlipidemia, whereas PPARγ agonists regulate lipid redistribution from visceral fat to subcutaneous fat and enhance insulin sensitivity. To achieve combined benefits from activated PPARs on lipid metabolism and insulin sensitivity, a number of PPARα/γ dual agonists have been developed. However, several adverse effects such as weight gain and organ failure of PPARα/γ dual agonists have been reported. By use of virtual ligand screening, we identified and characterized a novel PPARα/γ dual agonist, (R)-1-(4-(2-(5-methyl-2-p-tolyloxazol-4-yl)ethoxy)benzyl)piperidine-2-carboxylic acid (CG301360), exhibiting the improvement in insulin sensitivity and lipid metabolism. CG301360 selectively stimulated transcriptional activities of PPARα and PPARγ and induced expression of their target genes in a PPARα- and PPARγ-dependent manner. In cultured cells, CG301360 enhanced fatty acid oxidation and glucose uptake and it reduced pro-inflammatory gene expression. In db/db mice, CG301360 also restored insulin sensitivity and lipid homeostasis. Collectively, these data suggest that CG301360 would be a novel PPARα/γ agonist, which might be a potential lead compound to develop against insulin resistance and hyperlipidemia.

Normal Adult Hippocampal Neurogenesis in SRG3-overexpressing Transgenic Mice.

SRG3 (SWI3-related gene) is a core subunit of mouse SWI/SNF complex and is known to play a critical role in stabilizing the SWI/SNF complex by attenuating its proteasomal degradation. SWI/SNF chromatin remodeling complex is reported to act as an important endogenous regulator in the proliferation and differentiation of mammalian neural stem cells. Because limited expression of SRG3 occurs in the brain and thymus during mouse embryogenesis, it was hypothesized that the altered SRG3 expression level might affect the process of adult hippocampal neurogenesis. Due to the embryonic lethality of homozygous knockout mice, this study focuses on dissecting the effect of overexpressed SRG3 on adult hippocampal neurogenesis. The BrdU incorporation assay, immunostaing with neuronal markers for each differentiation stage, and imunoblotting analysis with intracellular molecules involved in survival in adult hippocampal neurogenesis found no alteration, suggesting that the overexpression of SRG3 protein in mature neurons had no effect on the entire process of adult hippocampal neurogenesis including proliferation, differentiation, and survival.

Induction of neuronal vascular endothelial growth factor expression by cAMP in the dentate gyrus of the hippocampus is required for antidepressant-like behaviors.

The cAMP cascade and vascular endothelial growth factor (VEGF) are critical modulators of depression. Here we have tested whether the antidepressive effect of the cAMP cascade is mediated by VEGF in the adult hippocampus. We used a conditional genetic system in which the Aplysia octopamine receptor (Ap oa(1)), a G(s)-coupled receptor, is transgenically expressed in the forebrain neurons of mice. Chronic activation of the heterologous Ap oa(1) by its natural ligand evoked antidepressant-like behaviors, accompanied by enhanced phosphorylation of cAMP response element-binding protein and transcription of VEGF in hippocampal dentate gyrus (DG) neurons. Selective knockdown of VEGF in these cells during the period of cAMP elevation inhibited the antidepressant-like behaviors. These findings reveal a molecular interaction between the cAMP cascade and VEGF expression, and the pronounced behavioral consequences of this interaction shed light on the mechanism underlying neuronal VEGF functions in antidepression.

Chromatin remodeling, development and disease.

Development is a stepwise process in which multi-potent progenitor cells undergo lineage commitment, differentiation, proliferation and maturation to produce mature cells with restricted developmental potentials. This process is directed by spatiotemporally distinct gene expression programs that allow cells to stringently orchestrate intricate transcriptional activation or silencing events. In eukaryotes, chromatin structure contributes to developmental progression as a blueprint for coordinated gene expression by actively participating in the regulation of gene expression. Changes in higher order chromatin structure or covalent modification of its components are considered to be critical events in dictating lineage-specific gene expression during development. Mammalian cells utilize multi-subunit nuclear complexes to alter chromatin structure. Histone-modifying complex catalyzes covalent modifications of histone tails including acetylation, methylation, phosphorylation and ubiquitination. ATP-dependent chromatin remodeling complex, which disrupts histone-DNA contacts and induces nucleosome mobilization, requires energy from ATP hydrolysis for its catalytic activity. Here, we discuss the diverse functions of ATP-dependent chromatin remodeling complexes during mammalian development. In particular, the roles of these complexes during embryonic and hematopoietic development are reviewed in depth. In addition, pathological conditions such as tumor development that are induced by mutation of several key subunits of the chromatin remodeling complex are discussed, together with possible mechanisms that underlie tumor suppression by the complex.

Time- and dose-based gene expression profiles produced by a bile-duct-damaging chemical, 4,4'-methylene dianiline, in mouse liver in an acute phase.

A toxicogenomics study was performed in the mouse liver after treatment of a bile-duct-damaging chemical, 4,4'-methylene dianiline (MDA), across multiple doses and sampling times in an acute phase using the AB Expression Array System. Imprinting control region (ICR) mice were given a single oral administration of a low (10 mg/kg b.w.) or high (100 mg/kg b.w.) dose of MDA. Mice were sacrificed six, twenty-four, and seventy-two hours after treatment for serum chemistry, histopathology, and mRNA preparation from liver samples. Treatment with MDA increased liver-toxicity-related enzymes in blood and induced bile-duct cell injury, followed by regeneration. To explore potential biomarker gene profiles, the altered genes were categorized into four expression patterns depending on dose and time. Numerous functionally defined and unclassified genes in each category were up- or down-regulated throughout the period from cellular injury to the recovery phase, verified by RT-PCR. Many genes associated with liver toxicity and diseases belonged to one of these categories. The chemokine-mediated Th1 pathway was implicated in the inflammatory process. The genes associated with oxidative stress, apoptosis, and cell-cycle regulation were also dynamically responsive to MDA treatment. The Wnt/beta-catenin signaling pathway was likely responsible for the reconstitution process of the MDA-injured liver.

Gene expression profiles of murine fatty liver induced by the administration of methotrexate.

Methotrexate (MTX) is used to treat a variety of chronic inflammatory and neoplastic diseases. However, it can induce hepatotoxicity such as microvesicular steatosis and necrosis. To explore the mechanisms of MTX-induced hepatic steatosis, we used microarray analysis to profile the gene expression patterns of mouse liver after MTX treatment. MTX was administered orally as a single dose of 10mg/kg (low dose) or 100 mg/kg (high dose) to ICR mice, and the livers were obtained 6 h, 24 h, and 72 h after treatment. Serum alanine aminotransferase, aspartate aminotransferase and triacylglycerol levels were not significantly altered in the experimental animals. Signs of steatosis were observed at 24 h after administration of high dose of MTX. From microarray data analysis, 908 genes were selected as MTX-responsive genes (P<0.05, two-way ANOVA; cutoff > or =1.5-fold). Database for Annotation, Visualization and Integrated Discovery (DAVID) analysis revealed that the predominant biological processes associated with these genes are response to unfolded proteins, phosphate metabolism, and cellular lipid metabolism. Functional categorization of these genes identified 28 genes involved in lipid metabolism that was interconnected with the biological pathways of biosynthesis, catabolism, and transport of lipids and fatty acids. Taken together, these data provide a better understanding of the molecular mechanisms of MTX-induced steatogenic hepatotoxicity, and useful information for predicting hepatotoxicity through pattern recognition.

BAF60a interacts with p53 to recruit the SWI/SNF complex.

To understand the tumor-suppressing mechanism of the SWI/SNF chromatin remodeling complex, we investigated its molecular relationship with p53. Using the pREP4-luc episomal reporter, we first demonstrated that p53 utilizes the chromatin remodeling activity of the SWI/SNF complex to initiate transcription from the chromatin-structured promoter. Among the components of the SWI/SNF complex, we identified BAF60a as a mediator of the interaction with p53 by the yeast two-hybrid assay. p53 directly interacted only with BAF60a, but not with other components of the SWI/SNF complex, such as BRG1, SRG3, SNF5, or BAF57. We found out that multiple residues at the amino acid 108-150 region of BAF60a were involved in the interaction with the tetramerization domain of p53. The N-terminal fragment of BAF60a containing the p53-interacting region as well as small interfering RNA for baf60a inhibited the SWI/SNF complex-mediated transcriptional activity of p53. The uncoupling of p53 with the SWI/SNF complex resulted in the repression of both p53-dependent apoptosis and cell cycle arrest by the regulation of target genes. These results suggest that the SWI/SNF chromatin remodeling complex is involved in the suppression of tumors by the interaction with p53.

SRG3, a core component of mouse SWI/SNF complex, is essential for extra-embryonic vascular development.

The SWI/SNF chromatin-remodeling complex functions as a transcriptional regulator and plays a significant role in cell proliferation, differentiation and embryonic development. SRG3, a homologue of human BAF155, is a core component of the mouse SWI/SNF chromatin remodeling complex. Mutant mice deficient in Srg3 expression are peri-implantation lethal. To investigate the role of SRG3 in the post-implantation stage, we generated SRG3 transgene-rescued (Srg3-/-Tg+) embryos by inducing exogenous gene expression. These Srg3-/-Tg+ embryos overcame early embryonic lethality and extended the life span until mid-gestation. However, the embryos displayed significant defects in blood vessel formation and fetal circulation within the yolk sac around embryonic day 10.5, which led to developmental retardation and death. We found that SRG3 expression was absent in the visceral endoderm of Srg3-/-Tg+ yolk sacs, while SRG3 was normally expressed in wild-type embryos. In addition, expression of angiogenesis-related genes, including Angiopoietin1, Tie2, EphrinB2, Ihh and Notch1, was markedly reduced in Srg3-/-Tg+ yolk sacs. During normal angiogenesis, maturation of the visceral endoderm development is observed in the yolk sac. However, in Srg3-/-Tg+ yolk sacs, the visceral endoderm did not develop normally. Our results indicate that SRG3 is required for angiogenesis and visceral endoderm development in the yolk sac.

Id-1 regulates Bcl-2 and Bax expression through p53 and NF-kappaB in MCF-7 breast cancer cells.

Although increasing evidence supports the protective role of inhibitor of differentiation and DNA binding-1 (Id-1) against anticancer drug-induced apoptosis, the underlying molecular mechanisms seem to vary depending on the tumor system. Here, we examined the direct role of Id-1 in MCF-7 breast cancer cells by ectopically overexpressing Id-1 under serum-free condition, where the endogenous Id-1 expression was suppressed. Id-1 expression resulted in increased number of viable cells, reduced Bax expression, enhanced Bcl-2 expression, but no change in Bcl-xL expression. The expression of nuclear factor-kappaB (NF-kappaB) was augmented, while those of p53 and IkappaB were reduced. Such changes in p53 and NF-kappaB pathways were also functional, as assessed by real-time polymerase chain reactions and reporter assays of their known downstream targets, p21 and Il-6, as well as Bax and Bcl-2 genes. Finally, Id-1 played a protective role against taxol-induced apoptosis in breast cancer cells as assessed by MTT assay and apoptotic cell count upon taxol treatment (0-200 nM). Reduced Bax expression and enhanced Bcl-2 expression by Id-1 were also noted in the presence of taxol. Taken together, we present a molecular mechanism where Id-1 regulates p53 and NF-kappaB pathways, which in turn regulates Bax and Bcl-2 genes, thus providing a survival advantage under exogenous stress such as serum-free or taxol treatment in MCF-7 breast cancer cells. In this regard, inactivation of Id-1 may provide a potential therapeutic strategy leading to inhibition of breast cancer progression and anti-cancer drug resistance.

Subchronic effects of valproic acid on gene expression profiles for lipid metabolism in mouse liver.

Valproic acid (VPA) is used clinically to treat epilepsy, however it induces hepatotoxicity such as microvesicular steatosis. Acute hepatotoxicity of VPA has been well documented by biochemical studies and microarray analysis, but little is known about the chronic effects of VPA in the liver. In the present investigation, we profiled gene expression patterns in the mouse liver after subchronic treatment with VPA. VPA was administered orally at a dose of 100 mg/kg/day or 500 mg/kg/day to ICR mice, and the livers were obtained after 1, 2, or 4 weeks. The activities of serum liver enzymes did not change, whereas triglyceride concentration increased significantly. Microarray analysis revealed that 1325 genes of a set of 32,996 individual genes were VPA responsive when examined by two-way ANOVA (P<0.05) and fold change (>1.5). Consistent with our previous results obtained using an acute VPA exposure model (Lee et al., Toxicol Appl Pharmacol. 220:45-59, 2007), the most significantly over-represented biological terms for these genes included lipid, fatty acid, and steroid metabolism. Biological pathway analysis suggests that the genes responsible for increased biosynthesis of cholesterol and triglyceride, and for decreased fatty acid beta-oxidation contribute to the abnormalities in lipid metabolism induced by subchronic VPA treatment. A comparison of the VPA-responsive genes in the acute and subchronic models extracted 15 commonly altered genes, such as Cyp4a14 and Adpn, which may have predictive power to distinguish the mode of action of hepatotoxicants. Our data provide a better understanding of the molecular mechanisms of VPA-induced hepatotoxicity and useful information to predict steatogenic hepatotoxicity.

Anticancer effects of wogonin in both estrogen receptor-positive and -negative human breast cancer cell lines in vitro and in nude mice xenografts.

Wogonin is a plant monoflavonoid which has been reported to inhibit cell growth and/or induce apoptosis in various tumors. Herein, we investigated the in vitro and in vivo anticancer effects and associated mechanisms of wogonin in human breast cancer. Effects of wogonin were examined in estrogen receptor (ER)-positive and -negative human breast cancer cells in culture for proliferation, cell cycle progression, and apoptosis. The in vivo effect of oral wogonin was examined on tumor xenograft growth in athymic nude mice. The molecular changes associated with the biological effects of wogonin were analyzed by immunoblotting. Cell growth was attenuated by wogonin (50-200 microM), independently of its ER status, in a time- and concentration-dependent manner. Apoptosis was enhanced and accompanied by upregulation of PARP and Caspase 3 cleavages as well as proapoptotic Bax protein. Akt activity was suppressed and reduced phosphorylation of its substrates, GSK-3beta and p27, was observed. Suppression of Cyclin D1 expression suggested the downregulation of the Akt-mediated canonical Wnt signaling pathway. ER expression was downregulated in ER-positive cells, while c-ErbB2 expression and its activity were suppressed in ER-negative SK-BR-3 cells. Wogonin feeding to mice showed inhibition of tumor growth of T47D and MDA-MB-231 xenografts by up to 88% without any toxicity after 4 weeks of treatment. As wogonin was effective both in vitro and in vivo, our novel findings open the possibility of wogonin as an effective therapeutic and/or chemopreventive agent against both ER-positive and -negative breast cancers, particularly against the more aggressive and hormonal therapy-resistant ER-negative types.

Inhibitor of DNA binding 1 activates vascular endothelial growth factor through enhancing the stability and activity of hypoxia-inducible factor-1alpha.

Inhibitor of DNA binding 1 (Id-1) has been implicated in tumor angiogenesis by regulating the expression of vascular endothelial growth factor (VEGF), but its molecular mechanism has not been fully understood. Here, we show the cross talk between Id-1 and hypoxia-inducible factor-1alpha (HIF-1alpha), that Id-1 induces VEGF by enhancing the stability and activity of HIF-1alpha in human endothelial and breast cancer cells. Although both the transcript and proteins levels of VEGF were induced by Id-1, only the protein expression of HIF-1alpha was induced without transcriptional changes in both human umbilical endothelial cells and MCF7 breast cancer cells. Such induction of the HIF-1alpha protein did not require de novo protein synthesis but was dependent on the active extracellular response kinase (ERK) pathway. In addition, stability of the HIF-1alpha protein was enhanced in part by the reduced association of the HIF-1alpha protein with von Hippel-Lindau protein in the presence of Id-1. Furthermore, Id-1 enhanced nuclear translocation and the transcriptional activity of HIF-1alpha. Transcriptional activation of HIF-1-dependent promoters was dependent on the active ERK pathway, and the association of HIF-1alpha protein with cyclic AMP-responsive element binding protein was enhanced by Id-1. Finally, Id-1 induced tube formation in human umbilical endothelial cells, which also required active ERK signaling. In conclusion, we provide the molecular mechanism of the cross talk between HIF-1alpha and Id-1, which may play a critical role in tumor angiogenesis.