Hyojeung Kang

Expression of hMLH1 is inactivated in the gastric adenomas with enhanced microsatellite instability

Microsatellite instability (MSI) and frameshift mutations in the genes containing coding nucleotide repeats have been reported in a subset of gastric adenomas, however the inactivation profiles of DNA mismatch repair genes in MSI-positive gastric adenomas have not been characterized. To address the origin of MSI in gastric adenomas, expressions of hMLH1 and hMSH2 were explored in 86 gastric adenomas. Gastric carcinomas, of which 16 were MSI-positive and 22 MSI-negative, were used as controls. MSI was found in 15 (17%) of gastric adenomas. Absent or decreased hMLH1 expression by immunohistochemistry was noted in most of the MSI-positive adenomas (13/15, 87%) and carcinomas (14/16, 88%), and all of these tumours showed methylation of the hMLH1 gene promoter. In contrast, rare inactivation of hMLH1 expression was found in MSI-negative adenomas (3/71, 4%) and carcinomas (2/22, 9%). Intense expression of hMSH2 gene product was observed in most of the gastric adenomas and carcinomas regardless of MSI status. These findings indicate that the inactivation of hMLH1 gene expression by promoter methylation is an early event and might be the origin of MSI-positive gastric adenomas.

Prognostic value of Tumor-infiltrating lymphocytes in Epstein-Barr virus-associated gastric cancer

BACKGROUND This study explored the prognostic impact of tumor-infiltrating lymphocytes (TILs) and investigated whether three histologic subtypes (lymphoepithelioma-like carcinoma, carcinoma with Crohns disease-like lymphoid reaction, and conventional-type adenocarcinoma) could stratify a prognostic subset for patients with Epstein-Barr virus (EBV)-associated gastric cancer (EBVaGC). MATERIALS AND METHODS After reviewing 1318 consecutive cases of surgically resected or endoscopic submucosal dissected gastric cancers, 120 patients were identified as EBV-positive using EBV-encoded RNA in situ hybridization. The evaluation of the percentage of intratumoral (iTu-) and stromal (str-) TILs was carried out, and the cases were also subclassified into three histologic subtypes as noted above. RESULTS Among the 120 patients, 73 patients (60.8%) and 60 patients (50.0%) were determined as str-TIL-positive and iTu-TIL-positive, respectively. In a univariate analysis, str-TIL-positivity was significantly associated with longer recurrence-free survival (RFS; P = 0.002) and disease-free survival (DFS; P = 0.008), yet not overall survival (OS; P = 0.145). While iTu-TIL-positivity has a tendency of favorable outcome indicator for DFS and OS, but statistically significant differences were not shown, respectively (RFS, P = 0.058; DFS, P = 0.151; OS, P = 0.191). In a multivariate analysis using a Cox proportional hazard model adjusted for age, pTNM stage, lymphatic invasion, perineural invasion, and venous invasion; histologic subtype, WHO classification, and str-TIL-positivity were independently or tentatively associated with favorable RFS (hazard ratio [HR] = 12.193, 95% confidence interval [95% CI] 1.039-143.055, P = 0.047) or DFS (HR = 4.836, 95% CI 0.917-25.525, P = 0.063). CONCLUSION The histologic subclassification and TILs can be used to predict RFS and DFS for patients with EBVaGC.

CTCF Regulates Kaposi's Sarcoma-Associated Herpesvirus Latency Transcription by Nucleosome Displacement and RNA Polymerase Programming

ABSTRACT CCCTC-binding factor (CTCF) has been implicated in various aspects of viral and host chromatin organization and transcriptional control. We showed previously that CTCF binds to a cluster of three sites in the first intron of the Kaposis sarcoma-associated herpesvirus (KSHV) multicistronic latency-associated transcript that encodes latency-associated nuclear antigen (LANA), viral cyclin (vCyclin), vFLIP, viral microRNAs, and kaposin. We show here that these CTCF binding sites regulate mRNA production, RNA polymerase II (RNAPII) programming, and nucleosome organization of the KSHV latency transcript control region. We also show that KSHV bacmids lacking these CTCF binding sites have elevated and altered ratios of spliced latency transcripts. CTCF binding site mutations altered RNAPII and RNAPII-accessory factor interactions with the latency control region. CTCF binding sites were required for the in vitro recruitment of RNAPII to the latency control region, suggesting that direct interactions between CTCF and RNAPII contribute to transcription regulation. Histone modifications in the latency control region were also altered by mutations in the CTCF binding sites. Finally, we show that CTCF binding alters the regular phasing of nucleosomes in the latency gene transcript and intron, suggesting that nucleosome positioning can be an underlying biochemical mechanism of CTCF function. We propose that RNAPII interactions and nucleosome displacement serve as a biochemical basis for programming RNAPII in the KSHV transcriptional control region.

JAK2-targeted anti-inflammatory effect of a resveratrol derivative 2,4-dihydroxy-N-(4-hydroxyphenyl)benzamide

Chemical derivatization of resveratrol has been widely conducted in an effort to overcome its chemical instability and therapeutic potential. In the present study, we examined the anti-inflammatory effects of resveratrol derivatives containing an amide functionality using in vitro macrophage models that were stimulated by Toll-like receptor (TLR) ligands, and using several animal inflammatory disease models. Of the resveratrol derivatives tested, compound 8 (2,4-dihydroxy-N-(4-hydroxyphenyl)benzamide) most strongly inhibited the production of nitric oxide (NO), tumor necrosis factor (TNF)-α, and prostaglandin E2 (PGE2), as well as the mRNA expression of inducible NO synthase (iNOS), TNF-α, and cyclooxygenase (COX)-2 in lipopolysaccharide (LPS)-activated RAW264.7 cells, differentiated U937 cells, and peritoneal macrophages. The inhibitory activity of compound 8 was apparently mediated by suppressing the phosphorylation of signal transducer and activator of transcription (STAT)-1, STAT-3, STAT-5, and interferon regulatory factor (IRF)-3. The direct target of compound 8 was revealed to be Janus kinase 2 (JAK2) but not TANK-binding kinase (TBK) 1 using the direct kinase assay and analyses of complex formation with these molecules. Additionally, upstream kinase of TBK1 seems to be also inhibited by compound 8. This compound also strongly ameliorated mouse inflammatory symptoms seen in arachidonic acid-induced ear edema, dextran sodium sulfate (DSS)-treated colitis, EtOH/HCl-induced gastritis, collagen type II-triggered arthritis, and acetic acid-induced writhing. Therefore, of the resveratrol derivatives that we tested, compound 8 was determined to have the strongest anti-inflammatory activities in vitro and in vivo and may potentially be developed for use as a novel anti-inflammatory drug.

Genipin as a novel chemical activator of EBV lytic cycle

Epstein-Barr virus (EBV) is a ubiquitous gammaherpesvirus that causes acute infection and establishes life-long latency. EBV causes several human cancers, including Burkitt’s lymphoma, nasopharyngeal and gastric carcinoma. Antiviral agents can be categorized as virucides, antiviral chemotherapeutic agents, and immunomodulators. Most antiviral agents affect actively replicating viruses, but not their latent forms. Novel antiviral agents must be active on both the replicating and the latent forms of the virus. Gardenia jasminoides is an evergreen flowering plant belonging to the Rubiaceae family and is most commonly found growing wild in Vietnam, Southern China, Taiwan, Japan, Myanmar, and India. Genipin is an aglycone derived from an iridoid glycoside called geniposide, which is present in large quantities in the fruit of G. jasminoides. In this study, genipin was evaluated for its role as an antitumor and antiviral agent that produces inhibitory effects against EBV and EBV associated gastric carcinoma (EBVaGC). In SNU719 cells, one of EBVaGCs, genipin caused significant cytotoxicity (70 μM), induced methylation on EBV C promoter and tumor suppressor gene BCL7A, arrested cell-cycle progress (S phases), upregulated EBV latent/lytic genes in a dose-dependent manner, stimulated EBV progeny production, activated EBV F promoter for EBV lytic activation, and suppressed EBV infection. These results indicated that genipin could be a promising candidate for antiviral and antitumor agents against EBV and EBVaGC.

Development of double-sided silicon strip position sensor

Since double-sided silicon strip sensor provides two-dimensional position information with high resolution, it has been developed in various areas for medical imaging sensor, radiation detector, sensing detector in space science and silicon vertexing/tracking detector in experimental particle physics. We designed and fabricated the double-sided silicon position sensor in 5-inch fabrication line. We present measurement results of electrical characteristics of the sensor such as leakage currents and capacitances as function of bias voltages. We also performed beta source test with 90Sr radioactive source and tested the radiation damage of fabricated sensors with 35 MeV proton beam. The charge collection efficiencies for different sensor designs were measured with laser scanning method

Bioactive activities of natural products against herpesvirus infection

More than 90% of adults have been infected with at least one human herpesvirus, which establish long-term latent infection for the life of the host. While anti-viral drugs exist that limit herpesvirus replication, many of these are ineffective against latent infection. Moreover, drug-resistant strains of herpesvirus emerge following chemotherapeutic treatment. For example, resistance to acyclovir and related nucleoside analogues can occur when mutations arise in either HSV thymidine kinase or DNA polymerases. Thus, there exists an unmet medical need to develop new anti-herpesvirus agents with different mechanisms of action. In this Review, we discuss the promise of anti-herpetic substances derived from natural products including extracts and pure compounds from potential herbal medicines. One example is Glycyrrhizic acid isolated from licorice that shows promising antiviral activity towards human gammaherpesviruses. Secondly, we discuss anti-herpetic mechanisms utilized by several natural products in molecular level. While nucleoside analogues inhibit replicating herpesviruses in lytic replication, some natural products can disrupt the herpesvirus latent infection in the host cell. In addition, natural products can stimulate immune responses against herpesviral infection. These findings suggest that natural products could be one of the best choices for development of new treatments for latent herpesvirus infection, and may provide synergistic anti-viral activity when supplemented with nucleoside analogues. Therefore, it is important to identify which natural products are more efficacious anti-herpetic agents, and to understand the molecular mechanism in detail for further advance in the anti-viral therapies.More than 90% of adults have been infected with at least one human herpesvirus, which establish long-term latent infection for the life of the host. While anti-viral drugs exist that limit herpesvirus replication, many of these are ineffective against latent infection. Moreover, drug-resistant strains of herpesvirus emerge following chemotherapeutic treatment. For example, resistance to acyclovir and related nucleoside analogues can occur when mutations arise in either HSV thymidine kinase or DNA polymerases. Thus, there exists an unmet medical need to develop new anti-herpesvirus agents with different mechanisms of action. In this Review, we discuss the promise of anti-herpetic substances derived from natural products including extracts and pure compounds from potential herbal medicines. One example is Glycyrrhizic acid isolated from licorice that shows promising antiviral activity towards human gammaherpesviruses. Secondly, we discuss anti-herpetic mechanisms utilized by several natural products in molecular level. While nucleoside analogues inhibit replicating herpesviruses in lytic replication, some natural products can disrupt the herpesvirus latent infection in the host cell. In addition, natural products can stimulate immune responses against herpesviral infection. These findings suggest that natural products could be one of the best choices for development of new treatments for latent herpesvirus infection, and may provide synergistic anti-viral activity when supplemented with nucleoside analogues. Therefore, it is important to identify which natural products are more efficacious anti-herpetic agents, and to understand the molecular mechanism in detail for further advance in the anti-viral therapies.

The PseEF efflux system is a virulence factor of Pseudomonas syringae pv. syringae

An ATP-binding cassette (ABC) transporter, called the PseEF efflux system, was identified at the left border of the syr-syp genomic island of Pseudomonas syringae pv. syringae strain B301D. The PseEF efflux system was located within a 3.3-kb operon that encodes a periplasmic membrane fusion protein (PseE), and an ABC-type cytoplasmic membrane protein (PseF). The PseEF efflux system exhibited amino acid homology to a putative ABC efflux system (MacAB) of E. coli W3104 with identities of 47.2% (i.e., PseE to MacA) and 57.6% (i.e., PseF to MacB). A nonpolar mutation within the pseF gene was generated by nptII insertional mutagenesis. The resultant mutant strain showed significant reduction in secretion of syringomycin (74%) and syringopeptin (71%), as compared to parental strain B301D. Quantitative real-time RT-PCR was used to determine transcript levels of the syringomycin (syrB1) and syringopeptin (sypA) synthetase genes in strain B301D-HK7 (a pseF mutant). Expression of the sypA gene by mutant strain B301D-HK7 was approximately 6.9% as compared to that of parental strain B301D, while the syrB1 gene expression by mutant strain B301D-HK7 was nearly 14.6%. In addition, mutant strain B301D-HK7 was less virulent by approximately 67% than parental strain B301D in immature cherry fruits. Mutant strain B301D-HK7 was not reduced in resistance to any antibiotics used in this study as compared to parental strain B301D. Expression (transcript levels) of the pseF gene was induced approximately six times by strain B301D grown on syringomycin minimum medium (SRM) supplemented with the plant signal molecules arbutin and D-fructose (SRMAF), as compared to that of strain B301D grown on SRM (in the absence of plant signal molecules). In addition, during infection of bean plants by P. syringae pv. syringae strain B728a, expression of the pseF gene increased at 3 days after inoculation (dai). More than 180-fold induction was observed in transcript levels of the pseF gene by parental strain B728a as compared to strain B728a-SL7 (a salA mutant). Thus, the PseEF efflux system, an ABC-type efflux system, has an important role in secretion of syringomycin and syringopeptin, and is required for full virulence in P. syringae pv. syringae.

High level of viral microRNA-BART20-5p expression is associated with worse survival of patients with Epstein-Barr virus-associated gastric cancer

This study analyzed the relationship between several Epstein-Barr virus (EBV) microRNA (miRNA) expression profiles and the clinicopathologic features of patients with EBV-associated gastric cancer. The miRNA expression was examined in 59 tumor and 39 paired normal mucosal tissues from available formalin-fixed paraffin embedded tissue samples. The expression levels of miR-BamHI fragment A rightward transcript (BART)1-5p, miR-BART4-5p, and miR-BART20-5p were determined using a quantitative real-time polymerase chain reaction. The expression of all three analyzed EBV microRNAs was significantly higher in the tumor tissue than in the paired normal tissue (P < 0.001 for each). When the median value of the EBV microRNA expression levels was used as the cutoff point, a high BART20-5p expression was associated with worse recurrence-free survival (P = 0.034) in a multivariate analysis including age and pathologic stage. In conclusion, the expression level of BART20-5p may predict recurrence-free survival for patients with EBV-associated gastric cancer. Further studies are warranted to clarify the roles of EBV BART microRNAs in the carcinogenesis, and their potential as a biomarker and therapeutic target for EBV-associated gastric cancer.

Anti-influenza effect of Cordyceps militaris through immunomodulation in a DBA/2 mouse model

The immune-modulatory as well as anti-influenza effects of Cordyceps extract were investigated using a DBA/2 mouse model. Three different concentrations of Cordyceps extract, red ginseng extract, or drinking water were orally administered to mice for seven days, and then the mice were intranasally infected with 2009 pandemic influenza H1N1 virus. Body weight changes and survival rate were measured daily post-infection. Plasma IL-12, TNF-α, and the frequency of natural killer (NK) cells were measured on day 4 post-infection. The DBA/2 strain was highly susceptible to H1N1 virus infection. We also found that Cordyceps extract had an antiinfluenza effect that was associated with stable body weight and reduced mortality. The anti-viral effect of Cordyceps extract on influenza infection was mediated presumably by increased IL-12 expression and greater number of NK cells. However, high TNF-α expression after infection of H1N1 virus in mice not receiving treatment with Cordyceps extract suggested a two-sided effect of the extract on host immune regulation.