Evaluation of RNA Secondary Stem-Loop Structures in the UTRs of Mouse Hepatitis Virus as New Therapeutic Targets.

MHV-A59 is a beta-coronavirus that causes demyelinating encephalitis and hepatitis in mice. Recently, the mouse infection model of MHV-A59 has been used as an alternative animal infection model for SARS-CoV and SARS-CoV-2, aiding the development of new antiviral drugs. In this study, the MHV-A59 model was employed to investigate the potential of SARS-CoV-2 UTRs as new targets for antiviral drugs. Optimal targets within the MHV-A59 UTRs were identified using a shRNA and siRNA design tool, focusing on RNA secondary stem-loop (SL) structures in the UTRs. We then examined whether the designed RNAi constructs could inhibit MHV-A59 replication. In the 5'UTR, the stem-loop 1 (SL1) was identified as the most effective target, while in the 3'UTR, the minimal element for the initiation of negative-strand RNA synthesis (MIN) proved to be the most effective. Importantly, siRNAs targeting SL1 and MIN structures significantly reduced total RNA synthesis, negative-strand genomic RNA synthesis, subgenomic (sg) RNA synthesis, viral titer, and the plaque size of MHV-A59 compared to the control. Although not statistically significant, the combination of siSL1 and siMIN had a stronger effect on inhibiting MHV-A59 replication than either siRNA monotherapy. Interestingly, while the SL1 structure is present in both MHV and SARS-CoV-2, the MIN structure is unique to MHV. Thus, the SL1 of SARS-CoV-2 may represent a novel and promising target for RNAi-based antiviral drugs.

Immune Boosting Effect of Limosilactobacillus Reuteri in Immunocompetent C57BL/6J Mice.

Probiotics are well-known to be directly or indirectly involved in the host immune system. In this study, we analyzed the immune-boosting effects of lactic acid bacteria, including Limosilactobacillus and Lactococcus, in immunocompetent C57BL/6J mice. Three different lactic acid bacteria strains were orally administered to C57BL/6J mice for 8 weeks. Then, liver, spleen, and whole blood were harvested after sacrificing the animals. There were no significant changes in whole-body weight, weight of organs, or complete blood cell count by oral administration of lactic acid bacteria. The frequencies of CD3+, CD4+, and CD8+ T cells were significantly increased in the Limosilactobacillus reuteri MG5462 group compared to control. The frequency of NK1.1+ cells was significantly increased in the Lactococcus lactis MG5474 group compared to control. On the other hand, splenocyte proliferations and natural killer cytotoxicity did not differ between groups. In addition, the MG5462 group had a significant increase in the production of TNF-α compared to the control, which is consistent with the upregulation of T cells in the MG5462 group. Therefore, Limosilactobacillus reuteri could be a functional food additive to boost immunity by positively affecting T cell populations.

Role of Interleukin(IL)-6 in NK Activity to Hypoxic-Induced Highly Invasive Hepatocellular Carcinoma(HCC) Cells.

Natural killer (NK) cell dysfunctions against hepatocellular carcinoma (HCC) in a hypoxic environment. Many solid tumors are present in a hypoxic condition, which changes the effector function of various immune cells. The transcription of hypoxic-inducible factors (HIFs) in cancer cells make it possible to adapt to their hypoxic environment and to escape the immune surveillance of NK cells. Recently, the correlation between the transcription of HIF-1α and pro-inflammatory cytokines has been reported. Interleukin (IL)-6 is higher in cancers with a highly invasive ability, and is closely related to the metastasis of cancers. This study showed that the expression of HIF-1α in HCC cells was associated with the presence of IL-6 in the environment of HCC-NK cells. Blocking of IL-6 by antibody in the HCC-NK interaction changed the production of several cytokines including TGF-ß, IL-1, IL-18 and IL-21. Interestingly, in a co-culture of HIF-1α-expressed HCC cells and NK cells, blocking of IL-6 increased the production of IL-21 in their supernatants. In addition, the absence of IL-6 significantly enhanced the cytotoxic ability and the expression of the activating receptors (NKG2D, NKp44, and NKG2C) in NK cells to HIF-1α-expressed HCC cells. These effects might be made by the decreased expression of HIF-1α in HCC cells through the inhibited phosphorylation of STAT3. In conclusion, the absence of IL-6 in the interaction of HIF-1α-expressed HCC cells and NK cells could enhance the antitumor activity of NK cells to HCC cells.

Immune-Enhancing Effects of Limosilactobacillus fermentum in BALB/c Mice Immunosuppressed by Cyclophosphamide.

This study evaluates the immune-enhancing effects of Limosilactobacillus fermentum on cyclophosphamide (CP)-induced immunosuppression in BALB/c mice. In vitro, the expressions of pro-inflammatory cytokines and MAPK signaling molecules in Raw264.7 cells were analyzed by ELISA and Western blot analysis. Moreover, cell proliferation, surface receptor expression, and cytotoxicity of NK-92 cells were examined by Cell Counting Kit-8, CytoTox96 assay, and flow cytometry, respectively. To investigate the immune-enhancing effects of selected L. fermentum strains in vivo, these strains were orally administered to BALB/c mice for 2 weeks, and CP was intraperitoneally injected. Then, liver, spleen, and whole blood were isolated from each animal. Administration of single L. fermentum strains or their mixture sustained the spleen weight, the counts of white blood cells compared to non-fed group. Splenocyte proliferation and NK cytotoxicity were significantly increased in all L. fermentum-fed groups. The frequency of B220+ cells was also significantly enhanced in splenocytes isolated from L. fermentum groups. In addition, the production of cytokines (TNF-α, IFN-γ) and antibodies was recovered in splenocyte supernatants isolated from L. fermentum groups. In conclusion, L. fermentum could be a suitable functional food additive for immune-enhancing effect.

Characterization of a new CCCTC-binding factor binding site as a dual regulator of Epstein-Barr virus latent infection.

Distinct viral gene expression characterizes Epstein-Barr virus (EBV) infection in EBV-producing marmoset B-cell (B95-8) and EBV-associated gastric carcinoma (SNU719) cell lines. CCCTC-binding factor (CTCF) is a structural chromatin factor that coordinates chromatin interactions in the EBV genome. Chromatin immunoprecipitation followed by sequencing against CTCF revealed 16 CTCF binding sites in the B95-8 and SNU719 EBV genomes. The biological function of one CTCF binding site (S13 locus) located on the BamHI A right transcript (BART) miRNA promoter was elucidated experimentally. Microscale thermophoresis assay showed that CTCF binds more readily to the stable form than the mutant form of the S13 locus. EBV BART miRNA clusters encode 22 miRNAs, whose roles are implicated in EBV-related cancer pathogenesis. The B95-8 EBV genome lacks a 11.8-kb EcoRI C fragment, whereas the SNU719 EBV genome is full-length. ChIP-PCR assay revealed that CTCF, RNA polymerase II, H3K4me3 histone, and H3K9me3 histone were more enriched at S13 and S16 (167-kb) loci in B95-8 than in the SNU719 EBV genome. 4C-Seq and 3C-PCR assays using B95-8 and SNU719 cells showed that the S13 locus was associated with overall EBV genomic loci including 3-kb and 167-kb region in both EBV genomes. We generated mutations in the S13 locus in bacmids with or without the 11.8-kb BART transcript unit (BART(+/-)). The S13 mutation upregulated BART miRNA expression, weakened EBV latency, and reduced EBV infectivity in the presence of EcoRI C fragment. Another 3C-PCR assay using four types of BART(+/-)·S13(wild-type(Wt)/mutant(Mt)) HEK293-EBV cells revealed that the S13 mutation decreased DNA associations between the 167-kb region and 3-kb in the EBV genome. Based on these results, CTCF bound to the S13 locus along with the 11.8-kb EcoRI C fragment is suggested to form an EBV 3-dimensional DNA loop for coordinated EBV BART miRNA expression and infectivity.

Anti-Tumor Effect of Heat-Killed Bifidobacterium bifidum on Human Gastric Cancer through Akt-p53-Dependent Mitochondrial Apoptosis in Xenograft Models.

Paraprobiotics, inactivated microbial cells, regulate immune system and exhibit antioxidant and anti-inflammatory activities in patients with weakened immunity or the elderly. This study evaluated the anti-tumor effects of heat-killed Bifidobacterium and Lactobacillus on human gastric cancer MKN1 cells in vitro and in vivo in xenograft animal models. First, cytotoxicity and apoptosis in MKN1 cells of 11 different heat-killed Bifidobacterium or Lactobacillus strains were examined using the MTT assay or flow cytometry, respectively. Then, BALB/c nude mice xenograft animal models were implanted with human gastric cancer MKN1 cells and orally administered a selected single or a mixture of heat-killed bacterial strains to investigate their inhibitory effect on tumor growth. In addition, the expression of p-Akt, p53, Bax, Bak, cleaved caspase-9, -3, and PARP in the tumor tissues was analyzed using Western blotting assay or immunohistochemistry staining. The results show that heat-killed B. bifidum MG731 (MG731), L. reuteri MG5346 (MG5346), and L. rhamnosus MG5200 (MG5200) induced relatively greater apoptosis than other strains in MKN1 cells. Oral administration of a single dose or a mixture of MG731, MG5346, or MG5200 significantly delayed tumor growth, and MG731 had the most effective anti-tumor effect in the xenograft model. Protein expression of p-Akt, p53, Bax, cleaved caspase-3 and -9, and PARP in tumors derived from the xenograft model correlated with the results of the immunohistochemistry staining.

Anti-Tumor Effects of Heat-Killed L. reuteri MG5346 and L. casei MG4584 against Human Colorectal Carcinoma through Caspase-9-Dependent Apoptosis in Xenograft Model.

In this study, we examined the anti-tumor effects of heat-killed Bifidobacterium and Lactobacillus strains on human colorectal carcinoma RKO cells in in vitro and in vivo xenograft models. First, the cytotoxic and apoptotic effects of 11 different strains were examined using an MTT assay and flow cytometry, respectively. Then, xenograft BALB/c nude mice were implanted with RKO cells and orally administered with single or mixed heat-killed bacterial strains to examine their inhibitory effects on tumor growth. Additionally, the levels of cleaved caspase-9, -3, and -7 and PARP in tumor tissues were analyzed using Western blotting or immunohistochemistry staining. The results showed that RKO cells were highly susceptible to heat-killed B. bifidum MG731 and L. reuteri MG5346 and that L. casei MG4584 induced apoptosis to a greater extent than other strains. The oral administration of individual MG731, MG5346, or MG4584 significantly delayed tumor growth, and mixtures of MG5346 and MG4584 or MG731, MG5346, and MG4584 synergistically inhibited the tumor growth in the xenograft model. The expression of cleaved caspase-3, -7, and -9 and PARP in the tumor tissues was increased in Western blotting, and the expression of cleaved caspase-3 and PARP in immunohistochemistry staining was also increased. Therefore, we suggest that the use of the combination of MG5346 and MG4584 as parabiotics could effectively inhibit the growth of colorectal cancer.

Apigenin Increases Natural Killer Cytotoxicity to Human Hepatocellular Carcinoma Expressing HIF-1α through High Interaction of CD95/CD95L.

Natural killer (NK) cell activity is more attenuated in hepatocellular carcinoma (HCC) patients than normal. Hypoxic-inducible factor (HIF)-1α is highly expressed in tumors to maintain their metabolism in a hypoxic environment. The expression of HIF-1α in cancers can lead to cell growth, proliferation, invasion/metastasis and immune escape. Although apigenin, a flavonoid, is known to have various biological activities, it has not been demonstrated in NK cell immune activity in HCC cells. In this study, NK-92 cells were directly cocultured with HCC SK-Hep1 cells for 24 h to evaluate NK cell activity in HCC cells or HCC cells expressing HIF-1α by apigenin. NK cell cytotoxicity to HCC cells expressing HIF-1α was significantly increased, and NK cell-activating receptors, NKG2D, NKp30 and NKp44 were highly expressed. The activating effect of apigenin on NK cells substantially induced apoptosis in HCC cells expressing HIF-1α through high expression of CD95L on the surface of NK-92 cells. Moreover, apigenin excellently inhibited the level of TGF-ß1 in a coculture of NK cells and HCC cells. In conclusion, apigenin seems to be a good compound that increases NK cell cytotoxicity to HCC cells by controlling HIF-1α expression.

NLRP3 Deficiency in Hepatocellular Carcinoma Enhances Surveillance of NK-92 through a Modulation of MICA/B.

Human hepatocellular carcinoma (HCC) is the most common and even worse at prognosis. The patients with HCC which accompanied by other diseases, such as cirrhosis, can be limited in various treatments, such as chemotherapy, not HCC patients without other diseases. NLRP3 inflammasome plays an important role in the innate immune response, but emerging evidence has indicated that the NLRP3 inflammasome is implicated in all stages of cancer development. Various cells express NLRP3 protein through the autocrine or paracrine signaling in their environment, but NK cells do not. The expanding evidence shows that patients who suffer from liver cancers have a low frequency of natural killer (NK) cells, and the function of these cells is also impaired. Thus, we examined how the expression of NLRP3 in HCC cells affects cancer surveillance by NK cells in a state of a co-culture of both cells. When the expression of NLRP3 in HCC cells was ablated, MICA/B on the surface of HCC cells was upregulated through the lowered expression of matrix metalloproteinase. The expression of MICA on the surface of HCC cells interacted with the NKG2D receptor on NK-92 cells, which led to NK cytotoxicity. Furthermore, in a xenograft mice model, NLRP3 KO HCC cells delayed tumor development and metastasis as well as increased the sensitivity to NK cell cytotoxicity. Taken together, NLRP3 KO in HCC could enhance NK immunosurveillance through an interaction of NKG2D-MICA.

Cisplatin Resistance in Epstein-Barr-Virus-Associated Gastric Carcinoma Acquired through ATM Methylation.

Epstein-Barr-virus-associated gastric carcinoma (EBVaGC), first reported in 1992, currently accounts for 10% of all gastric carcinoma worldwide. EBVaGC has unique DNA hypermethylation phenotypes that allow for higher proportions of DNA methylation than any other gastric cancer. CpG islands in the gene promoter region are one of the major regions in which DNA methylation controls gene transcription. Despite cisplatin-based chemotherapy being one of the standard treatment regimens for advanced gastric cancer, including EBVaGC, cisplatin alone or in combination with 5-fluorouracil has been limited by its less potent anticancer activity and the occurrence of cisplatin resistance. Accordingly, the current study evaluated the anticancer activities of a combination of cisplatin and 5-Azacytidine (5-AZA) against EBVaGC. Our findings showed that cisplatin upregulated the DNMT3A gene, whereas shRNA-targeted removal of DNMT3A mRNA contributed to cisplatin-mediated EBV lytic reactivation. Moreover, the removal of DNMT3A mRNA upregulated the ATM gene through DNA demethylation on the ATM promoter. Furthermore, CRISPR/Cas9-targeted removal of the ATM gene resulted in significantly reduced cell susceptibility and EBV lytic reactivation by a combination of cisplatin and DNMT3A inhibitor 5-AZA. Finally, 5-AZA exhibited a synergistic effect with cisplatin in anti-EBV and anti-EBVaGC activities by increasing drug susceptibility and EBV lytic reactivation. The aforementioned results suggest that cisplatin combined with DNA methylation inhibitors could be a novel therapeutic approach for EBVaGC.

Korean Red Ginseng Enhances Immunotherapeutic Effects of NK Cells via Eosinophils in Metastatic Liver Cancer Model.

Metastasis decreases the survival rate of patients with liver cancer. Therefore, novel anti-metastatic strategies are needed. Korean Red Ginseng (KRG) is often ingested as a functional food with an immune-boosting effect. We investigated a combination of KRG and natural killer (NK) cells as a novel immunotherapy approach. SK-Hep1 cells were injected into the tail vein of NRGA mice to establish an experimental metastasis model. KRG, NK cells, or a combination of KRG and NK cells were administered. Tumor growth was observed using an in vivo imaging system, and metastatic lesions were evaluated by histological analysis and immunohistochemistry. Bioluminescence intensity was lower in the KRG and NK cell combination group than in the other groups, indicating that the combination treatment suppressed the progression of metastasis. CD56 expression was used as a NK cell marker and hematological analysis was performed. The combination treatment also decreased the expression of matrix metalloproteinases and the area of metastatic lesions in liver and bone tissues, as well as increased the eosinophil count. Expression of cytokines-related eosinophils and NK cells was determined by Western blotting analysis. The expression of interleukin 33 (IL33) was induced by the combination of KRG and NK cells. High IL33 expression was associated with prolonged overall survival in the Kaplan-Meier plotter. Our results suggest that KRG enhances the immune activity of NK cells by IL-33 through eosinophils and suppresses metastatic liver cancer progression.

Natural killer cells inhibit breast cancer cell invasion through downregulation of urokinase­type plasminogen activator.

Triple­negative breast cancer (TNBC) is one of the most aggressive types of breast cancer, and there is no effective therapeutic target to date. Natural killer (NK) cells are functionally diverse lymphocytes that recognize and kill cancer cells. Although it is clear that NK cells exert antitumor activity in the tumor microenvironment, their role in the aggressive progression of TNBC has not been elucidated in detail. In the present study, we investigated the effect of NK cells on MDA­MB­231 TNBC cells using an indirect co­culture system. The invasive phenotype of MDA­MB­231 cells was significantly inhibited by co­culture with NK cells. Notably, the expression of urokinase­type plasminogen activator (uPA) was markedly reduced by NK cells. Cytokine array analysis showed that the levels of interleukin (IL)­10, IL­6, IL­8, C­C motif ligand (CCL)5, and CCL2 were increased in conditioned media from the co­cultured cells. Among these cytokines, IL­6 played a crucial role in the NK cell­induced uPA downregulation and inhibition of the invasive phenotype of MDA­MB­231 cells and Hs578T cells. We analyzed the Gene Expression Profiling Interactive Analysis database for correlations between IL­6 and uPA with the overall survival of breast cancer patients. The Kaplan­Meier survival analysis revealed that a low IL­6/uPA ratio was associated with the poor survival of breast cancer patients, suggesting it as an important factor for determining the overall survival of breast cancer patients. Taken together, our findings demonstrate that NK cells in the tumor microenvironment inhibit the invasiveness of TNBC cells through the IL­6­mediated inhibition of uPA.

Undaria pinnatifida Fucoidan-Rich Extract Recovers Immunity of Immunosuppressed Mice.

We investigated the immune restoration activity of Undaria pinnatifida fucoidan-rich extract in cyclophosphamide-induced immunosuppressed mice. C57BL/6 mice were intraperitoneally injected with 80 mg/kg of cyclophosphamide (CP) and orally administered with either drinking water (DW), red ginseng extract (RG), or one of three different doses of Undaria pinnatifida fucoidan-rich extract (DSU02 50, 100, and 150 mg/kg). After 14 days, liver, spleen, and whole blood were isolated from each animal. The frequencies of NK and CD3+, CD4+, and CD8+ T cells were significantly increased in splenocytes isolated from the DSU02 100 mg/kg and DSU02 150 mg/kg groups (NK1.1+, 5.4% or 4.9% vs 3.8%; CD3+, 39.3% or 37.9% vs 32.3%; CD4+, 22% or 20.2% vs 17.4%; CD8+, 12.7% or 11.6% vs 10.1%). NK cytotoxicity was enhanced in the DSU02-fed groups at all doses (CP-treated DW, 93.4%; RG, 107.2%; DSU02 50, 107.3%; DSU02 100, 107.3%; DSU02 150, 107.1%), and the proliferation of T cells (CD3+, CD4+, and CD8+) was also greater in the DSU02 100 mg/kg and DSU02 150 mg/kg administered groups compared with the unfed group. Plasma concentrations of TNF-α, IgM, and total IgG from the DSU02 150 mg/kg group were also significantly higher compared with the other groups (TNF- α: CP-treated DW - 21.5 pg/ml, DSU02 150 - 47.1 pg/ml; IgM: CP-treated DW - 82.9 ng/ml, DSU02 150 - 110.8 ng/ml; total IgG: CP-treated DW - 114.4 ng/ml, DSU02 150 - 162.7 ng/ml). We suggest that Undaria pinnatifida fucoidan-rich extract could be a promising candidate for a marine natural immune stimulator.

Quercetin Synergistically Inhibit EBV-Associated Gastric Carcinoma with Ganoderma lucidum Extracts.

Mycotherapy has been shown to improve the overall response rate during cancer treatment and reduce some chemotherapy-related adverse events. Ganoderma lucidum is a traditional mushroom used for pharmaceutical purposes. G. lucidum extracts (GLE) showed potential antitumor activities against several cancers. These tumor inhibitory effects of GLE were attributed to the suppression of the proliferation and metastasis of cancer cells. Epstein-Barr virus (EBV)-associated gastric carcinoma (EBVaGC) is defined as the monoclonal proliferation of carcinoma cells with latent EBV infection. The inhibitory effects of GLE against EBVaGC are questionable. The aim of this study was to investigate GLE as potential antitumor agents and a counterpart of quercetin (QCT) for the cotreatment in suppressing EBVaGC development. Therefore, this study conducted antitumor assays using a EBVaGC xenograft mice model and found that GLE could suppress tumor development. These inhibitory effects were significantly augmented by the low concentration of the quercetin (QCT) cotreatment in the xenograft mice. The addition of GLE in low concentrations synergistically reinforced QCT-induced apoptosis and EBV lytic reactivation. GLE contains various polysaccharides and triterpenes, such as ganoderic acid. Interestingly, the addition of ganoderic acid A (GAA) could produce similar bioactive effects like GLE in QCT-mediated antitumor activity. The GAA addition in low concentrations synergistically reinforced QCT-induced apoptosis and EBV lytic reactivation. GAA was sufficiently effective as much as GLE. Therefore, our results suggested that QCT-supplemented GLE could be a potential food adjunct for the prevention of EBVaGC development.

Antitumor and Anti-Invasive Effect of Apigenin on Human Breast Carcinoma through Suppression of IL-6 Expression.

Interleukin (IL)-6 plays a crucial role in the progression, invasion, and metastasis of breast cancer. Triple-negative breast cancer (TNBC) cell line MDA-MB-231 is known for its aggressive metastasis. Epithelial to mesenchymal transition (EMT) is a critical process in cancer metastasis. The positive correlation between IL-6 and EMT in tumor microenvironment is reported. We found significantly upregulated IL-6 expression in MDA-MB-231 cells. A blockade of IL-6 expression decreased levels of phosphorylated signal transducer and activator of transcription 3 (pSTAT3), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K), phosphorylated protein kinase B (pAkt), and cell cycle-related molecules, including cyclin-dependent kinases (CDKs) and cyclins in MDA-MB-231 cells. A short-hairpin RNA (shRNA)-mediated blockade of IL-6 expression inhibited migration and N-cadherin expression and induced E-cadherin expression in MDA-MB-231 cells. Growth rate was slower for the tumors derived from IL-6 shRNA-treated MDA-MB-231 cells than for those derived from control shRNA-treated MDA-MB-231 cells. The expression of pSTAT3, phosphorylated extracellular signal-regulated kinase (pERK), PI3K, pAkt, snail, vimentin, and N-cadherin was significantly lower in tumors from IL-6 shRNA-treated MDA-MB cells. In addition, apigenin treatment significantly inhibited the growth of MDA-MB-231-derived xenograft tumors along with the protein expressions of pSTAT3, pERK, IL-6, PI3K, pAkt, and N-cadherin. Our results demonstrate that the anti-invasive effect of apigenin in MDA-MB-231-derived xenograft tumors is mediated by the inhibition of IL-6-linked downstream signaling pathway.

Adenosine Induces EBV Lytic Reactivation through ADORA1 in EBV-Associated Gastric Carcinoma.

Cordyceps species are known to contain numerous bioactive compounds, including cordycepin. Extracts of Cordyceps militaris (CME) are used in diverse medicinal purposes because of their bioactive components. Cordycepin, one of the active components of CME, exhibits anti-proliferative, pro-apoptotic, and anti-inflammatory effects. Cordycepin structurally differs from adenosine in that its ribose lacks an oxygen atom at the 3' position. We previously reported that cordycepin suppresses Epstein⁻Barr virus (EBV) gene expression and lytic replication in EBV-associated gastric carcinoma (EBVaGC). However, other studies reported that cordycepin induces EBV gene expression and lytic reactivation. Thus, it was reasonable to clarify the bioactive effects of CME bioactive compounds on the EBV life cycle. We first confirmed that CME preferentially induces EBV gene expression and lytic reactivation; second, we determined that adenosine in CME induces EBV gene expression and lytic reactivation; third, we discovered that the adenosine A1 receptor (ADORA1) is required for adenosine to initiate signaling for upregulating BZLF1, which encodes for a key EBV regulator (Zta) of the EBV lytic cycle; finally, we showed that BZLF1 upregulation by adenosine leads to delayed tumor development in the EBVaGC xenograft mouse model. Taken together, these results suggest that adenosine is an EBV lytic cycle inducer that inhibits EBVaGC development.

Cytokine-Modulated Natural Killer Cells Differentially Regulate the Activity of the Hepatitis C Virus.

HCV genotype 2a strain JFH-1 replicates and produces viral particles efficiently in human hepatocellular carcinoma (huh) 7.5 cells, which provide a stable in vitro cell infection system for the hepatitis C virus (HCVcc system). Natural killer (NK) cells are large lymphoid cells that recognize and kill virus-infected cells. In this study, we investigated the interaction between NK cells and the HCVcc system. IL-10 is a typical immune regulatory cytokine that is produced mostly by NK cells and macrophages. IL-21 is one of the main cytokines that stimulate the activation of NK cells. First, we used anti-IL-10 to neutralize IL-10 in a coculture of NK cells and HCVcc. Anti-IL-10 treatment increased the maturation of NK cells by enhancing the frequency of the CD56+dim population in NK-92 cells. However, with anti-IL-10 treatment of NK cells in coculture with J6/JFH-1-huh 7.5 cells, there was a significant decrease in the expression of STAT1 and STAT5 proteins in NK-92 cells and an increase in the HCV Core and NS3 proteins. In addition, rIL-21 treatment increased the frequency of the CD56+dim population in NK-92 cells, Also, there was a dramatic increase in the expression of STAT1 and STAT5 proteins in rIL-21 pre-stimulated NK cells and a decrease in the expression of HCV Core protein in coculture with J6/JFH-1-huh 7.5 cells. In summary, we found that the functional activation of NK cells can be modulated by anti-IL-10 or rIL-21, which controls the expression of HCV proteins as well as HCV RNA replication.

Phylogenetic comparison of Epstein-Barr virus genomes.

Technologies used for genome analysis and whole genome sequencing are useful for us to understand genomic characterization and divergence. The Epstein-Barr virus (EBV) is an oncogenic virus that causes diverse diseases such as Burkitt's lymphoma (BL), nasopharyngeal carcinoma (NPC), Hodgkin's lymphoma (HL), and gastric carcinoma (GC). EBV genomes found in these diseases can be classified either by phases of EBV latency (type-I, -II, and -III latency) or types of EBNA2 sequence difference (type-I EBV, type-II EBV or EBV-1, EBV-2). EBV from EBV-transformed lymphoblastoid cell line (LCL) establishes type-III latency, EBV from NPC establishes type-II latency, and EBV from GC establishes type-I latency. However, other important factors play key roles in classifying numerous EBV strains because EBV genomes are highly diverse and not phylogenetically related to types of EBV-associated diseases. Herein, we first reviewed previous studies to describe molecular characteristics of EBV genomes. Then, using comparative and phylogenetic analyses, we phylogenetically analyzed molecular variations of EBV genomes and proteins. The review of previous studies and our phylogenetic analysis showed that EBV genomes and proteins were highly diverse regardless of types of EBV-associated diseases. Other factors should be considered in determining EBV taxonomy. This review will be helpful to understand complicated phylogenetic relationships of EBV genomes.

Improved Anti-Cancer Effect of Curcumin on Breast Cancer Cells by Increasing the Activity of Natural Killer Cells.

Curcumin is known to possess various biological functions, including anti-inflammatory, antioxidative, and anti-cancer activities. Natural killer (NK) cells are large lymphocytes that directly kill cancer cells. However, many aggressive cancers, including breast cancer, were reported to escape the successful killing of NK cells in a tumor microenvironment. In this study, we investigated the anti-cancer effect of curcumin in coculture of human breast carcinoma MDA-MB-231 and NK (NK-92) cells. We found that curcumin had an immune-stimulatory effect on NK-92 by increasing the surface expression of the CD16⁺ and CD56dim population of NK-92. We confirmed that the cytotoxic effect of NK-92 on MDA-MB-231 was significantly enhanced in the presence of curcumin, which was highly associated with the activation of Stat4 and Stat5 proteins in NK-92. Finally, this improved anticancer effect of curcumin was correlated with decreased expression of pErk and PI3K in MDA-MB-231.

Natural killer cells and tumor metastasis.

Natural killer (NK) cells are cytotoxic lymphocytes that recognize tumor cells or stressed cells through 'missing-self' signals, such as altered or absent expression of MHC class I molecules. The function of NK cells is regulated by the activation or inhibition of receptors present on their surface. The activation of NK cells results in cytotoxic activity on target cells through release of toxic granules and inflammatory cytokines. However, NK cells infiltrating tumors have been frequently shown to exhibit a skewed phenotype that includes decreased antitumor activity and enhanced protumor activities, such as angiogenesis and metastasis. In fact, many studies have reported that tumor microenvironments induce a protumor phenotype in NK cells. Here, we review the biological properties of NK cells in the context of tumorigenesis and tumor progression, with a specific focus on the interactions between NK cells and critical tumor microenvironments, such as epithelial-to-mesenchymal transition, matrix metalloproteinases, and tumor-associated chronic inflammation in tumor metastasis.