Interference effect of epigallocatechin-3-gallate on targets of nuclear factor kappaB signal transduction pathways activated by EB virus encoded latent membrane protein 1

EGCG Inhibits Proliferation and Induces Apoptosis Through Downregulation of SIRT1 in Nasopharyngeal Carcinoma Cells

Epigallocatechin-3-gallate (EGCG), a frequently studied catechin in green tea, has been shown involved in the anti-proliferation and apoptosis of human nasopharyngeal carcinoma (NPC) cells. However, the underlying molecular mechanism of the apoptotic effects of EGCG has not been fully investigated. Recent literature emphasized the importance of Sirtuin 1 (SIRT1), an NAD⁺-dependent protein deacetylase, in regulating cellular stress responses, survival, and organismal lifespan. Herein, the study showed that EGCG could significantly inhibit cell proliferation and promote apoptosis of 2 NPC (CNE-2 and 5-8F) cell lines. Moreover, it was also found that SIRT1 is down-regulated by EGCG, and the SIRT1-p53 signaling pathway participates in the effects of EGCG on CNE-2 and 5-8 F cells. Taken together, the findings of this study provided evidence that EGCG could inhibit the growth of NPC cell lines and is linked with the inhibition of the SIRT1-p53 signaling pathway, suggesting the therapeutic potential of EGCG in human NPC.

Knockout of TRPV1 Exacerbates Ischemia-reperfusion-induced Renal Inflammation and Injury in Obese Mice

BACKGROUND/AIM

Transient receptor potential vanilloid type 1 (TRPV1) has anti-inflammatory properties. The present study aimed to investigate the role of TRPV1 in renal inflammatory responses and tissue injury following renal ischemia-reperfusion (I/R) in diet-induced obese mice.

MATERIALS AND METHODS

TRPV1 knockout and wild type mice were fed a normal or western diet (WD) for 23 weeks and were then subjected to renal I/R injury.

RESULTS

TRPV1 knockout mice showed enhanced WD-induced renal macrophage infiltration and collagen deposition. Knocking out TRPV1 exacerbated renal I/R-induced increase of malondialdehyde, interleukin-6, monocyte chemoattractant protein-1, and NF-ĸB in obese mice. Similar results were observed in the expression of phosphorylated Smad1 and Smad2/3. Blockade of calcitonin gene-related peptide (CGRP) receptors with CGRP8-37 worsened the I/R-induced renal inflammation and injury.

CONCLUSION

Our data indicate that preserving TRPV1 expression and function may prevent renal I/R injury in obesity likely through alleviating inflammatory responses.

EBV-LMP1 targeted DNAzyme enhances radiosensitivity by inhibiting tumor angiogenesis via the JNKs/HIF-1 pathway in nasopharyngeal carcinoma

LMP1, which is encoded by the Epstein-Barr virus, is proposed to be one of the major oncogenic factors involved in nasopharyngeal carcinoma (NPC). Previous studies demonstrated that down-regulation of LMP1 by LMP1-targeted DNAzyme (DZ1) increases the radiosensitivity of NPC. However, the mechanism by which DZ1 contributes to this radiosensitivity remains unclear. In this study, we determined whether a DZ1 blockade of LMP1 expression has an overall positive effect on the radiotherapy of NPCs by repressing HIF-1/VEGF activity and to investigate the mechanisms underlying LMP1-induced HIF-1 activation in NPC cells. The results showed that DZ1 inhibited the microtubule-forming ability of HUVECs co-cultured with NPC cells, which occurs with the down-regulation of VEGF expression and secretion. Moreover, LMP1 increases phosphorylated JNKs/c-Jun signaling, which is involved in the regulation of HIF-1/VEGF activity. After silencing LMP1 and decreasing phosphorylation of JNKs, NPC cells exhibited an enhanced radiosensitivity. Furthermore, in vivo experiments revealed a significant inhibition of tumor growth and a marked reduction of the Ktrans parameter, which reflects the condition of tumor micro-vascular permeability. Taken together, our data suggested that VEGF expression is increased by LMP1 through the JNKs/c-Jun signaling pathway and indicated that DZ1 enhances the radiosensitivity of NPC cells by inhibiting HIF-1/VEGF activity.

The Brain NO Levels and NOS Activities Ascended in the Early and Middle Stages and Descended in the Terminal Stage in Scrapie-Infected Animal Models

The infections of prion agents may cause progressive and fatal neurodegenerative diseases in humans and a serial of animal species. Previous studies have proposed that the levels of nitric oxide (NO) and nitric oxide synthase (NOS) in the brains of some neurodegeneration diseases changed, while S-nitrosylation (SNO) of many brain proteins altered in prion diseases. To elucidate the potential changes of brain NO levels during prion infection, the NO levels and NOS activities in the brain tissues of three scrapie experimental rodents were measured, including scrapie agent 263 K-infected hamsters and 139A- and ME7-infected mice. Both NO levels and NOS activities, including total NOS (TNOS) and inducible NOS (iNOS), were increased at the terminal stages of scrapie-infected animals. Assays of the brain samples collected at different time points during scrapie infection showed that the NO levels and NOS activities started to increase at early stage, reached to the peak in the middle stage, and dropped down at late stage. Western blots for brain iNOS revealed increased firstly and decreased late, especially in the brains of 139A- and ME7-infected mice. In line with those alterations, the levels of the SNO forms of several selected brain proteins such as aquaporin-1 (AQP1), calcium/calmodulin-dependent protein kinase II (CaMKII), neurogranin, and opalin, underwent similar changing trends, while their total protein levels did not change obviously during scrapie infection. Our data here for the first time illustrate the changing profile of brain NO and NOS during prion infection. Time-dependent alterations of brain NO level and the associated protein S-nitrosylation process may contribute greatly to the neuropathological damage in prion diseases.

Role of Viral miRNAs and Epigenetic Modifications in Epstein-Barr Virus-Associated Gastric Carcinogenesis

MicroRNAs are short (21–23 nucleotides), noncoding RNAs that typically silence posttranscriptional gene expression through interaction with target messenger RNAs. Currently, miRNAs have been identified in almost all studied multicellular eukaryotes in the plant and animal kingdoms. Additionally, recent studies reported that miRNAs can also be encoded by certain single-cell eukaryotes and by viruses. The vast majority of viral miRNAs are encoded by the herpesviruses family. These DNA viruses including Epstein-Barr virus encode their own miRNAs and/or manipulate the expression of cellular miRNAs to facilitate respective infection cycles. Modulation of the control pathways of miRNAs expression is often involved in the promotion of tumorigenesis through a specific cascade of transduction signals. Notably, latent infection with Epstein-Barr virus is considered liable of causing several types of malignancies, including the majority of gastric carcinoma cases detected worldwide. In this review, we describe the role of the Epstein-Barr virus in gastric carcinogenesis, summarizing the functions of the Epstein-Barr virus-encoded viral proteins and related epigenetic alterations as well as the roles of Epstein-Barr virus-encoded and virally modulated cellular miRNAs.

Chemosensitization of solid tumors by inhibition of Bcl-xL expression using DNAzyme

DNAzymes are a novel class of gene suppressors that selectively bind to an RNA substrate by Watson-Crick base pairing and cleave phosphodiester bonds. To explore the potential for therapeutic use of catalytic DNA molecules, active DNAzymes targeting the bcl-xL gene were generated through a multiplex in vitro selection. The DNAzyme-mediated down-regulation of the bcl-xL expression was demonstrated in various cancer cell lines by Western blots. Treatment of the cells with the active DNAzyme led to increases in percentage of apoptotic cells and cytochrome c release from mitochondria, a hall marker of apoptosis. When combined with chemotherapeutics such as Taxol, the DNAzyme significantly sensitised a panel of cancer cells to apoptosis as measured by cell survival assay. In Taxol-resistant cells, down-regulation of bcl-xL expression by the DNAzyme reversed the chemo-resistant phenotype of the cancer cells. In a xenograft mouse model, the DNAzyme was delivered into the tumors via an ALZET osmotic pump and shown to chemosensitize PC3 tumor when treating with Taxol. The results from the present study demonstrate that bcl-xL DNAzyme treatment facilitates apoptosis in solid tumors and suggest the potential use of bcl-xL DNAzyme in combination with chemotherapeutics for cancer therapy.

EGCG inhibits proliferation, invasiveness and tumor growth by up-regulation of adhesion molecules, suppression of gelatinases activity, and induction of apoptosis in nasopharyngeal carcinoma cells

(-)-Epigallocatechin-3-gallate (EGCG), a major green tea polyphenol, has been shown to inhibit the proliferation of a variety of tumor cells. Epidemiological studies have shown that drinking green tea can reduce the incidence of nasopharyngeal carcinoma (NPC), yet the underlying mechanism is not well understood. In this study, the inhibitory effect of EGCG was tested on a set of Epstein Barr virus-negative and -positive NPC cell lines. Treatment with EGCG inhibited the proliferation of NPC cells but did not affect the growth of a non-malignant nasopharyngeal cell line, NP460hTert. Moreover, EGCG treated cells had reduced migration and invasive properties. The expression of the cell adhesion molecules E-cadherin and β-catenin was found to be up-regulated by EGCG treatment, while the down-regulation of matrix metalloproteinases (MMP)-2 and MMP-9 were found to be mediated by suppression of extracellular signal-regulated kinase (ERK) phosphorylation and AP-1 and Sp1 transactivation. Spheroid formation by NPC cells in suspension was significantly inhibited by EGCG. Oral administration of EGCG was capable of suppressing tumor growth in xenografted mice bearing NPC tumors. Treatment with EGCG was found to elevate the expression of p53 and p21, and eventually led to apoptosis of NPC cells via caspase 3 activation. The nuclear translocation of NF-κB and β-catenin was also suppressed by EGCG treatment. These results indicate that EGCG can inhibit the proliferation and invasiveness, and induce apoptosis, of NPC cells, making it a promising agent for chemoprevention or adjuvant therapy of NPC.

Chemoprevention of head and neck squamous cell carcinoma through inhibition of NF-κB signaling

Nuclear factor-kappa B (NF-κB) transcription factors regulate cellular processes such as inflammation and cell survival. The NF-κB pathway is often activated with development and progression of head and neck squamous cell carcinoma (HNSCC). As such, NF-κB represents an attractive target for chemoprevention. HNSCC involves progression of lesions from premalignant to malignant, providing a window of opportunity for intervention with chemopreventive agents. Appropriate chemopreventive agents should be inexpensive, nontoxic, and target important pathways involved in the development of HNSCC. Several such agents that inhibit the NF-κB pathway have been investigated in HNSCC. Retinoids have been studied most extensively but have shown limited potential in human trials. Epidermal growth factor receptor inhibitors and PI3K-mTOR inhibitors may benefit a subset of patients. Other agents such as green tea extract and curcumin are appealing because they are generally regarded as safe. In contrast, there is evidence that Vitamin E supplementation may actually increase mortality of cancer patients. Repurposed drugs such as cyclooxygenase (COX) inhibitors and antidiabetic drugs are an emerging area of interest. Future research to develop agents with lower toxicity and higher specificity for the NF-κB pathway, and to target these therapies to individual patient genetic signatures should help to increase the utility of chemoprevention in HSNCC.

Down-regulation of EBV-LMP1 radio-sensitizes nasal pharyngeal carcinoma cells via NF-κB regulated ATM expression

Background

The latent membrane protein 1 (LMP1) encoded by EBV is expressed in the majority of EBV-associated human malignancies and has been suggested to be one of the major oncogenic factors in EBV-mediated carcinogenesis. In previous studies we experimentally demonstrated that down-regulation of LMP1 expression by DNAzymes could increase radiosensitivity both in cells and in a xenograft NPC model in mice.

Results

In this study we explored the molecular mechanisms underlying the radiosensitization caused by the down-regulation of LMP1 in nasopharyngeal carcinoma. It was confirmed that LMP1 could up-regulate ATM expression in NPCs. Bioinformatic analysis of the ATM ptomoter region revealed three tentative binding sites for NF-κB. By using a specific inhibitor of NF-κB signaling and the dominant negative mutant of IkappaB, it was shown that the ATM expression in CNE1-LMP1 cells could be efficiently suppressed. Inhibition of LMP1 expression by the DNAzyme led to attenuation of the NF-κB DNA binding activity. We further showed that the silence of ATM expression by ATM-targeted siRNA could enhance the radiosensitivity in LMP1 positive NPC cells.

Conclusions

Together, our results indicate that ATM expression can be regulated by LMP1 via the NF-κB pathways through direct promoter binding, which resulted in the change of radiosensitivity in NPCs.