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Radioresistance has been one of the impediments to effective nasopharyngeal carcinoma (NPC) therapy in clinical settings. Epstein‐Barr virus (EBV) encoded latent membrane protein 1 (LMP1) is expressed in NPC and has potent effects on radioresistance. It has been detected in extracellular vesicles (EVs) or exosomes and shown to promote tumor proliferation and invasive potential. However, whether LMP1‐positive EVs can confer radioresistance to cancer cells and the mechanism used to promote radioresistance need to be elucidated. In this study, the data showed that EVs derived from LMP1‐positive NPC cells could induce recipient NPC cell proliferation and invasion and suppress apoptosis, especially promoting radioresistance. In addition, LMP1 could increase the secretion of LMP1‐positive EVs. Furthermore, transmitted LMP1 subsequently performed its oncogenic functions through activating P38 MAPK signaling in recipient cells, and inhibiting P38 activity could efficaciously restore the sensitivity of NPC cells to ionizing radiation (IR). Finally, we found that LMP1‐positive EVs could promote tumor growth and P38 inhibition eliminates this promoting effect in vivo, and EV formation is associated with a poor prognosis in NPC patients. These results showed that a few cells expressing LMP1 could enhance the radioresistance of NPC cells through potentially impacting the infected host and also modulating the tumor microenvironment. [ABSTRACT FROM AUTHOR]

The ability of the 10-23 DNAzyme to specifically cleave RNA with high efficiency has fuelled expectation that this agent may have useful applications for targeted therapy. Here, we, for the first time, investigated the antitumor and radiosensitizing effects of a DNAzyme (DZ1) targeted to the Epstein-Barr virus (EBV)-LMP1 mRNA of nasopharyngeal carcinoma (NPC) in patients. Preclinical studies indicated that the DNAzyme was safe and well tolerated. A randomized and double-blind clinical study was conducted in 40 NPC patients who received DZ1 or saline intratumorally, in conjunction with radiation therapy. Tumor regression, patient survival, EBV DNA copy number and tumor microvascular permeability were assessed in a 3-month follow-up. The mean tumor regression rate at week 12 was significantly higher in DZ1 treated group than in the saline control group. Molecular imaging analysis showed that DZ1 impacted on tumor microvascular permeability as evidenced by a faster decline of the Ktrans in DZ1-treated patients. The percentage of the samples with undetectable level of EBV DNA copy in the DZ1 group was significantly higher than that in the control group. No adverse events that could be attributed to the DZ1 injection were observed in patients. [ABSTRACT FROM AUTHOR]

The latent membrane protein 1 (LMP1), which is encoded by the Epstein-Barr virus (EBV), is an important oncogenic protein that is closely related to carcinogenesis and metastasis of nasopharyngeal carcinoma (NPC), a prevalent cancer in China. We previously reported that the expression of the functional chemokine receptor CXCR4 is associated with human NPC metastasis. In this study, we show that LMP1 induces tyrosine sulfation of CXCR4 through tyrosylprotein sulfotransferase-1 (TPST-1), an enzyme that is responsible for catalysis of tyrosine sulfation in vivo, which is likely to contribute to the highly metastatic character of NPC. LMP1 could induce tyrosine sulfation of CXCR4 and its associated cell motility and invasiveness in a NPC cell culture model. In contrast, the expression of TPST-1 small interfering RNA reversed LMP1-induced tyrosine sulfation of CXCR4. LMP1 conveys signals through the epidermal growth factor receptor (EGFR) pathway, and EGFR-targeted siRNA inhibited the induction of TPST-1 by LMP1. We used a ChIP assay to show that EGFR could bind to the TPST-1 promoter in vivo under the control of LMP1. A reporter gene assay indicated that the activity of the TPST-1 promoter could be suppressed by deleting the binding site between EGFR and TPST-1. Finally, in human NPC tissues, the expression of TPST-1 and LMP1 was directly correlated and clinically, the expression of TPST-1 was associated with metastasis. These results suggest the up-regulation of TPST-1 and tyrosine sulfation of CXCR4 by LMP1 might be a potential mechanism contributing to NPC metastasis. [ABSTRACT FROM AUTHOR]

Epstein–Barr virus (EBV) reactivation into the lytic cycle plays certain roles in the development of EBV-associated diseases, including nasopharyngeal carcinoma and lymphoma. In this study, we investigated the effects of the tea polyphenol (-)-epigallocatechin-3-gallate (EGCG) on EBV spontaneous lytic infection and the mechanism(s) involved in EBV-positive cells. We found that EGCG could effectively inhibit the constitutive lytic infection of EBV at the DNA, gene transcription and protein levels by decreasing the phosphorylation and activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt. By using cellular signaling pathway-specific inhibitors, we also explored the signaling mechanisms underlying the inhibitory effects of EGCG on EBV spontaneous lytic infection in cell models. Results show that specific inhibitors of Mitogen-Activated Protein Kinase Kinase (MEK) (PD98059) and phosphatidylinositol 3-kinase [PI3-K (LY294002)] markedly downregulated gene transcription and expression of BZLF1 and BMRF1 indicating that the MEK/ERK1/2 and PI3-K/Akt pathways are involved in the EBV spontaneous lytic cycle cascade. Therefore, one of the mechanisms by which EGCG inhibits EBV spontaneous lytic infection appears to involve the suppression of the activation of MEK/ERK1/2 and PI3-K/Akt signaling. [ABSTRACT FROM AUTHOR]

Several reports have demonstrated that Epstein-Barr virus (EBV) encoded latent membrane protein 1 (LMP1), which is transferred by extracellular vesicles (EVs) or exosomes, can promote cancer progression. However, its mechanism is still not fully understood. In the present study, we demonstrated that EV packaged LMP1 can activate normal fibroblasts (NFs) into cancer-associated fibroblasts (CAFs). The NF-κB p65 pathway is the key signal that promotes the activation of NFs to CAFs in nasopharyngeal carcinoma (NPC). In activated CAFs, aerobic glycolysis and autophagy were increased. Moreover, glucose uptake and lactate production were decreased, and mitochondrial activity in tumor cells was enhanced, which supported the Reverse Warburg Effect (RWE). During this process, upregulation of MCT4 in CAFs and MCT1 in tumor cells was observed. The NF-κB p65 pathway also plays an important role in the regulation of MCT4. Furthermore, co-culture with CAFs promoted the proliferation, migration and radiation resistance of NPC cells. And EV packaged LMP1 promoted tumor proliferation and pre-metastatic niche formation by activating CAFs in vivo. Our findings indicate that EV packaged LMP1-activated CAFs promote tumor progression via autophagy and stroma-tumor metabolism coupling. [ABSTRACT FROM AUTHOR]

We conducted this research to explore the role of latent membrane protein 1 (LMP1) encoded by the Epstein-Barr virus (EBV) in modulating the DNA damage response (DDR) and its regulatory mechanisms in radioresistance. Our results revealed that LMP1 repressed the repair of DNA double strand breaks (DSBs) by inhibiting DNA-dependent protein kinase (DNA-PK) phosphorylation and activity. Moreover, LMP1 reduced the phosphorylation of AMP-activated protein kinase (AMPK) and changed its subcellular location after irradiation, which appeared to occur through a disruption of the physical interaction between AMPK and DNA-PK. The decrease in AMPK activity was associated with LMP1-mediated glycolysis and resistance to apoptosis induced by irradiation. The reactivation of AMPK significantly promoted radiosensitivity both in vivo and in vitro. The AMPKα (Thr172) reduction was associated with a poorer clinical outcome of radiation therapy in NPC patients. Our data revealed a new mechanism of LMP1-mediated radioresistance and provided a mechanistic rationale in support of the use of AMPK activators for facilitating NPC radiotherapy. [ABSTRACT FROM AUTHOR]

EBERs (EBER1 and EBER2) are suggested to be involved in cellular transformation and tumor growth. Cytoplasmic pattern recognition receptor-RIG-I, which is characterized by the recognition of viral dsRNAs, could efficiently trigger the downstream pathways of innate immunity. Although some previous reports have shown that EBERs and RIG-I associate with hematological malignancies, the role of EBERs-RIG-I signaling in solid tumors remains to be clarified. Here we demonstrate that EBER mediation of the inflammatory response via RIG-I contributes to NPC development in vitro and in vivo. We first verified that the expression level of RIG-I was associated with EBER transcription in a dose-dependent manner in NPC cells and specimens from NPC patients. Furthermore, pro-inflammatory cytokine transcription and release were sharply reduced after RIG-I knockdown compared with the control shRNA group in the presence of EBERs, accompanied by an attenuation of the NF-κB and MAPK signaling pathways. Consequently, the tumor burden was greatly alleviated in the RIG-I knockdown group in a xenograft model. In addition, macrophage colony-stimulating factor (M-CSF) and monocyte chemoattractant protein (MCP-1), which promote the maturation and attraction of tumor-associated macrophages, were stimulated upon the introduction of EBERs, and this upregulation conceivably led to the tumor-promoting subset transition of the macrophages. Taken together, our results reveal that EBERs could promote NPC progression through RIG-I-mediated cancer-related inflammation. [ABSTRACT FROM AUTHOR]

Abstract: miRNAs (microRNAs) are a class of non-coding small RNAs. The Epstein-Barr-virus (EBV) encoded miR-BHRF1-1 is barely expressed in most nasopharyngeal carcinoma (NPC) cells with EBV latent infection. Here, we used a strategy of overexpression and inhibition of miR-BHRF1-1 and showed that miR-BHRF1-1 is involved in TPA-induced accumulation of EBV lytic proteins and viral copies in late lytic cycle. The data further suggested that the miR-BHRF1-1-potentiated induction of EBV lytic replication was accompanied by inhibiting p53 expression. Our results demonstrated that the EBV original pathogen miR-BHRF1-1 is involved in the control of EBV late lytic replication by directly targeting the host p53 gene. [Copyright &y& Elsevier]

The principal Epstein–Barr virus (EBV) oncoprotein, latent membrane protein 1 (LMP1), has been suggested to contribute to the highly invasive nature of nasopharyngeal carcinoma (NPC). Signal transducer and activator of transcription 3 (STAT3) is a master transcriptional regulator in proliferation and apoptosis and is newly implicated in angiogenesis and invasiveness, which, in turn, are likely to contribute to the highly invasive character of NPC. The fundamental molecular mechanisms of LMP1-regulated STAT3 activation in NPC cell invasion have not been completely explored. Here, we showed that LMP1 signals the Janus kinase 3 (JAK3) and extracellular signal-regulated kinase 1/2 (ERK1/2) pathways upon the activation of STAT3 as well as STAT transactivation activity. LMP1 induces vascular endothelial growth factor (VEGF) expression via the JAK/STAT and mitogen-activated protein kinase (MAPK)/ERK signalling pathways. Induction of STAT3 by the human viral oncoprotein LMP1 may contribute to the invasion of NPC. [Copyright &y& Elsevier]