Modulation of the tumor microenvironment by Epstein-Barr virus latent membrane protein 1 in nasopharyngeal carcinoma

Soluble CD27 as a predictive biomarker for intra-tumoral CD70/CD27 interaction in nasopharyngeal carcinoma

In CD70-expressing tumors, the interaction of CD70 on tumor cells with its lymphocyte receptor, CD27, is thought to play a role in immunosuppression in the tumor microenvironment and elevated serum levels of soluble CD27 (sCD27). Previous studies showed that CD70 is expressed in nasopharyngeal carcinoma (NPC), an Epstein-Barr virus (EBV)-related malignancy. However, the association between intratumoral CD70/CD27 expression and serum levels of sCD27 in NPC remains unclear. In the present study, we show that CD70 is primarily expressed by tumor cells in NPC and that CD27-positive lymphocytes infiltrate around tumor cells. NPC patients with CD27-positive lymphocytes had significantly better prognosis than patients lacking these cells. In addition, high CD70 expression by tumor cells tended to be correlated with shorter survival in NPC patients with CD27-positive lymphocytes. Serum sCD27 levels were significantly increased in patients with NPC and provided good diagnostic accuracy for discriminating patients from healthy individuals. The concentration of serum sCD27 in patients with CD70-positive NPC with CD27-positive lymphocytes was significantly higher than in patients with tumors negative for CD70 and/or CD27, indicating that the intratumoral CD70/CD27 interaction boosts the release of sCD27. Furthermore, positive expression of CD70 by NPC cells was significantly correlated with EBV infection. Our results suggest that CD70/CD27-targeted immunotherapies may be promising treatment options and that sCD27 may become an essential tool for evaluating the applicability of these therapies by predicting the intratumoral CD70/CD27 interaction in NPC.

Could MMP3 and MMP9 Serve as Biomarkers in EBV-Related Oropharyngeal Cancer

The high incidence of, and mortality from, head and neck cancers (HNCs), including those related to Epstein-Barr virus (EBV), constitute a major challenge for modern medicine, both in terms of diagnosis and treatment. Therefore, many researchers have made efforts to identify diagnostic and prognostic factors. The aim of this study was to evaluate the diagnostic usefulness of matrix metalloproteinase 3 (MMP 3) and matrix metalloproteinase 9 (MMP 9) in EBV positive oropharyngeal squamous cell carcinoma (OPSCC) patients. For this purpose, the level of these MMPs in the serum of patients with EBV-positive OPSCC was analyzed in relation to the degree of histological differentiation and TNM classification. Our research team's results indicate that the level of both MMPs is much higher in the EBV positive OPSCC patients compared to the EBV negative and control groups. Moreover, their levels were higher in more advanced clinical stages. Considering the possible correlation between the level of MMP 3, MMP 9 and anti-EBV antibodies, and also viral load, after statistical analysis using multiple linear regression, their high correlation was demonstrated. The obtained results confirm the diagnostic accuracy for MMP 3 and MMP 9. Both MMPs may be useful in the diagnosis of EBV positive OPSCC patients.

The Role of LMP1 in Epstein-Barr Virus-associated Gastric Cancer

EBV promotes many cancers such as lymphoma, nasopharyngeal carcinoma, and gastric; Latent Membrane Protein 1 (LMP1) is considered to be a major oncogenic protein encoded by Epstein- Barr virus (EBV). LMP1 functions as a carcinogen in lymphoma and nasopharyngeal carcinoma, and LMP1 may also promote gastric cancer. The expression level of LMP1 in host cells is a key determinant in tumorigenesis and maintenance of virus specificity. By promoting cell immortalization and cell transformation, promoting cell proliferation, affecting immunity, and regulating cell apoptosis, LMP1 plays a crucial tumorigenic role in epithelial cancers. However, very little is currently known about LMP1 in Epstein-Barr virus-associated gastric cancer (EBVaGC); the main reason is that the expression level of LMP1 in EBVaGC is comparatively lower than other EBV-encoded proteins, such as The Latent Membrane Protein 2A (LMP2A), Epstein-Barr nuclear antigen 1 (EBNA1) and BamHI-A rightward frame 1 (BARF1), to date, there are few studies related to LMP1 in EBVaGC. Recent studies have demonstrated that LMP1 promotes EBVaGC by affecting The phosphatidylinositol 3-kinase- Akt (PI3K-Akt), Nuclear factor-kappa B (NF-κB), and other signaling pathways to regulate many downstream targets such as Forkhead box class O (FOXO), C-X-C-motif chemokine receptor (CXCR), COX-2 (Cyclooxygenase-2); moreover, the gene methylation induced by LMP1 in EBVaGC has become one of the characteristics that distinguish this gastric cancer (GC) from other types of gastric cancer and LMP1 also promotes the formation of the tumor microenvironment (TME) of EBVaGC in several ways. This review synthesizes previous relevant literature, aiming to highlight the latest findings on the mechanism of action of LMP1 in EBVaGC, summarize the function of LMP1 in EBVaGC, lay the theoretical foundation for subsequent new research on LMP1 in EBVaGC, and contribute to the development of novel LMP1-targeted drugs.

Recent Advances in Assessing the Clinical Implications of Epstein-Barr Virus Infection and Their Application to the Diagnosis and Treatment of Nasopharyngeal Carcinoma

Reports about the oncogenic mechanisms underlying nasopharyngeal carcinoma (NPC) have been accumulating since the discovery of Epstein-Barr virus (EBV) in NPC cells. EBV is the primary causative agent of NPC. EBV-host and tumor-immune system interactions underlie the unique representative pathology of NPC, which is an undifferentiated cancer cell with extensive lymphocyte infiltration. Recent advances in the understanding of immune evasion and checkpoints have changed the treatment of NPC in clinical settings. The main EBV genes involved in NPC are LMP1, which is the primary EBV oncogene, and BZLF1, which induces the lytic phase of EBV. These two multifunctional genes affect host cell behavior, including the tumor-immune microenvironment and EBV behavior. Latent infections, elevated concentrations of the anti-EBV antibody and plasma EBV DNA have been used as biomarkers of EBV-associated NPC. The massive infiltration of lymphocytes in the stroma suggests the immunogenic characteristics of NPC as a virus-infected tumor and, at the same time, also indicates the presence of a sophisticated immunosuppressive system within NPC tumors. In fact, immune checkpoint inhibitors have shown promise in improving the prognosis of NPC patients with recurrent and metastatic disease. However, patients with advanced NPC still require invasive treatments. Therefore, there is a pressing need to develop an effective screening system for early-stage detection of NPC in patients. Various modalities, such as nasopharyngeal cytology, cell-free DNA methylation, and deep learning-assisted nasopharyngeal endoscopy for screening and diagnosis, have been introduced. Each modality has its advantages and disadvantages. A reciprocal combination of these modalities will improve screening and early diagnosis of NPC.

Epstein-Barr Virus Promotes Oral Squamous Cell Carcinoma Stemness through the Warburg Effect

Epstein-Barr virus (EBV) is associated with various human malignancies. An association between EBV infection and oral squamous cell carcinoma (OSCC) has recently been reported. We established EBV-positive OSCC cells and demonstrated that EBV infection promoted OSCC progression. However, the mechanisms by which EBV promotes OSCC progression remain poorly understood. Therefore, we performed metabolic analyses of EBV-positive OSCC cells and established a xenograft model to investigate the viral contribution to OSCC progression. Here, we demonstrated that EBV infection induced mitochondrial stress by reducing the number of mitochondrial DNA (mtDNA) copies. Microarray data from EBV-positive OSCC cells showed altered expression of glycolysis-related genes, particularly the upregulation of key genes involved in the Warburg effect, including LDHA, GLUT1, and PDK1. Furthermore, lactate production and LDH activity were elevated in EBV-positive OSCC cells. EBV infection significantly upregulated the expression levels of cancer stem cell (CSC) markers such as CD44 and CD133 in the xenograft model. In this model, tumor growth was significantly increased in EBV-positive SCC25 cells compared with that in uninfected cells. Furthermore, tumorigenicity increased after serial passages of EBV-positive SCC25 tumors. This study revealed the oncogenic role of EBV in OSCC progression by inducing the Warburg effect and cancer stemness.

Shifted-excitation Raman difference spectroscopy for improving in vivo detection of nasopharyngeal carcinoma

A strong fluorescence background is one of the common interference factors of Raman spectroscopic analysis in biological tissue. This study developed an endoscopic shifted-excitation Raman difference spectroscopy (SERDS) system for real-time in vivo detection of nasopharyngeal carcinoma (NPC) for the first time. Owing to the use of the SERDS method, the high-quality Raman signals of nasopharyngeal tissue could be well extracted and characterized from the complex raw spectra by removing the fluorescence interference signals. Significant spectral differences relating to proteins, phospholipids, glucose, and DNA were found between 42 NPC and 42 normal tissue sites. Using linear discriminant analysis, the diagnostic accuracy of SERDS for NPC detection was 100%, which was much higher than that of raw Raman spectroscopy (75.0%), showing the great potential of SERDS for improving the accurate in vivo detection of NPC.

Tegument proteins of Epstein-Barr virus: Diverse functions, complex networks, and oncogenesis

The tegument is the structure between the envelope and nucleocapsid of herpesvirus particles. Viral (and cellular) proteins accumulate to create the layers of the tegument. Some Epstein-Barr virus (EBV) tegument proteins are conserved widely in Herpesviridae, but others are shared only by members of the gamma-herpesvirus subfamily. As the interface to envelope and nucleocapsid, the tegument functions in virion morphogenesis and budding of the nucleocapsid during progeny production. When a virus particle enters a cell, enzymes such as kinase and deubiquitinase, and transcriptional activators are released from the virion to promote virus infection. Moreover, some EBV tegument proteins are involved in oncogenesis. Here, we summarize the roles of EBV tegument proteins, in comparison to those of other herpesviruses.

STIM1-regulated exosomal EBV-LMP1 empowers endothelial cells with an aggressive phenotype by activating the Akt/ERK pathway in nasopharyngeal carcinoma

BACKGROUND

Stromal interaction molecule 1 (STIM1)-mediated Ca²⁺ signaling regulates tumor angiogenesis in nasopharyngeal carcinoma (NPC), an Epstein-Barr virus (EBV)-related human malignancy. However, the mechanism by which STIM1 modulates endothelial functional phenotypes contributing to tumor angiogenesis remains elusive.

METHODS

NPC cell-derived exosomes were isolated via differential centrifugation and observed using transmission electron microscopy. Exosome particle sizes were assessed by nanoparticle tracking analysis (NTA). Uptake of exosomes by recipient ECs was detected by fluorescent labeling of the exosomes with PKH26. Tumor angiogenesis-associated profiles were characterized by determining cell proliferation, migration, tubulogenesis and permeability in human umbilical vein endothelial cells (HUVECs). Activation of the Akt/ERK pathway was assessed by detecting the phosphorylation levels using Western blotting. A chick embryo chorioallantoic membrane (CAM) xenograft model was employed to study tumor-associated neovascularization in vivo.

RESULTS

We found that NPC cell-derived exosomes harboring EBV-encoded latent membrane protein 1 (LMP1) promoted proliferation, migration, tubulogenesis and permeability by activating the Akt/ERK pathway in ECs. STIM1 silencing reduced LMP1 enrichment in NPC cell-derived exosomes, thereby reversing its pro-oncogenic effects in an Akt/ERK pathway-dependent manner. Furthermore, STIM1 knockdown in NPC cells blunted tumor-induced vascular network formation and inhibited intra-tumor neovascularization in the chorioallantoic membrane (CAM) xenograft model.

CONCLUSION

STIM1 regulates tumor angiogenesis by controlling exosomal EBV-LMP1 delivery to ECs in the NPC tumor microenvironment. Blocking exosome-mediated cell-to-cell horizontal transfer of EBV-associated oncogenic signaling molecules may be an effective therapeutic strategy for NPC.

Repression of DERL3 via DNA methylation by Epstein-Barr virus latent membrane protein 1 in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is Epstein-Barr virus (EBV)-associated invasive malignancy. Increasing evidence indicates that epigenetic abnormalities, including DNA methylation, play important roles in the development of NPC. In particular, the EBV principal oncogene, latent membrane protein 1 (LMP1), is considered a key factor in inducing aberrant DNA methylation of several tumour suppressor genes in NPC, although the mechanism remains unclear. Herein, we comprehensively analysed the methylome data of Infinium BeadArray from 51 NPC and 52 normal nasopharyngeal tissues to identify LMP1-inducible methylation genes. Using hierarchical clustering analysis, we classified NPC into the high-methylation, low-methylation, and normal-like subgroups. We defined high-methylation genes as those that were methylated in the high-methylation subgroup only and common methylation genes as those that were methylated in both high- and low-methylation subgroups. Subsequently, we identified 715 LMP1-inducible methylation genes by observing the methylome data of the nasopharyngeal epithelial cell line with or without LMP1 expression. Because high-methylation genes were enriched with LMP1-inducible methylation genes, we extracted 95 high-methylation genes that overlapped with the LMP1-inducible methylation genes. Among them, we identified DERL3 as the most significantly methylated gene affected by LMP1 expression. DERL3 knockdown in cell lines resulted in significantly increased cell proliferation, migration, and invasion. Lower DERL3 expression was more frequently detected in the advanced T-stage NPC than in early T-stage NPC. These results indicate that DERL3 repression by DNA methylation contributes to NPC tumour progression.

Insights into intricacies of the Latent Membrane Protein-1 (LMP-1) in EBV-associated cancers

Numerous lymphomas, carcinomas, and other disorders have been associated with Epstein-Barr Virus (EBV) infection. EBV's carcinogenic potential can be correlated to latent membrane protein 1 (LMP1), which is essential for fibroblast and primary lymphocyte transformation. LMP1, a transmembrane protein with constitutive activity, belongs to the tumour necrosis factor receptor (TNFR) superfamily. LMP1 performs number of role in the life cycle of EBV and the pathogenesis by interfering with, reprogramming, and influencing a vast range of host cellular activities and functions that are getting well-known but still poorly understood. LMP1, pleiotropically perturbs, reprograms and balances a wide range of various processes of cell such as extracellular vesicles, epigenetics, ubiquitin machinery, metabolism, cell proliferation and survival, and also promotes oncogenic transformation, angiogenesis, anchorage-independent cell growth, metastasis and invasion, tumour microenvironment. By the help of various experiments, it is proven that EBV-encoded LMP1 activates multiple cell signalling pathways which affect antigen presentation, cell-cell interactions, chemokine and cytokine production. Therefore, it is assumed that LMP1 may perform majorly in EBV associated malignancies. For the development of novel techniques toward targeted therapeutic applications, it is essential to have a complete understanding of the LMP1 signalling landscape in order to identify potential targets. The focus of this review is on LMP1-interacting proteins and related signalling processes. We further discuss tactics for using the LMP1 protein as a potential therapeutic for cancers caused by the EBV.

Epstein-Barr viral product-containing exosomes promote fibrosis and nasopharyngeal carcinoma progression through activation of YAP1/FAPα signaling in fibroblasts

Background

The progression of nasopharyngeal carcinoma (NPC) is profoundly affected by Epstein-Barr virus (EBV) infection. However, the role of EBV in the intercommunication between NPC and surrounding stromal cells has yet to be explored.

Methods

NPC biopsies were obtained for immunohistochemical (IHC) analyses. Clinical correlations between the expression of active YAP1/FAPα and the fibrotic response and between YAP1/FAPα and the density of cytotoxic CD8a+ T lymphocytes were determined. Survival times based on IHC scores were compared between groups using Kaplan-Meier survival and log-rank tests. Independent prognostic factors for metastasis/recurrence-free survival and overall survival were identified using univariate and multivariate Cox regression models. Fibroblasts were isolated from human nasopharyngeal biopsies. Exosomes were purified from culture supernatants of EBV+-positive NPC cells. The effects of EBV product-containing exosomes on fibroblast activation, fibrotic response, tumor growth, immune response, and correlations between the expression of featured genes were investigated using gel contraction assays, ELISAs, EdU incorporation assays, real-time impedance assays, RNA sequencing, immunostaining, 3D cancer spheroid coculture systems, and an NPC xenograft model.

Results

NPC patients who developed metastasis had significantly higher levels of active YAP1 and FAPα in their tumor stroma, which was further correlated with tumor fibrosis and poorer metastasis-free survival. Exosomes released from EBV+-NPC cells contained abundant FAPα protein and EBV-encoded latent membrane protein 1. Viral product-containing exosomes markedly enhanced the fibrotic response and tumor growth in a mouse xenograft model. IHC analyses of human NPC and NPC xenografts revealed positive correlations between levels of active YAP1 and FAPα, YAP1 and the fibrotic response, and FAPα and the fibrotic response. Mechanistic studies showed that treatment of fibroblasts with viral product-containing exosomes promoted the characteristics of cancer-associated fibroblasts by stimulating YAP1 signaling and the production of the immunosuppressive cytokines IL8, CCL2, and IL6. Inhibition of YAP1 activation markedly reversed these exosome-mediated protumoral effects, resulting in reduced contractility, inactivation of YAP1 signaling, and decreased production of immunosuppressive cytokines in fibroblasts. Furthermore, fibroblasts stimulated with these viral product-containing exosomes promoted NPC resistance to T cell-mediated cytotoxicity within tumor spheroids. In NPC tissues, a significant negative correlation was found between YAP1/FAPα and the density of CD8a+ T lymphocytes with a granzyme B signature.

Conclusion

EBV orchestrates interactions with the host and surrounding stroma by stimulating the functions of YAP1 and FAPα in fibroblasts through exosome cargos to create a more immunosuppressive, proinvasive microenvironment.

EBV genome variations enhance clinicopathological features of nasopharyngeal carcinoma in a non-endemic region

Nasopharyngeal carcinoma (NPC) is caused by infection with Epstein–Barr virus (EBV) and endemic in certain geographic regions. EBV lytic gene, BALF2, closely associates with viral reactivation and BALF2 gene variation, the H‐H‐H strain, causes NPC in endemic region, southern China. Here, we investigate whether such EBV variations also affect NPC in a non‐endemic region, Japan. Viral genome sequencing with 47 EBV isolates of Japanese NPC were performed and compared with those of other EBV‐associated diseases from Japan or NPC in Southern China. EBV genomes of Japanese NPC are different from those of other diseases in Japan or endemic NPC; Japanese NPC was not affected by the endemic strain (the BALF2 H‐H‐H) but frequently carried the type 2 EBV or the strain with intermediate risk of endemic NPC (the BALF2 H‐H‐L). Seven single nucleotide variations were specifically associated with Japanese NPC, of which six were present in both type 1 and 2 EBV genomes, suggesting the contribution of the type 2 EBV‐derived haplotype. This observation was supported by a higher viral titer and stronger viral reactivation in NPC with either type 2 or H‐H‐L strains. Our results highlight the importance of viral strains and viral reactivation in the pathogenesis of non‐endemic NPC.

Nasopharyngeal Carcinoma and Its Microenvironment: Past, Current, and Future Perspectives

Nasopharyngeal carcinoma (NPC) is an epithelial malignancy that raises public health concerns in endemic countries. Despite breakthroughs in therapeutic strategies, late diagnosis and drug resistance often lead to unsatisfactory clinical outcomes in NPC patients. The tumor microenvironment (TME) is a complex niche consisting of tumor-associated cells, such as fibroblasts, endothelial cells, leukocytes, that influences tumor initiation, progression, invasion, and metastasis. Cells in the TME communicate through various mechanisms, of note, exosomes, ligand-receptor interactions, cytokines and chemokines are active players in the construction of TME, characterized by an abundance of immune infiltrates with suppressed immune activities. The NPC microenvironment serves as a target-rich niche for the discovery of potential promising predictive or diagnostic biomarkers and the development of therapeutic strategies. Thus, huge efforts have been made to exploit the role of the NPC microenvironment. The whole picture of the NPC microenvironment remains to be portrayed to understand the mechanisms underlying tumor biology and implement research into clinical practice. The current review discusses the recent insights into the role of TME in the development and progression of NPC which results in different clinical outcomes of patients. Clinical interventions with the use of TME components as potential biomarkers or therapeutic targets, their challenges, and future perspectives will be introduced. This review anticipates to provide insights to the researchers for future preclinical, translational and clinical research on the NPC microenvironment.

New Look of EBV LMP1 Signaling Landscape

Simple Summary

Epstein-Barr Virus (EBV) infection is associated with various lymphomas and carcinomas as well as other diseases in humans. The transmembrane protein LMP1 plays versatile roles in EBV life cycle and pathogenesis, by perturbing, reprograming, and regulating a large range of host cellular mechanisms and functions, which have been increasingly disclosed but not fully understood so far. We summarize recent research progress on LMP1 signaling, including the novel components LIMD1, p62, and LUBAC in LMP1 signalosome and LMP1 novel functions, such as its induction of p62-mediated selective autophagy, regulation of metabolism, induction of extracellular vehicles, and activation of NRF2-mediated antioxidative defense. A comprehensive understanding of LMP1 signal transduction and functions may allow us to leverage these LMP1-regulated cellular mechanisms for clinical purposes.

Abstract

The Epstein–Barr Virus (EBV) principal oncoprotein Latent Membrane Protein 1 (LMP1) is a member of the Tumor Necrosis Factor Receptor (TNFR) superfamily with constitutive activity. LMP1 shares many features with Pathogen Recognition Receptors (PRRs), including the use of TRAFs, adaptors, and kinase cascades, for signal transduction leading to the activation of NFκB, AP1, and Akt, as well as a subset of IRFs and likely the master antioxidative transcription factor NRF2, which we have gradually added to the list. In recent years, we have discovered the Linear UBiquitin Assembly Complex (LUBAC), the adaptor protein LIMD1, and the ubiquitin sensor and signaling hub p62, as novel components of LMP1 signalosome. Functionally, LMP1 is a pleiotropic factor that reprograms, balances, and perturbs a large spectrum of cellular mechanisms, including the ubiquitin machinery, metabolism, epigenetics, DNA damage response, extracellular vehicles, immune defenses, and telomere elongation, to promote oncogenic transformation, cell proliferation and survival, anchorage-independent cell growth, angiogenesis, and metastasis and invasion, as well as the development of the tumor microenvironment. We have recently shown that LMP1 induces p62-mediated selective autophagy in EBV latency, at least by contributing to the induction of p62 expression, and Reactive Oxygen Species (ROS) production. We have also been collecting evidence supporting the hypothesis that LMP1 activates the Keap1-NRF2 pathway, which serves as the key antioxidative defense mechanism. Last but not least, our preliminary data shows that LMP1 is associated with the deregulation of cGAS-STING DNA sensing pathway in EBV latency. A comprehensive understanding of the LMP1 signaling landscape is essential for identifying potential targets for the development of novel strategies towards targeted therapeutic applications.

Genomic Landscape of Head and Neck Squamous Cell Carcinoma Across Different Anatomic Sites in Chinese Population

Background

The characteristics of head and neck squamous cell carcinoma (HNSCC) across different anatomic sites in the Chinese population have not been studied. To determine the genomic abnormalities underlying HNSCC across different anatomic sites, the alterations of selected cancer-related genes were evaluated.

Methods

Genomic DNA samples obtained from formalin-fixed, paraffin-embedded tissues were analyzed using targeted sequencing in a panel of 383 cancer-related genes to determine the genomic alterations.

Results

A total of 317 formalin-fixed, paraffin-embedded HNSCC specimens were collected, and a total of 2,156 protein-coding mutations, including 1,864 single nucleotide variants and 292 insertions and deletions, were identified across more than six different anatomic sites. Mutation loads were distinct across the anatomic sites. Larynx carcinoma was found with the highest mutation loads, whereas nasopharynx carcinoma showed the lowest mutation loads. A total of 1,110 gains and 775 losses were identified in the 317 specimens. Patients who had at least one clinically actionable alteration (levels 1–4 in OncoKB) were identified. One patient had an actionable alteration with level 1 evidence in OncoKB, TEX10-NTRK2 fusion, who may benefit from larotrectinib or entrectinib treatment.

Conclusion

The genomic profiling of HNSCC using targeted sequencing can identify rational therapeutic candidate genes suitable for the treatment of the HNSCCs.

Exosomes-carrying Epstein-Barr virus-encoded small RNA-1 induces indoleamine 2, 3-dioxygenase expression in tumor-infiltrating macrophages of oral squamous-cell carcinomas and suppresses T-cell activity by activating RIG-I/IL-6/TNF-α pathway

OBJECTIVES

Although exosomes carrying Epstein-Barr virus-encoded small RNA-1 (EBER-1) are involved in the immunosuppressive tumor microenvironments of EBV-associated head and neck carcinomas, the effects of EBER-1-associated exosomes on tumor-infiltrating macrophages are poorly understood.

MATERIALS AND METHODS

The association between EBV infection and expression of indoleamine 2,3-dioxygenase (IDO) was assessed in 165 paraffin-embedded oral squamous cell carcinoma (OSCC) tissue samples. Using in vitro techniques, we investigated whether stimulation of the RIG-I/IL-6/TNF-α pathway by exosomes carrying EBER-1 is critical for IDO induction in macrophages. We performed a thymidine incorporation and a cell cytolytic assay to test for up-regulated IDO in macrophages that can block the proliferation and function of effector T cells.

RESULTS

Some infiltrated macrophages expressed levels of IDO higher than OSCC cells which was significantly associated with presence of EBV. The production of IDO, tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in human monocyte-derived macrophages (MDMs) was induced by EBV-associated exosomes in vitro. Mechanistically, the retinoic acid-inducible gene I (RIG-I) pathway in MDMs was stimulated by EBV-encoded small RNA-1 (EBER-1) whereas the inhibition of these pathways by BX-795 almost abolished the production of these two cytokines and IDO induction. Also, the EBER-1-activated IDO in MDMs suppressed the proliferation of T lymphocytes and diminished the cytolytic activity of CD8+ T cells.

CONCLUSION

Exosomes carrying EBER-1 could induce IDO expression in MDMs, considerably aided by an IL-6 and TNF-α-dependent mechanism via the RIG-I signaling pathway, which might create an immunosuppressive microenvironment affecting T-cell immune responses.

Viral Manipulation of the Host Epigenome as a Driver of Virus-Induced Oncogenesis

Tumorigenesis due to viral infection accounts for a high fraction of the total global cancer burden (15–20%) of all human cancers. A comprehensive understanding of the mechanisms by which viral infection leads to tumor development is extremely important. One of the main mechanisms by which viruses induce host cell proliferation programs is through controlling the host’s epigenetic machinery. In this review, we dissect the epigenetic pathways through which oncogenic viruses can integrate their genome into host cell chromosomes and lead to tumor progression. In addition, we highlight the potential use of drugs based on histone modifiers in reducing the global impact of cancer development due to viral infection.

Epstein-Barr Virus LMP1 Induces Soluble PD-L1 in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is an Epstein–Barr virus (EBV)-associated malignancy. The principal oncogene of EBV, latent membrane protein 1 (LMP1), induces the expression of programmed death-ligand 1 (PD-L1), which is an immunosuppressive transmembrane protein and a promising therapeutic target for various malignancies. Recent studies have revealed an association between the level of soluble PD-L1 (sPD-L1) and disease progression. However, the role of sPD-L1 in NPC or its relevance to LMP1 has not been elucidated. This study aimed to examine whether LMP1 induces sPD-L1 in vitro and analyze the clinical relevance of LMP1, PD-L1, and sPD-L1 in NPC patients. Analysis of nasopharyngeal cell lines revealed that LMP1 induces both cellular PD-L1 and sPD-L1. Analysis of biopsy specimens from 32 NPC patients revealed that LMP1 expression was significantly correlated with PD-L1 expression. Finally, the serum sPD-L1 level in NPC patients was higher than that in the controls. Moreover, the sPD-L1 level in the advanced stage was higher than that in the early stage. However, LMP1 expression, PD-L1 expression, and sPD-L1 levels were not associated with prognosis. These results suggest that LMP1 induces both sPD-L1 and PD-L1, which are associated with NPC progression.

Epstein-Barr virus LMP1 manipulates the content and functions of extracellular vesicles to enhance metastatic potential of recipient cells

Extracellular vesicles (EV) mediate intercellular communication events and alterations in normal vesicle content contribute to function and disease initiation or progression. The ability to package a variety of cargo and transmit molecular information between cells renders EVs important mediators of cell-to-cell crosstalk. Latent membrane protein 1 (LMP1) is a chief viral oncoprotein expressed in most Epstein-Barr virus (EBV)-associated cancers and is released from cells at high levels in EVs. LMP1 containing EVs have been demonstrated to promote cell growth, migration, differentiation, and regulate immune cell function. Despite these significant changes in recipient cells induced by LMP1 modified EVs, the mechanism how this viral oncogene modulates the recipient cells towards these phenotypes is not well understood. We hypothesize that LMP1 alters EV content and following uptake of the LMP1-modified EVs by the recipient cells results in the activation of cell signaling pathways and increased gene expression which modulates the biological properties of recipient cell towards a new phenotype. Our results show that LMP1 expression alters the EV protein and microRNA content packaged into EVs. The LMP1-modified EVs also enhance recipient cell adhesion, proliferation, migration, invasion concomitant with the activation of ERK, AKT, and NF-κB signaling pathways. The LMP1 containing EVs induced transcriptome reprogramming in the recipient cells by altering gene expression of different targets including cadherins, matrix metalloproteinases 9 (MMP9), MMP2 and integrin-α5 which contribute to extracellular matrix (ECM) remodeling. Altogether, our data demonstrate the mechanism in which LMP1-modified EVs reshape the tumor microenvironment by increasing gene expression of ECM interaction proteins.

EBV-EBNA1 constructs an immunosuppressive microenvironment for nasopharyngeal carcinoma by promoting the chemoattraction of Treg cells

Background

Nasopharyngeal carcinoma (NPC) is primarily caused by the Epstein-Barr virus (EBV) infection in NPC endemic areas. EBNA1 is an EBV-encoded nuclear antigen, which plays a critical role in the maintenance and replication of EBV genome. However, the mechanisms of EBNA1-promoted NPC immune escape are unknown. Regulatory T (Treg) cells are among the key regulators in restraining antitumor responses. However, the mechanisms of accumulation of Treg cells in NPC have not been defined. This study attempted to identify the detailed mechanisms of EBNA1 functions as a tumor accelerator to promote NPC immune escape by enhancing chemoattraction of Treg cells.

Methods

mRNA profiles were determined by next-generation sequencing in NPC cells. In vitro and in vivo assays were performed to analyze the role of EBNA1 in regulation of recruitment of Treg cells. Colocation and coimmunoprecipitation analyzes were used to identify the SMAD3/c-JUN complex. Chromatin immunoprecipitation assay and dual luciferase reporter assays were designed to demonstrate c-JUN binding to miR-200a promoter and miR-200a targeting to CXCL12 3’Untranslated Regions. The hepatocellular carcinoma models were designed to demonstrate universality of the CXCL12-CXCR4-Treg axis in promoting immune evasion of various tumors.

Result

A novel molecular mechanism was identified that involves EBV-EBNA1-stimulated chemotactic migration of Treg cells toward NPC microenvironment by upregulation of the transforming growth factor-β1 (TGFβ1)-SMAD3-PI3K-AKT-c-JUN-CXCL12-CXCR4 axis and downregulation of miR-200a. EBV-EBNA1 promotes the chemoattraction of Treg cells by governing the protein–protein interactions of the SMAD3/c-JUN complex in a TGFβ1-dependent manner in vitro and in vivo. TGFβ1 suppresses miR-200a by enhancing the SMAD3/c-JUN complex. miR-200a negatively regulates the CXCL12 chemokine by direct targeting of the CXCL12 3’UTR region. However, CXCL12 acts as the target gene of miR-200a and as an inhibitor of miR-200a transcription, and inhibition of miR-200a by CXCL12 is mediated by c-JUN, which directly binds to the miR-200a promoter and forms a c-JUN-miR-200a-CXCL12-c-JUN feedback loop. In addition, enhanced CXCL12 efficiently attracts CXCR4-positive Treg cells to remodel an immunosuppressive microenvironment.

Conclusions

EBV-EBNA1 promotes chemotactic migration of Treg cells via the TGFβ1-SMAD3-PI3K-AKT-c-JUN-miR-200a-CXCL12-CXCR4 axis in the NPC microenvironment. These results suggest that EBV-EBNA1 may serve as a potential therapeutic target to reshape the NPC microenvironment.

EBV-LMP1 induces APOBEC3s and mitochondrial DNA hypermutation in nasopharyngeal cancer

An Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) is a principal oncogene that plays a pivotal role in EBV-associated malignant tumors including nasopharyngeal cancer (NPC). Recent genomic landscape studies revealed that NPC also contained many genomic mutations, suggesting the role of LMP1 as a driver gene for the induction of these genomic mutations. Nonetheless, its exact mechanism has not been investigated. In this study, we report that LMP1 alters the expression profile of APOBEC3s(A3s), host deaminases that introduce consecutive C-to-U mutations (hypermutation). In vitro, LMP1 induces APOBEC3B (A3B) and 3F(A3F), in a nasopharyngeal cell line, AdAH. Overexpression of LMP1, A3B, or A3F induces mtDNA hypermutation, which is also detectable from NPC specimens. Expression of LMP1 and A3B in NPC was correlated with neck metastasis. These results provide evidence as to which LMP1 induces A3s and mtDNA hypermutation, and how LMP1 facilitates metastasis is also discussed.

Exosomal Delivery of AntagomiRs Targeting Viral and Cellular MicroRNAs Synergistically Inhibits Cancer Angiogenesis

Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated cancer characterized by a high degree of recurrence, angiogenesis, and metastasis. The importance of alternative pro-angiogenesis pathways including viral factors has emerged after decades of directly targeting various signaling components. Using NPC as a model, we identified an essential oncogenic pathway underlying angiogenesis regulation that involves the inhibition of a tumor suppressor, Spry3, and its downstream targets by EBV-miR-BART10-5p (BART10-5p) and hsa-miR-18a (miR-18a). Overexpression of EBV-miR-BART10-5p and hsa-miR-18a strongly promotes angiogenesis in vitro and in vivo by regulating the expression of VEGF and HIF1-α in a Spry3-dependent manner. In vitro or in vivo treatment with iRGD-tagged exosomes containing antagomiR-BART10-5p and antagomiR-18a preferentially suppressed the angiogenesis and growth of NPC. Our findings first highlight the role of EBV-miR-BART10-5p and oncogenic hsa-miR-18a in NPC angiogenesis and also shed new insights into the clinical intervention and therapeutic strategies for nasopharyngeal carcinoma and other virus-associated tumors.

Novel Therapies Boosting T Cell Immunity in Epstein Barr Virus-Associated Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant tumour of the head and neck affecting localised regions of the world, with the highest rates described in Southeast Asia, Northern Africa, and Greenland. Its high morbidity rate is linked to both late-stage diagnosis and unresponsiveness to conventional anti-cancer treatments. Multiple aetiological factors have been described including environmental factors, genetics, and viral factors (Epstein Barr Virus, EBV), making NPC treatment that much more complex. The most common forms of NPCs are those that originate from the epithelial tissue lining the nasopharynx and are often linked to EBV infection. Indeed, they represent 75–95% of NPCs in the low-risk populations and almost 100% of NPCs in high-risk populations. Although conventional surgery has been improved with nasopharyngectomy’s being carried out using more sophisticated surgical equipment for better tumour resection, recent findings in the tumour microenvironment have led to novel treatment options including immunotherapies and photodynamic therapy, able to target the tumour and improve the immune system. This review provides an update on the disease’s aetiology and the future of NPC treatments with a focus on therapies activating T cell immunity.

CD47 Overexpression Is Associated with Epstein-Barr Virus Infection and Poor Prognosis in Patients with Nasopharyngeal Carcinoma

Purpose

Little is known about the clinical significance of CD47 expression and its association with Epstein–Barr virus (EBV) infection in patients with nasopharyngeal carcinoma (NPC). The aim of this study was to clarify the prognostic value and role of CD47 in EBV-associated NPC.

Materials and Methods

Sixty-six cases of non-metastatic NPC were retrospectively reviewed. Tissues were collected for immunohistochemical staining of CD47 and the EBV-encoded oncoprotein latent membrane protein 1 (LMP1). Western blotting and quantitative real-time PCR were performed to determine the CD47 and LMP1 levels in common human NPC cell lines. Additionally, CD47 and LMP1 expression in a constructed EBV-positive human NPC cell (CNE-2-EBV+) and a stable cell line transfected with LMP1 plasmid (CNE-2-LMP1) was assessed. Next, we used Western blotting to assess the decrease in CD47 expression on CNE-2-LMP1 cells after transfecting them with small interfering RNA (siRNA)-targeting LMP1.

Results

In NPC patients, CD47 overexpression was significantly associated with disease recurrence (P=0.010), leading to poorer disease-free survival (DFS; P=0.002) and overall survival (P=0.021). Multivariate Cox proportional hazards models demonstrated that CD47 (HR=5.452, P=0.016) was an independent prognostic factor of DFS. Moreover, CD47 expression was associated with plasma EBV-DNA copy number and LMP1 tissue expression. Among the human NPC cell lines, CD47 and LMP1 expression was notably higher in the EBV-positive C666-1 cell line than in the EBV-negative cell lines. Furthermore, EBV infection upregulated CD47 expression via LMP1-mediated pathways in human NPC cells.

Conclusion

This study indicated that CD47 is related to EBV infection in NPC patients, and it is a feasible biomarker.

EB virus promotes metastatic potential by boosting STIM1-dependent Ca2+ signaling in nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC) is a unique head and neck malignancy with highly metastatic cell-biological characteristics, for which latent EBV-infection is responsible. Our earlier studies showed that EGF-stimulated Ca²⁺ signaling via store-operated Ca²⁺ entry (SOCE) was amplified in NPC cells expressing EBV-encoded LMP1, thus contributing to EBV-enhanced metastatic capacities. However, the pathway through which EBV modulates cytosolic Ca²⁺ signaling still remains unclear. Here, we demonstrated that EBV-infection amplified EGF-stimulated Ca²⁺ responses through the promotion of intracellular aggregation of STIM1, which serves as a Ca²⁺ sensor to activate SOCE. Blockage of EBV-remodeled Ca²⁺ signaling by STIM1-silencing inhibited cell migration by interrupting epithelial-mesenchymal transition (EMT) in vitro, and suppressed tumor dissemination in zebrafish and lymph node metastasis in mice. In addition, STIM1 expression was upregulated in primary NPC tissues compared with normal nasopharyngeal epithelium and stronger among the patients with advanced lymph node metastatic disease (N_2-3 stage). Our findings thus indicate that EBV promotes metastatic potential by enhancing STIM1-dependent Ca²⁺ signaling that manipulates EMT in NPC cells. EBV-modulated Ca²⁺ signaling could serve as a candidate anti-metastatic target for NPC treatment.

Mesenchymal stem/stromal cells-derived IL-6 promotes nasopharyngeal carcinoma growth and resistance to cisplatin via upregulating CD73 expression

Previous studies have implicated the important role of mesenchymal stem/stromal cells (MSCs) within tumor microenvironment (TME) in the pathogenesis and progression of nasopharyngeal carcinoma (NPC), but the potential mechanisms are still unclear. Herein, we showed that an elevated IL-6 level was positively correlated with elevated expression of CD73 in TME of NPC. NPC specimens with an IL-6^highCD73^high phenotype showed higher expression levels of gp80, gp130, p-STAT3, MMP-9 and α-SMA, and clinically, a poorer prognosis than those with an IL-6^lowCD73^low phenotype. We found that stimulation with conditioned media derived from IL-6 gene knocked out MSC (MSC^IL6KO-CM) down-regulated the expression of CD73, IL-6, gp80, p-STAT3, and proliferative cell nuclear antigen (PCNA) in CNE-2 NPC cells. Meanwhile, NPC cells co-cultured with MSC^IL6KO-CM were more sensitive to cisplatin than those co-cultured with MSC-CM. Additionally, MSC-derived IL-6 transcriptionally upregulated CD73 expression via activating STAT3 signaling pathway in NPC cells. In summary, our findings suggest that MSCs promote NPC progression and chemoresistance by upregulation of CD73 expression via activating STAT3 signaling pathway.

LMP1 Up-regulates Calreticulin to Induce Epithelial-mesenchymal Transition via TGF-β/Smad3/NRP1 Pathway in Nasopharyngeal Carcinoma Cells

Background: Latent membrane protein 1 (LMP1) is known as an oncogenic protein encoded by the EBV genome. The purpose of this study was to investigate the mechanism of LMP1-induced cell epithelial-mesenchymal transition (EMT).

Methods: The NP69 cell line of nasopharyngeal epithelial cells with high expression of LMP1 was established to observe the effect of high expression of LMP1 on cell growth, proliferation, cycle, apoptosis, migration and invasion. We used proteomics to screen and identify differentially expressed proteins related to LMP1-mediated epithelial cell transformation. Then, we analyzed the expression and significance of differentially expressed calreticulin (CRT) in nasopharyngeal carcinoma (NPC), and observed the effect of CRT expression on EMT in CNE2 cells of NPC. Finally, the expression of neuropilin-1 (NRP1), which is a protein downstream of the EMT-related signaling pathway TGF-β (transforming growth factor β), was detected.

Results: LMP1 promoted NP69 cells proliferation, inhibited apoptosis and induced EMT. We identified 22 differentially expressed proteins associated with LMP1-induced EMT. Among them, CRT expression level was significantly increased in NPC compared with adjacent tissues, and was interrelated with TNM staging and lymph node metastasis of NPC. After knockdown of CRT expression, the phenomenon of cell EMT was reduced and the ability of cell migration and invasion was weakened. CRT regulated NRP1 expression by affecting SMAD3 phosphorylation.

Conclusion: LMP1 induced cell EMT via TGF-β/Smad3/NRP1 pathway, which promoted migration and invasion of NPC cells.

CUL4A expression is associated with tumor stage and prognosis in nasopharyngeal carcinoma

Cullin 4A (CUL4A) is a protein of E3 ubiquitin ligase with many cellular processes. CUL4A could regulate cell cycle, development, apoptosis, and genome instability. This study aimed to analyze the expression of CUL4A in nasopharyngeal carcinoma (NPC) tissues and the associations of CUL4A expression with prognostic significance. A total of 115 NPC patients were collected to assess the protein expression of CUL4A by immunohistochemistry, so as to analyze the relationships between CUL4A expression and clinicopathological and prognostic parameters. All patients were followed-up until death or 5 years. The results showed that high expression of CUL4A was significantly associated with larger primary tumor size (P = .026), higher nodal status (P = .013), more distant metastasis (P = .020), and higher TNM stage (P = .005). Kaplan-Meier curves showed that patients with higher CUL4A expression had significantly shorter overall survival (OS) and progression-free survival (PFS) (both P < .001). In multivariate Cox analysis, CUL4A is an independent prognostic factor for OS (P = .016; hazard ratio [HR] = 2.770, 95% CI: 1.208-6.351) and PFS (P = .022; HR = 2.311, 95% CI: 1.126-4.743). In conclusion, high expression of CUL4A was associated with advanced disease status of NPC, and might serve as an independent prognostic factor.

Targeting Immune-Related Biological Processes in Solid Tumors: We do Need Biomarkers

Immunotherapy has become the standard-of-care in many solid tumors. Despite the significant recent achievements in the diagnosis and treatment of cancer, several issues related to patients’ selection for immunotherapy remain unsolved. Multiple lines of evidence suggest that, in this setting, the vision of a single biomarker is somewhat naïve and imprecise, given that immunotherapy does not follow the rules that we have experienced in the past for targeted therapies. On the other hand, additional immune-related biomarkers that are reliable in real-life clinical practice remain to be identified. Recently, the immune-checkpoint blockade has been approved in the US irrespective of the tumor site of origin. Further histology-agnostic approvals, coupled with with tumor-specific companion diagnostics and guidelines, are expected in this field. In addition, immune-related biomarkers can also have a significant prognostic value. In this review, we provide an overview of the role of these biomarkers and their characterization in the management of lung cancer, melanoma, colorectal cancer, gastric cancer, head and neck cancer, renal cell carcinoma, urothelial cancers, and breast cancer.

Expression and clinical significance of PD-L1 and BRAF expression in nasopharyngeal carcinoma

Background

The prognostic value of programmed death-ligand 1 (PD-L1) and BRAF expression in nasopharyngeal carcinoma (NPC) is not well-defined. In this study we investigated alterations in PD-L1, BRAF and EGFR by using immunohistochemistry analysis in a cohort of consecutively enrolled NPC patients.

Methods

A retrospective review of 154 NPC patients form our previous study (BMC Cancer. 2013; 13:226) were conducted. Survival and prognostic impacts were analyzed based on PD-L1, BRAF and EGFR expression levels.

Results

One hundred fifty four patients were included in this study. PD-L1 expression was detected in 87.7% of patients; 14.3% had 1–5% PD-L1 expression, 47.4% had 5–49% expression while 26% had ≥50% expression Higher PD-L1 expression was significantly associated with shorter PFS and OS. The median PFS was 25 months (95% CI 15.7–34.3 months) and OS was 35 months (95% CI 22.60–47.4 months) for patients with PD-L1 expression ≥50%; both median PFS and OS were not yet reached for patients with PD-L1 expression < 50%. PFS was significantly higher in BRAF mutation positive patients (5-year PFS: 55.1% vs. 30.8%, P = 0.044).

Conclusion

Tumor PD-L1 expression and BRAF mutation are associated with poor outcomes in patients with NPC. This study was retrospectively registered in ClinicalTrials.gov (NCT03989297) on 2019-6-18.

Plasma levels of soluble programmed death ligand 1 (sPD-L1) in WHO II/III nasopharyngeal carcinoma (NPC): A preliminary study

Plasma levels of soluble PD-L1 (sPD-L1) have been reported to be an independent prognostic factor in many malignant tumors. The expression of sPD-L1 in nasopharyngeal carcinoma (NPC) has not been reported. The purpose of this study was to evaluate the expression of sPD-L1 and analyze its correlation with clinical characteristics in patients with NPC.Thirty-five patients with stage I-IVa NPC were included. Plasma samples were obtained pretreatment. The sPD-L1 concentrations were measured by enzyme-linked immunosorbent assay (ELISA). The correlations of sPD-L1 expression with clinical parameters and laboratory data were analyzed.sPD-L1 was detected in 35 plasma samples, the mean sPD-L1 concentration was 45.47 pg/ml. sPD-L1 was significantly higher in stage III-IVa (50.76 ± 28.15 pg/ml) compared to stage I-II (19.87 ± 11.38 pg/ml) (t = 2.618, P = .013). sPD-L1 was also higher in stage N2-3 (52.03 ± 28.98 pg/ml) than that in N0-1 (32.88 ± 23.75 pg/ml) (t = 2.096, P = .046). Univariate analysis identified that sPD-L1 level positively correlated with clinical stage (r = 0.495, P = .002) and N stage (r = 0.34, P = .046). Multivariate analysis showed the clinical stage was an independent factor affecting sPD-L1 expression.This is the first report to detect sPD-L1 in NPC. The study indicated sPD-L1 is quantifiable, convenient and easy to obtain. sPD-L1 may serve as a useful biomarker for evaluating tumor progression and therapeutic efficacy of NPC.

Inhibition of UCH-L1 Deubiquitinating Activity with Two Forms of LDN-57444 Has Anti-Invasive Effects in Metastatic Carcinoma Cells

Normally ubiquitin C-terminal hydrolase L1 (UCH-L1) is expressed in the central nervous and reproductive systems of adults, but its de novo expression has been detected in many human cancers. There is a growing body of evidence that UCH-L1 de-ubiquitinating (DUB) activity plays a major pro-metastatic role in certain carcinomas. Here we tested anti-metastatic effects of the small-molecule inhibitor of UCH-L1 DUB activity, LDN-57444, in cell lines from advanced oral squamous cell carcinoma (OSCC) as well as invasive nasopharyngeal (NP) cell lines expressing the major pro-metastatic gene product of Epstein–Barr virus (EBV) tumor virus, LMP1. To overcome the limited aqueous solubility of LDN-57444 we developed a nanoparticle formulation of LDN-57444 by incorporation of the compound in polyoxazoline micellear nanoparticles (LDN-POx). LDN-POx nanoparticles were equal in effects as the native compound in vitro. Our results demonstrate that inhibition of UCH-L1 DUB activity with LDN or LDN-POx inhibits secretion of exosomes and reduces levels of the pro-metastatic factor in exosomal fractions. Both forms of UCH-L1 DUB inhibitor suppress motility of metastatic squamous carcinoma cells as well as nasopharyngeal cells expressing EBV pro-metastatic Latent membrane protein 1 (LMP1) in physiological assays. Moreover, treatment with LDN and LDN-POx resulted in reduced levels of pro-metastatic markers, a decrease of carcinoma cell adhesion, as well as inhibition of extra-cellular vesicle (ECV)-mediated transfer of viral invasive factor LMP1. We suggest that soluble inhibitors of UCH-L1 such as LDN-POx offer potential forms of treatment for invasive carcinomas including EBV-positive malignancies.

Tumor Microenvironment and Cell Fusion

Cell fusion is a highly regulated biological process that occurs under both physiological and pathological conditions. The cellular and extracellular environment is critical for the induction of the cell-cell fusion. Aberrant cell fusion is initiated during tumor progression. Tumor microenvironment is a complex dynamic system formed by the interaction between tumor cells and their surrounding cells. Cell-cell fusion mediates direct interaction between tumor cells and their surrounding cells and is associated with tumor initiation and progression. Various microenvironmental factors affect cell fusion in tumor microenvironment and generate hybrids that acquire genomes of both parental cells and exhibit novel characteristics, such as tumor stem cell-like properties, radioresistance, drug resistance, immune evasion, and enhanced migration and invasion abilities, which are closely related to the initiation, invasion, and metastasis of tumor. The phenotypic characteristics of hybrids are based on the phenotypes of parental cells, and the fusion of tumor cells with diverse types of microenvironmental fusogenic cells is concomitant with phenotypic heterogeneity. This review highlights the types of fusogenic cells in tumor microenvironment that can fuse with tumor cells and their specific significance and summarizes the various microenvironmental factors affecting tumor cell fusion. This review may be used as a reference to develop strategies for future research on tumor cell fusion and the exploration of cell fusion-based antitumor therapies.

Epstein-Barr virus-encoded LMP1 regulated Pim1 kinase expression promotes nasopharyngeal carcinoma cells proliferation

Background

Epstein–Barr virus-encoded LMP1 plays a critical role in the carcinogenesis of nasopharyngeal carcinoma (NPC), but the mechanism remains elusive. We aimed to analyze the expression and clinical pathological significance of provirus integration site for Moloney murine leukemia virus 1 (Pim1) in clinical NPC, and to elucidate the effect of LMP1 on Pim1 expression and its mechanism.

Methods

Immunohistochemical staining was used to detect the expression of Pim1 in clinical NPC tissues and control nasopharyngeal chronic inflammation (NPI) tissues, and the correlation between Pim1 and clinical parameters of NPC patients was analyzed. The LMP1 stable expression cell line CNE1-LMP1-OV was constructed through infecting the well-differentiated nasopharyngeal carcinoma cells CNE1 with LMP1 overexpressing lentivirus. Then the in vivo experiments were conducted.

Results

Among 89 NPC patients, 48 cases (53.93%) were positive for Pim1, while only one case was Pim1 positive in 15 NPI controls (6.67%). Pim1 expression was not correlated with gender, age, smoking status and clinical classification of NPC patients, but positively correlated with T, N and M classification. CNE1-LMP1-OV cell line was successfully established, which displayed a higher cell proliferation ability and Pim1 expression. NF-κB inhibitor PDTC, PKC inhibitor GF109203X and STAT3 inhibitor Stattic significantly attenuated LMP1-induced Pim1 expression, and while AP-1 inhibitor SR11302 showed no inhibitory effect. Interestingly, Pim1 inhibitor quercetagetin significantly inhibited the proliferation of CNE1-LMP1-OV cells.

Conclusion

LMP1 mediates Pim1 expression through NF-κB, PKC and STAT3 signaling, which promotes the proliferation of NPC cells and participate in the clinical progression of NPC.

Exosomes in virus-associated cancer

Exosomes are phospholipid bilayer membrane-enclosed vesicles in a size from 30 to 150 nm, carrying a variety of active components, such as proteins, mRNA and miRNAs, and are involved in intercellular communication. Exosomes are released by almost all living cells and detected in various biological fluids. Viruses especially oncogenic viruses have been reported to influence the formation of virus-associated cancer through reshaping the tumor microenvironment via exosomes. In this review, a role of exosomes released by oncogenic virus-infected cells in promoting or inhibiting cancer formation is outlined. Moreover, the prospects and challenges of exosome applications in cancer therapies are critically discussed.

Inhibition of CD9 expression reduces the metastatic capacity of human hepatocellular carcinoma cell line MHCC97-H

Metastasis is a characteristic of malignant tumors and may be a fatal clinical factor for many patients with cancer. Hepatocellular carcinoma (HCC) cells are highly metastatic; the mechanism of metastasis is complicated and may be influenced by a number of factors. Membrane proteins may block receptors or inhibit important enzymes, thus inhibiting tumor progression, and may be potential therapeutic targets for tumor prognosis and treatment. The present study aimed to use proteomics to analyze the dynamic changes of membrane proteins in HCC cells, to improve our understanding of membrane protein functions and to clarify the important components of the mechanisms of HCC metastasis. The present study used the highly metastatic MHCC97-H and the lowly metastatic MHCC97-L HCC cell lines, and the isobaric tags for relative and absolute quantitation (iTRAQ) approach was used for high-throughput screening of metastasis-related membrane proteins. A total of 22 membrane proteins were identified as differentially expressed between the MHCC97-H and MHCC97-L cell lines; these results were verified by reverse transcription-quantitative polymerase chain reaction and western blotting. A number of the identified proteins were revealed to be related to tumor metastasis, including the tetraspan in transmembrane protein CD9. CD9 was demonstrated to be highly expressed in MHCC97-H cells compared with MHCC97-L cells. The functional role of CD9 was characterized by inhibiting its expression using a small interfering RNAs, which demonstrated that reduced CD9 expression inhibited cell migration and metastasis, as determined by wound-healing and invasion assays. Results from the present study demonstrated that CD9 was highly expressed in the highly metastatic HCC cells and promoted HCC cell migration. This protein may be a novel target for regulating the invasive phenotype in HCC.

Modulation of the tumor microenvironment by Epstein-Barr virus latent membrane protein 1 in nasopharyngeal carcinoma

Latent membrane protein 1 (LMP1) is a primary oncogene encoded by the Epstein‐Barr virus, and various portions of LMP1 are detected in nasopharyngeal carcinoma (NPC) tumor cells. LMP1 has been extensively studied since the discovery of its transforming property in 1985. LMP1 promotes cancer cell growth during NPC development and facilitates the interaction of cancer cells with surrounding stromal cells for invasion, angiogenesis, and immune modulation. LMP1 is detected in 100% of pre‐invasive NPC tumors and in approximately 50% of advanced NPC tumors. Moreover, a small population of LMP1‐expressing cells in advanced NPC tumor tissue is proposed to orchestrate NPC tumor tissue maintenance and development through cancer stem cells and progenitor cells. Recent studies suggest that LMP1 activity shifts according to tumor development stage, but it still has a pivotal role during all stages of NPC development.