EBV-miR-BART7-3p Imposes Stemness in Nasopharyngeal Carcinoma Cells by Suppressing SMAD7

Tumor-Derived EBV-miR-BART2-5p Promotes Nasopharyngeal Carcinoma Metastasis by Inducing Premetastatic Endothelial Cell Pyroptosis

Extravasation is a key step in tumor metastasis. Epstein‒Barr virus plays a crucial role in nasopharyngeal carcinoma (NPC) metastasis. However, the functions and molecular mechanisms of Epstein‒Barr virus during tumor cell extravasation remain unclear. Here, we showed that the expression of pyroptosis-associated proteins is greater in the endothelial cells of metastatic NPC tissues than in those of nontumor tissues exosomes derived from NPC cells promoted endothelial cell pyroptosis, vascular permeability, and tumor cell extravasation. Moreover, we found that BART2-5p is abundant in serum exosomes from patients with NPC metastasis and in NPC cells and that it regulates endothelial cell pyroptosis in premetastatic organs via MRE11A. Exosomes containing a BART2-5p inhibitor and AAV-MRE11A attenuated endothelial cell pyroptosis and tumor metastasis. Moreover, in the endothelial cells of metastatic tissues from patients with NPC, the BART2-5p level was positively associated with pyroptosis-related protein expression. Collectively, our findings suggest that exosomal BART2-5p is involved in premetastatic niche formation, identifying secreted BART2-5p as a potential therapeutic target for NPC metastasis. Implications: The finding that secreted BART2-5p is involved in premetastatic niche formation may aid the development of a potential therapeutic target for NPC metastasis.

The 'Oma's of the Gammas-Cancerogenesis by γ-Herpesviruses

Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV), which are the only members of the gamma(γ) herpesviruses, are oncogenic viruses that significantly contribute to the development of various human cancers, such as Burkitt's lymphoma, nasopharyngeal carcinoma, Hodgkin's lymphoma, Kaposi's sarcoma, and primary effusion lymphoma. Oncogenesis triggered by γ-herpesviruses involves complex interactions between viral genetics, host cellular mechanisms, and immune evasion strategies. At the genetic level, crucial viral oncogenes participate in the disruption of cell signaling, leading to uncontrolled proliferation and inhibition of apoptosis. These viral proteins can modulate several cellular pathways, including the NF-κB and JAK/STAT pathways, which play essential roles in cell survival and inflammation. Epigenetic modifications further contribute to EBV- and KSHV-mediated cancerogenesis. Both EBV and KSHV manipulate host cell DNA methylation, histone modification, and chromatin remodeling, the interplay of which contribute to the elevation of oncogene expression and the silencing of the tumor suppressor genes. Immune factors also play a pivotal role in the development of cancer. The γ-herpesviruses have evolved intricate immune evasion strategies, including the manipulation of the major histocompatibility complex (MHC) and the release of cytokines, allowing infected cells to evade immune detection and destruction. In addition, a compromised immune system, such as in HIV/AIDS patients, significantly increases the risk of cancers associated with EBV and KSHV. This review aims to provide a comprehensive overview of the genetic, epigenetic, and immune mechanisms by which γ-herpesviruses drive cancerogenesis, highlighting key molecular pathways and potential therapeutic targets.

The role of c-Myc in Epstein-Barr virus-associated cancers: Mechanistic insights and therapeutic implications

c-Myc is an important proto-oncogene belonging to the MYC family. In normal conditions, c-Myc regulates different aspects of cellular function. However, its dysregulation can result in the development of cancer due to various mechanisms. Epstein-Barr virus is a ubiquitous viral pathogen that infects a huge proportion of the global population. This virus is linked to various cancers, such as different types of lymphoma, nasopharyngeal, and gastric cancers. It can manipulate host cells, and many cellular and viral genes are important in the Epstein-Barr virus carcinogenesis. This review explores the complex relationship between c-Myc and Epstein-Barr virus in the context of cancer development. Also, potential therapeutic strategies targeting c-Myc to treat EBV-related cancers are discussed.

War or peace: Viruses and metastasis

Metastasis, the dissemination of malignant cells from a primary tumor to secondary sites, poses a catastrophic burden to cancer treatment and is the predominant cause of mortality in cancer patients. Metastasis as one of the main aspects of cancer progression could be strongly under the influence of viral infections. In fact, viruses have been central to modern cancer research and are associated with a great number of cancer cases. Viral-encoded elements are involved in modulating essential pathways or specific targets that are implicated in different stages of metastasis. Considering the continuous emergence of new viruses and the establishment of their contribution to cancer progression, the warfare between viruses and cancer appears to be endless. Here we aimed to review the critical mechanism and pathways involved in cancer metastasis and the influence of viral machinery and various routes that viruses adopt to manipulate those pathways for their benefit.

LINC00313 suppresses autophagy and promotes stemness of nasopharyngeal carcinoma cells through PTBP1/STIM1 axis

BACKGROUND

Nasopharyngeal carcinoma (NPC) is a kind of malignant head and neck tumor with high mortality. lncRNAs are valuable diagnostic biomarkers and therapeutic targets for various tumors. This study investigated the effects and mechanism of LINC00313 in nasopharyngeal carcinoma.

METHODS

Cell Counting Kit-8 (CCK-8) and immunohistochemistry were used for assessing cell proliferation. The levels of autophagy-related proteins, and stem cell markers were detected. Immunofluorescence assay was used for LC3 detection. Methylated RNA Immunoprecipitation (meRIP) of LINC00313 in NPC cells was assessed. The localization of LINC00313 was verified by luorescence in situ hybridization (FIHS). The interaction between LINC00313 and the downstream targets were analyzed and confirmed by immunoprecipitation (RIP). Besides, the tumorigenesis roles of LINC00313 were confirmed in tumor growth mice model.

RESULTS

LINC00313 was increased in NPC tissues and cells. LINC00313 knockdown enhanced autophagy, and decreased stemness and cell viability of NPC cells through regulating STIM1. METTL3/IGF2BP1-mediated m6A modification promoted the stabilization and up-regulation of LINC00313. LINC00313 activated AKT/mTOR pathway in NPC cells through PTBP1/STIM1 axis. Moreover, LINC00313 promoted tumor growth and metastasis in xenograft model.

CONCLUSION

Upregulation of LINC00313 suppressed autophagy and promoted stemness of NPC cells through PTBP1/STIM1 axis.

Epstein-Barr Virus miR-BARTs 7 and 9 modulate viral cycle, cell proliferation, and proteomic profiles in Burkitt lymphoma

The Epstein-Barr Virus (EBV) encodes viral microRNAs (miRs) that have been implicated in the pathogenesis of nasopharyngeal and gastric carcinomas, yet their potential roles in lymphomas remain to be fully elucidated. This study evaluated the impact of CRISPR/Cas9-mediated knockdown of EBV miRs BART-7 and BART-9 in EBV-positive Burkitt lymphoma cells Akata. As anticipated, the Akata cells subjected to CRISPR/Cas9-mediated knockdown of either EBV BART-7 or BART-9 exhibited a significant reduction in the expression of these viral miRs compared to cells with wild-type (wt) EBV genomes. This outcome effectively validates the experimental model employed in this study. Knocking down either BART-7 or BART-9 resulted in a notable reduction in cell viability and proliferation rates, alongside an elevation in the expression of EBV lytic genes. Global proteomic analysis revealed that the knockdown of EBV BART-7 significantly decreased the expression of ubiquitin/proteasome proteins while concurrently increasing RNA binding proteins (RBPs). Conversely, BART-9 knockdown reduced proteins associated with oxidoreductase activity, particularly those involved in fatty acid metabolism. Our findings unveil previously undiscovered EBV miRs BARTs 7 and 9 roles in cellular pathways relevant to both viral biology and lymphomagenesis.

The promising role of miRNAs in radioresistance and chemoresistance of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant epithelial tumor that develops in the nasopharynx. It has a distinct ethnic and geographical distribution, and emerging evidence suggests that it is an ecological disease. Most patients respond well to radiation combined with chemotherapy as the primary treatment for NPC. However, some patients will eventually develop radio resistance and chemoresistance, resulting in recurrence and metastasis, which is a primary cause of poor prognosis. The processes underlying radio resistance and chemoresistance in NPC are complex and unknown. MicroRNAs (miRNAs) are endogenic non-coding RNA molecules. They play a role in a variety of cell functions as well as development of disease such as cancer. There has been considerable data demonstrating the existence of numerous aberrant miRNAs in cancer tissues, cells, and biofluids, which indicates the importance of studying the influence of miRNAs on NPC. Therefore, this review comprehensively analyzes the elaborate mechanisms of miRNAs affecting the radio resistance and chemoresistance of NPC. Multiple tumor-specific miRNAs can be employed as therapeutic and prognostic biological indicators.

Nasopharyngeal carcinoma: current views on the tumor microenvironment's impact on drug resistance and clinical outcomes

The incidence of nasopharyngeal carcinoma (NPC) exhibits significant variations across different ethnic groups and geographical regions, with Southeast Asia and North Africa being endemic areas. Of note, Epstein-Barr virus (EBV) infection is closely associated with almost all of the undifferentiated NPC cases. Over the past three decades, radiation therapy and chemotherapy have formed the cornerstone of NPC treatment. However, recent advancements in immunotherapy have introduced a range of promising approaches for managing NPC. In light of these developments, it has become evident that a deeper understanding of the tumor microenvironment (TME) is crucial. The TME serves a dual function, acting as a promoter of tumorigenesis while also orchestrating immunosuppression, thereby facilitating cancer progression and enabling immune evasion. Consequently, a comprehensive comprehension of the TME and its intricate involvement in the initiation, progression, and metastasis of NPC is imperative for the development of effective anticancer drugs. Moreover, given the complexity of TME and the inter-patient heterogeneity, personalized treatment should be designed to maximize therapeutic efficacy and circumvent drug resistance. This review aims to provide an in-depth exploration of the TME within the context of EBV-induced NPC, with a particular emphasis on its pivotal role in regulating intercellular communication and shaping treatment responses. Additionally, the review offers a concise summary of drug resistance mechanisms and potential strategies for their reversal, specifically in relation to chemoradiation therapy, targeted therapy, and immunotherapy. Furthermore, recent advances in clinical trials pertaining to NPC are also discussed.

Viral miRNA regulation of host gene expression

Viruses have evolved a multitude of mechanisms to combat barriers to productive infection in the host cell. Virally-encoded miRNAs are one such means to regulate host gene expression in ways that benefit the virus lifecycle. miRNAs are small non-coding RNAs that regulate protein expression but do not trigger the adaptive immune response, making them powerful tools encoded by viruses to regulate cellular processes. Diverse viruses encode for miRNAs but little sequence homology exists between miRNAs of different viral species. Despite this, common cellular pathways are targeted for regulation, including apoptosis, immune evasion, cell growth and differentiation. Herein we will highlight the viruses that encode miRNAs and provide mechanistic insight into how viral miRNAs aid in lytic and latent infection by targeting common cellular processes. We also highlight how viral miRNAs can mimic host cell miRNAs as well as how viral miRNAs have evolved to regulate host miRNA expression. These studies dispel the myth that viral miRNAs are subtle regulators of gene expression, and highlight the critical importance of viral miRNAs to the virus lifecycle.

Targeting exosomes enveloped EBV-miR-BART1-5p-antagomiRs for NPC therapy through both anti-vasculogenic mimicry and anti-angiogenesis

BACKGROUND

Nasopharyngeal carcinoma (NPC) is a type of head and neck cancer with high incidence in China. The molecular mechanisms of vasculogenic mimicry (VM) and angiogenesis are not fully elucidated in NPC. More specially, it has seldomly been reported that Epstein-Barr virus-encoded miRNA can regulate VM and angiogenesis in NPC. The aim of this study was to investigate the function and molecular mechanism of a targeting exosome system (iRGD-exo-antagomiR) against VM and angiogenesis in NPC, and to provide new approaches for improving the comprehensive treatment of NPC.

METHODS

Exosomes were isolated by differential ultracentrifugation. Dynamic light scattering, transmission electron microscopy and western blotting were performed to characterize the exosomes. The 3D-Culture assay, tube formation assay, chicken chorioallantoic membrane assay, Matrigel plug assay, mouse xenograft tumor modeling and immunohistochemical staining were applied to evaluate the anti-VM and anti-angiogenic effects of the targeting exosome system in vitro and in vivo. Western blot was performed to detect the changes of downstream regulated networks following interference and recovery of the target gene.

RESULTS

In vitro or in vivo treatment with iRGD-tagged exosome containing antagomiR-BART1-5p specifically suppressed VM and angiogenesis in NPC. EBV-miR-BART1-5p promoted VM and angiogenesis in vitro and in vivo by regulating VEGF, PI3K, Akt, mTOR and HIF1-α in a Spry2-dependent manner.

CONCLUSIONS

Our findings demonstrated that targeting exosomes enveloped EBV-miR-BART1-5p-antagomiRs in a Spry2-dependent manner for NPC therapy through both anti-VM and anti-angiogenesis in vitro and in vivo.

Role of Exosomes and Their Potential as Biomarkers in Epstein-Barr Virus-Associated Gastric Cancer

Exosomes are a subtype of extracellular vesicles ranging from 30 to 150 nm and comprising many cellular components, including DNA, RNA, proteins, and metabolites, encapsulated in a lipid bilayer. Exosomes are secreted by many cell types and play important roles in intercellular communication in cancer. Viruses can hijack the exosomal pathway to regulate viral propagation, cellular immunity, and the microenvironment. Cells infected with Epstein-Barr virus (EBV), one of the most common oncogenic viruses, have also been found to actively secrete exosomes, and studies on their roles in EBV-related malignancies are ongoing. In this review, we focus on the role of exosomes in EBV-associated gastric cancer and their clinical applicability in diagnosis and treatment.

Exosomes loaded with circPARD3 promotes EBV-miR-BART4-induced stemness and cisplatin resistance in nasopharyngeal carcinoma side population cells through the miR-579-3p/SIRT1/SSRP1 axis

OBJECTIVE

To explore the effects of exosomes loaded with circular RNA PARD3 on EBV-miR-BART4-induced stemness and resistance of cisplatin in nasopharyngeal carcinoma side population (NPC-SP) cells through the miR-579-3p/SIRT1/SSRP1 axis.

METHODS

Sixty-five cancer tissues and 65 noncancerous tissues were collected from NPC patients or patients with rhinitis. The expressions of circPARD3, miR-579-3p, SIRT1, and SSRP1 were detected by qRT-PCR, western blot, or immunohistochemistry. In vivo tumor formation assay was performed in nude mice. Immunofluorescence and qRT-PCR were conducted for the determination of CD44 and CD133 expressions, and flow cytometry combined with Hoechst 33,342 dye efflux for identifying SP cells, CCK-8 and EdU assays for cell proliferation, and Transwell assay for migration and invasion.

RESULTS

CircPARD3, SIRT1, and SSRP1 were upregulated while miR-579-3p was downregulated in NPC tissues and cells. CircPARD3 was positively correlated with the expressions of SIRT1 and SSRP1, and miR-579-3p was negatively correlated with circPARD3, SIRT1, and SSRP1. Exosomes loaded with circPARD3 promoted EBV-miR-BART4-induced stemness and cisplatin resistance in NPC-SP cells, while miR-579-3p reversed the effect of exosomal circPARD3 on EBV-miR-BART4-induced stemness and cisplatin resistance in NPC-SP cells. Additionally, miR-579-3p suppressed EBV-miR-BART4-induced stemness and cisplatin resistance in NPC-SP cells by regulating SIRT1. SIRT1 upregulated SSRP1 expression by catalyzing H3K4 methylation and down-regulation of SSRP1 reversed the effect of SIRT1 on EBV-miR-BART4-induced stemness and cisplatin resistance in NPC-SP cells.

CONCLUSION

Exosomes loaded with circPARD3 promoted EBV-miR-BART4-induced stemness and cisplatin resistance in NPC-SP cells through the miR-579-3p/SIRT1/SSRP1 axis. Graphical Headlights • EBV-miR-BART4 induces the stemness and resistance of NPC-SP cells. • CircPARD3 regulates SIRT1 by miR-579-3p. • SIRT1 regulates SSRP1 expression by histone methylation. • Exosomes loaded with circPARD3 promotes EBV-miR-BART4-induced NPC-SP cell stemness and resistance by the miR-579-3p/SIRT1/SSRP1 axis.

The World of Oral Cancer and Its Risk Factors Viewed from the Aspect of MicroRNA Expression Patterns

Oral cancer is one of the leading causes of death worldwide, with a reported 5-year survival rate of around 50% after treatment. Epigenetic modifications are considered to have a key role in oral carcinogenesis due to histone modifications, aberrant DNA methylation, and altered expression of miRNAs. MicroRNAs (miRNAs) are small non-coding RNAs that have a key role in cancer development by regulating signaling pathways involved in carcinogenesis. MiRNA deregulation identified in oral cancer has led to the idea of using them as potential biomarkers for early diagnosis, prognosis, and the development of novel therapeutic strategies. In recent years, a key role has been observed for risk factors in preventing and treating this malignancy. The purpose of this review is to summarize the recent knowledge about the altered mechanisms of oral cancer due to risk factors and the role of miRNAs in these mechanisms.

Prognostic Value of Oral Epstein–Barr Virus DNA Load in Locoregionally Advanced Nasopharyngeal Carcinoma

Background: Plasma Epstein–Barr virus (EBV) DNA load has been widely used for nasopharyngeal carcinoma (NPC) prognostic risk stratification. However, oral EBV DNA load, a non-invasive biomarker that reflects the EBV lytic replication activity, has not been evaluated for its prognostic value in NPC yet.

Methods: A total number of 1,194 locoregionally advanced NPC (LA-NPC) patients from south China were included from a prospective observational cohort (GARTC) with a median follow-up of 107.3 months. Pretreatment or mid-treatment mouthwashes were collected for EBV DNA detection by quantitative polymerase chain reaction (qPCR). The difference of pre- and mid-treatment oral EBV DNA load was tested by the Wilcoxon signed-rank test. The associations of oral EBV DNA load with overall survival (OS), progression-free survival (PFS), distant metastasis–free survival (DMFS), and locoregional relapse-free survival (LRFS) were assessed using the log-rank test and multivariate Cox regression.

Results: The high level of the oral EBV DNA load (>2,100 copies/mL) was independently associated with worse OS (HR = 1.45, 95% CI: 1.20–1.74, p < 0.001), PFS (HR = 1.38, 95% CI: 1.16–1.65, p < 0.001), DMFS (HR = 1.66, 95% CI: 1.25–2.21, p = 0.001), and LRFS (HR = 1.43, 95% CI: 1.05–1.96, p = 0.023). Similar and robust associations between oral EBV DNA load and prognosis were observed for patients in both the pretreatment and mid-treatment stages. The detection rate (71.7 vs. 48.6%, p < 0.001) and the median load of oral EBV DNA (13,368 vs. 382 copies/mL, p < 0.001) for patients in the pretreatment stage were significantly higher than those in the mid-treatment stage. The combination of the oral EBV DNA load and TNM staging provided a more precise risk stratification for the LA-NPC patients.

Conclusion: Oral EBV DNA load was an alternative non-invasive predictor of prognosis and may facilitate risk stratification for the LA-NPC patients.

Aberrant miR-362-3p is Associated with EBV-Infection and Prognosis in Nasopharyngeal Carcinoma and Involved in Tumor Progression by Targeting JMJD2A

Background

Many microRNAs (miRNAs) are involved in the progression of nasopharyngeal carcinoma (NPC). This study aimed to examine the expression and clinical significance of microRNA (miR)-362-3p in NPC, especially in Epstein–Barr virus (EBV)-positive patients, and explore its potential mechanism in NPC progression.

Methods

miR-362-3p levels and Jumonji C domain 2A (JMJD2A) mRNA levels were detected by quantitative real-time PCR. The diagnostic value of miR-362-3p to distinguish NPC patients and EBV-positive cases was evaluated using receiver operating characteristic analysis. The association of miR-362-3p with NPC survival was assessed by Kaplan–Meier curves and Cox regression analysis. NPC cell proliferation, migration and invasion were determined using Cell Counting Kit-8 and Transwell assays, respectively. A luciferase reporter assay was used to confirm the interaction between miR-362-3p and JMJD2A.

Results

miR-362-3p expression was decreased in the serum and tissues of NPC patients and had diagnostic value for screening NPC. According to the survival follow-up, NPC survivors had significantly higher miR-362-3p, and miR-326-3p was demonstrated as an independent prognostic indicator of NPC. Interestingly, it is found that EBV-positive NPC patients and cells had significantly lower miR-362-3p compared with EBV-negative NPC patients and cells and had certain ability to distinguish EBV-positive patients. Moreover, miR-362-3p inhibited the proliferation, migration and invasion of both EBV-positive and -negative NPC cells, and these effects might be mediated by targeting JMJD2A.

Conclusion

Abnormal miR-362-3p expression is related to EBV-infection and prognosis in NPC patients and may be involved in NPC progression by targeting JMJD2A.

Epstein-Barr virus (EBV) encoded microRNA BART8-3p drives radioresistance-associated metastasis in nasopharyngeal carcinoma

Radiotherapy plays an important role in the treatment of nasopharyngeal carcinoma (NPC), however, 20% of patients with NPC exhibit unusual radioresistance. Patients with radioresistance are at risk of recurrence, so it is imperative to explore the mechanism of resistance to radiotherapy. In the past, studies on the mechanism of radioresistance have been restricted to DNA damage and related cell cycle remodeling or apoptosis. So far, no studies have explored the relationship between radioresistance and metastasis. Through the analysis of clinical samples, we observed that the metastasis rate of recurrent NPC was much higher than that of primary patients. In vitro and in vivo experiments showed that NPC cells with acquired radioresistance exhibited a stronger ability for invasion and metastasis. Mechanistically, we found that the Epstein-Barr virus (EBV)-encoded miRNA BART8-3p was increased in patients with NPC, and its expression was positively correlated with adverse prognostic factors, such as radioresistance. Besides this, miR-BART8-3p promoted the epithelial-mesenchymal transition, invasion, and metastasis of radioresistant NPC cells by targeting and inhibiting their PAG1 host gene. These findings suggested a novel role for EBV-miR-BART8-3p in promoting NPC radioresistance-associated metastasis and highlighted its potential value as a prognostic indicator or therapeutic target.

Epstein-Barr virus microRNA BART10-3p promotes dedifferentiation and proliferation of nasopharyngeal carcinoma by targeting ALK7

Non-keratinizing nasopharyngeal carcinoma, the major subtype of nasopharyngeal carcinoma, is characterized by low differentiation and a close relation to Epstein-Barr virus infection, which indicates a link between Epstein-Barr virus oncogenesis and loss of differentiation, and raises our interest in investigating the involvement of Epstein-Barr virus in nasopharyngeal carcinoma dedifferentiation. Our previous study showed abundant expression of an Epstein-Barr virus-encoded microRNA, BART10-3p, in nasopharyngeal carcinoma tissues, but the association between BART10-3p and nasopharyngeal carcinoma differentiation remains unknown. Here, we examined the expression and prognostic value of BART10-3p, and undertook bioinformatics analysis and functional assays to investigate the influence of BART10-3p on nasopharyngeal carcinoma differentiation and proliferation and the underpinning mechanism. Microarray analysis identified BART10-3p as the most significantly upregulated Epstein-Barr virus-encoded microRNA in nasopharyngeal carcinoma tissues and the upregulation was confirmed in two public datasets. The expression of BART10-3p was an independent unfavorable prognosticator in nasopharyngeal carcinoma and its integration with the clinical stage showed improved prognosis predictive performance. Bioinformatics analysis suggested a potential role of BART10-3p in tumor differentiation and progression. Functional assays demonstrated that BART10-3p could promote nasopharyngeal carcinoma cell dedifferentiation, epithelial-mesenchymal transition, and proliferation in vitro, and tumorigenicity in vivo. Mechanistically, BART10-3p directly targeted the 3'UTR of ALK7 and suppressed its expression. Reconstitution of ALK7 rescued BART10-3p-induced malignant phenotypes. Overall, our study demonstrates that BART10-3p promotes dedifferentiation and proliferation of nasopharyngeal carcinoma by targeting ALK7, suggesting a promising therapeutic opportunity to reverse the malignant phenotypes of nasopharyngeal carcinoma.

MicroRNA and Other Non-Coding RNAs in Epstein-Barr Virus-Associated Cancers

EBV is a direct causative agent in around 1.5% of all cancers. The oncogenic properties of EBV are related to its ability to activate processes needed for cellular proliferation, survival, migration, and immune evasion. The EBV latency program is required for the immortalization of infected B cells and involves the expression of non-coding RNAs (ncRNAs), including viral microRNAs. These ncRNAs have different functions that contribute to virus persistence in the asymptomatic host and to the development of EBV-associated cancers. In this review, we discuss the function and potential clinical utility of EBV microRNAs and other ncRNAs in EBV-associated malignancies. This review is not intended to be comprehensive, but rather to provide examples of the importance of ncRNAs.

Advances in research on microRNAs related to the invasion and metastasis of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC), which is associated with latent Epstein-Barr virus infection in most cases, is a unique epithelial malignancy arising from the nasopharyngeal mucosal lining. Accumulating evidence provides insights into the genetic and molecular aberrations that likely drive nasopharyngeal tumor development and progression. We review recent analyses of microRNAs (miRNAs), including Epstein-Barr virus-encoded miRNAs (EBV-encoded miRNAs) and dysregulated cellular miRNAs, that may be related to the metastasis of nasopharyngeal carcinoma. The studies summarized herein have greatly expanded our knowledge of the molecular biology of NPC involving miRNAs, and they may provide new biological targets for clinical diagnosis and reveal the potential of microRNA therapeutics. However, much information remains to be uncovered.

Oncogenic viruses and chemoresistance: What do we know?

Chemoresistance is often referred to as a major leading reason for cancer therapy failure, causing cancer relapse and further metastasis. As a result, an urgent need has been raised to reach a full comprehension of chemoresistance-associated molecular pathways, thereby designing new therapy methods. Many of metastatic tumor masses are found to be related with a viral cause. Although combined therapy is perceived as the model role therapy in such cases, chemoresistant features, which is more common in viral carcinogenesis, often get into way of this kind of therapy, minimizing the chance of survival. Some investigations indicate that the infecting virus dominates other leading factors, i.e., genetic alternations and tumor microenvironment, in development of cancer cell chemoresistance. Herein, we have gathered the available evidence on the mechanisms under which oncogenic viruses cause drug-resistance in chemotherapy.

Protein tyrosine phosphatase receptor type D gene promotes radiosensitivity via STAT3 dephosphorylation in nasopharyngeal carcinoma

Radiotherapy is essential to the treatment of nasopharyngeal carcinoma (NPC) and acquired or innate resistance to this therapeutic modality is a major clinical problem. However, the underlying molecular mechanisms in the radiation resistance in NPC are not fully understood. Here, we reanalyzed the microarray data from public databases and identified the protein tyrosine phosphatase receptor type D (PTPRD) as a candidate gene. We found that PTPRD was downregulated in clinical NPC tissues and NPC cell lines with its promoter hypermethylated. Functional assays revealed that PTPRD overexpression sensitized NPC to radiation in vitro and in vivo. Importantly, miR-454-3p directly targets PTPRD to inhibit its expression and biological effect. Interestingly, mechanistic analyses indicate that PTPRD directly dephosphorylates STAT3 to enhance Autophagy-Related 5 (ATG5) transcription, resulting in triggering radiation-induced autophagy. The immunohistochemical staining of 107 NPC revealed that low PTPRD and high p-STAT3 levels predicted poor clinical outcome. Overall, we showed that PTPRD promotes radiosensitivity by triggering radiation-induced autophagy via the dephosphorylation of STAT3, thus providing a potentially useful predictive biomarker for NPC radiosensitivity and drug target for NPC radiosensitization.

Targeting the signaling in Epstein-Barr virus-associated diseases: mechanism, regulation, and clinical study

Epstein–Barr virus-associated diseases are important global health concerns. As a group I carcinogen, EBV accounts for 1.5% of human malignances, including both epithelial- and lymphatic-originated tumors. Moreover, EBV plays an etiological and pathogenic role in a number of non-neoplastic diseases, and is even involved in multiple autoimmune diseases (SADs). In this review, we summarize and discuss some recent exciting discoveries in EBV research area, which including DNA methylation alterations, metabolic reprogramming, the changes of mitochondria and ubiquitin-proteasome system (UPS), oxidative stress and EBV lytic reactivation, variations in non-coding RNA (ncRNA), radiochemotherapy and immunotherapy. Understanding and learning from this advancement will further confirm the far-reaching and future value of therapeutic strategies in EBV-associated diseases.

EBV miR-BARTs and human lncRNAs: Shifting the balance in competing endogenous RNA networks in EBV-associated gastric cancer

Non-coding RNAs (ncRNAs) contribute to the regulation of gene expression. By acting as competing endogenous RNA (ceRNA), long non-coding RNAs (lncRNAs) hijack microRNAs (miRNAs) and inhibit their ability to bind their coding targets. Viral miRNAs can compete with and target the same transcripts as human miRNAs, shifting the balance in networks associated with multiple cellular processes and diseases. Epstein-Barr virus (EBV) is an example of how a subset of viral coding RNA and non-coding RNAs can cause deregulation of human transcripts and contribute to the development of EBV-associated malignancies. EBV non-coding transforming genes include lncRNAs (i.e circular RNAs), and small ncRNAs (i.e. miRNAs). Among the latter, most ongoing research has focused on miR-BARTs whereas target many genes associated with apoptosis and epithelial-mesenchymal transition, in EBV-associated gastric cancer (GC). In this review, we propose to include the interactions between EBV ncRNAs human transcripts in the hypothesis known as "competitive viral and host RNAs". These interactions may shift the balance in biological pathways such as apoptosis and epithelial-mesenchymal transition in EBV-associated gastric cancer.

EBV-Positive Gastric Cancer: Current Knowledge and Future Perspectives

Gastric cancer is the fifth most common malignant tumor and second leading cause of cancer-related deaths worldwide. With the improved understanding of gastric cancer, a subset of gastric cancer patients infected with Epstein–Barr virus (EBV) has been identified. EBV-positive gastric cancer is a type of tumor with unique genomic aberrations, significant clinicopathological features, and a good prognosis. After EBV infects the human body, it first enters an incubation period in which the virus integrates its DNA into the host and expresses the latent protein and then affects DNA methylation through miRNA under the action of the latent protein, which leads to the occurrence of EBV-positive gastric cancer. With recent developments in immunotherapy, better treatment of EBV-positive gastric cancer patients appears achievable. Moreover, studies show that treatment with immunotherapy has a high effective rate in patients with EBV-positive gastric cancer. This review summarizes the research status of EBV-positive gastric cancer in recent years and indicates areas for improvement of clinical practice.

Epstein-Barr virus microRNAs in the pathogenesis of human cancers

The Epstein-Barr Virus (EBV) is a gamma-herpesvirus involved with a variety of human cancers, notably the endemic Burkitt lymphoma and nasopharyngeal carcinoma. In 2004, EBV was described as one the first known human oncoviruses to encode viral microRNAs (miRNAs), and these molecules were found to interact with viral and host targets. EBV miRNAs modulate biological processes that are critical for carcinogenesis, contributing to cell transformation and tumor progression of EBV-associated cancers. Herein we review and discuss EBV miRNAs as modulators of viral biology and carcinogenesis, as well as their usefulness as putative markers to monitor the onset, progression, and recurrence of cancers associated with the EBV infection.

CYLD Promotes Apoptosis of Nasopharyngeal Carcinoma Cells by Regulating NDRG1

Purpose

Nasopharyngeal carcinoma (NPC) is among the most common malignancies derived from the epithelium of the nasopharynx. To date, the regulatory networks involved in NPC have not been fully identified. Previous studies revealed multiple loss-of-function mutations in NPC and specifically in cylindromatosis lysine 63 deubiquitinase (CYLD); however, the exact role of CYLD in NPC progression and its potential mechanism remains unclear.

Methods

We performed immunohistochemical (IHC) staining and real-time quantitative polymerase chain reaction (qPCR) to measure CYLD expression in NPC tissues, and Western blot was conducted to determine CYLD levels in NPC cell lines. Cell proliferation was detected by CCK8 assay and colony formation analysis, and apoptosis was determined by Annexin V/propidium iodide staining. Potential targets of CYLD were verified by co-immunoprecipitation and mass spectrometry. Xenograft assay was conducted to confirm the role of CYLD in vivo.

Results

We found that CYLD levels were significantly decreased in both NPC tissues and cell lines, and that CYLD overexpression inhibited NPC cell proliferation and promoted apoptosis. Additionally, we revealed that CYLD bound and upregulated N-Myc downstream regulated 1 (NDRG1), and that silencing NDRG1 abolished the tumor-suppressor effect of CYLD on NPC cells. Furthermore, CYLD suppressed tumor growth in xenograft mice models.

Conclusion

These results suggest CYLD as a tumor suppressor, potential biomarker for diagnosing NPC, and therapeutic target.

miR-4721, Induced by EBV-miR-BART22, Targets GSK3β to Enhance the Tumorigenic Capacity of NPC through the WNT/β-catenin Pathway

Nasopharyngeal carcinoma (NPC) is prevalent in East and Southeast Asia. In a previous study, Epstein-Barr virus (EBV)-miR-BART22 induces tumor metastasis and stemness and is significantly involved in NPC progression. In the present study, we observed that miR-4721 is induced by EBV-miR-BART22 through phosphatidylinositol 3-kinase (PI3K)/AKT/c-JUN/Sp1 signaling to promote its transcription. In a subsequent study, we observed that miR-4721 serves as a potential oncogenic factor promoting NPC cell cycle progression and cell proliferation in vitro and in vivo. Mechanism analysis indicated that miR-4721 directly targetes GSK3β and reduces its expression, which therefore elevates β-catenin intra-nuclear aggregation and activates its downstream cell cycle factors, including CCND1 and c-MYC. In clinical samples, miR-4721 and GSK3β are respectively observed to be upregulated and downregulated in NPC progression. Elevated expression of miR-4721 is positively associated with clinical progression and poor prognosis. Our study first demonstrated that miR-4721 as an oncogene is induced by EBV-miR-BART22 via modulating PI3K/AKT/c-JUN/Sp1 signaling to target GSK3β, which thus activates the WNT/β-catenin-stimulated cell cycle signal and enhances the tumorigenic capacity in NPC. miR-4721 may be a potential biomarker or therapeutic target in NPC treatment in the future.

Chemotherapy and chemo-resistance in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is closely associated with Epstein-Barr virus (EBV) and occurs frequently in the south of China and Southeast Asian countries. Concurrent chemo-radiotherapy is one of the main treatments for NPC. Although, the combined treatment of chemo-radiotherapy produces a satisfying survival rate, the chemo-resistance arises as a big obstacle in curing recurrent NPC patients. The acquirement of chemo-resistance is usually along with a poor prognosis. So far, the mechanism of chemo-resistance in NPC has not been fully elucidated and there have not been a comprehensive review on this issue. Thus, it is of great significance to summarize the mechanisms involved in NPC chemo-resistance. In this review, the importance and limitations of chemotherapy and the mechanisms of chemo-resistances in NPC were discussed.

Epstein-Barr virus BART microRNAs in EBV- associated Hodgkin lymphoma and gastric cancer

Background

EBV produces miRNAs with important functions in cancer growth, tumor invasion and host immune surveillance. The discovery of EBV miR-BARTs is recent, and most of their functions are still unknown. Nonetheless, some new studies underline their key roles in EBV-associated malignancies.

Main body

In EBV-associated tumors, the expression profile of miR-BARTs varies according to the cell type, autophagic process and signals received from the tumor microenvironment. By the same way of interest is the interaction between tumor cells and the tumor environment by the release of selected EBV miR-BARTs in addition to the tumor proteins trough tumor exosomes.

Conclusion

In this review, we discuss new findings regarding EBV miR-BARTs in Hodgkin lymphoma and gastric cancer. The recent discovery that miRNAs are released by exosomes, including miR-BARTs, highlights the importance of tumor and microenvironment interplay with more specific effects on the host immune response.

MiRNAs in Radiotherapy Resistance of Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is one of the most common malignant tumors of the head and neck in Southeast Asia and southern China. Although the comprehensive treatment based on intensity-modulated radiation therapy improves outcomes, the five-year survival rate of NPC patients is low, and the recurrence remains high. Radiotherapy resistance is the main cause of poor prognosis in NPC patients. MicroRNAs (miRNAs) are a class of endogenous non-coding RNAs regulating various biological functions in eukaryotes. These miRNAs can regulate the development and progression of nasopharyngeal carcinoma by affecting the proliferation, apoptosis, movement, invasion and metastasis of NPC cells. The abnormal expression of miRNAs is closely related to radiotherapy sensitivity and prognosis of NPC patients, which can affect the transmission of related signaling pathways by regulating the expression of tumor suppressor genes and / or oncogenes, and therefore participate in radiotherapy resistance in nasopharyngeal carcinoma. Here, we review the mechanisms by which miRNAs may be involved in the radiotherapy resistance of nasopharyngeal carcinoma.