New Insights from Elucidating the Role of LMP1 in Nasopharyngeal Carcinoma

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.

Combinations of radiotherapy with immunotherapy in nasopharyngeal carcinoma

BACKGROUND

The treatment of nasopharyngeal carcinoma (NPC) is currently based on concurrent chemoradiotherapy. The prognosis of early NPC is better, while the prognosis of advanced NPC is poor. Immunotherapy is becoming increasingly commonly employed in clinical practice as a new strategy for treating malignant tumors. It has shown promising results in the treatment of certain malignant tumors, making it a current clinical research hotspot.

METHODS

This review summarizes the current immunotherapy on NPC, highlighting the application of immunotherapy and radiotherapy in the treatment of NPC.

RESULTS

X-rays can either increase or suppress anti-tumor immune responses through various pathways and mechanisms. Immune checkpoint inhibitors can usually enhance X-ray-induced anti-tumor immune responses. Detecting the immune checkpoint markers and tumor mutation markers, and the functional status of effector cells in patients can aid in the development of individualized treatment that improves the treatment efficacy with reducing drug resistance and adverse reactions. The development of a multivalent vaccine for NPC will help improve the efficacy of the vaccine. Combining techniques that increase the tumor antigens release, such as radiotherapy and oncolytic virus vaccines, may enhance the ability of the immune response.

CONCLUSIONS

To shed further light on the application of immunotherapy in NPC, large pooled studies must accumulate sufficient cases with detailed exposure data.

Suppression of Nasopharyngeal and Gastric Tumor Growth in a Mouse Model by Antibodies to Epstein-Barr Virus LMP1 Protein

The study aimed to investigate the antitumor efficacy of anti-LMP1 antibodies in EBV-positive nasopharyngeal and stomach cell lines and xenograft models. The study also examined the NF-κB expression and cell cycle activation of NPC-serum-exosome-associated LMP1. Anti-LMP1 antibody treatment before or during cell implantation prevented tumor growth in nude mice. A small dose of antibodies resulted in complete tumor regression for at least three months after the tumors had grown in size. The consumption of antigen-antibody complexes by tumor cells limited tumor growth. In vitro experiments showed that anti-LMP1 antibodies killed EBV-positive NPC- or GC-derived epithelial cell lines and EBV-positive human B-cell lines but not EBV-negative cell lines. Treatment with anti-LMP1 reduced NF-κB expression in cells. The animal model experiments showed that anti-LMP1 inhibited and prevented NPC- or GC-derived tumor growth. The results suggest that LMP1 antibody immunotherapy could cure nasopharyngeal cancer, EBV-positive gastric carcinoma, and EBV-associated lymphomas. However, further validation of these findings is required through human clinical trials.

Cyclophilin A binds to AKT1 and facilitates the tumorigenicity of Epstein-Barr virus by mediating the activation of AKT/mTOR/NF-κB positive feedback loop

The AKT/mTOR and NF-κB signalings are crucial pathways activated in cancers including nasopharyngeal carcinoma (NPC), which is prevalent in southern China and closely related to Epstein-Barr virus (EBV) infection. How these master pathways are persistently activated in EBV-associated NPC remains to be investigated. Here we demonstrated that EBV-encoded latent membrane protein 1 (LMP1) promoted cyclophilin A (CYPA) expression through the activation of NF-κB. The depletion of CYPA suppressed cell proliferation and facilitated apoptosis. CYPA was able to bind to AKT1, thus activating AKT/mTOR/NF-κB signaling cascade. Moreover, the use of mTOR inhibitor, rapamycin, subverted the activation of the positive feedback loop, NF-κB/CYPA/AKT/mTOR. It is reasonable that LMP1 expression derived from initial viral infection is enough to assure the constant potentiation of AKT/mTOR and NF-κB signalings. This may partly explain the fact that EBV serves as a tumor-promoting factor with minimal expression of the viral oncoprotein LMP1 in malignancies. Our findings provide new insight into the understanding of causative role of EBV in tumorigenicity during latent infection.

Protein Farnesylation on Nasopharyngeal Carcinoma, Molecular Background and Its Potential as a Therapeutic Target

Simple Summary

Nasopharyngeal carcinoma is distinguished from other head and neck carcinomas by the association of its carcinogenesis with the Epstein–Barr virus. It is highly metastatic, and a novel therapeutic modality for metastatic nasopharyngeal carcinoma is keenly awaited. Protein farnesylation is a C-terminal lipid modification of proteins and was initially investigated as a key process in activating the RAS oncoprotein through its association with the cellular membrane structure. Since then, more and more evidence has accumulated to indicate that proteins other than RAS are also farnesylated and have significant roles in carcinogenesis. This review delineates molecular pathogenesis through protein farnesylation in the context of nasopharyngeal carcinoma and discusses the potential of farnesylation as a therapeutic target.

Abstract

Nasopharyngeal carcinoma (NPC) is one of the Epstein–Barr virus (EBV)-associated malignancies. NPC is highly metastatic compared to other head and neck carcinomas, and evidence has shown that the metastatic features of NPC are involved in EBV infection. The prognosis of advanced cases, especially those with distant metastasis, is still poor despite advancements in molecular research and its application to clinical settings. Thus, further advancement in basic and clinical research that may lead to novel therapeutic modalities is needed. Farnesylation is a lipid modification in the C-terminus of proteins. It enables proteins to attach to the lipid bilayer structure of cellular membranes. Farnesylation was initially identified as a key process of membrane association and activation of the RAS oncoprotein. Farnesylation is thus expected to be an ideal therapeutic target in anti-RAS therapy. Additionally, more and more molecular evidence has been reported, showing that proteins other than RAS are also farnesylated and have significant roles in cancer progression. However, although several clinical trials have been conducted in cancers with high rates of ras gene mutation, such as pancreatic carcinomas, the results were less favorable than anticipated. In contrast, favorable outcomes were reported in the results of a phase II trial on head and neck carcinoma. In this review, we provide an overview of the molecular pathogenesis of NPC in terms of the process of farnesylation and discuss the potential of anti-farnesylation therapy in the treatment of NPC.

Conformational change of adenine nucleotide translocase-1 mediates cisplatin resistance induced by EBV-LMP1

Adenine nucleotide translocase-1 (ANT1) is an ADP/ATP transporter protein located in the inner mitochondrial membrane. ANT1 is involved not only in the processes of ADP/ATP exchange but also in the composition of the mitochondrial membrane permeability transition pore (mPTP); and the function of ANT1 is closely related to its own conformational changes. Notably, various viral proteins can interact directly with ANT1 to influence mitochondrial membrane potential by regulating the opening of mPTP, thereby affecting tumor cell fate. The Epstein-Barr virus (EBV) encodes the key tumorigenic protein, latent membrane protein 1 (LMP1), which plays a pivotal role in promoting therapeutic resistance in related tumors. In our study, we identified a novel mechanism for EBV-LMP1-induced alteration of ANT1 conformation in cisplatin resistance in nasopharyngeal carcinoma. Here, we found that EBV-LMP1 localizes to the inner mitochondrial membrane and inhibits the opening of mPTP by binding to ANT1, thereby favoring tumor cell survival and drug resistance. The ANT1 conformational inhibitor carboxyatractyloside (CATR) in combination with cisplatin improved the chemosensitivity of EBV-LMP1-positive cells. This finding confirms that ANT1 is a novel therapeutic target for overcoming cisplatin resistance in the future.

The association between lncRNA H19 and EZH2 expression in patients with EBV-positive laryngeal carcinoma

Objective

Materials and methods

Results

Conclusions

Epstein-Barr Virus Latent Membrane Protein-1 Expression in Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC), a malignant neoplasm of the epithelium covering the nasopharynx, is a rare disease in most parts of the world. Epstein-Barr virus (EBV), the most potent oncogenic virus, coupled with environmental and genetic factors has been identified to play a role in the development of NPC. An array of methods for detecting the virus do exist, from serologic detection of antibodies to DNA amplification. There is paucity of local data on the status of EBV infection in relation to NPC within the region, and this study attempts to shed more light on the subject.

With prospects of immunotherapy for nasopharyngeal carcinoma, can resource constrained centers use IHC to detect EBV infection in NPC? We report of the first ever documented use of LMP-1 IHC for the detection of EBV in NPC in Tanzania.

The roles of ribosomal proteins in nasopharyngeal cancer: culprits, sentinels or both

Ribosomal protein genes encode products that are essential for cellular protein biosynthesis and are major components of ribosomes. Canonically, they are involved in the complex system of ribosome biogenesis pivotal to the catalysis of protein translation. Amid this tightly organised process, some ribosomal proteins have unique spatial and temporal physiological activity giving rise to their extra-ribosomal functions. Many of these extra-ribosomal roles pertain to cellular growth and differentiation, thus implicating the involvement of some ribosomal proteins in organogenesis. Consequently, dysregulated functions of these ribosomal proteins could be linked to oncogenesis or neoplastic transformation of human cells. Their suspected roles in carcinogenesis have been reported but not specifically explained for malignancy of the nasopharynx. This is despite the fact that literature since one and half decade ago have documented the association of ribosomal proteins to nasopharyngeal cancer. In this review, we explain the association and contribution of dysregulated expression among a subset of ribosomal proteins to nasopharyngeal oncogenesis. The relationship of these ribosomal proteins with the cancer are explained. We provide information to indicate that the dysfunctional extra-ribosomal activities of specific ribosomal proteins are tightly involved with the molecular pathogenesis of nasopharyngeal cancer albeit mechanisms yet to be precisely defined. The complete knowledge of this will impact future applications in the effective management of nasopharyngeal cancer.

A primary nasopharyngeal three-dimensional air-liquid interface cell culture model of the pseudostratified epithelium reveals differential donor- and cell type-specific susceptibility to Epstein-Barr virus infection

Epstein-Barr virus (EBV) is a ubiquitous γ-herpesvirus with latent and lytic cycles. EBV replicates in the stratified epithelium but the nasopharynx is also composed of pseudostratified epithelium with distinct cell types. Latent infection is associated with nasopharyngeal carcinoma (NPC). Here, we show with nasopharyngeal conditionally reprogrammed cells cultured at the air-liquid interface that pseudostratified epithelial cells are susceptible to EBV infection. Donors varied in susceptibility to de novo EBV infection, but susceptible cultures also displayed differences with respect to pathogenesis. The cultures from one donor yielded lytic infection but cells from two other donors were positive for EBV-encoded EBERs and negative for other lytic infection markers. All cultures stained positive for the pseudostratified markers CK7, MUC5AC, α-tubulin in cilia, and the EBV epithelial cell receptor Ephrin receptor A2. To define EBV transcriptional programs by cell type and to elucidate latent/lytic infection-differential changes, we performed single cell RNA-sequencing on one EBV-infected culture that resulted in alignment with many EBV transcripts. EBV transcripts represented a small portion of the total transcriptome (~0.17%). All cell types in the pseudostratified epithelium had detectable EBV transcripts with suprabasal cells showing the highest number of reads aligning to many EBV genes. Several restriction factors (IRF1, MX1, STAT1, C18orf25) known to limit lytic infection were expressed at lower levels in the lytic subcluster. A third of the differentially-expressed genes in NPC tumors compared to an uninfected pseudostratified ALI culture overlapped with the differentially-expressed genes in the latent subcluster. A third of these commonly perturbed genes were specific to EBV infection and changed in the same direction. Collectively, these findings suggest that the pseudostratified epithelium could harbor EBV infection and that the pseudostratified infection model mirrors many of the transcriptional changes imposed by EBV infection in NPC.

It has been known for over 50 years that EBV infection is associated with NPC. Despite many advances from studies in 2-dimensional cell culture, many aspects of EBV molecular pathogenesis in the nasopharynx remain undefined because the cell types and the biology of the nasopharyngeal epithelium can only be faithfully captured in 3-dimensional cell culture. In the stratified epithelium, cellular differentiation triggers lytic infection but it is not clear to what degree the pseudostratified epithelium is involved. The pseudostratified epithelium is abundant in the lateral wall where the lymphoid-rich fossa of Rosenmüller is located and is a site where NPC tumors most often arises. While the oral epithelium is a site of EBV replication, whether the nasopharyngeal epithelium is a major source of EBV shedding in the nasopharynx is not well defined. Here, we present a 3-dimensional organoid model of the nasopharyngeal pseudostratified epithelium showing that such cells can be infected with EBV in some donor cultures, with examples of both latent and lytic infection. We propose that the cell types of the pseudostratified epithelium should be considered a component of EBV pathogenesis in the nasopharynx and that the difference in donor susceptibility and latent/lytic infection could influence EBV’s fitness in the nasopharynx.

The Role of EBV-Encoded LMP1 in the NPC Tumor Microenvironment: From Function to Therapy

Nasopharyngeal carcinoma (NPC) is closely associated with Epstein-Barr virus (EBV) infection. It is also characterized by heavy infiltration with non-malignant leucocytes. The EBV-encoded latent membrane protein 1 (LMP1) is believed to play an important role in NPC pathogenesis by virtue of its ability to activate multiple cell signaling pathways which collectively promote cell proliferation and survival, angiogenesis, invasiveness, and aerobic glycolysis. LMP1 also affects cell-cell interactions, antigen presentation, and cytokine and chemokine production. Here, we discuss how LMP1 modulates local immune responses that contribute to the establishment of the NPC tumor microenvironment. We also discuss strategies for targeting the LMP1 protein as a novel therapy for EBV-driven malignancies.

Intra-host changes in Kaposi sarcoma-associated herpesvirus genomes in Ugandan adults with Kaposi sarcoma

Intra-host tumor virus variants may influence the pathogenesis and treatment responses of some virally-associated cancers. However, the intra-host variability of Kaposi sarcoma-associated herpesvirus (KSHV), the etiologic agent of Kaposi sarcoma (KS), has to date been explored with sequencing technologies that possibly introduce more errors than that which occurs in the viral population, and these studies have only studied variable regions. Here, full-length KSHV genomes in tumors and/or oral swabs from 9 Ugandan adults with HIV-associated KS were characterized. Furthermore, we used deep, short-read sequencing using duplex unique molecular identifiers (dUMI)–random double-stranded oligonucleotides that barcode individual DNA molecules before library amplification. This allowed suppression of PCR and sequencing errors to ~10⁻⁹/base as well as afforded accurate determination of KSHV genome numbers sequenced in each sample. KSHV genomes were assembled de novo, and rearrangements observed were confirmed by PCR and Sanger sequencing. 131-kb KSHV genome sequences, excluding major repeat regions, were successfully obtained from 23 clinical specimens, averaging 2.3x10⁴ reads/base. Strikingly, KSHV genomes were virtually identical within individuals at the point mutational level. The intra-host heterogeneity that was observed was confined to tumor-associated KSHV mutations and genome rearrangements, all impacting protein-coding sequences. Although it is unclear whether these changes were important to tumorigenesis or occurred as a result of genomic instability in tumors, similar changes were observed across individuals. These included inactivation of the K8.1 gene in tumors of 3 individuals and retention of a region around the first major internal repeat (IR1) in all instances of genomic deletions and rearrangements. Notably, the same breakpoint junctions were found in distinct tumors within single individuals, suggesting metastatic spread of rearranged KSHV genomes. These findings define KSHV intra-host heterogeneity in vivo with greater precision than has been possible in the past and suggest the possibility that aberrant KSHV genomes may contribute to aspects of KS tumorigenesis. Furthermore, study of KSHV with use of dUMI provides a proof of concept for utilizing this technique for detailed study of other virus populations in vivo.

Kaposi sarcoma (KS) is a leading cancer in sub-Saharan Africa and in persons with HIV co-infection. Kaposi sarcoma-associated herpesvirus (KSHV, also referred to as human herpesvirus-8, or HHV-8) is the etiologic agent of KS, but the factors that contribute to the development of KS, which occurs in only a small subset of infected individuals, remain largely unknown. While strain differences or mutations in other tumor viruses are known to affect the risk and progression of their associated cancers, whether genetic variation in KSHV is important to the natural history of KS is unclear. Most studies of KSHV diversity have only characterized ~4% of its 165-kb genome, and the observed variation in some studies is likely to have been impacted by PCR or cloning artifacts. To precisely define genomic diversity of KSHV in vivo, we evaluated full-length viral genomes (except the internal repeat regions) using a technique that greatly lowers sequencing error rates and thus measures genomic diversity much more accurately than previous studies. In addition, we extended our analyses to look for potential tumor-specific changes in the KSHV genomes by examining viruses in both tumor and non-tumor tissues. To these ends, we performed highly sensitive, single-molecule sequencing of whole KSHV genomes in paired KS tumors and oral swabs from 9 individuals with KS. We found that KSHV genomes were virtually identical within the 9 individuals, with no evidence of quasispecies formation or multi-strain infection. However, KSHV genome aberrations and gene-inactivating mutations were found to be common in KS tumors, often impacting the same genes and genomic regions across individuals. Whether theses mutations influence KS tumorigenesis or result from genomic instability commonly found in tumors warrants further study. Lastly, aberrant KSHV genomes were found to be shared by distinct tumors within individuals, suggesting the capacity of KS tumor cells to metastasize and seed new lesions.

mSphere of Influence: 3-D Culture Models Influence Studies on Epstein-Barr Virus Molecular Pathogenesis in the Epithelium

Kathy Shair works in the field of Epstein-Barr virus (EBV)-associated cancers, with emphasis on nasopharyngeal carcinoma (NPC). In this mSphere of Influence article, she reflects on how the paper "Efficient replication of Epstein-Barr virus in stratified epithelium in vitro" by Temple et al. (R. M. Temple, J. Zhu, L. Budgeon, N. D. Christensen, et al., Proc Natl Acad Sci U S A 111:16544-16549, 2014, https://doi.org/10.1073/pnas.1400818111) has influenced her work on EBV molecular pathogenesis in the nasopharynx by highlighting the importance of using three-dimensional (3-D) culture models to study epithelial infection.

Epstein-Barr Virus Mediated Signaling in Nasopharyngeal Carcinoma Carcinogenesis

Simple Summary

Epstein-Barr virus (EBV) infection is known to contribute in nasopharyngeal carcinoma (NPC) carcinogenesis. The oncogenic roles of the EBV proteins and non-coding RNAs in NPC are becoming evident with the aid of current advances in genome-wide and in-depth molecular analyses. This current work provides a comprehensive overview, which covers recent understandings of the pathogenic role of EBV infection in NPC. Perspectives on molecular mechanisms, which are involved in the pathogenesis of NPC, focusing on the connection between EBV and NPC cells and the corresponding signaling pathways are highlighted. Cancer hallmarks associated with EBV in NPC development are also discussed herein.

Abstract

Nasopharyngeal carcinoma (NPC) is one of the most common tumors occurring in China and Southeast Asia. Etiology of NPC seems to be complex and involves many determinants, one of which is Epstein-Barr virus (EBV) infection. Although evidence demonstrates that EBV infection plays a key role in NPC carcinogenesis, the exact relationship between EBV and dysregulation of signaling pathways in NPC needs to be clarified. This review focuses on the interplay between EBV and NPC cells and the corresponding signaling pathways, which are modulated by EBV oncoproteins and non-coding RNAs. These altered signaling pathways could be critical for the initiation and progression of NPC.

Comparative study of FosPeg® photodynamic effect on nasopharyngeal carcinoma cells in 2D and 3D models

Photodynamic Therapy (PDT) offers an alternative option for the treatment of nasopharyngeal carcinoma (NPC). The utilization of 3-dimensional (3D) culture model might provide better understanding of PDT effects on NPC cells. The aim of this in vitro study was to compare PDT effect on NPC cells using 2D and 3D models. Two 3D culture models were established using liquid overlay method with agarose base (MCL) and hanging drop method (MCS). PDT was carried out using the combination of FosPeg® and 652 nm laser in 3D and conventional 2D models. The effects of 3D culture size and morphology on the uptake and distribution of sensitizer and gene expression were examined. Photocytotoxity, mode of cell death, and protein expression were compared for 2D and 3D models. Regular and irregular NPC spheroids were obtained from MCL and MCS methods, respectively. A significantly down-regulation of LMP1 mRNA were observed in MCL spheroid. The sensitizer uptake in 3D spheroids was half of 2D culture. More sensitizers were required to obtain IC₅₀ in 3D spheroids. Apoptosis, necrosis and autophagosomes were detected in PDT treated 2D and 3D cells. Different protein expression patterns were observed in 2D and 3D models. FosPeg® PDT is effective in killing NPC cells. MCL-derived 3D spheroid model is more suitable for the evaluation of PDT killing mechanisms.

Evaluation of the effect of 5-aminolevulinic acid hexyl ester (H-ALA) PDT on EBV LMP1 protein expression in human nasopharyngeal cells

Nasopharyngeal carcinoma (NPC) is of high prevalence in Hong Kong and southern China. The pathogenesis of NPC is closely associated with Epstein-Barr virus (EBV) infection via regulation of viral oncoprotein latent membrane protein 1 (LMP1). The conventional treatment for NPC is chemo-radiotherapy, but the prognosis remains poor for advanced stage, recurrent and metastatic NPC. Photodynamic therapy (PDT) is a therapeutic approach to combat tumors. PDT effectiveness depends on the interaction of photosensitizers, light and molecular oxygen. 5- aminolevulinic acid hexyl derivative (H-ALA) is one of the photosensitizers derived from 5-ALA. H-ALA with improved lipophilic properties by adding a long lipophilic chain (hexyl group) to 5-ALA, resulted in better penetration into cell cytoplasm. In this study, the effect of H-ALA-PDT on NPC cells (EBV positive C666-1 and EBV negative CNE2) was investigated. The H-ALA mediated cellular uptake and cytotoxicity was revealed via flow cytometry analysis and MTT assay respectively. H-ALA PDT mediated protein modulation was analysed by western blot analysis. Our finding reported that the cellular uptake of H-ALA in C666-1 and CNE2 cells was in a time dependent manner. H-ALA PDT was effective to C666-1 and CNE2 cells. EBV LMP1 proteins was expressed in C666-1 cells only and its expression was responsive to H-ALA PDT in a dose dependent manner. This work revealed the potential of H-ALA PDT as a treatment regiment for EBV positive NPC cells. Understanding the mechanism of H-ALA mediated PDT could develop improved strategies for the treatment of NPC.

Capn4 is induced by and required for Epstein-Barr virus latent membrane protein 1 promotion of nasopharyngeal carcinoma metastasis through ERK/AP-1 signaling

Capn4, also known as CapnS1, is a member of the calpain family, which plays a crucial role in maintaining the activity and function of calpain. We previously reported that Capn4 also plays an essential role in the migration of nasopharyngeal carcinoma (NPC) cells through regulation of (MMP‐2) by nuclear factor‐kappa B activation. Epstein‐Barr virus latent membrane protein 1 (LMP1) is closely related to the malignant functions of NPC; however, the relationship between LMP1 and Capn4 in NPC remain unclear. Immunohistochemical studies showed that the level of LMP1 and Capn4 expression was high in both primary and metastatic NPC tissues, with a significantly positive correlation. We further found that LMP1 was able to upregulate the Capn4 promoter in a dose‐dependent way through the C‐terminal activation region (CTAR)1 and CTAR2 domains to activate AP‐1. Moreover, we also found that LMP1 activated AP‐1 through ERK/JNK phosphorylation. These findings indicate that Capn4 coordination with LMP1 promotes actin rearrangement and, ultimately, cellular migration. These results show that Capn4 coordination with LMP1 enhances NPC migration by increasing actin rearrangement involving ERK/JNK/AP‐1 signaling. Therapeutically, additional and more specific LMP1 and Capn4 targeted inhibitors could be exploited to treat NPC.

Translational genomics of nasopharyngeal cancer

Nasopharyngeal carcinoma (NPC), also named the Cantonese cancer, is a unique cancer with strong etiological association with infection of the Epstein-Barr virus (EBV). With particularly high prevalence in Southeast Asia, the involvement of EBV and genetic aberrations contributive to NPC tumorigenesis have remained unclear for decades. Recently, genomic analysis of NPC has defined it as a genetically homogeneous cancer, driven largely by NF-κB signaling caused by either somatic aberrations of NF-κB negative regulators or by overexpression of the latent membrane protein 1 (LMP1), an EBV viral oncoprotein. This represents a landmark finding of the NPC genome. Exome and RNA sequencing data from new EBV-positive NPC models also highlight the importance of PI3K pathway aberrations in NPC. We also realize for the first time that NPC mutational burden, mutational signatures, MAPK/PI3K aberrations, and MHC Class I gene aberrations, are prognostic for patient outcome. Together, these multiple genomic discoveries begin to shape the focus of NPC therapy development. Given the challenge of NF-κB targeting in human cancers, more innovative drug discovery approaches should be explored to target the unique atypical NF-κB activation feature of NPC. Our next decade of NPC research should focus on further identification of the -omic landscapes of recurrent and metastatic NPC, development of gene-based precision medicines, as well as large-scale drug screening with the newly developed and well-characterized EBV-positive NPC models. Focused preclinical and clinical investigations on these major directions may identify new and effective targeting strategies to further improve survival of NPC patients.

Positive Correlative over-Expression between eIF4E and Snail in Nasopharyngeal Carcinoma Promotes its Metastasis and Resistance to Cisplatin

EIF4E is the rate-limiting factor in the mRNA translation of specific set of oncogenes. Snail is the core transcription factor of epithelial-mesenchymal transition (EMT), a key step of cancer metastasis. The connection between the two oncoproteins has not been well established in the human cancer tissues and in nasopharyngeal carcinoma (NPC). Here we showed that the positive correlative over-expression was seen between eIF4E and Snail in NPC tissues, and the expression was significantly higher in the metastatic NPC than in the un-metastatic NPC. In NPC cells, eIF4E knockdown significantly reduced Snail mRNA and protein levels, increased the mRNA level of E-cad (a direct downstream gene of Snail and a negative EMT marker), attenuated the invasive ability of the cells, and sensitized the cells to cisplatin in invasion. In contrast, enforced the expression of eIF4E significantly increased Snail mRNA and protein levels, and promoted the invasive ability in NPC cells. Under the condition of the high eIF4E expression, Snail knockdown significantly increased E-cad mRNA level and weaken the invasive ability of NPC cells. Finally, eIF4E directly bound Snail mRNA for translation initiation displayed by the RIP assay. Therefore, the results firstly suggested that eIF4E enhanced the Snail expression in both transcription and translation manner in human cancer tissues and targeting the eIF4E/Snail axis might intervene with the EMT and metastasis of NPC. This finding provided a new clue for further understanding the metastatic mechanism of human cancers and for preventing and treating NPC metastasis.

Efficient Epstein-Barr Virus Progeny Production Mediated by Cancer-Derived LMP1 and Virally-Encoded microRNAs

Epstein-Barr virus (EBV) genomes, particularly their latent genes, are heterogeneous among strains. The heterogeneity of EBV-encoded latent membrane protein 1 (LMP1) raises the question of whether there are functional differences between LMP1 expressed by cancer-associated EBV and that by non-cancerous strains. Here, we used bacterial artificial chromosome (BAC)-cloned EBV genomes retaining all virally encoded microRNA (miRNA) genes to investigate the functions of cancer-derived LMP1 in the context of the EBV genome. HEK293 cells were stably transfected with EBV-BAC clone DNAs encoding either nasopharyngeal carcinoma (NPC)-derived CAO-LMP1 (LMP1_CAO) or LMP1 from a prototype B95-8 strain of EBV (LMP1_B95-8). When an EBV-BAC clone DNA encoding LMP1_CAO was stably transfected into HEK293 cells, it generated many more stable transformants than the control clone encoding LMP1_B95-8. Furthermore, stably transfected HEK293 cells exhibited highly efficient production of progeny virus. Importantly, deletion of the clustered viral miRNA genes compromised the ability to produce progeny viruses. These results indicate that cancer-derived LMP1 and viral miRNAs together are necessary for efficient production of progeny virus, and that the resulting increase in efficiency contributes to EBV-mediated epithelial carcinogenesis.

FOXO3a knockdown promotes radioresistance in nasopharyngeal carcinoma by inducing epithelial-mesenchymal transition and the Wnt/β-catenin signaling pathway

Mutations in the forkhead box O 3a (FOXO3a) gene are closely related to the progression of several types of cancers. However, few studies explore the relationship between FOXO3a and nasopharyngeal carcinoma (NPC). Our findings demonstrate that silencing FOXO3a promotes tumor radioresistance of NPC in vitro and in vivo through inducing EMT and activating Wnt/β-catenin signal pathway. These data establish that FOXO3a can be a novel and reliable NPC marker and a potential therapeutic target against NPC.

Caffeic acid phenethyl ester suppressed growth and metastasis of nasopharyngeal carcinoma cells by inactivating the NF-κB pathway

Purpose: Caffeic acid phenethyl ester (CAPE) is the main polyphenol extracted from honeybee propolis, which inhibits the growth of several kinds of tumor. This study aimed to assess the inhibitory effect of CAPE in nasopharyngeal carcinoma (NPC), evaluate the synergistic action of CAPE in radiotherapy sensitivity of NPC cell lines and further elucidate the possible molecular mechanism involved.

Materials and methods: CCK-8 assay was used to analyze cell proliferation ability. Colony formation assay was used to evaluate the clonogenic ability and radio-sensitiveness of NPC cells by CAPE treatment. Wound-healing and transwell assay were used to assess the motility of cells. The expression of key molecules of the epithelial–mesenchymal transition (EMT) was determined by western blot analysis and changes in radiation sensitivity were measured by colony-formation assay. cDNA microarray analysis was used to determine differentially expressed genes with and without CAPE treatment, with Gene Ontology enrichment of gene function and KEGG pathways determined. Cell cycle and apoptosis were detected by flow cytometry and western blot analysis.

Results: CAPE suppressed the viability of NPC cell lines time- and dose-dependently. It induced apoptosis in NPC cells along with decreased expression of Bcl-XL and increased cleavage of PARP and expression of Bax. G1 phase arrest was induced by CAPE with ower expression of CDK4, CDK6, Rb and p-Rb. The migratory and invasive ability of NPC cells was decreased by the EMT pathway. The irradiation sensitivity of NPC cells was enhanced with CAPE treatment. CAPE specifically inhibited nuclear factor κB (NF-κB) signaling pathway by suppressing p65 subunit translocation from cytoplasm to nucleus. CAPE treatment was synergistic with chemotherapy and radiotherapy.

Conclusion: CAPE may inhibit the proliferation and metastasis of NPC cells but enhance radiosensitivity in NPC therapy by inhibiting the NF-κB pathway. CAPE could be a potential therapeutic compound for NPC therapy.

The Epstein-Barr virus LMP1 interactome: biological implications and therapeutic targets

The oncogenic potential of Epstein-Barr virus (EBV) is mostly attributed to latent membrane protein 1 (LMP1), which is essential and sufficient for transformation of fibroblast and primary lymphocytes. LMP1 expression results in the activation of multiple signaling cascades like NF-ΚB and MAP kinases that trigger cell survival and proliferative pathways. LMP1 specific signaling events are mediated through the recruitment of a number of interacting proteins to various signaling domains. Based on these properties, LMP1 is an attractive target to develop effective therapeutics to treat EBV-related malignancies. In this review, we focus on LMP1 interacting proteins, associated signaling events, and potential targets that could be exploited for therapeutic strategies.

Modified Anoikis Assay That Functionally Segregates Epstein-Barr Virus LMP1 Strains into Two Groups

Nasopharyngeal carcinoma (NPC) is a metastatic Epstein-Barr virus (EBV)-associated cancer that expresses the viral oncogenic protein, latent membrane protein 1 (LMP1). During epithelial metastasis, detached cells must overcome anoikis-induced cell death and gain the ability to reattach and restore growth potential. Anoikis assays have revealed cell survival mechanisms during suspension, but few studies have tracked the fate of cells surviving anoikis-inducing conditions. In this study, a modified anoikis assay was used to examine if the expression of LMP1 confers the recovery of epithelial cells from anoikis. Cells expressing LMP1 mutants and strains were evaluated for distinguishing properties in survival during suspension, reattachment, and outgrowth potential. Expression of LMP1 promoted the outgrowth of the NPC cell line HK1 following anoikis induction that was not attributed to enhanced cell survival in suspension or reattachment. The mechanism of LMP1-induced outgrowth required Akt signaling and the conserved PXQXT motif on LMP1, which activates Akt. Deletion of any of the three LMP1 C-terminal activation regions (CTAR) abrogated anoikis recovery, suggesting that additional LMP1-regulated signaling pathways are likely involved. Of the seven LMP1 strains, only B958, China1, and Med⁺ promoted HK1 outgrowth from anoikis. This distinguishing biological property segregates LMP1 strains into two categories (anoikis recovering and nonrecovering) and suggests that LMP1 strain-specific sequences may be important in determining metastatic outgrowth potential in NPC tumors.IMPORTANCE LMP1 is one of the most divergent sequences in the EBV genome and phylogenetically segregates into seven LMP1 strains. The LMP1 strains differ in geographical distribution and NPC tumor prevalence, but the molecular basis for this potential selection is not clear. While there are signaling motifs conserved in all LMP1 sequences from circulating EBV isolates, phylogenetic studies of NPC also suggest that there may be sequence selection for tumor-associated LMP1 strains and polymorphisms. The present study describes a modified anoikis assay that can distinguish LMP1 strains into two groups by biological properties. The pleiotropic LMP1 signaling properties and sequence diversity may offer a unique opportunity to illuminate the complex mechanisms of metastasis. Although the host genomic landscape is variable between NPC tumors, the present functional-mapping studies on LMP1 support the notion that viral proteins could serve as molecular tool kits and potentially reveal sequence-associated risk factors in NPC metastatic progression.

Air-Liquid Interface Method To Study Epstein-Barr Virus Pathogenesis in Nasopharyngeal Epithelial Cells

Epstein-Barr virus (EBV) is a ubiquitous gammaherpesvirus that establishes a latent reservoir in peripheral B-lymphocytes with sporadic reactivation. EBV also infects epithelial cells, predominantly resulting in a lytic infection, which may contribute to EBV transmission from saliva. In the nasopharynx, EBV infection can lead to the clonal expansion of a latently infected cell and the development of nasopharyngeal carcinoma (NPC). The mechanisms governing EBV pathogenesis in nasopharyngeal epithelium are largely unknown. An advanced understanding would depend on a physiologically relevant culture model of polarized airway epithelium. The recent application of the organotypic raft culture in keratinocytes has demonstrated great promise for the use of polarized cultures in the study of EBV permissive replication. In this study, the adaptation of an air-liquid interface (ALI) culture method using transwell membranes was explored in an EBV-infected NPC cell line. In the EBV-infected NPC HK1 cell line, ALI culture resulted in the completion of EBV reactivation, with global induction of the lytic cascade, replication of EBV genomes, and production of infectious progeny virus. We propose that the ALI culture method can be widely adopted as a physiologically relevant model to study EBV pathogenesis in polarized nasal epithelial cells.

IMPORTANCE

Lifting adherent cells to the air-liquid interface (ALI) is a method conventionally used to culture airway epithelial cells into polarized apical and basolateral surfaces. Reactivation of Epstein-Barr virus (EBV) from monolayer epithelial cultures is sometimes abortive, which may be attributed to the lack of authentic reactivation triggers that occur in stratified epithelium in vivo In the present work, the ALI culture method was applied to study EBV reactivation in nasopharyngeal epithelial cells. The ALI culture of an EBV-infected cell line yielded high titers and can be dissected by a variety of molecular virology assays that measure induction of the EBV lytic cascade and EBV genome replication and assembly. EBV infection of polarized cultures of primary epithelial cells can be challenging and can have variable efficiencies. However, the use of the ALI method with established EBV-infected cell lines offers a readily available and reproducible approach for the study of EBV permissive replication in polarized epithelia.

Genomic Landscapes of EBV-Associated Nasopharyngeal Carcinoma vs. HPV-Associated Head and Neck Cancer

: Epstein-Barr virus-positive nasopharyngeal carcinoma (EBV(+) NPC), and human papillomavirus-positive head and neck squamous cell carcinoma (HPV(+) HNSCC) are two distinct types of aggressive head and neck cancers with early age onsets. Their recently identified genomic landscapes by whole-exome sequencing (WES) clearly reveal critical roles of: (1) inflammation via NF-kB activation, (2) survival via PI3K aberrations, and perhaps (3) immune evasion via MHC loss in these cancers as summarized in this review. Immediate outcomes of these WES studies include the identification of potential prognostic biomarkers, and druggable events for these cancers. The impact of these genomic findings on the development of precision medicine and immunotherapies will be discussed. For both of these cancers, the main lethality comes from metastases and disease recurrences which may represent therapy resistance. Thus, potential curing of these cancers still relies on future identification of key genomic drivers and likely druggable events in recurrent and metastatic forms of these intrinsically aggressive cancers of the head and neck.