EBV-infected Nasopharyngeal Epithelial Cells Research Articles

The Comparison of Biomolecular Changes of Epstein-Barr Virus Infection in Nasopharyngeal Epithelial Cells Using Confocal Raman Microspectroscopy.

Due to its unique fingerprinting properties, Confocal Raman microscopy (CRM) can be used to examine the biomolecular changes of viruses invading and manipulating host cells. Recently, the biochemical changes due to the invasion and infection of B lymphocyte cells, nerve cells, and epithelial cells by Epstein-Barr virus (EBV) have been reported. However, biomolecular changes in nasopharyngeal epithelial cells that result from EBV infection are still poorly understood. In continuation of our prior investigation of EBV infection in nasopharyngeal epithelial cells, we tried to expound on biomolecular changes in EBV-infected nasopharyngeal epithelial cells using Raman microspectroscopy. EBV has two life cycles, latent infection and lytic replication. We have established latent and lytic infection models at the cellular level. In order to understand the characteristics of the two patterns of EBV infection, we used Raman spectroscopy to identify the changes in biomolecules of EBV latent cells (CNE2, CNE2-EBV) and lytic cells (NPEC1-BMI1-CN, NPEC1-BMI1-EBV). During latent infection, levels of glycogen, protein, and lipid molecules in the cell increased while levels of nucleic acid and collagen molecules decreased. Molecular levels of glycogen, proteins, and nucleic acids are reduced during lytic infection. We found that molecular levels of nucleic acid decreased during two different periods of infection, whereas levels of other biomolecules showed the opposite trend. Glycogen, proteins, lipids, nucleic acids, and other molecules are associated with alterations in cellular biochemical homeostasis. These changes correspond to unique Raman spectra in infected and uninfected cells associated with specific biomolecules that have been proven. These molecules are mainly responsible for cellular processes such as cell proliferation and apoptosis. The Raman signatures of these biomolecular changes depend on the different phases of viral infection. Therefore, by using CRM, it is possible to discern details in the progression of EBV infection in nasopharyngeal epithelial cells at the molecular level.

EBV infection is associated with histone bivalent switch modifications in squamous epithelial cells

Epstein-Barr virus (EBV) induces histone modifications to regulate signaling pathways involved in EBV-driven tumorigenesis. To date, the regulatory mechanisms involved are poorly understood. In this study, we show that EBV infection of epithelial cells is associated with aberrant histone modification; specifically, aberrant histone bivalent switches by reducing the transcriptional activation histone mark (H3K4me3) and enhancing the suppressive mark (H3K27me3) at the promoter regions of a panel of DNA damage repair members in immortalized nasopharyngeal epithelial (NPE) cells. Sixteen DNA damage repair family members in base excision repair (BER), homologous recombination, nonhomologous end-joining, and mismatch repair (MMR) pathways showed aberrant histone bivalent switches. Among this panel of DNA repair members, MLH1, involved in MMR, was significantly down-regulated in EBV-infected NPE cells through aberrant histone bivalent switches in a promoter hypermethylation-independent manner. Functionally, expression of MLH1 correlated closely with cisplatin sensitivity both in vitro and in vivo. Moreover, seven BER members with aberrant histone bivalent switches in the EBV-positive NPE cell lines were significantly enriched in pathway analysis in a promoter hypermethylation-independent manner. This observation is further validated by their down-regulation in EBV-infected NPE cells. The in vitro comet and apurinic/apyrimidinic site assays further confirmed that EBV-infected NPE cells showed reduced DNA damage repair responsiveness. These findings suggest the importance of EBV-associated aberrant histone bivalent switch in host cells in subsequent suppression of DNA damage repair genes in a methylation-independent manner.

Defining early events of Epstein-Barr virus (EBV) infection in immortalized nasopharyngeal epithelial cells using cell-free EBV infection.

Epstein-Barr virus (EBV) infection is strongly associated with nasopharyngeal carcinoma, a common cancer in Southeast Asia and certain regions of Africa. However, the dynamics of EBV episome maintenance in infected nasopharyngeal epithelial (NPE) cells remain largely undefined. Here, we report the establishment of a highly efficient cell-free EBV infection method for NPE cells. By using this method, we have defined some of the dynamic events involved in the early stage of EBV infection in NPE cells. We report, for the first time, a rapid loss of EBV copies from infected NPE cells during the first 12-72 h post-infection. The rate of EBV loss slowed at later stages of infection. Live cell imaging revealed that the freshly infected NPE cells were delayed in entry into mitosis compared with uninfected cells. Freshly infected NPE cells transcribed significantly higher levels of lytic EBV genes BZLF1 and BMRF1 yet significantly lower levels of EBER1/2 than stably infected NPE cells. Notably, there were very low or undetectable levels of protein expressions of EBNA1, LMP1, Zta and Rta in freshly infected NPE cells, whereas EBNA1 and LMP1 proteins were readily detected in stable EBV-infected NPE cells. The kinetics of EBV loss and the differential EBV gene expression profiles between freshly and stably infected NPE cells are in line with the suggestion of epigenetic changes in the EBV genome that affect viral gene expression and the adaptation of host cells to EBV infection to maintain persistent EBV infection in NPE cells.

Abstract 3079: Epstein Barr virus-encoded LMP1 reprograms glucose metabolism to enhance cell motility in nasopharyngeal epithelial cell

Abstract How oncogenic virus rewires glucose flux to regulate cell motility is not well-understood. Epstein-Barr virus (EBV) infection of preinvasive nasopharyngeal epithelium is believed to be an essential initiation event during nasopharyngeal carcinoma pathogenesis. Here we demonstrate that EBV-encoded LMP1 enhances glycolysis thereby accelerating cell mobility of nasopharyngeal epithelial (NPE) cells. Activation of IGF1/mTORC2/AKT/PDHE1α signaling which mediates Histone 3 acetylation is involved in cell motility in EBV-infected NPE cells. Blocking the glucose uptake by pharmacological inhibitors effectively suppress glycolysis as well as the cell motility, linking the glucose metabolism to cell movement. We further show that mTORC2/AKT mediated phosphorylation of pyruvate decarboxylase kinase 1 (PDHK1) and its substrate, pyruvate decarboxylase E1α (PDHE1α) component plays a significant role in cell motility. PDHE1α knockdown effectively blocks LMP1-induced cell motility while overexpression of its phosphomimetic mutant S293A but not S293D inhibits LMP1-induced cell motility, supporting the involvement of PDHE1α in enhanced cell motility is depended on Ser293 phosphorylation. Furthermore, PDHE1α translocation into nucleus enhances Histone 3 acetylation and its binding to the promoter region of snail to enhance cell motility. Finally, we find that LMP1 increases the mRNA expression and the secretion of the ligand IGF1, which promotes phosphorylation of IGF1R as the key regulator for LMP1-induced mTORC2/AKT activation. In summary, this study provides evidences of involvement of EBV infection in metabolic reprogramming of NPE cells to promote cell motility involving activation of mTORC2/AKT/PDHE1α. Acknowledgment: This project was supported by funding from the Research Grants Council, Hong Kong: General Research Fund (17120814, 17161116, 17111516, 171110315), Area of Excellence (AoE/M-06/08), Theme-Based Research Scheme (T12-401/13-R), Collaborative Research Fund (Project reference: C7027-16G); Health and Medical Research Fund of Hong Kong (12110782, 13120872, 04151726); and CRCG, University of Hong Kong, Hong Kong. Citation Format: Jun Zhang, Weitao Lin, Chi Man Tsang, Teng Fei Liu, Wing Chong Tang, Yim Ling Yip, Wen Deng, Lin Jia, Sai Wah Tsao. Epstein Barr virus-encoded LMP1 reprograms glucose metabolism to enhance cell motility in nasopharyngeal epithelial cell [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3079.

Abstract 3084: Epstein Barr virus-encoded LMP1 activates the mTORC2 signaling pathway to reprogram glucose metabolism in nasopharyngeal epithelial cell

Abstract Epstein-Barr virus (EBV) infection of preinvasive nasopharyngeal epithelium is believed to be an essential initiation event during nasopharyngeal carcinoma pathogenesis, but the underlying mechanisms are largely undefined. Here we demonstrate that EBV-encoded LMP1 reprograms the glucose metabolism from oxidative phosphorylation to glycolysis of nasopharyngeal epithelial (NPE) is a major process for NPC pathogenesis. RNA-seq analysis indicates that EBV infection reprograms the glucose metabolism from glycolysis and oxidative phosphorylation and enhances the metabolic associated pathways. Our study show EBV encoded LMP1 is important for this event, EBV infection and LMP1 expression enhance the extracellular acidification rate and decrease the oxygen consumption rate in NPE cells. We further show that activation of mTORC2/AKT signaling is involved in this metabolic reprogramming in EBV-infected NPE cells. Genetic or pharmacologic inhibition of the mTORC2/AKT signaling blocks the LMP1-induced glycolysis. In summary, this study provides evidences of involvement of EBV infection in metabolic reprogramming of NPE cells. Acknowledgment: This project was supported by funding from the Research Grants Council, Hong Kong: General Research Fund (17120814, 17161116, 17111516, 171110315), Area of Excellence (AoE/M-06/08), Theme-Based Research Scheme (T12-401/13-R), Collaborative Research Fund (Project reference: C7027-16G); Health and Medical Research Fund of Hong Kong (12110782, 13120872, 04151726); and CRCG, University of Hong Kong, Hong Kong. Citation Format: Jun Zhang, Weitao Lin, Chi-Man Tsang, Teng Fei Liu, W C. Tang, Tim Ling Yip, Wen Deng, Lin Jia, Sai-Wah Tsao. Epstein Barr virus-encoded LMP1 activates the mTORC2 signaling pathway to reprogram glucose metabolism in nasopharyngeal epithelial cell [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3084.

Abstract 2731: Establishment and characterization of immortalized nasopharyngeal epithelial cells with stable infection of Epstein-Barr virus

Abstract Nasopharyngeal carcinoma (NPC), with a remarkably distinctive ethnic and geographic distribution, has the highest incidence among Southern Chinese. Unlike other types of head and neck cancers, a unique feature of NPC is its close association with Epstein-Barr virus (EBV). EBV infection represents an early event during the pathogenesis of NPC. Latent EBV infection is found in every cancer cell of virtually all cases of undifferentiated NPC in endemic regions. Genetic alterations in the premalignant epithelium may support the EBV latency. Although EBV-encoded proteins in its latent infection, including LMP1, LMP2A, etc., have been identified with crucial functions to initiate or promote oncogenesis, to date the exact role of EBV infection in the malignant transformation of nasopharyngeal epithelial (NPE) cells remains unclear. We have previously generated a panel of immortalized NPE cells by ectopic overexpression of hTert (catalytic unit of human telomerase). However, reliable in vitro models of stable EBV infection are also necessary for further elucidating the regulatory network supporting the persistent latency of EBV in NPE cells, and also the potential roles of EBV in the pathogenesis of NPC. In the present study, we established NP361hTert-EBV cells with stable EBV infection via co-culture with Akata B cells harboring EBV, followed by the effective enrichment of EBV-infected cells by FACS sorting. The loss of EBV episome in NPE cells was fast initially upon infection, and relatively stable maintenance of EBV could be achieved after enrichment of EBV-positive cells for three times. Results of western blotting analysis showed that the protein expression level of cyclin D1 was increased in NP361hTert-EBV cells, as compared to the non-infected NP361hTert cells. Meanwhile, we also observed increased expression of phosphorylated protein kinase Akt (Ser473) in NP361hTert-EBV cells, suggesting that the Akt signaling was activated, and such activation might contribute to the persistence of EBV in NP361hTert cells. The stable EBV-infected NPE cells will serve as a powerful in vitro model for further study in elucidating the functional role of EBV in the carcinogenesis of NPC. This work was partly supported by General Research Fund (HKU 779713M, HKU780911M), and the AoE NPC grant (AoE/M-06/08) from Hong Kong Research Grant Council; and Small Project Funding (201309176242) from The University of Hong Kong. Citation Format: Lin Jia, Chi Man Tsang, Yim Ling Yip, Wai Tak Law, Jun Zhang, George SW Tsao. Establishment and characterization of immortalized nasopharyngeal epithelial cells with stable infection of Epstein-Barr virus. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2731. doi:10.1158/1538-7445.AM2015-2731

Role of ATM in the formation of the replication compartment during lytic replication of Epstein-Barr virus in nasopharyngeal epithelial cells.

Epstein-Barr virus (EBV), a type of oncogenic herpesvirus, is associated with human malignancies. Previous studies have shown that lytic reactivation of EBV in latently infected cells induces an ATM-dependent DNA damage response (DDR). The involvement of ATM activation has been implicated in inducing viral lytic gene transcription to promote lytic reactivation. Its contribution to the formation of a replication compartment during lytic reactivation of EBV remains poorly defined. In this study, the role of ATM in viral DNA replication was investigated in EBV-infected nasopharyngeal epithelial cells. We observed that induction of lytic infection of EBV triggers ATM activation and localization of DDR proteins at the viral replication compartments. Suppression of ATM activity using a small interfering RNA (siRNA) approach or a specific chemical inhibitor profoundly suppressed replication of EBV DNA and production of infectious virions in EBV-infected cells induced to undergo lytic reactivation. We further showed that phosphorylation of Sp1 at the serine-101 residue is essential in promoting the accretion of EBV replication proteins at the replication compartment, which is crucial for replication of viral DNA. Knockdown of Sp1 expression by siRNA effectively suppressed the replication of viral DNA and localization of EBV replication proteins to the replication compartments. Our study supports an important role of ATM activation in lytic reactivation of EBV in epithelial cells, and phosphorylation of Sp1 is an essential process downstream of ATM activation involved in the formation of viral replication compartments. Our study revealed an essential role of the ATM-dependent DDR pathway in lytic reactivation of EBV, suggesting a potential antiviral replication strategy using specific DDR inhibitors. Epstein-Barr virus (EBV) is closely associated with human malignancies, including undifferentiated nasopharyngeal carcinoma (NPC), which has a high prevalence in southern China. EBV can establish either latent or lytic infection depending on the cellular context of infected host cells. Recent studies have highlighted the importance of the DNA damage response (DDR), a surveillance mechanism that evolves to maintain genome integrity, in regulating lytic EBV replication. However, the underlying molecular events are largely undefined. ATM is consistently activated in EBV-infected epithelial cells when they are induced to undergo lytic reactivation. Suppression of ATM inhibits replication of viral DNA. Furthermore, we observed that phosphorylation of Sp1 at the serine-101 residue, a downstream event of ATM activation, plays an essential role in the formation of viral replication compartments for replication of virus DNA. Our study provides new insights into the mechanism through which EBV utilizes the host cell machinery to promote replication of viral DNA upon lytic reactivation.

Abstract 2392: The role of ATM in lytic infection of EBV in nasopharyngeal epithelial cells

Abstract Epstein-Barr virus (EBV), a type of oncogenic herpesvirus, is associated with human malignancies. Previous studies have shown that reactivation of EBV in infected cells induces ATM-dependent DNA damage response (DDR). The functional role and involvement of ATM activation during lytic induction remains obscure. In this study, the essential role of ATM for viral DNA replication was examined in EBV-infected nasopharyngeal epithelial cells. Induction of lytic EBV infection triggers ATM activation and localization of DDR proteins at the viral replication compartments. Suppression of ATM activity using siRNA approach or specific chemical inhibitor diminished EBV DNA replication and production of infectious virion in EBV-infected cells induced to undergo lytic infection. Phosphorylation of Sp1 is a downstream event of ATM activation. The phosphorylation of Sp1 at serine 101 residue is crucial in promoting the accretion of EBV replication proteins at the replication compartment to facilitate viral DNA replication. Depletion of Sp1 suppresses viral DNA replication and localization of EBV replication proteins to the replication compartments. Our studies support an important role of ATM activation in lytic infection of EBV. Phosphorylation of Sp1 is an essential process mediating the recruitment of EBV replication protein to replication compartments. Our study highlights the importance of DDR pathway in lytic infection of EBV and suggests the potential application of specific DDR inhibitors to control the EBV replication in infected cells. Funding support: Research Grant Council of Hong Kong (GRF #779312 & 779713; AoE/M-06/08). Note: This abstract was not presented at the meeting. Citation Format: George Sai-Wah Tsao, Pok Man Hau. The role of ATM in lytic infection of EBV in nasopharyngeal epithelial cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2392. doi:10.1158/1538-7445.AM2014-2392

Etiological factors of nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a common disease among southern Chinese. The major etiological factors proposed for NPC pathogenesis include genetic susceptibility, environment factors and EBV infection. In the high risk population, genetic susceptibility to NPC has been mapped to the HLA loci and adjacent genes in MHC region on chromosome 6p21. Consumption of preserved food including salted fish has been implicated in its etiology in earlier studies. Its contribution to pathogenesis of NPC remains to be determined. A decreasing trend of NPC incidence was observed in Hong Kong, Taiwan and Singapore in recent years which may be accounted by a change of dietary habits. A comprehensive epidemiological study will help to elucidate the relative importance of various risk factors in the pathogenesis of NPC. Despite the close association of EBV infection with NPC, the etiological role of EBV in NPC pathogenesis remains enigmatic. EBV infection in primary nasopharyngeal epithelial cells is uncommon and difficult to achieve. EBV does not transform primary nasopharyngeal epithelial cells into proliferative clones, which contrasts greatly with the well-documented ability of EBV to transform and immortalize primary B cells. Genetic alterations identified in premalignant nasopharyngeal epithelium may play crucial roles to support stable EBV infection. Subsequently, latent and lytic EBV gene products may drive clonal expansion and transformation of premalignant nasopharyngeal epithelial cells into cancer cells. Stromal inflammation in nasopharyngeal mucosa is believed to play an important role in modulating the growth and possibly drive the malignant transformation of EBV-infected nasopharyngeal epithelial cells. Furthermore, there are increasing evidences supporting a role of EBV infection to evade host immune surveillance. EBV-infected cells may have selective growth advantages in vivo by acquiring a stress-resistance phenotype. Understanding the etiological factors and pathogenesis of NPC will contribute effectively to the prevention and treatment of this disease.

Id1 interacts and stabilizes the Epstein-Barr virus latent membrane protein 1 (LMP1) in nasopharyngeal epithelial cells.

The EBV-encoded latent membrane protein 1 (LMP1) functions as a constitutive active form of tumor necrosis factor receptor (TNFR) and activates multiple downstream signaling pathways similar to CD40 signaling in a ligand-independent manner. LMP1 expression in EBV-infected cells has been postulated to play an important role in pathogenesis of nasopharyngeal carcinoma. However, variable levels of LMP1 expression were detected in nasopharyngeal carcinoma. At present, the regulation of LMP1 levels in nasopharyngeal carcinoma is poorly understood. Here we show that LMP1 mRNAs are transcribed in an EBV-positive nasopharyngeal carcinoma (NPC) cell line (C666-1) and other EBV-negative nasopharyngeal carcinoma cells stably re-infected with EBV. The protein levels of LMP1 could readily be detected after incubation with proteasome inhibitor, MG132 suggesting that LMP1 protein is rapidly degraded via proteasome-mediated proteolysis. Interestingly, we observed that Id1 overexpression could stabilize LMP1 protein in EBV-infected cells. In contrary, Id1 knockdown significantly reduced LMP1 levels in cells. Co-immunoprecipitation studies revealed that Id1 interacts with LMP1 by binding to the CTAR1 domain of LMP1. N-terminal region of Id1 is required for the interaction with LMP1. Furthermore, binding of Id1 to LMP1 suppressed polyubiquitination of LMP1 and may be involved in stabilization of LMP1 in EBV-infected nasopharyngeal epithelial cells.

Epstein‐Barr virus infection in immortalized nasopharyngeal epithelial cells: Regulation of infection and phenotypic characterization

Epstein-Barr virus (EBV) infection has been postulated to be an early event involved in the pathogenesis of nasopharyngeal carcinomas (NPC). The lack of representative premalignant nasopharyngeal epithelial cell system for EBV infection has hampered research investigation into the regulation and involvement of EBV infection in NPC pathogenesis. We have compared the efficiency of EBV infection in nasopharyngeal epithelial cells with different biological properties including immortalized, primary and cancerous nasopharyngeal epithelial cells. EBV infection could be achieved in all the nasopharyngeal epithelial cells examined with variable infection rate. TGF-beta effectively enhanced EBV infection into nasopharyngeal epithelial cells both in the immortalized and primary nasopharyngeal epithelial cells. Stable infection of EBV was achieved in a telomerase-immortalized nasopharyngeal epithelial cell line, NP460hTert. The expression pattern of EBV-encoded genes and biological properties of this EBV infected cell line on long-term propagation were monitored. The EBV-infected nasopharyngeal epithelial cells acquired anchorage-independent growth and exhibited invasive growth properties on prolonged propagation. A distinguished feature of this EBV-infected nasopharyngeal epithelial cell model was its enhanced ability to survive under growth factor and nutrient starvation. This was evidenced by the suppressed activation of apoptotic markers and sustained activation of pAkt of EBV-infected cells compared to control cells under nutrient starvation. Examination of cytokine profiles of EBV-infected NP460hTert cells to nutrient and growth factor deprivation revealed upregulation of expression of MCP-1 and GRO-alpha. The establishment of a stable EBV infection model of premalignant nasopharyngeal epithelial cells will facilitate research investigation into the pathogenic role of EBV in NPC development.

Abstract 4015: The role of IL-6/STAT3 axis in the transformation of Epstein-Barr Virus (EBV) infected-immortalized nasopharyngeal epithelial cells

Abstract The role of IL-6/STAT3 axis in the transformation of Epstein-Barr Virus (EBV) infected-immortalized nasopharyngeal epithelial cells. Zhang Guitao, Tsang Chi Man, Chen Honglin, Tsao Sai Wah. Nasopharyngeal carcinoma (NPC) is rare throughout most parts of the world but common in certain geographic area, such as Southern China including Hong Kong. The etiology is based on intricate interactions among environmental factors, genetic susceptibility and Epstein-Barr virus (EBV) infection. Elevated antibody titers to EBV antigens are regularly observed in NPC patients. However, little information is available concerning the role of EBV in the early stage of NPC carcinogenesis. Our laboratory has established and characterized immortalized nasopharyngeal epithelial cells lines as premalignant nasopharyngeal cell models to examine for the transformation property of EBV infection in early stage of NPC development. Our results show that EBV infection activates STAT3 in immortalized nasopharyngeal epithelial cells. We had previously reported that the EBV-encoded LMP1 could upregulate IL-6 secretion to activate STAT3 signaling. Interestingly, we observed that activation of STAT3 in EBV-infected immortalized nasopharyngeal epithelial cells is highly susceptible to the induction by inflammatory cytokines, notably IL-6. Using quantitative real-time PCR, up-regulation of LMP1 was observed after IL-6 treatment on a time course dependent manner. An analysis of IL-6 receptor (IL-6R) indicated that EBV-infected nasopharyngeal epithelial cells have elevated level of IL-6R expression compared with uninfected cells. Activation of STAT3 signaling in immortalized nasopharyngeal epithelial cells by expressing a flag-tagged constitutively active STAT3-C confers transformed properties to cells. Our results support a model that EBV infection may predispose the aberrant STAT3 signaling for inflammatory cytokines involving the activation of LMP1/IL-6/STAT3 axis in premalignant nasopharyngeal epithelial cells. Enhanced STAT3 activation in EBV-infected epithelial cells by stromal inflammatory cytokines could result in irregular-gene expressions and cell signaling essential for malignant transformation, which may represent a crucial function of EBV infection in the development of nasopharyngeal carcinoma. (This project is supported by The Research Grant Council (Hong Kong) and Area of Excellence on Nasopharyngeal Carcinoma Research Center (Hong Kong)). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4015.

Abstract 2460: Epstein-Barr virus infection confer stress-resistant property in immortalized nasopharyngeal epithelial cells

Abstract Epstein-Barr virus (EBV) infection has been postulated to be an early event involved in the pathogenesis of NPC. The lack of representative premalignant nasopharyngeal epithelial cell system for EBV infection has hampered research investigation into the regulation and involvement of EBV infection in NPC pathogenesis. We have compared the efficiency of EBV infection in nasopharyngeal epithelial cells with different biological properties including immortalized, primary and cancerous nasopharyngeal epithelial cells. EBV infection could be achieved in all the nasopharyngeal epithelial cells examined with variable infection rate. TGF-β effectively enhanced EBV infection into nasopharyngeal epithelial cells both in the immortalized and primary nasopharyngeal epithelial cells. Stable infection of EBV was achieved in a telomerase-immortalized nasopharyngeal epithelial cell line, NP460hTert. The expression pattern of EBV-encoded genes and biological properties of this EBV infected cell line upon long term propagation were monitored. The EBV-infected nasopharyngeal epithelial cells acquired anchorage independent growth in soft-agar and exhibited invasive growth properties upon prolonged propagation. A distinguish feature of this EBV-infected nasopharyngeal epithelial cell model was its enhanced ability to survive under growth factor and nutrient starvation. This was evidenced by the suppressed activation of apoptotic markers and sustained activation of pAkt of EBV-infected cells compared to control cells under nutrient starvation. Examination of cytokine profiles of EBV-infected NP460hTert cells to nutrient and growth factor deprivation revealed upregulation expression of MCP-1 and GRO-α. The establishment of a stable EBV infection model of premalignant nasopharyngeal epithelial cells will facilitate research investigation into the pathogenic role of EBV in NPC development. Acknowlegement: The authors wish to acknowlege the funding support from the Research Grant Council (Hong Kong) and the Area of Excellence on Nasopharyangeal Carcinoma Research Center (Hong Kong). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2460.