Telomerase Activity Impacts on Epstein-Barr Virus Infection of AGS Cells

Abstract

The Epstein-Barr virus (EBV) is transmitted from host-to-host via saliva and is associated with epithelial malignancies including nasopharyngeal carcinoma (NPC) and some forms of gastric carcinoma (GC). Nevertheless, EBV does not transform epithelial cells in vitro where it is rapidly lost from infected primary epithelial cells or epithelial tumor cells. Long-term infection by EBV, however, can be established in hTERT-immortalized nasopharyngeal epithelial cells. Here, we hypothesized that increased telomerase activity in epithelial cells enhances their susceptibility to infection by EBV. Using HONE-1, AGS and HEK293 cells we generated epithelial model cell lines with increased or suppressed telomerase activity by stable ectopic expression of hTERT or of a catalytically inactive, dominant negative hTERT mutant. Infection experiments with recombinant prototypic EBV (rB95.8), recombinant NPC EBV (rM81) with increased epithelial cell tropism compared to B95.8, or recombinant B95.8 EBV with BZLF1-knockout that is not able to undergo lytic replication, revealed that infection frequencies positively correlate with telomerase activity in AGS cells but also partly depend on the cellular background. AGS cells with increased telomerase activity showed increased expression mainly of latent EBV genes, suggesting that increased telomerase activity directly acts on the EBV infection of epithelial cells by facilitating latent EBV gene expression early upon virus inoculation. Thus, our results indicate that infection of epithelial cells by EBV is a very selective process involving, among others, telomerase activity and cellular background to allow for optimized host-to-host transmission via saliva.

Epstein‐Barr virus mRNA profiles and viral DNA methylation status in nasopharyngeal brushings from nasopharyngeal carcinoma patients reflect tumor origin

“…Previously we and others showed that the molecular diversity of EBV‐reactive IgG and IgA responses varies greatly among NPC patients, reflecting heterogeneous EBV antigen exposure during NPC development . We suggest that VCA‐IgA reactivity reflects loco‐regional virus replication events outside the initiating tumor mass, potentially contributing to tumor initiation by providing infectious EBV to infect susceptible cells capable of maintaining the viral genome, as recently identified . Recently, the combination of EBV IgA serology with EBV‐DNA load analysis in NP brushings has been proposed as preferred method for population screening programs to identify early stage NPC …”

Expression of α-fetoprotein in gastric cancer AGS cells contributes to invasion and metastasis by influencing anoikis sensitivity

“…This cell line was derived from fragments of a tumor resected from a 54-year-old female patient who had received no prior therapy in 1979 (13). As a common GC cell line, AGS has been used widely in GC-related studies (14)(15)(16). The expression of AFP in AGS was reported by Chen et al in 2003 (17); however, the biological functions of AFP in AGS, particularly in invasion and metastasis remain unknown.…”

Extra-telomeric functions of telomerase in the pathogenesis of Epstein-Barr virus-driven B-cell malignancies and potential therapeutic implications

“…More recently, the impact of TERT on EBV infection and viral gene expression has also been studied in epithelial cells [ 49 ]. Gastric carcinoma AGS cells with high telomerase activity show increased expression of latent EBV genes, indicating that telomerase directly contributes toward favoring the latency program in epithelial EBV-infected cells [ 49 ]. Thus, the ability of TERT to favor the latency program in both B lymphocytes and epithelial EBV-infected cells further supports the crucial role of telomerase in EBV-driven malignancies.…”