Establishment of stable infection of Epstein-Barr Virus in premalignant nasopharyngeal epithelial cells

Abstract

Epstein Barr virus (EBV) infection is closely associated with nasopharyngeal carcinoma (NPC) and has been postulated as an etiological factor for the development of nasopharyngeal carcinoma. EBV infection was shown to be an early event in the pathogenesis of NPC. The lack of representative premalignant nasopharyngeal epithelial cell system for EBV infection has hampered research to elucidate events regulating EBV infection and the role of EBV infection in NPC pathogenesis. Recently, we have established and characterized a telomerase-immortalized nasopharyngeal epithelial cell, NP460hTert. Here, we reported the successful establishment of stable EBV infection in this premalignant nasopharyngeal epithelial cell system upon long term propagation NP460hTert-EBV expressed latent genes of EBV including EBER, EBNA1 and LMP1. The EBV infected cells were also responsive to lytic induction by TPA, with the expression of BZLF1 and BMRF1 being effectively induced. However, the lytic infection of EBV infection in nasopharyngeal epithelial cells is abortive in nature as no infectious EBV particles could be detected in the culture supernatant. The EBV infected premalignant nasopharyngeal epithelial cells exhibited some transformed properties including invasive growth property in 3-dimensional collagen gel and anchorage independent growth in soft agar. STAT3 was activated in the EBV-infected nasopharyngeal epithelial cells together with upregulated cytokines which may support cell growth and survival. The EBV-infected nasopharyngeal epithelial cells remain non-tumorigenic in athymic nude mice indicating additional events are required to complete the malignant transformation of these cells.