Phenotypic alterations induced by the Hong Kong‐prevalent Epstein‐Barr virus‐encoded LMP1 variant (2117‐LMP1) in nasopharyngeal epithelial cells

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Abstract
Epstein-Barr virus (EBV) is closely associated with nasopharyngeal carcinoma (NPC), a common cancer in Hong Kong. The EBV-encoded LMP1 protein is believed to play an important role in cell transformation. We have previously identified a prevalent LMP1 variant (2117-LMP1) that is expressed in 86% of primary NPC in Hong Kong. In this study, the biologic phenotypes induced by 2117-LMP1 were compared with those of the prototypic B95.8-LMP1 in an immortalized nasopharyngeal epithelial cell line, NP69. The 2117-LMP1 could induce cell proliferation and resistance to apoptosis induced by growth factor deprivation. Expression of 2117-LMP1 also suppressed expression of p16, p21 and Bax but induced expression of CDK2 and A20. Compared with B95.8-LMP1, 2117-LMP1 could induce a higher migration ability in NP69 cells but was less efficient in inducing morphologic changes, anchorage-independent growth and cell invasion. Relatively weaker ability of 2117-LMP1 than B95.8-LMP1 in upregulation of vimentin, VEGF and MMP9 as well as in downregulation of E-cadherin was observed. 2117-LMP1 could activate higher level of NF-κB activity in HEK 293 cells than B95.8-LMP1. The present study supports a role of 2117-LMP1 in NPC development by enhancing cell proliferation, cell death inhibition and migration in premalignant nasopharyngeal epithelial cells. Furthermore, our study reveals significant functional differences between 2117-LMP1 and the prototypic B95.8-LMP1. Our results provide insights into the pathologic significance of this prevalent LMP1 variant, 2117-LMP1, in the development of NPC in the Hong Kong population.