Identification of functional differences between prototype Epstein-Barr virus-encoded LMP1 and a nasopharyngeal carcinoma-derived LMP1 in human epithelial cells

The contribution of Epstein-Barr Virus (EBV) strain Variation to the pathog enesis of virus-associated tumours remains unknown. Given the central role of LMP1 in EBV-induced transformation, much interest has focused on the inf luence of LMP1 sequence variation on the signaling pathways and multiple do wnstream phenotypic consequences of LMP1 expression. The identification of LMP1 variants with a common 10-amino-acid deletion and additional point mut ations (typified by the CAO-LMP1 isolate) in EBV strains associated with na sopharyngeal carcinoma prompted us to examine the effect of stable prototyp e B95.8-LMP1 and CAO-LMP1 expression on the phenotype and differentiation o f SCC12F human epithelial cells. Both forms of LMP1 were able to induce exp ression of the antiapoptotic A20 protein and provide protection from tumour necrosis factor-ct-induced cytotoxicity. Although B95.8-LMP1 induced growt h inhibition, expression of certain cell surface molecules (CD40, CD44, and CD54), and secretion of interleukin-6 and -8 in SCC12F cells, stable CAO-L MP1 expression failed to elicit these effects. Furthermore, B95.8-LMP1, but not CAO-LMP1, induced alterations in cell morphology and blacked epithelia l cell differentiation. Both B95.8-LMP1 and CAO-LMP1 induced similar levels of nuclear factor-kappa B activation, but the ability of CAO-LMP1 to activ ate the AP-1 pathway was relatively impaired. These data highlight signific ant functional differences between the prototype B95.8-LMP1 and the CAO-LMP 1 variant when stably expressed in human epithelial cells and suggest that continued analysis of LMP1 variants will help to further dissect the signal ing pathways activated by LMP1 as well as provide insights into the contrib ution of LMP1 sequence variation to the pathogenesis of EBV-associated tumo urs. (C) 2000 Academic Press.