Role of Latent Membrane Protein 1 of Epstein-Barr Virus---Its Mechanism in the Pathogenesis of Nasopharyngeal Carcinoma

Serological and molecular evidence strongly suggests that Epstein-Barr virus(EBV) plays an important role in the pathogenesis of nasopharyngeal carcinoma(NPC). However, it is not understood by which mechanism EBV contributes to the development of NPC. Therefore, more information, particularly on the interaction between EBV gene products with cellular factors, is required to conclusively assess the significance of the presently available data for the pathogenesis of NPC. Previously we have identified a strain of EBV predominantly present in NPC tumor biopsies in Taiwan. Structural differences between B-cell-derived LMP1 gene(BLMP 1) and NPC-derived LMP 1(NLMP 1)gene have been described and it has been suggested that the NLMP 1 variant may be more oncogenic. Our recent studies indicated that a recurrent 30-bp deletion found in the 3' end of the gene plays an important role in the transformation of BALB/c3T3 cells and induction of tumors in nude mice. LMP1 is a transmembrane protein that has been reported that has been reported to interact with the tumor necrosisi factor receptor(TNFR)-associated protein. This association has been implied as the possible involvement of LMP1 in signal transduction pathway similar to TNFR family. Our preliminary data using two LMP1(B and N) genes and their chimeric constructs showed that the NF-KB activity was activated specifically by LMP1 regardless of its origin. Thus, the activation of NF-KB activity is independent of the transformation ability of these two proteins. In this 3 year proposal, we plan to ask which cellular factor interacts with the NLMP1, but not with the BLMP1. To do so, we will take advantage of the yeast two-hybrid system, using LMP1 constructs as the DNA binding domain and cDNA libraries derived from BALB/c3T3 cells and NPC biopsies as the activation domain. By this way, we hope to identify the cellular factor that is potentially important for NLMP1 transforming ability. The biological function of this cellular factor will be further evaluated in the knockout mice study. To further examine the role of NLMP1 or the effect of 30-bp deletion in cellualr transformation, we plan to establish a transgenic mouse model that will express either BLMP1 or NLMP1 gene. The genomic constructs of both variant genes which were used for our BALB/c3T3 transformation study will be used to generate transgenic mice. These transgenic mice will be able to tell us if N-LMP1 behaves differently from B-LMP1 in this in vivo model. The cellular factor identified in the yeast two-hybrid system will be used to examine its expression in the tiuuse of transgenic mice. Furthermore, the knockout mice with defects in the cellular factor gene described above will also be used to generate NLMP 1 transgenic mice. The above experiments are very important for understanding of the mechanism of LMP1 biological function, specifically, transformation. The transgenic mice will provide us with an in vivo model for studying the role of NLMP1 in the pathogdnesis of NPC.

Project ID:PG9103-0533
External Project ID:NHRI-EX91-8703SL