The goal of this research is to determine the role of EBV in the etiology of nasopharyngeal carcinoma (NPC), an epithelial malignancy that develops with high incidence in Southern China, Northern Africa, and among Eskimos. The viral genes that are expressed in NPC include the latent membrane proteins, LMP1 and 2, and a new family of mRNAs, transcribed through the BamHI A fragment. Sequence analysis of the intricately spliced cDNAs representing the BamHI A transcripts has revealed four previously unidentified open reading frames. To determine how EBV affects epithelial cell growth, the viral proteins will be expressed in epithelial cell lines and in primary keratinocytes. Cell lines expressing LMP1 will be analyzed to test the hypothesis that LMP1 alters epithelial cell growth through the induction of expression of the epidermal growth factor receptor and by inhibiting p53-mediated apoptosis. The NFKB complexes induced by LMP1 and the mechanism of activation of NFKB will also be determined in epithelial cell lines. Cell lines expressing LMP2 will be analyzed to determine whether LMP2 blocks differentiation induced by extracellular Ca++ and to identify a possible interaction with a cellular tyrosine kinase. The ability of EBV to transform epithelial cells will be determined in primary epithelial cells or cell lines that are stably infected with EBV that has been genetically altered and contains a selectable marker. Genetically altered EBV lacking specific genes will be tested in this system. The BamHI A open reading frames that are formed by splicing will be translated in vivo to screen human sera for reactivity to the putative proteins. Glutathionein transferase fusion proteins will be synthesized to produce monospecific antisera to identify the proteins in transfected cell lines and in NPC tumor tissues. The proteins will be tested for interactions with cellular proteins and for transactivation of the LMP1 promoter. To investigate the high incidence in specific populations and to explore a possible genetic contribution to NPC, additional NPC samples will be obtained from Chinese, Caucasian, Black, and possibly Inuit Americans. When possible the samples will be obtained viably for transplantation into SCID mice. Additional NPC samples and any samples passaged in SCID mice will be used for identification of viral proteins and interactive cellular proteins and characterization of the EBV strain. To test the hypothesis that loss of heterozygosity on chromosomes 3 or 9 contributes to the development of NPC, tumor tissue and normal tissue from patients from Chinese, Mediterranean, and American populations will be analyzed for LOH in these regions.
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