Antagonistic effects of C-MYC and Epstein-Barr virus latent genes on the phenotype of human B cells

Epstein-Barr virus (EBV) immortalized cells and Burkitt lymphoma cells have a completely different growth pattern and phenotype. EBV immortalized cell s express a set of 11 viral genes to accommodate B cell activation and prol iferation, whereas EBV-positive Burkitt lymphoma cells highly express the c -myc oncogene that is activated through translocation into I of the immunog lobulin loci and EBNA I as the only viral protein. We have developed a prim ary human B cell line conditionally immortalized by Epstein-Barr virus in w hich the viral gene program responsible for the induction of proliferation can be switched on and off by the addition or withdrawal of estrogen (cell line EREB2-5). Starting from this cell line we have generated 2 daughter ce ll lines that proliferate in a c-myc dependent fashion, I with a highly act ive exogenous c-myc gene (cell line A1) and I with a regulatable c-myc gene that can be switched on by withdrawal and switched off by addition of tetr acycline (cell line P493-6). The comparison of the 3 cell lines has allowed us to dissect the contribution of c-myc and EBV genes to the regulation of the growth pattern and expression of cell surface molecules. We show that MYC and EBNA2 (and their respective target genes) have opposing effects on the expression of several surface markers involved in B cell activation. We show that MYC contributes to the phenotype of Burkitt lymphoma cells by up regulating CD10 and CD38 and downregulating activation markers. The phenoty pe of the cells is determined on one hand by the absence of the viral gene products EBNA2 and LMP I that mediate the phenotype of activated lymphoblas ts and to a lesser extent by an active contribution of the c-myc gene. (C) 2001 Wilely-Liss. Inc.