CARCINOGEN ENHANCEMENT OF EBV INDUCED TRANSFORMATION

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We have shown that chemical and physical carcinogens can enhance peripheral blood lymphocyte (PBL) transformation by Epstein-Barr virus (EBV). Recently, using cloned EBV DNA fragments, Eco R1 J and D, which are transcribed in cells latently infected with EBV, we have demonstrated that carcinogen-induced enhancement of PBL transformation by EBV correlates with EBV genome amplification and association with high-molecule-weight lymphoblastoid cell line (LCL) DNA. These latter studies are in agreement with the findings that treatment of virus-producing cells P3HR-1 with N-methyl-N' -nitroso-nitrosoguanidine (MNNG) resulted in a 3-fold increase in EBV genome copies per cell and that pretreatment of Raji cells with MNNG followed by superinfection with P3HR-1 virus resulted in a 35% enhancement of EBV-DNA replication. Singularly, each of these observations strongly suggests that synergism between occupational-environmental factors and EBV could contribute to EBV-associated malignancy. Collectively, these observations present a compelling argument for further investigations into the mechanism by which carcinogens enhance EBV-induced lymphocyte transformation and if this phenomenon contributes to malignancy following EBV infection. Numerous LCLs have been established from EBV-infected control and carcinogen-treated PBLs, the latter of which have amplified EBV sequences and enhanced growth and cloning efficiencies. We propose that by using these LCLs to examine the organization of the EBV genome and its interaction with the host cell genome by nucleic acid hybridization, we can demonstrate correlations between certain aspects of these parameters and enhanced PBL transformation. Specifically, our aims are 1) to determine the methylation patterns of the EBV genomes in LCLs derived from control and carcinogen-treated PBLs; 2) to determine whether EBV sequences are more frequently found integrated into host cell DNA in LCLs derived from carcinogen-treated PBLs; and 3) if so, to determine whether carcinogen-EBV synergism during lymphocyte transformation results in oncogene (c-myc or Blym) activation. These experiments should provide information central to our understanding of how the EBV initiates malignant transformation.