This project aims at understanding how Epstein-Barr virus immortalized cells die when deprived of autocrine growth factors. Cell death is known to occur by two distinct pathways, necrosis and apoptosis. We have found that starved EBV-immortalized cells die by programmed cell death and exhibit all the features of death by apoptosis, including nuclear condensation and fragmentation as well as DNA lattering in distinct nucleosomal fragments. We have also found that unlike normal peripheral blood B cells which rapidly downregulate c-myc expression and arrest growth in G0/G1 after growth factor deprivation, EBV-immortalized B cells continue to cycle and do not downregulate c-myc expression. These cells also fail to change levels of expression of p53 and BCL2. Together, these findings suggested that c-myc expression is deregulated in B cells immortalized by EBV. This conclusion was further supported by the observation that treatment of starved EBV-immortalized cells with antisense oligonucleotides to c-Myc, but not with control oligonucleotides, delays cell death by apoptosis. Post-transplant lymproproliferative disease (PTLD) represents a common and often lethal complication of immunosuppression associated with bone marrow and solid organ transplantation. PTLD represents the outgrowth in vivo of EBV-infected cells that are no longer under T cell surveillance. The present studies investigate the mechanisms and circumstances leading to death of the EBV-infected cells, a very desirable outcome in the context of EBV-induced malignancies. We showed that IL-6 and/or lactic acid prevent death of EBV-infected cells, induced by a variety of mechanisms such as growth factor starvation, irradiation or treatment with cytotoxic drugs. Thus, these studies provide a clear understanding of safety and efficacy issues associated with administration of IL-6 and or lactic acid to severely immunosuppresed individuals.
