Theodore E. Woodward Award: development of novel, EBV-targeted therapies for EBV-positive tumors

The near universal presence of EBV in certain tumors suggests that new EBV-based therapies could be developed for these malignancies. We have explored one EBV-based therapy that involves the purposeful induction of lytic EBV infection in tumors. Induction of lytic EBV infection in tumors activates expression of EBV-encoded kinases that convert the prodrug, ganciclovir, to its active cytotoxic form. In mouse models for EBV-positive tumors, the combination of lytic-inducing chemotherapy and ganciclovir is much more effective than either agent alone for treating tumors. Another potential EBV-based target is the cellular protein, CD70. EBV-positive tumors commonly express CD70, while CD70 expression in normal cells is restricted to a few highly activated B cells and T cells. Anti-CD70 monoclonal antibody inhibits the growth of CD70-positive (but not CD70-negative) Burkitt's lymphomas in SCID mice. Finally, while completely lytic EBV infection is clearly incompatible with tumor cell growth, we recently discovered that small numbers of lytically-infected cells actually promote the growth of EBV-immortalized lymphocytes in SCID mice, through the release of paracrine growth factors as well as angiogenic factors. Thus, agents that prevent the earliest stage of lytic EBV infection (such as fatty acid synthase inhibitors), rather than the later stage of viral replication, might also be useful in the treatment of early-stage EBV-positive tumors.