Epstein-Barr virus is an oncogenic herpes virus associated with lymphoma in immune-compromised individuals. In vitro EBV transforms primary B cells into indefinitely proliferating lymphoblastoid cell lines (LCLs) with an efficiency of less than 10%. While nearly all infected cells express viral latent genes and begin to proliferate, a block to long term proliferation exists in the majority of these cells. Recent evidence suggests that activated oncogenes induce a tumor suppressive DNA damage response (DDR). In this application, we aim to understand the role of the DDR as an innate suppressor of EBV-mediated transformation and the mechanisms by which EBV overcomes this response. It is our working hypothesis that the initial EBV latent gene expression program upon primary B cell infection depends on high-level EBNA2 activity, which drives an initial hyper-proliferative state that provokes the host DDR. Long-term outgrowth depends on EBNA3C mitigating the DDR through attenuation of EBNA2 activity and the B cell proliferation rate. The rationale for the proposed research is that determining the essential effectors of the DDR suppressing EBV transformation is expected to lead to candidate targets for therapeutic intervention in EBV-associated malignancies. Further, delineating the role of viral proteins in mitigating the DDR will provide insight into the mechanism of EBV-induced oncogenesis. We plan to test our hypothesis and complete the objectives outlined in this application through three specific aims. First, we will determine the critical effectors of the ATM/Chk2 dependent DDR detected early after EBV infection. Second, we will determine the molecular basis for the DDR-correlated change in EBNA3C protein isoform during early initial cell divisions following EBV infection. Third, we will define the genetic requirements of EBNA3C in attenuating the EBV-induced DDR in early infection. The proposed research is significant because it aims to determine a critical mechanism by which EBV immortalization is suppressed by the host and how the virus overcomes this innate tumor suppressor pathway. This knowledge will be informative towards identifying novel therapeutic targets for EBV-associated malignancy. For example, a novel therapeutic approach could be focused on accentuation of such tumor suppressor effectors to block proliferation of EBV- driven tumors.
This project is particularly innovative because it is one of the first to address the role of the host innate tumor suppressor response in limiting EBV transformation. Our experiments will largely be performed in the physiological setting of primary human B cell infection. While challenging, this approach is expected to provide fundamental clues regarding the earliest steps in virus-induced lymphomagenesis. The ultimate application of our findings will be the identification of novel therapeutic targets that limit EBV-associated malignancies.
|McFadden, Karyn; Hafez, Amy Y; Kishton, Rigel et al. (2016) Metabolic stress is a barrier to Epstein-Barr virus-mediated B-cell immortalization. Proc Natl Acad Sci U S A 113:E782-90|
|Price, Alexander M; Luftig, Micah A (2015) To be or not IIb: a multi-step process for Epstein-Barr virus latency establishment and consequences for B cell tumorigenesis. PLoS Pathog 11:e1004656|
|Luftig, Micah A (2014) Viruses and the DNA Damage Response: Activation and Antagonism. Annu Rev Virol 1:605-25|
|Price, Alexander M; Luftig, Micah A (2014) Dynamic Epstein-Barr virus gene expression on the path to B-cell transformation. Adv Virus Res 88:279-313|
|Nikitin, Pavel A; Price, Alexander M; McFadden, Karyn et al. (2014) Mitogen-induced B-cell proliferation activates Chk2-dependent G1/S cell cycle arrest. PLoS One 9:e87299|
|Forte, Eleonora; Luftig, Micah A (2013) Use of viral systems to study miRNA-mediated regulation of gene expression in human cells. Methods Mol Biol 936:143-56|
|Homa, Nicholas J; Salinas, Raul; Forte, Eleonora et al. (2013) Epstein-Barr virus induces global changes in cellular mRNA isoform usage that are important for the maintenance of latency. J Virol 87:12291-301|
|Zhang, Jenny; Grubor, Vladimir; Love, Cassandra L et al. (2013) Genetic heterogeneity of diffuse large B-cell lymphoma. Proc Natl Acad Sci U S A 110:1398-403|
|Luftig, Micah (2013) Heavy LIFting: tumor promotion and radioresistance in NPC. J Clin Invest 123:4999-5001|
|McFadden, Karyn; Luftig, Micah A (2013) Interplay between DNA tumor viruses and the host DNA damage response. Curr Top Microbiol Immunol 371:229-57|
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