Epstein-Barr virus (EBV) is a cancer-associated virus that infects more than 90% of adults. Unfortunately, many EBV-driven malignancies, including numerous B cell lymphomas, are highly aggressive and lack acceptable therapeutic outcomes. The concentrations of extracellular purines, namely, ATP and adenosine, are highly dysregulated in the tumor microenvironment and significantly impact the degree of immune responses to the tumor. Additionally, many tumor cells adapt to this dysregulation by overexpressing one or more ectonucleotidases, enzymes that degrade extracellular nucleotides to nucleosides. The degradation of immunostimulatory extracellular ATP to immunosuppressive adenosine through ectonucleotidase activity is one example of tumor cell exploitation of the purinergic signaling pathway. As such, preclinical studies targeting the purinergic signaling pathway have found it to be a promising immunotherapeutic target for the treatment of solid tumors; however, the extent to which purinergic signaling impacts the development and survival of EBV+ B cell lymphoma remains unstudied. Here, we demonstrate robust ectonucleotidase expression on multiple types of EBV-positive B cell non-Hodgkin lymphoma (NHL). Furthermore, the presence of high concentrations of extracellular ATP resulted in the expression of lytic viral proteins and exhibited cytotoxicity toward EBV+ B cell lines, particularly when CD39 was inhibited. Inhibition of CD39 also significantly prolonged survival in an aggressive cord blood humanized mouse model of EBV-driven lymphomagenesis and was correlated with an enhanced inflammatory immune response and reduced tumor burden. Taken together, these data suggest that EBV+ B cell lymphomas exploit ectonucleotidase activity to circumvent ATP-mediated inflammation and cell death. IMPORTANCE EBV is a ubiquitous pathogen responsible for significant global lymphoma burden, including Hodgkin lymphoma, numerous non-Hodgkin B, T, and NK cell lymphomas, and lymphoproliferative disorders. EBV is also associated with epithelial cancers and autoimmune diseases, such as multiple sclerosis. Many of these diseases are highly aggressive and exhibit poor outcomes. As such, new treatments for EBV-driven cancers have the potential to benefit a large number of patients. We use in vitro and in vivo models to demonstrate the therapeutic potential of targeting the purinergic signaling pathway in the context of EBV-driven B cell lymphoma. These findings lend credence to the manipulation of purinergic signaling as a viable therapeutic approach to EBV+ malignancies and support the feasibility of immunotherapeutic treatments for viral lymphoma.
Keywords: EBV; ectonucleotidase; immune evasion; lymphoma.