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Aggressive Mature Natural Killer Cell Neoplasms: From EBV-Infection to Disease Etiopathogeny

Margarida Lima

Mature Natural Killer (NK) cell neoplasms are rare tumors with higher prevalence in Asia, Central and South America, which are related to Epstein Barr Virus (EBV) infection. Nature killer /T cell lymphoma, nasal type, presents as a localized or generalized destructive tumor, affecting the nose, the upper aero digestive tract or any organ or tissue, whereas aggressive NK-cell leukemia manifests as a systemic disease that preferentially affects the bone marrow, the spleen and the liver, and rapidly evolve to multiorgan failure resulting in death. Both NK-cell neoplasms arise as a consequence of the inability of the immune system to control EBV infection and of the transforming potential of multiple EBV gene products. Chronic active EBV infection and EBV-related lymphoproliferative disorders of NK-cells are predisposing conditions. The tumor NK-cells do express an EBV infection type II latency pattern, specific EBV-encoded latent membrane proteins and early region EBV RNAs being detected on lymphoma cells. The EBV encoded proteins and non-coding EBV RNAs and micro-RNAs expressed on the infected cells are involved in immune deregulation and play a crucial role in cell transformation and oncogenesis. This review addresses the mechanisms used by EBV to infect the cells and to evade the immune-surveillance as well as to induce cell survival and transformation, and characterizes the spectrum of the clinical manifestations associated with chronic EBV-infection and related T-and NK-lymphoproliferative disorders. Improving the knowledge in this subject will help to develop new therapeutic approaches for chronic EBV-infection and even prevention strategies for the aggressive NK-cell malignancies.