Epstein-Barr Virus-Encoded miR-BART20-5p Inhibits T-bet Translation with Secondary Suppression of p53 in Invasive Nasal NK/T-Cell Lymphoma

Nasal NK/T-cell lymphoma (NNL) is an Epstein-Barr virus (EBV)-associated lymphoma derived from cytotoxic NK or T cells of the nasal mucosa. NNLs are noninvasive in the earliest stage, and become invasive with disease progression. The EBV encodes at least 44 miRNAs, whose functions in the pathogenesis of NNL are mostly unknown. We evaluated the levels of 39 EBV-encoded miRNAs with quantitative real-time RT-PCR in a series of 20 noninvasive NNLs and 20 invasive NNLs. miR-BART20-5p was associated most strongly with invasion (P ≤ 0.001), and lack of T-bet, the master transcription factor for cytotoxic NK cells. However, we identified T-bet (official symbol, TBX21) transcripts in T-bet-negative NNLs, implying a block in the translation of T-bet by miR-BART20-5p. In co-transfection experiments, miR-BART20-5p inhibited T-bet translation in both non-Hodgkin and Hodgkin lymphoma cell lines. Endogenous mir-BART20-5p also inhibited translation of T-bet in EBV-infected YT lymphoma cells of NK-cell origin. Induction of T-bet in YT cells up-regulated p53, leading to increased sensitivity in response to doxorubicin. Finally, YT cells transplanted into severe combined immunodeficiency mice had an invasive behavior. Taken together, we conclude that EBV-encoded miR-BART20-5p inhibits T-bet translation with secondary suppression of p53 in invasive nasal NK/T-cell lymphoma. An antagomir to miR-BART20-5p might be an effective therapeutic agent through induction of T-bet and p53.