The PTEN-AKT-mTOR/RICTOR Pathway in Nasal Natural Killer Cell Lymphoma Is Activated by miR-494-3p via PTEN But Inhibited by miR-142-3p via RICTOR

Nasal natural killer (NK) cell lymphoma (NNL) is an Epstein-Barr virus-associated lymphoma of cytotoxic NK cell origin. The Epstein-Barr virus-encoded miR-BART20-5p inhibits T-bet (TBX21), the master transcription factor of cytotoxic NK cells. To further explore the roles of miRNAs in NNLs, we measured the miRNA expression profiles of 36 NNLs. miR-21, miR-142-3p, miR-126, miR-451, and miR-494-3p were the top five miRNAs with the highest expression levels. By using pathway analysis, we identified associations between all of the five miRNAs with the PTEN-AKT-mTOR pathway, in which PTEN suppresses the oncogenic AKT, and mTOR mediates the oncogenic effects of AKT. YT and NK92 cells derived from NK cell lymphomas were used. miR-494-3p inhibited PTEN with secondary activation of AKT in NK92 cells, and miR-142-3p inhibited RICTOR, a key component of the mTOR complex, with secondary suppression of AKT in YT cells. Significantly, T-bet inhibited the PTEN-AKT-mTOR/RICTOR pathway through induction of PTEN and suppression of RICTOR. Therefore, a molecular circuit of T-bet, PTEN, AKT, and RICTOR is regulated by miR-BART20-5p, miR-494-3p, and miR-142-3p. This circuit is involved in the pathogenesis of NNL. Hence, antagomirs to miR-BART20-5p or miR-494-3p, miR-142-3p mimics, or AKT inhibitors may be useful in NNL therapy.