Impact of microRNA-29b on natural killer cells in T-cell acute lymphoblastic leukemia

Natural killer (NK)-based immunotherapeutic strategies are showing promise in the clinic, particularly against acute myeloid leukemia (AML). Similar treatments for T-cell acute lymphoblastic leukemia (T-ALL) have been less successful, which is due to the higher resistance of T-ALL blasts to the cytotoxic function of NK cells. Herein, microRNA-29b (miR-29b) upregulation was identified in NK cells in both neurogenic locus notch homolog protein 1 (Notch1)-T-ALL mice and patients with T-ALL. Furthermore, miR-29b expression levels were downregulated in T-ALL blast cells. In addition, there was a selective downregulation of an immature subset of NK cells, as well as a reduction in interferon γ (IFNγ) production and natural killer receptor group 2, member D (NKG2D) expression level by NK cells in Notch1-T-ALL mice and patients with T-ALL. Furthermore, when miR-29b knock-out NK cells were adoptively transfused into Notch1-T-ALL mice, partial restoration of IFNγ production and NKG2D expression was observed in NK cells, accompanied by retarded ALL progression and improved survival time. These results implied that T-ALL blast immune evasion occurred via miR-29b-mediated dysregulation in NK cells in the T-ALL microenvironment.