Decitabine enhances targeting of AML cells by CD34 + progenitor-derived NK cells in NOD/SCID/IL2Rg null mice.

Combining natural killer (NK) cell adoptive transfer with hypomethylating agents (HMAs) is an attractive therapeutic approach for patients with acute myeloid leukemia (AML). However, data regarding the impact of HMAs on NK cell functionality are mostly derived from in vitro studies with high nonclinical relevant drug concentrations. In the present study, we report a comparative study of azacitidine (AZA) and decitabine (DAC) in combination with allogeneic NK cells generated from CD34+ hematopoietic stem and progenitor cells (HSPC-NK cells) in in vitro and in vivo AML models. In vitro, low-dose HMAs did not impair viability of HSPC-NK cells. Furthermore, low-dose DAC preserved HSPC-NK killing, proliferation, and interferon gamma production capacity, whereas AZA diminished their proliferation and reactivity. Importantly, we showed HMAs and HSPC-NK cells could potently work together to target AML cell lines and patient AML blasts. In vivo, both agents exerted a significant delay in AML progression in NOD/SCID/IL2Rgnull mice, but the persistence of adoptively transferred HSPC-NK cells was not affected. Infused NK cells showed sustained expression of most activating receptors, upregulated NKp44 expression, and remarkable killer cell immunoglobulin-like receptor acquisition. Most importantly, only DAC potentiated HSPC-NK cell anti-leukemic activity in vivo. Besides upregulation of NKG2D- and DNAM-1-activating ligands on AML cells, DAC enhanced messenger RNA expression of inflammatory cytokines, perforin, and TRAIL by HSPC-NK cells. In addition, treatment resulted in increased numbers of HSPC-NK cells in the bone marrow compartment, suggesting that DAC could positively modulate NK cell activity, trafficking, and tumor targeting. These data provide a rationale to explore combination therapy of adoptive HSPC-NK cells and DAC in patients with AML.