Pan-HDAC inhibitors augment IL2-induced proliferation of NK cells via the JAK2-STAT5B signaling pathway

Natural killer (NK) cells are a subtype of lymphocytes with the ability to quickly and efficiently identify and eliminate tumor cells. In the presence of IL2, NK cells can divide rapidly but in limited numbers. According to previous studies, in vivo treatment with histone deacetylase (HDAC) inhibitors did not impair NK-cell function. This study aimed to investigate the effect of HDAC inhibitors on NK-cell proliferation and the underlying regulatory mechanism.NK92 cells, primary NK (pNK) cells, and CD19-CAR-NK92 cells were treated with low concentrations of pan-HDACi Dacinostat (Dac) and Panobinostat (Pan) in the presence of IL2, and Cell Counting Kit-8 (CCK8), 5-ethynyl-2'-deoxyuridine (EdU), and flow cytometry assays were used to assess cell proliferation and apoptosis. The expression of granzyme B was detected by immunofluorescence, and the expression of CD107a and NKG2D was determined by flow cytometry. The downstream regulatory genes were identified by RNA-seq, and the "JAK-STAT signaling pathway"- and "Cell cycle signaling pathway"-related genes were detected by real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis. The JAK2V617F mouse model was constructed to simulate the upregulation of the JAK2 signaling pathway in vivo, and the NK proliferation was evaluated by flow cytometry. A tumor-bearing nude mouse model was constructed to determine the anti-tumor efficacy of NK92 cells following Dac treatment.In the presence of IL2, the proliferation rate of NK92 cells, pNK cells, and CD19-CAR-NK92 cells treated with pan-HDACi Dac and Pan at low nanomolar doses was significantly increased, although cell function was unaffected. Low doses of Dac upregulated the JAK-STAT signaling pathway and enhance the cell cycle via that pathway. In addition, the in vivo experiment in nude mice showed that the capacity of Dac treated NK92 cells to eliminate tumor cells was unaffected.Low nanomolar doses of Pan-HDACi enhanced IL2-induced NK cell proliferation without compromising the functioning of NK cells.