Regulatory effect of decitabine on human acute myeloid leukemia cell line HL-60 and its mechanism

Abstract

Objective To investigate the effect of decitabine (DAC) on human acute myeloid leukemia (AML) cell line HL-60 and the regulating of natural killer (NK) cell activating receptor (NKG2D) ligands (NKG2DL), and to detect the molecular mechanism of JAK-STAT3-SOCS signaling pathway. Methods The effect of DAC on the proliferation of HL-60 was detected by using CCK-8 assay. The cell apoptosis was analyzed by using Annexin-V/PI double standard method. The expressions of receptor NKG2DL including MICA/B and ULBPs in HL-60 cells were detected by using flow cytometry (FCM). The killing activity of NK cells was analyzed by using carboxy fluorescein diacetate succinimidyl ester (CFSE). The expressions of JAK/STAT3 signaling pathway or molecules including STAT3, its upstream kinases JAK1, JAK2 and the negative regulator of STAT3, SOCS-1, SOCS-3 were examined by Western blot. Methylation level of the SOCS-1, SOCS-3 gene after the treatment of DAC was analyzed by using methylation-sensitive high resolution melting (MS-HRM). Results There was an obvious inhibitory effect of DAC on HL-60 cells. The cell viability of HL-60 treated with 0.2, 0.5, and 1.0 μmol/L DAC for 48 h was decreased by (25±11) %, (39±8) % and (50±7) % (P < 0.01) respectively compared with those cells without DAC treatment. The incidence of apoptosis was (24.77±7.50) %, (27.10±4.48) % and (30.53±3.93) % after DAC treatment for 48h respectively, which were higher than that of untreated cells [(3.11±0.50) %] (P < 0.01). DAC induced a significant up-regulation of MICA/B, ULBP-1, ULBP-3 in HL-60 cells, and enhanced the sensitivity of HL-60 cells to NK cytotoxicity. Western blot results showed that a down-regulating expression of STAT3 and JAK1, JAK2 protein was detected, in addition to the phosphor-STAT3 and phosphor-JAKs in HL-60 cells after DAC treatment, but the expressions of SOCS-1 and SOCS-3 protein were increased. HRM results showed that DAC could inhibit the methylation of SOCS-3 gene. Conclusion DAC can inhibit the proliferation of HL-60 cells, upregulate the expression of NKG2DL and enhance the cytotoxicity of NK targeted to HL-60 cells, which might be related to the activity regulation of intracellular JAK-STAT3-SOCS signaling pathway. Key words: Leukemia, myeloid, acute; Cell proliferation; Apoptosis; Molecular mechanisms of action; Decitabine