The Roles Of HDAC Inhibitor VPA In Enhancement Of Differentiation,Apoptosis And Sensitivity Of Leukemia Cells To NK Cells

ObjectiveIn the present study, we took human promyelocytic leukemia cells HL-60 as the research object,the enhancement of ATRA and ORI by VPA was observed to detect the role of HDAC inhibitors VPA on differentiation induction by ATRA or apoptosis induction by ORI in HL-60 cells. The effect of VPA on the sensitivity of HL-60 cells to NK cells and its key mechanism were also been investigated. This research provides foundation for exploring factors that apply the drug VPA,ATRA of low dose or ORI.It will probably provide theory foundation for design new tumor therapeutic strategy.MethodsHL-60 cells which in logarithmic phase were incubated with different concentrations of ATRA, ORI or VPA for 1 to 3 days under the condition of 37°C, 5%CO2. Respectively, the cell proliferation was observed by trypan blue staining assay; The CD11b, cell cycle and apoptosis were detected by flow cytometry. The NK-92 cells killing activity to HL-60 cells were detected by flow cytometry with CFSE and PI double staining. The protein and gene expression of surface NK cell receptor ligands in HL60 cells were detected by FACS and RT-PCR. Oridonin of 6~12μmol/L combined with VPA of 0.5~1mmol/L were added in exponential growth HL-60 cells respectively. Flow cytometry was used to evaluate apoptosis with Annexin V and propidium iodide (PI) double staining. ResultsThe results showed that the proliferation of HL-60 cells was obviously inhibited and the differentiation and apoptosis was induced in HL-60 cells by ATRA or VPA, the cells were arrested at the stage of G0/G1. And VPA of 1mmol/L combined with ATRA of 0.5μmol/L can enhance NK cells natural killer sensitivity of HL-60 cells, which contribute to the upregulation of the surface MHC-I related molecules (MICA/B) and CD54 expression and downregulation of HLA-ABC. The combination of oridonin and VPA could synergistically inactivate HL-60 cells,inhibit the cell proliferation and induce apoptosis in a dose-and time-dependent manner(P<0.05).ConclusionOur results indicated that the HDAC inhibitor VPA could enhance the role of ATRA on induction of differentiation in HL60 cells and the role of ORI on induction of apoptosis in HL60 cells. The VPA also played an improtant role in enhancing sensitivity of leukemia cells to NK cells, which was mediated by the up-regulation of NK cells activation receptor ligands and adhesion molecules ,down-regulation of NK cells inhibition receptor ligands on HL-60 cells. Our study provide the molecular mechanisms of improvement of the host immune surveillance by leukemia cells to the sensitivity, and to provide experimental and theory basis for the clinical combination of VPA and little dose of ATRA which to increase efficacy, reduce side effects. Oridonin can present a synergistic effect with VPA. Oridonin has a promising prospect in clinical use of leukemia.