[Effects of H3K27 methylation inhibitor EPZ005687 on apoptosis, proliferation and cell cycle of U937 cells and normal CD34 positive cells]

The aim of this study was to investigate the effects of H3K27 methylation inhibitor EPZ005687 on the Apoptosis, proliferation and cell cycle of U937 cells and normal CD34⁺ cells. The U937 cells and normal CD34⁺ cells were treated with different concentration of EPZ005687 at different time points. The Apoptosis rate was determined by Annexin V/PI staining. The cell proliferation and cell cycle was determined using WST-1 assay and 7-AAD assay, respectively. The activity of H3K27 methylation was detected by chemiluminescent immunoassay. The results showed that the EPZ005687 induced an obvious Apoptosis of U937 cells. The apoptotic rate was 3.96% ± 0.79%,5.74% ± 0.73%,13.34% ± 1.77% and 25.24% ± 2.55% in U937 cells treated with 0.5, 1, 5 and 10 µmol/L EPZ005687 for 48 hours, respectively. However, EPZ005687 had rare effect on normal bone marrow(NBM) CD34⁺ cells. The apoptotic rate was 3.64% ± 0.62%,4.28% ± 0.99%,6.18% ± 1.19% and 7.56% ± 1.34% after U937 cells were treated with 0.5, 1, 5 and 10 µmol/L EPZ005687 for 48 hours, respectively. EPZ005687 inhibited obviously the proliferation of U937 cells but had weak effect on the proliferation of NBMCD34⁺ cells. The inhibitory effect of EPZ005687 on U937 cells was time-dependent after treated with 0.5, 1, 5 and 10 µmol/L EPZ005687 from 12 to 96 hours. EPZ005687 induced G1 phase blocking (G1%, 64.18% ± 13.27% vs 49.43% ± 12.54%) and decreased the percentage of cells in S phase (9.67% ± 2.61% vs15.26% ± 5.58%) in U937 cells. However, EPZ005687 had no effect on the cell cycle of NBMCD34⁺ cells. In addition, EPZ005687 produced obviously depletion of H3K27 methylation in U937 cells (P < 0.05), but hardly had effect on the H3K27 methylation of NBMCD34⁺ cells. It is concluded that the EPZ005687 inhibites proliferation, induces Apoptosis and cell cycle blocking in G1 phase in leukemia cells. This agent may have potential value in clinical application.