The Prognostic Significance And Effects Of EZH2 In Acute Myeloid Leukemia

ObjectiveAcute myeloid leukemia(AML)is a clonal malignant hematopoietic stem cell disease,often accompanied by a variety of molecular cytogenetic abnormalities and its clinical prognosis vary greatly,although important progress has been made on molecular biology of AML at present,relapse or refractory is still great challenge for AML.Enhancer of zeste homolog 2(EZH2)is highly expressed in many tumors.Studies have shown that EZH2 inhibitors have anti-tumor effect,and there is a cross between the inhibition of histone methylation and DNA methylation.In this study,we investigated the correlation between the expression of EZH2 and the clinical characters andprognosis of AML.We also explored the role of EZH2 inhibitor or combined with DNAdemethylation drug in AML to provide a newpotential therapeutic target for AML.MethodsThe expression of EZH2 in bone marrow mononuclear cells of 99 patients with primary AML was measured by quantitative RT-PCR(qRT-PCR).The effect of EZH2 inhibitor GSK126 was investigated in HL60 and K562 human leukemic cells.Cell proliferation was determined by CCK8 assay.The expression of EZH2 was detected by qRT-PCR.Cell apoptosis was analyzed by flow cytometry and expression of cleaved caspase-3 proteinwas measured by Western blot.Furthermore,the effect of GSK126 combined with DAC was investigated in HL60 and K562 human leukemic cells.We measured cell proliferation ratesby CCK8 assay and calculated the combination index(CI),and detected expression of EZH2 by qRT-PCR,apoptosis rate by flow cytometryand expression level ofcleaved caspase-3protein by Western blot.ResultsEZH2 was overexpressed in 99 AML patients,and the overexpression of EZH2correlates with higher proportion of patients with poor prognosis and higher recurrence rate in twelve months(52.0%vs 28.6%,p=0.045),(54.8%vs 23.1%,p=0.015).After application of EZH2 inhibitor GSK126 to HL60 and K562 cells,expression of EZH2 gradually decreased with higher drug concentration,meanwhile,cell proliferation inhibition rate,apoptosis rate and cleaved caspase-3 protein level increased gradually.GSK126 combined with DAChad a synergistic effect on proliferation inhibition and apoptosis in HL60 and K562 cells.GSK126 enhanced the effect of DAC on decreasing the expression of EZH2 gene,and increasing the expression of cleaved caspase-3 protein.ConclusionsEZH2 is overexpressed in primary AML,and its overexpression is associated with poor prognosis of AML.EZH2 inhibitor GSK126 could inhibit leukemia cell growth and promote apoptosis,and EZH2 might be a potential therapeutic target for AML.The EZH2 inhibitor GSK126 and the DNA methylation inhibitor can synergistically inhibit the growth of AML cells and promote apoptosis,which can provide a new approach for the clinical treatment of AML.