Biological Function And Molecular Mechanism Of ELL Family Genes In Acute Myeloid Leukemia

The treatment for acute myeloid leukemia(AML)is difficult and the curative effect is poor,there is an urgent need to explore novel targets for developing new treatment strategies.Although BET inhibitors(BETi)have exhibited varible potential for hematological malignancies via targeting epigentetic regulators,its drug resistance limits its clinical application.Our previous study found that CCCTC-binding factor(CTCF)plays a functional role in the establishment and maintenance of high-order chromatin structure of the HOXA genes in AML through binding to the site located between HOXA7 and HOXA9(CBS7/9),and the BET family protein Brd4 was recruited by ELL3.However,the relationship between CTCF,HOXA and ELL3,as well as the regulatory role of ELL3 in HOXA expression and BET inhibitor sensitivity are still unclear.Therefore,this study is expected 1)to explore the underlying mechanism of HOXA9 gene regulated by CTCF through ELL3 in the progression of AML,as well as its effect on the sensitivity of BETi;2)to evaluate the correlation between ELL family genes and the prognosis of AML with normal karyotype(CN-AML)by using clinical data in public databases and functional verification.Results:1.Deletion of CBS7/9 rather than CBS5/6 and CBS9/10 led to reduced cell viability,enhanced apoptosis and increased sensitivity to BETi treatment,and knockout of CBS7/9 decreased recruitment of H4K5ac at posterior HOXA genes in AML cells.Gain of function(GOF)expression of HOXA9 can rescue and restore the resistance to BETi treatment of the CBS7/9 KO AML cells.These results indicated that BETi therapeutic sensitivity in AML is depended on the expression level of the HOXA9 gene.2.CBS7/9 deletion disrupted transcription elongation mediated by ELLS,thereby leading to decreased posterior HOXA gene expression.ELL3 could regulate HOXA9 gene expression by recruiting Brd4.By knockdown or overexpression of ELL3,we confirmed that ELL3 is a key factor in CTCF-mediated HOXA9 gene expression and enhanced sensitivity to BETi treatment in AML cells.3.The Kaplan-Meier analysis revealed that higher ELL expression markedly correlated with the short overall survival(OS)of the patients with CN-AML.GO and KEGG enrichment analysis were subsequently conducted.The hub gene BMP4 was screened by the analysis of the PPI network.In vitro experiments confirmed that ELL gene is closely related to BMP4 gene expression and affects the proliferation,apoptosis and drug sensitivity of AML cells.Conclusions:1)Thus,the novel epigenetic regulation mechanism of CTCF-ELL3-HOXA9 is proposed to provide a potential therapeutic target for AML.2)These observations suggested ELL might affect the outcome of CN-AML via regulating BMP4,and it could serve as a new predictive biomarker for CN-AML patients.