Disordered epigenetic regulation of the CREBBP oncoprotein and of micro-RNA transcription in juvenile myelomonocytic leukemia at high risk of relapse

我们以前的工作表明，幼年粒单核细胞白血病（JMML），一种侵袭性骨髓增生性肿瘤的早期儿童，是一种疾病与受损的DNA甲基化控制。一部分患者携带白血病克隆，在特定靶位点具有广泛的DNA超甲基化。这些儿童面临移植后疾病复发的严重风险。在一系列JMML病例中使用全基因组CpG甲基化分析，我们确定了cAMP反应元件结合蛋白（CREB）结合蛋白CREBBP，一种转录共激活因子和组蛋白乙酰转移酶，在髓性白血病发生中具有良好的作用，作为高危JMML表观遗传修饰的靶点。此外，编码micro-RNA的几个位点被DNA超甲基化改变。在这里，我们建议调查如何表观遗传失调1）CREBBP，2）特定的micro-RNAs，有助于功能难治性JMML表型。首先，我们将进行一个系统的筛选表观遗传CREBBP修饰在一个扩展队列的JMML患者，证实这种病变的不良预后意义，使用报告构建体详细分析CREBBP CpG岛甲基化对其表达的影响，研究CREBBP在低风险与高风险JMML中的表达模式，研究JMML中实验性CREBBP抑制的表型后果，并定义当CREBBP在JMML中变得功能障碍时其功能受损的靶启动子。其次，我们将研究JMML中具有表观遗传启动子修饰的微RNA的全基因组谱，确定JMML中异常调节的micro-RNA的靶结构，并表征表观遗传micro-RNA沉默在该白血病中的功能作用。我们预计这些研究将增强我们对JMML中表观遗传异常和侵袭性表型之间密切联系的理解，他们将提供有价值的见解，表观遗传失调的作用，在启动髓性白血病，他们将提供功能解释后，高失败率HSCT的JMML。此外，这些研究将加强在JMML中使用表观遗传疗法的临床前理论基础。

Our previous work indicates that juvenile myelomonocytic leukemia (JMML), an aggressive myeloproliferative neoplasm of early childhood, is a disease with impaired DNA methylation control. A subset of patients carry a leukemic clone with extensive DNA hypermethylation at specific target sites. These children face a serious risk of disease recurrence after transplantation. Using genome-wide CpG methylation profiling in a pilot series of JMML cases, we identified the cAMP-responsive element binding protein (CREB)-binding protein CREBBP, a transcriptional co-activator and histone acetyltransferase with a well-documented role in myeloid leukemogenesis, as a target of epigenetic modification in high-risk JMML. In addition, several loci encoding micro-RNAs were altered by DNA hypermethylation. Here we propose to investigate how epigenetic dysregulation 1) of CREBBP, and 2) of specific micro-RNAs, contributes functionally to the refractory JMML phenotype.First, we will perform a systematic screen for epigenetic CREBBP modification in an extended cohort of JMML patients, corroborate the adverse prognostic significance of such lesions, use reporter constructs to analyze the effects of CREBBP CpG island methylation on its expression in detail, study the expression patterns of CREBBP in low-risk versus high-risk JMML, look into the phenotypic consequences of experimental CREBBP repression in JMML, and define target promoters whose function is impaired when CREBBP becomes dysfunctional in JMML.Second, we will study the genome-wide spectrum of micro-RNAs with epigenetic promoter modification in JMML, identify target structures of aberrantly regulated micro-RNAs in JMML, and characterize the functional role of epigenetic micro-RNA silencing in this leukemia.We anticipate that these investigations will enhance our understanding of the close link between epigenetic aberrations and aggressive phenotype in JMML, that they will provide valuable insight into the role of epigenetic dysregulation in the initiation of myeloid leukemia, and that they will provide functional explanation for the high rate of failure after HSCT for JMML. Moreover, these studies will strengthen the preclinical rationale for the use of epigenetic therapy in JMML.