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)是一种儿童早期侵袭性骨髓增生性肿瘤，是一种DNA甲基化控制受损的疾病。一组患者携带的白血病克隆在特定的靶点具有广泛的DNA高甲基化。这些儿童在移植后面临疾病复发的严重风险。通过对一系列JMML病例进行全基因组CpG甲基化分析，我们发现cAMP反应元件结合蛋白(CREB)结合蛋白CREBBP是一种转录共激活蛋白和组蛋白乙酰转移酶，在髓系白血病的发生中具有广泛的证据，是高危JMML表观遗传修饰的目标。此外，DNA超甲基化还改变了编码microRNA的几个基因座。首先，我们将在扩大的JMML患者队列中进行系统的CREBBP修饰的筛查，证实此类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在低风险和高风险JMML中的表达模式，研究实验性CREBBP抑制JMML的表型后果，并确定当CREBBP功能障碍时其功能受损的目标启动子我们将研究JMML中带有表观遗传启动子修饰的microRNA的全基因组谱，鉴定JMML中异常调控的microRNA的靶结构，并表征表观遗传microRNA沉默在这种白血病中的功能作用。我们期待这些研究将加深我们对JMML表观遗传异常与侵袭性表型之间密切联系的理解，它们将为表观遗传异常在髓系白血病发病中的作用提供有价值的见解，并将为JMML HSCT后高失败率提供功能解释。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.