DACT1基因羟甲基化在儿童WT1、IDH1/2、TET2基因突变的急性髓细胞白血病中的特征及临床意义

Characteristics and clinical significance of DACT1 hydroxymethylation in childhood acute myeloid leukemia with mutant WT1，IDH1/2，or TET2

摘要:

目的：研究dapper，β-连环蛋白拮抗剂，非洲爪蟾同系物1（dapper，antagonist of beta-catenin，homolog 1 Xenopus laevis，DACT1）在儿童急性髓细胞白血病（acute myeloid leukemia，AML）中的羟甲基化特征及其与预后的关系，寻找AML新的危险分层分子标志物。方法：测序分析本院血液科初发AML188例，根据是否存在Wilms肿瘤因子1（Wilms tumor 1，WT1）、异柠檬酸脱氢酶1/2（isocitrate dehydrogenase 1/2，IDH1/2）或TET蛋白2（ten-eleven translocation，TET2）基因突变，将病例分为WIT-AML组（30例）和非WIT-AML组（158例）；用糖基化qPCR及qPCR方法检测WIT-AML（16例）、非WIT-AML（14例）和非AML患儿（14例）的DACT1基因羟甲基化水平（5-hydroxymethylcytosine，5hmC）和表达水平，并用Spearman法研究羟甲基化与表达的相关性；随访患儿的缓解、复发及生存情况，采用COX回归分析DACT1羟甲基化对AML患儿总生存率（overall survival，OS）及无病生存率（event free survival，EFS）的影响。结果：WIT-AML组的DACT1 a、b区域（DACT1 a/b）甲基岛（CpG）羟甲基化（5hmC）水平较非WIT-AML组低（Ua=48.00，Pa=0.008；Ub=19.00，Pb=0.000），且其基因表达明显减低（Uexp=0.00，Pexp=0.000）；DACT1 a/b 甲基岛5hmC与DACT1的表达水平呈正相关（ra=0.812，Pa=0.000；rb=0.789，Pb=0.000）；DACT1a 5hmC水平减低是EFS的危险因素（HR=3.896，95%CI=1.161~13.073，P=0.028），同样也是OS的危险因素（HR=4.109，95%CI=1.226~13.771，P=0.022）。结论：在WIT-AML中，DACT1 5hmC水平和表达水平明显降低，DACT1a区5hmC水平降低可增加儿童AML生存风险，可作为AML一个新的独立预后不良指标。

Abstract:

Objective:To study the characteristics of hydroxymethylation of dapper，antagonist of beta-catenin，homolog 1（Xenopus laevis）（DACT1） in childhood acute myeloid leukemia（AML） and its relationship with prognosis，and to identify the new molecular marker for the risk classification of AML. Methods：This study included 188 newly diagnosed AML cases in Department of Hematology，The Children’s Hospital of Chongqing Medical University. Sanger sequencing was employed to analyze the mutation in Wilms’ tumor 1（WT1），isocitrate dehydrogenase 1/2（IDH1/2），or ten-eleven translocation（TET2）. These cases were assigned to either WIT-AML group（n=30） or non-WIT-AML group（n=158） according to the presence or absence of mutation in any of the above genes. The hydroxymethylation（5-hydroxymethylcytosine，5hmC） level of the DACT1 gene and the expression of DACT1 were assessed using glycosylation qPCR and qPCR for 16 WIT-AML cases，14 non-WIT-AML cases，and 14 non-AML cases. The correlation between the hydroxymethylation and expression of DACT1 was investigated by Spearman analysis. Data on the remission，relapse，and survival of children were acquired by follow-up. Cox regression analysis was employed to assess the effect of DACT1 hydroxy-methylation on the overall survival（OS） and event-free survival（EFS） rates of children with AML. Results：Compared with the non-WIT-AML group，the WIT-AML group had a significantly lower 5hmC level at the CpG island of DACT1 a/b（Ua=48.00，Pa=0.008；Ub=19.00，Pb=0.000），as well as significantly reduced DACT1 expression（Uexp=0.00，Pexp=0.000）. Moreover，DACT1 a/b 5hmC level was positively correlated with DACT1 expression（ra=0.812，Pa=0.000；rb=0.789，Pb=0.000）. Reduced DACT1a 5hmC was associated with shorter survival（EFS：hazard ratio[HR]=3.896，95% confidence interval[CI]=1.161-13.073，P=0.028；OS：HR=4.109，95%CI=1.226-13.771，P=0.022）. Conclusion：In WIT-AML，DACT1 5hmC level and DACT1 expression are significantly decreased. Reduced DACT1a 5hmC is associated with shorter survival in children with AML，so it can be used as an independent unfavorable prognostic biomarker for childhood AML.