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

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.