<p>Expression Profiles of DNA Methylation and Demethylation Machinery Components in Pediatric Myelodysplastic Syndrome: Clinical Implications</p>

Abstract

The aim of this study was to analyse the expression profiles of DNMT1, DNMT3A, DNMT3B (components of DNA methylation machinery), TET2 and APOBEC3B (components of DNA demethylation machinery) in pediatric MDS patients and investigate their associations with MDS subtypes, cytogenetics, evolution to acute myeloid leukemia (AML) and p15 INK4B methylation level. Patients and Methods: The expressions of DNMT1, DNMT3A, DNMT3B, TET2, and APOBEC3B were evaluated in 39 pediatric MDS patients by real-time quantitative PCR (qPCR). The quantification of p15 INK4B methylation levels (MtL) was performed in 20 pediatric MDS patients by pyrosequencing. Mann-Whitney test was used to evaluate possible differences between the expression levels of selected in patients and donors, according to MDS subtypes, karyotypes, evolution to AML and p15 INK4B MtL. The correlations between the expression levels of the different genes were assessed by Spearman rank correlation coefficient. Results: We found that DNMTs expression levels were higher in pediatric MDS compared to donors [DNMT1 (p<0.03), DNMT3A (p<0.03), DNMT3B (p<0.02)]. TET2 and APOBEC3B expression levels did not show a statistically significant difference between pediatric patients and donors. Considering MDS subtypes, patients at initial stage presented DNMT1 overexpression (p<0.01), while DNMT3A (p<0.02) and DNMT3B (p<0.007) were overexpressed in advanced subtypes. TET2 and APOBEC3B expression did not differ in MDS subtypes. DNMT1 (p<0.03), DNMT3B (p<0.03), and APOBEC3B (p<0.04) expression was higher in patients with normal karyotypes, while patients with abnormal karyotypes showed higher DNMT3A expression (p<0.03). Karyotypes had no association with TET2 expression. DNMTs overexpression was observed in patients who showed disease evolution. A positive correlation was found between DNMTs expression and between APOBEC3B and DNMT3A/DNMT3B. However, TET2 expression was not correlated with DNMTs or APOBEC3B. p15 INK4B MtL was higher in pediatric MDS patients compared with donors (p<0.03) and its hypermethylation was associated with increased DNMT1 expression (p<0.009). Conclusion: Our results suggest that the overexpression of DNMTs and an imbalance between the expressions of the DNA methylation/demethylation machinery components play an important role in MDS development and evolution to AML. These results have clinical implications indicating the importance of DNMTs inhibitors for preventing or delaying the progression to leukemia in pediatric MDS patients.

A review of aberrant DNA methylation in bone marrow mesenchymal stromal cells: a new possible access of acute myeloid leukemia

“…Both too little and too much DNMT expression may play a role in these diseases. Just like Lovatel and colleagues showed that the overexpression of DNMTs plays an important role in pediatric MDS patients developing into AML [25].…”

The effect of decitabine-combined minimally myelosuppressive regimen bridged allo-HSCT on the outcomes of pediatric MDS from 10 years’ experience of a single center

“…Preemptive treatment for the minimal residual disease (MRD) is essential for preventing or substantially delaying hematological relapse after HSCT in pediatric MDS, especially in high-risk subgroups. The discovery of genome-wide DNA hypermethylation in pediatric MDS provides a rationale for DNMT inhibitors applicatio n [9,17]. Low-dose decitabine could directly and irreversibly inhibit the DNA methyltransferases.…”

“…As for the pre-transplant period for aMDS, a diversity of therapy strategies like intensive chemotherapy, AMLtype induction chemotherapy, minimally myelosuppressive regimen (MMR) and DNA methyltransferase (DNMT) inhibitors has been investigate d [9,10]. Intensive chemotherapy is not generally recommended due to showing no survival benefi t [11].…”

“…Hypermethylation of critical genes was revealed in adult and childhood MDS, considered one of the disease's driving alteration s [9,17,18]. In addition, hypermethylation of the promoters of various genes was associated with unfavorable prognosis in MDS, and the strategy of adopting DNA-hypomethylating agents including azacitidine (AZA) and decitabine (DAC) combination therapy is appealing for MD S [19,20].…”

Recent advances in understanding DNA methylation of prostate cancer

“…have shown there is increased expression of DNMT3A2 , DNMT3B , and EZH2 in tumors, and transient DNMT3B1 and DNMT3B2 overexpression in primary prostate cells results in increased methylation of some CpG sites that show increased methylation in tumors ( 101 ). Furthermore, in AML, TET2, IDH1, and DNMT3B do not seem to affect each other in terms of methylation pattern and regulation of downstream genes, but IDH1 and DNMT3A do ( 58 , 102 ). More specifically, co-occurrence of DNMT3A and IDH1 mutations show epigenetic patterns different from those of either IDH1 or DNMT3A mutation, upregulation of RAS signaling and unique sensitivity to MEK inhibition and appear to be associated with either worse clinical outcome or show no difference in EFS or OS ( 103 – 105 ).…”