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Myelodysplastic syndrome marrow stroma shows widespread aberrant hypermethylation that is abrogated by treatment with DNMT inhibitors

ABSTRACT: The marrow microenvironment contributes to the pathogenesis of ineffective hematopoiesis in Myelodysplastic Syndromes (MDS). Since mutations and cytogenetic alterations are generally not present in marrow stromal cells, we hypothesized that epigenetic alterations may be responsible for altered stroma functionin MDS. Global DNA methylation of MDS marrow-derived stroma was analyzed by HELP assay and compared to healthy controls. MDS stroma showed aberrant hypermethylation that preferentially occurred outside of CpG islands and involved important signaling pathways.Comparison with stroma derived from 5-Azacytidine (5-Aza) treated MDS patients revealed abrogation of aberrant methylation in treated samples. Integrative expression analysis revealed that the WNT pathway was epigenetically dysregulated in MDS stroma, and the WNT antagonists FRZB and SFRP1 were aberrantly hypermethylated and underexpressed. These epigenetic changes were validated ina co-culture model of stroma and leukemic cells and in an independent set of MDS samples. Importantly, 5-Aza treatment of MDS stroma enhanced hematopoietic activity and erythroid differentiationfrom co-cultured healthy CD34+ cells. These results reveal widespread aberrant epigenetic changes in the MDS marrow microenvironment and demonstrate that DNA methyl transferase inhibitors alter the epigenomic profiles of stromal cells, potentiallycontributing to theirtherapeutic efficacy.

ORGANISM(S): Homo sapiens

PROVIDER: GSE60233 | GEO | 2015/05/20

SECONDARY ACCESSION(S): PRJNA257803

REPOSITORIES: GEO

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Project description:Genome-wide expression and methylation profiling identifies novel targets with aberrant hypermethylation and reduced expression in low-risk myelodysplastic syndromes (MDSs). Gene expression profiling signatures may be used to classify the subtypes of Myelodysplastic syndrome (MDS) patients. However, there are few reports on the global methylation status in MDS. The integration of genome-wide epigenetic regulatory marks with gene expression levels would provide additional information regarding the biological differences between MDS and healthy controls. Gene expression and methylation status were measured using high-density microarrays. A total of 552 differentially methylated CpG loci were identified as being present in low-risk MDS; hypermethylated genes were more frequent than hypomethylated genes. In addition, mRNA expression profiling identified 1005 genes that significantly differed between low-risk MDS and the control group. Integrative analysis of the epigenetic and expression profiles revealed that 66.7% of the hypermethylated genes were underexpressed in low-risk MDS cases. Gene network analysis revealed molecular mechanisms associated with the low-risk MDS group, including altered apoptosis pathways. The two key apoptotic genes BCL2 and ETS1 were identified as silenced genes. In addition, the immune response and micro RNA biogenesis were affected by the hypermethylation and underexpression of IL27RA and DICER1. Our integrative analysis revealed that aberrant epigenetic regulation is a hallmark of low-risk MDS patients and could have a central role in these diseases. Low-risk MDS patients and age-matched controls without haematological malignancies were included in the study. Mononuclear cells were isolated from bone marrow samples of low-risk MDS patients and controls by density gradient (Ficoll). A cohort of 18 patients with low-risk MDS and seven controls were included in a simultaneous integrative study of methylation and expression, while the whole series was used as a control group of expression data.

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Myelodysplastic syndrome marrow stroma shows widespread aberrant hypermethylation that is abrogated by treatment with DNMT inhibitors

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