5-Azacytidine supports the long-term repopulating activity of cord blood CD34(+) cells.
ABSTRACT DNA methylation plays important roles in a wide range of biological phenomena, especially in the embryonic development and tumorigenesis. However, correlations between differentiation and DNA methylation have not been clarified well in each differentiation system. In this study, we focused our attention on regulatory roles of DNA methylation in normal hematopoietic differentiation using a demethylating reagent, 5-azacytidine (5-AzaC). As a source of hematopoietic progenitor cells, we used CD34(+) cells prepared from human umbilical cord blood and examined the effects of 5-AzaC on the colony-forming activity and the long-term culture-initiating (LTC-IC) activity of these cells. 5-AzaC treatment increased LTC-IC frequency 1.57- to 2.50-fold as compared to the nontreated control. In parallel to this, immunoblotting analysis showed that the intensity of overall DNA methylation decreased after 5-AzaC treatment. These results indicated the involvement of DNA methylation and demethylation in controlling immaturity of hematopoietic progenitor cells and the usefulness of 5-AzaC for regulating this immaturity.
[show abstract] [hide abstract]
ABSTRACT: Silencing of tumor suppressor genes (TSGs), by DNA methylation, is well known in adult cancers. However, based on the "stem cell" theory of tumorigenesis, the early epigenetic events arising in malignant precursors remain unknown. A recent report demonstrates that, while pluripotent embryonic stem cells lack DNA methylation and possess a "bivalent" pattern of activating and repressive histone marks in numerous TSGs, analogous multipotent malignant cells derived from germ cell tumors (embryonic carcinoma cells) gain additional silencing modifications to those same genes. These results suggest a possible mechanism by which aberrant differentiation, mediated by histone and DNA methylation, instigates tumor progression.BioEssays 10/2007; 29(9):842-5. · 4.95 Impact Factor
Article: CpG methylation patterns and decitabine treatment response in acute myeloid leukemia cells and normal hematopoietic precursors.[show abstract] [hide abstract]
ABSTRACT: The DNA hypomethylating drug decitabine maintains normal hematopoietic stem cell (HSC) self-renewal but induces terminal differentiation in acute myeloid leukemia (AML) cells. The basis for these contrasting cell fates, and for selective CpG hypomethylation by decitabine, is poorly understood. Promoter CpGs, with methylation measured by microarray, were classified by the direction of methylation change with normal myeloid maturation. In AML cells, the methylation pattern at maturation-responsive CpGs suggested at least partial maturation. Consistent with partial maturation, in gene expression analyses, AML cells expressed high levels of the key lineage-specifying factor CEBPA, but relatively low levels of the key late-differentiation driver CEBPE. In methylation analysis by mass spectrometry, CEBPE promoter CpGs that are usually hypomethylated during granulocyte maturation were significantly hypermethylated in AML cells. Decitabine-induced hypomethylation was greatest at these and other promoter CpGs that are usually hypomethylated with myeloid maturation, accompanied by cellular differentiation of AML cells. In contrast, decitabine-treated normal HSCs retained immature morphology, and methylation significantly decreased at CpGs that are less methylated in immature cells. High expression of lineage-specifying factor and aberrant epigenetic repression of some key late-differentiation driver genes distinguishes AML cells from normal HSCs, and could explain the contrasting differentiation and methylation responses to decitabine.Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 08/2011; 26(2):244-54. · 8.30 Impact Factor