CpG methylation patterns and decitabine treatment response in acute myeloid leukemia cells and normal hematopoietic precursors

Department of Translational Hematology and Oncology Research, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K (Impact Factor: 10.43). 08/2011; 26(2):244-54. DOI: 10.1038/leu.2011.207
Source: PubMed


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.

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    • "Increasing interest in targeting epigenetic pathways has led to multiple studies of DNA demethylating agents, including decitabine (DAC) administered in low dose regimens [3]–[5]. DAC is a nucleoside analog believed to have multiple distinct mechanisms of action, including; activation of methylation-silenced tumor-suppressor genes, up-regulation of microRNA and induction of DNA damage responses [6]–[10]. DAC achieved marketing authorisation for the treatment of MDS (approved in the US, based on randomised study versus best supportive care) and for AML in older patients (approved in the EU, following randomised controlled study versus cytarabine or best supportive care) [3], [11], [12]. "
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    ABSTRACT: The current interest in epigenetic priming is underpinned by the belief that remodelling of the epigenetic landscape will sensitise tumours to subsequent therapy. In this pre-clinical study, paediatric AML cells expanded in culture and primary AML xenografts were treated with decitabine, a DNA demethylating agent, and cytarabine, a frontline cytotoxic agent used in the treatment of AML, either alone or in combination. Sequential treatment with decitabine and cytarabine was found to be more effective in reducing tumour burden than treatment with cytarabine alone suggesting that the sequential delivery of these agents may a have real clinical advantage in the treatment of paediatric AML. However we found no evidence to suggest that this outcome was dependent on priming with a hypomethylating agent, as the benefits observed were independent of the order in which these drugs were administered.
    PLoS ONE 01/2014; 9(1):e87475. DOI:10.1371/journal.pone.0087475 · 3.23 Impact Factor
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    • "The molecular actions of decitabine offer an important alternative to conventional apoptosis-based chemotherapy, since low, non-cytotoxic doses can induce cell cycle exit in cancer cells by p53-independent differentiation pathways[26, 34-35, 38]. However, this relatively low dosage could be particularly vulnerable to treatment failure caused by CDA-mediated degradation, exemplified by protection for cancer cells in CDA-rich organs. "
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    ABSTRACT: We document for the first time that sanctuary in an organ which expresses high levels of the enzyme cytidine deaminase (CDA) is a mechanism of cancer cell resistance to cytidine analogues. This mechanism could explain why historically, cytidine analogues have not been successful chemotherapeutics against hepatotropic cancers, despite efficacy in vitro. Importantly, this mechanism of resistance can be readily reversed, without increasing toxicity to sensitive organs, by combining cytidine analogue with an inhibitor of cytidine deaminase (tetrahydrouridine). Specifically, CDA rapidly metabolizes cytidine analogues into inactive uridine counterparts. Hence, to determine if sheltering/protection of cancer cells in organs which express high levels of CDA (e.g., liver) is a mechanism of resistance, we utilized a murine xenotransplant model of myeloid cancer that is sensitive to epigenetic therapeutic effects of the cytidine analogue decitabine in vitro and hepato-tropic in vivo. Treatment of tumor-bearing mice with decitabine (subcutaneous 0.2mg/kg 2X/week) doubled median survival and significantly decreased extra-hepatic tumor burden, but hepatic tumor burden remained substantial, to which the animals eventually succumbed. Combining a clinically-relevant inhibitor of CDA (tetrahydrouridine) with a lower dose of decitabine (subcutaneous 0.1mg/kg 2X/week) markedly decreased liver tumor burden without blood count or bone marrow evidence of myelotoxicity, and with further improvement in survival. In conclusion, sanctuary in a CDA-rich organ is a mechanism by which otherwise susceptible cancer cells can resist the effects of decitabine epigenetic therapy. This protection can be reversed without increasing myelotoxicity by combining tetrahydrouridine with a lower dose of decitabine.
    Oncotarget 09/2012; 3(10). DOI:10.18632/oncotarget.597 · 6.36 Impact Factor
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    • " - hanced dependence on Dnmt1 . Two DNA methylation inhibitors , azacitidine and decitabine , have been FDA - approved for clinical use in the United States . In recent preclinical and clinical studies , therapeutic doses of decitabine were demonstrated to induce terminal differ - entiation of AML cells without altering normal HSC self - renewal ( Negrotto et al . 2011 ) , and azacitidine was found to have an acceptable safety profile and could substantially prevent or delay hemato - logic relapse in MDS and AML follow - ing HSC transplant ( Platzbecker et al . 2011 ) . Despite these successes , the high - dose cytotoxic effects and chemical instability of these DNA methylation inhibitors have prompte"
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    ABSTRACT: Epigenetic mechanisms regulating leukemia stem cells (LSCs) are an attractive target for therapy of blood cancers. Here, we report that conditional knockout of the DNA methyltransferase Dnmt1 blocked development of leukemia, and haploinsufficiency of Dnmt1 was sufficient to delay progression of leukemogenesis and impair LSC self-renewal without altering normal hematopoiesis. Haploinsufficiency of Dnmt1 resulted in tumor suppressor gene derepression associated with reduced DNA methylation and bivalent chromatin marks. These results suggest that LSCs depend on not only active expression of leukemogenic programs, but also DNA methylation-mediated silencing of bivalent domains to enforce transcriptional repression.
    Genes & development 02/2012; 26(4):344-9. DOI:10.1101/gad.184341.111 · 10.80 Impact Factor
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