Molecular Targets for Therapy

The DNA methyltransferase inhibitors azacitidine, decitabine and zebularine exert differential effects on cancer gene expression in acute myeloid leukemia cells


The three DNA methyltransferase (DNMT)-inhibiting cytosine nucleoside analogues, azacitidine, decitabine and zebularine, which are currently studied as nonintensive therapy for myelodysplastic syndromes and acute myeloid leukemia (AML), differ in structure and metabolism, suggesting that they may have differential molecular activity. We investigated cellular and molecular effects of the three substances relative to cytarabine in Kasumi-1 AML blasts. Under in vitro conditions mimicking those used in clinical trials, the DNMT inhibitors inhibited proliferation and triggered apoptosis but did not induce myeloid differentiation. The DNMT inhibitors showed no interference with cell-cycle progression whereas cytarabine treatment resulted in an S-phase arrest. Quantitative methylation analysis of hypermethylated gene promoters and of genome-wide LINE1 fragments using bisulfite sequencing and MassARRAY suggested that the hypomethylating potency of decitabine was stronger than that of azacitidine; zebularine showed no hypomethylating activity. In a comparative gene expression analysis, we found that the effects of each DNMT inhibitor on gene transcription were surprisingly different, involving several genes relevant to leukemogenesis. In addition, the gene methylation and expression analyses suggested that the effects of DNMT-inhibiting cytosine nucleoside analogues on the cellular transcriptome may, in part, be unrelated to direct promoter DNA hypomethylation, as previously shown by others.

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Grant support: Kind Philipp Foundation T237/15893/2006 (to CF); José Carreras Leukemia Foundation DJCLS R06/42f (to ML); Research Commission of the Faculty of Medicine of the University of Freiburg (to CF and ML); Deutsche Forschungsgemeinschaft (to RC). We thank Dr A Heinzmann for providing the Affymetrix facility and J Heinze for excellent technical assistance with capillary sequencing. We sincerely thank Dr Peter A Jones, Dr Richard Momparler and Dr James Downing for critically reading the paper and providing helpful comments.

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Correspondence to C Flotho.

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Flotho, C., Claus, R., Batz, C. et al. The DNA methyltransferase inhibitors azacitidine, decitabine and zebularine exert differential effects on cancer gene expression in acute myeloid leukemia cells. Leukemia 23, 1019–1028 (2009).

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  • myeloid
  • DNA methylation
  • epigenetic therapy
  • 5-azacytidine
  • 5-aza-2′-deoxycytidine

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