Effect of 5-aza-2′-deoxycytidine (Dacogen) on covalent histone modifications of chromatin associated with the ɛ-, γ-, and β-globin promoters in Papio anubis

Butyrate is a prototype of histone deacetylase inhibitors that is believed to reactivate silent genes by inducing epigenetic modifications. Although butyrate was shown to induce fetal hemoglobin (HbF) production in patients with hemoglobin disorders, the mechanism of this induction has not been fully elucidated. Our studies of the epigenetic configuration of the ␤-globin cluster suggest that DNA methylation and histone H3 acetylation are important for the regulation of developmental stage-specific expression of the ␤-like globin genes, whereas acetylation of both histones H3 and H4 seem to be important for the regulation of tissuespecific expression. These studies suggest that DNA methylation may be important for the silencing of the ␤-like globin genes in nonerythroid hematopoietic cells but may not be necessary for their silencing in nonhematopoietic cells. Furthermore, our studies demonstrate that butyrate exposure results in a true reversal of the normal developmental switch from ␥-to ␤-globin expression. This is associated with increased histone acetylation and decreased DNA methylation of the ␥-globin genes, with opposite changes in the ␤-globin gene. These studies provide strong support for the role of epigenetic modifications in the normal developmental and tissue-specific regulation of globin gene expression and in the butyratemediated pharmacologic induction of HbF production.

Section: Discussionmentioning

confidence: 99%

Role of epigenetic modifications in normal globin gene regulation and butyrate-mediated induction of fetal hemoglobin

Fathallah

Weinberg

Galperin

et al. 2007

“…38 In baboons treated with 5-Aza-29-deoxycytidine by subcutaneous injection, changes in several histone modifications at the globin genes were detected, but H3K9me2 was not studied. 39 Alternatively, loss of G9a/GLP activity may direct DNA methylation 40 or affect the activity of LSD1, another therapeutic target for induction of fetal hemoglobin. 41 Of note, RE1 silencing transcription factor-mediated gene repression involves colocalization of G9a, LSD1, and histone deacetylases with other chromatin remodeling proteins.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of G9a methyltransferase stimulates fetal hemoglobin production by facilitating LCR/γ-globin looping

Krivega¹,

Byrnes

Vasconcellos

et al. 2015

“…The baboon model has been accurate and useful in predicting by body surface area scaling a safe human equivalent dose for SC DAC treatment and for combination oral THU and 5-azacytidine therapy. 2,18,19,33,[42][43][44][45][46] Therefore, the THU dose (400 mg/m 2 ) and timing (60 minutes before DAC) that are likely to be useful for human translation were identified by studies in baboons. In the pharmacokinetic studies in baboons, AUC last estimates for DAC alone were calculated over 240 minutes, whereas estimates for THU-DAC were calculated over 180 minutes (the permissible total duration of anesthesia in the nonhuman primate studies was 240 minutes; therefore, the administration of DAC 60 minutes after THU decreased the duration of sampling in THU-DACadministered animals).…”

Section: Discussionmentioning

confidence: 99%

Effects of tetrahydrouridine on pharmacokinetics and pharmacodynamics of oral decitabine

Lavelle

Vaitkus

Ling

et al. 2012

Self Cite

The deoxycytidine analog decitabine (DAC) can deplete DNA methyl-transferase 1 (DNMT1) and thereby modify cellular epigenetics, gene expression, and differentiation. However, a barrier to efficacious and accessible DNMT1-targeted therapy is cytidine deaminase, an enzyme highly expressed in the intestine and liver that rapidly metabolizes DAC into inactive uridine counterparts, severely limiting exposure time and oral bioavailability. In the present study, the effects of tetrahydrouridine (THU), a competitive inhibitor of cytidine deaminase, on the pharmacokinetics and pharmacodynamics of oral DAC were evaluated in mice and nonhuman primates. Oral administration of THU before oral DAC extended DAC absorption time and widened the concentration-time profile, increasing the exposure time for S-phase-specific depletion of DNMT1 without the high peak DAC levels that can cause DNA damage and cytotoxicity. THU also decreased interindividual variability in pharmacokinetics seen with DAC alone. One potential clinical application of DNMT1-targeted therapy is to increase fetal hemoglobin and treat hemoglobinopathy. Oral THU-DAC at a dose that would produce peak DAC concentrations of less than 0.2M administered 2؋/wk for 8 weeks to nonhuman primates was not myelotoxic, hypomethylated DNA in the ␥-globin gene promoter, and produced large cumulative increases in fetal hemoglobin. IntroductionThe deoxycytidine analog decitabine (DAC) can deplete DNA methyl-transferase 1 (DNMT1), a key chromatin-modifying enzyme, and thereby modify cellular epigenetics, gene expression, and differentiation. 1 Potential clinical applications include increasing erythropoiesis and fetal hemoglobin (HbF) expression to treat hemoglobinopathies, 2 inducing terminal differentiation in malignant cells, [3][4][5][6][7] and increasing self-renewal of normal hematopoietic stem cells. [8][9][10] Certain aspects of DAC's pharmacology and mechanism of action influence its clinical activity; unlike cytidine analogs such as cytarabine (AraC) or gemcitabine, the sugar moiety of DAC is unmodified. Therefore, at low concentrations, DAC does not terminate DNA chain synthesis 11,12 and can deplete DNMT1 without causing significant DNA damage or cytotoxicity both in vitro and in vivo. 2,3,[11][12][13][14][15] However, at high concentrations, similar to other nucleoside analogs, DAC is cytotoxic. Another important aspect of DAC action is that it is S-phase specific, so exposure timing critically influences efficacy. 13,16 Considering these properties of DAC, for the objective of noncytotoxic DNMT1 depletion, the ideal DAC concentration-time profile is low peak drug levels but extended time above minimum concentrations required to deplete DNMT1. Oral administration of DAC could be more likely to produce this concentration-time profile than parenteral administration and would have major logistical advantages. A significant physiologic barrier to DAC oral bioavailability is the enzyme cytidine deaminase (CDA), which is highly expressed in the gut and liver of humans and...