Transcriptional activation of the γ-globin gene in baboons treated with decitabine and in cultured erythroid progenitor cells involves different mechanisms

Chin, Janet; Singh, Mahipal; Banzon, Virryan; Vaitkus, Kestis; Ibanez, Vinzon; Kouznetsova, Tatiana; Mahmud, Nadim; DeSimone, Joseph; Lavelle, Donald

doi:10.1016/j.exphem.2009.06.007

Cited by 22 publications

(25 citation statements)

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“…Comparison of the level of γ-globin synthesis in RN-1-treated baboons with previous results from our laboratory of baboons treated with DNMT inhibitors [3][4][5]12,38,[40][41][42] A. Rivers et al 694 haematologica | 2016; 101(6) …”

Section: Discussionmentioning

confidence: 99%

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The LSD1 inhibitor RN-1 recapitulates the fetal pattern of hemoglobin synthesis in baboons (P. anubis)

et al. 2016

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Section: Discussionmentioning

confidence: 99%

“…4 The ratio of Iγ /Vγ-globin expression is more than 9:5 in early gestational age (50-60dpc) fetuses, 3:2 at birth and 1:2 in the adult. 4,5 Therefore, the developmental pattern of expression of the baboon Iγ-and Vγ-globin genes is very similar to the human Gγ-and Aγ-globin genes ( Figure 1). …”

Section: Introductionmentioning

confidence: 96%

The LSD1 inhibitor RN-1 recapitulates the fetal pattern of hemoglobin synthesis in baboons (P. anubis)

et al. 2016

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“…The differences in our findings may relate to differences in the cell populations analyzed, but also differences in the hydroxyurea dosing and the time of analysis (ie, single large dose versus steady-state MTD). However, compared with known hypomethylating agents such as decitabine and 5-azacitidine that decrease methylation by 40% or more, 39 and given recent data that hypomethylation alone by these agents may not be sufficient for the pharmacologic induction of HbF, 40,41 it is unlikely that the observed small changes in methylation by hydroxyurea is sufficient for HbF induction. Thus methylation patterns of the ␤-globin locus may be a critical regulatory mechanism during normal erythroid cell development, but hypomethylation of the ␥-globin promoter region is probably not an important mechanism of action for hydroxyureamediated induction of HbF.…”

Section: Discussionmentioning

confidence: 99%

Epigenetic and molecular profiles of erythroid cells after hydroxyurea treatment in sickle cell anemia

Walker

Steward²,

Howard

et al. 2011

Blood

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Hydroxyurea has been shown to be efficacious for the treatment of sickle cell anemia (SCA), primarily through the induction of fetal hemoglobin (HbF). However, the exact mechanisms by which hydroxyurea can induce HbF remain incompletely defined, although direct transcriptional effects and altered cell cycle kinetics have been proposed. In this study, we investigated potential epigenetic and alternative molecular mechanisms of hydroxyurea-mediated HbF induction by examining methylation patterns within the G ␥-globin promoter and miRNA expression within primary CD71 ؉ erythrocytes of patients with SCA, both at baseline before beginning hydroxyurea therapy and after reaching maximum tolerated dose (MTD). Using both cross-sectional analysis and paired-sample analysis, we found that the highly methylated G ␥-globin promoter was inversely correlated to baseline HbF levels, but only slightly altered by hydroxyurea treatment. Conversely, expression of several specific miRNAs was significantly increased after hydroxyurea treatment, and expression of miR-26b and miR-151-3p were both associated with HbF levels at MTD. The significant associations identified in these studies suggest that methylation may be important for regulation of baseline HbF, but not after hydroxyurea treatment, whereas changes in miRNA expression may be associated with hydroxyurea-mediated HbF induction. This study was registered at ClinicalTrials.gov (NCT00305175) . IntroductionHydroxyurea is a potent ribonucleotide reductase inhibitor that was initially developed as an antineoplastic agent, but was later found to be beneficial for the treatment of sickle cell anemia (SCA) primarily through its ability to induce fetal hemoglobin (HbF). [1][2][3][4] Clinical trials have proven hydroxyurea to be efficacious in children, adolescents, and adults with SCA for increasing HbF. 2,[5][6][7] Hydroxyurea decreases the number and frequency of vasoocclusive pain crises, episodes of acute chest syndrome, hospitalizations, 6,8-10 and more recently has been shown to also reduce mortality. 11,12 Although highly efficacious for most patients with SCA, there is considerable inter-patient variability creating a broad spectrum of HbF induction. 13,14 HbF induction by cytotoxic drugs, such as hydroxyurea, has been correlated to cell cycle inhibition leading to activation of stress erythropoiesis. [15][16][17] Other studies have suggested that HbF induction by hydroxyurea is mediated more specifically via nitric oxide-dependent transcriptional mechanisms 18,19 and cyclic nucleotides. 20,21 However, the precise mechanisms by which hydroxyurea can induce HbF in patients with SCA remain incompletely defined.Expression of erythroid genes at the ␤-globin locus is developmentally regulated by a complex series of epigenetic and molecular processes. Proposed epigenetic mechanisms of HbF regulation in hemoglobinopathies include methylation, histone deacetylation, and chromosomal looping (reviewed in Sankaran et al, 22 Bank et al, 23 and Stamatoyannopoulos et al 24 ). Methylation i...

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“…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

Blood

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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...

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Transcriptional activation of the γ-globin gene in baboons treated with decitabine and in cultured erythroid progenitor cells involves different mechanisms

Cited by 22 publications

References 51 publications

The LSD1 inhibitor RN-1 recapitulates the fetal pattern of hemoglobin synthesis in baboons (P. anubis)

The LSD1 inhibitor RN-1 recapitulates the fetal pattern of hemoglobin synthesis in baboons (P. anubis)

Epigenetic and molecular profiles of erythroid cells after hydroxyurea treatment in sickle cell anemia

Effects of tetrahydrouridine on pharmacokinetics and pharmacodynamics of oral decitabine

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