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Parker WB, Thottassery JV. 5-Aza-4'-thio-2'-deoxycytidine, a new orally bioavailable non-toxic "best-in-class" DNMT1 depleting agent in clinical development. J Pharmacol Exp Ther 2021; 379:211-222. [PMID: 34503994 DOI: 10.1124/jpet.121.000758] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 09/01/2021] [Indexed: 11/22/2022] Open
Abstract
DNA methyltransferase 1 (DNMT1) is an enzyme that functions as a maintenance methyltransferase during DNA replication, and depletion of this enzyme from cells is considered to be a rational goal in DNA methylation dependent disorders. Two DNMT1 depleting agents aza-dCyd (5-aza-2'-deoxycytidine, decitabine) and aza-Cyd (5-aza-cytidine, azacitidine) are currently used for the treatment of myelodysplastic syndromes and acute myeloid leukemia, and have also been investigated for non-oncology indications such as sickle cell disease. However, these agents have several off-target activities leading to significant toxicities that limit dosing and duration of treatment. Development of more selective inhibitors of DNMT1 could therefore afford treatment for long durations at effective doses. We have discovered that 5-aza-4'-thio-2'-deoxycytidine (aza-T-dCyd) is as effective as aza-dCyd in depleting DNMT1 in mouse tumor models, but with markedly low toxicity. In this review we describe the preclinical studies that led to the development of aza-T-dCyd as a superior DNMT1 depleting agent with respect to aza-dCyd, and will describe its pharmacology, metabolism, and mechanism of action. In an effort to understand why aza-T-dCyd is a more selective DNMT1 depleting agent than aza-dCyd, we will also compare and contrast the activities of these two agents. Significance Statement Aza-T-dCyd is a potent DNMT1 depleting agent. Although similar in structure to decitabine (aza-dCyd) its metabolism and mechanism of action is different than that of aza-dCyd, resulting in less off target activity and less toxicity. The larger therapeutic index of aza-T-dCyd (DNMT1 depletion vs toxicity) in mice suggests that it would be a better clinical candidate to selectively deplete DNMT1 from target cells and determine whether or not depletion of DNMT1 is an effective target for various diseases.
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Tomita T, Kurita R, Onishi Y. Epigenetic regulation of the circadian clock: role of 5-aza-2'-deoxycytidine. Biosci Rep 2017; 37:BSR20170053. [PMID: 28487473 PMCID: PMC5437938 DOI: 10.1042/bsr20170053] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 04/30/2017] [Accepted: 05/08/2017] [Indexed: 12/18/2022] Open
Abstract
We have been investigating transcriptional regulation of the BMAL1 gene, a critical component of the mammalian clock system including DNA methylation. Here, a more detailed analysis of the regulation of DNA methylation of BMAL1 proceeded in RPMI8402 lymphoma cells. We found that CpG islands in the BMAL1 and the PER2 promoters were hyper- and hypomethylated, respectively and that 5-aza-2'-deoxycytidine (aza-dC) not only enhanced PER2 gene expression but also PER2 oscillation within 24 h in RPMI8402 cells. That is, such hypermethylation of CpG islands in the BMAL1 promoter restricted PER2 expression which was recovered by aza-dC within 1 day in these cells. These results suggest that the circadian clock system can be recovered through BMAL1 expression induced by aza-dC within a day. The RPIB9 promoter of RPMI8402 cells, which is a methylation hotspot in lymphoblastic leukemia, was also hypermethylated and aza-dC gradually recovered RPIB9 expression in 3 days. In addition, methylation-specific PCR revealed a different degree of aza-dC-induced methylation release between BMAL1 and RPIB9 These results suggest that the aza-dC-induced recovery of gene expression from DNA methylation is dependent on a gene, for example the rapid response to demethylation by the circadian system, and thus, is of importance to clinical strategies for treating cancer.
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Affiliation(s)
- Tatsunosuke Tomita
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), DBT-AIST International Laboratory for Advanced Biomedicine (DAILAB), Higashi 1-1-1, Tsukuba 305-8566, Japan
| | - Ryoji Kurita
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), DBT-AIST International Laboratory for Advanced Biomedicine (DAILAB), Higashi 1-1-1, Tsukuba 305-8566, Japan
| | - Yoshiaki Onishi
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), DBT-AIST International Laboratory for Advanced Biomedicine (DAILAB), Higashi 1-1-1, Tsukuba 305-8566, Japan
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Rawson JMO, Roth ME, Xie J, Daly MB, Clouser CL, Landman SR, Reilly CS, Bonnac L, Kim B, Patterson SE, Mansky LM. Synergistic reduction of HIV-1 infectivity by 5-azacytidine and inhibitors of ribonucleotide reductase. Bioorg Med Chem 2016; 24:2410-2422. [PMID: 27117260 DOI: 10.1016/j.bmc.2016.03.052] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Revised: 03/18/2016] [Accepted: 03/27/2016] [Indexed: 11/29/2022]
Abstract
Although many compounds have been approved for the treatment of human immunodeficiency type-1 (HIV-1) infection, additional anti-HIV-1 drugs (particularly those belonging to new drug classes) are still needed due to issues such as long-term drug-associated toxicities, transmission of drug-resistant variants, and development of multi-class resistance. Lethal mutagenesis represents an antiviral strategy that has not yet been clinically translated for HIV-1 and is based on the use of small molecules to induce excessive levels of deleterious mutations within the viral genome. Here, we show that 5-azacytidine (5-aza-C), a ribonucleoside analog that induces the lethal mutagenesis of HIV-1, and multiple inhibitors of the enzyme ribonucleotide reductase (RNR) interact in a synergistic fashion to more effectively reduce the infectivity of HIV-1. In these drug combinations, RNR inhibitors failed to significantly inhibit the conversion of 5-aza-C to 5-aza-2'-deoxycytidine, suggesting that 5-aza-C acts primarily as a deoxyribonucleoside even in the presence of RNR inhibitors. The mechanism of antiviral synergy was further investigated for the combination of 5-aza-C and one specific RNR inhibitor, resveratrol, as this combination improved the selectivity index of 5-aza-C to the greatest extent. Antiviral synergy was found to be primarily due to the reduced accumulation of reverse transcription products rather than the enhancement of viral mutagenesis. To our knowledge, these observations represent the first demonstration of antiretroviral synergy between a ribonucleoside analog and RNR inhibitors, and encourage the development of additional ribonucleoside analogs and RNR inhibitors with improved antiretroviral activity.
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Affiliation(s)
- Jonathan M O Rawson
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Molecular, Cellular, Developmental Biology & Genetics Graduate Program, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA
| | - Megan E Roth
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, 515 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Jiashu Xie
- Center for Drug Design, Academic Health Center, University of Minnesota, 516 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Michele B Daly
- Emory Center for AIDS Research, Emory University, 1518 Clifton Road NE, Suite 8050, Atlanta, GA 30322, USA
| | - Christine L Clouser
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, 515 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Sean R Landman
- Department of Computer Science and Engineering, University of Minnesota, 4-192 Keller Hall, 200 Union Street SE, Minneapolis, MN 55455, USA
| | - Cavan S Reilly
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Division of Biostatistics, School of Public Health, University of Minnesota, 420 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Laurent Bonnac
- Center for Drug Design, Academic Health Center, University of Minnesota, 516 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Baek Kim
- Emory Center for AIDS Research, Emory University, 1518 Clifton Road NE, Suite 8050, Atlanta, GA 30322, USA
| | - Steven E Patterson
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Center for Drug Design, Academic Health Center, University of Minnesota, 516 Delaware Street SE, Minneapolis, MN 55455, USA
| | - Louis M Mansky
- Institute for Molecular Virology, University of Minnesota, 18-242 Moos Tower, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, 515 Delaware Street SE, Minneapolis, MN 55455, USA; Department of Microbiology and Immunology, Medical School, University of Minnesota, 689 23rd Avenue SE, Minneapolis, MN 55455, USA; Molecular, Cellular, Developmental Biology & Genetics Graduate Program, University of Minnesota, 321 Church Street SE, Minneapolis, MN 55455, USA; Center for Drug Design, Academic Health Center, University of Minnesota, 516 Delaware Street SE, Minneapolis, MN 55455, USA.
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Epigenetic targeting therapies to overcome chemotherapy resistance. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 754:285-311. [PMID: 22956507 DOI: 10.1007/978-1-4419-9967-2_14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
It is now well established that epigenetic aberrations occur early in malignant transformation, raising the possibility of identifying chemopreventive compounds or reliable diagnostic screening using epigenetic biomarkers. Combinatorial therapies effective for the reexpression of tumor suppressors, facilitating resensitization to conventional chemotherapies, hold great promise for the future therapy of cancer. This approach may also perturb cancer stem cells and thus represent an effective means for managing a number of solid tumors. We believe that in the near future, anticancer drug regimens will routinely include epigenetic therapies, possibly in conjunction with inhibitors of "stemness" signal pathways, to effectively reduce the devastating occurrence of cancer chemotherapy resistance.
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Soleymani Fard S, Jeddi Tehrani M, Ardekani AM. Prostaglandin E2 induces growth inhibition, apoptosis and differentiation in T and B cell-derived acute lymphoblastic leukemia cell lines (CCRF-CEM and Nalm-6). Prostaglandins Leukot Essent Fatty Acids 2012; 87:17-24. [PMID: 22749740 DOI: 10.1016/j.plefa.2012.04.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 04/24/2012] [Accepted: 04/26/2012] [Indexed: 12/23/2022]
Abstract
Despite advances in the treatment of ALL, in most patients long-term survival rates remain unsatisfactory. The objective of the present study was to investigate the anti-cancer effects of Prostaglandin E2 (PGE2) in two different ALL cell lines (CCRF-CEM (T-ALL) and Nalm-6 (B-ALL)). The anti-leukemic effects of PGE2 were also compared with two epigenetic compounds (trichostatin A and 5-aza-2'-deoxycytidine). MTT assay was used to assess growth inhibition by anti-cancer drugs in these cells. All three compounds were shown to induce apoptosis in both ALL cell lines using flow cytometry and Western blotting. To evaluate the differentiation induction by these agents, the expressions of CD19 and CD38 markers on Nalm-6 cell line and CD7 marker on CCRF-CEM cell line were assayed. Surprisingly, the flow cytometric analysis showed a significant increase in CD markers expression in response to PGE2 treatments. We, for the first time, provide evidences that PGE2 has anti-leukemic effects and induces differentiation at micromolar ranges in both T- and B-cell derived ALL cell lines. Since T-ALL cells are insensitive to current chemotherapies, these findings may help the designing of new protocols for T-ALL differentiation therapy in the future.
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Affiliation(s)
- Shahrzad Soleymani Fard
- Reproductive Biotechnology Research Center, Avicenna Research Institute, ACECR, Tehran, Iran
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Bryan J, Kantarjian H, Garcia-Manero G, Jabbour E. Pharmacokinetic evaluation of decitabine for the treatment of leukemia. Expert Opin Drug Metab Toxicol 2011; 7:661-72. [PMID: 21500965 DOI: 10.1517/17425255.2011.575062] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
INTRODUCTION Acute myeloid leukemia (AML) is a life-threatening malignancy that primarily afflicts an elderly population. Treatment of elderly patients with intensive chemotherapy is associated with high treatment-related morbidity and mortality. Therefore, less toxic approaches involving low-dose decitabine-based regimens are being explored in this patient population. AREAS COVERED This drug evaluation article discusses the rationale for targeting aberrant DNA methylation in hematologic malignancies, in particular the myelodysplastic syndromes (MDS) and AML. The authors review the pharmacokinetic data gained from low-dose decitabine, as well as the clinical progress of decitabine in the treatment of hematologic malignancies. Published manuscripts in English were selected from PubMed using a combination of the following search terms: acute myeloid leukemia, pharmacokinetics, decitabine, 5-aza-2'-deoxycytidine, DNA methylation, DNA methyltransferase, myelodysplastic syndrome and leukemia. EXPERT OPINION Decitabine has established efficacy in MDS and shown promising activity in AML at low doses. Given decitabine’s favorable toxicity profile and emerging clinical efficacy, decitabine may be a low intensity therapeutic option for elderly patients with AML who are considered unfit for aggressive chemotherapy.
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Affiliation(s)
- Jeffrey Bryan
- The University of Texas, M.D. Anderson Cancer Center, Department of Leukemia, Houston, TX 77030, USA
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Palii SS, Van Emburgh BO, Sankpal UT, Brown KD, Robertson KD. DNA methylation inhibitor 5-Aza-2'-deoxycytidine induces reversible genome-wide DNA damage that is distinctly influenced by DNA methyltransferases 1 and 3B. Mol Cell Biol 2008; 28:752-71. [PMID: 17991895 PMCID: PMC2223421 DOI: 10.1128/mcb.01799-07] [Citation(s) in RCA: 280] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2007] [Accepted: 10/25/2007] [Indexed: 02/08/2023] Open
Abstract
Genome-wide DNA methylation patterns are frequently deregulated in cancer. There is considerable interest in targeting the methylation machinery in tumor cells using nucleoside analogs of cytosine, such as 5-aza-2'-deoxycytidine (5-azadC). 5-azadC exerts its antitumor effects by reactivation of aberrantly hypermethylated growth regulatory genes and cytoxicity resulting from DNA damage. We sought to better characterize the DNA damage response of tumor cells to 5-azadC and the role of DNA methyltransferases 1 and 3B (DNMT1 and DNMT3B, respectively) in modulating this process. We demonstrate that 5-azadC treatment results in growth inhibition and G(2) arrest-hallmarks of a DNA damage response. 5-azadC treatment led to formation of DNA double-strand breaks, as monitored by formation of gamma-H2AX foci and comet assay, in an ATM (ataxia-telangiectasia mutated)-dependent manner, and this damage was repaired following drug removal. Further analysis revealed activation of key strand break repair proteins including ATM, ATR (ATM-Rad3-related), checkpoint kinase 1 (CHK1), BRCA1, NBS1, and RAD51 by Western blotting and immunofluorescence. Significantly, DNMT1-deficient cells demonstrated profound defects in these responses, including complete lack of gamma-H2AX induction and blunted p53 and CHK1 activation, while DNMT3B-deficient cells generally showed mild defects. We identified a novel interaction between DNMT1 and checkpoint kinase CHK1 and showed that the defective damage response in DNMT1-deficient cells is at least in part due to altered CHK1 subcellular localization. This study therefore greatly enhances our understanding of the mechanisms underlying 5-azadC cytotoxicity and reveals novel functions for DNMT1 as a component of the cellular response to DNA damage, which may help optimize patient responses to this agent in the future.
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Affiliation(s)
- Stela S Palii
- Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Box 100245, 1600 SW Archer Rd., Gainesville, FL 32610, USA
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Abstract
5-Aza-2'-deoxycytidine (decitabine; Dacogen, MGI Pharma, Inc, Bloomington, MN) is a cytidine analog that inhibits DNA methyltransferases resulting in loss of DNA methylation with subsequent gene re-expression. This compound was first synthesized over 40 years ago and since that time much information has been learned regarding its mechanism of action. It took nearly 20 years before the dual mechanism of action was elucidated. At high doses decitabine is cytotoxic, while lower doses are associated with demethylating activity. This information sparked further clinical trials using a lower dosing schedule since the original studies using higher doses were associated with significant myelosuppression and induction toxicity. Current trials using lower dosing schedules, particularly in patients with hematologic malignancies, have shown significant promise for the future use of demethylating agents. Sequential and/or randomized phase I/II studies have suggested that decitabine is most active when administered at relatively low doses given via a short infusion. The drug is less active and more toxic when administered via continuous infusion, and increasing dose-intensity resulted in a higher response rate, suggesting a relationship between peak drug levels and response. Even with all the information we have learned, there is still a need to determine the optimal dosing schedule and the development of alternative dosing forms.
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Affiliation(s)
- Hagop M Kantarjian
- Department of Leukemia, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA.
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Abstract
Myelodysplastic syndromes (MDS) are a heterogenous group of hematopoietic stem cell disorders that are multifactorial in their etiology. Aberrant DNA hypermethylation is now thought to be involved in MDS, as numerous tumor-suppressor genes have been identified that are silenced in these patients. Thus, the use of DNA methyltransferase inhibitors, such as 5-aza-2'-deoxycytidine (decitabine, Dacogen, MGI Pharma Inc, Bloomington, MN), for reversal of this process appears to be a rational intervention that may influence the course of the disease. Several phase I/II studies have been conducted using a low-dose schedule of decitabine in MDS patients. Based on these studies, decitabine appears to be effective and generally well tolerated, especially in those patients with worse prognostic indicators. Recent results of a phase III study also confirmed that patients treated with decitabine compared to standard supportive care had higher overall response rates and longer time to AML transformation. Decitabine appears to be a promising new therapy for the treatment of MDS; however, defining the optimal dosing schedule and exploring the possible use in combination with other agents such as the histone deacetylase inhibitors need further evaluation.
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Affiliation(s)
- Hussain I Saba
- Department of Internal Medicine, University of South Florida College of Medicine, James A Haley Veterans Hospital, Tampa, FL 33612, USA.
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La Rosée P, Johnson K, Corbin AS, Stoffregen EP, Moseson EM, Willis S, Mauro MM, Melo JV, Deininger MW, Druker BJ. In vitro efficacy of combined treatment depends on the underlying mechanism of resistance in imatinib-resistant Bcr-Abl-positive cell lines. Blood 2004; 103:208-15. [PMID: 12933582 DOI: 10.1182/blood-2003-04-1074] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Imatinib mesylate (Gleevec, formerly STI571) is an effective therapy for all stages of chronic myelogenous leukemia (CML). While responses in chronic-phase CML are generally durable, resistance develops in many patients with advanced disease. We evaluated novel antileukemic agents for their potential to overcome resistance in various imatinib-resistant cell lines. Using cell proliferation assays, we investigated whether different mechanisms of resistance to imatinib would alter the efficacy of arsenic trioxide (As2O3) or 5-aza-2-deoxycytidine (decitabine) alone and in combination with imatinib. Our results indicate that resistance to imatinib induced by Bcr-Abl overexpression or by engineered expression of clinically relevant Bcr-Abl mutants does not induce cross-resistance to As2O3 or decitabine. Combined treatment with these agents and imatinib is beneficial in cell lines that have residual sensitivity to imatinib monotherapy, with synergistic growth inhibition achieved only at doses of imatinib that overcome resistance. In some imatinib-resistant cell lines, combination treatments that use low doses of imatinib lead to antagonism. Apoptosis studies suggest that this can be explained in part by the reduced proapoptotic activity of imatinib in resistant cell lines. These data underline the importance of resistance testing and provide a rational approach for dose-adjusted administration of imatinib when combined with other agents.
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MESH Headings
- Antineoplastic Combined Chemotherapy Protocols/administration & dosage
- Arsenic Trioxide
- Arsenicals/administration & dosage
- Azacitidine/administration & dosage
- Azacitidine/analogs & derivatives
- Base Sequence
- Benzamides
- Cell Division/drug effects
- Cell Line, Tumor
- DNA, Neoplasm/genetics
- Decitabine
- Drug Resistance, Neoplasm
- Drug Synergism
- Enzyme Inhibitors/administration & dosage
- Enzyme Inhibitors/pharmacology
- Fusion Proteins, bcr-abl
- Genes, abl
- Humans
- Imatinib Mesylate
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/drug therapy
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/enzymology
- Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics
- Oxides/administration & dosage
- Piperazines/administration & dosage
- Piperazines/pharmacology
- Protein-Tyrosine Kinases/antagonists & inhibitors
- Protein-Tyrosine Kinases/metabolism
- Pyrimidines/administration & dosage
- Pyrimidines/pharmacology
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Affiliation(s)
- Paul La Rosée
- Oregon Health and Science University Cancer Institute, Division of Hematology and Medical Oncology, Portland, OR 97239, USA
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Rosen MB, Chernoff N. 5-Aza-2'-deoxycytidine-induced cytotoxicity and limb reduction defects in the mouse. TERATOLOGY 2002; 65:180-90. [PMID: 11948564 DOI: 10.1002/tera.10029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND 5-Aza-2'-deoxycytidine (dAZA), causes hindlimb phocomelia in CD-1 mice. Studies in our laboratory have examined the hypothesis that compound- induced changes in gene expression may uniquely affect hindlimb pattern formation. The present study tests the hypothesis that dAZA causes limb dysplasia by inducing cytotoxicity among rapidly proliferating cells in the limb bud mesenchyme. METHODS Pregnant CD-1 mice were given a teratogenic dose of dAZA (i.p.) at different times on GD 10 and fetuses evaluated for skeletal development in both sets of limbs by standard methods. Using general histology and BrdU immunohistochemistry, limb mesenchymal cell death and cell proliferation were then assessed in embryos at various times post dosing, shortly after initial limb bud outgrowth. The effect of dAZA on early limb chondrogenesis was also studied using Northern analysis of scleraxis and Alcian blue staining of whole mount limb buds. RESULTS Compound related hindlimb defects were not restricted to a specific set of skeletal elements but consisted of a range of temporally related limb anomalies. Modest defects of the radius were observed as well. These results are consistent with a general insult to the limb mesenchyme. Mesenchymal cell death and reduced cell proliferation were also observed in both sets of limbs. The timing and location of these effects indicate a role for cytotoxicity in the etiology of dAZA induced limb defects. These effects also agree with the greater teratogenicity of dAZA in the hindlimb because they were more pronounced in that limb. The expression of scleraxis, a marker of early chondrogenesis, was reduced 12 hr after dAZA exposure, a time coincident with maximal cell death, as was the subsequent emergence of Alcian blue stained long bone anlagen. CONCLUSIONS These findings support the hypothesis that cytotoxic changes in the limb bud mesenchyme during early limb outgrowth can induce the proximal limb truncations characteristic of phocomelia after dAZA administration.
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Affiliation(s)
- Mitchell B Rosen
- U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Reproductive Toxicology Division, Research Triangle Park, North Carolina 27711, USA.
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Rietveld LE, Caldenhoven E, Stunnenberg HG. Avian erythroleukemia: a model for corepressor function in cancer. Oncogene 2001; 20:3100-9. [PMID: 11420726 DOI: 10.1038/sj.onc.1204335] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Transcriptional regulation at the level of chromatin plays crucial roles during eukaryotic development and differentiation. A plethora of studies revealed that the acetylation status of histones is controlled by multi-protein complexes containing (de)acetylase activities. In the current model, histone deacetylases and acetyltransferases are recruited to chromatin by DNA-bound repressors and activators, respectively. Shifting the balance between deacetylation, i.e. repressive chromatin and acetylation, i.e. active chromatin can lead to aberrant gene transcription and cancer. In human acute promyelocytic leukemia (APL) and avian erythroleukemia (AEL), chromosomal translocations and/or mutations in nuclear hormone receptors, RARalpha [NR1B1] and TRalpha [NR1A1], yielded oncoproteins that deregulate transcription and alter chromatin structure. The oncogenic receptors are locked in their 'off' mode thereby constitutively repressing transcription of genes that are critical for differentiation of hematopoietic cells. AEL involves an oncogenic version of the chicken TRalpha, v-ErbA. Apart from repression by v-ErbA via recruitment of corepressor complexes, other repressors and corepressors appear to be involved in repression of v-ErbA target genes, such as carbonic anhydrase II (CAII). Reactivation of repressed genes in APL and AEL by chromatin modifying agents such as inhibitors of histone deacetylase or of methylation provides new therapeutic strategies in the treatment of acute myeloid leukemia.
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Affiliation(s)
- L E Rietveld
- Department of Molecular Biology, NCMLS, Geert Grooteplein Zuid 26, PO Box 9101 6500 HB Nijmegen, The Netherlands
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Podolyan Y, Rubin YV, Leszczynski J. An ab Initio Post-Hartree−Fock Comparative Study of 5-Azacytosine and Cytosine and Their Dimers with Guanine. J Phys Chem A 2000. [DOI: 10.1021/jp0015271] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yevgeniy Podolyan
- Computational Center for Molecular Structure and Interactions, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, and B. Verkin Institute for Low-Temperature Physics and Engineering, National Academy of Sciences, Kharkov, 310164, Ukraine
| | - Yury V. Rubin
- Computational Center for Molecular Structure and Interactions, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, and B. Verkin Institute for Low-Temperature Physics and Engineering, National Academy of Sciences, Kharkov, 310164, Ukraine
| | - Jerzy Leszczynski
- Computational Center for Molecular Structure and Interactions, Department of Chemistry, Jackson State University, Jackson, Mississippi 39217, and B. Verkin Institute for Low-Temperature Physics and Engineering, National Academy of Sciences, Kharkov, 310164, Ukraine
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Jackson-Grusby L, Laird PW, Magge SN, Moeller BJ, Jaenisch R. Mutagenicity of 5-aza-2'-deoxycytidine is mediated by the mammalian DNA methyltransferase. Proc Natl Acad Sci U S A 1997; 94:4681-5. [PMID: 9114051 PMCID: PMC20784 DOI: 10.1073/pnas.94.9.4681] [Citation(s) in RCA: 151] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The cytosine analog 5-aza-2'-deoxycytidine has been used clinically to reactivate genes silenced by DNA methylation. In particular, patients with beta-thalassemia show fetal globin expression after administration of this hypomethylating drug. In addition, silencing of tumor suppressor gene expression by aberrant DNA methylation in tumor cells may potentially be reversed by a similar regimen. Consistent with its function in maintaining tumor suppressor gene expression, 5-aza-2'-deoxycytidine significantly reduces intestinal tumor multiplicity in the predisposed Min mouse strain. Despite its utility as an anti-cancer agent, the drug is highly mutagenic by an unknown mechanism. To gain insight into how 5-aza-2'-deoxycytidine induces mutations in vivo, we examined the mutational spectrum in an Escherichia coli lac I transgene in colonic DNA from 5-aza-2'-deoxycytidine-treated mice. Mutations induced by 5-aza-2'-deoxycytidine were predominantly at CpG dinucleotides, which implicates DNA methyltransferase in the mutagenic mechanism. C:G-->G:C transversions were the predominant class of mutations observed. We suggest a model for how the mammalian DNA methyltransferase may be involved in facilitating these mutations. The observation that 5-aza-2'-deoxycytidine-induced mutations are mediated by the enzyme suggests that novel inhibitors of DNA methyltransferase, which can inactivate the enzyme before its interaction with DNA, are needed for chemoprevention or long term therapy.
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Affiliation(s)
- L Jackson-Grusby
- Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Nine Cambridge Center, Cambridge, MA 02142, USA
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