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Marx N, Eisenhut P, Weinguny M, Klanert G, Borth N. How to train your cell - Towards controlling phenotypes by harnessing the epigenome of Chinese hamster ovary production cell lines. Biotechnol Adv 2022; 56:107924. [PMID: 35149147 DOI: 10.1016/j.biotechadv.2022.107924] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 02/03/2022] [Accepted: 02/04/2022] [Indexed: 11/24/2022]
Abstract
Recent advances in omics technologies and the broad availability of big datasets have revolutionized our understanding of Chinese hamster ovary cells in their role as the most prevalent host for production of complex biopharmaceuticals. In consequence, our perception of this "workhorse of the biopharmaceutical industry" has successively shifted from that of a nicely working, but unknown recombinant protein producing black box to a biological system governed by multiple complex regulatory layers that might possibly be harnessed and manipulated at will. Despite the tremendous progress that has been made to characterize CHO cells on various omics levels, our understanding is still far from complete. The well-known inherent genetic plasticity of any immortalized and rapidly dividing cell line also characterizes CHO cells and can lead to problematic instability of recombinant protein production. While the high mutational frequency has been a focus of CHO cell research for decades, the impact of epigenetics and its role in differential gene expression has only recently been addressed. In this review we provide an overview about the current understanding of epigenetic regulation in CHO cells and discuss its significance for shaping the cell's phenotype. We also look into current state-of-the-art technology that can be applied to harness and manipulate the epigenetic network so as to nudge CHO cells towards a specific phenotype. Here, we revise current strategies on site-directed integration and random as well as targeted epigenome modifications. Finally, we address open questions that need to be investigated to exploit the full repertoire of fine-tuned control of multiplexed gene expression using epigenetic and systems biology tools.
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Affiliation(s)
- Nicolas Marx
- University of Natural Resources and Life Sciences, Vienna, Austria
| | - Peter Eisenhut
- Austrian Centre for Industrial Biotechnology GmbH, Vienna, Austria
| | - Marcus Weinguny
- University of Natural Resources and Life Sciences, Vienna, Austria; Austrian Centre for Industrial Biotechnology GmbH, Vienna, Austria
| | - Gerald Klanert
- Austrian Centre for Industrial Biotechnology GmbH, Vienna, Austria
| | - Nicole Borth
- University of Natural Resources and Life Sciences, Vienna, Austria; Austrian Centre for Industrial Biotechnology GmbH, Vienna, Austria.
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Weinguny M, Eisenhut P, Klanert G, Virgolini N, Marx N, Jonsson A, Ivansson D, Lövgren A, Borth N. Random epigenetic modulation of CHO cells by repeated knockdown of DNA methyltransferases increases population diversity and enables sorting of cells with higher production capacities. Biotechnol Bioeng 2020; 117:3435-3447. [PMID: 32662873 PMCID: PMC7818401 DOI: 10.1002/bit.27493] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2020] [Revised: 05/25/2020] [Accepted: 07/12/2020] [Indexed: 12/15/2022]
Abstract
Chinese hamster ovary (CHO) cells produce a large share of today's biopharmaceuticals. Still, the generation of satisfactory producer cell lines is a tedious undertaking. Recently, it was found that CHO cells, when exposed to new environmental conditions, modify their epigenome, suggesting that cells adapt their gene expression pattern to handle new challenges. The major aim of the present study was to employ artificially induced, random changes in the DNA-methylation pattern of CHO cells to diversify cell populations and consequently increase the finding of cell lines with improved cellular characteristics. To achieve this, DNA methyltransferases and/or the ten-eleven translocation enzymes were downregulated by RNA interference over a time span of ∼16 days. Methylation analysis of the resulting cell pools revealed that the knockdown of DNA methyltransferases was highly effective in randomly demethylating the genome. The same approach, when applied to stable CHO producer cells resulted in (a) an increased productivity diversity in the cell population, and (b) a higher number of outliers within the population, which resulted in higher specific productivity and titer in the sorted cells. These findings suggest that epigenetics play a previously underestimated, but actually important role in defining the overall cellular behavior of production clones.
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Affiliation(s)
- Marcus Weinguny
- ACIB—Austrian Centre of Industrial BiotechnologyGrazAustria,Department of BiotechnologyUniversity of Natural Resources and Life SciencesViennaAustria
| | - Peter Eisenhut
- ACIB—Austrian Centre of Industrial BiotechnologyGrazAustria,Department of BiotechnologyUniversity of Natural Resources and Life SciencesViennaAustria
| | - Gerald Klanert
- ACIB—Austrian Centre of Industrial BiotechnologyGrazAustria
| | | | - Nicolas Marx
- ACIB—Austrian Centre of Industrial BiotechnologyGrazAustria,Department of BiotechnologyUniversity of Natural Resources and Life SciencesViennaAustria
| | | | | | | | - Nicole Borth
- ACIB—Austrian Centre of Industrial BiotechnologyGrazAustria,Department of BiotechnologyUniversity of Natural Resources and Life SciencesViennaAustria
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Hsu CW, Hewes KP, Stavitskaya L, Kruhlak NL. Construction and application of (Q)SAR models to predict chemical-induced in vitro chromosome aberrations. Regul Toxicol Pharmacol 2018; 99:274-288. [PMID: 30278198 DOI: 10.1016/j.yrtph.2018.09.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 09/24/2018] [Accepted: 09/26/2018] [Indexed: 12/23/2022]
Abstract
In drug development, genetic toxicology studies are conducted using in vitro and in vivo assays to identify potential mutagenic and clastogenic effects, as outlined in the International Council for Harmonisation (ICH) S2 regulatory guideline. (Quantitative) structure-activity relationship ((Q)SAR) models that predict assay outcomes can be used as an early screen to prioritize pharmaceutical candidates, or later during product development to evaluate safety when experimental data are unavailable or inconclusive. In the current study, two commercial QSAR platforms were used to build models for in vitro chromosomal aberrations in Chinese hamster lung (CHL) and Chinese hamster ovary (CHO) cells. Cross-validated CHL model predictive performance showed sensitivity of 80 and 82%, and negative predictivity of 75 and 76% based on 875 training set compounds. For CHO, sensitivity of 61 and 67% and negative predictivity of 68 and 74% was achieved based on 817 training set compounds. The predictive performance of structural alerts in a commercial expert rule-based SAR software was also investigated and showed positive predictivity of 48-100% for selected alerts. Case studies examining incorrectly-predicted compounds, non-DNA-reactive clastogens, and recently-approved pharmaceuticals are presented, exploring how an investigational approach using similarity searching and expert knowledge can improve upon individual (Q)SAR predictions of the clastogenicity of drugs.
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Affiliation(s)
- Chia-Wen Hsu
- US Food and Drug Administration, Center for Drug Evaluation and Research, Silver Spring, MD, USA
| | - Kurt P Hewes
- US Food and Drug Administration, Center for Drug Evaluation and Research, Silver Spring, MD, USA
| | - Lidiya Stavitskaya
- US Food and Drug Administration, Center for Drug Evaluation and Research, Silver Spring, MD, USA
| | - Naomi L Kruhlak
- US Food and Drug Administration, Center for Drug Evaluation and Research, Silver Spring, MD, USA.
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An Initial Investigation of an Alternative Model to Study rat Primordial Germ Cell Epigenetic Reprogramming. Biol Proced Online 2017; 19:9. [PMID: 28785173 PMCID: PMC5541664 DOI: 10.1186/s12575-017-0058-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 07/14/2017] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND Primordial germ cells (PGC) are the precursors of the gametes. During pre-natal development, PGC undergo an epigenetic reprogramming when bulk DNA demethylation occurs and is followed by sex-specific de novo methylation. The de novo methylation and the maintenance of the methylation patterns depend on DNA methyltransferases (DNMTs). PGC reprogramming has been widely studied in mice but not in rats. We have previously shown that the rat might be an interesting model to study germ cell development. In face of the difficulties of getting enough PGC for molecular studies, the aim of this study was to propose an alternative method to study rat PGC DNA methylation. Rat embryos were collected at 14, 15 and 19 days post-coitus (dpc) for the analysis of 5mC, 5hmC, DNMT1, DNMT3a and DNMT3b expression or at 16dpc for treatment 5-Aza-CdR, a DNMT inhibitor, in vitro. METHODS Once collected, the gonads were placed in 24-well plates previously containing 45μm pore membrane and medium with or without 5-Aza-CdR. The culture was kept for five days and medium was changed daily. The gonads were either fixed or submitted to RNA extraction. RESULTS 5mC and DNMTs labelling suggests that PGC are undergoing epigenetic reprogramming around 14/15dpc. The in vitro treatment of rat embryonic gonads with 1 μM of 5-Aza-CdR lead to a loss of 5mC labelling and to the activation of Pax6 expression in PGC, but not in somatic cells, suggesting that 5-Aza-CdR promoted a PGC-specific global DNA hypomethylation. CONCLUSIONS This study suggests that the protocol used here can be a potential method to study the wide DNA demethylation that takes place during PGC reprogramming.
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Brevini T, Pennarossa G, Acocella F, Brizzola S, Zenobi A, Gandolfi F. Epigenetic conversion of adult dog skin fibroblasts into insulin-secreting cells. Vet J 2016; 211:52-6. [DOI: 10.1016/j.tvjl.2016.02.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 01/29/2016] [Accepted: 02/27/2016] [Indexed: 12/15/2022]
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Liu K, Liu Y, Lau JL, Min J. Epigenetic targets and drug discovery Part 2: Histone demethylation and DNA methylation. Pharmacol Ther 2015; 151:121-40. [PMID: 25857453 DOI: 10.1016/j.pharmthera.2015.04.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 03/31/2015] [Indexed: 02/06/2023]
Abstract
Chromatin structure is dynamically modulated by various chromatin modifications, such as histone/DNA methylation and demethylation. We have reviewed histone methyltransferases and methyllysine binders in terms of small molecule screening and drug discovery in the first part of this review series. In this part, we will summarize recent progress in chemical probe and drug discovery of histone demethylases and DNA methyltransferases. Histone demethylation and DNA methylation have attracted a lot of attention regarding their biology and disease implications. Correspondingly, many small molecule compounds have been designed to modulate the activity of histone demethylases and DNA methyltransferases, and some of them have been developed into therapeutic drugs or put into clinical trials.
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Affiliation(s)
- Ke Liu
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Science, Central China Normal University, Wuhan 430079, PR China; Structural Genomics Consortium, University of Toronto, 101 College Street, Toronto, Ontario M5G 1L7, Canada
| | - Yanli Liu
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Science, Central China Normal University, Wuhan 430079, PR China; Structural Genomics Consortium, University of Toronto, 101 College Street, Toronto, Ontario M5G 1L7, Canada
| | - Johnathan L Lau
- Structural Genomics Consortium, University of Toronto, 101 College Street, Toronto, Ontario M5G 1L7, Canada; Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Jinrong Min
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Science, Central China Normal University, Wuhan 430079, PR China; Structural Genomics Consortium, University of Toronto, 101 College Street, Toronto, Ontario M5G 1L7, Canada; Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
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Ulahannan N, Greally JM. Genome-wide assays that identify and quantify modified cytosines in human disease studies. Epigenetics Chromatin 2015; 8:5. [PMID: 25788985 PMCID: PMC4363328 DOI: 10.1186/1756-8935-8-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 01/05/2015] [Indexed: 12/23/2022] Open
Abstract
The number of different assays that has been published to study DNA methylation is extensive, complemented by recently described assays that test modifications of cytosine other than the most abundant 5-methylcytosine (5mC) variant. In this review, we describe the considerations involved in choosing how to study 5mC throughout the genome, with an emphasis on the common application of testing for epigenetic dysregulation in human disease. While microarray studies of 5mC continue to be commonly used, these lack the additional qualitative information from sequencing-based approaches that is increasingly recognized to be valuable. When we test the representation of functional elements in the human genome by several current assay types, we find that no survey approach interrogates anything more than a small minority of the nonpromoter cis-regulatory sites where DNA methylation variability is now appreciated to influence gene expression and to be associated with human disease. However, whole-genome bisulphite sequencing (WGBS) adds a substantial representation of loci at which DNA methylation changes are unlikely to be occurring with transcriptional consequences. Our assessment is that the most effective approach to DNA methylation studies in human diseases is to use targeted bisulphite sequencing of the cis-regulatory loci in a cell type of interest, using a capture-based or comparable system, and that no single design of a survey approach will be suitable for all cell types.
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Affiliation(s)
- Netha Ulahannan
- Department of Genetics, Albert Einstein College of Medicine, Center for Epigenomics and Division of Computational Genetics, 1301 Morris Park Avenue, Bronx, NY 10461 USA
| | - John M Greally
- Department of Genetics, Albert Einstein College of Medicine, Center for Epigenomics and Division of Computational Genetics, 1301 Morris Park Avenue, Bronx, NY 10461 USA
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Zych J, Stimamiglio MA, Senegaglia AC, Brofman PRS, Dallagiovanna B, Goldenberg S, Correa A. The epigenetic modifiers 5-aza-2'-deoxycytidine and trichostatin A influence adipocyte differentiation in human mesenchymal stem cells. Braz J Med Biol Res 2014; 46:405-16. [PMID: 23797495 PMCID: PMC3854397 DOI: 10.1590/1414-431x20132893] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2012] [Accepted: 03/11/2013] [Indexed: 01/10/2023] Open
Abstract
Epigenetic mechanisms such as DNA methylation and histone modification are
important in stem cell differentiation. Methylation is principally associated
with transcriptional repression, and histone acetylation is correlated with an
active chromatin state. We determined the effects of these epigenetic mechanisms
on adipocyte differentiation in mesenchymal stem cells (MSCs) derived from bone
marrow (BM-MSCs) and adipose tissue (ADSCs) using the chromatin-modifying agents
trichostatin A (TSA), a histone deacetylase inhibitor, and
5-aza-2′-deoxycytidine (5azadC), a demethylating agent. Subconfluent MSC
cultures were treated with 5, 50, or 500 nM TSA or with 1, 10, or
100 µM 5azadC for 2 days before the initiation of adipogenesis. The
differentiation was quantified and expression of the adipocyte genes PPARG and
FABP4 and of the anti-adipocyte gene GATA2 was evaluated. TSA decreased
adipogenesis, except in BM-MSCs treated with 5 nM TSA. Only treatment
with 500 nM TSA decreased cell proliferation. 5azadC treatment decreased
proliferation and adipocyte differentiation in all conditions evaluated,
resulting in the downregulation of PPARG and FABP4 and the upregulation of
GATA2. The response to treatment was stronger in ADSCs than in BM-MSCs,
suggesting that epigenetic memories may differ between cells of different
origins. As epigenetic signatures affect differentiation, it should be possible
to direct the use of MSCs in cell therapies to improve process efficiency by
considering the various sources available.
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Affiliation(s)
- J Zych
- Laboratório de Biologia Básica de Células-Tronco, Instituto Carlos Chagas, FIOCRUZ, Curitiba, PR, Brasil.
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Reprogramming of Pig Dermal Fibroblast into Insulin Secreting Cells by a Brief Exposure to 5-aza-cytidine. Stem Cell Rev Rep 2013; 10:31-43. [DOI: 10.1007/s12015-013-9477-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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Abstract
DNA hypomethylation was the initial epigenetic abnormality recognized in human tumors. However, for several decades after its independent discovery by two laboratories in 1983, it was often ignored as an unwelcome complication, with almost all of the attention on the hypermethylation of promoters of genes that are silenced in cancers (e.g., tumor-suppressor genes). Because it was subsequently shown that global hypomethylation of DNA in cancer was most closely associated with repeated DNA elements, cancer linked-DNA hypomethylation continued to receive rather little attention. DNA hypomethylation in cancer can no longer be considered an oddity, because recent high-resolution genome-wide studies confirm that DNA hypomethylation is the almost constant companion to hypermethylation of the genome in cancer, just usually (but not always) in different sequences. Methylation changes at individual CpG dyads in cancer can have a high degree of dependence not only on the regional context, but also on neighboring sites. DNA demethylation during carcinogenesis may involve hemimethylated dyads as intermediates, followed by spreading of the loss of methylation on both strands. In this review, active demethylation of DNA and the relationship of cancer-associated DNA hypomethylation to cancer stem cells are discussed. Evidence is accumulating for the biological significance and clinical relevance of DNA hypomethylation in cancer, and for cancer-linked demethylation and de novo methylation being highly dynamic processes.
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Affiliation(s)
- Melanie Ehrlich
- Hayward Genetics Program, Department of Biochemistry, Tulane Cancer Center, Tulane Medical School, 1430 TulaneAvenue, New Orleans, LA 70112, USA.
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Lim SP, Neilsen P, Kumar R, Abell A, Callen DF. The Application of Delivery Systems for DNA Methyltransferase Inhibitors. BioDrugs 2011; 25:227-42. [DOI: 10.2165/11592770-000000000-00000] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Kongruttanachok N, Phuangphairoj C, Thongnak A, Ponyeam W, Rattanatanyong P, Pornthanakasem W, Mutirangura A. Replication independent DNA double-strand break retention may prevent genomic instability. Mol Cancer 2010; 9:70. [PMID: 20356374 PMCID: PMC2867818 DOI: 10.1186/1476-4598-9-70] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2009] [Accepted: 03/31/2010] [Indexed: 01/16/2023] Open
Abstract
Background Global hypomethylation and genomic instability are cardinal features of cancers. Recently, we established a method for the detection of DNA methylation levels at sites close to endogenous DNA double strand breaks (EDSBs), and found that those sites have a higher level of methylation than the rest of the genome. Interestingly, the most significant differences between EDSBs and genomes were observed when cells were cultured in the absence of serum. DNA methylation levels on each genomic location are different. Therefore, there are more replication-independent EDSBs (RIND-EDSBs) located in methylated genomic regions. Moreover, methylated and unmethylated RIND-EDSBs are differentially processed. Euchromatins respond rapidly to DSBs induced by irradiation with the phosphorylation of H2AX, γ-H2AX, and these initiate the DSB repair process. During G0, most DSBs are repaired by non-homologous end-joining repair (NHEJ), mediated by at least two distinct pathways; the Ku-mediated and the ataxia telangiectasia-mutated (ATM)-mediated. The ATM-mediated pathway is more precise. Here we explored how cells process methylated RIND-EDSBs and if RIND-EDSBs play a role in global hypomethylation-induced genomic instability. Results We observed a significant number of methylated RIND-EDSBs that are retained within deacetylated chromatin and free from an immediate cellular response to DSBs, the γ-H2AX. When cells were treated with tricostatin A (TSA) and the histones became hyperacetylated, the amount of γ-H2AX-bound DNA increased and the retained RIND-EDSBs were rapidly repaired. When NHEJ was simultaneously inhibited in TSA-treated cells, more EDSBs were detected. Without TSA, a sporadic increase in unmethylated RIND-EDSBs could be observed when Ku-mediated NHEJ was inhibited. Finally, a remarkable increase in RIND-EDSB methylation levels was observed when cells were depleted of ATM, but not of Ku86 and RAD51. Conclusions Methylated RIND-EDSBs are retained in non-acetylated heterochromatin because there is a prolonged time lag between RIND-EDSB production and repair. The rapid cellular responses to DSBs may be blocked by compact heterochromatin structure which then allows these breaks to be repaired by a more precise ATM-dependent pathway. In contrast, Ku-mediated NHEJ can repair euchromatin-associated EDSBs. Consequently, spontaneous mutations in hypomethylated genome are produced at faster rates because unmethylated EDSBs are unable to avoid the more error-prone NHEJ mechanisms.
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Affiliation(s)
- Narisorn Kongruttanachok
- Center of Excellence in Molecular Genetics of Cancer and Human Diseases, Department of Anatomy, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand
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LIM HW, IWATANI M, HATTORI N, TANAKA S, YAGI S, SHIOTA K. Resistance to 5-aza-2'-deoxycytidine in Genic Regions Compared to Non-genic Repetitive Sequences. J Reprod Dev 2010; 56:86-93. [DOI: 10.1262/jrd.20247] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Hui Wen LIM
- Laboratory of Cellular Biochemistry, Animal Resource Sciences/Veterinary Medical Sciences, The University of Tokyo
| | - Misa IWATANI
- Laboratory of Cellular Biochemistry, Animal Resource Sciences/Veterinary Medical Sciences, The University of Tokyo
| | - Naoko HATTORI
- Laboratory of Cellular Biochemistry, Animal Resource Sciences/Veterinary Medical Sciences, The University of Tokyo
| | - Satoshi TANAKA
- Laboratory of Cellular Biochemistry, Animal Resource Sciences/Veterinary Medical Sciences, The University of Tokyo
| | - Shintaro YAGI
- Laboratory of Cellular Biochemistry, Animal Resource Sciences/Veterinary Medical Sciences, The University of Tokyo
| | - Kunio SHIOTA
- Laboratory of Cellular Biochemistry, Animal Resource Sciences/Veterinary Medical Sciences, The University of Tokyo
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Fan H, Cheng J, Zhao ZJ. Inhibition of de novo Methyltransferase 3B is a Potential Therapy for Hepatocellular Carcinoma. Gastroenterology Res 2008; 1:33-39. [PMID: 27994704 PMCID: PMC5154213 DOI: 10.4021/gr2008.10.1240] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2008] [Accepted: 11/06/2008] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND Aberrant epigenetic patterns, including inactivation of tumor suppressor genes due to DNA methylation, have been described in many human cancers. Epigenetic therapeutic is a new and rapidly developing area of tumor treatment because DNA methyltransferase (DNMT) inhibitors can reverse its changes. We attempted to identify potential approach for epigenetic therapy of hepatocellular carcinoma. METHODS We knocked down the expression of DNMT 1 or DNMT 3B by siRNA, and inhibited DNA methyltranferases by 5-Aza-2'-deoxycytidine. We used high-density oligonucleotide gene expression microarrays to examine the induced genes in human hepatocellular carcinoma cell line SMMC-7721 after suppressing DNA methyltranferases. The 5' ends of up-regulated genes were analyzed by BLAST database to determine whether they have promoter CpG islands, and then the identical induced genes were compared among different inhibition of DNA methyltranferases. RESULTS Our results show that 9 genes were found to be over expressed by more than two-fold induced by DNMT1 siRNA and 5-Aza-CdR, and 30 genes were found to be over expressed by more than two-fold induced by DNMT3B siRNA and 5-Aza-CdR in SMMC-7721. Among them, 76.6% up-regulated genes conjectural contained 5' CpG islands. The DNMT3B siRNA could induce more genes identical to demethylation agent in SMMC-7721. CONCLUSIONS DNMT3B might be a new potential target for therapy of hepatocellular carcinoma.
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Affiliation(s)
- Hong Fan
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Southeast University; Department of Genetics and Development, Southeast University Medical School. 87 Dingjiaqiao, Nanjing 210009, Jiangsu Province, China
| | - Jian Cheng
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Southeast University; Department of Genetics and Development, Southeast University Medical School. 87 Dingjiaqiao, Nanjing 210009, Jiangsu Province, China
| | - Zhu Jiang Zhao
- Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Southeast University; Department of Genetics and Development, Southeast University Medical School. 87 Dingjiaqiao, Nanjing 210009, Jiangsu Province, China
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Byun HM, Choi SH, Laird PW, Trinh B, Siddiqui MA, Marquez VE, Yang AS. 2'-Deoxy-N4-[2-(4-nitrophenyl)ethoxycarbonyl]-5-azacytidine: a novel inhibitor of DNA methyltransferase that requires activation by human carboxylesterase 1. Cancer Lett 2008; 266:238-48. [PMID: 18499340 DOI: 10.1016/j.canlet.2008.02.069] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Revised: 02/25/2008] [Accepted: 02/26/2008] [Indexed: 11/30/2022]
Abstract
2'-Deoxy-N4-[2-(4-nitrophenyl)ethoxycarbonyl]-5-azacytidine (NPEOC-DAC), decitabine with a modification of the N4 position of the azacitidine ring can be used to inhibit DNA methyltransferase. This modification protects the azacitidine ring and can be cleaved by carboxylesterase to release decitabine. NPEOC-DAC was 23-fold less potent at low doses (<10microM) than decitabine at inhibiting DNA methylation, and was also associated with a 3-day delay in its effect. However, at doses > or = 10microM NPEOC-DAC was more effective at inhibiting DNA methylation. Theses differences between decitabine and NPEOC-DAC are dependent on the cleavage of the carboxylester bond, and could be potentially exploited pharmacologically.
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Affiliation(s)
- Hyang-Min Byun
- Division of Hematology, University of Southern California/Norris Comprehensive Cancer Center, 1441 Eastlake Avenue, Room 6428, Los Angeles, CA, USA
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Kiziltepe T, Hideshima T, Catley L, Raje N, Yasui H, Shiraishi N, Okawa Y, Ikeda H, Vallet S, Pozzi S, Ishitsuka K, Ocio EM, Chauhan D, Anderson KC. 5-Azacytidine, a DNA methyltransferase inhibitor, induces ATR-mediated DNA double-strand break responses, apoptosis, and synergistic cytotoxicity with doxorubicin and bortezomib against multiple myeloma cells. Mol Cancer Ther 2007; 6:1718-27. [PMID: 17575103 DOI: 10.1158/1535-7163.mct-07-0010] [Citation(s) in RCA: 134] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
In this study, we investigated the cytotoxicity of 5-azacytidine, a DNA methyltransferase inhibitor, against multiple myeloma (MM) cells, and characterized DNA damage-related mechanisms of cell death. 5-Azacytidine showed significant cytotoxicity against both conventional therapy-sensitive and therapy-resistant MM cell lines, as well as multidrug-resistant patient-derived MM cells, with IC(50) of approximately 0.8-3 micromol/L. Conversely, 5-azacytidine was not cytotoxic to peripheral blood mononuclear cells or patient-derived bone marrow stromal cells (BMSC) at these doses. Importantly, 5-azacytidine overcame the survival and growth advantages conferred by exogenous interleukin-6 (IL-6), insulin-like growth factor-I (IGF-I), or by adherence of MM cells to BMSCs. 5-Azacytidine treatment induced DNA double-strand break (DSB) responses, as evidenced by H2AX, Chk2, and p53 phosphorylations, and apoptosis of MM cells. 5-Azacytidine-induced apoptosis was both caspase dependent and independent, with caspase 8 and caspase 9 cleavage; Mcl-1 cleavage; Bax, Puma, and Noxa up-regulation; as well as release of AIF and EndoG from the mitochondria. Finally, we show that 5-azacytidine-induced DNA DSB responses were mediated predominantly by ATR, and that doxorubicin, as well as bortezomib, synergistically enhanced 5-azacytidine-induced MM cell death. Taken together, these data provide the preclinical rationale for the clinical evaluation of 5-azacytidine, alone and in combination with doxorubicin and bortezomib, to improve patient outcome in MM.
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Affiliation(s)
- Tanyel Kiziltepe
- Jerome Lipper Multiple Myeloma Center, Department of Medical Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts 02115, USA.
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17
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Seth G, Ozturk M, Hu WS. Reverting cholesterol auxotrophy of NS0 cells by altering epigenetic gene silencing. Biotechnol Bioeng 2006; 93:820-7. [PMID: 16189819 DOI: 10.1002/bit.20720] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
NS0 is a cholesterol-requiring mouse myeloma cell line widely used in the production of recombinant antibodies. We have previously reported that the deficiency of 17beta-hydroxysteroid dehydrogenase type7 (Hsd17b7) is responsible for the cholesterol auxotrophy of NS0 cells. Here we demonstrate DNA methylation to be the mechanism underlying transcriptional suppression of Hsd17b7 in cholesterol dependent NS0 cells. Analysis of the DNA methylation pattern revealed methylation of the CpG-rich region upstream of the Hsd17b7 transcription start site in NS0 cells. This is in contrast to the unmethylated status of this sequence in a naturally isolated cholesterol independent revertant cell population (NS0_r). This transcriptional repression was relieved after treating cells with the demethylating drug, 5-azacytidine. Drug treatment also gave rise to high frequency cholesterol-independent variants. Characterization of revertants revealed substantially elevated transcript level of 17beta-hydroxysteroid dehydrogenase type7 (Hsd17b7) gene along with hypomethylation of the CpG-rich region. These results affirm that deficiency of Hsd17b7 causes cholesterol dependence of NS0 cells. Furthermore, induction of cholesterol independence by altering DNA methylation pattern alludes to the role of epigenetics in the metabolic adaptation of NS0 cells. With the widespread use of NS0 cells, this finding will have a significant impact on the optimization of recombinant antibody production processes.
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Affiliation(s)
- Gargi Seth
- Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota, USA
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18
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Missiaglia E, Donadelli M, Palmieri M, Crnogorac-Jurcevic T, Scarpa A, Lemoine NR. Growth delay of human pancreatic cancer cells by methylase inhibitor 5-aza-2'-deoxycytidine treatment is associated with activation of the interferon signalling pathway. Oncogene 2005; 24:199-211. [PMID: 15637593 DOI: 10.1038/sj.onc.1208018] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Alteration of methylation status has been recognized as a possible epigenetic mechanism of selection during tumorigenesis in pancreatic cancer. This type of cancer is characterized by poor prognosis partly due to resistance to conventional drug treatments. We have used microarray technology to investigate the changes in global gene expression observed after treatment of different pancreatic cancer cell lines with the methylase inhibitor 5-aza-2'-deoxycytidine (5-aza-CdR). We have observed that this agent is able to inhibit to various degrees the growth of three pancreatic cancer cell lines. In particular, this inhibition was associated with induction of interferon (IFN)-related genes, as observed in other tumour types. Thus, expression of STAT1 seems to play a key role in the cellular response to treatment with the cytosine analogue. Moreover, we found increased p21(WAF1) and gadd45A expression to be associated with the efficacy of the treatment; this induction may correlate with activation of the IFN signalling pathway. Expression of the p16(INK) protein was also linked to the ability of cells to respond to 5-aza-CdR. Finally, genome-wide demethylation induced sensitization that significantly increased response to further treatment with various chemotherapy agents.
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Affiliation(s)
- Edoardo Missiaglia
- Cancer Research UK, Molecular Oncology Unit, Imperial College School of Medicine at Hammersmith Campus, London, UK
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19
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Kelly TLJ, Li E, Trasler JM. 5-aza-2'-deoxycytidine induces alterations in murine spermatogenesis and pregnancy outcome. ACTA ACUST UNITED AC 2004; 24:822-30. [PMID: 14581508 DOI: 10.1002/j.1939-4640.2003.tb03133.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Because of the ability of cytidine analogues, such as 5-aza-2'-deoxycytidine, to incorporate into DNA and lead to decreases in DNA methylation, there has recently been renewed interest in using these drugs in anticancer therapy. To determine the effects of paternal 5-aza-2'-deoxycytidine treatment on spermatogenesis and progeny outcome in the mouse and whether effects are modulated by decreased levels of the predominant DNA methyltransferase, DNMT1, adult Dnmt1(+/+) and Dnmt1-deficient (Dnmt1(c/+)) male mice were treated with 5-aza-2'-deoxycytidine for 7 weeks, which resulted in dose-dependent decreases in testicular weight, an increase in histological abnormalities, and a decline in sperm counts, with no apparent effect on androgen status. Testes of Dnmt1(c/+) mice, however, were less severely affected by 5-aza-2'-deoxycytidine than were those of wild-type mice. The exposure of Dnmt1(+/+) male mice to even low doses of 5-aza-2'-deoxycytidine followed by mating elicited significantly reduced pregnancy rates and elevated preimplantation loss in females. Dnmt1 deficiency, however, protected against such drug-induced decreases in pregnancy rate but not preimplantation loss. Altered DNA methylation or DNMT1 activity may explain such adverse effects, because treatment resulted in dose-dependent decreases in the global methylation of sperm DNA. Thus, in the mouse, paternal administration of 5-aza-2'-deoxycytidine interferes with normal male germ cell development and results in reduced fertility, whereas lowering DNMT1 levels appears to partially protect the seminiferous epithelium from deleterious drug effects.
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Affiliation(s)
- Tamara L J Kelly
- Departments of Pediatrics, McGill University, and McGill University-Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada
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20
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Christman JK. 5-Azacytidine and 5-aza-2'-deoxycytidine as inhibitors of DNA methylation: mechanistic studies and their implications for cancer therapy. Oncogene 2002; 21:5483-95. [PMID: 12154409 DOI: 10.1038/sj.onc.1205699] [Citation(s) in RCA: 1019] [Impact Index Per Article: 46.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
5-Azacytidine was first synthesized almost 40 years ago. It was demonstrated to have a wide range of anti-metabolic activities when tested against cultured cancer cells and to be an effective chemotherapeutic agent for acute myelogenous leukemia. However, because of 5-azacytidine's general toxicity, other nucleoside analogs were favored as therapeutics. The finding that 5-azacytidine was incorporated into DNA and that, when present in DNA, it inhibited DNA methylation, led to widespread use of 5-azacytidine and 5-aza-2'-deoxycytidine (Decitabine) to demonstrate the correlation between loss of methylation in specific gene regions and activation of the associated genes. There is now a revived interest in the use of Decitabine as a therapeutic agent for cancers in which epigenetic silencing of critical regulatory genes has occurred. Here, the current status of our understanding of the mechanism(s) by which 5-azacytosine residues in DNA inhibit DNA methylation is reviewed with an emphasis on the interactions of these residues with bacterial and mammalian DNA (cytosine-C5) methyltransferases. The implications of these mechanistic studies for development of less toxic inhibitors of DNA methylation are discussed.
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Affiliation(s)
- Judith K Christman
- Department of Biochemistry and Molecular Biology and UNMC/Eppley Cancer Center, University of Nebraska Medical Center, 984525 University Medical Center, Omaha, Nebraska, NE 68198-4525, USA.
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21
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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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22
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Kurek K, Matsumoto L, Gustafson G, Pires R, Tantravahi U, Suggs JW. Biological effects of a bifunctional DNA cross-linker. II. Generation of micronuclei and attached micronuclear-like structures. Mutat Res 1999; 426:89-94. [PMID: 10320754 DOI: 10.1016/s0027-5107(99)00041-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Madin-Darby bovine kidney (MDBK) cells were treated with the bifunctional DNA cross-linker, L-7, to examine the generation of micronuclei and other nuclear abnormalities. The preceding paper demonstrates that L-7 treatment induces the formation of triradial and quadriradial chromosomes in MDBK cells. These chromosomes are believed to result from interduplex DNA cross-links formed between G-C rich centromeric satellite DNA regions on non-sister chromatids. Treatment produces a majority of centromere-positive micronuclei. In addition, many daughter cells remain attached by chromatin bridges which are sometimes beaded with micronuclei. Up to 15% of cell nuclei become lobular and fused with numerous micronuclear-like structures attached to their membranes. These attached structures are classified as attached micronuclear-like structures (AMNLS). Fluorescence in situ hybridization (FISH) using a centromeric satellite sequence was performed on treated cells. Hybridization reveals that intercellular bridges are composed of centromeric sequences and initiate at centromeric foci in daughter cells. Furthermore, the majority of junctions between AMNLS and nuclei contain an enhancement of centromeric signal. The frequency of AMNLS appears dependent on the concentration of L-7 and the duration of treatment. Similar results were found for the generation of cross-linked chromosome products in the previous paper. We suggest that AMNLS result from the abnormal mitotic segregation of cross-linked chromosome products.
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Affiliation(s)
- K Kurek
- Division of Biology and Medicine, Brown University, Providence, RI 02912, USA
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23
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Ji W, Hernandez R, Zhang XY, Qu GZ, Frady A, Varela M, Ehrlich M. DNA demethylation and pericentromeric rearrangements of chromosome 1. Mutat Res 1997; 379:33-41. [PMID: 9330620 DOI: 10.1016/s0027-5107(97)00088-2] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Rearrangements in the vicinity of the centromere of chromosome 1 are over-represented in many types of human cancer and are a characteristic feature of a rare genetic disease called ICF (immunodeficiency, centromeric heterochromatin instability, and facial anomalies). Evidence is presented that implicates DNA hypomethylation in the formation of these pericentromeric chromosomal anomalies. The DNA methylation inhibitors 5-azadeoxycytidine and 5-azacytidine, but not other tested genotoxins, induced the preferential formation of pericentromeric rearrangements of chromosome 1 at a very high frequency in a pro-B-cell line (FLEB14) and at a lower frequency in a mature B-cell line (AHH-1). These abnormal chromosomes appear identical to the diagnostic chromosomal aberrations in the ICF syndrome. A major component of the pericentromeric DNA in chromosome 1, satellite 2, was shown to be hypomethylated in an ICF B-cell line, although DNA from this cell line did not display detectable overall hypomethylation. It is hypothesized that demethylation in certain DNA regions, including in pericentromeric satellite DNA, helps lead to pericentromeric chromosomal rearrangements in lymphocytes from ICF patients and in normal lymphoblastoid cells incubated in vitro with DNA demethylating agents.
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Affiliation(s)
- W Ji
- Department of Biochemistry, Tulane Medical School, New Orleans, LA 70112, USA
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24
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Hossain MM, Takashima A, Nakayama H, Doi K. 5-Azacytidine induces toxicity in PC12 cells by apoptosis. EXPERIMENTAL AND TOXICOLOGIC PATHOLOGY : OFFICIAL JOURNAL OF THE GESELLSCHAFT FUR TOXIKOLOGISCHE PATHOLOGIE 1997; 49:201-6. [PMID: 9314054 DOI: 10.1016/s0940-2993(97)80008-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
5-Azacytidine (5 Az)is a potent inhibitor of DNA methylation, and it may allow inactive genes to become expressed. In a previous study, we demonstrated that 5 Az administered to the dam induced apoptosis in the brains of fetal mice. In this study, the 5 Az-induced apoptosis was further characterized in differentiated PC 12 cells as a model for neuronal apoptosis. Cell death, determined by the activity of released lactate dehydrogenase (LDH) into the medium, occurred from 24 to 48 hrs after 5 Az treatment. Toxicity for differentiated PC 12 cells was observed on treatment with more than 10(-1) micrograms/ml of 5 Az, and it reached the maximal level at 10 micrograms/ml. Cycloheximide, an inhibitor of protein synthesis, prevented 5 Az toxicity, suggesting that this cell death required protein synthesis which could be related to the activation of a dormant gene(s). Electrophoresis of DNA from 5 Az-treated cells evoked ladder formation, indicating the cleavage of DNA into nucleosomes. Scanning electron microscopy demonstrated bleb formation, the so-called apoptotic bodies on the cell surface. The biochemical and morphological findings indicated that 5 Az-induced cell death occurred in the form of apoptosis. 5 Az-induced cell death was prevented by treatment with cAMP but not by treatment with high K+ or deoxycytidine. These results suggest that a cAMP-sensitive mechanism is involved in 5 Az-induced cell death. PC 12 cells should be of value in elucidating the molecular mechanism of 5 Az-induced neuronal apoptosis.
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Affiliation(s)
- M M Hossain
- Department of Veterinary Pathology, Faculty of Agriculture, University of Tokyo, Japan
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25
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Jüttermann R, Li E, Jaenisch R. Toxicity of 5-aza-2'-deoxycytidine to mammalian cells is mediated primarily by covalent trapping of DNA methyltransferase rather than DNA demethylation. Proc Natl Acad Sci U S A 1994; 91:11797-801. [PMID: 7527544 PMCID: PMC45322 DOI: 10.1073/pnas.91.25.11797] [Citation(s) in RCA: 496] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The deoxycytidine analog 5-aza-2'-deoxycytidine (5-azadCyd) has been widely used as a DNA methylation inhibitor to experimentally induce gene expression and cellular differentiation. Prior to the availability of mutant mice with altered DNA methyltransferase levels, treatment of cells with drugs has been the only means to experimentally manipulate the level of genomic DNA methylation in mammalian cells. Substitution of DNA with 5-azadCyd leads to covalent trapping of the enzyme, thereby depleting the cells of enzyme activity and resulting in DNA demethylation. 5-AzadCyd or 5-azacytidine treatment causes multiple changes in treated cells, including activation of silent genes, decondensation of chromatin, and induction of cellular differentiation, all of which are believed to be consequences of drug-induced demethylation. 5-AzadCyd is highly toxic in cultured cells and animals and is utilized as a potent antitumor agent for treatment of certain human cancers. It has been postulated that the toxicity of the drug in mammalian cells is also due to its inhibition of DNA methylation. The chemistry of the methylation reaction is consistent, however, with an alternative mechanism: the cytotoxic effect of 5-azadCyd may be directly mediated through the covalent binding of DNA methyltransferase to 5-azadCyd-substituted DNA. We have tested this possibility by using embryonic stem cells and mice with reduced levels of DNA methyltransferase due to a targeted mutation of the gene. When exposed to 5-azadCyd mutant embryonic stem cells or embryos were significantly more resistant to the toxic effects of the drug than wild-type cells and embryos, respectively. These results strongly suggest that the cellular DNA methyltransferase itself, rather than the secondary demethylation of genomic DNA, is the primary mediator of 5-azadCyd cytotoxicity. In light of our results, some conclusions from previous studies using 5-azadCyd in order to experimentally manipulate cellular methylation levels may have to be reassessed. Also, our data make clear predictions for cancer treatment: tumor cells with elevated DNA methyltransferase levels would be expected to be susceptible to treatment with 5-azadCyd, whereas tumors with reduced levels of the enzyme would be resistant.
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Affiliation(s)
- R Jüttermann
- Whitehead Institute for Biomedical Research, Cambridge, MA
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26
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De Cabo SF, Hazen MJ, Molero ML, Fernández-Piqueras J. S-adenosyl-L-homocysteine: a non-cytotoxic hypomethylating agent. EXPERIENTIA 1994; 50:658-9. [PMID: 7518395 DOI: 10.1007/bf01952867] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The cytotoxic effect caused by the hypomethylating agent S-adenosyl-L- homocysteine (SAH) was compared with that of two drugs commonly used to induce DNA hypomethylation, 5-azacytidine and 5-aza-2'-deoxycytidine. Two in vitro cytotoxicity tests, the tetrazolium MTT assay and the intracellular lactate dehydrogenase (LDH) activity test, suggest that SAH induces hypomethylation without causing any cytotoxic effect. We propose the use of SAH as a non-cytotoxic agent which may be more suitable for inducing experimental DNA hypomethylation.
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Affiliation(s)
- S F De Cabo
- Unidad de Genética, Facultad de Ciencias, Universidad Autónoma de Madrid, Spain
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27
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Caraglia M, Pinto A, Correale P, Zagonel V, Genua G, Leardi A, Pepe S, Bianco AR, Tagliaferri P. 5-Aza-2'-deoxycytidine induces growth inhibition and upregulation of epidermal growth factor receptor on human epithelial cancer cells. Ann Oncol 1994; 5:269-76. [PMID: 7514437 DOI: 10.1093/oxfordjournals.annonc.a058806] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
BACKGROUND The epidermal growth factor (EGF-R) receptor is an important growth regulator of epithelial cancer cells, and is presently considered a tumor-associated antigen (TAA) which is overexpressed by several human cancers and barely detectable in most normal tissues. Since TAA density at the tumor cell surface is a critical factor regulating the efficiency of immunotargeting procedures, a therapeutic advantage may derive from the pharmacologic enhancement of membrane expression of such antigens on tumor cells. MATERIALS AND METHODS Utilizing a panel of different human cancer cell lines of epithelial derivation, we have investigated in the in vitro effects of 5-aza-2'-deoxycytidine (5azaCdR), an antineoplastic agent able to induce gene activation and phenotypic modulation, on the surface expression of EGF-R by tumor cells. RESULTS 5azaCdR (10-1000 nM) induced growth inhibition, in the absence of acute cell kill, on KB (human oropharyngeal carcinoma), LoVo and the drug-resistant clone LoVo-DX (colon carcinoma) and A549 (lung adenocarcinoma) cell lines, along with a significant enhancement of EGF-R expression at the tumor cell surface. A single 24 h pulse of 5azaCdR, followed by 96 h of culture in drug-free medium, induced 50% growth inhibition on KB cells at a concentration (IC50) of 500 nM, on A549 (IC50 = 490 nM), LoVo (IC50 = 400 nM) and LoVo-DX (IC50 = 100 nM) cell lines. Under these conditions the specific binding of 125I-EGF was significantly upregulated at the surface of growth-inhibited cancer cells. Scatchard analysis of EGF-binding data revealed no changes in the Kd of EGF-R for its ligand in 5azaCdR-treated tumor cells and demonstrated a significant increase in the number of both the high- and low-affinity EGF-binding sites on KB cells, while only one class of EGF-binding site was detectable on A549, LoVo and LoVo-DX tumor cell lines before and after exposure to 5azaCdR. The EGF-R upregulation induced by 5azaCdR was paralleled by the increased binding of the anti-EGF-R monoclonal antibody (MAb) 108.1 on the surface of cancer cells. Finally, the rate of endocytosis of the anti-EGF-R MAb by KB cells was not modified by drug treatment, indicating that exposure to 5azaCdR does not hamper MAb internalization by the tumor cells. This latter represents an essential process for the cytotoxic effects of immunoconjugate drugs or toxins. CONCLUSIONS We suggest a role for 5azaCdR in enhancing the efficacy of therapeutic approaches involving the use of anti-EGF-R immunoconjugated for the imaging and the treatment of human epithelial neoplasias.
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Affiliation(s)
- M Caraglia
- Cattedra di Oncologia Medica, Facoltà di Medicina, Università Federico II, Naples, Italy
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28
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Stopper H, Körber C, Schiffmann D, Caspary WJ. Cell-cycle dependent micronucleus formation and mitotic disturbances induced by 5-azacytidine in mammalian cells. Mutat Res 1993; 300:165-77. [PMID: 7687016 DOI: 10.1016/0165-1218(93)90048-i] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
5-Azacytidine was originally developed to treat human myelogenous leukemia. However, interest in this compound has expanded because of reports of its ability to affect cell differentiation and to alter eukaryotic gene expression. In an ongoing attempt to understand the biochemical effects of this compound, we examined the effects of 5-azacytidine on mitosis and on micronucleus formation in mammalian cells. In L5178Y mouse cells, 5-azacytidine induced micronuclei at concentrations at which we and others have already reported its mutagenicity at the tk locus. Using CREST staining and C-banding studies, we showed that the induced micronuclei contained mostly chromosomal fragments although some may have contained whole chromosomes. By incorporating BrdU into the DNA of SHE cells, we determined that micronuclei were induced only when the compound was added while the cells were in S phase. Microscopically visible effects due to 5-azacytidine treatment were not observed until anaphase of the mitosis following treatment or thereafter. 5-Azacytidine did not induce micronuclei via interference with formation of the metaphase chromosome arrangement in mitosis, a common mechanism leading to aneuploidy. Supravital UV microscopy revealed that chromatid bridges were observed in anaphase and, in some cases, were sustained into interphase. In the first mitosis after 5-azacytidine treatment we observed that many cells were unable to perform anaphase separation. All of these observations indicate that 5-azacytidine is predominantly a clastogen through its incorporation into DNA.
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Affiliation(s)
- H Stopper
- Institute of Pharmacology and Toxicology, University of Würzburg, Germany
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