Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 14 de 14
Filtrar
Mais filtros











Base de dados
Intervalo de ano de publicação
1.
Free Radic Biol Med ; 170: 70-84, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33450377

RESUMO

The development of multicellular organisms involves the unpacking of a complex genetic program. Extensive characterization of discrete developmental steps has revealed the genetic program is controlled by an epigenetic state. Shifting the epigenome is a group of epigenetic enzymes that modify DNA and proteins to regulate cell type specific gene expression. While the role of these modifications in development has been established, the input(s) responsible for electing changes in the epigenetic state remains unknown. Development is also associated with dynamic changes in cellular metabolism, redox, free radical production, and oxygen availability. It has previously been postulated that these changes are causal in development by affecting gene expression. This suggests that oxygen is a morphogenic compound that impacts the removal of epigenetic marks. Likewise, metabolism and reactive oxygen species influence redox signaling through iron and glutathione to limit the availability of key epigenetic cofactors such as α-ketoglutarate, ascorbate, NAD+ and S-adenosylmethionine. Given the close relationship between these cofactors and epigenetic marks it seems likely that the two are linked. Here we describe how changing these inputs might affect the epigenetic state during development to drive gene expression. Combined, these cofactors and reactive oxygen species constitute the epigenetic landscape guiding cells along differing developmental paths.


Assuntos
Epigênese Genética , Histonas , Metilação de DNA , Histonas/metabolismo , Oxirredução , Oxigênio/metabolismo
2.
Hum Mol Genet ; 23(8): 2198-209, 2014 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-24256810

RESUMO

Genome-wide association studies of colorectal cancer (CRC) have identified a number of common variants associated with modest risk, including rs3802842 at chromosome 11q23.1. Several genes map to this region but rs3802842 does not map to any known transcribed or regulatory sequences. We reasoned, therefore, that rs3802842 is not the functional single-nucleotide polymorphism (SNP), but is in linkage disequilibrium (LD) with a functional SNP(s). We performed ChIP-seq for histone modifications in SW480 and HCT-116 CRC cells, and incorporated ChIP-seq and DNase I hypersensitivity data available through ENCODE within a 137-kb genomic region containing rs3802842 on 11q23.1. We identified SNP rs10891246 in LD with rs3802842 that mapped within a bidirectional promoter region of genes C11orf92 and C11orf93. Following mutagenesis to the risk allele, the promoter demonstrated lower levels of reporter gene expression. A second SNP rs7130173 was identified in LD with rs3802842 that mapped to a candidate enhancer region, which showed strong unidirectional activity in both HCT-116 and SW480 CRC cells. The risk allele of rs7130173 demonstrated reduced enhancer activity compared with the common allele, and reduced nuclear protein binding affinity in electromobility shift assays compared with the common allele suggesting differential transcription factor (TF) binding. SNPs rs10891246 and rs7130173 are on the same haplotype, and expression quantitative trait loci (eQTL) analyses of neighboring genes implicate C11orf53, C11orf92 and C11orf93 as candidate target genes. These data imply that rs10891246 and rs7130173 are functional SNPs mapping to 11q23.1 and that C11orf53, C11orf92 and C11orf93 represent novel candidate target genes involved in CRC etiology.


Assuntos
Mapeamento Cromossômico , Cromossomos Humanos Par 11/genética , Neoplasias Colorretais/genética , Elementos Facilitadores Genéticos/genética , Polimorfismo de Nucleotídeo Único/genética , Regiões Promotoras Genéticas/genética , Imunoprecipitação da Cromatina , Ensaio de Desvio de Mobilidade Eletroforética , Humanos , Luciferases/metabolismo , Repetições de Microssatélites/genética , Locos de Características Quantitativas , Fatores de Risco , Fatores de Transcrição/metabolismo , Células Tumorais Cultivadas
3.
Antioxid Redox Signal ; 18(15): 1946-55, 2013 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-22946823

RESUMO

SIGNIFICANCE: Manganese superoxide dismutase (SOD2), encoded by the nuclear gene SOD2, is a critical mitochondrial antioxidant enzyme whose activity has broad implications in health and disease. Thirty years ago, Oberley and Buettner elegantly folded SOD2 into cancer biology with the free radical theory of cancer, which was built on the observation that many human cancers had reduced SOD2 activity. In the original formulation, the loss of SOD2 in tumor cells produced a state of perpetual oxidative stress, which, in turn, drove genetic instability, leading to cancer development. RECENT ADVANCES: In the past two decades, research has established that SOD2 transcriptional activity is controlled, at least in part, via epigenetic mechanisms at different stages in the development of human cancer. These mechanisms, which include histone methylation, histone acetylation, and DNA methylation, are increasingly recognized as being aberrantly regulated in human cancer. Indeed, the epigenetic progenitor model proposed by Henikoff posits that epigenetic events are central governing agents of carcinogenesis. Important recent advances in epigenetics research have indicated that the loss of SOD activity itself may contribute to changes in epigenetic regulation, establishing a vicious cycle that drives further epigenetic instability. CRITICAL ISSUES: With these observations in mind, we propose an epigenetic revision to the free radical theory of cancer: that loss of SOD activity promotes epigenetic aberrancies, driving the epigenetic instability in tumor cells which produces broad phenotypic effects. FUTURE DIRECTIONS: The development of next-generation sequencing technologies and novel approaches in systems biology and bioinformatics promise to make testing this exciting model a reality in the near future.


Assuntos
Ilhas de CpG , Metilação de DNA , Histonas/metabolismo , Neoplasias/genética , Neoplasias/metabolismo , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismo , Epigênese Genética , Regulação Neoplásica da Expressão Gênica , Humanos , Oxirredução , Espécies Reativas de Oxigênio/metabolismo , Superóxidos/metabolismo
4.
Free Radic Biol Med ; 53(11): 2178-87, 2012 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-23022407

RESUMO

Cancer arises from normal cells that acquire a series of molecular changes; however, the founding events that create the clonogens from which a tumor will arise and progress have been the subject of speculation. Through the efforts of several generations of cancer biologists it has been established that the malignant phenotype is an amalgamation of genetic and metabolic alterations. Numerous theories have suggested that either, or both, of these elements might serve as the impetus for cancer formation. Recently, the epigenetic origins of cancer have been suggested as an additional mechanism giving rise to the malignant phenotype. When the discovery that the enzymes responsible for initiating and perpetuating epigenetic events is linked to metabolism by their cofactors, a new paradigm for the origins of cancer can be created. Here, we summarize the foundation of such a paradigm on the origins of cancer, in which metabolic alterations create an epigenetic progenitor that clonally expands to become cancer. We suggest that metabolic alterations disrupt the production and availability of cofactors such as S-adenosylmethionine, α-ketoglutarate, NAD(+), and acetyl-CoA to modify the epigenotype of cells. We further speculate that redox biology can change epigenetic events through oxidation of enzymes and alterations in metabolic cofactors that affect epigenetic events such as DNA methylation. Combined, these metabolic and redox changes serve as the foundation for altering the epigenotype of normal cells and creating the epigenetic progenitor of cancer.


Assuntos
Epigênese Genética , Neoplasias/metabolismo , Acetilação , Animais , Metabolismo dos Carboidratos , Epigenômica , Genoma Humano , Histonas/metabolismo , Humanos , Metilação , Neoplasias/genética , Oxirredução , Processamento de Proteína Pós-Traducional
5.
Clin Cancer Res ; 15(11): 3672-9, 2009 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-19458056

RESUMO

PURPOSE: Transcriptional regulation of estrogen receptor-alpha (ERalpha) involves both epigenetic mechanisms and trans-active factors, such as TFAP2C, which induces ERalpha transcription through an AP-2 regulatory region in the ERalpha promoter. Attempts to induce endogenous ERalpha expression in ERalpha-negative breast carcinomas by forced overexpression of TFAP2C have not been successful. We hypothesize that epigenetic chromatin structure alters the activity of TFAP2C at the ERalpha promoter. EXPERIMENTAL DESIGN: DNA methylation, histone acetylation, and chromatin accessibility were examined at the ERalpha promoter in a panel of breast carcinoma cell lines. TFAP2C and polymerase II binding were analyzed by chromatin immunoprecipitation. Epigenetic chromatin structure was altered using drug treatment with 5-aza-2'-deoxycytidine (AZA) and trichostatin A (TSA). RESULTS: The ERalpha promoter in the ERalpha-negative lines MDA-MB-231, MCF10A, and MCF7-5C show CpG island methylation, histone 3 lysine 9 deacetylation, and decreased chromatin accessibility compared with ERalpha-positive cell lines MCF7 and T47-D. Treatment with AZA/TSA increased chromatin accessibility at the ERalpha promoter and allowed TFAP2C to induce ERalpha expression in ERalpha-negative cells. Chromatin immunoprecipitation analysis showed that binding of TFAP2C to the ERalpha promoter is blocked in ERalpha-negative cells but that treatment with AZA/TSA enabled TFAP2C and polymerase II binding. CONCLUSION: We conclude that the activity of TFAP2C at specific target genes depends upon epigenetic chromatin structure. Furthermore, the combination of increasing chromatin accessibility and inducing TFAP2C provides a more robust activation of the ERalpha gene in ERalpha-negative breast cancer cells.


Assuntos
Cromatina/metabolismo , Receptor alfa de Estrogênio/genética , Regiões Promotoras Genéticas/genética , Fator de Transcrição AP-2/metabolismo , Acetilação/efeitos dos fármacos , Azacitidina/análogos & derivados , Azacitidina/farmacologia , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Neoplasias da Mama/patologia , Linhagem Celular Tumoral , Cromatina/efeitos dos fármacos , Imunoprecipitação da Cromatina , Ilhas de CpG/genética , Metilação de DNA/efeitos dos fármacos , Decitabina , Inibidores Enzimáticos/farmacologia , Feminino , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Histonas/metabolismo , Humanos , Ácidos Hidroxâmicos/farmacologia , Lisina/metabolismo , Ligação Proteica , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fator de Transcrição AP-2/genética
6.
Free Radic Biol Med ; 47(2): 115-27, 2009 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-19362589

RESUMO

Cancer is a pathology that is associated with aberrant gene expression and an altered metabolism. Whereas changes in gene expression have historically been attributed to mutations, it has become apparent that epigenetic processes also play a critical role in controlling gene expression during carcinogenesis. Global changes in epigenetic processes, including DNA methylation and histone modifications, have been observed in cancer. These epigenetic alterations can aberrantly silence or activate gene expression during the formation of cancer; however, the process leading to this epigenetic switch in cancer remains unknown. Carcinogenesis is also associated with metabolic defects that increase mitochondrially derived reactive oxygen species, create an atypical redox state, and change the fundamental means by which cells produce energy. Here, we summarize the influence of these metabolic defects on epigenetic processes. Metabolic defects affect epigenetic enzymes by limiting the availability of cofactors like S-adenosylmethionine. Increased production of reactive oxygen species alters DNA methylation and histone modifications in tumor cells by oxidizing DNMTs and HMTs or through direct oxidation of nucleotide bases. Last, the Warburg effect and increased glutamine consumption in cancer influence histone acetylation and methylation by affecting the activity of sirtuins and histone demethylases.


Assuntos
Epigênese Genética , Neoplasias/metabolismo , Acetilação , Animais , Metilação de DNA/fisiologia , Radicais Livres/metabolismo , Glutationa/biossíntese , Histonas/metabolismo , Humanos , Neoplasias/genética , Nucleossomos/metabolismo , Oxirredução , S-Adenosilmetionina/biossíntese , S-Adenosilmetionina/genética
7.
J Oncol ; 2009: 780874, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-20066163

RESUMO

AP-2alpha and c-MYC are important transcription factors involved in multiple cellular processes. They each display the paradoxical capacities to stimulate both cell proliferation and apoptosis under different conditions. In the present study we found that over expression of c-MYC was associated with accumulation of reactive oxygen species (ROS) and apoptosis in human keratinocytes, both of which were significantly inhibited by co-expression of AP-2. The effects of AP-2 on c-MYC were active at several levels. First, AP-2 and c-MYC were confirmed to interact at the protein level as previously described. In addition, forced expression of AP-2 significantly decreased steady state levels of c-MYC mRNA and protein. These findings suggested that AP-2 may have a direct effect on the c-myc gene. Chromatin immunoprecipitation assays demonstrated that AP-2 proteins bound to a cluster of AP-2 binding sites located within a 2 kb upstream regulatory region of c-myc These results suggest that the negative regulation of AP-2 on c-MYC activity was achieved through binding of AP-2 protein to the c-myc gene. The effects of AP-2 on c-MYC induced ROS accumulation and apoptosis in epidermal keratinocytes are likely to play an important role in cell growth, differentiation and carcinogenesis of the skin.

8.
Free Radic Biol Med ; 45(11): 1573-80, 2008 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-18845242

RESUMO

Many breast cancer cells typically exhibit lower expression of manganese superoxide dismutase (MnSOD) compared to the normal cells from which they arise. This decrease can often be attributed to a defect in the transcription of SOD2, the gene encoding MnSOD; however, the mechanism responsible for this change remains unclear. Here, we describe how altered histone modifications and a repressive chromatin structure constitute an epigenetic process to down regulate SOD2 in human breast carcinoma cell lines. Utilizing chromatin immunoprecipitation (ChIP) we observed decreased levels of dimethyl H3K4 and acetylated H3K9 at key regulatory elements of the SOD2 gene. Consistent with these results, we show that loss of these histone modifications creates a repressive chromatin structure at SOD2. Transcription factor ChIP experiments revealed that this repressive chromatin structure influences the binding of SP-1, AP-1, and NFkappaB to SOD2 regulatory cis-elements in vivo. Lastly, we show that treatment with the histone deacetylase inhibitors trichostatin A and sodium butyrate can reactivate SOD2 expression in breast cancer cell lines. Taken together, these results indicate that epigenetic silencing of SOD2 could be facilitated by changes in histone modifications and represent one mechanism leading to the altered expression of MnSOD observed in many breast cancers.


Assuntos
Neoplasias da Mama/genética , Inativação Gênica , Histonas/metabolismo , Superóxido Dismutase/genética , Acetilação , Neoplasias da Mama/enzimologia , Neoplasias da Mama/metabolismo , Linhagem Celular Tumoral , Cromatina/metabolismo , Cromatina/ultraestrutura , Imunoprecipitação da Cromatina , Feminino , Código das Histonas , Inibidores de Histona Desacetilases , Histona Desacetilases/metabolismo , Humanos , Ácidos Hidroxâmicos/farmacologia , Metilação , NF-kappa B/metabolismo , Regiões Promotoras Genéticas , RNA Mensageiro/metabolismo , Fator de Transcrição Sp1/metabolismo , Superóxido Dismutase/metabolismo , Fator de Transcrição AP-1/metabolismo , Ativação Transcricional
9.
Free Radic Biol Med ; 43(7): 1023-36, 2007 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-17761298

RESUMO

The development of organisms requires concerted changes in gene activity. The free radical theory of development proposes that oxygen serves as a morphogen to educe development by influencing the production of metabolic oxidants such as free radicals and reactive oxygen species. One of the central tenets of this theory is that these metabolic oxidants influence development by altering the antioxidant capacity of cells by changing their production of glutathione (GSH). Here we extend on these principles by linking GSH production and oxygen sensing in the control of gene expression to establish the epigenotype of cells during development. We prescribe this novel role to GSH and oxygen during development because these metabolites influence the activity of enzymes responsible for initiating and perpetuating epigenetic control of gene expression. Increased GSH production influences epigenetic processes including DNA and histone methylation by limiting the availability of S-adenosylmethionine, the cofactor utilized during epigenetic control of gene expression by DNA and histone methyltransferases. Moreover, the recent discovery of histone demethylases that require oxygen as a cofactor directly links epigenetic processes to oxygen gradients during development.


Assuntos
Metilação de DNA , Epigênese Genética , Radicais Livres , Estresse Oxidativo , Animais , Dano ao DNA/genética , Humanos , Neoplasias/induzido quimicamente , Neoplasias/genética , Neoplasias/metabolismo , Oxirredução
10.
Exp Mol Pathol ; 83(2): 277-82, 2007 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-17651731

RESUMO

Amyloid precursor protein (APP) has been implicated in squamous cell carcinoma. In this study we show that forced expression of the transcription factor activating protein 2alpha (AP-2alpha) results in significantly increased steady state levels of APP mRNA in human keratinocytes. Sequence analysis of the 5' end of the human APP gene revealed five putative binding sites for AP-2, suggesting that APP is a direct target for transactivation by AP-2. AP-2 protein bound at least 3 of these putative promoter elements in vitro as determined by electrophoretic mobility shift assay. Chromatin immunoprecipitation (ChIP) analysis showed that these binding sites were occupied by AP-2 in cells, thus indicating the relevance to AP-2 binding in vivo. We then analyzed APP and AP-2 mRNA and protein expression in squamous cell carcinoma tumor samples. Analysis of RNA extracted from human tissue showed a significant positive correlation between AP-2alpha and APP mRNA expression. Immunohistochemical staining of tumor samples also demonstrated a positive correlation which was substantiated through western blot studies. Taken together, these findings demonstrate a role for the transcription factor AP-2alpha in the regulation of APP gene expression in human keratinocytes.


Assuntos
Precursor de Proteína beta-Amiloide/genética , Carcinoma de Células Escamosas/genética , Regulação Neoplásica da Expressão Gênica , Neoplasias Bucais/genética , Receptores de Superfície Celular/genética , Fator de Transcrição AP-2/genética , Fator de Transcrição AP-2/fisiologia , Transcrição Gênica , Carcinoma de Células Escamosas/patologia , Linhagem Celular , Cromatina/genética , Primers do DNA , Humanos , Queratinócitos/fisiologia , Neoplasias Bucais/patologia , Nexinas de Proteases , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transfecção
11.
Cancer Res ; 67(13): 6392-9, 2007 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-17616699

RESUMO

Thiol antioxidants, including N-acetyl-L-cysteine (NAC), are widely used as modulators of the intracellular redox state. We investigated the hypothesis that NAC-induced reactive oxygen species (ROS) signaling perturbs cellular proliferation by regulating the cell cycle regulatory protein cyclin D1 and the ROS scavenging enzyme Mn-superoxide dismutase (MnSOD). When cultured in media containing NAC, mouse fibroblasts showed G(1) arrest with decreased cyclin D1 protein levels. The absence of a NAC-induced G(1) arrest in fibroblasts overexpressing cyclin D1 (or a nondegradable mutant of cyclin D1-T286A) indicates that cyclin D1 regulates this G(1) arrest. A delayed response to NAC exposure was an increase in both MnSOD protein and activity. NAC-induced G(1) arrest is exacerbated in MnSOD heterozygous fibroblasts. Results from electron spin resonance spectroscopy and flow cytometry measurements of dihydroethidine fluorescence showed an approximately 2-fold to 3-fold increase in the steady-state levels of superoxide (O(2)(*-)) in NAC-treated cells compared with control. Scavenging of O(2)(*-) with Tiron reversed the NAC-induced G(1) arrest. These results show that an O(2)(*-) signaling pathway regulates NAC-induced G(1) arrest by decreasing cyclin D1 protein levels and increasing MnSOD activity.


Assuntos
Acetilcisteína/farmacologia , Ciclina D1/metabolismo , Superóxido Dismutase/metabolismo , Superóxidos/metabolismo , Animais , Dicarbetoxi-Di-Hidrocolidina/análogos & derivados , Dicarbetoxi-Di-Hidrocolidina/farmacologia , Espectroscopia de Ressonância de Spin Eletrônica , Fibroblastos/metabolismo , Fase G1 , Humanos , Camundongos , Células NIH 3T3 , Oxirredução , Espécies Reativas de Oxigênio , Transdução de Sinais
12.
Cancer Res ; 66(3): 1605-10, 2006 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-16452219

RESUMO

It has been hypothesized that cancer cells increase glucose metabolism to protect against metabolic fluxes of hydroperoxides via glutathione-dependent peroxidases. 2-Deoxy-D-glucose, inhibits glucose metabolism and has been shown to cause cytotoxicity in cancer cells that is partially mediated by disruptions in thiol metabolism. In the current study, human breast cancer cells were continuously treated (24 hours) with 2-deoxy-D-glucose, and total glutathione content as well as the expression of the first enzyme in the glutathione synthetic pathway [glutamate cysteine ligase (GCL)] were found to be induced 2.0-fold. Inhibiting GCL activity during 2-deoxy-D-glucose exposure using l-buthionine-[S,R]-sulfoximine (BSO) significantly enhanced the cytotoxic effects of 2-deoxy-D-glucose and caused increases in endpoints indicative of oxidative stress, including % oxidized glutathione and steady-state levels of pro-oxidants as assayed using an oxidation-sensitive fluorescent probe. These results show that treatment of human breast cancer cells with 2-deoxy-d-glucose causes metabolic oxidative stress that is accompanied by increases in steady-state levels of GCL mRNA, GCL activity, and glutathione content. Furthermore, inhibition of 2-deoxy-D-glucose-mediated induction of GCL activity with BSO increases endpoints indicative of oxidative stress and sensitizes cancer cells to 2-deoxy-D-glucose-induced cytotoxicity. These results support the hypothesis that drug combinations capable of inhibiting both glucose and hydroperoxide metabolism may provide an effective biochemical strategy for sensitizing human cancer cells to metabolic oxidative stress.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Neoplasias da Mama/tratamento farmacológico , Neoplasias da Mama/enzimologia , Butionina Sulfoximina/farmacologia , Desoxiglucose/farmacologia , Glutamato-Cisteína Ligase/antagonistas & inibidores , Antimetabólitos Antineoplásicos/farmacologia , Neoplasias da Mama/sangue , Linhagem Celular Tumoral , Desoxiglucose/sangue , Sinergismo Farmacológico , Inibidores Enzimáticos/farmacologia , Glutamato-Cisteína Ligase/genética , Glutamato-Cisteína Ligase/metabolismo , Glutationa/metabolismo , Dissulfeto de Glutationa/metabolismo , Humanos , Estresse Oxidativo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo
13.
Gynecol Oncol ; 102(2): 319-24, 2006 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16457875

RESUMO

OBJECTIVE: Maspin expression is often deregulated in human cancer cells compared to their normal cells due to loss of epigenetic control. In contrast to normal human ovarian surface epithelial (HOSE) cells, ovarian carcinoma cells display a gain of maspin mRNA expression. The objective of this study was to determine whether gain of maspin expression in ovarian cancer is governed by epigenetic mechanisms. METHODS: We examined the cytosine methylation and chromatin accessibility status of the maspin promoter in normal HOSE cells and ovarian carcinoma cells with real-time RT-PCR, sodium bisulfite genomic sequencing, and chromatin accessibility assays. 5-Aza-2'-deoxycytidine (5-aza-dC) was used to induce demethylation of the maspin promoter. Ad p53 was used to induce transient overexpression of wild-type p53. RESULTS: Normal HOSE cells were maspin-negative in association with methylation of the maspin promoter. In the maspin-positive ovarian cancer cell lines, the maspin promoter was unmethylated. Increased maspin expression in ovarian carcinoma cells was accompanied by a more accessible chromatin structure in the maspin promoter. In the maspin-negative ovarian cancer cell line A222, maspin could be induced following 5-aza-dC treatment or by forced overexpression of p53. CONCLUSIONS: These results suggest that changes in cytosine methylation and chromatin accessibility play an important role in maspin expression in human ovarian carcinoma. Deregulation of maspin expression in ovarian cancer is due to loss of epigenetic control as has been shown in other cancers. This observation provides further evidence of the strict epigenetic control of the maspin gene.


Assuntos
Neoplasias Ovarianas/genética , Serpinas/genética , Cromatina/genética , Metilação de DNA , Feminino , Regulação Neoplásica da Expressão Gênica , Genes Supressores de Tumor , Humanos , Neoplasias Ovarianas/metabolismo , Regiões Promotoras Genéticas , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Serpinas/biossíntese
14.
Epigenetics ; 1(4): 163-71, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-17965603

RESUMO

Malignant breast cancer cells often exhibit lower expression and activity of manganese superoxide dismutase (MnSOD) than their normal cell counterparts; however, the mechanism(s) responsible for this change remains unclear. We examined whether SOD2, the gene encoding MnSOD, was epigenetically repressed in breast cancer cell lines by DNA methylation and histone acetylation. RT-PCR analysis of SOD2 mRNA showed the nontumorigenic breast epithelial cell line MCF-10A to have two to three fold higher expression levels than either UACC-893 or MDA-MB-435 breast carcinoma cells. Analysis of a region in the SOD2 promoter by sodium bisulfite genomic sequencing demonstrated significantly higher levels of CpG methylation in both human breast carcinoma cell lines assessed than in MCF-10A cells. CREB binding in vitro to a cognate site derived from this region was repressed by DNA methylation, and CREB binding to the 5' regulatory region of the SOD2 gene in vivo as determined by ChIP was significantly lower in breast carcinoma cells than in MCF-10A. Increased cytosine methylation was also accompanied by a significant decrease in the level of acetylated histones in the same region of the SOD2 promoter. Finally, a causal link between cytosine methylation and transcriptional repression was established by increasing MnSOD mRNA, protein and activity in breast carcinoma cells using the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine. These findings indicate that epigenetic silencing of SOD2 constitutes one mechanism leading to the decreased expression of MnSOD observed in many breast cancers.


Assuntos
Neoplasias da Mama/enzimologia , Neoplasias da Mama/genética , Epigênese Genética/genética , Regulação Enzimológica da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Inativação Gênica , Superóxido Dismutase/genética , Linhagem Celular Tumoral , Primers do DNA , Feminino , Gliceraldeído-3-Fosfato Desidrogenases/genética , Humanos , Análise de Sequência com Séries de Oligonucleotídeos , Reação em Cadeia da Polimerase
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA