RESUMEN
Treatments targeting metabolic abnormalities in children with autism are limited. Previously we reported that a nutritional treatment significantly improved glutathione metabolism in children with autistic disorder. In this study we evaluated changes in adaptive behaviors in this cohort and determined whether such changes are related to changes in glutathione metabolism. Thirty-seven children diagnosed with autistic disorder and abnormal glutathione and methylation metabolism were treated with twice weekly 75 µg/Kg methylcobalamin and twice daily 400 µg folinic acid for 3 months in an open-label fashion. The Vineland Adaptive Behavior Scale (VABS) and glutathione redox metabolites were measured at baseline and at the end of the treatment period. Over the treatment period, all VABS subscales significantly improved with an average effect size of 0.59, and an average improvement in skills of 7.7 months. A greater improvement in glutathione redox status was associated with a greater improvement in expressive communication, personal and domestic daily living skills, and interpersonal, play-leisure, and coping social skills. Age, gender, and history of regression did not influence treatment response. The significant behavioral improvements observed and the relationship between these improvements to glutathione redox status suggest that nutritional interventions targeting redox metabolism may benefit some children with autism.
RESUMEN
The biologic basis of autism is complex and is thought to involve multiple and variable gene-environment interactions. While the logical focus has been on the affected child, the impact of maternal genetics on intrauterine microenvironment during pivotal developmental windows could be substantial. Folate-dependent one carbon metabolism is a highly polymorphic pathway that regulates the distribution of one-carbon derivatives between DNA synthesis (proliferation) and DNA methylation (cell-specific gene expression and differentiation). These pathways are essential to support the programmed shifts between proliferation and differentiation during embryogenesis and organogenesis. Maternal genetic variants that compromise intrauterine availability of folate derivatives could alter fetal cell trajectories and disrupt normal neurodevelopment. In this investigation, the frequency of common functional polymorphisms in the folate pathway was investigated in a large population-based sample of autism case-parent triads. In case-control analysis, a significant increase in the reduced folate carrier (RFC1) G allele frequency was found among case mothers, but not among fathers or affected children. Subsequent log linear analysis of the RFC1 A80G genotype within family trios revealed that the maternal G allele was associated with a significant increase in risk of autism whereas the inherited genotype of the child was not. Further, maternal DNA from the autism mothers was found to be significantly hypomethylated relative to reference control DNA. Metabolic profiling indicated that plasma homocysteine, adenosine, and S-adenosylhomocyteine were significantly elevated among autism mothers consistent with reduced methylation capacity and DNA hypomethylation. Together, these results suggest that the maternal genetics/epigenetics may influence fetal predisposition to autism.
Asunto(s)
Trastorno Autístico/genética , Metilación de ADN/genética , Madres , Polimorfismo Genético/genética , Proteína Portadora de Folato Reducido/genética , Adulto , Alelos , Estudios de Casos y Controles , Niño , Preescolar , Epigenómica , Femenino , Ácido Fólico/metabolismo , Frecuencia de los Genes , Humanos , Masculino , Adulto JovenRESUMEN
Research into the metabolic phenotype of autism has been relatively unexplored despite the fact that metabolic abnormalities have been implicated in the pathophysiology of several other neurobehavioral disorders. Plasma biomarkers of oxidative stress have been reported in autistic children; however, intracellular redox status has not yet been evaluated. Lymphoblastoid cells (LCLs) derived from autistic children and unaffected controls were used to assess relative concentrations of reduced glutathione (GSH) and oxidized disulfide glutathione (GSSG) in cell extracts and isolated mitochondria as a measure of intracellular redox capacity. The results indicated that the GSH/GSSG redox ratio was decreased and percentage oxidized glutathione increased in both cytosol and mitochondria in the autism LCLs. Exposure to oxidative stress via the sulfhydryl reagent thimerosal resulted in a greater decrease in the GSH/GSSG ratio and increase in free radical generation in autism compared to control cells. Acute exposure to physiological levels of nitric oxide decreased mitochondrial membrane potential to a greater extent in the autism LCLs, although GSH/GSSG and ATP concentrations were similarly decreased in both cell lines. These results suggest that the autism LCLs exhibit a reduced glutathione reserve capacity in both cytosol and mitochondria that may compromise antioxidant defense and detoxification capacity under prooxidant conditions.
Asunto(s)
Trastorno Autístico/metabolismo , Glutatión/metabolismo , Linfocitos/metabolismo , Adenosina Trifosfato/metabolismo , Adolescente , Adulto , Trastorno Autístico/etiología , Estudios de Casos y Controles , Línea Celular , Niño , Citosol/metabolismo , Radicales Libres/metabolismo , Disulfuro de Glutatión/metabolismo , Humanos , Linfocitos/efectos de los fármacos , Masculino , Potencial de la Membrana Mitocondrial , Mitocondrias/metabolismo , Estrés Oxidativo/efectos de los fármacos , S-Nitroso-N-Acetilpenicilamina/farmacología , Timerosal/farmacología , Adulto JovenRESUMEN
BACKGROUND: Metabolic abnormalities and targeted treatment trials have been reported for several neurobehavioral disorders but are relatively understudied in autism. OBJECTIVE: The objective of this study was to determine whether or not treatment with the metabolic precursors, methylcobalamin and folinic acid, would improve plasma concentrations of transmethylation/transsulfuration metabolites and glutathione redox status in autistic children. DESIGN: In an open-label trial, 40 autistic children were treated with 75 microg/kg methylcobalamin (2 times/wk) and 400 microg folinic acid (2 times/d) for 3 mo. Metabolites in the transmethylation/transsulfuration pathway were measured before and after treatment and compared with values measured in age-matched control children. RESULTS: The results indicated that pretreatment metabolite concentrations in autistic children were significantly different from values in the control children. The 3-mo intervention resulted in significant increases in cysteine, cysteinylglycine, and glutathione concentrations (P < 0.001). The oxidized disulfide form of glutathione was decreased and the glutathione redox ratio increased after treatment (P < 0.008). Although mean metabolite concentrations were improved significantly after intervention, they remained below those in unaffected control children. CONCLUSION: The significant improvements observed in transmethylation metabolites and glutathione redox status after treatment suggest that targeted nutritional intervention with methylcobalamin and folinic acid may be of clinical benefit in some children who have autism. This trial was registered at (clinicaltrials.gov) as NCT00692315.
Asunto(s)
Trastorno Autístico/metabolismo , Glutatión/metabolismo , Leucovorina/farmacología , Estado Nutricional , Vitamina B 12/análogos & derivados , Complejo Vitamínico B/farmacología , Trastorno Autístico/sangre , Niño , Preescolar , Cromatografía Líquida de Alta Presión , Suplementos Dietéticos , Femenino , Glutatión/sangre , Humanos , Leucovorina/sangre , Masculino , Metilación , Oxidación-Reducción , Estrés Oxidativo/efectos de los fármacos , S-Adenosilhomocisteína/sangre , S-Adenosilhomocisteína/metabolismo , S-Adenosilmetionina/sangre , S-Adenosilmetionina/metabolismo , Resultado del Tratamiento , Vitamina B 12/sangre , Vitamina B 12/farmacología , Complejo Vitamínico B/sangreAsunto(s)
Trastorno Autístico/diagnóstico , Metilación de ADN , Glutatión/metabolismo , Homocisteína/metabolismo , Padres , Adolescente , Adulto , Trastorno Autístico/genética , Estudios de Casos y Controles , Niño , Cromatografía Líquida de Alta Presión , Metilación de ADN/genética , Femenino , Humanos , Masculino , Metionina/metabolismo , Persona de Mediana Edad , Estrés Oxidativo/genética , Polimorfismo GenéticoRESUMEN
The non adult immune system is particularly sensitive to perinatal and early life exposures to environmental toxicants. The common environmental toxicant, trichloroethylene (TCE), was shown to increase CD4+ T cell production of the proinflammatory cytokine IFN-gamma following a period of prenatal and lifetime exposure in autoimmune-prone MRL+/+ mice. In the current study, MRL+/+ mice were used to further examine the impact of TCE on the immune system in the thymus and periphery. Since there is considerable cross-talk between the immune system and the brain during development, the potential relationship between TCE and neurobehavioral endpoints were also examined. MRL+/+ mice were exposed to 0.1 mg/ml TCE (~ 31 mg/kg/day) via maternal drinking water or direct exposure via the drinking water from gestation day 1 until postnatal day (PD) 42. TCE exposure did not impact gross motor skills but instead significantly altered social behaviors and promoted aggression associated with indicators of oxidative stress in brain tissues in male mice. The immunoregulatory effects of TCE involved a redox-associated promotion of T cell differentiation in the thymus that preceded the production of proinflammatory cytokines, IL-2, TNF-alpha, and IFN-gamma by mature CD4+ T cells. The results demonstrated that developmental and early life TCE exposure modulated immune function and may have important implications for neurodevelopmental disorders.
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Linfocitos T CD4-Positivos/citología , Diferenciación Celular/fisiología , Hipercinesia/patología , Enfermedades del Sistema Nervioso/patología , Estrés Oxidativo/fisiología , Tricloroetileno/toxicidad , Animales , Animales Recién Nacidos , Linfocitos T CD4-Positivos/efectos de los fármacos , Linfocitos T CD4-Positivos/metabolismo , Diferenciación Celular/efectos de los fármacos , Femenino , Hipercinesia/inducido químicamente , Hipercinesia/metabolismo , Masculino , Ratones , Ratones Endogámicos MRL lpr , Enfermedades del Sistema Nervioso/inducido químicamente , Enfermedades del Sistema Nervioso/metabolismo , Estrés Oxidativo/efectos de los fármacos , Conducta SocialRESUMEN
An integrated metabolic profile reflects the combined influence of genetic, epigenetic, and environmental factors that affect the candidate pathway of interest. Recent evidence suggests that some autistic children may have reduced detoxification capacity and may be under chronic oxidative stress. Based on reports of abnormal methionine and glutathione metabolism in autistic children, it was of interest to examine the same metabolic profile in the parents. The results indicated that parents share similar metabolic deficits in methylation capacity and glutathione-dependent antioxidant/detoxification capacity observed in many autistic children. Studies are underway to determine whether the abnormal profile in parents reflects linked genetic polymorphisms in these pathways or whether it simply reflects the chronic stress of coping with an autistic child.
Asunto(s)
Trastorno Autístico/epidemiología , ADN/metabolismo , Metilación , Padres , Niño , HumanosRESUMEN
Autism is a behaviorally defined neurodevelopmental disorder usually diagnosed in early childhood that is characterized by impairment in reciprocal communication and speech, repetitive behaviors, and social withdrawal. Although both genetic and environmental factors are thought to be involved, none have been reproducibly identified. The metabolic phenotype of an individual reflects the influence of endogenous and exogenous factors on genotype. As such, it provides a window through which the interactive impact of genes and environment may be viewed and relevant susceptibility factors identified. Although abnormal methionine metabolism has been associated with other neurologic disorders, these pathways and related polymorphisms have not been evaluated in autistic children. Plasma levels of metabolites in methionine transmethylation and transsulfuration pathways were measured in 80 autistic and 73 control children. In addition, common polymorphic variants known to modulate these metabolic pathways were evaluated in 360 autistic children and 205 controls. The metabolic results indicated that plasma methionine and the ratio of S-adenosylmethionine (SAM) to S-adenosylhomocysteine (SAH), an indicator of methylation capacity, were significantly decreased in the autistic children relative to age-matched controls. In addition, plasma levels of cysteine, glutathione, and the ratio of reduced to oxidized glutathione, an indication of antioxidant capacity and redox homeostasis, were significantly decreased. Differences in allele frequency and/or significant gene-gene interactions were found for relevant genes encoding the reduced folate carrier (RFC 80G > A), transcobalamin II (TCN2 776G > C), catechol-O-methyltransferase (COMT 472G > A), methylenetetrahydrofolate reductase (MTHFR 677C > T and 1298A > C), and glutathione-S-transferase (GST M1). We propose that an increased vulnerability to oxidative stress (endogenous or environmental) may contribute to the development and clinical manifestations of autism.
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Trastorno Autístico/genética , Trastorno Autístico/metabolismo , Metionina/sangre , Estrés Oxidativo/genética , Adolescente , Trastorno Autístico/sangre , Catecol O-Metiltransferasa/genética , Niño , Preescolar , Cartilla de ADN , Femenino , Frecuencia de los Genes , Glutatión Transferasa/genética , Humanos , Masculino , Proteínas de Transporte de Membrana/genética , Metionina/metabolismo , Metilación , Metilenotetrahidrofolato Reductasa (NADPH2)/genética , Proteína Portadora de Folato Reducido , S-Adenosilhomocisteína/sangre , S-Adenosilmetionina/sangre , Transcobalaminas/genéticaRESUMEN
OBJECTIVE: This study was undertaken to investigate the association between congenital heart defects (CHD), and maternal homocysteine, smoking, and the MTHFR 677 C>T polymorphism. STUDY DESIGN: Plasma homocysteine concentrations, smoking status, and MTFHR 677 genotypes were determined in 275 white women who had pregnancies affected by CHDs and 118 white women who had a normal pregnancy. RESULTS: Homocysteine concentrations were significantly higher among women who had affected pregnancies (P < .0001). The highest estimated risk for having a CHD-affected pregnancy was among women who were smokers, were in the highest quartile for homocysteine, and had the MTHFR 677 CC genotype (odds ratio [OR] 11.8; 95% CI 2.6-53.3). CONCLUSION: Many CHDs are due to a complex interaction between lifestyle factors and genetic susceptibilities. Our results suggest that the combined effect of elevations in maternal homocysteine, smoking, and the MTHFR 677 C>T polymorphism increase the risk of having a CHD-affected pregnancy.
Asunto(s)
Cardiopatías Congénitas/etiología , Homocisteína/sangre , Metilenotetrahidrofolato Reductasa (NADPH2)/genética , Polimorfismo Genético , Embarazo/sangre , Embarazo/genética , Fumar/efectos adversos , Adulto , Estudios de Casos y Controles , Citosina , Femenino , Predisposición Genética a la Enfermedad , Genotipo , Cardiopatías Congénitas/genética , Humanos , TiminaRESUMEN
Thimerosol is an antiseptic containing 49.5% ethyl mercury that has been used for years as a preservative in many infant vaccines and in flu vaccines. Environmental methyl mercury has been shown to be highly neurotoxic, especially to the developing brain. Because mercury has a high affinity for thiol (sulfhydryl (-SH)) groups, the thiol-containing antioxidant, glutathione (GSH), provides the major intracellular defense against mercury-induced neurotoxicity. Cultured neuroblastoma cells were found to have lower levels of GSH and increased sensitivity to thimerosol toxicity compared to glioblastoma cells that have higher basal levels of intracellular GSH. Thimerosal-induced cytotoxicity was associated with depletion of intracellular GSH in both cell lines. Pretreatment with 100 microM glutathione ethyl ester or N-acetylcysteine (NAC), but not methionine, resulted in a significant increase in intracellular GSH in both cell types. Further, pretreatment of the cells with glutathione ethyl ester or NAC prevented cytotoxicity with exposure to 15 microM Thimerosal. Although Thimerosal has been recently removed from most children's vaccines, it is still present in flu vaccines given to pregnant women, the elderly, and to children in developing countries. The potential protective effect of GSH or NAC against mercury toxicity warrants further research as possible adjunct therapy to individuals still receiving Thimerosal-containing vaccinations.
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Antiinfecciosos Locales/toxicidad , Glutatión/análogos & derivados , Glutatión/metabolismo , Glutatión/farmacología , Timerosal/toxicidad , Acetilcisteína/farmacología , Antiinfecciosos Locales/antagonistas & inhibidores , Astrocitos/efectos de los fármacos , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Cromatografía Líquida de Alta Presión , Medios de Cultivo , Cistina/farmacología , Relación Dosis-Respuesta a Droga , Electroquímica , Humanos , Neuronas/efectos de los fármacos , Timerosal/antagonistas & inhibidoresRESUMEN
BACKGROUND: Autism is a complex neurodevelopmental disorder that usually presents in early childhood and that is thought to be influenced by genetic and environmental factors. Although abnormal metabolism of methionine and homocysteine has been associated with other neurologic diseases, these pathways have not been evaluated in persons with autism. OBJECTIVE: The purpose of this study was to evaluate plasma concentrations of metabolites in the methionine transmethylation and transsulfuration pathways in children diagnosed with autism. DESIGN: Plasma concentrations of methionine, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), adenosine, homocysteine, cystathionine, cysteine, and oxidized and reduced glutathione were measured in 20 children with autism and in 33 control children. On the basis of the abnormal metabolic profile, a targeted nutritional intervention trial with folinic acid, betaine, and methylcobalamin was initiated in a subset of the autistic children. RESULTS: Relative to the control children, the children with autism had significantly lower baseline plasma concentrations of methionine, SAM, homocysteine, cystathionine, cysteine, and total glutathione and significantly higher concentrations of SAH, adenosine, and oxidized glutathione. This metabolic profile is consistent with impaired capacity for methylation (significantly lower ratio of SAM to SAH) and increased oxidative stress (significantly lower redox ratio of reduced glutathione to oxidized glutathione) in children with autism. The intervention trial was effective in normalizing the metabolic imbalance in the autistic children. CONCLUSIONS: An increased vulnerability to oxidative stress and a decreased capacity for methylation may contribute to the development and clinical manifestation of autism.
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Trastorno Autístico/metabolismo , Homocisteína/metabolismo , Metionina/metabolismo , Estrés Oxidativo , Vitamina B 12/análogos & derivados , Adenosina/sangre , Adenosina/metabolismo , Trastorno Autístico/sangre , Trastorno Autístico/tratamiento farmacológico , Betaína/administración & dosificación , Biomarcadores/sangre , Estudios de Casos y Controles , Niño , Cromatografía Líquida de Alta Presión/métodos , Cistationina/sangre , Cistationina/metabolismo , Cisteína/sangre , Cisteína/metabolismo , Femenino , Glutatión/sangre , Glutatión/metabolismo , Homocisteína/sangre , Humanos , Leucovorina/administración & dosificación , Masculino , Metionina/sangre , Metilación , Estrés Oxidativo/efectos de los fármacos , S-Adenosilhomocisteína/sangre , S-Adenosilhomocisteína/metabolismo , S-Adenosilmetionina/sangre , S-Adenosilmetionina/metabolismo , Vitamina B 12/administración & dosificaciónRESUMEN
Chronic dietary insufficiency of the lipotropic nutrients choline and methionine is hepatocarcinogenic in male rats and certain mouse strains. Despite the fact that DNA hypomethylation is a hallmark of most cancer genomes, the tissue-specific consequences of this alternation with respect to tumorigenesis remain to be determined. In the present study, the folate/methyl deficient model of multistage hepatocarcinogenesis was used to evaluate in vivo alterations in DNA methylation in the liver, the carcinogenesis target tissue, and in non-target tissues, including pancreas, spleen, kidney, and thymus, of male F344 rats. By utilizing the HpaII/MspI-based cytosine extension assay, we demonstrated that the percent of CpG sites that lost methyl groups on both strands progressively increased in liver tissue after 9, 18, and 36 weeks of folate/methyl deficiency. The endogenous activity of DNA methyltransferase in liver of rats fed with folate/methyl deficient diet for the 36-week period gradually increased with time. In contrast, non-target tissues displayed no changes in DNA methylation level or activity of DNA methyltransferase. The failure of DNA methyltransferase to restore and maintain DNA methylation patterns in preneoplastic liver tissue may lead to the establishment of tumor-specific DNA methylation and DNA methyltransferase profiles that are not expressed in normal liver. These results provide additional information about alterations in DNA methylation during early preneoplastic stages of carcinogenesis. They also demonstrate that DNA hypomethylation is localized to tissue that undergoes carcinogenesis, and is not altered in non-target tissues.
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Metilación de ADN , Deficiencia de Ácido Fólico/genética , Neoplasias Hepáticas Experimentales/genética , Hígado/metabolismo , Lesiones Precancerosas/genética , Animales , Carcinoma Hepatocelular/genética , Citosina/metabolismo , Metilasas de Modificación del ADN/metabolismo , ADN de Neoplasias/análisis , Riñón/metabolismo , Masculino , Páncreas/metabolismo , Ratas , Ratas Endogámicas F344 , Bazo/metabolismo , Timo/metabolismoRESUMEN
Uteroplacental insufficiency leads to intrauterine growth retardation (IUGR) and increases the risk of insulin resistance and hypertriglyceridemia in both humans and rats. Postnatal changes in hepatic gene expression characterize the postnatal IUGR rat, despite the transient nature of the initial in utero insult. Phenomena such as DNA methylation and histone acetylation can induce a relatively static reprogramming of gene transcription by altering chromatin infrastructure. We therefore hypothesized that uteroplacental insufficiency persistently affects DNA methylation and histone acetylation in the IUGR rat liver. IUGR rat pups were created by inducing uteroplacental insufficiency through bilateral uterine artery ligation of the pregnant dam on day 19 of gestation. The SssI methyltransferase assay and two-dimensional thin-layer chromatography demonstrated genome-wide DNA hypomethylation in postnatal IUGR liver. To investigate a possible mechanism for this hypomethylation, levels of hepatic metabolites and enzyme mRNAs involved in one-carbon metabolism were measured using HPLC with coulometric electrochemical detection and real-time RT-PCR, respectively. Uteroplacental insufficiency increased IUGR levels of S-adenosylhomocysteine, homocysteine, and methionine in association with decreased mRNA levels of methionine adenosyltransferase and cystathionine-beta-synthase. Western blotting further demonstrated that increased quantities of acetylated histone H3 also characterized the IUGR liver. Increased hepatic levels of S-adenosylhomocysteine can promote DNA hypomethylation, which is often associated with histone hyperacetylation. We speculate that the altered intrauterine milieu associated with uteroplacental insufficiency affects hepatic one-carbon metabolism and subsequent DNA methylation, which thereby alters chromatin dynamics and leads to persistent changes in hepatic gene expression.
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Carbono/metabolismo , Metilación de ADN , Retardo del Crecimiento Fetal/metabolismo , Regulación del Desarrollo de la Expresión Génica/fisiología , Histonas/metabolismo , Circulación Placentaria , Insuficiencia Placentaria/metabolismo , Procesamiento Proteico-Postraduccional , Acetilación , Animales , Cromatina/genética , Cistationina betasintasa/biosíntesis , Cistationina betasintasa/genética , Modelos Animales de Enfermedad , Susceptibilidad a Enfermedades , Inducción Enzimática , Femenino , Retardo del Crecimiento Fetal/etiología , Retardo del Crecimiento Fetal/genética , Edad Gestacional , Hígado/metabolismo , Metionina/metabolismo , Metionina Adenosiltransferasa/biosíntesis , Metionina Adenosiltransferasa/genética , Insuficiencia Placentaria/genética , Embarazo , Ratas , S-Adenosilhomocisteína/metabolismoRESUMEN
Using the folate/methyl-deficient rat model of hepatocarcinogenesis, we obtained evidence that may provide new insights into a major unresolved paradox in DNA methylation and cancer research: the mechanistic basis for genome-wide hypomethylation despite an increase in DNA methyltransferase activity and gene-specific regional hypermethylation. Previous studies revealed that the methyltransferase binds with higher affinity to DNA strand breaks, gaps, abasic sites, and uracil than it does to its cognate hemimethylated CpG sites, consistent with its ancestral function as a DNA repair enzyme. These same DNA lesions are an early occurrence in models of folate and methyl deficiency and are often present in human preneoplastic cells. We hypothesized that the high-affinity binding of the maintenance DNA methyltransferase to unrepaired lesions in DNA could sequester available enzyme away from the replication fork and promote passive replication-dependent demethylation. In support of this possibility, we found that lesion-containing DNA is less efficiently methylated than lesion-free DNA from folate/methyl-deficient rats and that an increase in DNA strand breaks precedes DNA hypomethylation. Despite an adaptive increase in DNA methyltransferase activity, hemimethylated DNA from folate/methyl-deficient rats is progressively replaced by double-stranded unmethylated DNA that is resistant to remethylation with dietary methyl repletion. In promoter regions, the inappropriate binding of the DNA methyltransferase to unrepaired lesions or mispairs may promote local histone deacetylation, methylation, and regional hypermethylation associated with tumor suppressor gene silencing. These insights in an experimental model are consistent with the possibility that DNA lesions may be a necessary prerequisite for the disruption of normal DNA methylation patterns in preneoplastic and neoplastic cells.