RESUMEN
The identification of aberrantly hypermethylated genes may lead to the development of new diagnostic markers and the identification of novel targets of epigenetic therapy in myelodysplastic syndromes (MDS). We therefore investigated the methylation status of transcription factor genes KLF5, KLF11, and MAFB, shown to be aberrantly methylated in myelogeneous leukaemia cells, in a series of 115 MDS patient as well as in 25 control subjects. Using quantitative high-resolution pyrosequencing methodology, KLF11, MAFB, and KLF5 were shown for the first time to be hypermethylated in 17 (15%), 8 (7%), and 2 (1.7%) cases, respectively, but not in any of the patients with an isolated 5q-deletion. Patient samples harbouring KLF11 methylation displayed reduced KLF11 mRNA expression and KLF11 hypermethylation correlated with a high International Prognostic Scoring System score (P < 0.05). In conclusion, epigenetic inactivation and subsequent transcriptional repression of the KLF11 gene is quite frequent in MDS. Patients with an isolated 5q-deletion seem to harbour a distinct epigenetic profile.
Asunto(s)
Proteínas de Ciclo Celular/biosíntesis , Metilación de ADN , Epigénesis Genética , Silenciador del Gen , Genes Supresores de Tumor , Síndromes Mielodisplásicos/metabolismo , Proteínas Represoras/biosíntesis , Adulto , Anciano , Anciano de 80 o más Años , Proteínas Reguladoras de la Apoptosis , Proteínas de Ciclo Celular/genética , Femenino , Humanos , Factores de Transcripción de Tipo Kruppel/biosíntesis , Factores de Transcripción de Tipo Kruppel/genética , Factor de Transcripción MafB/biosíntesis , Factor de Transcripción MafB/genética , Masculino , Persona de Mediana Edad , Síndromes Mielodisplásicos/genética , Proteínas Represoras/genéticaAsunto(s)
Azacitidina/análogos & derivados , Inhibidor p15 de las Quinasas Dependientes de la Ciclina/genética , Citogenética , Metilación de ADN/efectos de los fármacos , Leucemia Mieloide Aguda/tratamiento farmacológico , Azacitidina/farmacología , Azacitidina/uso terapéutico , Citogenética/tendencias , Metilación de ADN/genética , Decitabina , Humanos , Leucemia Mieloide Aguda/genética , Masculino , Persona de Mediana Edad , Resultado del TratamientoRESUMEN
Gene silencing through aberrant CpG island methylation is a frequent epigenetic defect in hepatocellular carcinoma (HCC). However, nothing is known as yet whether aberrant hypermethylation occurs already in non-neoplastic liver cells from patients with hereditary haemochromatosis who have a clearly elevated risk for developing HCC. Therefore, quantitative real-time PCR-based methylation analysis of six genes frequently hypermethylated in HCC (RASSF1A, cyclinD2, p16(INK4a), GSTpi1, SOCS-1, APC) was performed for liver biopsies from patients with hereditary haemochromatosis. For genotyping of the HFE gene restriction enzyme analysis and Pyrosequencing were used. Transcriptional repression of hypermethylated genes was assessed using real-time RT-PCR. Eighty-four percent of all samples with severe hepatic iron overload and a mutated HFE gene (but without HCC) had at least one gene hypermethylated. All six genes tested were affected by aberrant hypermethylation, albeit to a different extent: RASSF1A 55%, cyclinD2 45%, p16(INK4a) 32%, GSTpi1 10%, SOCS-1 6%, APC 8%. Concomitant transcriptional down-regulation was shown for RASSF1A, cyclinD2, GSTpi1 and SOCS-1. Biopsies from haemochromatosis patients showed significantly more aberrant hypermethylation than normal liver tissue or benign liver tumours (P < 0.001) and also to a higher degree. This effect is independent of patient age, cirrhosis or hepatitis infection. This is the first report demonstrating that longstanding severe iron overload is frequently associated with epigenetic defects characteristic of HCC, which reflects the increased risk of these lesions to progress to HCC. Thus, changes in DNA methylation patterns are an early event preceding morphological alterations of malignant transformation and represent promising targets for early detection.
Asunto(s)
Carcinoma Hepatocelular/genética , Epigénesis Genética , Hemocromatosis/patología , Neoplasias Hepáticas/genética , Adulto , Metilación de ADN , Hemocromatosis/genética , Humanos , Persona de Mediana EdadRESUMEN
H19 and IGF-2 are two growth regulatory genes located on chromosome 11p15 implicated in tumorigenesis. Both genes are imprinted and regulated reciprocally under many circumstances. In order to elucidate the contribution of H19 and IGF-2 to leukemogenesis, the mRNA expression level of both genes were quantitated in bone marrow biopsies and peripheral blood samples from normal (n=98), chronic myelomonocytic leukemia (CMML, n=43), chronic myelogenous leukemia (CML, n=40) and, acute myelogenous leukemia (AML, n=32) cases. A concomitant reduction of H19 and IGF-2 expression was observed in all leukemic samples compared to the healthy controls. This down-regulation was not accompanied by changes in methylation of the differentially methylated region (DMR). Whereas the H19 gene showed strict monoallelic expression in all informative normal (n=31) and leukemic (n=54) samples, the imprinting pattern of the IGF2 gene was found to be heterogeneous. No correlations between imprinting status (mono- versus biallelic expression), quantitative mRNA expression levels and course of disease were found for the IGF-2 gene. The data suggest a disturbed regulation of the IGF-2/H19 locus in myeloid leukemias which is not caused by loss of imprinting.