SEARCH · PubMed Health
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Decitabine is a DNA methyltransferase inhibitor under development by SuperGen Inc and MGI Pharma Inc for the potential treatment of a range of hematological malignancies, including myelodysplastic syndrome, solid tumors and sickle cell disease.
BACKGROUND: The DNA Methyltransferase 1 (DNMTI) gene is among the better known 'epigenetic' systems that can regulate normal and abnormal gene expression as well as create 'hot spots' for DNA mutations. Its role has been studied in a number of malignancies with important implications for involvement in early events of malignant transformation. The present study describes the findings with respect to expression of this gene in human lymphomas studied by Fluorescent In Situ Hybridization (FISH). METHOD: The study was undertaken on randomly selected archival human lymph nodes comprising 50 specimens of normal or reactive lymph nodes and 50 specimens of lymphoma lymph nodes. These were subjected to FISH using oligonucleotide Antisense probes for the DNMT1 mRNA according to standard FISH protocols. Percent cells stained, mean 'dots' stained per cell and staining signal intensity were taken as the criteria for comparing control and lymphoma lymph nodes. Quantitation of probe signals was done both by manual visualisation of the fluorescent signals and computer based image analysis. RESULTS: Data indicated a significantly increased expression of the DNMT1 mRNA in lymphoma cases as compared to controls (p<0.001). CONCLUSION: This implies a possible role of the DNMT1 gene in transformation / oncogenesis in human lymphomas.
To study the methylation in the promoter of LRP15 gene and its relationship with gene expression and to explore the possible mechanism of regulating LRP15 gene methylation, the methylation in the promoter of LRP15 gene in K562 cell line was detected by MS-PCR. Then K562 was exposed to 5-aza-2'-deoxycytidine (CdR) and trichostatin (TSA), to determine whether the silencing of LRP15 gene by de novo methylation could be reversed. As a result, it was confirmed by MS-PCR that the promoter of LRP15 was hypermathylated in K562 cell line, and lost its transcription activity. After CdR, with or without TSA, the silencing of LRP15 gene by de novo methylation can be reversed. Observation demonstrated that the expression of LRP15 was controlled by methylation in its promoter in K562. It is suggested that methyltransferase inhibitor and deacetylase inhibitor may be effective agents in leukemia therapy.
Explore the source record for details and available documents.
BACKGROUND & OBJECTIVE: 5-Aza-2'-deoxycytidine (5-Aza-CdR) is an inhibitor of DNA methyltransferase; it may reactivate methylated antioncogene, therefore, inhibit the growth of cancer cells. This study was to observe the inhibitory effect of 5-Aza-CdR on the growth of human nasopharyngeal carcinoma (NPC) cells and xenografts in nude mice, explore the possible mechanisms, and search for new treatment target of NPC. METHODS: NPC cell line CNE cells were treated with 5-Aza-CdR; the methylation status of death-associated protein kinase (DAPK) gene was evaluated by methylation-specific polymerase chain reaction (PCR). The model of human NPC xenograft in nude mice was constructed and treated with 5-Aza-CdR; the xenograft growth in nude mice was observed, and the mRNA and protein expression of DAPK was detected by reverse transcription-PCR (RT-PCR) and immunohistochemistry. RESULTS: No expression of DAPK mRNA was found in CNE cells and the xenografts in nude mice without treatment of 5-Aza-CdR. After treatment, the expression of DAPK mRNA in CNE cells and the xenografts was increased along with the increasing concentration of 5-Aza-CdR; the growth of CNE cells and the xenografts in nude mice were obviously inhibited, and the methylated DAPK gene was reactivated. Four weeks after treatment, no significant difference was found in body weight of nude mice between 5-Aza-CdR group and control group [(22.35+/-2.02) g vs. (21.68+/-2.14) g, t=0.011, P>0.05]; the volume of xenografts was significantly smaller in 5-Aza-CdR group than in control group [(195.32+/-27.57) mm(3) vs. (343.67+/-23.08) mm(3), t=10.11, P<0.01]. CONCLUSION: 5-Aza-CdR may reactivate antioncogene silenced by de novo methylation, therefore, inhibit the growth of CNE cells in vivo and in vitro.
OBJECTIVE: To explore the role of DNA methyltransferases (DNMT) 1, 3A, 3B in the development of epithelial ovarian carcinoma. METHODS: Semi-quantitative RT-PCR method was used to detect the mRNA levels of DNMT 1, 3A and 3B in the tissues of epithelial ovarian carcinoma from 55 cancer patients (40 primary and 15 recurrent cancer) and 20 normal ovary tissues, and the relevant clinical pathological parameters were analyzed. RESULTS: DNMT1 mRNA levels were 1.15, 3.11, 2.85, respectively in normal ovary, primary and recurrent ovarian epithelial cancer tissues, with significant difference between them (P < 0.05). DNMT3A mRNA levels had no obvious changes in the different groups, being 1.32, 0.71, 1.24, respectively (P > 0.05). DNMT3B mRNA levels were 0.25, 0.60, 2.12, in normal ovary, primary and recurrent ovarian epithelial cancer tissues, respectively and there was a significant increase in recurrent cancer tissues compared with normal and primary ovary cancer tissues (P < 0.01). In the primary ovarian cancer tissues, DNMT1 mRNA levels were over expressed in the tissues of low-moderate differentiated (4.92, 1.38), stage III-IV (6.02, 2.13) and lymphatic metastasis (8.25, 2.40; P < 0.05). DNMT 1, 3A, 3B mRNA were over expressed in primary carcinoma, serous carcinoma and clear cell carcinoma of the ovary (5.64, 1.00, 0.78), in comparison with the other pathologic types (1.76, 0.44, 0.23), the differences were significant (P < 0.05). Using COX regression analysis, and after analyzing the parameters effecting survival in epithelial ovarian cancer tissues, including DNMT1, 3A, 3B mRNA level and pathologic type, differentiation, surgical staging, lymphatic metastasis as well as residue tumor post cytoreductive surgery, we found that the mRNA level of DNMT3B was the only factor affecting survival of ovarian cancer patients. CONCLUSION: DNMT1, 3B mRNA were overexpressed in primary and recurrent epithelial ovarian carcinoma, and they have some correlation with clinical pathology and prognosis of epithelial ovarian carcinoma.
A homozygous deletion of the DOCK8 (dedicator of cytokinesis 8) locus at chromosome 9p24 was found in a lung cancer cell line by array-CGH analysis. Cloning of the full-length DOCK8 cDNA led us to define that the DOCK8 gene encodes a protein consisting of 2,099 amino acids. DOCK8 was expressed in a variety of human organs, including the lungs, and was also expressed in type II alveolar, bronchiolar epithelial and bronchial epithelial cells, which are considered as being progenitors for lung cancer cells. DOCK8 expression was reduced in 62/71 (87%) primary lung cancers compared with normal lung tissue, and the reduction occurred irrespective of the histological type of lung cancer. 5-Aza-2'-deoxy-cytidine and/or Trichostatin A treatments induced DOCK8 expression in lung cancer cell lines with reduced DOCK8 expression. Therefore, epigenetic mechanisms, including DNA methylation and histone deacetylation, were indicated to be involved in DOCK8 down-regulation in lung cancer cells. Further screening revealed homozygous deletions of the DOCK8 gene in a gastric and a breast cancer cell line. DOCK family proteins have been shown to play roles in regulation of migration, morphology, adhesion and growth of cells. Thus, the present results suggest that genetic and epigenetic inactivation of DOCK8 is involved in the development and/or progression of lung and other cancers by disturbing such regulations.
The molecular mechanism for cisplatin (CDDP)-resistance of cancer cells has not yet been clarified, despite extensive studies. Here, we investigated whether death-associated protein (DAP) kinase, an apoptosis modulator, was involved in CDDP-resistance by examining the ME180 human cervical squamous cancer cell line and 6 monoclonal ME180-derived CDDP-resistant subclones. Co-treatment with CDDP and 5-aza-2'-deoxycytidine (5-aza-CdR), a demethylating agent, significantly enhanced the CDDP-sensitivities of the parent cells and CDDP-resistant subclones. Subsequent removal of 5-aza-CdR rapidly reversed the CDDP-sensitivity of the CDDP-resistant subclones to their original levels, whereas the parent cells retained the enhanced CDDP-sensitivity for at least 24 h. Quantitative RT-PCR revealed that the CDDP-resistant subclones expressed higher DNA methyltransferase (DNMT) mRNA levels than the parent cells, suggesting that increased DNMT expressions easily restored the CDDP-resistance of the CDDP-resistant subclones following 5-aza-CdR removal. Although the parent cells showed hypermethylation in the DAP kinase promoter region, corresponding methylated bands were not detected in 2 of the 6 CDDP-resistant subclones by methylation-specific PCR. All 6 CDDP-resistant subclones expressed higher DAP kinase mRNA levels than the parent cells, as evaluated by quantitative RT-PCR. Although DAP kinase protein expression was strongly suppressed in the parent cells and CDDP-resistant subclones, 5-aza-CdR treatment of the parent cells dose-dependently stimulated the DAP kinase protein expression, and this was synergistically enhanced by inhibiting histone deacetylation via trichostatin treatment in addition to 5-aza-CdR. However, DAP kinase protein expression in the CDDP-resistant subclones was not stimulated by treatment with 5-aza-CdR and/or trichostatin. These results indicate that post-transcriptional translation of DAP kinase mRNA is strongly suppressed and insensitive to treatment with 5-aza-CdR and trichostatin in the CDDP-resistant subclones established from ME180 human cervical squamous cancer cells. This CDDP-resistance is accompanied by molecular changes that disturb the post-transcriptional translation of the DAP kinase mRNA, and these molecular changes are transiently restored by demethylation.
Epigenetics, heritable changes in gene expression that do not involve changes in DNA sequence, is known to be involved in disease. Two important epigenetic changes that are known to contribute to disease are abnormal methylation patterns of DNA and modifications of histones in chromatin. This review describes a new development in pharmacology, epigenetic therapy, which attempts to correct these changes. At present two groups of drugs are being developed. One inhibits DNA methyltransferases (DNMTs) resulting in the inhibition of DNA methylation. This group of drugs may prove to be useful in the treatment of cancer where hypermethylation of tumour suppressor genes is known to lead to silencing of these genes. The other group of drugs inhibits histone deacetylases (HDACs) resulting in the accumulation of acetylated histones which are thought to mediate the anticancer effects of these drugs. Both these drug groups have shown promising results in drug trials for the treatment of cancer. Since epigenetic changes are thought to underlie a wide range of diseases, the scope of epigenetic therapy is likely to expand.
DNA methylation is an epigenetic process affecting gene expression and chromatin organization. It can heritably silence or activate transcription of genes without any change in their nucleotide sequences, and for a long time was not recognized as an important regulatory mechanism. However, during the recent years it has been shown that improper methylation, especially hypermethylation of promoter regions, is observed in nearly all steps of tumorigenesis. Aberrant methylation is also the cause of several major pathologies including developmental disorders involving chromosome instabilities and mental retardation. A great progress has been made in our understanding of the enzymatic machinery involved in establishing and maintaining methylation patterns. This allowed for the development of new diagnostic tools and epigenetic treatment therapies. The new approaches hold a great potential; several inhibitors of DNA methyltransferases have already shown very promising therapeutic effects.
OBJECTIVE: To investigate the effect of environmental contaminants on development rate and DNA methyltransferase activity of preimplantation embryos. METHODS: 1-cell embryos were collected from oviduct, in vitro cultured to blastocyst stage in media with or without environmental contaminants. The development rate and DNA methyltransferase activity were determined. RESULTS: The development rates of preimplantation embryos from 1-cell stage to blastocyst stage were not affected by the exposed compounds. However, 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) significantly increased the DNA methyltransferase activity, 2, 2', 3, 3' 4, 4'-polychlorinated biphenyl (PCB153) and diethylstilbestrol (DES) significantly decreased the DNA methyltransferase activity, while p, p'- dichlorodiphenel ethylene (DDE) and dibutyl phthalate (DBP) did not change the DNA methyltransferase activity significantly. CONCLUSION: Exposure to TCDD, DES, and PCB 153 alters the DNA methyltransferase activity in early development stage, which may induce the change of methylation status of genes and affect the development in the later stage.
In the past 40 years, advances in supportive care and development of chemotherapeutic agents have led to improved outcomes in patients with acute myeloid leukemia. High relapse rates following remission have led to extensive efforts to develop techniques and regimens for detecting and eliminating minimal residual disease. However, the best postremission therapy has not been identified. Better understanding of the biology and the molecular pathogenesis of AML has led to the development of new, more specific agents and strategies for AML treatment. Targeted therapy has improved outcomes in some patients. Most of the new agents are less toxic then their predecessors, and they can be used in combination with the more intensive traditional regimens.
The purpose of this study was to determine the effect of the FHIT gene on tumorigenesis of cervical cancer. RT-PCR and MTT were used to detect the expression of FHIT and cell proliferation respectively. Flow cytometry was used to test cell cycle and cell apoptosis. The expression of FHIT was not induced at all four cervical cancer cells treated with demethylating agent 5-aza-2'-deoxycytidine (5-Aza-CdR). However, a constant level of FHIT expression was detected in the human umbilical vein endothelial cell before and after 5-aza-dC treatment. The proliferation of all four cervical cancer cells was inhibited evidently when treated with 5-aza-dC and the inhibiting rate of cell growth along with the increasing concentration of 5-aza-dC. There was no obvious inhibiting effect on the growth of the human umbilical vein endothelial cell treated with 5-aza-dC. An increasing G1 phase and high apoptosis rate were detected in all four cervical cancer cells. However, a negligible change was seen in the human umbilical vein endothelial cell. These results suggest that aberrant methylation of the FHIT gene might be a key mechanism for silenced FHIT gene, which could be reactivated and whose tumor suppressing function could be restored by demethylating agent treatment.
Cancer growth and metastasis require the coordinate change in gene expression of different sets of genes. While genetic alterations can account for some of these changes, many of the changes in gene expression observed in cancer are caused by epigenetic modifications. The epigenome consists of the chromatin and its modifications, the "histone code" as well as the pattern of distribution of covalent modifications of cytosines residing in the dinucleotide sequence CG by methylation. The normal pattern of distribution of DNA methylation is altered in cancer. A number of genes are regionally hypermethylated but many parts of the genome are hypomethylated. Hypermethylation of tumor suppressor genes is involved in silencing of strategic genes. DNA hypermethylation has received much attention and a number of clinical trials are underway with different inhibitors of DNA methylating enzymes. It is now becoming clear however that hypomethylation also plays a role in cancer by activating genes required for invasion and metastasis. The potential therapeutic implications of targeting DNA methylation in cancer are discussed.
The RNA-directed DNA Methylation (RdDM) is one type of epigenetic modification which was firstly discovered in plant. RdDM can directly cause DNA modifications of the genome through RNA-DNA interactions. In plant, both of RdDM and mRNA degradation induced by siRNA can silence sequence specific genes through RNA. They play very significant roles in chromosome rearrangement, defence of virus invasion, regulation of gene expression and many processes of plant development. However, the mechanisms of RdDM are still unclear. In this paper the basic characteristics of RdDM were briefly summarized and advances in studies on mechanisms of RdDM were reviewed. These include the kinds of DNA methyltransferases and their functional mechanisms in RdDM, the relationships between DNA methylation and chromatin modification, and important proteins involved in the RdDM process. In plants, RdDM may occur at both the transcriptional and post-transcriptionnal levels, both of which induce gene silencing. Methylation of the target gene promoter correlates with transcriptional gene silencing (TGS) whereas methylation of the coding sequence is associated with post-transcriptional gene silencing (PTGS). RdDM and RNAi all depend on the similar siRNA and enzymes, such as DCL3, RdR2, SDE4 and AGO4. There are at least three kinds of DNA methyltransferases, DRM1/2, MET1 and CMT3, in pants. They can interact with and modifies all cytidines within the DNA regions homologous to RNA sequence. Furthermore, methylation of lysine 9 in Histone H3 can affect the methylation of cytidines.
Genomic imprinting is an epigenetic mark introduced on a DNA molecule without alteration of the base sequence. Upon replication, the primary mark is propagated to the daughter DNA molecules. Epigenetic DNA modification often serves as a regulatory signal and may play a crucial role in many developmental processes. Although this mode of gene regulation was first discovered in multicellular eukaryotes, cases of imprinting have been recently found in lower eukaryotes, bacteria and phage. Thus it may be reasonable to list DNA modification among the major mechanisms that regulate gene expression.
Sinefungin is a naturally occurring nucleoside isolated from cultures of Streptomyces griseolus and S. incarnatus. It is structurally related to S-adenosyl-methionine (SAM) and S-adenosyl-L-homocysteine (SAH). Its effect and level of action on prokaryotes has not been studied with the same detail as with eukaryotic cells. In this report we describe the effect of sinefungin and SAH on several Streptomyces methyltransferases (DNA and protein MTases) and on other bacterial DNA-MTases. Protein MTases are resistant to sinefungin, whereas DNA-MTases are inhibited. Adenine MTases however, seem more sensitive to this analogue than cytosine MTases.
Explore the source record for details and available documents.