Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present study was designed to investigate the potential relationship between CDKN2A (p16) gene hypermethylation, which has reported to be frequently observed in oral squamous cell carcinomas (OSCCs), and expression of human DNA methyltransferases (DNMTs: DNMT1, DNMT3A and DNMT3B). Twenty-five pairs of primary OSCCs and matched normal oral mucosa tissues were examined. The p16 gene was hypermethylated (48%) in the tumors showing significant down-regulation of both mRNA and protein expressions. A demethylation assay on 8 OSCC-derived cell lines was also performed by means of treatment with the demethylating agent, 5-aza-2'-deoxycytidine. Four of 5 cell lines showing down-regulation of the p16 gene, revealed re-activation of gene expression after the treatment. In contrast, frequent over-expression of DNMT mRNA expression, also found in the expression of the proteins, was detected: DNMT1 at 72% and DNMT3A at 56%, and DNMT3B at 64%, respectively. However, we could not identify any statistical significance between p16-hypermethylation status in individual tumors and the expression of any of the three DNMTs. These data suggest that hypermethylation of the p16 gene and up-regulation of DNMTs are involved in oral carcinogenesis, but they may be through different mechanisms.
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PMID:Over-expression of DNA methyltransferases and CDKN2A gene methylation status in squamous cell carcinoma of the oral cavity. 1273 84

Drosophila Asx is a Polycomb group gene. Because Drosophila Asx mutations exhibit anterior and posterior transformations, Drosophila Asx is one of the ETP (Enhancers of trithorax and Polycomb) genes with dual functions in transcriptional activation and silencing. ASXL1 is one of human homologs of Drosophila Asx. Here, we searched for ASXL1-related gene within the human genome by using bioinformatics, and identified the ASXL2 gene. Nucleotide sequence of human ASXL2 cDNA was determined by assembling the nucleotide sequences of human EST AI797346, and partial cDNAs MGC44431 (BC042999) and KIAA1685 (AB051472). Nucleotide sequence of mouse Asxl2 was derived from uncharacterized mouse cDNA 9930017F14 (AK036839). Human ASXL2 (1435 aa) showed 79.4% total-amino-acid identity with mouse Asxl2 (1370 aa), and 29.8% total-amino-acid identity with human ASXL1. ASXN domain (codon 1-86 of ASXL2), ASXM domain (codon 269-380 of ASXL2), and PHD domain (codon 1400-1431 of ASXL2) were conserved between human ASXL2 and ASXL1. Human ASXL2 gene, consisting of at least 13 exons, was mapped to human chromosome 2p23.3, one of recombination hot spots or fragile sites associated with carcinogenesis. The DNMT3A-ASXL2-KIF3C locus on human chromosome 2p23.3 and the DNMT3B-ASXL1-KIF3B locus on human chromosome 20q11.21 were paralogous regions within the human genome. Polycomb group and trithorax group proteins are implicated in embryogenesis and carcinogenesis due to transcriptional regulation of target genes through histone modification and chromatin remodeling. Based on functional conservation and human chromosomal localization, ASXL2 and ASXL1 genes were predicted cancer-associated genes.
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PMID:Identification and characterization of ASXL2 gene in silico. 1288 26

MicroRNAs (miRNAs) are small, noncoding RNAs that regulate expression of many genes. Recent studies suggest roles of miRNAs in carcinogenesis. We and others have shown that expression profiles of miRNAs are different in lung cancer vs. normal lung, although the significance of this aberrant expression is poorly understood. Among the reported down-regulated miRNAs in lung cancer, the miRNA (miR)-29 family (29a, 29b, and 29c) has intriguing complementarities to the 3'-UTRs of DNA methyltransferase (DNMT)3A and -3B (de novo methyltransferases), two key enzymes involved in DNA methylation, that are frequently up-regulated in lung cancer and associated with poor prognosis. We investigated whether miR-29s could target DNMT3A and -B and whether restoration of miR-29s could normalize aberrant patterns of methylation in non-small-cell lung cancer. Here we show that expression of miR-29s is inversely correlated to DNMT3A and -3B in lung cancer tissues, and that miR-29s directly target both DNMT3A and -3B. The enforced expression of miR-29s in lung cancer cell lines restores normal patterns of DNA methylation, induces reexpression of methylation-silenced tumor suppressor genes, such as FHIT and WWOX, and inhibits tumorigenicity in vitro and in vivo. These findings support a role of miR-29s in epigenetic normalization of NSCLC, providing a rationale for the development of miRNA-based strategies for the treatment of lung cancer.
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PMID:MicroRNA-29 family reverts aberrant methylation in lung cancer by targeting DNA methyltransferases 3A and 3B. 1789 Mar 17

The human gene MUC4 encodes a transmembrane mucin, ligand of ErbB2, that is associated with pancreatic tumor progression. In the normal pancreas, MUC4 is not expressed, whereas activation of its expression is observed in the early steps of pancreatic carcinogenesis. The molecular mechanisms responsible for MUC4 gene activation are however still unknown. The MUC4 5'-flanking region being GC-rich and including two CpG islands, we hypothesized that epigenetic regulation may be involved and undertook to decipher the molecular phenomenons implied. By treating cancer cell lines with 5-aza-2'-deoxycytidine (5-aza) and trichostatin A (TSA), we were able to restore MUC4 expression in a cell-specific manner. We showed by bisulfite-treated genomic DNA sequencing and chromatin immunoprecipitation that methylation of five CpG sites and establishment of a repressive histone code at the 5'-untranslated region were associated with MUC4 silencing and impaired its activation by Sp1. Direct involvement of DNMT3A, DNMT3B, HDAC1, and HDAC3 was demonstrated by RNA interference and chromatin immunoprecipitation. Moreover, inhibition of histone deacetylation by TSA was associated with strong MUC4 repression in high-expressing cells. In conclusion, this work shows for the first time the importance of epigenetics in regulating MUC4 expression and may represent a new strategy to inhibit its expression in epithelial tumors.
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PMID:Epigenetic regulation of the human mucin gene MUC4 in epithelial cancer cell lines involves both DNA methylation and histone modifications mediated by DNA methyltransferases and histone deacetylases. 1849 26

The mutagen sensitivity assay is an in vitro measure of DNA repair capacity used to evaluate intrinsic susceptibility for cancer. The high heritability of mutagen sensitivity to different mutagens validates the use of this phenotype to predict cancer susceptibility. However, genetic determinants of mutagen sensitivity have not been fully characterized. Recently, several studies found that three major cytosine DNA methyltransferases (DNMTs), especially DNMT1, have a direct role in the DNA damage response, independent of their methyltransferase activity. This study evaluated the hypothesis that sequence variants in DNMT1, DNMT3A and DNMT3B are associated with mutagen sensitivity induced by the tobacco carcinogen benzo[a]pyrene diol epoxide (BPDE) in 278 cancer-free smokers. Single-nucleotide polymorphisms (n = 134) dispersed over the entire gene and regulatory regions of these DNMTs were genotyped by the Illumina Golden Gate Assay. DNA sequence variation in the DNMT1 and DNMT3B loci was globally associated with breaks per cell (P < 0.04 for both). No global association between DNMT3A and breaks per cell was seen (P = 0.09). Two haplotypes in block1 of DNMT1 (H284) and 3B (H70) were associated with 16 and 24% increase in breaks per cell, respectively. Subjects with three or four adverse haplotypes of both DNMT1 and 3B had a 50% elevation in mean level of breaks per cell compared with persons without adverse alleles (P = 0.004). The association between sequence variants of DNMT1 and 3B and mutagen sensitivity induced by BPDE supports the involvement of these DNMTs in protecting the cell from DNA damage.
Carcinogenesis 2008 Jul
PMID:Haplotypes of DNMT1 and DNMT3B are associated with mutagen sensitivity induced by benzo[a]pyrene diol epoxide among smokers. 1849

Studies centered at the intersection of embryogenesis and carcinogenesis have identified striking parallels involving signaling pathways that modulate both developmental and neoplastic processes. In the prostate, reciprocal interactions between epithelium and stroma are known to influence neoplasia and also exert morphogenic effects via the urogenital sinus mesenchyme. In this study, we sought to determine molecular relationships between aspects of normal prostate development and prostate carcinogenesis. We first characterized the gene expression program associated with key points of murine prostate organogenesis spanning the initial in utero induction of prostate budding through maturity. We identified a highly reproducible temporal program of gene expression that partitioned according to the broad developmental stages of prostate induction, branching morphogenesis, and secretory differentiation. Comparisons of gene expression profiles of murine prostate cancers arising in the context of genetically engineered alterations in the Pten tumor suppressor and Myc oncogene identified significant associations between the profile of branching morphogenesis and both cancer models. Further, the expression of genes comprising the branching morphogenesis program, such as PRDX4, SLC43A1, and DNMT3A, was significantly altered in human neoplastic prostate epithelium. These results indicate that components of normal developmental processes are active in prostate neoplasia and provide further rationale for exploiting molecular features of organogenesis to understand cancer phenotypes.
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PMID:Conserved gene expression programs integrate mammalian prostate development and tumorigenesis. 1922 57

Previously we had discovered loss of DNA methylation at the DNMT3L promoter, an enzymatically-inactive DNA methyltransferase, in squamous cell carcinoma of cervix indicating association between cancer and DNMT3L. This study extends this correlation further by identifying the role of DNMT3L in nuclear reprogramming, an event central to the process of carcinogenesis. We show that in cervical cancer cell lines, overexpression of DNMT3L, which functions by regulating the activity of DNMT3A and DNMT3B, increased cellular proliferation and anchorage-independent growth. Importantly, increased DNMT3L expression resulted in changed morphology of cells but this change was gradual and observed only after several passages. Interestingly, confluent cultures of DNMT3L-overexpressing HeLa cell colonies had characteristics of iPS cells. Concomitant with the morphological changes, expression pattern of genes important in nuclear reprogramming, development and cell cycle were observed to have significantly changed. Many imprinted genes, the known targets of DNMT3L, were downregulated. The slow nature of morphological changes and genome-wide nuclear reprogramming observed upon DNMT3L overexpression reinforces its role in carcinogenesis.
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PMID:Reprogramming of HeLa cells upon DNMT3L overexpression mimics carcinogenesis. 1962 66

DNA methylation patterns are established and maintained by three DNA methyltransferases (DNMT): DNMT1, DNMT3A, and DNMT3B. Although essential for development, methylation patterns are frequently disrupted in cancer and contribute directly to carcinogenesis. Recent studies linking polycomb group repression complexes (PRC1 and PRC2) to the DNMTs have begun to shed light on how methylation is targeted. We identified previously a panel of genes regulated by DNMT3B. Here, we compare these with known polycomb group targets to show that approximately 47% of DNMT3B regulated genes are also bound by PRC1 or PRC2. We chose 44 genes coregulated by DNMT3B and PRC1/PRC2 to test whether these criteria would accurately identify novel targets of epigenetic silencing in colon cancer. Using reverse transcription-PCR, bisulfite genomic sequencing, and pyrosequencing, we show that the majority of these genes are frequently silenced in colorectal cancer cell lines and primary tumors. Some of these, including HAND1, HMX2, and SIX3, repressed cell growth. Finally, we analyzed the histone code, DNMT1, DNMT3B, and PRC2 binding by chromatin immunoprecipitation at epigenetically silenced genes to reveal a novel link between DNMT3B and the mark mediated by PRC1. Taken together, these studies suggest that patterns of epigenetic modifiers and the histone code influence the propensity of a gene to become hypermethylated in cancer and that DNMT3B plays an important role in regulating PRC1 function.
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PMID:DNMT1 and DNMT3B modulate distinct polycomb-mediated histone modifications in colon cancer. 1972 60

Tobacco smoke is an important risk factor for various human cancers, including esophageal cancer. How benzo [a]pyrene diol epoxide (BPDE), a carcinogen present in tobacco smoke as well as in environmental pollution, induces esophageal carcinogenesis has yet to be defined. In this study, we investigated the molecular mechanism responsible for BPDE-suppressed expression of retinoic acid receptor-beta2 (RAR-beta2) in esophageal cancer cells. We treated esophageal cancer cells with BPDE before performing methylation-specific polymerase chain reaction (MSP) to find that BPDE induced methylation of the RAR-beta2 gene promoter. We then performed chromatin immunoprecipitation (ChIP) assays to find that BPDE recruited genes of the methylation machinery into the RAR-beta2 gene promoter. We found that BPDE recruited DNA (cytosine-5-)-methyltransferase 3 alpha (DNMT3A), but not beta (DNMT3B), in a time-dependent manner to methylate the RAR-beta2 gene promoter, which we confirmed by reverse transcription-polymerase chain reaction (RT-PCR) analysis of the reduced RAR-beta2 expression in these BPDE-treated esophageal cancer cell lines. However, BPDE did not significantly change DNMT3A expression, but it slightly reduced DNMT3B expression. DNA methylase inhibitor 5-aza-2'-deoxycytidine (5-Aza) and DNMT3A small hairpin RNA (shRNA) vector antagonized the effects of BPDE on RAR-beta2 expressions. Transient transfection of the DNMT3A shRNA vector also antagonized BPDE's effects on expression of RAR-beta2, c-Jun, phosphorylated extracellular signal-regulated protein kinases 1/2 (ERK1/2), and cyclooxygenase-2 (COX-2), suggesting a possible therapeutic effect. The results of this study form the link between the esophageal cancer risk factor BPDE and the reduced RAR-beta2 expression.
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PMID:Benzo[a]pyrene diol epoxide suppresses retinoic acid receptor-beta2 expression by recruiting DNA (cytosine-5-)-methyltransferase 3A. 2042 65

Promoter hypermethylation mediated by DNA methyltransferases (DNMTs) is the main reason for epigenetic inactivation of tumor suppressor genes (TSGs). Previous studies showed that DNMT1 and DNMT3B play an important role in CpG island methylation in tumorigenesis. Little is known about the role of DNMT3A in this process, especially in hepatocellular carcinoma (HCC). In the present study, increased DNMT3A expression in 3 out of 6 HCC cell lines and 16/25 (64%) HCC tissues implied that DNMT3A is involved in hepatocellular carcinogenesis. Depletion of DNMT3A in HCC cell line SMMC-7721 inhibited cell proliferation and decreased the colony formation (about 65%). Microarray data revealed that 153 genes were upregulated in DNMT3A knockdown cells and that almost 71% (109/153) of them contain CpG islands in their 5' region. 13 of them including PTEN, a crucial tumor suppressor gene in HCC, are genes involved in cell cycle and cell proliferation. Demethylation of PTEN promoter was observed in DNMT3A-depleted cells implying that DNMT3A silenced PTEN via DNA methylation. These results provide insights into the mechanisms of DNMT3A to regulate TSGs by an epigenetic approach in HCC.
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PMID:Depletion of DNMT3A suppressed cell proliferation and restored PTEN in hepatocellular carcinoma cell. 2046 90


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