Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.1.1.37 (DNA methyltransferase)
4,983 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The apoptosis-promoting protein Par-4 has been shown to be down-regulated in Ras-transformed NIH 3T3 fibroblasts through the Raf/MEK/ERK MAPK pathway. Because mutations of the ras gene are most often found in tumors of epithelial origin, we explored the signaling pathways utilized by oncogenic Ras to down-regulate Par-4 in RIE-1 and rat ovarian surface epithelial (ROSE) cells. We determined that constitutive activation of the Raf, phosphatidylinositol 3-kinase, or Ral guanine nucleotide exchange factor effector pathway alone was not sufficient to down-regulate Par-4 in RIE-1 or ROSE cells. However, treatment of Ras-transformed RIE-1 or ROSE cells with the MEK inhibitors U0126 and PD98059 increased Par-4 protein expression. Thus, although oncogenic Ras utilizes the Raf/MEK/ERK pathway to down-regulate Par-4 in both fibroblasts and epithelial cells, Ras activation of an additional signaling pathway(s) is required to achieve the same outcome in epithelial cells. Methylation-specific PCR showed that the par-4 promoter is methylated in Ras-transformed cells through a MEK-dependent pathway and that treatment with the DNA methyltransferase inhibitor azadeoxycytidine restored Par-4 mRNA transcript and protein levels, suggesting that the mechanism for Ras-mediated down-regulation of Par-4 is by promoter methylation. Support for this possibility is provided by our observation that Ras transformation was associated with up-regulation of Dnmt1 and Dnmt3 DNA methyltransferase expression. Finally, ectopic Par-4 expression significantly reduced Ras-mediated growth in soft agar, but not morphological transformation, highlighting the importance of Par-4 down-regulation in specific aspects of Ras-mediated transformation of epithelial cells.
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PMID:Ras-mediated loss of the pro-apoptotic response protein Par-4 is mediated by DNA hypermethylation through Raf-independent and Raf-dependent signaling cascades in epithelial cells. 1583 92

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of autoantibodies against a host of nuclear antigens. The pathogenesis of lupus is incompletely understood. Environmental factors may play a role via altering DNA methylation, a mechanism regulating gene expression. In lupus, genes including CD11a and CD70 are overexpressed in T cells as a result of promoter hypomethylation. T-cell DNA methyltransferase expression is regulated in part by the extracellular signal-regulated kinase (ERK) signaling pathway. In this study, we investigate the effects of decreased ERK pathway signaling in T cells using transgenic animals. We generated a transgenic mouse that inducibly expresses a dominant-negative MEK in T cells in the presence of doxycycline. We show that decreased ERK pathway signaling in T cells results in decreased expression of DNA methyltransferase 1 and overexpression of the methylation-sensitive genes CD11a and CD70, similar to T cells in human lupus. Our transgenic animal model also develops anti-dsDNA antibodies. Interestingly, microarray expression assays revealed overexpression of several interferon-regulated genes in the spleen similar to peripheral blood cells of lupus patients. This model supports the contention that ERK pathway signaling defects in T cells contribute to the development of autoimmunity.
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PMID:Defective T-cell ERK signaling induces interferon-regulated gene expression and overexpression of methylation-sensitive genes similar to lupus patients. 1852 34

Among the many oncogenic variants of the anaplastic lymphoma kinase (ALK), nucleophosmin 1 (NPM)/ALK fusion protein expressed in the subset of T-cell lymphoma (ALK(+)TCL) is currently the best characterized. NPM/ALK activates several signal transduction pathways, including PI3K/AKT, MEK/ERK, mTORC1, STAT3, and STAT5b. In turn, the pathways modulate expression and function of many genes and proteins involved in the key cellular functions such as proliferation, growth, survival, metabolism, and angiogenesis. Recent data indicate that NPM/ALK also promotes immune evasion of the ALK(+)TCL by inducing through STAT3 activation the expression of immunosuppressive cytokines interleukin-10 (IL-10) and transforming growth factor-beta (TGFss) and cell surface protein CD274 (PD-L1, B7-H1). In addition, NPM/ALK protects its own expression by mediating via STAT3 and at least one member of the DNA methyltransferase family DNMT1 epigenetic silencing of the SHP-1 and STAT5a genes. In ALK+TCL cells, SHP-1 and STAT5a proteins act as potent tumor suppressors by promoting degradation of the NPM/ALK protein and inhibiting expression of the NPM/ALK gene, respectively. These findings provide further rationale to therapeutically target ALK and its effector proteins, foremost STAT3. They also suggest that immunotherapeutic approaches to ALK(+)TCL and, possibly, other ALK-driven malignancies may require inhibition of ALK and STAT3 to achieve the optimal clinical efficacy.
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PMID:Anaplastic lymphoma kinase (ALK)-induced malignancies: novel mechanisms of cell transformation and potential therapeutic approaches. 1939 33

Most malignant features of cancer cells are triggered by activated oncogenes and the loss of tumor suppressors due to mutation or epigenetic inactivation. It is still unclear, to what extend the escape of emerging cancer cells from recognition and elimination by the immune system is determined by similar mechanisms. We compared the transcriptomes of HCT116 colorectal cancer cells deficient in DNA methyltransferases (DNMTs) and of cells, in which the RAS pathway as the major growth-promoting signaling system is blocked by inhibition of MAPK. We identified the MHC Class I genes HLA-A1/A2 and the ULBP2 gene encoding 1 of the 8 known ligands of the activating NK receptor NKG2D among a cluster of immune genes up-regulated under the conditions of both DNMT-deficiency and MEK-inhibition. Bisulphite sequencing analyses of HCT116 with DNMT deficiency or after MEK-inhibition showed that de-methylation of the ULPB2 promoter correlated with its enhanced surface expression. The HLA-A promoters were not methylated indicating that components of the HLA assembly machinery were also suppressed in DNMT-deficient and MEK-inhibited cells. Increased HLA-A2 surface expression was correlated with enhanced recognition and lysis by A2-specific CTL. On the contrary, elevated ULBP2 expression was not reflected by enhanced recognition and lysis by NK cells. Cosuppression of HLA Class I and NKG2D ligands and genes encoding peptide transporters or proteasomal genes mediates a strong functional link between RAS activation, DNMT activity and disruption of the antigen presenting system controlling immune recognition in colorectal cancer cells.
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PMID:Down-regulation of HLA Class I and NKG2D ligands through a concerted action of MAPK and DNA methyltransferases in colorectal cancer cells. 1956 44

Increasing evidence suggests tumors are maintained by cancer stem cells; however, their nature remains controversial. In a HoxA9-Meis1 (H9M) model of acute myeloid leukemia (AML), we found that tumor-initiating activity existed in three, immunophenotypically distinct compartments, corresponding to disparate lineages on the normal hematopoietic hierarchy--stem/progenitor cells (Lin(-)kit(+)) and committed progenitors of the myeloid (Gr1(+)kit(+)) and lymphoid lineages (Lym(+)kit(+)). These distinct tumor-initiating cells (TICs) clonally recapitulated the immunophenotypic spectrum of the original tumor in vivo (including cells with a less-differentiated immunophenotype) and shared signaling networks, such that in vivo pharmacologic targeting of conserved TIC survival pathways (DNA methyltransferase and MEK phosphorylation) significantly increased survival. Collectively, H9M AML is organized as an atypical hierarchy that defies the strict lineage marker boundaries and unidirectional differentiation of normal hematopoiesis. Moreover, this suggests that in certain malignancies tumor-initiation activity (or "cancer stemness") can represent a cellular state that exists independently of distinct immunophenotypic definition.
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PMID:Decoupling of tumor-initiating activity from stable immunophenotype in HoxA9-Meis1-driven AML. 2230 58

DNA hypomethylation is a characteristic feature of systemic lupus erythematosus (SLE) immune cells. Numerous reports have implicated the involvement of the MEK/ERK pathway in the reduction of DNA methyltransferase (DNMT) expression, hence inducing the transcription of methylation-sensitive genes in SLE patients. However, the molecular mechanisms involved remain unclear. Here, we investigated whether the catalytic subunit of protein phosphatase 2A (PP2Ac), which is overexpressed in SLE T-cells, contributes to reduced DNA methylation. We show that both chemical suppression and siRNA silencing of PP2Ac in T-cells resulted in sustained phosphorylation of MEK and ERK following stimulation with phorbol 12-myristate 13-acetate and ionomycin. Furthermore, PP2Ac suppression resulted in increased DNMT enzyme activity, DNA hypermethylation, and decreased expression of methylation-sensitive genes. Similarly, in SLE T-cells, suppression of PP2Ac resulted in increased MEK/ERK phosphorylation, enhanced DNMT1 expression and suppressed expression of the methylation-sensitive CD70 gene. Our results demonstrate that PP2A regulates DNA methylation by influencing the phosphorylation of MEK/ERK. We propose that enhanced PP2Ac in SLE T-cells may dephosphorylate and activate the signaling pathway upstream of DNMT1, thus disturbing the tight control of methylation-sensitive genes, which are involved in SLE pathogenesis.
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PMID:The catalytic subunit of protein phosphatase 2A (PP2Ac) promotes DNA hypomethylation by suppressing the phosphorylated mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) kinase (MEK)/phosphorylated ERK/DNMT1 protein pathway in T-cells from controls and systemic lupus erythematosus patients. 2377 84

Cell division is a process by which a mother cell divides into genetically identical sister cells, although sister cells often display considerable diversity. In this report, over 350 sister embryonic stem cells (ESCs) were isolated through a microdissection method, and then expression levels of 48 key genes were examined for each sister cell. Our system revealed considerable diversities between sister ESCs at both pluripotent and differentiated states, whereas the similarity between sister ESCs was significantly elevated in a 2i (MEK and GSK3b inhibitors) condition, which is believed to mimic the ground state of pluripotency. DNA methyltransferase 3a/3b were downregulated in 2i-grown ESCs, and the loss of DNA methyltransferases was sufficient to generate nearly identical sister cells. These results suggest that DNA methylation is a major cause of the diversity between sister cells at the pluripotent states, and thus demethylation per se plays an important role in promoting ESC's self-renewal.
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PMID:Identifying division symmetry of mouse embryonic stem cells: negative impact of DNA methyltransferases on symmetric self-renewal. 2431 70

Most colorectal cancers (CRCs) containing activated BRAF (BRAF[V600E]) have a CpG island methylator phenotype (CIMP) characterized by aberrant hypermethylation of many genes, including the mismatch repair gene MLH1. MLH1 silencing results in microsatellite instability and a hypermutable phenotype. Through an RNAi screen, here we identify the transcriptional repressor MAFG as the pivotal factor required for MLH1 silencing and CIMP in CRCs containing BRAF(V600E). In BRAF-positive human CRC cell lines and tumors, MAFG is bound at the promoters of MLH1 and other CIMP genes, and recruits a corepressor complex that includes its heterodimeric partner BACH1, the chromatin remodeling factor CHD8, and the DNA methyltransferase DNMT3B, resulting in hypermethylation and transcriptional silencing. BRAF(V600E) increases BRAF/MEK/ERK signaling resulting in phosphorylation and elevated levels of MAFG, which drives DNA binding. Analysis of transcriptionally silenced CIMP genes in KRAS-positive CRCs indicates that different oncoproteins direct the assembly of distinct repressor complexes on common promoters.
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PMID:The BRAF oncoprotein functions through the transcriptional repressor MAFG to mediate the CpG Island Methylator phenotype. 2521

Decitabine, a cancer therapeutic that inhibits DNA methylation, produces variable antitumor response rates in patients with solid tumors that might be leveraged clinically with identification of a predictive biomarker. In this study, we profiled the response of human ovarian, melanoma, and breast cancer cells treated with decitabine, finding that RAS/MEK/ERK pathway activation and DNMT1 expression correlated with cytotoxic activity. Further, we showed that KRAS genomic status predicted decitabine sensitivity in low-grade and high-grade serous ovarian cancer cells. Pretreatment with decitabine decreased the cytotoxic activity of MEK inhibitors in KRAS-mutant ovarian cancer cells, with reciprocal downregulation of DNMT1 and MEK/ERK phosphorylation. In parallel with these responses, decitabine also upregulated the proapoptotic BCL-2 family member BNIP3, which is known to be regulated by MEK and ERK, and heightened the activity of proapoptotic small-molecule navitoclax, a BCL-2 family inhibitor. In a xenograft model of KRAS-mutant ovarian cancer, combining decitabine and navitoclax heightened antitumor activity beyond administration of either compound alone. Our results define the RAS/MEK/DNMT1 pathway as a determinant of sensitivity to DNA methyltransferase inhibition, specifically implicating KRAS status as a biomarker of drug response in ovarian cancer.
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PMID:KRAS Genomic Status Predicts the Sensitivity of Ovarian Cancer Cells to Decitabine. 2596 87

Aberrant DNA methylation has been frequently observed in many human cancers, including rhabdomyosarcoma (RMS), the most common soft tissue sarcoma in children. To date, the expression and function of the de novo DNA methyltransferase (DNMT) 3B in RMS have not yet been investigated. Our study show for the first time a significant up-regulation of DNMT3B levels in 14 RMS tumour samples and 4 RMS cell lines in comparison to normal skeletal muscle. Transfection of RD and TE671 cells, two in vitro models of embryonal RMS (ERMS), with a synthetic DNMT3B siRNA decreased cell proliferation by arresting cell cycle at G1 phase, as demonstrated by the reduced expression of Cyclin B1, Cyclin D1 and Cyclin E2, and by the concomitant up-regulation of the checkpoint regulators p21 and p27. DNMT3B depletion also impaired RB phosphorylation status and decreased migratory capacity and clonogenic potential. Interestingly, DNMT3B knock-down was able to commit ERMS cells towards myogenic terminal differentiation, as confirmed by the acquisition of a myogenic-like phenotype and by the increased expression of the myogenic markers MYOD1, Myogenin and MyHC. Finally, inhibition of MEK/ERK signalling by U0126 resulted in a reduction of DNMT3B protein, giving evidence that DNMT3B is a down-stream molecule of this oncogenic pathway.Taken together, our data indicate that altered expression of DNMT3B plays a key role in ERMS development since its silencing is able to reverse cell cancer phenotype by rescuing myogenic program. Epigenetic therapy, by targeting the DNA methylation machinery, may represent a novel therapeutic strategy against RMS.
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PMID:DNMT3B in vitro knocking-down is able to reverse embryonal rhabdomyosarcoma cell phenotype through inhibition of proliferation and induction of myogenic differentiation. 2776 16


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