Hypermethylation of the alternative AWT1 promoter in hematological malignancies is a highly specific marker for acute myeloid leukemias despite high expression levels

High glucose induces DNA methyltransferase 1 dependent epigenetic reprogramming of the endothelial exosome proteome in type 2 diabetes

In response to hyperglycemia, endothelial cells (ECs) release exosomes with altered protein content and contribute to paracrine signalling, subsequently leading to vascular dysfunction in type 2 diabetes (T2D). High glucose reprograms DNA methylation patterns in various cell/tissue types, including ECs, resulting in pathologically relevant changes in cellular and extracellular proteome. However, DNA methylation-based proteome reprogramming in endothelial exosomes and associated pathological implications in T2D are not known. Hence, in the present study, we used Human umbilical vein endothelial cells (HUVECs), High Fat Diet (HFD) induced diabetic mice (C57BL/6) and clinical models to understand epigenetic basis of exosome proteome regulation in T2D pathogenesis . Exosomes were isolated by size exclusion chromatography and subjected to tandem mass tag (TMT) labelled quantitative proteomics and bioinformatics analysis. Immunoblotting was performed to validate exosome protein signature in clinically characterized individuals with T2D. We observed ECs cultured in high glucose and aortic ECs from HFD mouse expressed elevated DNA methyltransferase1 (DNMT1) levels. Quantitative proteomics of exosomes isolated from ECs treated with high glucose and overexpressing DNMT1 showed significant alterations in both protein levels and post translational modifications which were aligned to T2D associated vascular functions. Based on ontology and gene-function-disease interaction analysis, differentially expressed exosome proteins such as Thrombospondin1, Pentraxin3 and Cystatin C related to vascular complications were significantly increased in HUVECs treated with high glucose and HFD animals and T2D individuals with higher levels of glycated hemoglobin. These proteins were reduced upon treatment with 5-Aza-2'-deoxycytidine. Our study shows epigenetic regulation of exosome proteome in T2D associated vascular complications.

Epigenome editing for targeted DNA (de)methylation: a new perspective in modulating gene expression

Traditionally, it has been believed that inheritance is driven as phenotypic variations resulting from changes in DNA sequence. However, this paradigm has been challenged and redefined in the contemporary era of epigenetics. The changes in DNA methylation, histone modification, non-coding RNA biogenesis, and chromatin remodeling play crucial roles in genomic functions and regulation of gene expression. More importantly, some of these changes are inherited to the next generations as a part of epigenetic memory and play significant roles in gene expression. The sum total of all changes in DNA bases, histone proteins, and ncRNA biogenesis constitutes the epigenome. Continuous progress in deciphering epigenetic regulations and the existence of heritable epigenetic/epiallelic variations associated with trait of interest enables to deploy epigenome editing tools to modulate gene expression. DNA methylation marks can be utilized in epigenome editing for the manipulation of gene expression. Initially, genome/epigenome editing technologies relied on zinc-finger protein or transcriptional activator-like effector protein. However, the discovery of clustered regulatory interspaced short palindromic repeats CRISPR)/deadCRISPR-associated protein 9 (dCas9) enabled epigenome editing to be more specific/efficient for targeted DNA (de)methylation. One of the major concerns has been the off-target effects, wherein epigenome editing may unintentionally modify gene/regulatory element which may cause unintended change/harmful effects. Moreover, epigenome editing of germline cell raises several ethical/safety issues. This review focuses on the recent developments in epigenome editing tools/techniques, technological limitations, and future perspectives of this emerging technology in therapeutics for human diseases as well as plant improvement to achieve sustainable developmental goals.

Comprehensive analysis of TLX2 in pan cancer as a prognostic and immunologic biomarker and validation in ovarian cancer

T cell leukemia homeobox 2 (TLX2) plays an important role in some tumors. Bioinformatics and experimental validation represent a useful way to explore the mechanisms and functions of TLX2 gene in the cancer disease process from a pan cancer perspective. TLX2 was aberrantly expressed in pan cancer and cell lines and correlated with clinical stage. High TLX2 expression was significantly associated with poor overall survival in COAD, KIRC, OC, and UCS. The greatest frequency of TLX2 alterations in pan cancer was amplification. Alterations of NXF2B, MSLNL, PCGF1, INO80B-WBP1, LBX2-AS1, MRPL53, LBX2, TTC31, WDR54, and WBP1 co-occurred in the TLX2 alteration group. PFS was significantly shorter in the TLX2-altered group (n = 6) compared to the TLX2-unaltered group (n = 400). Methylation levels of TLX2 were high in 17 tumors. TLX2 expression was associated with MSI in seven tumors and TMB in five tumors. TLX2 expression was associated with immune infiltration and immune checkpoint genes. TLX2 may be associated with some pathways and chemoresistance. We constructed a possible competing endogenous RNA (ceRNA) network of LINC01010/miR-146a-5p/TLX2 in OC. TLX2 expression was significantly upregulated in ovarian cancer cell lines compared to ovarian epithelial cell lines. Aberrant expression of TLX2 in pan cancer may promote tumorigenesis and progression through different mechanisms. TLX2 may represent an important therapeutic target for human cancers.

Identification of cystic fibrosis transmembrane conductance regulator as a prognostic marker for juvenile myelomonocytic leukemia via the whole-genome bisulfite sequencing of monozygotic twins and data mining

BACKGROUND

Linked deoxyribonucleic acid (DNA) hypermethylation investigations of promoter methylation levels of candidate genes may help to increase the progressiveness and mortality rates of juvenile myelomonocytic leukemia (JMML), which is a unique myelodysplastic/myeloproliferative neoplasm caused by excessive monocyte and granulocyte proliferation in infancy/early childhood. However, the roles of hypermethylation in this malignant disease are uncertain.

METHODS

Bone marrow samples from a JMML patient and peripheral blood samples from a healthy monozygotic twin and an unrelated healthy donor were collected with the informed consent of the participant's parents. Whole-genome bisulfite sequencing (WGBS) was then performed. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to analyze specific differentially methylated region (DMG) related genes. The target genes were screened with Cytoscape and Search Tool for the Retrieval of Interacting Genes/Proteins (STRING), which are gene/protein interaction databases. A data mining platform was used to examine the expression level data of the healthy control and JMML patient tissues in Gene Expression Omnibus data sets, and a survival analysis was performed for all the JMML patients.

RESULTS

The STRING analysis revealed that the red node [i.e., the cystic fibrosis transmembrane conductance regulator (CFTR)] was the gene of interest. The gene-expression microarray data set analysis suggested that the CFTR expression levels did not differ significantly between the JMML patients and healthy controls (P=0.81). A statistically significant difference was observed in the CFTR promoter methylation level but not in the CFTR gene body methylation level. The overall survival analysis demonstrated that a high level of CFTR expression was associated with a worse survival rate in patients with JMML (P=0.039).

CONCLUSIONS

CFTR promoter hypermethylation may be a novel biomarker for the diagnosis, monitoring of disease progression, and prognosis of JMML.

DYSF promotes monocyte activation in atherosclerotic cardiovascular disease as a DNA methylation-driven gene

Dysferlin (DYSF) has drawn much attention due to its involvement in dysferlinopathy and was reported to affect monocyte functions in recent studies. However, the role of DYSF in the pathogenesis of atherosclerotic cardiovascular diseases (ASCVD) and the regulation mechanism of DYSF expression have not been fully studied. In this study, Gene Expression Omnibus (GEO) database and epigenome-wide association study (EWAS) literatures were searched to find the DNA methylation-driven genes (including DYSF) of ASCVD. The hub genes related to DYSF were also identified through weighted correlation network analysis (WGCNA). Regulation of DYSF expression through its promoter methylation status was verified using peripheral blood leucocytes (PBLs) from ASCVD patients and normal controls, and experiments on THP1 cells and Apoe^-/- mice. Similarly, the expressions of DYSF related hub genes, mainly contained SELL, STAT3 and TMX1, were also validated. DYSF functions were then evaluated by phagocytosis, transwell and adhesion assays in DYSF knock-down and overexpressed THP1 cells. The results showed that DYSF promoter hypermethylation up-regulated its expression in clinical samples, THP1 cells and Apoe^-/- mice, confirming DYSF as a DNA methylation-driven gene. The combination of DYSF expression and methylation status in PBLs had a considerable prediction value for ASCVD. Besides, DYSF could enhance the phagocytosis, migration and adhesion ability of THP1 cells. Among DYSF related hub genes, SELL was proven to be the downstream target of DYSF by wet experiments. In conclusion, DYSF promoter hypermethylation upregulated its expression and promoted monocytes activation, which further participated in the pathogenesis of ASCVD.

Developmental and Injury-induced Changes in DNA Methylation in Regenerative versus Non-regenerative Regions of the Vertebrate Central Nervous System

BACKGROUND

Because some of its CNS neurons (e.g., retinal ganglion cells after optic nerve crush (ONC)) regenerate axons throughout life, whereas others (e.g., hindbrain neurons after spinal cord injury (SCI)) lose this capacity as tadpoles metamorphose into frogs, the South African claw-toed frog, Xenopus laevis, offers unique opportunities for exploring differences between regenerative and non-regenerative responses to CNS injury within the same organism. An earlier, three-way RNA-seq study (frog ONC eye, tadpole SCI hindbrain, frog SCI hindbrain) identified genes that regulate chromatin accessibility among those that were differentially expressed in regenerative vs non-regenerative CNS [11]. The current study used whole genome bisulfite sequencing (WGBS) of DNA collected from these same animals at the peak period of axon regeneration to study the extent to which DNA methylation could potentially underlie differences in chromatin accessibility between regenerative and non-regenerative CNS.

RESULTS

Consistent with the hypothesis that DNA of regenerative CNS is more accessible than that of non-regenerative CNS, DNA from both the regenerative tadpole hindbrain and frog eye was less methylated than that of the non-regenerative frog hindbrain. Also, consistent with observations of CNS injury in mammals, DNA methylation in non-regenerative frog hindbrain decreased after SCI. However, contrary to expectations that the level of DNA methylation would decrease even further with axotomy in regenerative CNS, DNA methylation in these regions instead increased with injury. Injury-induced differences in CpG methylation in regenerative CNS became especially enriched in gene promoter regions, whereas non-CpG methylation differences were more evenly distributed across promoter regions, intergenic, and intragenic regions. In non-regenerative CNS, tissue-related (i.e., regenerative vs. non-regenerative CNS) and injury-induced decreases in promoter region CpG methylation were significantly correlated with increased RNA expression, but the injury-induced, increased CpG methylation seen in regenerative CNS across promoter regions was not, suggesting it was associated with increased rather than decreased chromatin accessibility. This hypothesis received support from observations that in regenerative CNS, many genes exhibiting increased, injury-induced, promoter-associated CpG-methylation also exhibited increased RNA expression and association with histone markers for active promoters and enhancers. DNA immunoprecipitation for 5hmC in optic nerve regeneration found that the promoter-associated increases seen in CpG methylation were distinct from those exhibiting changes in 5hmC.

CONCLUSIONS

Although seemingly paradoxical, the increased injury-associated DNA methylation seen in regenerative CNS has many parallels in stem cells and cancer. Thus, these axotomy-induced changes in DNA methylation in regenerative CNS provide evidence for a novel epigenetic state favoring successful over unsuccessful CNS axon regeneration. The datasets described in this study should help lay the foundations for future studies of the molecular and cellular mechanisms involved. The insights gained should, in turn, help point the way to novel therapeutic approaches for treating CNS injury in mammals.

Long Noncoding RNA Expression Profiling Reveals Upregulation of Uroplakin 1A and Uroplakin 1A Antisense RNA 1 under Hypoxic Conditions in Lung Cancer Cells

Hypoxia plays important roles in cancer progression by inducing angiogenesis, metastasis, and drug resistance. However, the effects of hypoxia on long noncoding RNA (lncRNA) expression have not been clarified. Herein, we evaluated alterations in lncRNA expression in lung cancer cells under hypoxic conditions using lncRNA microarray analyses. Among 40,173 lncRNAs, 211 and 113 lncRNAs were up- and downregulated, respectively, in both A549 and NCI-H460 cells. Uroplakin 1A (UPK1A) and UPK1A-antisense RNA 1 (AS1), which showed the highest upregulation under hypoxic conditions, were selected to investigate the effects of UPK1AAS1 on the expression of UPK1A and the mechanisms of hypoxia-inducible expression. Following transfection of cells with small interfering RNA (siRNA) targeting hypoxiainducible factor 1α (HIF-1α), the hypoxia-induced expression of UPK1A and UPK1A-AS1 was significantly reduced, indicating that HIF-1α played important roles in the hypoxiainduced expression of these targets. After transfection of cells with UPK1A siRNA, UPK1A and UPK1A-AS1 levels were reduced. Moreover, transfection of cells with UPK1A-AS1 siRNA downregulated both UPK1A-AS1 and UPK1A. RNase protection assays demonstrated that UPK1A and UPK1A-AS1 formed a duplex; thus, transfection with UPK1A-AS1 siRNA decreased the RNA stability of UPK1A. Overall, these results indicated that UPK1A and UPK1A-AS1 expression increased under hypoxic conditions in a HIF-1α-dependent manner and that formation of a UPK1A/UPK1A-AS1 duplex affected RNA stability, enabling each molecule to regulate the expression of the other.

Promoter DNA Hypermethylation and Paradoxical Gene Activation

DNA methylation is a stable epigenetic modification that contributes to the spatiotemporal regulation of gene expression. The manner in which DNA methylation contributes to transcriptional control is dependent on the biological context, including physiological state and the properties of the DNA itself. Classically, dense promoter DNA methylation is associated with transcriptional repression. However, growing evidence suggests that this association may not always hold true, and promoter hypermethylation now also appears to be associated with high transcriptional activity. Furthermore, in a selection of contexts, increasing levels of promoter methylation correlate directly with increased gene expression. These findings postulate a context-dependent model whereby epigenetic contributions to transcriptional regulation occur in a more complex and dynamic manner. We present current evidence documenting promoter hypermethylation and high levels of gene expression, offer insights into the possible mechanisms by which this occurs, and discuss the potential implications for both research and clinical applications.

Gene-Specific Targeting of DNA Methylation in the Mammalian Genome

DNA methylation is the most widely-studied epigenetic modification, playing a critical role in the regulation of gene expression. Dysregulation of DNA methylation is implicated in the pathogenesis of numerous diseases. For example, aberrant DNA methylation in promoter regions of tumor-suppressor genes has been strongly associated with the development and progression of many different tumors. Accordingly, technologies designed to manipulate DNA methylation at specific genomic loci are very important, especially in the context of cancer therapy. Traditionally, epigenomic editing technologies have centered around zinc finger proteins (ZFP)- and transcription activator-like effector protein (TALE)-based targeting. More recently, however, the emergence of clustered regulatory interspaced short palindromic repeats (CRISPR)-deactivated Cas9 (dCas9)-based editing systems have shown to be a more specific and efficient method for the targeted manipulation of DNA methylation. Here, we describe the regulation of the DNA methylome, its significance in cancer and the current state of locus-specific editing technologies for altering DNA methylation.

Repression of TERRA Expression by Subtelomeric DNA Methylation Is Dependent on NRF1 Binding

Chromosome ends are transcribed into long noncoding telomeric repeat-containing RNA (TERRA) from subtelomeric promoters. A class of TERRA promoters are associated with CpG islands embedded in repetitive DNA tracts. Cytosines in these subtelomeric CpG islands are frequently methylated in telomerase-positive cancer cells, and demethylation induced by depletion of DNA methyltransferases is associated with increased TERRA levels. However, the direct evidence and the underlying mechanism regulating TERRA expression through subtelomeric CpG islands methylation are still to establish. To analyze TERRA regulation by subtelomeric DNA methylation in human cell line (HeLa), we used an epigenetic engineering tool based on CRISPR-dCas9 (clustered regularly interspaced short palindromic repeats - dead CRISPR associated protein 9) associated with TET1 (ten-eleven 1 hydroxylase) to specifically demethylate subtelomeric CpG islands. This targeted demethylation caused an up-regulation of TERRA, and the enhanced TERRA production depended on the methyl-sensitive transcription factor NRF1 (nuclear respiratory factor 1). Since AMPK (AMP-activated protein kinase) is a well-known activator of NRF1, we treated cells with an AMPK inhibitor (compound C). Surprisingly, compound C treatment increased TERRA levels but did not inhibit AMPK activity in these experimental conditions. Altogether, our results provide new insight in the fine-tuning of TERRA at specific subtelomeric promoters and could allow identifying new regulators of TERRA.

The clinical significance of the alternative Wilms tumor gene overexpression-hypermethylation signature in acute myeloid leukemia

BACKGROUND

Wilms tumor 1 (WT1) gene is overexpressed in numerous cancers, including acute myeloid leukemia (AML). The alternative WT1 gene (AWT1) is generated from alternative transcription start site in the WT1 first intron and encodes an N-terminal-truncated protein lacking the repressor domain. Although WT1 overexpression is a common feature in AML, the expression levels of the AWT1 and its underlying epigenetic alterations, as well as their clinical relevance in AML remain unknown.

METHODS

Quantitative assessment of AWT1 gene transcripts was performed using real-time polymerase chain reaction (PCR). Bisulfite PCR followed by pyrosequencing was done to determine the methylation status of the AWT1 promoter. The bone marrow samples were collected at diagnosis and after completion of induction chemotherapy from 80 newly diagnosed AML patients. Forty non-malignant BM samples were recruited as controls.

RESULTS

The AWT1 was significantly overexpressed in AML patients. Robust hypermethylation of the AWT1 promoter was found to be a highly specific and sensitive marker for AML (p < 0.001). Significant positive correlations between the AWT1 expression and methylation levels with BM blast counts at both initial diagnosis and after induction therapy were observed (p < 0.001). AWT1 overexpression at the initial diagnosis of AML was found to be an independent negative factor for complete remission response after induction therapy (p = 0.014).

CONCLUSION

The AWT1 gene overexpression-hypermethylation signature is a characteristic marker that positively correlates with the leukemic burden in AML. AWT1 overexpression at AML diagnosis is an independent negative predictor for CR after induction chemotherapy.

DNA Methylation Events as Markers for Diagnosis and Management of Acute Myeloid Leukemia and Myelodysplastic Syndrome

During the onset and progression of hematological malignancies, many changes occur in cellular epigenome, such as hypo- or hypermethylation of CpG islands in promoter regions. DNA methylation is an epigenetic modification that regulates gene expression and is a key event for tumorigenesis. The continuous search for biomarkers that signal early disease, indicate prognosis, and act as therapeutic targets has led to studies investigating the role of DNA in cancer onset and progression. This review focuses on DNA methylation changes as potential biomarkers for diagnosis, prognosis, response to treatment, and early toxicity in acute myeloid leukemia and myelodysplastic syndrome. Here, we report that distinct changes in DNA methylation may alter gene function and drive malignant cellular transformation during several stages of leukemogenesis. Most of these modifications occur at an early stage of disease and may predict myeloid/lymphoid transformation or response to therapy, which justifies its use as a biomarker for disease onset and progression. Methylation patterns, or its dynamic change during treatment, may also be used as markers for patient stratification, disease prognosis, and response to treatment. Further investigations of methylation modifications as therapeutic biomarkers, which may correlate with therapeutic response and/or predict treatment toxicity, are still warranted.

Quantitative assessment of Wilms tumor 1 expression by real-time quantitative polymerase chain reaction in patients with acute myeloblastic leukemia

BACKGROUND

The Wilms tumor 1 (WT1) gene is originally defined as a tumor suppressor gene and a transcription factor that overexpressed in leukemic cells. It is highly expressed in more than 80% of acute myeloid leukemia (AML) patients, both in bone marrow (BM) and in peripheral blood (PB), and it is used as a powerful and independent marker of minimal residual disease (MRD); we have determined the expression levels of the WT1 by real-time quantitative polymerase chain reaction (RQ-PCR) in PB and BM in 126 newly diagnosed AML patients.

MATERIALS AND METHODS

This study was done in molecular pathology and cancer research center from April 2014 to June 2015, RQ-PCR method was used to determine the WT1 gene expression in BM and/or PB samples from 126 patients of AML, we cloned both WT1 and ABL genes for creating a standard curve, and we calculate copy number of WT1 genes in patients.

RESULTS

A total of 126 AML patients consist of 70 males (55.6%) and 56 females (44.4%), with a median age of 26 years; 104 (81%) patients out of 126 show overexpression of WT1 gene. We also concomitant monitoring of fusion transcripts (PML RARa, AML1-ETO, MLL-MLL, CBFb-MYH11, or DEK-CAN) in our patients, the AML1-ETO group showing remarkably low levels of WT1 compared with other fusion transcript and the CBFB-MYH11 showing high levels of WT1.

CONCLUSION

We conclude that WT1 expression by RQ-PCR in AML patients may be employed as an independent tool to detect MRD in the majority of normal karyotype AML patients.

Distal CpG islands can serve as alternative promoters to transcribe genes with silenced proximal promoters

DNA methylation at the promoter of a gene is presumed to render it silent, yet a sizable fraction of genes with methylated proximal promoters exhibit elevated expression. Here, we show, through extensive analysis of the methylome and transcriptome in 34 tissues, that in many such cases, transcription is initiated by a distal upstream CpG island (CGI) located several kilobases away that functions as an alternative promoter. Specifically, such genes are expressed precisely when the neighboring CGI is unmethylated but remain silenced otherwise. Based on CAGE and Pol II localization data, we found strong evidence of transcription initiation at the upstream CGI and a lack thereof at the methylated proximal promoter itself. Consistent with their alternative promoter activity, CGI-initiated transcripts are associated with signals of stable elongation and splicing that extend into the gene body, as evidenced by tissue-specific RNA-seq and other DNA-encoded splice signals. Furthermore, based on both inter- and intra-species analyses, such CGIs were found to be under greater purifying selection relative to CGIs upstream of silenced genes. Overall, our study describes a hitherto unreported conserved mechanism of transcription of genes with methylated proximal promoters in a tissue-specific fashion. Importantly, this phenomenon explains the aberrant expression patterns of some cancer driver genes, potentially due to aberrant hypomethylation of distal CGIs, despite methylation at proximal promoters.

Targeting histone methylation for cancer therapy: enzymes, inhibitors, biological activity and perspectives

Post-translational methylation of histone lysine or arginine residues plays important roles in gene regulation and other physiological processes. Aberrant histone methylation caused by a gene mutation, translocation, or overexpression can often lead to initiation of a disease such as cancer. Small molecule inhibitors of such histone modifying enzymes that correct the abnormal methylation could be used as novel therapeutics for these diseases, or as chemical probes for investigation of epigenetics. Discovery and development of histone methylation modulators are in an early stage and undergo a rapid expansion in the past few years. A number of highly potent and selective compounds have been reported, together with extensive preclinical studies of their biological activity. Several compounds have been in clinical trials for safety, pharmacokinetics, and efficacy, targeting several types of cancer. This review summarizes the biochemistry, structures, and biology of cancer-relevant histone methylation modifying enzymes, small molecule inhibitors and their preclinical and clinical antitumor activities. Perspectives for targeting histone methylation for cancer therapy are also discussed.

Inhibitor of DNA binding 4 functions as a tumor suppressor and is targetable by 5-aza-2'-deoxycytosine with potential therapeutic significance in Burkitt's lymphoma

Epigenetic gene silencing due to promoter methylation is observed in human neoplasia, including lymphoma and certain cancer types. One important target for gene methylation analysis in non-Hodgkin lymphoma (NHL) is inhibitor of DNA binding 4 (ID4). The present study aimed to investigate the gene methylation status of ID4, the expression of ID4 protein and the effect of demethylating agent 5-aza-2'-deoxycytosine (CdR) in the Raji human Burkitt's lymphoma cell line in vitro. Following assessment of the inhibition of Raji cell growth by various concentrations of CdR, the effects of CdR on the expression of ID4 protein were assessed using the immunocytochemical streptavidin-peroxidase method and semi-quantitative analysis, while apoptosis and cell cycle were determined by flow cytometry. The ID4 gene methylation status of Raji cells was tested using methylation-specific polymerase chain reaction analysis. ID4 was methylated and its protein expression was low in the control group, while ID4 was partly or completely demethylated and its protein expression was upregulated in Raji cells treated with CdR. In addition, CdR induced apoptosis and cell cycle arrest in Raji cells in a dose- and time-dependent manner. These results demonstrated that ID4 is hypermethylated and its protein expression is low in Burkitt's lymphoma cells, while CdR reversed the abnormal DNA methylation and induced re-expression of ID4 protein. Hypermethylation of ID4 promotes the proliferation of Burkitt's lymphoma cells; ID4 may function as a tumor suppressor and can be targeted with demethylating compounds such as CdR for the treatment of Burkitt's lymphoma.

Hidden among the crowd: differential DNA methylation-expression correlations in cancer occur at important oncogenic pathways

DNA methylation is a frequent epigenetic mechanism that participates in transcriptional repression. Variations in DNA methylation with respect to gene expression are constant, and, for unknown reasons, some genes with highly methylated promoters are sometimes overexpressed. In this study we have analyzed the expression and methylation patterns of thousands of genes in five groups of cancer and normal tissue samples in order to determine local and genome-wide differences. We observed significant changes in global methylation-expression correlation in all the neoplasms, which suggests that differential correlation events are frequent in cancer. A focused analysis in the breast cancer cohort identified 1662 genes whose correlation varies significantly between normal and cancerous breast, but whose DNA methylation and gene expression patterns do not change substantially. These genes were enriched in cancer-related pathways and repressive chromatin features across various model cell lines, such as PRC2 binding and H3K27me3 marks. Substantial changes in methylation-expression correlation indicate that these genes are subject to epigenetic remodeling, where the differential activity of other factors break the expected relationship between both variables. Our findings suggest a complex regulatory landscape where a redistribution of local and large-scale chromatin repressive domains at differentially correlated genes (DCGs) creates epigenetic hotspots that modulate cancer-specific gene expression.

Imprinted genes in myeloid lineage commitment in normal and malignant hematopoiesis

Genomic imprinting is characterized by the parent-of-origin monoallelic expression of several diploid genes because of epigenetic regulation. Imprinted genes (IGs) are key factors in development, supporting the ability of a genotype to produce phenotypes in response to environmental stimuli. IGs are highly expressed during prenatal stages but are downregulated after birth. They also affect aspects of life other than growth such as cognition, behavior, adaption to novel environments, social dominance and memory consolidation. Deregulated genomic imprinting leads to developmental disorders and is associated with solid and blood cancer as well. Several data have been published highlighting the involvement of IGs in as early as the very small embryonic-like stem cells stage and further during myeloid lineage commitment in normal and malignant hematopoiesis. Therefore, we have assembled the current knowledge on the topic, based mainly on recent findings, trying not to focus on a particular cluster but rather to have a global view of several different IGs in hematopoiesis.