Aberrant CpG-island methylation has non-random and tumour-type-specific patterns

Plant natural modulators in breast cancer prevention: status quo and future perspectives reinforced by predictive, preventive, and personalized medical approach

In contrast to the genetic component in mammary carcinogenesis, epigenetic alterations are particularly important for the development of sporadic breast cancer (BC) comprising over 90% of all BC cases worldwide. Most of the DNA methylation processes are physiological and essential for human cellular and tissue homeostasis, playing an important role in a number of key mechanisms. However, if dysregulated, DNA methylation contributes to pathological processes such as cancer development and progression. A global hypomethylation of oncogenes and hypermethylation of tumor-suppressor genes are characteristic of most cancer types. Moreover, histone chemical modifications and non-coding RNA-associated multi-gene controls are considered as the key epigenetic mechanisms governing the cellular homeostasis and differentiation states. A number of studies demonstrate dietary plant products as actively affecting the development and progression of cancer. "Nutri-epigenetics" focuses on the influence of dietary agents on epigenetic mechanisms. This approach has gained considerable attention; since in contrast to genetic alterations, epigenetic modifications are reversible affect early carcinogenesis. Currently, there is an evident lack of papers dedicated to the phytochemicals/plant extracts as complex epigenetic modulators, specifically in BC. Our paper highlights the role of plant natural compounds in targeting epigenetic alterations associated with BC development, progression, as well as its potential chemoprevention in the context of preventive medicine. Comprehensive measures are stated with a great potential to advance the overall BC management in favor of predictive, preventive, and personalized medical services and can be considered as "proof-of principle" model, for their potential application to other multifactorial diseases.

Zinc Finger Readers of Methylated DNA

DNA methylation is a prevalent epigenetic modification involved in regulating a number of essential cellular processes, including genomic accessibility and transcriptional outcomes. As such, aberrant alterations in global DNA methylation patterns have been associated with a growing number of disease conditions. Nevertheless, the full mechanisms by which DNA methylation information is interpreted and translated into genomic responses is not yet fully understood. Methyl-CpG binding proteins (MBPs) function as important mediators of this essential process by selectively reading DNA methylation signals and translating this information into down-stream cellular outcomes. The Cys₂His₂ zinc finger scaffold is one of the most abundant DNA binding motifs found within human transcription factors, yet only a few zinc finger containing proteins capable of conferring selectivity for mCpG over CpG sites have been characterized. This review summarizes our current structural understanding for the mechanisms by which the zinc finger MBPs evaluated to date read this essential epigenetic mark. Further, some of the biological implications for mCpG readout elicited by this family of MBPs are discussed.

Construction and characterization of regulated cycle inhibiting factors induced upon Tet-On system in human colon cancer cell lines

A previous study has proven that cycle inhibiting factors (Cifs) inhibit Cullin E3 ubiquitin ligases, resulting in cell cycle arrest. More importantly, Cifs are also involved in cancer progression by deamidating Nedd8. Here we aimed to explore a novel insight into the treatment implications of Cifs in colon cancers by Tet-on system. The anticancer activity of Cif by doxycycline induction was investigated in the colon cell lines based upon Tet-On system. The expression of Cif in the colon cancer cells was determined by western blot. Furthermore, the cell viability and flow cytometry analysis were respectively performed to evaluate the cell proliferation and survival of colon cells. More importantly, the p21 and p27 levels were also evaluated after the induction of Cif with Tet-On system. Multiple clones of colon cancer cells for doxycycline-regulated Cif expression were constructed for maintenance purposes including HCT116 and SW480 cell lines. The result of western blot displayed good inducibility of expressing Cif in the cell lines. The clones with Cif preserved their transformed phenotype compared with the control group (clones with GFP or with Cif), in terms of the inhibition of cancer cell proliferation and survival. Furthermore, western blot analysis showed that p27 and p21 were accumulated in the clones with Cif, compared with the colon cancer cell lines with GFP or with Cif. Using the Tet-On system, we developed an efficient approach toward generation of colon cancer cells induced with Cif. These engineered colons tightly controlled Cif expression in vitro, which is a good inducible model system for cancer treatment.

Immobilization of DNA with nitrogen mustard-biotin conjugate for global epigenetic analysis

We report the quantitative analysis of 5-methylcytosine, a representative epigenetic modification in genomic DNA, with an enzyme-linked immunosorbent assay (ELISA). We synthesized a novel hetero-bifunctional linker molecule consisting of nitrogen mustard and biotin to capture DNA on the surface of biosensing devices. The molecule can successfully immobilize genomic DNA on a streptavidin coated 96-well microplate, which was then employed for immunochemical epigenetic assessment. We achieved the sensitive and quantitative detection of 5-mC in genomic DNA samples. The CpG methylation ratios obtained from our system for mouse brain and mouse small intestine genomes were 79% and 82%, respectively. These numbers are in good agreement with the previously reported methylation ratio of 75-85%, which was identified by whole genome bisulfite sequencing. Accordingly, the present technology using our novel bifunctional linker molecule provides a fast, easy, and inexpensive method for epigenetic assessment, without the need for any conventional bisulfite treatment, polymerase chain reaction (PCR), or sequencing.

Diagnostic potential of methylated DAPK in brushing samples of nasopharyngeal carcinoma

Background

The death-associated protein kinase (DAPK) gene is an important member of the apoptotic pathway and is inactivated by abnormal methylation in numerous cancers, including nasopharyngeal carcinoma (NPC). However, the diagnostic value of DAPK methylation in brushing samples and tissue samples of NPC remains unclear.

Methods

We conducted a systematic meta-analysis based on 17 studies (including 386 tissue cases, 233 brushing cases, and 296 blood cases).

Results

Our results revealed an association between methylated DAPK and increased risk of NPC in blood, brushing, and tissue samples. In addition, the comparison of the pooled sensitivity, specificity, and area under the curve of methylated DAPK in brushing and tissue samples demonstrated the non-inferior effectiveness of methylated DAPK in brushing samples to monitor the development of NPC.

RUNX3 Epigenetic Inactivation Is Associated With Estrogen Receptor Positive Breast Cancer

The role of Runt-related transcription factor 3 ( RUNX3) gene in breast cancer remains not fully understood. We studied the correlation between RUNX3 gene promoter methylation and estrogen receptor (ER) expression status in breast cancer. Three breast cancer cell lines and 113 formalin-fixed, paraffin-embedded breast cancer tissue samples were analyzed for RUNX3 expression. Methylation-specific polymerase chain reaction was used to analyze RUNX3 methylation on the samples. Migration and invasion ability were evaluated in MCF7 cell line (RUNX3 methylated) treated with methylation inhibitor 5-Aza-2'-deoxycytidine (5-Aza-CdR) to study the effect of RUNX3 methylation status. Our data showed that the expression of RUNX3 was high in MCF10A but not in MCF7 and SKBR3 cell lines, while the RUNX3 promoter showed hypermethylation in MCF7 but not in MCF10A and SKBR3. In tissues samples, Immunohistochemical (IHC) expression of RUNX3 protein was higher in ER-negative samples than in ER-positive cases, and it was negatively correlated with the methylation status of the RUNX3 gene promoter. Proliferation, migration, and invasion of MCF7 were suppressed when 5-Aza-CdR treated. Also, the hypermethylation status of RUNX3 gene promoter was reversed and RUNX3 expression was increased. In summary, our data suggest that hypermethylation of the RUNX3 gene promoter may play an important role in ER-positive breast tumor progression.

Tissue-specific DNA methylation loss during ageing and carcinogenesis is linked to chromosome structure, replication timing and cell division rates

DNA methylation is an epigenetic mechanism known to affect gene expression and aberrant DNA methylation patterns have been described in cancer. However, only a small fraction of differential methylation events target genes with a defined role in cancer, raising the question of how aberrant DNA methylation contributes to carcinogenesis. As recently a link has been suggested between methylation patterns arising in ageing and those arising in cancer, we asked which aberrations are unique to cancer and which are the product of normal ageing processes. We therefore compared the methylation patterns between ageing and cancer in multiple tissues. We observed that hypermethylation preferentially occurs in regulatory elements, while hypomethylation is associated with structural features of the chromatin. Specifically, we observed consistent hypomethylation of late-replicating, lamina-associated domains. The extent of hypomethylation was stronger in cancer, but in both ageing and cancer it was proportional to the replication timing of the region and the cell division rate of the tissue. Moreover, cancer patients who displayed more hypomethylation in late-replicating, lamina-associated domains had higher expression of cell division genes. These findings suggest that different cell division rates contribute to tissue- and cancer type-specific DNA methylation profiles.

MeCP2 Regulates PTCH1 Expression Through DNA Methylation in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease, in which pathogenesis is not clear. Many research demonstrated that fibroblast-like synoviocytes (FLSs) play a key role in RA pathogenesis, join in the cartilage injury and hyperplasia of the synovium, and contribute to the release of inflammatory cytokines. We used adjuvant arthritis (AA) rats as RA animal models. The methyl-CpG-binding protein 2 (MeCP2) enables the suppressed chromatin structure to be selectively detected in AA FLSs. Overexpression of this protein leads to an increase of integral methylation levels. Some research has confirmed the hedgehog (Hh) signaling pathway plays an important role in RA pathogenesis; furthermore, patched 1 (PTCH1) is a negative fraction of Hh signaling pathway. We used 5-aza-2'-deoxycytidine (5-azadc) as DNA methylation inhibitor. In our research, we found MeCP2 reduced PTCH1 expression in AA FLSs; 5-azadc obstructed the loss of PTCH1 expression. 5-Azadc, treatment of AA FLSs, also blocks the release of inflammatory cytokines. In order to probe the potential molecular mechanism, we assumed the epigenetic participation in the regulation of PTCH1. Results demonstrated that PTCH1 hypermethylation is related to the persistent FLS activation and inflammation in AA rats. Knockdown of MeCP2 using small-interfering RNA technique added PTCH1 expression in AA FLSs. Our results indicate that DNA methylation may offer molecule mechanisms, and the reduced PTCH1 methylation level could regulate inflammation through knockdown of MeCP2. Graphical Abstract PTCH1 is an inhibitory protein of the Hedgehog signaling pathway. Increased expression of PTCH1 can inhibit the expression of Gli1 and Shh, thereby inhibiting the activation of Hedgehog signaling pathway. Inactivated Hedgehog signaling pathway inhibits the secretion of IL-6 and TNF-α. MeCP2 mediates hypermethylation of PTCH1 gene and decreases the expression of PTCH1 protein, thus activating Hedgehog signaling pathway and increasing secretion of IL-6 and TNF-α.

Next-Generation Drugs and Probes for Chromatin Biology: From Targeted Protein Degradation to Phase Separation

Chromatin regulation is a critical aspect of nuclear function. Recent advances have provided detailed information about dynamic three-dimensional organization of chromatin and its regulatory factors. Mechanisms crucial for normal nuclear function and epigenetic control include compartmentalization of biochemical reactions by liquid-phase separated condensates and signal-dependent regulation of protein stability. Synthetic control of these phenomena by small molecules provides deep insight into essential activities such as histone modification, BAF (SWI/SNF) and PBAF remodeling, Polycomb repression, enhancer looping by cohesin and CTCF, as well as many other processes that contribute to transcription. As a result, a complete understanding of the spatiotemporal mechanisms that underlie chromatin regulation increasingly requires the use of fast-acting drugs and chemical probes. Here, we provide a comprehensive review of next-generation chemical biology tools to interrogate the chromatin regulatory landscape, including selective PROTAC E3 ubiquitin ligase degraders, degrons, fluorescent ligands, dimerizers, inhibitors, and other drugs. These small molecules provide important insights into the mechanisms that govern gene regulation, DNA repair, development, and diseases like cancer.

Gene promoter and exon DNA methylation changes in colon cancer development - mRNA expression and tumor mutation alterations

BACKGROUND

DNA mutations occur randomly and sporadically in growth-related genes, mostly on cytosines. Demethylation of cytosines may lead to genetic instability through spontaneous deamination. Aims were whole genome methylation and targeted mutation analysis of colorectal cancer (CRC)-related genes and mRNA expression analysis of TP53 pathway genes.

METHODS

Long interspersed nuclear element-1 (LINE-1) BS-PCR followed by pyrosequencing was performed for the estimation of global DNA metlyation levels along the colorectal normal-adenoma-carcinoma sequence. Methyl capture sequencing was done on 6 normal adjacent (NAT), 15 adenomatous (AD) and 9 CRC tissues. Overall quantitative methylation analysis, selection of top hyper/hypomethylated genes, methylation analysis on mutation regions and TP53 pathway gene promoters were performed. Mutations of 12 CRC-related genes (APC, BRAF, CTNNB1, EGFR, FBXW7, KRAS, NRAS, MSH6, PIK3CA, SMAD2, SMAD4, TP53) were evaluated. mRNA expression of TP53 pathway genes was also analyzed.

RESULTS

According to the LINE-1 methylation results, overall hypomethylation was observed along the normal-adenoma-carcinoma sequence. Within top50 differential methylated regions (DMRs), in AD-N comparison TP73, NGFR, PDGFRA genes were hypermethylated, FMN1, SLC16A7 genes were hypomethylated. In CRC-N comparison DKK2, SDC2, SOX1 genes showed hypermethylation, while ERBB4, CREB5, CNTN1 genes were hypomethylated. In certain mutation hot spot regions significant DNA methylation alterations were detected. The TP53 gene body was addressed by hypermethylation in adenomas. APC, TP53 and KRAS mutations were found in 30, 15, 21% of adenomas, and in 29, 53, 29% of CRCs, respectively. mRNA expression changes were observed in several TP53 pathway genes showing promoter methylation alterations.

CONCLUSIONS

DNA methylation with consecutive phenotypic effect can be observed in a high number of promoter and gene body regions through CRC development.

Studying the expression rate and methylation of Reprimo gene in the blood of patients suffering from gastric cancer

As gastric cancer has no exclusive signals in its initial phases, it is usually diagnosed in advanced phases. Although many researches have been conducted on methylation and diagnosis of cancer’s markers, the methylation and expression of Reprimo gene and its correlation with gastric cancer has not been thoroughly studied. Methylation of Reprimo promoter is a repetitive procedure exclusive to cancer which nullifies its expression and performance. The present research seeks to study the expression and methylation of Reprimo among people suffering with gastric cancer so that it may be used as a biomarker for early diagnosis. Fifty blood samples taken from healthy people (normal samples) and 50 blood samples obtained from gastric cancer patients were analyzed using Real-Time PCR. The methylation status of the promoter of Reprimo was studied using Methylation Specific PCR technique in normal samples and in gastric cancer Iranian patients. We observed reduction in expression rate of Reprimo in the blood samples of patients suffering with gastric cancer in comparison to normal blood samples. A significant correlation was also observed between the expression rate of this gene, age and methylation of its promoter among patients suffering with gastric cancer and various analysis points to a correlation between reduced expressions of Reprimo gene in gastric cancer patients. In conclusion, reduced expression of Reprimo gene and greater levels of methylation of its promoter seems to be promising biomarkers for early diagnosis of gastric cancer.

Let-7e inhibits TNF-α expression by targeting the methyl transferase EZH2 in DENV2-infected THP-1 cells

Tumor necrosis factor α (TNFα), an important inflammatory cytokine, is associated with dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), a severe pathological manifestation of dengue virus (DENV) infection. However, the regulatory mechanism of microRNA on TNFα is currently unknown. Our study showed that the TNFα expression increased immediately and then later decreased, while a marked increase for the miRNA let-7e was detected in dengue virus type 2 (DENV2)-infected peripheral blood mononuclear cells (PBMCs). From this study, we found that let-7e was able to inhibit TNFα expression, but bioinformatics analysis showed that the enhancer of zeste homolog 2 (EZH2) was the potential direct target of let-7e instead of TNFα. EZH2 methyl transferase can produce H3K27me3 and has a negative regulatory role. Using a dual-luciferase reporter assay and Western blotting, we confirmed that EZH2 was a direct target of let-7e and found that siEZH2 could inhibit TNFα expression. In the further study of the regulatory mechanism of EZH2 on TNFα expression, we showed that siEZH2 promoted EZH1 and H3K4me3 expression and inhibited H3K27me3 expression. More importantly, we revealed that siEZH2 down-regulated NF-κB p65 within the nucleus. These findings indicate that the let-7e/EZH2/H3K27me3/NF-κB p65 pathway is a novel regulatory axis of TNFα expression. In addition, we determined the protein differences between siEZH2 and siEZH2-NC by iTRAQ and found a number of proteins that might be associated with TNFα.

Association Between RASSF1A Promoter Methylation and Testicular Germ Cell Tumor: A Meta-analysis and a Cohort Study

BACKGROUND

The RAS association domain family protein 1a (RASSF1A) is a prominent tumor suppressor gene showing altered promoter methylation in testicular germ cell tumors (TGCT). RASSF1A promoter hypermethylation might represent an early event in TGCT tumorigenesis. We investigated whether the RASSF1A promoter methylation in peripheral blood of TGCT patients can be associated with testicular cancer risk.

MATERIALS AND METHODS

Following a meta-analysis, we performed a cohort study including 32 testicular cancer patients and 32 healthy controls. Promoter methylation of the RASSF1A and O⁶-methylguanine-DNA-methyltransferase (MGMT) genes was analyzed using bisulfite pyrosequencing of DNA from peripheral blood.

RESULTS

Meta-analysis showed an odds ratio (OR) of 7.69 for RASSF1A promoter methylation as a risk factor for TGCT. Cohort study found altered methylation of the RASSF1A promoter in blood of TGCT patients. Methylation was higher in TGCT patients before BEP chemotherapy.

CONCLUSION

The meta-analysis indicates a role of the RASSF1A promoter hypermethylation from peripheral blood in TCGT. We confirmed that finding in our cohort study, which represents the first report of changed RASSF1A promoter methylation in peripheral blood TGCT.

Robust prediction of gene regulation in colorectal cancer tissues from DNA methylation profiles

DNA methylation is recognized as one of several epigenetic regulators of gene expression and as potential driver of carcinogenesis through gene-silencing of tumor suppressors and activation of oncogenes. However, abnormal methylation, even of promoter regions, does not necessarily alter gene expression levels, especially if the gene is already silenced, leaving the exact mechanisms of methylation unanswered. Using a large cohort of matching DNA methylation and gene expression samples of colorectal cancer (CRC; n = 77) and normal adjacent mucosa tissues (n = 108), we investigated the regulatory role of methylation on gene expression. We show that on a subset of genes enriched in common cancer pathways, methylation is significantly associated with gene regulation through gene-specific mechanisms. We built two classification models to infer gene regulation in CRC from methylation differences of tumor and normal tissues, taking into account both gene-silencing and gene-activation effects through hyper- and hypo-methylation of CpGs. The classification models result in high prediction performances in both training and independent CRC testing cohorts (0.92 Collapse

Key Words

• DNA methylation
• Epigenetic regulation
• HMGA1
• colorectal cancer
• gene expression
• prediction model

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MESH Headings

• Colorectal Neoplasms/genetics
• DNA Methylation
• Databases, Genetic
• Epigenesis, Genetic
• Gene Expression Profiling/methods
• Gene Expression Regulation, Neoplastic
• HMGA Proteins/genetics
• Humans
• Machine Learning
• Promoter Regions, Genetic
• Sequence Analysis, DNA/methods

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Affiliation(s)

Hagen Klett German Cancer Consortium (DKTK), Heidelberg, Germany German Cancer Research Center (DKFZ), Heidelberg, Germany Institute of Molecular Medicine and Cell Research, Faculty of Medicine and Medical Center, University of Freiburg, Germany
Yesilda Balavarca Division of Preventive Oncology, National Center for Tumor Diseases (NCT) and German Cancer Research Center (DKFZ), Heidelberg, Germany
Reka Toth German Cancer Consortium (DKTK), Heidelberg, Germany Division of Preventive Oncology, National Center for Tumor Diseases (NCT) and German Cancer Research Center (DKFZ), Heidelberg, Germany
Biljana Gigic German Cancer Consortium (DKTK), Heidelberg, Germany Division of Preventive Oncology, National Center for Tumor Diseases (NCT) and German Cancer Research Center (DKFZ), Heidelberg, Germany Department of General, Visceral and Transplantation Surgery, University Clinic Heidelberg, Heidelberg, Germany
Nina Habermann German Cancer Consortium (DKTK), Heidelberg, Germany Division of Preventive Oncology, National Center for Tumor Diseases (NCT) and German Cancer Research Center (DKFZ), Heidelberg, Germany
Dominique Scherer German Cancer Consortium (DKTK), Heidelberg, Germany Division of Preventive Oncology, National Center for Tumor Diseases (NCT) and German Cancer Research Center (DKFZ), Heidelberg, Germany Institute of Medical Biometry and Informatics, University of Heidelberg, Heidelberg, Germany
Petra Schrotz-King German Cancer Consortium (DKTK), Heidelberg, Germany Division of Preventive Oncology, National Center for Tumor Diseases (NCT) and German Cancer Research Center (DKFZ), Heidelberg, Germany
Alexis Ulrich Department of General, Visceral and Transplantation Surgery, University Clinic Heidelberg, Heidelberg, Germany
Peter Schirmacher German Cancer Consortium (DKTK), Heidelberg, Germany Institute of Pathology, University Clinic Heidelberg, Heidelberg, Germany
Esther Herpel Institute of Pathology, University Clinic Heidelberg, Heidelberg, Germany Tissue Bank of the National Center for Tumor Diseases (NCT) Heidelberg, Germany
Hermann Brenner German Cancer Consortium (DKTK), Heidelberg, Germany Division of Preventive Oncology, National Center for Tumor Diseases (NCT) and German Cancer Research Center (DKFZ), Heidelberg, Germany Division of Clinical Epidemiology and Aging Research, German Cancer Research Center (DKFZ), Heidelberg, Germany
Cornelia M. Ulrich German Cancer Consortium (DKTK), Heidelberg, Germany Division of Preventive Oncology, National Center for Tumor Diseases (NCT) and German Cancer Research Center (DKFZ), Heidelberg, Germany Huntsman Cancer Institute and Department of Population Health Sciences, University of Utah, Salt Lake City, UT, USA
Karin B. Michels Institute for Prevention and Cancer Epidemiology, Faculty of Medicine and Medical Center, University of Freiburg, Germany Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles, CA, USA
Hauke Busch Lübeck Institute of Experimental Dermatology and Institute of Cardiogenetics, University of Lübeck, Lübeck, Germany
Melanie Boerries German Cancer Consortium (DKTK), Heidelberg, Germany German Cancer Research Center (DKFZ), Heidelberg, Germany Institute of Molecular Medicine and Cell Research, Faculty of Medicine and Medical Center, University of Freiburg, Germany

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Defining Driver DNA Methylation Changes in Human Cancer

Human malignant tumors are characterized by pervasive changes in the patterns of DNA methylation. These changes include a globally hypomethylated tumor cell genome and the focal hypermethylation of numerous 5′-cytosine-phosphate-guanine-3′ (CpG) islands, many of them associated with gene promoters. It has been challenging to link specific DNA methylation changes with tumorigenesis in a cause-and-effect relationship. Some evidence suggests that cancer-associated DNA hypomethylation may increase genomic instability. Promoter hypermethylation events can lead to silencing of genes functioning in pathways reflecting hallmarks of cancer, including DNA repair, cell cycle regulation, promotion of apoptosis or control of key tumor-relevant signaling networks. A convincing argument for a tumor-driving role of DNA methylation can be made when the same genes are also frequently mutated in cancer. Many of the most commonly hypermethylated genes encode developmental transcription factors, the methylation of which may lead to permanent gene silencing. Inactivation of such genes will deprive the cells in which the tumor may initiate from the option of undergoing or maintaining lineage differentiation and will lock them into a perpetuated stem cell-like state thus providing an additional window for cell transformation.

Candidate gene DNA methylation associations with breast cancer characteristics and tumor progression

AIM

We examined methylation patterns with aggressive tumor phenotypes and investigated demographic, socioeconomic and reproductive predictors of gene methylation.

MATERIALS & METHODS

Pyrosequencing quantified methylation of BRCA1, EGFR, GSTM2, RASSF1, TFF1 and Sat 2. We used quantile regression models to calculate adjusted median methylation values by estrogen and progesterone receptor (ER/PR) status. Bivariate associations between participant characteristics and methylation were examined.

RESULTS

Higher percent methylation of GSTM2 was observed in ER/PR-negative compared with ER/PR-positive tumors in ductal carcinoma in situ (14 vs 2%) and invasive (35 vs 3%) tissue components. Trends in aberrant GSTM2 methylation across tissue components were stronger among ER/PR-negative tumors (p-interaction <0.001). Black women were more likely to have ER/PR-negative tumors (p = 0.01) and show hypermethylation of GSTM2 compared with other women (p = 0.05).

CONCLUSION

GSTM2 promoter hypermethylation may serve as a potential biomarker of aggressive tumor development and a mechanism for ER/PR-negative tumor progression.

Molecular mechanism of hepatitis B virus (HBV) on suppression of raf kinase inhibitor protein (RKIP) expression

Raf kinase inhibitor protein (RKIP) has been shown to be a suppressor of the mitogen-activated protein kinase pathway and is reported to be involved in human malignancy. However, the molecular mechanism of hepatitis B virus (HBV) in regulating RKIP expression is not yet clarified. In this study, we compared RKIP expression in 107 pairs of matched liver cancer and adjacent non-cancerous liver tissues. Among seven HBV-encoded proteins, we found HBV X (HBX) protein could significantly inhibit the expression level of RKIP, indicating that HBV could suppress RKIP expression through regulating HBX. To further elucidate the mechanism, analyses on transcriptional regulation and promoter methylation inhibition were conducted in Huh7 cells. Our results showed that HBX can interact with AP1 protein to inhibit the RKIP transcription. Moreover, we observed that the promoter methylation level of RKIP could be enhanced by HBV. In conclusion, our study revealed that RKIP could act as a molecular marker for HBV-infected liver cancer, but had no tumor-suppressing effect.

Whole-exome sequencing identified mutational profiles of high-grade colon adenomas

Although gene-to-gene analyses identified genetic alterations such as APC, KRAS and TP53 mutations in colon adenomas, it is largely unknown whether there are any others in them. Mutational profiling of high-grade colon adenoma (HGCA) that just precedes colon carcinoma might identify not only novel adenoma-specific genes but also critical genes for its progression to carcinoma. For this, we performed whole-exome sequencing (WES) of 12 HGCAs and identified 11 non-hypermutated and one hypermutated (POLE-mutated) cases. We identified 22 genes including APC, KRAS, TP53, GNAS, NRAS, SMAD4, ARID2, and PIK3CA with non-silent mutations in the cancer Census Genes. Bi-allelic and mono-allelic APC alterations were found in nine and one HGCAs, respectively, while the other two harbored wild-type APC. Five HGCAs harbored either mono-allelic (four HGCAs) or bi-allelic (one HGCA) SMAD4 mutation or 18q loss that had been known as early carcinoma-specific changes. We identified MTOR, ACVR1B, GNAQ, ATM, CNOT1, EP300, ARID2, RET and MAP2K4 mutations for the first time in colon adenomas. Our WES data is largely matched with the earlier 'adenoma-carcinoma model' (APC, KRAS, NRAS and GNAS mutations), but there are newly identified SMAD4, MTOR, ACVR1B, GNAQ, ATM, CNOT1, EP300, ARID2, RET and MAP2K4 mutations in this study. Our findings provide resource for understanding colon premalignant lesions and for identifying genomic clues for differential diagnosis and therapy options for colon adenomas and carcinomas.

Methylation markers differentiate thyroid cancer from benign nodules

PURPOSE

The incidence of thyroid cancer (TC) is increasing. Cytology by itself cannot distinguish TC from some benign nodules especially in certain subtypes of TC. Our immediate goal is to identify DNA methylation markers for early detection of TC and to molecularly differentiate TC subtypes from benign nodules.

METHODS

Promoter methylation status of 21 candidate genes was examined on formalin-fixed paraffin-embedded tissue (FFPE) utilizing quantitative methylation-specific polymerase chain reaction (QMSP) in a retrospective cohort of 329 patients (56% white, 29% African American, 61% female) comprising 71 normal thyroid, 83 benign nodules [follicular adenomas (FA)], 90 follicular TC (FTC) and 85 papillary TC (PTC). All genes were analyzed individually (Kruskal-Wallis and Wilcoxon rank sum tests) and in combination (logistic regression models) to identify genes whose methylation levels might best separate groups.

RESULTS

Combination gene panels TPO and UCHL1 (ROC = 0.607, sensitivity 78%) discriminated FTC from FA, and RASSF1 and TPO (ROC = 0.881, sensitivity 78%) discriminated FTC from normal. Methylation of TSHR distinguished PTC from FTC (ROC = 0.701, sensitivity 84%) and PTC from FA (ROC = 0.685, sensitivity 70%). The six gene panel of TIMP3, RARB2, SERPINB5, RASSF1, TPO and TSHR, which differentiates PTC from normal thyroid, had the best combination sensitivity (91%) and specificity (81%) of the panels addressing discrimination of cancer tissue.

CONCLUSIONS

Aberrant gene methylation used in combination panels may be useful clinically in differentiating FTC and PTC from benign nodules. If confirmed in additional studies, these findings could help reduce the over diagnosis of thyroid cancer and surgeries related to over diagnosis.

Estimation of a significance threshold for epigenome-wide association studies

Epigenome-wide association studies (EWAS) are designed to characterise population-level epigenetic differences across the genome and link them to disease. Most commonly, they assess DNA-methylation status at cytosine-guanine dinucleotide (CpG) sites, using platforms such as the Illumina 450k array that profile a subset of CpGs genome wide. An important challenge in the context of EWAS is determining a significance threshold for declaring a CpG site as differentially methylated, taking multiple testing into account. We used a permutation method to estimate a significance threshold specifically for the 450k array and a simulation extrapolation approach to estimate a genome-wide threshold. These methods were applied to five different EWAS datasets derived from a variety of populations and tissue types. We obtained an estimate of α=2.4×10-7 for the 450k array, and a genome-wide estimate of α=3.6×10-8. We further demonstrate the importance of these results by showing that previously recommended sample sizes for EWAS should be adjusted upwards, requiring samples between ∼10% and ∼20% larger in order to maintain type-1 errors at the desired level.

Identification of DNA methylation associated gene signatures in endometrial cancer via integrated analysis of DNA methylation and gene expression systematically

Objective

Endometrial cancer (EC) is a common gynecologic cancer worldwide. However, the pathogenesis of EC has not been epigenetically elucidated. Here, this study aims to describe the DNA methylation profile and identify favorable gene signatures highly associated with aberrant DNA methylation changes in EC.

Methods

The data regarding DNA methylation and gene expression were downloaded from The Cancer Genome Atlas (TCGA) database. Differentially methylated CpG sites (DMCs), differentially methylated regions (DMRs), and differentially expressed genes (DEGs) were identified, and the relationship between the 2 omics was further analyzed. In addition, weighted CpG site co-methylation network (WCCN) was constructed followed by an integrated analysis of DNA methylation and gene expression data.

Results

Four hundred thirty-one tumor tissues and 46 tissues adjacent tumor of EC patients were analyzed. One thousand one hundred thirty-five DMCs (merging to 10 DMRs), and 1,488 DEGs were obtained between tumor and normal groups, respectively. One hundred forty-eight DMCs-DEGs correlated pairs and 13 regional DMCs-DEGs pairs were obtained. Interestingly, we found that some hub genes in 2 modules among 8 modules of WCCN analysis were down-regulated in tumor samples. Furthermore, protocadherins (PCDHs) clusters, DDP6, TNXB, and ZNF154 were identified as novel deregulated genes with altered methylation in EC.

Conclusion

Based on the analysis of DNA methylation in a systematic view, the potential long-range epigenetic silencing (LRES) composed of PCDHs was reported in ECs for the first time. PCDHs clusters, DDP6, and TNXB were firstly found to be associated with tumorigenesis, and may be novel candidate biomarkers for EC.

DNA methylation is a common molecular alteration in colorectal cancer cells and culture method has no influence on DNA methylation

The present study aimed to explore whether culture method had an influence on DNA methylation in colorectal cancer (CRC). In the present study, CRC cells were cultured in two-dimensional (2D), three-dimensional (3D) and mouse orthotopic transplantation (Tis) cultures. Principal component analysis (PCA) was used for global visualization of the three samples. A Venn diagram was applied for intersection and union analysis for different comparisons. The methylation condition of 5′-C-phosphate-G-3′ (CpG) location was determined using unsupervised clustering analysis. Scatter plots and histograms of the mean β values between 3D vs. 2D, 3D vs. Tis and Tis vs. 2D were constructed. In order to explore the biological function of the genes, gene ontology and Kyoto Encyclopedia of Gene and Genomes (KEGG) pathway analyses were utilized. To explore the influence of culture condition on genes, quantitative methylation specific polymerase chain reaction (QMSP) was performed. The three samples connected with each other closely, as demonstrated by PCA. Venn diagram analysis indicated that some differential methylation positions were commonly shared in the three groups of samples and 16 CpG positions appeared hypermethylated in the three samples. The methylation patterns between the 3D and 2D cultures were more similar than those of 3D and Tis, and Tis and 2D. Results of gene ontology demonstrated that differentially expressed genes were involved in molecular function, cellular components and biological function. KEGG analysis indicated that genes were enriched in 13 pathways, of which four pathways were the most evident. These pathways were pathways in cancer, mitogen-activated protein kinase signaling, axon guidance and insulin signaling. Furthermore, QMSP demonstrated that methylation of mutL homolog, phosphatase and tensin homolog, runt-related transcription factor, Ras association family member, cadherin-1, O-6-methylguanine-DNA-methyltransferase and P16 genes had no obvious difference in 2D, 3D and Tis culture conditions. In conclusion, the culture method had no influence on DNA methylation in CRC cells.

Epigenetic cerebellar diseases

Epigenetics is a growing field of knowledge that is changing our understanding of pathologic processes. For many cerebellar disorders, recent discoveries of epigenetic mechanisms help us to understand their pathophysiology. In this chapter, a short explanation of each epigenetic mechanism (including methylation, histone modification, and miRNA) is followed by references to those cerebellar disorders in which relevant epigenetic advances have been made. The importance of normal timing and distribution of methylation during neurodevelopment is explained. Abnormal methylation and altered gene expression in the developing cerebellum have been related to neurodevelopmental disorders such as autism, Rett syndrome, and fragile X syndrome. DNA packaging by histones is another important epigenetic mechanism in cerebellar functioning. Current knowledge of histone abnormalities in cerebellar diseases such as Friedreich ataxia and spinocerebellar ataxias is reviewed, including implications for new therapeutic approaches to these degenerative diseases. Finally, micro RNAs, the third mechanism to modulate DNA expression, and their role in normal cerebellar development and disease are described. Understanding how genetic and epigenetic mechanisms interact not only in normal cerebellar development but also in disease is a great challenge. However, such understanding will lead to promising new therapeutic possibilities as is already occurring in other areas of medicine.

A Summary of the Biological Processes, Disease-Associated Changes, and Clinical Applications of DNA Methylation

DNA methylation at cytosines followed by guanines, CpGs, forms one of the multiple layers of epigenetic mechanisms controlling and modulating gene expression through chromatin structure. It closely interacts with histone modifications and chromatin remodeling complexes to form the local genomic and higher-order chromatin landscape. DNA methylation is essential for proper mammalian development, crucial for imprinting and plays a role in maintaining genomic stability. DNA methylation patterns are susceptible to change in response to environmental stimuli such as diet or toxins, whereby the epigenome seems to be most vulnerable during early life. Changes of DNA methylation levels and patterns have been widely studied in several diseases, especially cancer, where interest has focused on biomarkers for early detection of cancer development, accurate diagnosis, and response to treatment, but have also been shown to occur in many other complex diseases. Recent advances in epigenome engineering technologies allow now for the large-scale assessment of the functional relevance of DNA methylation. As a stable nucleic acid-based modification that is technically easy to handle and which can be analyzed with great reproducibility and accuracy by different laboratories, DNA methylation is a promising biomarker for many applications.

Detection of prognostic methylation markers by methylC-capture sequencing in acute myeloid leukemia

Clinical and genetic features incompletely predict outcome in acute myeloid leukemia (AML). The value of clinical methylation assays for prognostic markers has not been extensively explored. We assess the prognostic implications of methylC-capture sequencing (MCC-Seq) in patients with de novo AML by integrating DNA methylation and genetic risk stratification. MCC-Seq assessed DNA methylation level in 44 samples. The differentially methylated regions associated with prognostic genetic information were identified. The selected prognostic DNA methylation markers were independently validated in two sets. MCC-Seq exhibited good performance in AML patients. A panel of 12 differentially methylated genes was identified with promoter hyper-differentially methylated regions associated with the outcome. Compared with a low M-value, a high M-value was associated with failure to achieve complete remission (p = 0.024), increased hazard for disease-free survival in the study set (p = 0.039) and poor overall survival in The Cancer Genome Atlas set (p = 0.038). Hematopoietic stem cell transplantation and survival outcomes were not adversely affected by a high M-value (p = 0.271). Our study establishes that MCC-Seq is a stable, reproducible, and cost-effective methylation assay in AML. A 12-gene M-value encompassing epigenetic and genetic prognostic information represented a valid prognostic marker for patients with AML.

Hit-and-run epigenetic editing prevents senescence entry in primary breast cells from healthy donors

Aberrant promoter DNA hypermethylation is a hallmark of cancer; however, whether this is sufficient to drive cellular transformation is not clear. To investigate this question, we use a CRISPR-dCas9 epigenetic editing tool, where an inactive form of Cas9 is fused to DNA methyltransferase effectors. Using this system, here we show simultaneous de novo DNA methylation of genes commonly methylated in cancer, CDKN2A, RASSF1, HIC1 and PTEN in primary breast cells isolated from healthy human breast tissue. We find that promoter methylation is maintained in this system, even in the absence of the fusion construct, and this prevents cells from engaging senescence arrest. Our data show that the key driver of this phenotype is repression of CDKN2A transcript p16 where myoepithelial cells harbour cancer-like gene expression but do not exhibit anchorage-independent growth. This work demonstrates that hit-and-run epigenetic events can prevent senescence entry, which may facilitate tumour initiation.

“Although aberrant promoter DNA hypermethylation is a hallmark of cancer, it is not clear whether it is sufficient to drive transformation. Here, the authors use CRISPR-dCas9 to perform hit-and-run epigenetic editing, which prevents senescence entry in primary breast cells from healthy donors.”

Hypermethylation of BEND5 contributes to cell proliferation and is a prognostic marker of colorectal cancer

Aberrant hypermethylation of CpG islands in tumor suppressor genes (TSGs) contributes to colorectal tumorigenesis. To identify new colorectal cancer (CRC) screening marker, we investigated DNA methylation alterations in novel TSGs. Using HumanMethylation450 BeadChip arrays, CpG regions in BEND5 were the most highly methylated among all genomic regions in 26 colorectal tumors compared to paired non-neoplastic tissues from a Taiwan cohort. Therefore, BEND5 was selected for further analysis. Quantitative methylation-specific real-time PCR revealed that 86.7% (117/135) of CRC patients exhibited hypermethylated BEND5. Real-time reverse transcription PCR identified that BEND5 mRNA expression was downregulated in 68% (32/47) of the analyzed samples. BEND5 hypermethylation was associated with poor overall survival (OS) in Taiwan patients with early-stage CRC (P = 0.037). In a CRC tissue set from South Korea, OS was higher in patients with high BEND5 protein expression than in those with low BEND5 protein expression (P = 0.037) by using immunohistochemistry assays. Consistently, BEND5 hypermethylation was associated with poor OS in patients with early-stage CRC in The Cancer Genome Atlas (TCGA) data set (P = 0.003). Multivariate Cox proportional hazards regression analysis further supported that hypermethylation of BEND5 genes was significantly associated with OS in Taiwan and TCGA CRC patients (P = 0.023 and 0.033, respectively). Finally, the cell model assay with transient transfection of BEND5 or si-BEND5 knockdown indicated that BEND5 inhibited cancer cell proliferation. In conclusion, epigenetic alteration in the candidate TSG BEND5 contributes to colorectal cancer development and is a prognostic marker of CRC.

Liquid Biopsies for Assessing Metastatic Melanoma Progression

The field of genomic biomarkers in melanoma has evolved dramatically in the past few decades. Whereas much of the prior focus was on molecular assessment of tumor tissue, circulating tumor cells (CTCs), and cell-free circulating tumor DNA (ctDNA) as sources of a "liquid biopsy" in cancer patients provide promising potential as a method to assess tumor progression, identify targets for therapy, and evaluate clinical response to treatment. Blood biomarker assays have the advantage of being noninvasive, allow for dynamic evaluation of disease over a serial time frame, and help to address the issue of tissue sampling bias and tumor heterogeneity. However, there remains an assortment of technologies and techniques to isolate and detect CTCs and ctDNA and a standardized method has yet to be established. Despite these challenges, multiple studies have already demonstrated the clinical prognostic utility of blood-based genomic biomarker assays. With the advent of next-generation sequencing and genome-wide ctDNA analysis, this will undoubtedly lead to an improved understanding of tumor progression, help to identify new targets for treatment, and improve monitoring of treatment response and development of resistance.

Gene-body hypermethylation controlled cryptic promoter and miR26A1-dependent EZH2 regulation of TET1 gene activity in chronic lymphocytic leukemia

The Ten-eleven-translocation 1 (TET1) protein is a member of dioxygenase protein family that catalyzes the oxidation of 5-methylcytosine to 5-hydroxymethylcytosine. TET1 is differentially expressed in many cancers, including leukemia. However, very little is known about mechanism behind TET1 deregulation. Previously, by characterizing global methylation patterns in CLL patients using MBD-seq, we found TET1 as one of the differentially methylated regions with gene-body hypermethylation. Herein, we characterize mechanisms that control TET1 gene activity at the transcriptional level. We show that treatment of CLL cell lines with 5-aza 2´-deoxycytidine (DAC) results in the activation of miR26A1, which causes decrease in both mRNA and protein levels of EZH2, which in turn results in the decreased occupancy of EZH2 over the TET1 promoter and consequently the loss of TET1 expression. In addition, DAC treatment also leads to the activation of antisense transcription overlapping the TET1 gene from a cryptic promoter, located in the hypermethylated intronic region. Increased expression of intronic transcripts correlates with decreased TET1 promoter activity through the loss of RNA Pol II occupancy. Thus, our data demonstrate that TET1 gene activation in CLL depends on miR26A1 regulated EZH2 binding at the TET1 promoter and silencing of novel cryptic promoter by gene-body hypermethylation.

High Resolution Imaging of DNA Methylation Dynamics using a Zebrafish Reporter

As one of the major epigenetic modifications, DNA methylation is constantly regulated during embryonic development, cell lineage commitment, and pathological processes. To facilitate real-time observation of DNA methylation, we generated a transgenic zebrafish reporter of DNA methylation (zebraRDM) via knockin of an mCherry-fused methyl-CpG binding domain (MBD) probe driven by the bactin2 promoter. The probe colocalized with heterochromatin, and its intensity was positively correlated with 5 mC immunostaining at a subcellular resolution in early embryos. Biochemical assays indicated that cells with stronger fluorescence maintained a higher level of DNA methylation, and time-lapse imaging at the blastula stage showed that the level of DNA methylation was transiently strengthened during mitosis. By crossing zebraRDM with other fluorescent transgenic lines, we demonstrate that the reporter can visually distinguish different cell lineages in organs like the heart. Our zebraRDM reporter therefore serves as a convenient and powerful tool for high-resolution investigation of methylation dynamics in live animals.

Epigenetic regulation of the circadian clock: role of 5-aza-2'-deoxycytidine

We have been investigating transcriptional regulation of the BMAL1 gene, a critical component of the mammalian clock system including DNA methylation. Here, a more detailed analysis of the regulation of DNA methylation of BMAL1 proceeded in RPMI8402 lymphoma cells. We found that CpG islands in the BMAL1 and the PER2 promoters were hyper- and hypomethylated, respectively and that 5-aza-2'-deoxycytidine (aza-dC) not only enhanced PER2 gene expression but also PER2 oscillation within 24 h in RPMI8402 cells. That is, such hypermethylation of CpG islands in the BMAL1 promoter restricted PER2 expression which was recovered by aza-dC within 1 day in these cells. These results suggest that the circadian clock system can be recovered through BMAL1 expression induced by aza-dC within a day. The RPIB9 promoter of RPMI8402 cells, which is a methylation hotspot in lymphoblastic leukemia, was also hypermethylated and aza-dC gradually recovered RPIB9 expression in 3 days. In addition, methylation-specific PCR revealed a different degree of aza-dC-induced methylation release between BMAL1 and RPIB9 These results suggest that the aza-dC-induced recovery of gene expression from DNA methylation is dependent on a gene, for example the rapid response to demethylation by the circadian system, and thus, is of importance to clinical strategies for treating cancer.

A six-CpG panel with DNA methylation biomarkers predicting treatment response of chemoradiation in esophageal squamous cell carcinoma

BACKGROUND

Prognosis of esophageal squamous cell carcinoma (ESCC) patients remains poor, and the chemoradiotherapy (CRT) applied to ESCC patients often failed. Therefore, development of biomarkers to predict CRT response is immensely important for choosing the best treatment strategy of an individual patient.

METHODS

The methylation array and pyrosequencing methylation assay were performed in pre-treatment endoscopic biopsies to identify probes with differential CpG methylation levels between good and poor CRT responders in a cohort of 12 ESCC patients. Receiver operating characteristic curves and multivariate logistic regressions were conducted to build the risk score equation of selected CpG probes in another cohort of 91 ESCC patients to predict CRT response. Kaplan-Meier analysis was used to estimate progression-free survival or time-to-progression of patients predicted with good and poor CRT responses.

RESULTS

Nine differentially methylated CpG probes were identified to be associated with CRT response. A risk score equation comprising six CpG probes located in IFNGR2, KCNK4, NOTCH4, NPY, PAX6, and SOX17 genes were built. The risk score was derived from the sum of each probe multiplied by its corresponding coefficient. Such a risk score has a good prediction performance in discriminating poor CRT responders from good responders (AUC: 0.930). Moreover, poor CRT responders predicted by risk score significantly had poorer prognosis in terms of shorter progression-free survival and time-to-progression (p = 0.004-0.008).

CONCLUSION

We established a proof-of-concept CRT response prediction panel consisting of six-CpG methylation biomarkers in identifying ESCC patients who are at high risk of CRT failure and need intensive care.

Genetic and epigenetic patterns in patients with the head-and-neck paragangliomas associate with differential clinical characteristics

PURPOSE

In addition to genetic alterations, the importance of a CpG island methylator phenotype, characterized by methylation of multiple tumour-suppressor genes (TSGs), has been acknowledged in many cancer types. This study was done to determine the impact of genetic and epigenetic patterns on the clinical characteristics of the head and neck paragangliomas (HNPGLs).

METHODS

The retrospective study examined a series of 37 patients with HNPGLs who underwent surgical resection between 2010 and 2015. The mutations in the succinate dehydrogenase (SDH) genes were detected using direct DNA sequencing. Aberrant hypermethylation of the CpG islands of a panel of ten TSGs was also analysed using methylation-specific PCR.

RESULTS

Direct sequencing demonstrated the presence of germline SDH mutations in ten HNPGLs. Comparisons of clinical features between mutated and non-mutated HNPGLs established an association of SDH mutations with progressive phenotypes, including an earlier formation, multiple lesions, or malignancy. There was also a significant correlation between the presence of SDH mutations and the number of TSGs methylated in HNPGLs. The SDH-related tumours were therefore more likely to suffer from a CpG island methylator phenotype. Four differentially methylated TSGs in mutated tumours vs non-mutated counterparts were identified with inefficient expression through Real-Time PCR analysis.

CONCLUSIONS

Our results suggested that epigenetic inactivation on multiple TSGs may serve as a key mechanism for the progressive behaviors of SDH-mutated HNPGLs. Thus, an interplay between genetic status, epigenetic alterations, and clinical features might be established in the disease.

DNA methylation: an epigenetic mark of cellular memory

DNA methylation is a stable epigenetic mark that can be inherited through multiple cell divisions. During development and cell differentiation, DNA methylation is dynamic, but some DNA methylation patterns may be retained as a form of epigenetic memory. DNA methylation profiles can be useful for the lineage classification and quality control of stem cells such as embryonic stem cells, induced pluripotent cells and mesenchymal stem cells. During cancer initiation and progression, genome-wide and gene-specific DNA methylation changes occur as a consequence of mutated or deregulated chromatin regulators. Early aberrant DNA methylation states occurring during transformation appear to be retained during tumor evolution. Similarly, DNA methylation differences among different regions of a tumor reflect the history of cancer cells and their response to the tumor microenvironment. Therefore, DNA methylation can be a useful molecular marker for cancer diagnosis and drug treatment.

A New Approach to Evaluating Aberrant DNA Methylation Profiles in Hepatocellular Carcinoma as Potential Biomarkers

Hypermethylation of CpG islands in the promoter region of tumor suppressor genes (TSGs) and their subsequent silencing is thought to be one of the main mechanisms of carcinogenesis. MBD2b enrichment coupled with a NimbleGen array was applied to examine the genome-wide CpG island methylation profile of hepatocellular carcinoma (HCC). Hypermethylated DNA of 58 pairs of HCC and adjacent tissue samples was enriched and hybridized in the same array. Aberrant hypermethylated peaks of HCC and adjacent tissues were screened and annotated after data processing using NimbleScan2.5 and our newly developed Weighting and Scoring (WAS) method, respectively. Validation using bisulfite sequencing of randomly selected ANKRD45, APC, CDX1, HOXD3, PTGER and TUBB6 genes demonstrated significant hypermethylation modification in HCC samples, consistent with the array data.

A pre-neoplastic epigenetic field defect in HCV-infected liver at transcription factor binding sites and polycomb targets

The predisposition of patients with Hepatitis C virus (HCV) infection to hepatocellular carcinoma (HCC) involves components of viral infection, inflammation and time. The development of multifocal, genetically distinct tumours is suggestive of a field defect affecting the entire liver. The molecular susceptibility mediating such a field defect is not understood. One potential mediator of long-term cellular reprogramming is heritable (epigenetic) regulation of transcription, exemplified by DNA methylation. We studied epigenetic and transcriptional changes in HCV-infected livers in comparison with control, uninfected livers and HCC, allowing us to identify pre-neoplastic epigenetic and transcriptional events. We find the HCV-infected liver to have a pattern of acquisition of DNA methylation targeted to candidate enhancers active in liver cells, enriched for the binding sites of the FOXA1, FOXA2 and HNF4A transcription factors. These enhancers can be subdivided into those proximal to genes implicated in liver cancer or to genes involved in stem cell development, the latter distinguished by increased CG dinucleotide density and polycomb-mediated repression, manifested by the additional acquisition of histone H3 lysine 27 trimethylation (H3K27me3). Transcriptional studies on our samples showed that the increased DNA methylation at enhancers was associated with decreased local gene expression, results validated in independent samples from The Cancer Genome Atlas. Pharmacological depletion of H3K27me3 using the EZH2 inhibitor GSK343 in HepG2 cells suppressed cell growth and also revealed that local acquired DNA methylation was not dependent upon the presence of polycomb-mediated repression. The results support a model of HCV infection influencing the binding of transcription factors to cognate sites in the genome, with consequent local acquisition of DNA methylation, and the added repressive influence of polycomb at a subset of CG-dense cis-regulatory sequences. These epigenetic events occur before neoplastic transformation, resulting in what may be a pharmacologically reversible epigenetic field defect in HCV-infected liver.

Correlation between the DNA methylation and gene expression of IGFBP5 in breast cancer

BACKGROUND

The insulin-like growth factor binding protein5 (IGFBP5) is often dysregulated in human cancers and considered neither a tumor suppressor nor an oncogene.

OBJECTIVE

We aim to examine the reason of the changeable gene regulation of IGFBP5 in the case of methylation in breast cancer.

METHODS

We used methyl-specific polymerase (MSP) chain reaction to detect CpG methylation of IGFBP5 promoter and exon-I in breast cancer and adjacent tissues. Gene expression is evaluated by quantative polymerase chain reaction (qPCR).

RESULTS

IGFBP5 methylation was detected in 24 of 58 (41%) and 54 of 56 (96.5%) promoter and exon-I site respectively in tumor tissues. In adjacent tissues 17 of 58 (29%) and 53 of 56 (96.5%) was methylated. IGFBP5 expression was higher estrogene receptor (ER)(+) than ER(-) patients (p = 0.0549). Beside, we found a positive correlation between the expression of IGFBP5 and G2 tumor grade (p = 0.0131). However, no correlation was observed between IGFBP5 expression and age, menopause or the presence of lymph node metastasis (p > 0.05).

CONCLUSIONS

In summary, our results showed that IGFBP5 promoter and exon-I methylation did not have any differences between tumor and adjacent tissues so that IGFBP5 methylation did not change IGFBP5 gene regulation in breast cancer. This is the first study investigating the IGFBP5 gene methylation in breast cancer.

High-throughput sequencing offers new insights into 5-hydroxymethylcytosine

Chemical modifications of DNA comprise epigenetic mechanisms that contribute to the maintenance of cellular activities and memory. Although the function of 5-methylcytosine (5-mC) has been extensively studied, little is known about the function(s) of relatively rarer and underappreciated cytosine modifications including 5-hydroxymethylcytosine (5-hmC). The discovery that ten-eleven translocation (Tet) proteins mediate conversion of 5-mC to 5-hmC, and other oxidation derivatives, sparked renewed interest to understand the biological role of 5-hmC. Studies examining total 5-hmC levels revealed the highly dynamic yet tissue-specific nature of this modification, implicating a role in epigenetic regulation and development. Intriguingly, 5-hmC levels are highest during early development and in the brain where abnormal patterns of 5-hmC have been observed in disease conditions. Thus, 5-hmC adds to the growing list of epigenetic modifications with potential utility in clinical applications and warrants further investigation. This review discusses the emerging functional roles of 5-hmC in normal and disease states, focusing primarily on insights provided by recent studies exploring the genome-wide distribution of this modification in mammals.

Identification of Methylation-Driven, Differentially Expressed STXBP6 as a Novel Biomarker in Lung Adenocarcinoma

DNA methylation is an essential epigenetic marker associated with the silencing of gene expression. Although various genome-wide studies revealed aberrantly methylated gene targets as molecular biomarkers for early detection, the survival rate of lung cancer patients is still poor. In order to identify methylation-driven biomarkers, genome-wide changes in DNA methylation and differential expression in 32 pairs of lung adenocarcinoma and adjacent normal lung tissue in non-smoking women were examined. This concurrent analysis identified 21 negatively correlated probes (r ≤ −0.5), corresponding to 17 genes. Examining the endogenous expression in lung cancer cell lines, five of the genes were found to be significantly down-regulated. Furthermore, in tumor cells alone, 5-aza-2′-deoxycytidine treatment increased the expression levels of STXBP6 in a dose dependent manner and pyrosequencing showed higher percentage of methylation in STXBP6 promoter. Functional analysis revealed that overexpressed STXBP6 in A549 and H1299 cells significantly decreased cell proliferation, colony formation, and migration, and increased apoptosis. Finally, significantly lower survival rates (P < 0.05) were observed when expression levels of STXBP6 were low. Our results provide a basis for the genetic etiology of lung adenocarcinoma by demonstrating the possible role of hypermethylation of STXBP6 in poor clinical outcomes in lung cancer patients.

The Genomic Impact of DNA CpG Methylation on Gene Expression; Relationships in Prostate Cancer

The process of DNA CpG methylation has been extensively investigated for over 50 years and revealed associations between changing methylation status of CpG islands and gene expression. As a result, DNA CpG methylation is implicated in the control of gene expression in developmental and homeostasis processes, as well as being a cancer-driver mechanism. The development of genome-wide technologies and sophisticated statistical analytical approaches has ushered in an era of widespread analyses, for example in the cancer arena, of the relationships between altered DNA CpG methylation, gene expression, and tumor status. The remarkable increase in the volume of such genomic data, for example, through investigators from the Cancer Genome Atlas (TCGA), has allowed dissection of the relationships between DNA CpG methylation density and distribution, gene expression, and tumor outcome. In this manner, it is now possible to test that the genome-wide correlations are measurable between changes in DNA CpG methylation and gene expression. Perhaps surprisingly is that these associations can only be detected for hundreds, but not thousands, of genes, and the direction of the correlations are both positive and negative. This, perhaps, suggests that CpG methylation events in cancer systems can act as disease drivers but the effects are possibly more restricted than suspected. Additionally, the positive and negative correlations suggest direct and indirect events and an incomplete understanding. Within the prostate cancer TCGA cohort, we examined the relationships between expression of genes that control DNA methylation, known targets of DNA methylation and tumor status. This revealed that genes that control the synthesis of S-adenosyl-l-methionine (SAM) associate with altered expression of DNA methylation targets in a subset of aggressive tumors.

Role of the HTLV-1 viral factors in the induction of apoptosis

Adult T-cell leukemia (ATL) and HTLV-1-associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP) are the two main diseases that are caused by the HTLV-1 virus. One of the features of HTLV-1 infection is its resistance against programmed cell death, which maintains the survival of cells to oncogenic transformation and underlies the viruses' therapeutic resistance. Two main genes by which the virus develops cancer are Tax and HBZ; playing an essential role in angiogenesis in regulating viral transcription and modulating multiple host factors as well as apoptosis pathways. Here we have reviewed by prior research how the apoptosis pathways are suppressed by the Tax and HBZ and new drugs which have been designed to deal with this suppression.

'Omics Approaches in Breast Cancer Research and Clinical Practice

Our understanding of the natural history of breast cancer has evolved alongside technologies to study its genomic, transcriptomic, proteomic, and metabolomics landscapes. These technologies have helped decipher multiple molecular pathways dysregulated in breast cancer. First-generation 'omics analyses considered each of these dimensions individually, but it is becoming increasingly clear that more holistic, integrative approaches are required to fully understand complex biological systems. The 'omics represent an exciting era of discovery in breast cancer research, although important issues need to be addressed to realize the clinical utility of these data through precision cancer care. How can the data be applied to predict response to molecular-targeted therapies? When should treatment decisions be based on tumor genetics rather than histology? And with the sudden explosion of "big data" from large 'omics consortia and new precision clinical trials, how do we now negotiate evidence-based pathways to clinical translation through this apparent sea of opportunity? The aim of this review is to provide a broad overview of 'omics technologies used in breast cancer research today, the current state-of-play in terms of applying this new knowledge in the clinic, and the practical and ethical issues that will be central to the public discussion on the future of precision cancer care.