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Objective Disease-associated, differentially hypermethylated regions have been reported in rheumatoid arthritis (RA), but no DNA methyltransferase inhibitors have been evaluated in either RA or any animal models of RA. The present study was conducted to evaluate the therapeutic potential of 5'-azacytidine (5'-azaC), a DNA methyltransferase inhibitor, and explore the cellular and gene regulatory networks involved in the context of autoimmune arthritis. Methods A disease-associated genome-wide DNA methylation profile was explored by methylated CpG island recovery assay-chromatin immunoprecipitation (ChIP) in arthritic B cells. Mice with proteoglycan-induced arthritis (PGIA) were treated with 5'-azaC. The effect of 5'-azaC on the pathogenesis of PGIA was explored by measuring serum IgM and IgG1 antibody levels using enzyme-linked immunosorbent assay, investigating the efficiency of class-switch recombination (CSR) and Aicda gene expression using real-time quantitative polymerase chain reaction, monitoring germinal center (GC) formation by immunohistochemistry, and determining alterations in B cell subpopulations by flow cytometry. The 5'-azaC-induced regulation of the Aicda gene was explored using RNA interference, ChIP, and luciferase assays. Results We explored arthritis-associated hypermethylated regions in mouse B cells and demonstrated that DNA demethylation had a beneficial effect on autoimmune arthritis. The 5'-azaC-mediated demethylation of the epigenetically inactivated Ahr gene resulted in suppressed expression of the Aicda gene, reduced CSR, and compromised GC formation. Ultimately, this process led to diminished IgG1 antibody production and amelioration of autoimmune arthritis in mice. Conclusion DNA hypermethylation plays a leading role in the pathogenesis of autoimmune arthritis and its targeted inhibition has therapeutic potential in arthritis management.

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease hallmarked by progressive and irreversible joint destruction. RA pathogenesis is a T cell-regulated and B cell-mediated process in which activated lymphocyte-produced chemokines and cytokines promote leukocyte infiltration that ultimately leads to destruction of the joints. There is an obvious need to discover new drugs for RA treatment that have different biological targets or modes of action than the currently employed therapeutics. Environmental factors such as cigarette smoke, certain diet components, and oral pathogens can significantly affect gene regulation via epigenetic factors. Epigenetics opened a new field for pharmacology, and DNA methylation and histone modification-implicated factors are feasible targets for RA therapy. Exploring RA pathogenesis involved epigenetic factors and mechanisms is crucial for developing more efficient RA therapies. Here we review epigenetic alterations associated with RA pathogenesis including DNA methylation and interacting factors. Additionally, we will summarize the literature revealing the involved molecular structures and interactions. Finally, potential epigenetic factor-based therapies will be discussed that may help in better management of RA in the future.

Although dilated cardiomyopathy (DCM) is often caused by viral infections, it frequently involves autoimmune mechanisms associated with particular HLA-DR and DQ alleles. Our homozygous HLA-DQ8Ab(0) transgenic mice in the BALB/c background (HLA-DQ8(BALB/c)-Tg) developed early and progressive fatal heart failure from 4 to 5 weeks of age. Clinical signs of the disease included cyanotic eyes, tachycardia with dyspnea (from pale to cyanotic limbs), and terminal whole body edema. Sick mice had extremely dilated hearts, enlarged liver and spleen, and pleural/peritoneal effusion. Histology of the heart showed extensive heart muscle destruction with signs of fibrosis. The autoimmune nature of the disease was shown by high titers of antimyosin antibodies in the sera and IgG deposits in sick heart muscles, as well as focal neutrophil, T cell, and macrophage infiltration of the heart muscle. The sera of the sick mice showed a granular staining pattern on sections of healthy heart muscle. Quantitative analyses of DCM-specific gene expression studies revealed that sets of genes are involved in inflammation, hypoxia, and fibrosis. Treatment with FTY720 (Fingolimod/Gilenya) protected animals from the development of cardiomyopathy. HLA-DQ8(BALB/c)-Tg mice represent a spontaneous autoimmune myocarditis model that may provide a useful tool for studying the autoimmune mechanism of DCM and testing immunosuppressive drugs.

Rheumatoid arthritis (RA) is one of the most common autoimmune disorders characterized by the chronic and progressive inflammation of various organs, most notably the synovia of joints leading to joint destruction, a shorter life expectancy, and reduced quality of life. Although we have substantial information about the pathophysiology of the disease with various groups of immune cells and soluble mediators identified to participate in the pathogenesis, several aspects of the altered immune functions and regulation in RA remain controversial. Animal models are especially useful in such scenarios. Recently research focused on IL-17 and IL-17 producing cells in various inflammatory diseases such as in RA and in different rodent models of RA. These studies provided occasionally contradictory results with IL-17 being more prominent in some of the models than in others; the findings of such experimental setups were sometimes inconclusive compared to the human data. The aim of this review is to summarize briefly the recent advancements on the role of IL-17, particularly in the different rodent models of RA.

Objective The regulatory role of capsaicin-sensitive peptidergic sensory nerves has been shown in acute inflammation, but little is known about their involvement in T/B-cell driven autoimmune arthritis. This study integratively characterized the function of these nerve endings in the proteoglycan-induced chronic arthritis (PGIA), a translational model of rheumatoid arthritis. Methods Peptidergic afferents were defunctionalized by resiniferatoxin (RTX) pretreatment in BALB/c mice, PGIA was induced by repeated antigen challenges. Hind paw volume, arthritis severity, grasping ability and the mechanonociceptive threshold were monitored during the 17-week experiment. Myeloperoxidase activity, vascular leakage and bone turnover were evaluated by in vivo optical imaging. Bone morphology was assessed using micro-CT, the intertarsal small joints were processed for histopathological analysis. Results Following desensitization of the capsaicin-sensitive afferents, ankle edema, arthritis severity and mechanical hyperalgesia were markedly diminished. Myeloperoxidase activity was lower in the early, but increased in the late phase, whilst plasma leakage and bone turnover were not altered. Desensitized mice displayed similar bone spurs and erosions, but increased trabecular thickness of the tibia and bony ankylosis of the spine. Intertarsal cartilage thickness was not altered in the model, but desensitization increased this parameter in both the non-arthritic and arthritic groups. Conclusion This is the first integrative in vivo functional and morphological characterization of the PGIA mouse model, wherein peptidergic afferents have an important regulatory function. Their overall effect is proinflammatory by increasing acute inflammation, immune cell activity and pain. Meanwhile, their activation decreases spinal ankylosis, arthritis-induced altered trabecularity, and cartilage thickness in small joints. Electronic supplementary material The online version of this article (10.1186/s12974-018-1364-5) contains supplementary material, which is available to authorized users.

Objective To identify epigenetic factors that are implicated in the pathogenesis of rheumatoid arthritis (RA), and to explore the therapeutic potential of the targeted inhibition of these factors. Methods Polymerase chain reaction (PCR) arrays were used to investigate the expression profile of genes that encode key epigenetic regulator enzymes. Mononuclear cells from RA patients and mice were monitored for gene expression changes, in association with arthritis development in murine models of RA. Selected genes were further characterized by quantitative reverse transcription–PCR, Western blot, and flow cytometry methods. The targeted inhibition of the up-regulated enzymes was studied in arthritic mice. Results A set of genes with arthritis-specific expression was identified by the PCR arrays. Aurora kinases A and B, both of which were highly expressed in arthritic mice and treatment-naive RA patients, were selected for detailed analysis. Elevated aurora kinase expression was accompanied by increased phosphorylation of histone H3, which promotes proliferation of T lymphocytes. Treatment with VX-680, a pan–aurora kinase inhibitor, promoted B cell apoptosis, provided significant protection against disease onset, and attenuated inflammatory reactions in arthritic mice. Conclusion Arthritis development is accompanied by changes in expression of a number of epigenome-modifying enzymes. Drug-induced down-regulation of the aurora kinases, among other targets, seems to be sufficient to treat experimental arthritis. Development of new therapeutics that target aurora kinases can potentially improve RA management.

Background Rheumatoid arthritis (RA) is an autoimmune disease of the synovial joints. The autoimmune character of RA is underscored by prominent production of autoantibodies such as those against IgG (rheumatoid factor), and a broad array of joint tissue-specific and other endogenous citrullinated proteins. Anti-citrullinated protein antibodies (ACPA) can be detected in the sera and synovial fluids of RA patients and ACPA seropositivity is one of the diagnostic criteria of RA. Studies have demonstrated that RA T cells respond to citrullinated peptides (epitopes) of proteoglycan (PG) aggrecan, which is one of the most abundant macromolecules of articular cartilage. However, it is not known if the PG molecule is citrullinated in vivo in human cartilage, and if so, whether citrulline-containing neoepitopes of PG (CitPG) can contribute to autoimmunity in RA. Methods CitPG was detected in human cartilage extracts using ACPA+ RA sera in dot blot and Western blot. Citrullination status of in vitro citrullinated recombinant G1 domain of human PG (rhG1) was confirmed by antibody-based and chemical methods, and potential sites of citrullination in rhG1 were explored by molecular modeling. CitPG-specific serum autoantibodies were quantified by enzyme-linked immunosorbent assays, and CitPG was localized in osteoarthritic (OA) and RA cartilage using immunohistochemistry. Findings Sera from ACPA+ RA patients reacted with PG purified from normal human cartilage specimens. PG fragments (mainly those containing the G1 domain) from OA or RA cartilage extracts were recognized by ACPA+ sera but not by serum from ACPA- individuals. ACPA+ sera also reacted with in vitro citrullinated rhG1 and G3 domain-containing fragment(s) of PG. Molecular modeling suggested multiple sites of potential citrullination within the G1 domain. The immunohistochemical localization of CitPG was different in OA and RA cartilage. Conclusions CitPG is a new member of citrullinated proteins identified in human joints. CitPG could be found in both normal and diseased cartilage specimens. Antibodies against CitPG may trigger or augment arthritis by forming immune complexes with this autoantigen in the joints of ACPA+ RA patients.

Proteoglycan (PG)-induced arthritis (PGIA) is a murine model of rheumatoid arthritis. Arthritis-prone BALB/c mice are 100% susceptible, whereas the major histocompatibility complex-matched DBA/2 strain is completely resistant to PGIA. To reduce the size of the disease-suppressive loci for sequencing and to find causative genes of arthritis, we created a set of BALB/c.DBA/ 2-congenic/subcongenic strains carrying DBA/2 genomic intervals overlapping the entire Pgia26 locus on chromosome 3 (chr3) and Pgia23/Pgia12 loci on chr19 in the arthritis-susceptible BALB/c background. Upon immunization of these subcongenic strains and their wild-type (BALB/c) littermates, we identified a major Pgia26a sublocus on chr3 that suppressed disease onset, incidence and severity via controlling the complex trait of T-cell responses. The region was reduced to 3 Mbp (11.8 Mbp with flanking regions) in size and contained gene(s) influencing the production of a number of proinflammatory cytokines. Additionally, two independent loci (Pgia26b and Pgia26c) suppressed the clinical scores of arthritis. The Pgia23 locus (~3 Mbp in size) on chr19 reduced arthritis susceptibility and onset, and the Pgia12 locus (6 Mbp) associated with low arthritis severity. Thus, we have reached the critical sizes of arthritis-associated genomic loci on mouse chr3 and chr19, which are ready for high-throughput sequencing of genomic DNA.

Summary Objective To study temporomandibular joint (TMJ) involvement in an autoimmune murine model of rheumatoid arthritis (RA), a disease characterized by inflammatory destruction of the synovial joints. Although TMJ dysfunction is frequently found in RA, TMJ involvement in RA remains unclear, and TMJ pathology has not been studied in systemic autoimmune animal models of RA. Methods Proteoglycan (PG) aggrecan-induced arthritis (PGIA) was generated in genetically susceptible BALB/c mice. TMJs and joint tissues/cartilage were harvested for histological and immunohistochemical analyses and RNA isolation for quantitative polymerase chain-reaction. Serum cytokine levels were measured in mice with acute or chronic arthritis, and in non-arthritic control animals. Results Despite the development of destructive synovitis in the limbs, little or no synovial inflammation was found in the TMJs of mice with PGIA. However, the TMJs of arthritic mice showed evidence of aggrecanase- and matrix metalloproteinase-mediated loss of glycosaminoglycan-containing aggrecan, and in the most severe cases, structural damage of cartilage. Serum levels of pro-inflammatory cytokines, including interleukin (IL)-1β, were elevated in arthritic animals. Expression of the IL-1β gene was also high in the inflamed limbs, but essentially normal in the TMJs. Local expression of genes encoding matrix-degrading enzymes (aggrecanases and stromelysin) was upregulated to a similar degree in both the limbs and the TMJs. Conclusion We propose that constantly elevated levels of catabolic cytokines, such as IL-1β, in the circulation (released from inflamed joints) create a pro-inflammatory milieu within the TMJ, causing local upregulation of proteolytic enzymes and subsequent loss of aggrecan from cartilage.

Autism is currently considered a multigene disorder with epigenetic influences. To investigate the contribution of DNA methylation to autism spectrum disorders, we have recently completed large-scale methylation profiling by CpG island microarray analysis of lymphoblastoid cell lines derived from monozygotic twins discordant for diagnosis of autism and their nonautistic siblings. Methylation profiling revealed many candidate genes differentially methylated between discordant MZ twins as well as between both twins and nonautistic siblings. Bioinformatics analysis of the differentially methylated genes demonstrated enrichment for high-level functions including gene transcription, nervous system development, cell death/survival, and other biological processes implicated in autism. The methylation status of 2 of these candidate genes, BCL-2 and retinoic acid-related orphan receptor alpha (RORA), was further confirmed by bisulfite sequencing and methylation-specific PCR, respectively. Immunohistochemical analyses of tissue arrays containing slices of the cerebellum and frontal cortex of autistic and age- and sex-matched control subjects revealed decreased expression of RORA and BCL-2 proteins in the autistic brain. Our data thus confirm the role of epigenetic regulation of gene expression via differential DNA methylation in idiopathic autism, and furthermore link molecular changes in a peripheral cell model with brain pathobiology in autism.—Nguyen, A., Rauch, T. A., Pfeifer, G. P., Hu, V. W. Global methylation profiling of lymphoblastoid cell lines reveals epigenetic contributions to autism spectrum disorders and a novel autism candidate gene, RORA, whose protein product is reduced in autistic brain.

Background Myeloid-derived suppressor cells (MDSCs) are innate immune cells capable of suppressing T-cell responses. We previously reported the presence of MDSCs with a granulocytic phenotype in the synovial fluid (SF) of mice with proteoglycan (PG)-induced arthritis (PGIA), a T cell-dependent autoimmune model of rheumatoid arthritis (RA). However, the limited amount of SF-MDSCs precluded investigations into their therapeutic potential. The goals of this study were to develop an in vitro method for generating MDSCs similar to those found in SF and to reveal the therapeutic effect of such cells in PGIA. Methods Murine bone marrow (BM) cells were cultured for 3 days in the presence of granulocyte macrophage colony-stimulating factor (GM-CSF), interleukin-6 (IL-6), and granulocyte colony-stimulating factor (G-CSF). The phenotype of cultured cells was analyzed using flow cytometry, microscopy, and biochemical methods. The suppressor activity of BM-MDSCs was tested upon co-culture with activated T cells. To investigate the therapeutic potential of BM-MDSCs, the cells were injected into SCID mice at the early stage of adoptively transferred PGIA, and their effects on the clinical course of arthritis and PG-specific immune responses were determined. Results BM cells cultured in the presence of GM-CSF, IL-6, and G-CSF became enriched in MDSC-like cells that showed greater phenotypic heterogeneity than MDSCs present in SF. BM-MDSCs profoundly inhibited both antigen-specific and polyclonal T-cell proliferation primarily via production of nitric oxide. Injection of BM-MDSCs into mice with PGIA ameliorated arthritis and reduced PG-specific T-cell responses and serum antibody levels. Conclusions Our in vitro enrichment strategy provides a SF-like, but controlled microenvironment for converting BM myeloid precursors into MDSCs that potently suppress both T-cell responses and the progression of arthritis in a mouse model of RA. Our results also suggest that enrichment of BM in MDSCs could improve the therapeutic efficacy of BM transplantation in RA.

Alterations in DNA methylation patterns occur in every type of human cancer and are considered a hallmark of malignant transformation. Most notable is the cancer-associated hypermethylation of CpG-rich sequences, the so-called CpG islands, which are often found near the 5' ends and promoters of genes. This CpG island methylation represents a positive signal that can be used to distinguish malignant tissue from normal tissue. Thus, characterization of CpG island hypermethylation has become a valuable tool for cancer detection and diagnosis. There are several methods used for detection of gene-specific DNA methylation. However, besides looking at individual genes, an even greater potential lies in the characterization of genome-wide changes of DNA methylation patterns in tumors. The authors propose that tumor type- and tumor subtype-specific DNA methylation patterns exist and can be exploited for the classification of cancers, their response to therapy and their metastatic potential, and thus may have predictive value. Various methods for genome-wide analysis of DNA methylation have been developed. These methods are described briefly and the methylated-CpG island recovery assay will be reviewed. This assay has been used in combination with microarray analysis to map CpG island methylation across cancer genomes.

Summary T cell receptor transgenic (TCR-Tg) mice specific for the arthritogenic 5/4E8 epitope in the G1 domain of cartilage proteoglycan were generated and back-crossed into arthritis-prone BALB/c background. Although more than 90% of CD4+ T cells of all TCR-Tg lines were 5/4E8-specific, one (TCR-TgA) was highly sensitive to G1-induced or spontaneous arthritis, while another (TCR-TgB) was less susceptible. Here we studied whether fine differences in TCR signalling controlled the onset and severity of arthritis. Mice from the two TCR-Tg lines were immunized side by side with purified recombinant human G1 (rhG1) domain for G1 domain of cartilage proteoglycan (PG)-induced arthritis (GIA). TCR-TgA mice developed severe and early-onset arthritis, whereas TCR-TgB mice developed weaker arthritis with delayed onset, although TCR-TgB CD4+ T cells expressed approximately twice more TCR-Vβ4 chain protein. The more severe arthritis in TCR-TgA mice was associated with higher amounts of anti-G1 domain-specific antibodies, larger numbers of B cells and activated T helper cells. Importantly, TCR-TgB CD4+ T cells were more sensitive to in vitro activation-induced apoptosis, correlating with their higher TCR and CD3 expression and with the increased TCR signal strength. These findings indicate that TCR signal strength determines the clinical outcome of arthritis induction: ‘optimal’ TCR signal strength leads to strong T cell activation and severe arthritis in TCR-TgA mice, whereas ‘supra-optimal’ TCR signal leads to enhanced elimination of self-reactive T cells, resulting in attenuated disease.

Lung carcinomas have been the leading causes of cancer-associated death in both sexes worldwide. Epidemiological studies demonstrated that cigarette smoking and other environmental factors such as radon or asbestos can also contribute to lung cancer development. Environmental chemicals can promote cancer formation by causing lesions in genomic DNA and/or by inducing various alterations in the epigenomes of cells lining the airways. Epithelial cells whose epigenome has significantly become altered or damaged can become transformed (i.e., reprogrammed) and start to exhibit malignant properties. With the advent of the postgenomic era and its advanced methodological arsenal, genome-wide analysis tools have become available that have contributed to the identification of the involved epigenetic factors and map disease-associated epigenome profile changes. These studies proved that DNA methylation, posttranslational modification of histones, and noncoding RNAs are also involved in lung cancer development. Coordinated epigenetic and genetic studies can provide new insights into the etiology of lung carcinomas, and perhaps extend the currently used diagnostic and therapeutic arsenal for cancer patients.

The base 5-hydroxymethylcytosine (5hmC) was recently identified as an oxidation product of 5-methylcytosine in mammalian DNA. Here, using sensitive and quantitative methods to assess levels of 5-hydroxymethyl-2′-deoxycytidine (5hmdC) and 5-methyl-2′-deoxycytidine (5mdC) in genomic DNA, we investigated whether levels of 5hmC can distinguish normal tissue from tumor tissue. In squamous cell lung cancers, levels of 5hmdC were depleted substantially with up to 5-fold reduction compared with normal lung tissue. In brain tumors, 5hmdC showed an even more drastic reduction with levels up to more than 30-fold lower than in normal brain, but 5hmdC levels were independent of mutations in isocitrate dehydrogenase-1. Furthermore, immunohistochemical analysis indicated that 5hmC is remarkably depleted in many types of human cancer. Importantly, an inverse relationship between 5hmC levels and cell proliferation was observed with lack of 5hmC in proliferating cells. The data therefore suggest that 5hmdC is strongly depleted in human malignant tumors, a finding that adds another layer of complexity to the aberrant epigenome found in cancer tissue. In addition, a lack of 5hmC may become a useful biomarker for cancer diagnosis. Cancer Res; 71(24); 7360–5. ©2011 AACR.

Changes in DNA methylation patterns are an important characteristic of human cancer including lung cancer. In particular, hypermethylation of CpG islands is a signature of malignant progression. Methylated CpG islands are promising diagnostic markers for the early detection of cancer. However, the full extent and sequence context of DNA hypermethylation in lung cancer has remained unknown. We have used the methylated CpG island recovery assay and high-resolution microarray analysis to find hypermethylated CpG islands in squamous cell carcinomas (SCC) and adenocarcinomas of the lung. Each tumor contained several hundred hypermethylated CpG islands. In an initial microarray screen, 36 CpG islands were methylated in five of five (=100%) of the SCC tumors tested and 52 CpG islands were methylated in at least 75% of the adenocarcinomas tested (n=8). Using sodium-bisulfite-based approaches, 12 CpG islands (associated with the BARHL2, EVX2, IRX2, MEIS1, MSX1, NR2E1, OC2, OSR1, OTX1, PAX6, TFAP2A, and ZNF577 genes) were confirmed to be methylated in 85% to 100% of the squamous cell carcinomas and 11 CpG islands (associated with the CHAD, DLX4, GRIK2, KCNG3, NR2E1, OSR1, OTX1, OTX2, PROX1, RUNX1, and VAX1 genes) were methylated in80% of the adenocarcinomas. From the list of genes that were methylated in lung adenocarcinomas, we identified the gene FAT4 and found that this gene was methylated in 39% of the tumors. FAT4 is the closest mammalian homologue of the Drosophila tumor suppressor Fat which is an important component of the Hippo growth control pathway. Many of these newly discovered methylated CpG islands hold promise for becoming biomarkers for the early detection of lung cancer.

Astrocytomas are common and lethal human brain tumors. We have analyzed the methylation status of over 28,000 CpG islands and 18,000 promoters in normal human brain and in astrocytomas of various grades using the methylated CpG island recovery assay. We identified 6,000 to 7,000 methylated CpG islands in normal human brain. Approximately 5% of the promoter-associated CpG islands in the normal brain are methylated. Promoter CpG island methylation is inversely correlated whereas intragenic methylation is directly correlated with gene expression levels in brain tissue. In astrocytomas, several hundred CpG islands undergo specific hypermethylation relative to normal brain with 428 methylation peaks common to more than 25% of the tumors. Genes involved in brain development and neuronal differentiation, such as BMP4, POU4F3, GDNF, OTX2, NEFM, CNTN4, OTP, SIM1, FYN, EN1, CHAT, GSX2, NKX6-1, PAX6, RAX, and DLX2, were strongly enriched among genes frequently methylated in tumors. There was an overrepresentation of homeobox genes and 31% of the most commonly methylated genes represent targets of the Polycomb complex. We identified several chromosomal loci in which many (sometimes more than 20) consecutive CpG islands were hypermethylated in tumors. Seven such loci were near homeobox genes, including the HOXC and HOXD clusters, and the BARHL2, DLX1, and PITX2 genes. Two other clusters of hypermethylated islands were at sequences of recent gene duplication events. Our analysis offers mechanistic insights into brain neoplasia suggesting that methylation of the genes involved in neuronal differentiation, in cooperation with other oncogenic events, may shift the balance from regulated differentiation towards gliomagenesis. Cancer Res; 70(7); 2718–27

Background Genetic as well as epigenetic alterations are a hallmark of both epithelial and haematological malignancies. High throughput screens are required to identify epigenetic markers that can be useful for diagnostic and prognostic purposes across malignancies. Results Here we report for the first time the use of the MIRA assay (methylated CpG island recovery assay) in combination with genome-wide CpG island arrays to identify epigenetic molecular markers in childhood acute lymphoblastic leukemia (ALL) on a genome-wide scale. We identified 30 genes demonstrating methylation frequencies of ≥25% in childhood ALL, nine genes showed significantly different methylation frequencies in B vs T-ALL. For majority of the genes expression could be restored in methylated leukemia lines after treatment with 5-azaDC. Forty-four percent of the genes represent targets of the polycomb complex. In chronic myeloid leukemia (CML) two of the genes, (TFAP2A and EBF2), demonstrated increased methylation in blast crisis compared to chronic phase (P < 0.05). Furthermore hypermethylation of an autophagy related gene ATG16L2 was associated with poorer prognosis in terms of molecular response to Imatinib treatment. Lastly we demonstrated that ten of these genes were also frequently methylated in common epithelial cancers. Conclusion In summary we have identified a large number of genes showing frequent methylation in childhood ALL, methylation status of two of these genes is associated with advanced disease in CML and methylation status of another gene is associated with prognosis. In addition a subset of these genes may act as epigenetic markers across hematological malignancies as well as common epithelial cancers.

An increasing number of studies show that besides the inherited genetic architecture (that is, genomic DNA), various environmental factors significantly contribute to the etiology of rheumatoid arthritis. Epigenetic factors react to external stimuli and form bridges between the environment and the genetic information-harboring DNA. Epigenetic mechanisms are implicated in the final interpretation of the encoded genetic information by regulating gene expression, and alterations in their profile influence the activity of the immune system. Overall, epigenetic mechanisms further increase the well-known complexity of rheumatoid arthritis by providing additional subtle contributions to rheumatoid arthritis susceptibility. Although there are controversies regarding the involvement of epigenetic and genetic factors in rheumatoid arthritis etiology, it is becoming obvious that the two systems (genetic and epigenetic) interact with each other and are ultimately responsible for rheumatoid arthritis development. Here, epigenetic factors and mechanisms involved in rheumatoid arthritis are reviewed and new, potential therapeutic targets are discussed.