Aberrant DNA hypermethylation signature in acute myeloid leukemia directed by EVI1

Predictive genomic biomarkers of therapeutic effects in renal cell carcinoma

BACKGROUND

In recent years, there have been great improvements in the therapy of renal cell carcinoma. Nevertheless, the therapeutic effect varies significantly from person to person. To discern the effective treatment for different populations, predictive molecular biomarkers in response to target, immunological, and combined therapies are widely studied.

CONCLUSION

This review summarized those studies from three perspectives (SNPs, mutation, and expression level) and listed the relationship between biomarkers and therapeutic effect, highlighting the great potential of predictive molecular biomarkers in metastatic RCC therapy. However, due to a series of reasons, most of these findings require further validation.

EVI1-mediated Programming of Normal and Malignant Hematopoiesis

Ecotropic viral integration site 1 (EVI1), encoded at the MECOM locus, is an oncogenic zinc finger transcription factor with diverse roles in normal and malignant cells, most extensively studied in the context of hematopoiesis. EVI1 interacts with other transcription factors in a context-dependent manner and regulates transcription and chromatin remodeling, thereby influencing the proliferation, differentiation, and survival of cells. Interestingly, it can act both as a transcriptional activator as well as a transcriptional repressor. EVI1 is expressed, and fulfills important functions, during the development of different tissues, including the nervous system and hematopoiesis, demonstrating a rigid spatial and temporal expression pattern. However, EVI1 is regularly overexpressed in a variety of cancer entities, including epithelial cancers such as ovarian and pancreatic cancer, as well as in hematologic malignancies like myeloid leukemias. Importantly, EVI1 overexpression is generally associated with a very poor clinical outcome and therapy-resistance. Thus, EVI1 is an interesting candidate to study to improve the prognosis and treatment of high-risk patients with "EVI1high" hematopoietic malignancies.

Characteristics and clinical outcomes of patients with acute myeloid leukemia with inv(3)(q21q26.2) or t(3;3)(q21;q26.2)

Acute myeloid leukemia (AML) with inv(3)(q21q26.2)/t(3;3)(q21;q26.2) has a very poor prognosis. Determinants of clinical outcomes and optimal treatment remain uncertain. We retrospectively reviewed 108 cases of AML with inv(3)/t(3;3) and evaluated clinicopathological characteristics and clinical outcomes: 53 newly diagnosed (ND) AML and 55 relapsed/refractory (R/R) AML. Median age was 55 years. White blood cell (WBC) count ≥20x109/L and platelet count ≥140x109/L was observed in 25% and 32% of ND patients, respectively. Anomalies involving chromosome 7 were identified in 56% of patients. The most frequently mutated genes were SF3B1, PTPN11, NRAS, KRAS and ASXL1. In ND patients, the composite complete remission (CRc) rate was 46% overall; 46% with high-intensity treatments and 47% with lowintensity treatments. The 30-day mortality was 14% and 0%, with high- and low-intensity treatment, respectively. In R/R patients, the CRc rate was 14%. Venetoclax based-regimens were associated with a CRc rate of 33%. The 3-year overall survival (OS) was 8.8% and 7.1% in ND and R/R patients, respectively. The 3-year cumulative incidence of relapse was 81.7% overall. Older age, high WBC, high peripheral blast count, secondary AML and KRAS, ASXL1, DNMT3A mutations were associated with worse OS in univariable analyses. The 5-year OS rates were 44% and 6% with or without hematopoietic stem cell transplantation in CR1, respectively. AML with inv(3)/t(3;3) is associated with low CR rates, very high risk of relapse and dismal long-term survival. Intensive chemotherapy and hy pomethylating agents provide similar rates of remission and patients achieving CR benefit from hematopoietic stem cell transplantation in first CR.

Ectopic viral integration Site-1 oncogene promotes NRAS pathway through epigenetic silencing of microRNA-124 in acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) is an aggressive hematological malignancy characterized by genetic mutations that promote proliferation of myeloid progenitors and prevent their differentiation. Over-expression of Ectopic Viral Integration site-1(EVI-1) is related to the poor prognosis in myeloid leukemia, but the underlying mechanism remains unclear.

METHODS

Using qRT-PCR and western blotting, we quantified expressions of EVI-1, NRAS and ERK/p-ERK in leukemia cell lines and PBMCs. Using WTS-8 and cell cycle analysis, we further investigated whether downregulation of EVI-1 by siRNA can inhibit cell proliferation. Microscopic observation of peripheral blood cells from EVI-1 transgenic zebrafish and WT control were analyzed by Wright Giemsa staining. Using miR-seq, qPCR, dual-luciferase reporter and coimmunoprecipitation assays, we revealed the relationship between EVI-1, miR-124 and NRAS.

RESULTS

EVI-1 was highly expressed in both primary AML and leukemia cell lines (THP-1 and K562). In a transgenic zebrafish model, EVI-1 mediated higher mortality and induced immature hematopoietic cells in the blood circulation, suggesting its oncogenic role. Furthermore, our results suggested that EVI-1 upregulated NRAS expression, thereby activating the RAS/ERK pathway through epigenetic silencing of a potent NRAS suppressor, miR-124. In this study, we found that EVI1 physically interacts with Dnmt3a to form a protein complex that targets and binds to regulatory elements of miR-124.

CONCLUSIONS

Overall, the current findings demonstrate that EVI-1 overexpression converges on the regulation of miR-124 promoter methylation and activation of the RAS/ERK pathway in AML carcinogenesis, and suggest EVI-1 and/or miR-124 as therapeutic targets for this dismal disease.

EVI1 protein interaction dynamics: targetable for therapeutic intervention?

High expression of the transcriptional regulator EVI1 encoded at the MECOM locus at 3q26 is one of the most aggressive oncogenic drivers in acute myeloid leukaemia (AML) and carries a very poor prognosis. How EVI1 confers leukaemic transformation and chemotherapy resistance in AML is subject to important ongoing clinical and experimental studies. Recent discoveries have revealed critical details about genetic mechanisms of the activation of EVI1 overexpression and downstream events of aberrantly high EVI1 expression. Here we review and discuss aspects concerning the protein interactions of EVI1 and the related proteins MDS-EVI1 and ΔEVI1 from the perspective of their potential for therapeutic intervention.

EVI1 promotes metastasis by downregulating TIMP2 in metastatic colon and breast cancer cells

Ecotropic viral integration site-1 (EVI1) is an oncogenic zinc finger transcription factor whose expression is frequently upregulated in a variety of cancers, including both myeloid malignancies and solid tumors. Previously, our group has shown that EVI1 knockdown minimizes the metastatic potential of colon cancer cells compared to that of control cells. In this study, to identify the potential targets that regulate cancer metastasis, control and EVI1 knockdown colon cancer cells were subjected to microarray. Differential gene expression analysis revealed significant downregulation of tissue inhibitor of matrix metalloproteinase-2 (TIMP2) in EVI1 expressing cells. EVI1 knockdown increased TIMP2 protein expression levels and reduced wound healing and migration capacity in metastatic cells. Mechanistically, the TIMP2 promoter harbors potential binding sites for EVI1; EVI1 binds to TIMP2 promoter and represses its expression, as observed using ChIP and luciferase assay, respectively. TIMP2 is an important metastasis suppressor gene; however, its function is suppressed in many cancers through hypermethylation. Thus, demethylation could prove to be a potential alternative to reactivate TIMP2 functional activity. Immunoprecipitation analysis showed that DNA-methyltransferase 1 (DNMT1), which plays a vital role in maintaining the genome methylation pattern during DNA replication and repair, interacts with EVI1 to promote TIMP2 silencing. Treating cancer cells in vitro with a known demethylation agent, 5-aza-2'-deoxycytidine (Aza-D), restored the optimal TIMP2 expression without altering EVI1 binding efficiency and reduced relative wound healing potential of cancer cells. Animal studies showed that Aza-D treated cells injected through the intravenous route exhibited reduced liver and skin metastasis when compared to non-treated cells. Furthermore, Aza-D treatment in mice delayed the metastasis progression compared to the vehicle treated group. Thus, the present study provides an insight into the therapeutic applications of demethylating agents to reduce cancer metastasis in models with EVI1 overexpressing tumors.

Silylation of Deoxynucleotide Analog Yields an Orally Available Drug with Antileukemia Effects

DNA methyltransferase inhibitors have improved the prognosis of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). However, because these agents are easily degraded by cytidine deaminase (CDA), they must be administered intravenously or subcutaneously. Recently, two orally bioavailable DNA methyltransferase inhibitors, CC-486 and ASTX727, were approved. In previous work, we developed 5-O-trialkylsilylated decitabines that resist degradation by CDA. However, the effects of silylation of a deoxynucleotide analog and enzymatic cleavage of silylation have not been fully elucidated. Enteric administration of OR21 in a cynomolgus monkey model led to high plasma concentrations and hypomethylation, and in a mouse model, oral administration of enteric-coated OR21 led to high plasma concentrations. The drug became biologically active after release of decitabine (DAC) from OR21 following removal of the 5'-O-trisilylate substituent. Toxicities were tolerable and lower than those of DAC. Transcriptome and methylome analysis of MDS and AML cell lines revealed that OR21 increased expression of genes associated with tumor suppression, cell differentiation, and immune system processes by altering regional promoter methylation, indicating that these pathways play pivotal roles in the action of hypomethylating agents. OR21 induced cell differentiation via upregulation of the late cell differentiation drivers CEBPE and GATA-1 Thus, silylation of a deoxynucleotide analog can confer oral bioavailability without new toxicities. Both in vivo and in vitro, OR21 exerted antileukemia effects, and had a better safety profile than DAC. Together, our findings indicate that OR21 is a promising candidate drug for phase I study as an alternative to azacitidine or decitabine.

EVI1 dysregulation: impact on biology and therapy of myeloid malignancies

Ecotropic viral integration site 1 (Evi1) was discovered in 1988 as a common site of ecotropic viral integration resulting in myeloid malignancies in mice. EVI1 is an oncogenic zinc-finger transcription factor whose overexpression contributes to disease progression and an aggressive phenotype, correlating with poor clinical outcome in myeloid malignancies. Despite progress in understanding the biology of EVI1 dysregulation, significant improvements in therapeutic outcome remain elusive. Here, we highlight advances in understanding EVI1 biology and discuss how this new knowledge informs development of novel therapeutic interventions. EVI1 is overexpression is correlated with poor outcome in some epithelial cancers. However, the focus of this review is the genetic lesions, biology, and current therapeutics of myeloid malignancies overexpressing EVI1.

Epigenetic Mechanisms in Leukemias and Lymphomas

Although we are just beginning to understand the mechanisms that regulate the epigenome, aberrant epigenetic programming has already emerged as a hallmark of hematologic malignancies including acute myeloid leukemia (AML) and B-cell lymphomas. Although these diseases arise from the hematopoietic system, the epigenetic mechanisms that drive these malignancies are quite different. Yet, in all of these tumors, somatic mutations in transcription factors and epigenetic modifiers are the most commonly mutated set of genes and result in multilayered disruption of the epigenome. Myeloid and lymphoid neoplasms generally manifest epigenetic allele diversity, which contributes to tumor cell population fitness regardless of the underlying genetics. Epigenetic therapies are emerging as one of the most promising new approaches for these patients. However, effective targeting of the epigenome must consider the need to restore the various layers of epigenetic marks, appropriate biological end points, and specificity of therapeutic agents to truly realize the potential of this modality.

EVI1 phosphorylation at S436 regulates interactions with CtBP1 and DNMT3A and promotes self-renewal

The transcriptional regulator EVI1 has an essential role in early development and haematopoiesis. However, acute myeloid leukaemia (AML) driven by aberrantly high EVI1 expression has very poor prognosis. To investigate the effects of post-translational modifications on EVI1 function, we carried out a mass spectrometry (MS) analysis of EVI1 in AML and detected dynamic phosphorylation at serine 436 (S436). Wild-type EVI1 (EVI1-WT) with S436 available for phosphorylation, but not non-phosphorylatable EVI1-S436A, conferred haematopoietic progenitor cell self-renewal and was associated with significantly higher organised transcriptional patterns. In silico modelling of EVI1-S436 phosphorylation showed reduced affinity to CtBP1, and CtBP1 showed reduced interaction with EVI1-WT compared with EVI1-S436A. The motif harbouring S436 is a target of CDK2 and CDK3 kinases, which interacted with EVI1-WT. The methyltransferase DNMT3A bound preferentially to EVI1-WT compared with EVI1-S436A, and a hypomethylated cell population associated by EVI1-WT expression in murine haematopoietic progenitors is not maintained with EVI1-S436A. These data point to EVI1-S436 phosphorylation directing functional protein interactions for haematopoietic self-renewal. Targeting EVI1-S436 phosphorylation may be of therapeutic benefit when treating EVI1-driven leukaemia.

Efficacy of All-Trans-Retinoic Acid in High-Risk Acute Myeloid Leukemia with Overexpression of EVI1

Introduction

EVI1 (MECOM)-positive acute myeloid leukemia (AML) cells have shown in vitro sensitivity to all-trans-retinoic acid (ATRA) by inducing differentiation, cell death, and decreased leukemic engraftment.

Methods

In this pilot study, we investigated the response to ATRA in 13 high-risk AML patients with overexpression of EVI1.

Results

Seven of the 13 patients (53.8%) achieved complete remission (CR), and response can be combined with a decreased of the leukemia stem cell pool.

Conclusion

These primary results tend to confirm in vitro results and suggest that addition of ATRA might be of benefit in the treatment of patients with EVI1-positive AML.

De novo methyltransferases: Potential players in diseases and new directions for targeted therapy

Epigenetic modifications govern gene expression by guiding the human genome on 'what to express and what not to'. DNA methyltransferases (DNMTs) establish methylation patterns on DNA, particularly in CpG islands, and such patterns play a major role in gene silencing. DNMTs are a family of proteins/enzymes (DNMT1, 2, 3A, 3B, and 3L), among which, DNMT1 (maintenance methyltransferase) and DNMT3 (de novo methyltransferases) that direct mammalian development and genome imprinting are highly investigated. In recent decades, many studies revealed a strong association of DNA methylation patterns with gene expression in various clinical conditions. Differential expression of DNMT3 family proteins and their splice variants result in changes in methylation patterns and such alterations have been associated with the initiation and progression of various diseases, especially cancer. This review will discuss the aberrant modifications generated by DNMT3 proteins under various clinical conditions, suggesting a potential signature for de novo methyltransferases in targeted disease therapy. Further, this review discusses the possibility of using 'CpG island methylation signatures' as promising biomarkers and emphasizes 'targeted hypomethylation' by disrupting the interaction of specific DNMT-protein complexes as the future of cancer therapeutics.

EVI1 as a Prognostic and Predictive Biomarker of Clear Cell Renal Cell Carcinoma

The transcription factor EVI1 plays an oncogenic role in several types of neoplasms by promoting aggressive cancer features. EVI1 contributes to epigenetic regulation and transcriptional control, and its overexpression has been associated with enhanced PI3K-AKT-mTOR signaling in some settings. These observations raise the possibility that EVI1 influences the prognosis and everolimus-based therapy outcome of clear cell renal cell carcinoma (ccRCC). Here, gene expression and protein immunohistochemical studies of ccRCC show that EVI1 overexpression is associated with advanced disease features and with poorer outcome-particularly in the CC-e.3 subtype defined by The Cancer Genome Atlas. Overexpression of an oncogenic EVI1 isoform in RCC cell lines confers substantial resistance to everolimus. The EVI1 rs1344555 genetic variant is associated with poorer survival and greater progression of metastatic ccRCC patients treated with everolimus. This study leads us to propose that evaluation of EVI1 protein or gene expression, and of EVI1 genetic variants may help improve estimates of prognosis and the benefit of everolimus-based therapy in ccRCC.

Downregulation of EVI1 Expression Inhibits Cell Proliferation and Induces Apoptosis in Hilar Cholangiocarcinoma via the PTEN/AKT Signalling Pathway

Aims: Hilar cholangiocarcinoma (HCCA) is a tumour with high malignancy, low surgical resection potential, and a poor prognosis. Ecotropic Viral Integration site 1 (EVI1) is a transcriptional regulator that has been proven to be associated with tumourigenesis and progression in many human solid tumours. However, the expression of EVI1 and its role in HCCA progression remain unclear. The aim of this study was to clarify the association between EVI1 expression and clinical outcomes in patients with HCCA.

Methods: The expression of EVI1 in HCCA tissue samples and cell lines was examined by quantitative real-time PCR (qRT-PCR), Western blotting, and immunohistochemistry (IHC). Kaplan-Meier analysis was used for survival analysis. A log-rank test was performed for univariate analysis of survival, and a Cox regression model was utilized for multivariate analysis of survival. Cell proliferation was measured by cell counting kit-8 (CCK-8), colony formation, and 5-ethynyl-2'-deoxyuridine (EdU) assays. The cell cycle was evaluated by flow cytometry. Cell apoptosis was detected by flow cytometry and a terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labelling (TUNEL) assay. In vivo tumour growth was observed for xenografts in nude mice.

Results: EVI1 expression was upregulated in HCCA tissue samples and correlated with a poor prognosis. In clinical specimens, the expression of EVI1 correlated with tumour histological grade and tumour size. Knocking down EVI1 expression reduced HCCA cell proliferation, blocked cell cycle progression, and promoted apoptosis in vitro and in vivo. Furthermore, we found that EVI1 could regulate the AKT signalling pathway by regulating PTEN levels in HCCA.

Conclusion: Our data revealed that EVI1 played important roles in HCCA tumourigenesis and development. Our findings suggest that EVI1 may be a potentially useful therapeutic target in HCCA.

Transcriptional networks in acute myeloid leukemia

Acute myeloid leukemia (AML) is a complex disease characterized by a diverse range of recurrent molecular aberrations that occur in many different combinations. Components of transcriptional networks are a common target of these aberrations, leading to network-wide changes and deployment of novel or developmentally inappropriate transcriptional programs. Genome-wide techniques are beginning to reveal the full complexity of normal hematopoietic stem cell transcriptional networks and the extent to which they are deregulated in AML, and new understandings of the mechanisms by which AML cells maintain self-renewal and block differentiation are starting to emerge. The hope is that increased understanding of the network architecture in AML will lead to identification of key oncogenic dependencies that are downstream of multiple network aberrations, and that this knowledge will be translated into new therapies that target these dependencies. Here, we review the current state of knowledge of network perturbation in AML with a focus on major mechanisms of transcription factor dysregulation, including mutation, translocation, and transcriptional dysregulation, and discuss how these perturbations propagate across transcriptional networks. We will also review emerging mechanisms of network disruption, and briefly discuss how increased knowledge of network disruption is already being used to develop new therapies.

Myeloid leukemia with high EVI1 expression is sensitive to 5-aza-2'-deoxycytidine by targeting miR-9

PURPOSE

High expression of ecotropic viral integration site 1 (EVI1) has been associated with a poor prognosis in leukemia patients, but the underlying mechanism remains unclear. Aberrant expression of microRNAs plays critical roles in leukemia development. MiR-9 is a putative potential target of EVI1. We have investigated the regulating mechanism of miR-9 by EVI1 in leukemia cells.

METHODS

We first examined the relationship between miR-9 and EVI1 expression levels in nine leukemia cell lines by RT-PCR. Then we forced high expression of EVI1 in UoCM1 and K562 cells to confirm the downregulation of miR-9 by EVI1. Methylation of the miR-9 promoter region was detected by DNA bisulfite sequencing. We treated the EVI1-overexpressing cells with the hypomethylating agent 5-aza-2'-deoxycytidine (5-AZA) to reverse EVI1-induced hypermethylation of miR-9.

RESULTS

EVI1 and miR-9 expression was negative related. Forced expression of EVI1 downregulated miR-9 by inducing hypermethylation of the miR-9 promoter. 5-AZA reversed high EVI1-induced hypermethylation of the miR-9 promoter and restored the expression of miR-9. 5-AZA induced extensive apoptosis and inhibited proliferation through cell cycle arrest in EVI1-overexpressing leukemia cells.

CONCLUSIONS

Our results suggest that EVI1 may be involved in leukemia cell proliferation and apoptosis via the regulation of miR-9 promoter methylation. 5-AZA may represent a promising therapeutic option for EVI1-high leukemia patients.

A critical role of epigenetic inactivation of miR-9 in EVI1high pediatric AML

Ectopic Viral Integration site 1 (EVI1) upregulation is implicated in 10-25% of pediatric acute myeloid leukemia (AML) and has an inferior outcome with current chemotherapy regimens. Here we report that EVI1 upregulation is associated with methylation of the miR-9 promoter and correlated with downregulation of miR-9 in human AML cell lines and bone marrow (BM) cells from pediatric patients. Reactivation of miR-9 by hypomethylating agents and forced expression of miR-9 in EVI1^high leukemia cell lines and primary leukemia cells results in apoptosis and decreased proliferation of EVI1^high leukemia cells. Furthermore, re-expression of miR-9 delays disease progression in EVI1^high leukemia-xenograft mice. Our results suggest that EVI1-induced hypermethylation and downregulation of the miR-9 plays an important role in leukemogenesis in EVI-1^high pediatric AML, indicating that hypomethylating agents may be a potential therapeutic strategy for EVI1^high pediatric AML.

Profiling of aberrant DNA methylation in acute myeloid leukemia reveals subclasses of CG-rich regions with epigenetic or genetic association

Malignant transformation is frequently associated with disease-specific epigenetic alterations, but the underlying mechanisms and pathophysiological consequences remain poorly understood. Here, we used global comparative DNA methylation profiling at CG-rich regions of 27 acute myeloid leukemia (AML) samples to select a subset of aberrantly methylated CG-rich regions (~400 regions, ~15,000 CpGs) for quantitative DNA methylation profiling in a large cohort of AML patients (n = 196) using MALDI-TOF analysis of bisulfite-treated DNA. Meta-analysis separated a subgroup of CG-rich regions showing highly correlated DNA methylation changes that were marked by histone H3 lysine 27 trimethylation in normal hematopoietic progenitor cells. While the group of non-polycomb group (PcG) target regions displayed methylation patterns that correlated well with molecular and cytogenetic markers, PcG target regions displayed a much weaker association with genetic features. However, the degree of methylation gain across the latter panel showed significant correlation with active DNMT3A levels and with overall survival. Our study suggests that both epigenetic as well as genetic aberrations underlay AML-related changes in DNA methylation at CG-rich regions and that the former may provide a marker to improve classification and prognostication of adult AML patients.

H2AFY is a novel fusion partner of MECOM in acute myeloid leukemia

The MECOM gene encoding a zinc finger protein that functions as a transcription factor, was located on chromosome 3q26, and rearrangements of MECOM often cause its overexpression in acute myeloid leukemia (AML). We identified H2AFY as a novel fusion gene partner of MECOM in an elderly male AML patient with cryptic 3q26 rearrangement using the whole transcriptome sequencing, who carried out abnormal karyotype of 46,XY,t(3;5)(q27;q31),add(14)(p11). We validated the existence of the unreported H2AFY-MECOM fusion gene by RT-PCR and Sanger DNA sequencing, and detected mutations of NRAS and BCOR in this patient. In addition, we found abnormally elevated expression of MECOM in this patient by quantitative-polymerase chain reaction (RQ-PCR). Further research is needed to investigate functional characterizations of this novel fusion in the development of AML.

3q26/EVI1 rearrangement in myelodysplastic/myeloproliferative neoplasms: An early event associated with a poor prognosis

3q26.2/EVI1 rearrangements resulting in EVI1 overexpression play an important role in leukemogenesis and are associated with treatment resistance and a poorer prognosis in patients with acute myeloid leukemia, myelodysplastic syndrome, chronic myeloid leukemia and BCR-ABL negative myeloproliferative neoplasms. In this study, we aim to explore the clinicopathological features of myelodysplastic/myeloproliferative (MDS/MPN) neoplasms with 3q26.2/EVI1 rearrangements and determine the potential impact of these cytogenetic abnormalities on treatment response and survival. The study group included 12 cases of MDS/MPN with 3q26.2 rearrangements detected by conventional karyotyping. There were 7 men and 5 women with a median age of 67 years (range, 51-79 years) at time of initial MDS/MPN diagnosis. Ten cases were classified as chronic myelomonocytic leukemia (CMML) and 2 were MDS/MPN, unclassifiable. Among CMML cases, 5 (50%) were proliferative type and 5 (50%) were dysplastic type. Based on blast counts, these 10 CMML were: CMML-0 (n = 2), CMML-1 (n = 3), and CMML-2 (n = 5). Eleven (92%) patients had 3q26 rearrangements at the initial diagnosis. Inv(3)(q21q26.2) was most common, identified in 7(58%) patients, followed by t(3;21)(q26.2;q22) in 2 patients and 1 patient each with t(3;3)(q21;q26.2), t(2;3)(p21;q26-27), and t(3;6)(q26.2;q26). Six (50%) patients had 3q26.2 rearrangements as a sole cytogenetic abnormality and 6 (50%) patients had additional cytogenetic abnormalities. Molecular studies revealed DNMT3A mutations in all 3 patients assessed and RAS mutations in 2 of 8 (25%) patients. No mutations in ASXL1 (n = 3), TET2 (n = 3), FLT3 ITD/D835 (n = 10), and CEBPA (n = 7) were detected. Most patients received hypomethylating agent based chemotherapy. The median follow-up was 11.5 months (range, 1.5-24 months) and at time of last follow-up, 11 (92%) died with a median survival of 13.4 months (range, 1.5-24 months). The only patient alive had a relatively short follow-up of 2.4 months and showed disease progression at the last visit. In conclusion, 3q26.2/EVI1 rearrangements are a rare event and usually present at time of initial diagnosis in MDS/MPN. The presence of 3q26.2/EVI1 rearrangements in MDS/MPN is associated with rapid disease progression, poor response to treatment, and a poor prognosis.

miR-22 Is a Novel Mediator of Vascular Smooth Muscle Cell Phenotypic Modulation and Neointima Formation

Supplemental Digital Content is available in the text.

Background:

MicroRNA-22 (miR-22) has recently been reported to play a regulatory role during vascular smooth muscle cell (VSMC) differentiation from stem cells, but little is known about its target genes and related pathways in mature VSMC phenotypic modulation or its clinical implication in neointima formation following vascular injury.

Methods:

We applied a wire-injury mouse model, and local delivery of AgomiR-22 or miR-22 inhibitor, as well, to explore the therapeutic potential of miR-22 in vascular diseases. Furthermore, normal and diseased human femoral arteries were harvested, and various in vivo, ex vivo, and in vitro models of VSMC phenotype switching were conducted to examine miR-22 expression during VSMC phenotype switching.

Results:

Expression of miR-22 was closely regulated during VSMC phenotypic modulation. miR-22 overexpression significantly increased expression of VSMC marker genes and inhibited VSMC proliferation and migration, whereas the opposite effect was observed when endogenous miR-22 was knocked down. As expected, 2 previously reported miR-22 target genes, MECP2 (methyl-CpG binding protein 2) and histone deacetylase 4, exhibited a regulatory role in VSMC phenotypic modulation. A transcriptional regulator and oncoprotein, EVI1 (ecotropic virus integration site 1 protein homolog), has been identified as a novel miR-22 target gene in VSMC phenotypic modulation. It is noteworthy that overexpression of miR-22 in the injured vessels significantly reduced the expression of its target genes, decreased VSMC proliferation, and inhibited neointima formation in wire-injured femoral arteries, whereas the opposite effect was observed with local application of a miR-22 inhibitor to injured arteries. We next examined the clinical relevance of miR-22 expression and its target genes in human femoral arteries. We found that miR-22 expression was significantly reduced, whereas MECP2 and EVI1 expression levels were dramatically increased, in diseased in comparison with healthy femoral human arteries. This inverse relationship between miR-22 and MECP2 and EVI1 was evident in both healthy and diseased human femoral arteries.

Conclusions:

Our data demonstrate that miR-22 and EVI1 are novel regulators of VSMC function, specifically during neointima hyperplasia, offering a novel therapeutic opportunity for treating vascular diseases.

DNMT3a methylation in neuropathic pain

Background

Mu opioid receptor (MOR) plays a crucial role in mediating analgesic effects of opioids and is closely associated with the pathologies of neuropathic pain. Previous studies have reported that peripheral nerve injury downregulates MOR expression, but the epigenetic mechanisms remain unknown.

Objective

Therefore, we investigated DNA methyltransferase3a (DNMT3a) expression or methylation changes within MOR promoter in the spinal cord in a neuropathic pain induced by a chronic constriction injury (CCI) mouse model and further determined whether these injury-associated changes are reversible by pharmacological interventions.

Methods

A CCI mouse model was established and tissue specimens of lumbar spinal cords were collected. The nociception threshold was evaluated by a Model Heated 400 Base. DNMT3a and MOR mRNA and protein level were detected by real-time-polymerase chain reaction and Western blot, respectively. Methylation of DNMT3a gene was measured by methylation-specific PCR.

Results

Our data showed that chronic nerve injury led to a significant upregulation of DNMT3a expression that was associated with increased methylation of MOR gene promoter and decreased MOR protein expression in the spinal cord. Inhibition of DNMT3a catalytic activity with DNMT inhibitor RG108 significantly blocked the increase in methylation of the MOR promoter, and then upregulated MOR expression and attenuated thermal hyperalgesia in neuropathic pain mice.

Conclusion

This study demonstrates that an increase of DNMT3a expression and MOR methylation epigenetically play an important role in neuropathic pain. Targeting DNMT3a to the promoter of MOR gene by DNMT inhibitor may be a promising approach to the development of new neuropathic pain therapy.

Acquired cross-linker resistance associated with a novel spliced BRCA2 protein variant for molecular phenotyping of BRCA2 disruption

BRCA2 encodes a protein with a fundamental role in homologous recombination that is essential for normal development. Carrier status of mutations in BRCA2 is associated with familial breast and ovarian cancer, while bi-allelic BRCA2 mutations can cause Fanconi anemia (FA), a cancer predisposition syndrome with cellular cross-linker hypersensitivity. Cancers associated with BRCA2 mutations can acquire chemo-resistance on relapse. We modeled acquired cross-linker resistance with an FA-derived BRCA2-mutated acute myeloid leukemia (AML) platform. Associated with acquired cross-linker resistance was the expression of a functional BRCA2 protein variant lacking exon 5 and exon 7 (BRCA2^ΔE5+7), implying a role for BRCA2 splicing for acquired chemo-resistance. Integrated network analysis of transcriptomic and proteomic differences for phenotyping of BRCA2 disruption infers impact on transcription and chromatin remodeling in addition to the DNA damage response. The striking overlap with transcriptional profiles of FA patient hematopoiesis and BRCA mutation associated ovarian cancer helps define and explicate the ‘BRCAness’ profile.

Reprogramming acute myeloid leukemia into sensitivity for retinoic-acid-driven differentiation

The success of all-trans retinoic acid (ATRA) therapy for acute promyelocytic leukemia (APL) provides a rationale for using retinoic acid (RA)-based therapy for other subtypes of acute myeloid leukemia (AML). Recently, several studies showed that ATRA may drive leukemic cells efficiently into differentiation and/or apoptosis in a subset of AML patients with an NPM1 mutation, a FLT3-ITD, an IDH1 mutation, and patients overexpressing EVI-1. Because not all patients within these molecular subgroups respond to ATRA and clinical trials that tested ATRA response in non-APL AML patients have had disappointing results, the identification of additional biomarkers may help to identify patients who strongly respond to ATRA-based therapy. Searching for response biomarkers might also reveal novel RA-based combination therapies with an efficient differentiation/apoptosis-inducing effect in non-APL AML patients. Preliminary studies suggest that the epigenetic or transcriptional state of leukemia cells determines their susceptibility to ATRA. We hypothesize that reprogramming by inhibitors of epigenetic-modifying enzymes or by modulation of microRNA expression might sensitize non-APL AML cells for RA-based therapy. AML relapse is caused by a subpopulation of leukemia cells, named leukemic stem cells (LSCs), which are in a different epigenetic state than the total bulk of the AML. The survival of LSCs after therapy is the main cause of the poor prognosis of AML patients, and novel differentiation therapies should drive these LSCs into maturity. In this review, we summarize the current knowledge on the epigenetic aspects of susceptibility to RA-induced differentiation in APL and non-APL AML.

Epigenetics in Cancer: A Hematological Perspective

For several decades, we have known that epigenetic regulation is disrupted in cancer. Recently, an increasing body of data suggests epigenetics might be an intersection of current cancer research trends: next generation sequencing, immunology, metabolomics, and cell aging. The new emphasis on epigenetics is also related to the increasing production of drugs capable of interfering with epigenetic mechanisms and able to trigger clinical responses in even advanced phase patients. In this review, we will use myeloid malignancies as proof of concept examples of how epigenetic mechanisms can trigger or promote oncogenesis. We will also show how epigenetic mechanisms are related to genetic aberrations, and how they affect other systems, like immune response. Finally, we will show how we can try to influence the fate of cancer cells with epigenetic therapy.

Pediatric chronic myeloid leukemia with inv(3)(q21q26.2) and T lymphoblastic transformation: a case report

Background

Chronic myeloid leukemia (CML) comprises ~3 % of pediatric leukemia. Although therapy with tyrosine kinase inhibitors (TKIs) is highly effective for CML, multiple factors have been identified as predictive of treatment failure. Chromosomal abnormalities involving the MECOM locus at 3q26 portend therapy resistant disease in adults, yet have never been described in pediatric patients and have not been associated with T lymphoblastic progression.

Case presentation

We present a case of an 11-year-old boy with CML possessing the unique combination of T lymphoblastic transformation and a subclone harboring inv(3)(q21q26.2) at diagnosis. This is the first reported case of pediatric CML with inv(3)(q21q26.2) and the first case of T lymphoblastic progression associated with this karyotype. The patient was treated with single agent TKI therapy with robust initial response. Marrow histology at one month showed restoration of trilineage hematopoiesis and BCR-ABL RT-PCR at three months showed a 1.4 log reduction in transcript levels.

Conclusions

The karyotypic abnormality of inv(3)(q21q26.2) in CML is not restricted to adult patients. Moreover, while chromosome 3 abnormalities are markers of TKI resistance in adults, our patient showed a robust early response to single agent TKI therapy. This finding suggests pediatric CML with inv(3)(q21q26.2) may have distinct features and more favorable treatment responses than those described in adults.

Identification of differentially methylated markers among cytogenetic risk groups of acute myeloid leukemia

Aberrant DNA methylation is known to occur in cancer, including hematological malignancies such as acute myeloid leukemia (AML). However, less is known about whether specific methylation profiles characterize specific subcategories of AML. We examined this issue by using comprehensive high-throughput array-based relative methylation analysis (CHARM) to compare methylation profiles among patients in different AML cytogenetic risk groups. We found distinct profiles in each group, with the high-risk group showing overall increased methylation compared with low- and mid-risk groups. The differentially methylated regions (DMRs) distinguishing cytogenetic risk groups of AML were enriched in the CpG island shores. Specific risk-group associated DMRs were located near genes previously known to play a role in AML or other malignancies, such as MN1, UHRF1, HOXB3, and HOXB4, as well as TRIM71, the function of which in cancer is not well characterized. These findings were verified by quantitative bisulfite pyrosequencing and by comparison with results available at the TCGA cancer genome browser. To explore the potential biological significance of the observed methylation changes, we correlated our findings with gene expression data available through the TCGA database. The results showed that decreased methylation at HOXB3 and HOXB4 was associated with increased gene expression of both HOXB genes specific to the mid-risk AML, while increased DNA methylation at DCC distinctive to the high-risk AML was associated with increased gene expression. Our results suggest that the differential impact of cytogenetic changes on AML prognosis may, in part, be mediated by changes in methylation.

Epigenetics and approaches to targeted epigenetic therapy in acute myeloid leukemia

Acute myeloid leukemia (AML) is the most common type of acute leukemia in adults. AML is a heterogeneous malignancy characterized by distinct genetic abnormalities. Recent discoveries have highlighted an additional important role of dysregulated epigenetic mechanisms in the pathogenesis of the disease. In contrast to genetic changes, epigenetic modifications are frequently reversible, which provides opportunities for targeted treatment using specific inhibitors. In this review, we will provide an overview of the current state of epigenetics and epigenetic therapy in AML and will describe perspectives on how to identify promising new approaches for epigenetic targeted treatment.

Primary acute myeloid leukemia cells with overexpression of EVI-1 are sensitive to all-trans retinoic acid

Enhanced expression of ecotropic viral integration site 1 (EVI-1) occurs in ∼10% of acute myeloid leukemia (AML) patients and is associated with a very poor disease outcome. Patients with EVI-1-positive AML have poor initial responses to chemotherapy and high relapse rates, indicating an urgent need for alternative treatment strategies improving clinical outcome for these patients. Because treatment of acute promyelocytic patients with all-trans retinoic acid (ATRA) has improved the survival of these patients substantially, we investigated whether ATRA might also be effective for the subgroup of AML patients with EVI-1 overexpression. Here, we show that a substantial part of the EVI-1-positive AML cases respond to ATRA by induction of differentiation and decreased clonogenic capacity of myeloid blasts. Most importantly, we demonstrate that in vivo treatment of primary EVI-1-positive AML with ATRA leads to a significant reduction in leukemic engraftment. Altogether, our results show that a considerable part of the EVI-1-positive primary AML cases are sensitive to ATRA, suggesting that combining ATRA with the currently used conventional chemotherapy might be a promising treatment strategy decreasing relapse rates and enhancing complete remissions in this poor prognostic subgroup of AML patients.

The role of EVI-1 in normal hematopoiesis and myeloid malignancies (Review)

Ecotropic virus integration site-1 (EVI-1) gene, locus on chromosome 3 (3q26.2) in the human genome, was first found in the AKXD strain of mice, in a model of retrovirus-induced acute myeloid leukemia (AML) established twenty years ago. Since then, EVI-1 was regarded as one of the most invasive proto-oncogenes in human leukemia. EVI-1 can encode a unique zinc-finger protein of 145 kDa that can bind with DNA, and its overexpression was closely related to human hemopoietic diseases. Furthermore, accumulating research indicates that EVI-1 is involved in the differentiation, apoptosis and proliferation of leukemia cells. The present review focuses on the biochemical properties of EVI-1 which plays a role in myeloid malignancies.

The use of molecular genetics to refine prognosis in acute myeloid leukemia

The discovery and application of advanced molecular techniques, such as gene and microRNA expression profiling, whole genome and exome sequencing, proteomic analysis and methylation assays, have allowed for the identification of recurrent molecular abnormalities in acute myeloid leukemia (AML) that have revolutionized our understanding of the genetic landscape of the disease. These modalities have emerged as valuable tools that permit a more comprehensive and detailed molecular characterization of AML. Many of these molecular abnormalities have been shown to predict prognosis, particularly within the context of cytogenetically normal AML. This review will discuss the major techniques and platforms that have been used to identify novel recurrent gene mutations in AML and briefly describe how these discoveries have impacted on outcome prediction.

Induction of the proapoptotic tumor suppressor gene Cell Adhesion Molecule 1 by chemotherapeutic agents is repressed in therapy resistant acute myeloid leukemia

Even though a large proportion of patients with acute myeloid leukemia (AML) achieve a complete remission upon initial therapy, the majority of them eventually relapse with resistant disease. Overexpression of the gene coding for the transcription factor Ecotropic Virus Integration site 1 (EVI1) is associated with rapid disease recurrence and shortened survival. We therefore sought to identify EVI1 target genes that may play a role in chemotherapy resistance using a previously established in vitro model system for EVI1 positive myeloid malignancies. Gene expression microarray analyses uncovered the Cell Adhesion Molecule 1 (CADM1) gene as a candidate whose deregulation by EVI1 may contribute to drug refractoriness. CADM1 is an apoptosis inducing tumor suppressor gene that is inactivated by methylation in a variety of tumor types. In the present study we provide evidence that it may play a role in chemotherapy induced cell death in AML: CADM1 was induced by drugs used in the treatment of AML in a human myeloid cell line and in primary diagnostic AML samples, and its experimental expression in a cell line model increased the proportion of apoptotic cells. CADM1 up-regulation was abolished by ectopic expression of EVI1, and EVI1 expression correlated with increased CADM1 promoter methylation both in a cell line model and in primary AML cells. Finally, CADM1 induction was repressed in primary samples from AML patients at relapse. In summary, these data suggest that failure to up-regulate CADM1 in response to chemotherapeutic drugs may contribute to therapy resistance in AML.

Impact of MLL5 expression on decitabine efficacy and DNA methylation in acute myeloid leukemia

Hypomethylating agents are widely used in patients with myelodysplastic syndromes and unfit patients with acute myeloid leukemia. However, it is not well understood why only some patients respond to hypomethylating agents. We found previously that the effect of decitabine on hematopoietic stem cell viability differed between Mll5 wild-type and null cells. We, therefore, investigated the role of MLL5 expression levels on outcome of acute myeloid leukemia patients who were treated with decitabine. MLL5 above the median expression level predicted longer overall survival independent of DNMT3A mutation status in bivariate analysis (median overall survival for high vs. low MLL5 expression 292 vs. 167 days; P=0.026). In patients who received three or more courses decitabine, high MLL5 expression and wild-type DNMT3A independently predicted improved overall survival (median overall survival for high vs. low MLL5 expression 468 vs. 243 days; P=0.012). In transformed murine cells, loss of Mll5 was associated with resistance to low-dose decitabine, less global DNA methylation in promoter regions, and reduced DNA demethylation upon decitabine treatment. Together, these data support our clinical observation of improved outcome in decitabine-treated patients who express MLL5 at high levels, and suggest a mechanistic role of MLL5 in the regulation of DNA methylation.

Isocitrate dehydrogenase 1 (IDH1) mutation in breast adenocarcinoma is associated with elevated levels of serum and urine 2-hydroxyglutarate

Mutations in the IDH1 and IDH2 (isocitrate dehydrogenase) genes have been discovered across a range of solid-organ and hematologic malignancies, including acute myeloid leukemia, glioma, chondrosarcoma, and cholangiocarcinoma. An intriguing aspect of IDH-mutant tumors is the aberrant production and accumulation of the oncometabolite 2-hydroxyglutarate (2-HG), which may play a pivotal oncogenic role in these malignancies. We describe the first reported case of an IDH1 p.R132L mutation in a patient with hormone receptor-positive (HR+) breast adenocarcinoma. This patient was initially treated for locally advanced disease, but then suffered a relapse and metastasis, at which point an IDH1-R132 mutation was discovered in an affected lymph node. The mutation was subsequently found in the primary tumor tissue and all metastatic sites, but not in an uninvolved lymph node. In addition, the patient's serum and urine displayed marked elevations in the concentration of 2-HG, significantly higher than that measured in six other patients with metastatic HR+ breast carcinoma whose tumors were found to harbor wild-type IDH1. In summary, IDH1 mutations may impact a rare subgroup of patients with breast adenocarcinoma. This may suggest future avenues for disease monitoring through noninvasive measurement of 2-HG, as well as for the development and study of targeted therapies against the aberrant IDH1 enzyme.

A remote GATA2 hematopoietic enhancer drives leukemogenesis in inv(3)(q21;q26) by activating EVI1 expression

Chromosomal inversion between 3q21 and 3q26 results in high-risk acute myeloid leukemia (AML). In this study, we identified a mechanism whereby a GATA2 distal hematopoietic enhancer (G2DHE or -77-kb enhancer) is brought into close proximity to the EVI1 gene in inv(3)(q21;q26) inversions, leading to leukemogenesis. We examined the contribution of G2DHE to leukemogenesis by creating a bacterial artificial chromosome (BAC) transgenic model that recapitulates the inv(3)(q21;q26) allele. Transgenic mice harboring a linked BAC developed leukemia accompanied by EVI1 overexpression-neoplasia that was not detected in mice bearing the same transgene but that was missing the GATA2 enhancer. These results establish the mechanistic basis underlying the pathogenesis of a severe form of leukemia through aberrant expression of the EVI1 proto-oncogene.

Chromatin modifiers and the promise of epigenetic therapy in acute leukemia

Hematopoiesis is a tightly regulated process involving the control of gene expression that directs the transition from hematopoietic stem and progenitor cells to terminally differentiated blood cells. In leukemia, the processes directing self-renewal, differentiation and progenitor cell expansion are disrupted, leading to the accumulation of immature, non-functioning malignant cells. Insights into these processes have come in stages, based on technological advances in genetic analyses, bioinformatics and biological sciences. The first cytogenetic studies of leukemic cells identified chromosomal translocations that generate oncogenic fusion proteins and most commonly affect regulators of transcription. This was followed by the discovery of recurrent somatic mutations in genes encoding regulators of the signal transduction pathways that control cell proliferation and survival. Recently, studies of global changes in methylation and gene expression have led to the understanding that the output of transcriptional regulators and the proliferative signaling pathways are ultimately influenced by chromatin structure. Candidate gene, whole-genome and whole-exome sequencing studies have identified recurrent somatic mutations in genes encoding epigenetic modifiers in both acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL). In contrast to the two-hit model of leukemogenesis, emerging evidence suggests that these epigenetic modifiers represent a class of mutations that are critical to the development of leukemia and affect the regulation of various other oncogenic pathways. In this review, we discuss the range of recurrent, somatic mutations in epigenetic modifiers found in leukemia and how these modifiers relate to the classical leukemogenic pathways that lead to impaired cell differentiation and aberrant self-renewal and proliferation.

The role of EVI1 in myeloid malignancies

The EVI1 oncogene at human chr 3q26 is rearranged and/or overexpressed in a subset of acute myeloid leukemias and myelodysplasias. The EVI1 protein is a 135 kDa transcriptional regulator with DNA-binding zinc finger domains. Here we provide a critical review of the current state of research into the molecular mechanisms by which this gene plays a role in myeloid malignancies. The major pertinent cellular effects are blocking myeloid differentiation and preventing cellular apoptosis, and several potential mechanisms for these phenomena have been identified. Evidence supports a role for EVI1 in inducing cellular quiescence, and this may contribute to the resistance to chemotherapy seen in patients with neoplasms that overexpress EVI1. Another isoform, MDS1-EVI1 (or PRDM3), encoded by the same locus as EVI1, harbors an N-terminal histone methyltransferase(HMT) domain; experimental findings indicate that this protein and its HMT activity are critical for the progression of a subset of AMLs, and this provides a potential target for therapeutic intervention.

Variability in DNA methylation defines novel epigenetic subgroups of DLBCL associated with different clinical outcomes

Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive form of non-Hodgkin lymphoma with variable biology and clinical behavior. The current classification does not fully explain the biological and clinical heterogeneity of DLBCLs. In this study, we carried out genomewide DNA methylation profiling of 140 DLBCL samples and 10 normal germinal center B cells using the HpaII tiny fragment enrichment by ligation-mediated polymerase chain reaction assay and hybridization to a custom Roche NimbleGen promoter array. We defined methylation disruption as a main epigenetic event in DLBCLs and designed a method for measuring the methylation variability of individual cases. We then used a novel approach for unsupervised hierarchical clustering based on the extent of DNA methylation variability. This approach identified 6 clusters (A-F). The extent of methylation variability was associated with survival outcomes, with significant differences in overall and progression-free survival. The novel clusters are characterized by disruption of specific biological pathways such as cytokine-mediated signaling, ephrin signaling, and pathways associated with apoptosis and cell-cycle regulation. In a subset of patients, we profiled gene expression and genomic variation to investigate their interplay with methylation changes. This study is the first to identify novel epigenetic clusters of DLBCLs and their aberrantly methylated genes, molecular associations, and survival.

Association between DNA methyltransferases 3B gene polymorphisms and the susceptibility to acute myeloid leukemia in Chinese Han population

DNMT3B plays a crucial role in the generation of aberrant methylation during carcinogenesis. Polymorphisms in the DNMT3B gene may influence the DNA methylation enzymatic activity of DNMT3B, thereby modulating the susceptibility to AML. Thus, we investigated the association between SNPs in the DNMT3Bgene and their haplotypes with the risk of AML in the Chinese Han population. The DNMT3B genotype was determined by HRM in 317 de novo AML patients and 406 healthy control subjects matched for age and gender. Among the 5 SNPs investigated in this study, rs2424913 demonstrated no polymorphisms in the Chinese Han populations, rs1569686 and rs2424908 were significantly associated with AML risk. The GG genotype of rs1569686 was associated with increased AML risk (OR: 5.76; 95%CI: 2.60-12.73; P<0.01) compared with the TT genotype, and individuals with a G allele had a significantly increased risk (OR: 1.89; 95%CI: 1.41-2.52; P<0.01) for AML compared with those harboring a C allele, this polymorphism can predict the risk of AML in a minority of patients. While the CC genotype of rs2424908 appeared to reduce the AML risk (OR: 0.57; 95%CI: 0.36-0.91; P=0.01) compared with the TT genotype, individuals with a C allele were associated with a lower risk (OR: 0.79, 95%CI: 0.64-0.97, P=0.03) for developing AML compared with those harboring a T allele. The other 2 SNPs, rs6087990 and rs6119954, had no significant association with AML risk in the study population. The CGGT, CTAT, TGAT, and CGAT haplotypes of rs6087990, rs1569686, rs6119954, and rs2424908 appeared to significantly increase the AML risk, and the TTGC haplotype appeared to significantly reduce the risk. These results suggest that DNMT3B polymorphisms may contribute to the genetic susceptibility to AML; in particular, the G allele of rs1569686 serves as a risk factor for AML, whereas the C allele of rs2424908 represents a potential protective factor.

Induction of Chromosomal Instability via Telomere Dysfunction and Epigenetic Alterations in Myeloid Neoplasia

Chromosomal instability (CIN) is a characteristic feature of cancer. In this review, we concentrate on mechanisms leading to CIN in myeloid neoplasia, i.e., myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML). The pathogenesis of myeloid neoplasia is complex and involves genetic and epigenetic alterations. Chromosome aberrations define specific subgroups and guide clinical decisions. Genomic instability may play an essential role in leukemogenesis by promoting the accumulation of genetic lesions responsible for clonal evolution. Indeed, disease progression is often driven by clonal evolution into complex karyotypes. Earlier studies have shown an association between telomere shortening and advanced MDS and underlined the important role of dysfunctional telomeres in the development of genetic instability and cancer. Several studies link chromosome rearrangements and aberrant DNA and histone methylation. Genes implicated in epigenetic control, like DNMT3A, ASXL1, EZH2 and TET2, have been discovered to be mutated in MDS. Moreover, gene-specific hypermethylation correlates highly significantly with the risk score according to the International Prognostic Scoring System. In AML, methylation profiling also revealed clustering dependent on the genetic status. Clearly, genetic instability and clonal evolution are driving forces for leukemic transformation. Understanding the mechanisms inducing CIN will be important for prevention and for novel approaches towards therapeutic interventions.

Epigenetic aberrations in myeloid malignancies (Review)

The development of novel technologies, such as massively parallel DNA sequencing, has led to the identification of several novel recurrent gene mutations, such as DNA methyltransferase (Dnmt)3a, ten-eleven-translocation oncogene family member 2 (TET2), isocitrate dehydrogenase (IDH)1/2, additional sex comb-like 1 (ASXL1), enhancer of zeste homolog 2 (EZH2) and ubiquitously transcribed tetratricopeptide repeat X chromosome (UTX) mutations in acute myeloid leukemia (AML) and other myeloid malignancies. These findings strongly suggest a link between recurrent genetic alterations and aberrant epigenetic regulations, resulting from an abnormal DNA methylation and histone modification status. This review focuses on the current findings of aberrant epigenetic signatures by these newly described genetic alterations. Moreover, epigenetic aberrations resulting from transcription factor aberrations, such as mixed lineage leukemia (MLL) rearrangement, ecotropic viral integration site 1 (Evi1) overexpression, chromosomal translocations and the downregulation of PU.1 are also described.

Phosphorylation of the leukemic oncoprotein EVI1 on serine 196 modulates DNA binding, transcriptional repression and transforming ability

The EVI1 (ecotropic viral integration site 1) gene at 3q26 codes for a transcriptional regulator with an essential role in haematopoiesis. Overexpression of EVI1 in acute myeloid leukaemia (AML) is frequently associated with 3q26 rearrangements and confers extremely poor prognosis. EVI1 mediates transcriptional regulation, signalling, and epigenetic modifications by interacting with DNA, proteins and protein complexes. To explore to what extent protein phosphorylation impacts on EVI1 functions, we analysed endogenous EVI1 protein from a high EVI1 expressing Fanconi anaemia (FA) derived AML cell line. Mass spectrometric analysis of immunoprecipitated EVI1 revealed phosphorylation at serine 196 (S196) in the sixth zinc finger of the N-terminal zinc finger domain. Mutated EVI1 with an aspartate substitution at serine 196 (S196D), which mimics serine phosphorylation of this site, exhibited reduced DNA-binding and transcriptional repression from a gene promotor selectively targeted by the N-terminal zinc finger domain. Forced expression of the S196D mutant significantly reduced EVI1 mediated transformation of Rat1 fibroblasts. While EVI1-mediated serial replating of murine haematopoietic progenitors was maintained by EVI1-S196D, this was associated with significantly higher Evi1-trancript levels compared with WT-EVI1 or EVI1-S196A, mimicking S196 non-phosphorylated EVI1. These data suggest that EVI1 function is modulated by phosphorylation of the first zinc finger domain.

Clinical results with the DNA hypomethylating agent 5-aza-2'-deoxycytidine (decitabine) in patients with myelodysplastic syndromes: an update

Patients with myelodysplastic syndromes (MDS), especially those with high-risk disease, other comorbidities, or of advanced age, still have a limited prognosis. In addition to cytotoxic chemotherapies, hypomethylating agents such as decitabine (5-aza-2'-deoxycytidine) and azacitidine (5-azacytidine), have been approved during the past decade and represent a very important option for the treatment of MDS today. Due to their lower toxicity compared to conventional chemotherapy, hypomethylating agents are often a safe and feasible alternative also for frail patients. Decitabine has been shown to be active in numerous studies including International Prognostic Scoring System (IPSS) intermediate-1 to high risk patients, in secondary acute myeloid leukemia (AML) arising from MDS, and in MDS with poor-risk cytogenetics. Furthermore, decitabine has been studied in the allograft setting and in combination treatment regimens, and may play a role in epigenetic "priming" before conventional chemotherapy. This review summarizes the results of clinical trials and experiences with decitabine not only in first-line and single-agent treatment regimens but also as second-line treatment after prior treatment failure, in the context of the allograft setting and as part of combination treatment regimens.

Recent progress toward epigenetic therapies: the example of mixed lineage leukemia

The importance of epigenetic gene regulatory mechanisms in normal and cancer development is increasingly evident. Genome-wide analyses have revealed the mutation, deletion, and dysregulated expression of chromatin-modifying enzymes in a number of cancers, including hematologic malignancies. Genome-wide studies of DNA methylation and histone modifications are beginning to reveal the landscape of cancer-specific chromatin patterns. In parallel, recent genetic loss-of-function studies in murine models are demonstrating functional involvement of chromatin-modifying enzymes in malignant cell proliferation and self-renewal. Paradoxically, the same chromatin modifiers can, depending on cancer type, be either hyperactive or inactivated. Increasingly, cross talk between epigenetic pathways is being identified. Leukemias carrying MLL rearrangements are quintessential cancers driven by dysregulated epigenetic mechanisms in which fusion proteins containing N-terminal sequences of MLL require few or perhaps no additional mutations to cause human leukemia. Here, we review how recent progress in the field of epigenetics opens potential mechanism-based therapeutic avenues.

Monitoring Response and Resistance to the Novel Arsenical Darinaparsin in an AML Patient

Acute myeloid leukemia (AML) with inversion of chromosome 3 is characterized by overexpression of EVI1 and carries a dismal prognosis. Arsenic-containing compounds have been described to be efficacious in malignancies overexpressing EVI1. Here, we describe a case of AML with inv(3)(q21q26.2) treated with the organic arsenical darinaparsin. Using a “personalized medicine approach,” two different arsenicals were screened for anti-leukemic effect against the patient’s cells ex vivo. The most promising compound, darinaparsin, was selected for in vivo treatment. Clinical effect was almost immediate, with a normalization of temperature, a stabilization of white blood cell (WBC) counts and an increased quality of life. Longitudinal monitoring of patient response and resistance incorporating significant correlative studies on patient-derived blood samples over the two cycles of darinaparsin given to this patient allowed us to evaluate potential mechanisms of response and resistance. The anti-leukemic effects of darinaparsin correlated with inhibition of the alternative NF-κB pathway and production of the inflammatory cytokine IL-8. Emergence of resistance was suspected during treatment cycle 2 and supported by xenograft studies in nude mice. Darinaparsin resistance correlated with an attenuation of the effect of treatment on the alternative NF-κB pathway. The results from this patient indicate that darinaparsin may be a good treatment option for inv(3) AML and that inhibition of the alternative NF-κB pathway may be predictive of response. Longitudinal monitoring of disease response as well as several correlative parameters allowed for the generation of novel correlations and predictors of response to experimental therapy in a heavily pretreated patient.

Promoter demethylation of cystathionine-β-synthetase gene contributes to inflammatory pain in rats

Hydrogen sulfide (H(2)S), an endogenous gas molecule synthesized by cystathionine-β-synthetase (CBS), is involved in inflammation and nociceptive signaling. However, the molecular and epigenetic mechanisms of CBS-H(2)S signaling in peripheral nociceptive processing remain unknown. We demonstrated that peripheral inflammation induced by intraplantar injection of complete Freund adjuvant significantly up-regulated expression of CBS at both protein and mRNA levels in rat dorsal root ganglia (DRG). The CBS inhibitors hydroxylamine and aminooxyacetic acid attenuated mechanical hyperalgesia in a dose-dependent manner and reversed hyperexcitability of DRG neurons in inflamed rats. Intraplantar administration of NaHS (its addition mimics CBS production of H(2)S) or l-cysteine in healthy rats elicited mechanical hyperalgesia. Application of NaHS in vitro enhanced excitability and tetrodotoxin (TTX)-resistant sodium current of DRG neurons from healthy rats, which was attenuated by pretreatment of protein kinase A inhibitor H89. Methylation-specific PCR and bisulfite sequencing demonstrated that promoter region of cbs gene was less methylated in DRG samples from inflamed rats than that from controls. Peripheral inflammation did not alter expression of DNA methyltransferase 3a and 3b, the 2 major enzymes for DNA methylation, but led to a significant up-regulation of methyl-binding domain protein 4 and growth arrest and DNA damage inducible protein 45α, the enzymes involved in active DNA demethylation. Our findings suggest that epigenetic regulation of CBS expression may contribute to inflammatory hyperalgesia. H(2)S seems to increase TTX-resistant sodium channel current, which may be mediated by protein kinase A pathway, thus identifying a potential therapeutic target for the treatment of chronic pain.