Overexpression of EZH2 associates with a poor prognosis in chronic lymphocytic leukemia

Biological, prognostic, and therapeutic impact of the epigenome in CLL

Chronic lymphocytic leukemia (CLL) is characterized by widespread alterations in the genetic and epigenetic landscapes which seem to underlie the variable clinical manifestations observed in patients. Over the last decade, epigenomic studies have described the whole-genome maps of DNA methylation and chromatin features of CLL and normal B cells, identifying distinct epigenetic mechanisms operating in tumoral cells. DNA methylation analyses have identified that the CLL methylome contains imprints of the cell of origin, as well as of the proliferative history of the tumor cells, with both being strong independent prognostic predictors. Moreover, single-cell analysis revealed a higher degree of DNA methylation noise in CLL cells, which associates with transcriptional plasticity and disease aggressiveness. Integrative analysis of chromatin has uncovered chromatin signatures, as well as regulatory regions specifically active in each CLL subtype or in Richter transformed samples. Unique transcription factor (TF) binding motifs are overrepresented on those regions, suggesting that altered TF networks operate from disease initiation to progression as nongenetic factors mediating the oncogenic transcriptional profiles. Multiomics analysis has identified that response to treatment is modulated by an epigenetic imprint, and that treatments affect chromatin through the activity of particular set of TFs. Additionally, the epigenome is an axis of therapeutic vulnerability in CLL, as it can be targeted by inhibitors of histone modifying enzymes, that have shown promising preclinical results. Altogether, this review aims at summarizing the major findings derived from published literature to distill how altered epigenomic mechanisms contribute to CLL origin, evolution, clinical behavior, and response to treatment.

Advances in epigenetic alterations of chronic lymphocytic leukemia: from pathogenesis to treatment

Chronic lymphocytic leukemia (CLL) is a heterogeneous disease with alterations in genetic expression and epigenetic modifications. In recent years, the new insight into epigenetics in the pathogenesis of CLL has been developed considerably, including DNA methylation, histone modification, RNA methylation, non-coding RNAs as well as chromatin remodeling. Epigenetic modification regulates various processes such as stem cell biology, cell growth, and tumorigenesis without altering gene sequence. Growing evidence indicates that the disturbance of gene expression profiles which were regulated by epigenetic modifications exerts vital roles in the development and progress in CLL, which provides novel perspectives to explore the etiology of CLL. In addition, the integration with epigenetic therapeutic targets and the in-depth understanding of epigenetic therapy contribute to develop new therapeutic strategies for CLL. Herein, the present review discusses the advances of epigenetic alterations in the pathogenesis, diagnosis, and prognostic assessment of CLL patients and also highlights existing and emerging agents targeting epigenetic regulators.

Design, synthesis and mechanism studies of dual EZH2/BRD4 inhibitors for cancer therapy

Aberrant expression of EZH2 is frequently observed in cancers, and the EZH2 inhibitors are only effective in hematological malignancies and almost noneffective against solid tumors. It has been reported that the combination of EZH2 and BRD4 inhibitors may be a promising strategy to treat solid tumors being insensitive to EZH2 inhibitors. Thus, a series of EZH2/BRD4 dual inhibitors were designed and synthesized. The optimized compound 28, encoded as KWCX-28, was the most potential compound by the SAR studies. Further mechanism studies showed that KWCX-28 inhibited HCT-116 cells proliferation (IC50 = 1.86 µM), induced HCT-116 cells apoptosis, arrested cell cycle arrest at G0/G1 phase and resisted the histone 3 lysine 27 acetylation (H3K27ac) upregulation. Therefore, KWCX-28 was a potential dual EZH2/BRD4 inhibitors for treating solid tumors.

Inhibition of EZH2 alleviates SAHA-induced senescence-associated secretion phenotype in small cell lung cancer cells

Chemotherapy has been widely used in small cell lung cancer (SCLC) treatment in the past decades. However, SCLC is easy to recur after chemotherapy. The senescence of cancer cells during chemotherapy is one of the effective therapeutic strategies to inhibit the progression of cancer. Nevertheless, the senescence-associated secretion phenotype (SASP) promotes chronic inflammation of the cancer microenvironment and further accelerates the progression of tumors. Therefore, inducing the senescence of cancer cells and inhibiting the production of SASP factors during anticancer treatment have become effective therapeutic strategies to improve the anticancer effect of drugs. Here we reported that SCLC cells treated with an FDA-approved HDAC inhibitor SAHA underwent senescence and displayed remarkable SASP. In particular, SAHA promoted the formation of cytoplasmic chromatin fragments (CCFs) in SCLC cells. The increased CCFs in SAHA-treated SCLC cells were related to nuclear porin Tpr, which activated the cGAS-STING pathway, and promoted the secretion of SASP in cancer cells. Inhibition of EZH2 suppressed the increase of CCFs in SAHA-treated SCLC cells, weakened the production of SASP, and increased the antiproliferative effect of SAHA. Overall, our work affords new insight into the secretion of SASP in SCLC and establishes a foundation for constructing a new therapeutic strategy for SCLC patients.

The roles of histone modifications in tumorigenesis and associated inhibitors in cancer therapy

Histone modifications are key factors in chromatin packaging, and are responsible for gene regulation during cell fate determination and development. Abnormal alterations in histone modifications potentially affect the stability of the genome and disrupt gene expression patterns, leading to many diseases, including cancer. In recent years, mounting evidence has shown that various histone modifications altered by aberrantly expressed modifier enzymes contribute to tumor development and metastasis through the induction of epigenetic, transcriptional, and phenotypic changes. In this review, we will discuss the existing histone modifications, both well-studied and rare ones, and their roles in solid tumors and hematopoietic cancers, to identify the molecular pathways involved and investigate targeted therapeutic drugs to reorganize the chromatin and enhance cancer treatment efficiency. Finally, clinical inhibitors of histone modifications are summarized to better understand the developmental stage of cancer therapy in using these drugs to inhibit the histone modification enzymes.

Targeting metabolic reprogramming in chronic lymphocytic leukemia

Metabolic reprogramming, fundamentally pivotal in carcinogenesis and progression of cancer, is considered as a promising therapeutic target against tumors. In chronic lymphocytic leukemia (CLL) cells, metabolic abnormalities mediate alternations in proliferation and survival compared with normal B cells. However, the role of metabolic reprogramming is still under investigation in CLL. In this review, the critical metabolic processes of CLL were summarized, particularly glycolysis, lipid metabolism and oxidative phosphorylation. The effects of T cells and stromal cells in the microenvironment on metabolism of CLL were also elucidated. Besides, the metabolic alternation is regulated by some oncogenes and tumor suppressor regulators, especially TP53, MYC and ATM. Thus, the agents targeting metabolic enzymes or signal pathways may impede the progression of CLL. Both the inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) statins and the lipoprotein lipase inhibitor orlistat induce the apoptosis of CLL cells. In addition, a series of oxidative phosphorylation inhibitors play important roles in decreasing the proliferation of CLL cells. We epitomized recent advancements in metabolic reprogramming in CLL and discussed their clinical potentiality for innovative therapy options. Metabolic reprogramming plays a vital role in the initiation and progression of CLL. Therapeutic approaches targeting metabolism have their advantages in improving the survival of CLL patients. This review may shed novel light on the metabolism of CLL, leading to the development of targeted agents based on the reshaping metabolism of CLL cells.

RPPA-based proteomics recognizes distinct epigenetic signatures in chronic lymphocytic leukemia with clinical consequences

The chronic lymphocytic leukemia (CLL) armamentarium has evolved significantly, with novel therapies that inhibit Bruton Tyrosine Kinase, PI3K delta and/or the BCL2 protein improving outcomes. Still, the clinical course of CLL patients is highly variable and most previously recognized prognostic features lack the capacity to predict response to modern treatments indicating the need for new prognostic markers. In this study, we identified four epigenetically distinct proteomic signatures of a large cohort of CLL and related diseases derived samples (n = 871) using reverse phase protein array technology. These signatures are associated with clinical features including age, cytogenetic abnormalities [trisomy 12, del(13q) and del(17p)], immunoglobulin heavy-chain locus (IGHV) mutational load, ZAP-70 status, Binet and Rai staging as well as with the outcome measures of time to treatment and overall survival. Protein signature membership was identified as predictive marker for overall survival regardless of other clinical features. Among the analyzed epigenetic proteins, EZH2, HDAC6, and loss of H3K27me3 levels were the most independently associated with poor survival. These findings demonstrate that proteomic based epigenetic biomarkers can be used to better classify CLL patients and provide therapeutic guidance.

Bimodal regulation of the PRC2 complex by USP7 underlies tumorigenesis

Although overexpression of EZH2, a catalytic subunit of the polycomb repressive complex 2 (PRC2), is an eminent feature of various cancers, the regulation of its abundance and function remains insufficiently understood. We report here that the PRC2 complex is physically associated with ubiquitin-specific protease USP7 in cancer cells where USP7 acts to deubiquitinate and stabilize EZH2. Interestingly, we found that USP7-catalyzed H2BK120ub1 deubiquitination is a prerequisite for chromatin loading of PRC2 thus H3K27 trimethylation, and this process is not affected by H2AK119 ubiquitination catalyzed by PRC1. Genome-wide analysis of the transcriptional targets of the USP7/PRC2 complex identified a cohort of genes including FOXO1 that are involved in cell growth and proliferation. We demonstrated that the USP7/PRC2 complex drives cancer cell proliferation and tumorigenesis in vitro and in vivo. We showed that the expression of both USP7 and EZH2 elevates during tumor progression, corresponding to a diminished FOXO1 expression, and the level of the expression of USP7 and EZH2 strongly correlates with histological grades and prognosis of tumor patients. These results reveal a dual role for USP7 in the regulation of the abundance and function of EZH2, supporting the pursuit of USP7 as a therapeutic target for cancer intervention.

Loss-of-function mutations in the histone methyltransferase EZH2 promote chemotherapy resistance in AML

Chemotherapy resistance is the main impediment in the treatment of acute myeloid leukaemia (AML). Despite rapid advances, the various mechanisms inducing resistance development remain to be defined in detail. Here we report that loss-of-function mutations (LOF) in the histone methyltransferase EZH2 have the potential to confer resistance against the chemotherapeutic agent cytarabine. We identify seven distinct EZH2 mutations leading to loss of H3K27 trimethylation via multiple mechanisms. Analysis of matched diagnosis and relapse samples reveal a heterogenous regulation of EZH2 and a loss of EZH2 in 50% of patients. We confirm that loss of EZH2 induces resistance against cytarabine in the cell lines HEK293T and K562 as well as in a patient-derived xenograft model. Proteomics and transcriptomics analysis reveal that resistance is conferred by upregulation of multiple direct and indirect EZH2 target genes that are involved in apoptosis evasion, augmentation of proliferation and alteration of transmembrane transporter function. Our data indicate that loss of EZH2 results in upregulation of its target genes, providing the cell with a selective growth advantage, which mediates chemotherapy resistance.

EZH2-activating mutation: no reliable indicator for efficacy of methyltransferase inhibitors

EZH2 gain of function mutations (EZH2^GOFmu) has been implicated in the pathogenesis of B-non-Hodgkin lymphoma. The EZH2-specific inhibitor GSK126 inhibits trimethylation of histone H3K27 and induces target gene expression. However, in 3/4 EZH2 ^GOFmu B-NHL lymphoma cell lines, GSK126 (400 nM) did not induce growth arrest. Only at high doses (10 µM), the inhibitor was effective as antiproliferative agent, comparably in EZH2 ^GOFmu, wild-type, and EZH2-negative cell lines, suggesting that at high concentrations, the antiproliferative effects of GSK126 are off-target effects. In sum, we could not confirm that B-NHL cell lines with EZH2 ^GOFmu show a higher sensitivity to GSK126 than EZH2 wild-type cell lines do. Only 1/4 EZH2 ^GOFmu B-NHL cell lines tested (PFEIFFER) were sensitive to GSK126 (400 nM) inducing growth arrest. If these results can be translated to patients, they raise the question of whether the presence of EZH2 activating mutations alone allows selection for targeted therapy with EZH2 inhibitors.

Inhibition of EZH2 and immune signaling exerts synergistic antitumor effects in chronic lymphocytic leukemia

Microenvironmental stimuli affect EZH2 expression and function in CLL. Combined B-cell signaling and EZH2 inhibition showed synergistic effects on primary CLL cells.

EZH2 upregulates the PI3K/AKT pathway through IGF1R and MYC in clinically aggressive chronic lymphocytic leukaemia

EZH2 is overexpressed in poor-prognostic chronic lymphocytic leukaemia (CLL) cases, acting as an oncogene; however, thus far, the EZH2 target genes in CLL have not been disclosed. In this study, using ChIP-sequencing, we identified EZH2 and H3K27me3 target genes in two prognostic subgroups of CLL with distinct prognosis and outcome, i.e., cases with unmutated (U-CLL, n = 6) or mutated IGHV genes (M-CLL, n = 6). While the majority of oncogenic pathways were equally enriched for EZH2 target genes in both prognostic subgroups, PI3K pathway genes were differentially bound by EZH2 in U-CLL versus M-CLL. The occupancy of EZH2 for selected PI3K pathway target genes was validated in additional CLL samples (n = 16) and CLL cell lines using siRNA-mediated EZH2 downregulation and ChIP assays. Intriguingly, we found that EZH2 directly binds to the IGF1R promoter along with MYC and upregulates IGF1R expression in U-CLL, leading to downstream PI3K activation. By investigating an independent CLL cohort (n = 96), a positive correlation was observed between EZH2 and IGF1R expression with higher levels in U-CLL compared to M-CLL. Accordingly, siRNA-mediated downregulation of either EZH2, MYC or IGF1R and treatment with EZH2 and MYC pharmacological inhibitors in the HG3 CLL cell line induced a significant reduction in PI3K pathway activation. In conclusion, we characterize for the first time EZH2 target genes in CLL revealing a hitherto unknown implication of EZH2 in modulating the PI3K pathway in a non-canonical, PRC2-independent way, with potential therapeutic implications considering that PI3K inhibitors are effective therapeutic agents for CLL.

Overexpression of polycomb repressive complex 2 key components EZH2/SUZ12/EED as an unfavorable prognostic marker in cholangiocarcinoma

BACKGROUND

Cholangiocarcinoma (CCA) is a fatal liver cancer arising from bile duct epithelium. Polycomb repressive complex 2 (PRC2) is a histone methyltransferase enzyme that catalyzes trimethylation of histone H3 on lysine 27, resulting transcriptional gene silencing. The key components of PRC2 are EZH2, SUZ12 and EED, which EZH2 is a catalytic subunit. The defect of individual PRC2 components has been shown to enhance carcinogenesis and cancer progression. The aim of this study was to determine the expression of individual PRC2 components and evaluate its association with clinicopathological data in CCA patients.

METHODS

The expression of PRC2 components including EZH2, SUZ12 and EED was determined by immunohistochemistry in 40 CCA tissue samples.

RESULTS

The expression of EZH2 and SUZ12 in CCA tissue was significantly higher than that in adjacent non-cancerous tissue (P < 0.001). The high cytoplasmic EZH2 expression was significantly associated with short overall survival in CCA (P = 0.030). Interestingly, a combined high nuclear and cytoplasmic expression of EZH2 was found to be a worse prognostic marker for overall survival (P = 0.015). Moreover, combined high expression of EZH2 and SUZ12/EED was also associated with short overall survival (P < 0.05).

CONCLUSIONS

Our findings suggest that overexpression of the PRC2 key components especially EZH2 in both nucleus and cytoplasm can be potentially used as a prognostic marker for CCA.

EZH2 is upregulated in the proliferation centers of CLL/SLL lymph nodes

Lymph node involvement of chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL) is characterised by the diffuse infiltration of small neoplastic lymphocytes, which is accompanied by the presence of proliferation centres (PCs) comprising prolymphocytes and paraimmunoblasts. There is increasing evidence of accumulation of various molecular alterations in the tumour cells of PCs, which may explain why extended PCs are related to a less favourable prognosis. To further characterize PCs, we compared the expression level of EZH2 protein, the overexpression of which has recently been recognized as poor prognostic factor in CLL/SLL, in the PCs and the intervening small cell areas in lymph nodes of 15 patients with CLL/SLL. We also investigated the mutational profile of EZH2 and the expression of its upstream regulators c-Myc, E2F1, pRB and miR-26a. Our results showed a significantly increased expression of EZH2 in the PCs. No EZH2 mutations were detected, however, overexpression of c-Myc, E2F1 and pRb proteins as well as reduced expression of the tumor suppressor miR-26a were demonstrated in the PCs. In summary our findings indicate that EZH2 pathway is significantly upregulated in the PCs of CLL/SLL lymph nodes, providing further evidence for the distinguished biological features of the PCs.

Efficacy of extracts of Celastrus orbiculatus in suppressing migration and invasion by inhibiting the EZH2/ROCK1 signaling pathway in human nasopharyngeal carcinoma

Celastrus orbiculatus extract (COE) has been used in folk medicine in China for the treatment of a number of diseases. In the laboratory, COE exhibits a variety of anticancer functions, including inhibition of metastasis. However, the underlying molecular anti-metastatic mechanism in nasopharyngeal carcinoma (NPC) cells remains unclear. The aim of the present study was to determine whether the anti-metastatic effect of COE was involved in inhibiting migration and invasion of human NPC cells. In vitro, cell viability and apoptosis of 5-8F cells were analyzed using an MTS assay and flow cytometry, respectively. Invasion and migration of 5-8F cells were analyzed using a Transwell assay. Protein and mRNA expression levels of 5-8F cells were analyzed by western blot analysis and the reverse transcription-quantitative polymerase chain reaction, respectively. COE significantly decreased cell viability in 5-8F cells and inhibited enhancer of zeste homolog 2 (EZH2) and Rho-associated coiled coil-containing protein kinase 1 (ROCK1) expression at the mRNA and protein levels. Furthermore, COE decreased the migration and invasion of 5-8F cells in a dose-dependent manner. The results of the present study suggested that COE prevents migration and invasion by suppressing the EZH2/ROCK1 signaling pathway in NPC cells. On the basis of the results of the present study, COE may be a novel anticancer agent for the treatment of metastasis in NPC.

Aberrant levels of SUV39H1 and SUV39H2 methyltransferase are associated with genomic instability in chronic lymphocytic leukemia

Chromosomal alterations are commonly detected in patients with chronic lymphocytic leukemia (CLL) and impact disease pathogenesis, prognosis, and progression. Telomerase expression (hTERT), its activity and the telomere length are other important predictors of survival and multiple outcomes in CLL. SUV39H and SUV420H enzymes are histone methyltransferases (HMTases) involved in several cellular processes, including regulation of telomere length, heterochromatin organization, and genome stability. Here, we investigated whether SUV39H1, SUV39H2, SUV420H1, SUV420H2, and hTERT are associated with genomic instability of CLL. SUV39H (1/2), SUV420H (1/2), and hTERT expression was determined in 59 CLL samples by real time PCR. In addition, ZAP-70 protein expression was evaluated by Flow Cytometry and patients' karyotype was defined by Cytogenetic Analysis. Low expression of SUV39H1 was associated with the acquisition of altered and complex karyotypes. Conversely, high expression of SUV39H2 correlated with cytogenetic abnormalities in CLL patients. The pattern of karyotypic alterations differed in samples with detectable or undetectable hTERT expression. Furthermore, hTERT expression in CLL showed a correlation with transcript levels of SUV39H2, which, in part, can explain the association between SUV39H2 expression and cytogenetic abnormalities. Moreover, SUV39H1 correlated with SUV420H1 expression while SUV420H2 was associated with all other investigated HMTases. Our data show that the differential expression of SUV39H1 and SUV39H2 is associated with genomic instability and that the modulation of these HMTases can be an attractive approach to prevent CLL evolution. Environ. Mol. Mutagen. 58:654-661, 2017. © 2017 Wiley Periodicals, Inc.

EZH2 overexpression in primary gastrointestinal diffuse large B-cell lymphoma and its association with the clinicopathological features

Gastrointestinal diffuse large B-cell lymphoma (GI DLBCL) is the most common gastrointestinal lymphoma. Enhancer of zeste homolog 2 (EZH2) has been implicated in the pathogenesis of several cancers. However, EZH2 has not been studied in GI DLBCL. Thus, we investigated EZH2 expression and EZH2 Y641 mutation in 100 GI DLBCL specimens by immunohistochemistry and sequencing. In addition, trimethylated H3K27 (H3K27me3), BCL2, c-MYC, and Ki-67 expression and Helicobacter pylori infection were detected, and BCL2 and c-MYC gene translocation was assessed. EZH2 was overexpressed in 50% of cases. EZH2 overexpression was significantly associated with higher stage (P = .014), higher International Prognostic Index score (P = .003), reduced overall survival rate (P = .030), and H3K27me3 (P = .001) and c-MYC expression (P = .008). We detected EZH2 mutations in 1 of 33 (3.0%) DLBCLs with a germinal center immunophenotype. The frequency of EZH2 Y641 mutation in GI DLBCL was significantly lower than that in patients with DLBCL without gastrointestinal features (P = .022). BCL2 and c-MYC translocation was detected in 6.5% and 5.1% of cases, respectively. BCL2 translocation was detected exclusively in the germinal center B-cell-like subtype. Chronic gastroenteritis was present in all cases, and 36.4% of gastric DLBCL cases had H pylori infection. The data indicate that primary GI DLBCL is closely related with chronic inflammation and has a low frequency of molecular abnormality, and EZH2 overexpression is significantly associated with inferior outcome in patients with primary GI DLBCL; evaluating EZH2 expression has therapeutic implications.

Aberrant histone modification in CD19+ B cells of patients with chronic lymphocytic leukemia

The aim of this study was to detect the alterations in histone methylation and acetylation in patients with chronic lymphocytic leukemia (CLL). Global histone H3/H4 acetylation and H3K4/H3K9 methylation were detected by the EpiQuik™ global histone H3/H4 acetylation and H3K4/H3K9 methylation assay kits. The mRNA expression of selected chromatin modifier genes was measured by real-time polymerase chain reaction (RT-PCR). Our results found that the global histone H3/H4 hypoacetylation in the CD19⁺ B cells of patients with CLL (P=0.028 and P=0.03, respectively) and the global histone H3K9 methylation in patients with CLL were significantly increased compared with controls (P=0.02), while there was no significant difference in the global histone H3K4 methylation between the two groups. The level of SIRT1 and EZH2 mRNA expression was upregulated in patients with CLL (P=0.03 and P=0.02, respectively), which increased significantly with progression from Binet stage A to stage C (P=0.015 and P=0.01, respectively) and Rai good to high risk stage (P=0.007 and P=0.008, respectively). The level of HDAC1 and HDAC7 mRNA expression was significantly increased (P=0.02 and P=0.008, respectively) and HDAC2 and P300 mRNA expression was reduced in patients with CLL (P=0.002 and P=0.001, respectively). In conclusion, it is observed that the aberrant histone modification plays an important role in the pathogenesis of CLL.

EZH2 in normal hematopoiesis and hematological malignancies

Enhancer of zeste homolog 2 (EZH2), the catalytic subunit of the Polycomb repressive complex 2, inhibits gene expression through methylation on lysine 27 of histone H3. EZH2 regulates normal hematopoietic stem cell self-renewal and differentiation. EZH2 also controls normal B cell differentiation. EZH2 deregulation has been described in many cancer types including hematological malignancies. Specific small molecules have been recently developed to exploit the oncogenic addiction of tumor cells to EZH2. Their therapeutic potential is currently under evaluation. This review summarizes the roles of EZH2 in normal and pathologic hematological processes and recent advances in the development of EZH2 inhibitors for the personalized treatment of patients with hematological malignancies.

H3K27 Methylation: A Focal Point of Epigenetic Deregulation in Cancer

Epigenetics, the modification of chromatin without changing the DNA sequence itself, determines whether a gene is expressed, and how much of a gene is expressed. Methylation of lysine 27 on histone 3 (H3K27me), a modification usually associated with gene repression, has established roles in regulating the expression of genes involved in lineage commitment and differentiation. Not surprisingly, alterations in the homeostasis of this critical mark have emerged as a recurrent theme in the pathogenesis of many cancers. Perturbations in the distribution or levels of H3K27me occur due to deregulation at all levels of the process, either by mutation in the histone itself, or changes in the activity of the writers, erasers, or readers of this mark. Additionally, as no single histone mark alone determines the overall transcriptional readiness of a chromatin region, deregulation of other chromatin marks can also have dramatic consequences. Finally, the significance of mutations altering H3K27me is highlighted by the poor clinical outcome of patients whose tumors harbor such lesions. Current therapeutic approaches targeting aberrant H3K27 methylation remain to be proven useful in the clinic. Understanding the biological consequences and gene expression pathways affected by aberrant H3K27 methylation may lead to identification of new therapeutic targets and strategies.

Residual expression of SMYD2 and SMYD3 is associated with the acquisition of complex karyotype in chronic lymphocytic leukemia

SET and MYND domain containing 2 (SMYD2) and the SET and MYND domain containing 3 (SMYD3) are the most studied and well-characterized members of SMYD family. It has been demonstrated that their altered expression is associated with the progression of several solid tumors. Nevertheless, whether these methyltransferases exert any impact in chronic lymphocytic leukemia (CLL) remains unknown. Here, we investigated the gene expression profile of SMYD2 and SMYD3 in 59 samples of CLL and 10 normal B cells. The obtained results were associated with white blood cells (WBC) and platelet counts, ZAP-70 protein expression, and cytogenetic analysis. We found that SMYD2 and SMYD3 are overexpressed in CLL patients and, interestingly, patients with residual expression of both genes presented a high WBC count and complex karyotype. Furthermore, a strong correlation between SMYD2 and SMYD3 gene expression was unveiled. Our data demonstrate the association of a residual expression of SMYD2 and SMYD3 with CLL progression indicators and suggests both genes are regulated by a common transcriptional control in this type of cancer. These results may provide the basis for the development of new therapeutic strategies to prevent CLL progression.

Activation of EZH2 and SUZ12 Regulated by E2F1 Predicts the Disease Progression and Aggressive Characteristics of Bladder Cancer

PURPOSE

Previous study identified E2F1 as a key mediator of non-muscle-invasive bladder cancer (NMIBC) progression. The aim of this study was to identify the E2F1-related genes associated with poor prognosis and aggressive characteristics of bladder cancer.

EXPERIMENTAL DESIGN

Microarray analysis was performed to find E2F1-related genes associated with tumor progression and aggressiveness in the gene expression data from 165 primary patients with bladder cancer. The biologic activity of E2F1-related genes in tumor progression and aggressiveness was confirmed with experimental assays using bladder cancer cells and tumor xenograft assay.

RESULTS

The expression of E2F1 was significantly associated with EZH2 and SUZ12. The overexpression of E2F1, EZH2, and SUZ12 enhanced cancer progression including cell colony formation, migration, and invasiveness. Knockdown of these genes reduced motility, blocked invasion, and decreased tumor size in vivo. E2F1 bound the proximal EZH2 and SUZ12 promoter to activate transcription, suggesting that E2F1 and its downstream effectors, EZH2 and SUZ12, could be important mediators for the cancer progression. In addition, we confirmed an association between these genes and aggressive characteristics. Interestingly, the treatment of anticancer drugs to the cells overexpressing E2F1, EZH2, and SUZ12 induced the expression of CD44, KLF4, OCT4, and ABCG2 known as cancer stem cell (CSC)-related genes.

CONCLUSIONS

The link between E2F1, EZH2, and/or SUZ12 revealed that E2f1 directly regulates transcription of the EZH2 and SUZ12 genes. The signature of E2F1-EZH2-SUZ12 shows a predictive value for prognosis in bladder tumors and the E2F1-EZH2-SUZ12-driven transcriptional events may regulate the cancer aggressiveness and chemo-resistance, which may provide opportunity for development of new treatment modalities.

Epigenetic roots of immunologic disease and new methods for examining chromatin regulatory pathways

The ability to accurately quantitate and experimentally examine epigenetic modifications across the human genome has exploded in the past decade. This has given rise to a wealth of new information concerning the contributions of epigenetic regulatory networks to the pathogenesis of human disease. In particular, immunological disorders have strong developmental roots in chromatin regulatory pathways. In this review, we focus on the epigenetic signatures and new discoveries revealing the epigenetic compositions of specific immunological cancers and autoimmune diseases. We also comment on the conserved epigenetic roots among diverse immunological disorders and suggest inhibition strategies that may be relevant for future treatment. Finally, we highlight emerging experimental tools with the capability to examine the mechanisms of chromatin regulatory enzymes with a high level of temporal control. The knowledge of genetic and epigenetic defects in immunological disease combined with new experimental approaches will elucidate the contribution of individual enzymes in complex epigenetic regulatory networks. This could lead to new diagnostic and therapeutic approaches for some very diverse and difficult to treat human diseases.