DZNep-mediated apoptosis in B-cell lymphoma is independent of the lymphoma type, EZH2 mutation status and MYC, BCL2 or BCL6 translocations

Epigenetic targets in B- and T-cell lymphomas: latest developments

Non-Hodgkin's lymphomas (NHLs) comprise a diverse group of diseases, either of mature B-cell or of T-cell derivation, characterized by heterogeneous molecular features and clinical manifestations. While most of the patients are responsive to standard chemotherapy, immunotherapy, radiation and/or stem cell transplantation, relapsed and/or refractory cases still have a dismal outcome. Deep sequencing analysis have pointed out that epigenetic dysregulations, including mutations in epigenetic enzymes, such as chromatin modifiers and DNA methyltransferases (DNMTs), are prevalent in both B- cell and T-cell lymphomas. Accordingly, over the past decade, a large number of epigenetic-modifying agents have been developed and introduced into the clinical management of these entities, and a few specific inhibitors have already been approved for clinical use. Here we summarize the main epigenetic alterations described in B- and T-NHL, that further supported the clinical development of a selected set of epidrugs in determined diseases, including inhibitors of DNMTs, histone deacetylases (HDACs), and extra-terminal domain proteins (bromodomain and extra-terminal motif; BETs). Finally, we highlight the most promising future directions of research in this area, explaining how bioinformatics approaches can help to identify new epigenetic targets in B- and T-cell lymphoid neoplasms.

Rational Targets of Therapy in Extranodal NK/T-Cell Lymphoma

Extranodal NK/T-cell lymphoma (ENKTL) is an aggressive extranodal non-Hodgkin lymphoma (NHL) with poor outcomes, particularly in advanced-stage and relapsed/refractory disease. Emerging research on molecular drivers of ENKTL lymphomagenesis by next-generation and whole genome sequencing has revealed diverse genomic mutations in multiple signaling pathways, with the identification of multiple putative targets for novel therapeutic agents. In this review, we summarize the biological underpinnings of newly-understood therapeutic targets in ENKTL with a focus on translational implications, including epigenetic and histone regulatory aberrations, activation of cell proliferation signaling pathways, suppression of apoptosis and tumor suppressor genes, changes in the tumor microenvironment, and EBV-mediated oncogenesis. In addition, we highlight prognostic and predictive biomarkers which may enable a personalized medicine approach toward ENKTL therapy.

The future clinical implications of trained immunity

INTRODUCTION

Trained Immunity (TI) refers to the long-term modulation of the innate immune response, based on previous interactions with microbes, microbial ligands or endogenous substances. Through metabolic and epigenetic reprogramming, monocytes, macrophages and neutrophils develop an enhanced capacity to mount innate immune responses to subsequent stimuli and this is persistent due to alterations at the myeloid progenitor compartment.

AREAS COVERED

The purpose of this article is to review the current understanding of the TI process and discuss about its potential clinical implications in the near future. We address the evidence of TI involvement in various diseases, the currently developed new therapy, and discuss how TI may lead to new clinical tools to improve existing standards of care.

EXPERT OPINION

The state of art in this domain has made considerable progress, linking TI-related mechanisms in multiple immune-mediated pathologies, starting with infections to autoimmune disorders and cancers. As a relatively new area of immunology, it has seen fast progress with many of its applications ready to be investigated in clinical settings.

Targeting EZH2-mediated methylation of histone 3 inhibits proliferation of pediatric acute monocytic leukemia cells in vitro

Enhancer of zeste homolog 2 (EZH2) is a histone methyltransferase and a catalytic subunit of the polycomb repressive complex 2 (PRC2) that catalyzes the mono-, di-, and tri-methylation of histone H3 at Lys 27 (H3K27me3) to facilitate chromatin-remodeling and gene-silencing functions. Previous reports showed a significant association of EZH2 aberrations in pediatric cancers, such as soft tissue sarcomas and glioblastoma. Recent reports in human subjects and animal models have also suggested a central role of EZH2 in the induction and progression of acute myeloid leukemia. In this study, we aimed to investigate the molecular status of EZH in cell lines derived from distinct pediatric leukemia to assess the efficacy of targeting EZH2 to suppress cancer cell survival and proliferation. Our results showed that EZH2 protein is overexpressed in the pediatric monocytic cell-line THP-1, but not in other leukemia-derived cell lines MV4;11 and SEM. Screening a panel of methyltransferase inhibitors revealed that three inhibitors; GSK126, UNC1999 and EPZ-5687 are the most potent inhibitors that suppressed EZH2 activity selectively on lysine 27 which resulted in increased apoptosis and inhibition of AKT and ERK protein phosphorylation in THP-1 cells. Our data demonstrated a significant increase in apoptosis in cells treated with drug combination (EZH2i and selinexor) compared to EZH2i inhibitors alone. Taken together, our data provide initial evidence that targeting EZH2 is a promising therapeutic strategy for the treatment of subtypes of pediatric AML. Also, combining EZH2 inhibitors with selinexor may increase the treatment efficacy in these patients.

EZH2-mediated lncRNA ABHD11-AS1 promoter regulates the progression of ovarian cancer by targeting miR-133a-3p

Long-chain noncoding RNAs (lncRNAs) are involved in a wide range of biological and pathological processes in ovarian cancer. The purpose of this study was to investigate the effects of EZH2-mediated ABHD11-AS1 promoter on the pathogenesis of ovarian cancer. The expression levels of EZH2, ABHD11-AS1 and miR-133a-3p were examined in ovarian cancer tissues using reverse transcription-quantitative PCR. Cell proliferation was evaluated using cell counting kit 8 assay, and cell invasion/migration was determined using a Transwell assay. Cell apoptosis was evaluated using flow cytometry. Dual luciferase assay was performed to confirm the interaction between ABHD11-AS1 and miR-133a-3p. The binding site of H3K27me3 on ABHD11-AS1 promoter was confirmed by ChIP. The expression of ABHD11-AS1 was significantly upregulated in ovarian cancer samples, and its levels were closely associated with lymph node metastasis, tumor stage and 3-year survival rate. Furthermore, interference of ABHD11-AS1 suppressed the proliferation, migration and invasion of ovarian cancer cells, while cell apoptosis was promoted. Additionally, miR-133a-3p could be a novel target of ABHD11-AS1, and EZH2-mediated H3K27me3 protein might bind to ABHD11-AS1 promoter directly. Moreover, rescue experiments indicated that the effects caused by ABHD11-AS1 knockdown on the malignant characteristics of ovarian cancer cells were notably enhanced by miR-133a-3p mimics, whereas the influences on cell growth and metastasis induced by overexpressed ABHD11-AS1 were abrogated by the restoration of miR-133a-3p expression. In summary, EZH2-mediated enrichment of H3K27me3 on ABHD11-AS1 promoter could regulate the progression of ovarian cancer via miR-133a-3p. Therefore, EZH2/ABHD11-AS1/miR-133a-3p axis might be a putative candidate for targeted treatment of ovarian cancer.

LINC00152 upregulates ZEB1 expression and enhances epithelial-mesenchymal transition and oxaliplatin resistance in esophageal cancer by interacting with EZH2

BACKGROUND

Expression of the long non-coding mRNA LINC00152 has been reported to correlate with cancer cell resistance to oxaliplatin (L-OHP). However, little is known regarding the molecular mechanism of LINC00152 in esophageal cancer (EC). Hence, we intended to characterize the role of LINC00152 in EC, with a special focus on epithelial-mesenchymal transition (EMT) and L-OHP resistance.

METHODS

We collected EC tissues and identified EC cell lines with higher L-OHP resistance, and then characterized expression patterns of LINC00152, Zeste Homologue 2 (EZH2), Zinc finger e-box binding homeobox (ZEB1) and EMT-related genes using RT-qPCR and Western blot analysis. Furthermore, their functional significance was identified by gain and loss-of-function experiments. The relationship among LINC00152, EZH2 and ZEB1 was examined using RIP, RNA pull-down and ChIP assays. Additionally, resistance of EC cells to L-OHP was reflected by CCK-8 assay to detect cell viability. Animal experiments were also conducted to detect the effects of the LINC00152/EZH2/ZEB1 on EMT and L-OHP resistance.

RESULTS

LINC00152, EZH2 and ZEB1 were highly expressed in EC tissues and Kyse-150/TE-1 cells. As revealed by assays in vitro and in vivo, LINC00152 positively regulated ZEB1 expression through interaction with EZH2 to enhance EMT and L-OHP resistance in EC cells. In contrast, silencing of LINC00152 contributed to attenuated EMT and drug resistance of EC cells to L-OHP.

CONCLUSIONS

Our study demonstrates that LINC00152/EZH2/ZEB1 axis can regulate EMT and resistance of EC cells to L-OHP, thus presenting a potential therapeutic target for EC treatment.

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.

Acquired resistance to DZNep-mediated apoptosis is associated with copy number gains of AHCY in a B-cell lymphoma model

BACKGROUND

Enhancer of zeste homolog 2 (EZH2) is considered an important driver of tumor development and progression by its histone modifying capabilities. Inhibition of EZH2 activity is thought to be a potent treatment option for eligible cancer patients with an aberrant EZH2 expression profile, thus the indirect EZH2 inhibitor 3-Deazaneplanocin A (DZNep) is currently under evaluation for its clinical utility. Although DZNep blocks proliferation and induces apoptosis in different tumor types including lymphomas, acquired resistance to DZNep may limit its clinical application.

METHODS

To investigate possible mechanisms of acquired DZNep resistance in B-cell lymphomas, we generated a DZNep-resistant clone from a previously DZNep-sensitive B-cell lymphoma cell line by long-term treatment with increasing concentrations of DZNep (ranging from 200 to 2000 nM) and compared the molecular profiles of resistant and wild-type clones. This comparison was done using molecular techniques such as flow cytometry, copy number variation assay (OncoScan and TaqMan assays), fluorescence in situ hybridization, Western blot, immunohistochemistry and metabolomics analysis.

RESULTS

Whole exome sequencing did not indicate the acquisition of biologically meaningful single nucleotide variants. Analysis of copy number alterations, however, demonstrated among other acquired imbalances an amplification (about 30 times) of the S-adenosyl-L-homocysteine hydrolase (AHCY) gene in the resistant clone. AHCY is a direct target of DZNep and is critically involved in the biological methylation process, where it catalyzes the reversible hydrolysis of S-adenosyl-L-homocysteine to L-homocysteine and adenosine. The amplification of the AHCY gene is paralleled by strong overexpression of AHCY at both the transcriptional and protein level, and persists upon culturing the resistant clone in a DZNep-free medium.

CONCLUSIONS

This study reveals one possible molecular mechanism how B-cell lymphomas can acquire resistance to DZNep, and proposes AHCY as a potential biomarker for investigation during the administration of EZH2-targeted therapy with DZNep.