EZH2 as a Regulator of CD8+ T Cell Fate and Function

EZH2: The roles in targeted therapy and mechanisms of resistance in breast cancer

Drug resistance presents a formidable challenge in the realm of breast cancer therapy. Accumulating evidence suggests that enhancer of zeste homolog 2 (EZH2), a component of the polycomb repressive complex 2 (PRC2), may serve as a key regulator in controlling drug resistance. EZH2 overexpression has been observed in breast cancer and many other malignancies, showing a strong correlation with poor outcomes. This review aims to summarize the mechanisms by which EZH2 regulates drug resistance, with a specific focus on breast cancer, in order to provide a comprehensive understanding of the underlying molecular processes. Additionally, we will discuss the current strategies and outcomes of targeting EZH2 using both single agents and combination therapies, with the goal of offering improved guidance for the clinical treatment of breast cancer patients who have developed drug resistance.

The roles of epigenetic regulation in graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation (aHSCT) is utilized as a potential curative treatment for various hematologic malignancies. However, graft-versus-host disease (GVHD) post-aHSCT is a severe complication that significantly impacts patients' quality of life and overall survival, becoming a major cause of non-relapse mortality. In recent years, the association between epigenetics and GVHD has garnered increasing attention. Epigenetics focuses on studying mechanisms that affect gene expression without altering DNA sequences, primarily including DNA methylation, histone modifications, non-coding RNAs (ncRNAs) regulation, and RNA modifications. This review summarizes the role of epigenetic regulation in the pathogenesis of GVHD, with a focus on DNA methylation, histone modifications, ncRNA, RNA modifications and their involvement and applications in the occurrence and development of GVHD. It also highlights advancements in relevant diagnostic markers and drugs, aiming to provide new insights for the clinical diagnosis and treatment of GVHD.

EZH2-Myc Hallmark in Oncovirus/Cytomegalovirus Infections and Cytomegalovirus' Resemblance to Oncoviruses

Approximately 15-20% of global cancer cases are attributed to virus infections. Oncoviruses employ various molecular strategies to enhance replication and persistence. Human cytomegalovirus (HCMV), acting as an initiator or promoter, enables immune evasion, supporting tumor growth. HCMV activates pro-oncogenic pathways within infected cells and direct cellular transformation. Thus, HCMV demonstrates characteristics reminiscent of oncoviruses. Cumulative evidence emphasizes the crucial roles of EZH2 and Myc in oncogenesis and stemness. EZH2 and Myc, pivotal regulators of cellular processes, gain significance in the context of oncoviruses and HCMV infections. This axis becomes a central focus for comprehending the mechanisms driving virus-induced oncogenesis. Elevated EZH2 expression is evident in various cancers, making it a prospective target for cancer therapy. On the other hand, Myc, deregulated in over 50% of human cancers, serves as a potent transcription factor governing cellular processes and contributing to tumorigenesis; Myc activates EZH2 expression and induces global gene expression. The Myc/EZH2 axis plays a critical role in promoting tumor growth in oncoviruses. Considering that HCMV has been shown to manipulate the Myc/EZH2 axis, there is emerging evidence suggesting that HCMV could be regarded as a potential oncovirus due to its ability to exploit this critical pathway implicated in tumorigenesis.

Deciphering the role of immune cell composition in epigenetic age acceleration: Insights from cell-type deconvolution applied to human blood epigenetic clocks

Aging is a significant risk factor for various human disorders, and DNA methylation clocks have emerged as powerful tools for estimating biological age and predicting health-related outcomes. Methylation data from blood DNA has been a focus of more recently developed DNA methylation clocks. However, the impact of immune cell composition on epigenetic age acceleration (EAA) remains unclear as only some clocks incorporate partial cell type composition information when analyzing EAA. We investigated associations of 12 immune cell types measured by cell-type deconvolution with EAA predicted by six widely-used DNA methylation clocks in data from >10,000 blood samples. We observed significant associations of immune cell composition with EAA for all six clocks tested. Across the clocks, nine or more of the 12 cell types tested exhibited significant associations with EAA. Higher memory lymphocyte subtype proportions were associated with increased EAA, and naïve lymphocyte subtypes were associated with decreased EAA. To demonstrate the potential confounding of EAA by immune cell composition, we applied EAA in rheumatoid arthritis. Our research maps immune cell type contributions to EAA in human blood and offers opportunities to adjust for immune cell composition in EAA studies to a significantly more granular level. Understanding associations of EAA with immune profiles has implications for the interpretation of epigenetic age and its relevance in aging and disease research. Our detailed map of immune cell type contributions serves as a resource for studies utilizing epigenetic clocks across diverse research fields, including aging-related diseases, precision medicine, and therapeutic interventions.

Epigenetics behind tumor immunology: a mini review

Immunogenic- and immune-therapies have become hot spots in the treatment of cancer. Although promising, these strategies are frequently associated with innate or acquired resistance, calling for combined targeting of immune inhibitory signals. Epigenetic therapy is attracting considerable attention as a combination partner for immune-based therapies due to its role in molding the state and fate of cancer and immune cells in the tumor microenvironment. Here, we describe epigenetic dysregulations in cancer, with a particular focus on those related to innate immune signaling and Type I interferons, and emphasize opportunities and current efforts to translate this knowledge into treatment regimens with improved clinical benefit.

Analysis on EZH2: mechanism identification of related CeRNA and its immunoassay in hepatocellular carcinoma

OBJECTIVE

To screen the possible potential signaling pathways related to enhancer of zeste homolog 2 (EZH2) based on ceRNA mechanism, and to analyze the correlation between E2H2 and depths of various immune cell infiltration depths. The relationship between different immune checkpoints were also analyzed.

METHODS

First, the expression of EZH2 in pan-cancer (18 malignancies) was analyzed with the TCGA database. Hepatocellular carcinoma (HCC) tissues of 374 cases and normal tissues of 50 cases were analyzed in terms of the differential expression, overall survival (OS) and progression-free-survival (PFS). Then, we conducted GO and KEGG enrichment analysis on target gene. We also analyzed mRNA-miRNA and MicroRNA (miRNA)- long non-coding RNA (lncRNA) correlation with starbase databse, so as to determine the potential ceRNA mechanism associated with EZH2. Finally, immunoassay and drug-sensitivity analysis of EZH2 was performed.

RESULTS

Seven potential EZH2-related ceRNA pathways were screened out, namely lncRNA: Small Nucleolar RNA Host Gene 1 (SNHG1), SNHG 3, and SNHG 6-miR-101-3p-EZH2; and lncRNA: Long Intergenic Non-Protein Coding RNA 1978 (LINC01978), SNHG12, Ring Finger Protein 216 Pseudogene 1 (RNF216P1), and Coiled-coil Domain Containing 18 Antisense RNA 1 (CCDC18-AS1)-let-7c-5p-EZH2. Finally, 4 potential EZH2-related ceRNA pathways were identified through qPCR.According to immune correlation analysis, EZH2 may be positively correlated with T cells follicular helper, T cells Cluster of differentiation (CD)4 memory activated, Macrophages M0, and B cells memory (P < 0.05, cof > 0.2); while be negatively correlated with T cells CD4 + memory resting (P < 0.05, cof < -0.2). And EZH2 is positively correlated with Programmed Cell Death 1 (PDCD1) (R = 0.22), CD274 (R = 0.3) and Cytotoxic T-Lymphocyte Associated Protein 4 (CTLA4) (R = 0.23). According to drug sensitivity analysis, patients in the high expression group were more susceptible to the effects of various drugs including Sorafenib, 5-Fluorouracil, Doxorubicin, Etoposide, Paclitaxel, and Vinorelbine than those with low expression.

CONCLUSION

This study revealed seven potential pathways of Enhancer of Zeste Homolog 2 (EZH2)-related ceRNA mechanisms: lncRNA (SNHG3, 6) -Mir-101-3P-ezh2; lncRNA (SNHG12, RNF216P1)-let-7c-5p-EZH2. We also analyzed the immunity and drug sensitivity of EZH2. Our study proves that EZH2 still has great research prospects in HCC.

EZH1/2 dual inhibitors suppress HTLV-1-infected cell proliferation and hyperimmune response in HTLV-1-associated myelopathy

Background

Human T-cell leukemia virus type 1 (HTLV-1) causes HTLV-1-associated myelopathy (HAM), adult T-cell leukemia/lymphoma (ATL), HTLV-1-associated uveitis, and pulmonary diseases. Although both HAM and ATL show proliferation of infected cells, their pathogeneses are quite different. In particular, the pathogenesis of HAM is characterized by hyperimmune responses to HTLV-1-infected cells. Recently, we demonstrated the overexpression of histone methyltransferase EZH2 in ATL cells and the cytotoxic effects of EZH2 inhibitors and EZH1/2 dual inhibitors on these cells. However, these phenomena have never been studied in HAM. Furthermore, what effect these agents have on the hyperimmune response seen in HAM is completely unknown.

Methods

In this study, we investigated histone methyltransferase expression levels in infected cell populations (CD4⁺ and CD4⁺CCR4⁺ cells) from patients with HAM using microarray and RT-qPCR analyses. Next, using an assay system that utilizes the spontaneous proliferation characteristic of peripheral blood mononuclear cells derived from patients with HAM (HAM-PBMCs), we investigated the effects of EZH2 selective inhibitors (GSK126 and tazemetostat) and EZH1/2 dual inhibitors (OR-S1 and valemetostat, also known as DS-3201), particularly on cell proliferation rate, cytokine production, and HTLV-1 proviral load. We also examined the effect of EZH1/2 inhibitors on the proliferation of HTLV-1-infected cell lines (HCT-4 and HCT-5) derived from patients with HAM.

Results

We found elevated expression of EZH2 in CD4⁺ and CD4⁺CCR4⁺ cells from patients with HAM. EZH2 selective inhibitors and EZH1/2 inhibitors significantly inhibited spontaneous proliferation of HAM-PBMC in a concentration-dependent manner. The effect was greater with EZH1/2 inhibitors. EZH1/2 inhibitors also reduced the frequencies of Ki67⁺ CD4⁺ T cells and Ki67⁺ CD8⁺ T cells. Furthermore, they reduced HTLV-1 proviral loads and increased IL-10 levels in culture supernatants but did not alter IFN-γ and TNF-α levels. These agents also caused a concentration-dependent inhibition of the proliferation of HTLV-1-infected cell lines derived from patients with HAM and increased annexin-V(+)7-aminoactinomycin D(-) early apoptotic cells.

Conclusion

This study showed that EZH1/2 inhibitors suppress HTLV-1-infected cell proliferation through apoptosis and the hyperimmune response in HAM. This indicates that EZH1/2 inhibitors may be effective in treating HAM.

Alteration of the tumor microenvironment by pharmacological inhibition of EZH2 in hepatocellular carcinoma

Enhancer of zeste homolog 2 (EZH2), a core component of polycomb repressive component 2 is overexpressed in a variety of cancers and recognized as a therapeutic target molecule. However, EZH2 possesses immunomodulatory functions in the tumor microenvironment (TME). The impact of EZH2 on TME of hepatocellular carcinoma (HCC) using immunocompetent mouse model was evaluated in the present study. UNC1999, an EZH2 inhibitor, impaired growth of the murine HCC cells (H22 cells) and induced apoptosis in a dose-dependent manner. Although UNC1999 significantly inhibited the growth of H22 cells-derived and Hepa1-6 cells-derived tumors in nonobese diabetic/severe combined immunodeficiency mice, its antitumor effect was diminished in allogenic BALB/c and C57BL/6 mice. Flow cytometric analyses of TME cells in BALB/c mice demonstrated a significant decrease in the number of interferon‑γ⁺ CD8⁺ T cells and regulatory T cells and a significant increase in the number of myeloid-derived suppressor cells (MDSCs). Administration of Gr-1 neutralizing antibody concomitant with UNC1999 restored antitumor effect accompanied by an increase in the number of CD8⁺ T cells followed by a decrease in the number of MDSCs. Chemokine antibody array demonstrated an enhanced expression of chemokines responsible for MDSCs recruitment such as C5a, CCL8, and CCL9. In conclusion, the study results demonstrated that EZH2 inhibitor contributed to attenuation of tumor immunity caused by TME arrangement. Combination therapy with EZH2 inhibitors and agents that reduce MDSCs might represent a novel therapeutic strategy for HCC.

The histone demethylase Utx controls CD8+ T-cell-dependent antitumor immunity via epigenetic regulation of the effector function

CD8⁺ T cells play a central role in antitumor immune responses. Epigenetic gene regulation is essential to acquire the effector function of CD8⁺ T cells. However, the role of Utx, a demethylase of histone H3K27, in antitumor immunity remains unclear. In this study, we examined the roles of Utx in effector CD8⁺ T-cell differentiation and the antitumor immune response. In a murine tumor-bearing model, an increased tumor size and decreased survival rate were observed in T-cell-specific Utx KO (Utx KO) mice compared with wild-type (WT) mice. The number of CD8⁺ T cells in tumor-infiltrating lymphocytes (TILs) was significantly decreased in Utx KO mice. We found that the acquisition of effector function was delayed and attenuated in Utx KO CD8⁺ T cells. RNA sequencing revealed that the expression of effector signature genes was decreased in Utx KO effector CD8⁺ T cells, while the expression of naïve or memory signature genes was increased. Furthermore, the expression of Cxcr3, which is required for the migration of effector CD8⁺ T cells to tumor sites, was substantially decreased in Utx KO CD8⁺ T cells. These findings suggest that Utx promotes CD8⁺ T-cell-dependent antitumor immune responses partially through epigenetic regulation of the effector function.

RNA sequencing reveals CircRNA expression profiles in chicken embryo fibroblasts infected with velogenic Newcastle disease virus

Introduction

Newcastle disease virus (NDV) is an important avian pathogen prevalent worldwide; it has an extensive host range and seriously harms the poultry industry. Velogenic NDV strains exhibit high pathogenicity and mortality in chickens. Circular RNAs (circRNAs) are among the most abundant and conserved eukaryotic transcripts. They are part of the innate immunity and antiviral response. However, the relationship between circRNAs and NDV infection is unclear.

Methods

In this study, we used circRNA transcriptome sequencing to analyze the differences in circRNA expression profiles post velogenic NDV infection in chicken embryo fibroblasts (CEFs). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to reveal significant enrichment of differentially expressed (DE) circRNAs. The circRNA- miRNA-mRNA interaction networks were further predicted. Moreover, circ-EZH2 was selected to determine its effect on NDV infection in CEFs.

Results

NDV infection altered circRNA expression profiles in CEFs, and 86 significantly DE circRNAs were identified. GO and KEGG enrichment analyses revealed significant enrichment of DE circRNAs for metabolism-related pathways, such as lysine degradation, glutaminergic synapse, and alanine, aspartic-acid, and glutamic-acid metabolism. The circRNA- miRNA-mRNA interaction networks further demonstrated that CEFs might combat NDV infection by regulating metabolism through circRNA-targeted mRNAs and miRNAs. Furthermore, we verified that circ-EZH2 overexpression and knockdown inhibited and promoted NDV replication, respectively, indicating that circRNAs are involved in NDV replication.

Conclusions

These results demonstrate that CEFs exert antiviral responses by forming circRNAs, offering new insights into the mechanisms underlying NDV-host interactions.

Transient EZH2 suppression by Tazemetostat during in vitro expansion maintains T cell stemness and improves adoptive T cell therapy

The histone methyltransferase enhancer of zeste homolog 2 (EZH2)-mediated epigenetic regulation of T cell differentiation in acute infection has been extensively investigated. However, the role of EZH2 in T cell exhaustion remains under-explored. Here, using in vitro exhaustion models, we demonstrated that transient inhibition of EZH2 in T cells before the phenotypic onset of exhaustion with a clinically approved inhibitor, Tazemetastat, delayed their dysfunctional progression and maintained T cell stemness and polyfunctionality while having no negative impact on cell proliferation. Tazemetestat induced T cell epigenetic reprogramming and increased the expression of the self-renewing T cell transcription factor TCF1 by reducing its promoter H3K27 methylation preferentially in rapidly dividing T cells. In a murine melanoma model, T cells pre-treated with tazemetastat exhibited a superior response to anti-PD-1 blockade therapy after adoptive transfer. Collectively, these data unveil the potential of transient epigenetic reprogramming as a potential intervention to be combined with checkpoint blockade for immune therapy.

EZH2-regulated immune risk score prognostic model predicts outcome of clear cell renal cell carcinoma

Background

The enhancer of zeste homolog 2 (EZH2) plays an important role in the tumor microenvironment (TME), and EZH2 in shaping the epigenetic landscape of CD8⁺ T cell fate and function, with a particular emphasis on cancer. Here, high EZH2 expression always leads to less CD8⁺ T cell infiltration. However, clear cell renal cell carcinoma (ccRCC) is reportedly a "hot" tumor, with contradictory high EZH2 expression. Our goal was to construct a EZH2-regulated immune risk score prognostic model to predict ccRCC outcomes, and provide a prospect of clinical EZH2 inhibitors in fine-tuning T cell responses with immune therapy.

Methods

We downloaded and analyzed The Cancer Genome Atlas (TCGA), Cancer Cell Line Encyclopedia (CCLE), TISIDB database, and WebGestalt for ccRCC patients, EZH2-related tumor-infiltrating lymphocytes and immunomodulators. R packages "limma", "BiocManager", and "preprocessCore", etc. were downloaded to prepare CIBERSORT files, immune cells heatmap, multivariable Cox model and survival analysis. The EZH2-regulated immune risk model's prognostic ability was calculated by receiver operating characteristic (ROC) and area under the curve (AUC) analyses in R studio.

Results

EZH2 was highly expressed and related to poor outcome in ccRCC. However, high-expression EZH2 was not related to a "cool" tumor. Of the 49 immunomodulators significantly regulated by EZH2, forest plot showed 26 immunomodulators signatures independently associated with overall survival. The EZH2-regulated immune-risk score prognostic model was an independent prognostic factor (AUC =0.816), especially combined with clinicopathologic parameters in ccRCC overall survival prediction.

Conclusions

The EZH2-regulated immune-risk score prognostic model was an independent prognostic factor, with good accuracy and predictability, and could provide experimental data to the clinical area.

EZH2: An Accomplice of Gastric Cancer

Gastric cancer is the fifth most common cancer and the third leading cause of cancer deaths worldwide. Understanding the factors influencing the therapeutic effects in gastric cancer patients and the molecular mechanism behind gastric cancer is still facing challenges. In addition to genetic alterations and environmental factors, it has been demonstrated that epigenetic mechanisms can also induce the occurrence and progression of gastric cancer. Enhancer of zeste homolog 2 (EZH2) is the catalytic subunit of the polycomb repressor complex 2 (PRC2), which trimethylates histone 3 at Lys-27 and regulates the expression of downstream target genes through epigenetic mechanisms. It has been found that EZH2 is overexpressed in the stomach, which promotes the progression of gastric cancer through multiple pathways. In addition, targeted inhibition of EZH2 expression can effectively delay the progression of gastric cancer and improve its resistance to chemotherapeutic agents. Given the many effects of EZH2 in gastric cancer, there are no studies to comprehensively describe this mechanism. Therefore, in this review, we first introduce EZH2 and clarify the mechanisms of abnormal expression of EZH2 in cancer. Secondly, we summarize the role of EZH2 in gastric cancer, which includes the association of the EZH2 gene with genetic susceptibility to GC, the correlation of the EZH2 gene with gastric carcinogenesis and invasive metastasis, the resistance to chemotherapeutic drugs of gastric cancer mediated by EZH2 and the high expression of EZH2 leading to poor prognosis of gastric cancer patients. Finally, we also clarify some of the current statuses of drug development regarding targeted inhibition of EZH2/PRC2 activity.

Fundamentals to therapeutics: Epigenetic modulation of CD8+ T Cell exhaustion in the tumor microenvironment

In the setting of chronic antigen exposure in the tumor microenvironment (TME), cytotoxic CD8+ T cells (CTLs) lose their immune surveillance capabilities and ability to clear tumor cells as a result of their differentiation into terminally exhausted CD8+ T cells. Immune checkpoint blockade (ICB) therapies reinvigorate exhausted CD8+ T cells by targeting specific inhibitory receptors, thus promoting their cytolytic activity towards tumor cells. Despite exciting results with ICB therapies, many patients with solid tumors still fail to respond to such therapies and patients who initially respond can develop resistance. Recently, through new sequencing technologies such as the assay for transposase-accessible chromatin with sequencing (ATAC-seq), epigenetics has been appreciated as a contributing factor that enforces T cell differentiation toward exhaustion in the TME. Importantly, specific epigenetic alterations and epigenetic factors have been found to control CD8+ T cell exhaustion phenotypes. In this review, we will explain the background of T cell differentiation and various exhaustion states and discuss how epigenetics play an important role in these processes. Then we will outline specific epigenetic changes and certain epigenetic and transcription factors that are known to contribute to CD8+ T cell exhaustion. We will also discuss the most recent methodologies that are used to study and discover such epigenetic modulations. Finally, we will explain how epigenetic reprogramming is a promising approach that might facilitate the development of novel exhausted T cell-targeting immunotherapies.

Single-Cell Landscape of Mouse Islet Allograft and Syngeneic Graft

Islet transplantation to treat the late stage of type 1 diabetic patient (T1DM) has recently made inspiring success in clinical trials. However, most patients experience a decline in islet graft function in one to three years due to immune rejection. Although the mechanisms of immune cells, including macrophages, dendritic cells (DCs), neutrophils, natural killer cells (NKs), B cells, and T cells, that mediate immune rejection have been investigated, the overall characteristics of immune infiltrates in islet allografts and syngeneic grafts remain unclear. Single-cell RNA sequencing (scRNA-seq) has provided us with new opportunities to study the complexity of the immune microenvironment in islet transplants. In the present study, we used scRNA-seq to comprehensively analyze the immune heterogeneity in the mouse model of islet transplantation. Our data revealed T lymphocytes and myeloid cells as the main immune components of grafts 7 days post-islet transplantation, especially in allografts. Moreover, our results indicated that allogeneic islet cells were transformed into antigen-presenting cell-like cells with highly expressed MHC class I molecules and genes involved in MHC class I-mediated antigen presentation. This transformation may dramatically facilitate the interaction with cytotoxic CD8⁺ T cells and promote the destruction of islet allografts. Our study provides insight into the transcriptomics and diverse microenvironment of islet grafts and their impacts on immune rejection.

Deep Neural Network Modeling Identifies Biomarkers of Response to Immune-checkpoint Therapy

Immunotherapy has shown significant promise as a treatment for cancer, such as lung cancer and melanoma. However, only 10%–30% of the patients respond to treatment with immune checkpoint blockers (ICBs), underscoring the need for biomarkers to predict response to immunotherapy. Here, we developed DeepGeneX, a computational framework that uses advanced deep neural network modeling and feature elimination to reduce single-cell RNA-seq data on ∼26,000 genes to six of the most important genes (CCR7, SELL, GZMB, WARS, GZMH, and LGALS1), that accurately predict response to immunotherapy. We also discovered that the high LGALS1 and WARS-expressing macrophage population represent a biomarker for ICB therapy nonresponders, suggesting that these macrophages may be a target for improving ICB response. Taken together, DeepGeneX enables biomarker discovery and provides an understanding of the molecular basis for the model’s predictions.

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Predicting biomarkers for immunotherapy response remains a challenge

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DeepGeneX combines neural networks with single-cell RNAseq to predict responders

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LGALS1 and WARS-expressing macrophages in nonresponders impact T cell activation

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DeepGeneX enables biomarker discovery and elucidates underlying molecular mechanism

The long and short non-coding RNAs modulating EZH2 signaling in cancer

Non-coding RNAs (ncRNAs) are a large family of RNA molecules with no capability in encoding proteins. However, they participate in developmental and biological processes and their abnormal expression affects cancer progression. These RNA molecules can function as upstream mediators of different signaling pathways and enhancer of zeste homolog 2 (EZH2) is among them. Briefly, EZH2 belongs to PRCs family and can exert functional roles in cells due to its methyltransferase activity. EZH2 affects gene expression via inducing H3K27me3. In the present review, our aim is to provide a mechanistic discussion of ncRNAs role in regulating EZH2 expression in different cancers. MiRNAs can dually induce/inhibit EZH2 in cancer cells to affect downstream targets such as Wnt, STAT3 and EMT. Furthermore, miRNAs can regulate therapy response of cancer cells via affecting EZH2 signaling. It is noteworthy that EZH2 can reduce miRNA expression by binding to promoter and exerting its methyltransferase activity. Small-interfering RNA (siRNA) and short-hairpin RNA (shRNA) are synthetic, short ncRNAs capable of reducing EZH2 expression and suppressing cancer progression. LncRNAs mainly regulate EZH2 expression via targeting miRNAs. Furthermore, lncRNAs induce EZH2 by modulating miRNA expression. Circular RNAs (CircRNAs), like lncRNAs, affect EZH2 expression via targeting miRNAs. These areas are discussed in the present review with a focus on molecular pathways leading to clinical translation.

EZH2, a prominent orchestrator of genetic and epigenetic regulation of solid tumor microenvironment and immunotherapy

Immune checkpoint blockade (ICB) is regarded as a promising strategy for cancer therapy. The histone methyltransferase, Enhancer of Zeste Homolog 2 (EZH2), has been implicated in the carcinogenesis of numerous solid tumors. However, the underlying mechanism of EZH2 in cancer immunotherapeutic resistance remains unknown. EZH2 orchestrates the regulation of the innate and adaptive immune systems of the tumor microenvironment (TME). Profound epigenetic and transcriptomic changes induced by EZH2 in tumor cells and immune cells mobilize the elements of the TME, leading to immune-suppressive activity of solid tumors. In this review, we summarized the dynamic functions of EZH2 on the different components of the TME, including tumor cells, T cells, macrophages, natural killer cells, myeloid-derived suppressor cells, dendritic cells, fibroblasts, and mesenchymal stem cells. Several ongoing anti-tumor clinical trials using EZH2 inhibitors have also been included as translational perspectives. In conclusion, based combinational therapy to enable ICB could offer a survival benefit in patients with cancer.

Nicotinamide Inhibits T Cell Exhaustion and Increases Differentiation of CD8 Effector T Cells

One of the limitations of immunotherapy is the development of a state referred to as T cell exhaustion (TEx) whereby T cells express inhibitory receptors (IRs) and lose production of effectors involved in killing of their targets. In the present studies we have used the repeated stimulation model with anti CD3 and anti CD28 to understand the factors involved in TEx development and treatments that may reduce changes of TEx. The results show that addition of nicotinamide (NAM) involved in energy supply to cells prevented the development of inhibitory receptors (IRs). This was particularly evident for the IRs CD39, TIM3, and to a lesser extent LAG3 and PD1 expression. NAM also prevented the inhibition of IL-2 and TNFα expression in TEx and induced differentiation of CD4+ and CD8 T cells to effector memory and terminal effector T cells. The present results showed that effects of NAM were linked to regulation of reactive oxygen species (ROS) consistent with previous studies implicating ROS in upregulation of TOX transcription factors that induce TEx. These effects of NAM in reducing changes of TEx and in increasing the differentiation of T cells to effector states appears to have important implications for the use of NAM supplements in immunotherapy against cancers and viral infections and require further exploration in vivo.

Regulation of antitumor immunity by inflammation-induced epigenetic alterations

Chronic inflammation promotes tumor development, progression, and metastatic dissemination and causes treatment resistance. The accumulation of genetic alterations and loss of normal cellular regulatory processes are not only associated with cancer growth and progression but also result in the expression of tumor-specific and tumor-associated antigens that may activate antitumor immunity. This antagonism between inflammation and immunity and the ability of cancer cells to avoid immune detection affect the course of cancer development and treatment outcomes. While inflammation, particularly acute inflammation, supports T-cell priming, activation, and infiltration into infected tissues, chronic inflammation is mostly immunosuppressive. However, the main mechanisms that dictate the outcome of the inflammation-immunity interplay are not well understood. Recent data suggest that inflammation triggers epigenetic alterations in cancer cells and components of the tumor microenvironment. These alterations can affect and modulate numerous aspects of cancer development, including tumor growth, the metabolic state, metastatic spread, immune escape, and immunosuppressive or immunosupportive leukocyte generation. In this review, we discuss the role of inflammation in initiating epigenetic alterations in immune cells, cancer-associated fibroblasts, and cancer cells and suggest how and when epigenetic interventions can be combined with immunotherapies to improve therapeutic outcomes.

Identification of the Immune Cell Infiltration Landscape in Hepatocellular Carcinoma to Predict Prognosis and Guide Immunotherapy

Background: Globally, hepatocellular carcinoma (HCC) is the sixth most frequent malignancy with a high incidence and a poor prognosis. Immune cell infiltration (ICI) underlies both the carcinogenesis and immunogenicity of tumors. However, a comprehensive classification system based on the immune features for HCC remains unknown.

Methods: The HCC dataset from The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) cohorts was used in this study. The ICI patterns of 571 patients were characterized using two algorithms: the patterns were determined based on the ICI using the ConsensusClusterPlus package, and principal component analysis (PCA) established the ICI scores. Differences in the immune landscape, biological function, and somatic mutations across ICI scores were evaluated and compared, followed by a predictive efficacy evaluation of ICI scores for immunotherapy by the two algorithms and validation using an external immunotherapy cohort.

Results: Based on the ICI profile of the HCC patients, three ICI patterns were identified, including three subtypes having different immunological features. Individual ICI scores were determined; the high ICI score subtype was characterized by enhanced activation of immune-related signaling pathways and a significantly high tumor mutation burden (TMB); concomitantly, diminished immunocompetence and enrichment of pathways associated with cell cycle and RNA degradation were found in the low ICI score subtype. Taken together, our results contribute to a better understanding of an active tumor and plausible reasons for its poor prognosis.

Conclusion: The present study reveals that ICI scores may serve as valid prognostic biomarkers for immunotherapy in HCC.

RKIP Pleiotropic Activities in Cancer and Inflammatory Diseases: Role in Immunity

Simple Summary

The human body consists of tissues and organs formed by cells. In each cell there is a switch that allows the cell to divide or not. In contrast, cancer cells have their switch on which allow them to divide and invade other sites leading to death. Over two decades ago, Doctor Kam Yeung, University of Toledo, Ohio, has identified a factor (RKIP) that is responsible for the on/off switch which functions normally in healthy tissues but is inactive or absent in cancers. Since this early discovery, many additional properties have been ascribed to RKIP including its role in inhibiting cancer metastasis and resistance to therapeutics and its role in modulating the normal immune response. This review describes all of the above functions of RKIP and suggesting therapeutics to induce RKIP in cancers to inhibit their growth and metastases as well as inhibit its activity to treat non-cancerous inflammatory diseases.

Abstract

Several gene products play pivotal roles in the induction of inflammation and the progression of cancer. The Raf kinase inhibitory protein (RKIP) is a cytosolic protein that exerts pleiotropic activities in such conditions, and thus regulates oncogenesis and immune-mediated diseases through its deregulation. Herein, we review the general properties of RKIP, including its: (i) molecular structure; (ii) involvement in various cell signaling pathways (i.e., inhibition of the Raf/MEK/ERK pathway; the NF-kB pathway; GRK-2 or the STAT-3 pathway; as well as regulation of the GSK3Beta signaling; and the spindle checkpoints); (iii) regulation of RKIP expression; (iv) expression’s effects on oncogenesis; (v) role in the regulation of the immune system to diseases (i.e., RKIP regulation of T cell functions; the secretion of cytokines and immune mediators, apoptosis, immune check point inhibitors and RKIP involvement in inflammatory diseases); and (vi) bioinformatic analysis between normal and malignant tissues, as well as across various immune-related cells. Overall, the regulation of RKIP in different cancers and inflammatory diseases suggest that it can be used as a potential therapeutic target in the treatment of these diseases.

New Insights into Epigenetic Regulation of T Cell Differentiation

Immature CD4⁻ CD8⁻ thymocytes progress through several developmental steps in the thymus, ultimately emerging as mature CD4⁺ (helper) or CD8⁺ (cytotoxic) T cells. Activation of naïve CD4⁺ and CD8⁺ T cells in the presence of specific cytokines results in the induction of transcriptional programs that result in their differentiation into effector or memory cells and in the case of CD4⁺ T cells, the adoption of distinct T-helper fates. Previous studies have shown that histone modification and DNA methylation play important roles in each of these events. More recently, the roles of specific epigenetic regulators in T cell differentiation have been clarified. The identification of the epigenetic modifications and modifiers that control mature T cell differentiation and specification has also provided further insights into how dysregulation of these processes can lead to cancer or autoimmune diseases. In this review, we summarize recent findings that have provided new insights into epigenetic regulation of T cell differentiation in both mice and humans.

Immune signature-based hepatocellular carcinoma subtypes may provide novel insights into therapy and prognosis predictions

Background

Hepatocellular carcinoma (HCC) has a poor prognosis and has become the sixth most common malignancy worldwide due to its high incidence. Advanced approaches to therapy, including immunotherapeutic strategies, have played crucial roles in decreasing recurrence rates and improving clinical outcomes. The HCC microenvironment is important for both tumour carcinogenesis and immunogenicity, but a classification system based on immune signatures has not yet been comprehensively described.

Methods

HCC datasets from The Cancer Genome Atlas (TCGA), the Gene Expression Omnibus (GEO), and the International Cancer Genome Consortium (ICGC) were used in this study. Gene set enrichment analysis (GSEA) and the ConsensusClusterPlus algorithm were used for clustering assessments. We scored immune cell infiltration and used linear discriminant analysis (LDA) to improve HCC classification accuracy. Pearson's correlation analyses were performed to assess relationships between immune signature indices and immunotherapies. In addition, weighted gene co-expression network analysis (WGCNA) was applied to identify candidate modules closely associated with immune signature indices.

Results

Based on 152 immune signatures from HCC samples, we identified four distinct immune subtypes (IS1, IS2, IS3, and IS4). Subtypes IS1 and IS4 had more favourable prognoses than subtypes IS2 and IS3. These four subtypes also had different immune system characteristics. The IS1 subtype had the highest scores for IFNγ, cytolysis, angiogenesis, and immune cell infiltration among all subtypes. We also identified 11 potential genes, namely, TSPAN15, TSPO, METTL9, CD276, TP53I11, SPINT1, TSPO, TRABD2B, WARS2, C9ORF116, and LBH, that may represent potential immunological biomarkers for HCC. Furthermore, real-time PCR revealed that SPINT1, CD276, TSPO, TSPAN15, METTL9, and WARS2 expression was increased in HCC cells.

Conclusions

The present gene-based immune signature classification and indexing may provide novel perspectives for both HCC immunotherapy management and prognosis prediction.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-021-02033-4.

The role of tazemetostat in relapsed/refractory follicular lymphoma

Large strides have been made in the treatment of follicular lymphoma (FL) over the last few years. Although the majority of patients respond to upfront therapy, many experience disease progression with a progressive shortening of subsequent treatment free intervals. New treatment options are therefore crucial for such patients. Tazemetostat is a first-in-class, selective, oral inhibitor of enhancer of zester homolog 2 (EZH2), a histone methyltransferase that is mutated in about a quarter of FL cases. Tazemetostat was recently approved for the treatment of patients with relapsed FL after 2 or more prior lines of therapy in the presence of an EZH2 mutation and for those without any other available therapeutic option, independently of EZH2 mutation status. In this review, we will summarize the background and key data that led to the development of tazemetostat, and, ultimately, to its approval for this indication.