Ezh2 Acts as a Tumor Suppressor in Kras-driven Lung Adenocarcinoma

EZH2: An analysis of a potential new tumor marker in high-risk localization of cutaneous squamous cell carcinomas

Background

Enhancer of zeste homolog 2 (EZH2) is a transcriptional enzyme implicated in tumor development and is often correlated to poor patient outcomes in various malignancies. The study evaluated various methods for EZH2 expression in lip and ear squamous cell carcinomas (LSCC, ESCC) by matching patients with and without lymph node metastasis (LNM) and further analysis of clinical outcome parameters. EZH2 inhibition therapy has shown promising results in multiple cancer entities, with ongoing research exploring its potential in other malignancies. This approach may also be applicable to high-risk LSCC and ESCC.

Methods

A total of 122 patients who had been surgically treated for LSCC and ESCC were selected to form LNM-positive and LNM-negative matched pairs. EZH2 expression has been examined after immunostaining of the tumor tissue with EZH2-antibodies and quantified as extent, intensity, and score. Pursuing the clinical benefit, we analyzed three different EZH2-score approaches to determine aberrations in EZH2 expression.

Results

While the overall EZH2 extent did not correlate with clinical outcome, the EZH2-intensity and -score was lower in patients who developed a local relapse or distant metastasis (DM). High EZH2-scores correlated with increasing grading, pN-, and American Joint Committee on Cancer-stage. Overall, the carcinoma tissue samples showed a high expression of EZH2 (mean expression > 60%).

Conclusion

The hypothesis of the predictive prognostic contribution of EZH2 in clinical decisions regarding the occurrence of LNM was not substantiated by our data. Nevertheless, the elevated expression of EZH2 we have observed in our findings could be utilized as a pretherapeutic assessment prior to targeted therapies with tazemetostat. Subsequent research should substantiate this hypothesis.

Regulation of histone H3K27 methylation in inflammation and cancer

Inflammation is a multifaceted defense mechanism of the immune system against infection. Chronic inflammation is intricately linked to all stages of tumorigenesis and is therefore associated with an elevated risk of developing serious cancers. Epigenetic mechanisms have the capacity to trigger inflammation as well as facilitate tumor development and transformation within an inflammatory context. They achieve this by dynamically modulating the expression of both pro-inflammatory and anti-inflammatory cytokines, which in turn sustains chronic inflammation. The aberrant epigenetic landscape reconfigures the transcriptional programs of inflammatory and oncogenic genes. This reconfiguration is pivotal in dictating the biological functions of both tumor cells and immune cells. Aberrant histone H3 lysine 27 site (H3K27) methylation has been shown to be involved in biological behaviors such as inflammation development, tumor progression, and immune response. The establishment and maintenance of this repressive epigenetic mark is dependent on the involvement of the responsible histone modifying enzymes enhancer of zeste homologue 2 (EZH2), jumonji domain containing 3 (JMJD3) and ubiquitously transcribed tetratricopeptide repeat gene X (UTX) as well as multiple cofactors. In addition, specific pharmacological agents have been shown to modulate H3K27 methylation levels, thereby modulating inflammation and carcinogenesis. This review comprehensively summarises the current characteristics and clinical significance of epigenetic regulation of H3K27 methylation in the context of inflammatory response and tumor progression.

EZH2 directly methylates PARP1 and regulates its activity in cancer

DNA repair dysregulation is a key driver of cancer development. Understanding the molecular mechanisms underlying DNA repair dysregulation in cancer cells is crucial for cancer development and therapies. Here, we report that enhancer of zeste homolog 2 (EZH2) directly methylates poly(adenosine diphosphate-ribose) polymerase-1 (PARP-1), an essential enzyme involved in DNA repair, and regulates its activity. Functionally, EZH2-catalyzed methylation represses PARP1 catalytic activity, down-regulates the recruitment of x-ray repair cross-complementing group-1 to DNA lesions and its associated DNA damage repair; on the other hand, it protects the cells from nicotinamide adenine dinucleotide overconsumption upon DNA damage formation. Meanwhile, EZH2-mediated methylation regulates PARP1 transcriptional and oncogenic activity, at least in part, through impairing PARP1-E2F1 interaction and E2F1 transcription factor activity. EZH2 and PARP1 inhibitors synergistically suppress prostate cancer growth. Collectively, our findings uncover an insight of EZH2 functions in fine-tuning PARP1 activity during DNA damage repair and cancer progression, which provides a rationale for combinational targeting EZH2 and PARP1 in cancer.

Developmental Stage and Cellular Context Determine Oncogenic and Molecular Outcomes of Ezh2 Y641F Mutation in Hematopoiesis

Mutations in the histone methyltransferase EZH2, particularly the Y641 hotspot mutation, have been implicated in hematologic malignancies, yet the effect of timing and cellular context on their oncogenic potential has remained unknown. In this study, we utilized a conditional allele with tissue-specific Cre drivers to investigate the effects of Ezh2 Y641F mutations at various stages of development, with a focus on the hematopoietic system. We found that ubiquitous heterozygous Ezh2 Y641F expression at birth, or conditional expression in hematopoietic or mesenchymal stem cells, led to decreased survival due to hematopoietic defects and bone marrow failure, with no evidence of malignancy. In contrast, Ezh2 Y641F expression in committed B cells drives lymphoma formation, highlighting the lineage-specific oncogenic activity of the mutation. Transcriptomic analysis of B cell progenitors revealed key pathway alterations between Cre models such as altered IL2-Stat5 signaling pathway, differential expression of E2F targets, and altered GTPase pathway expression driven by upregulation of Guanylate Binding Proteins (GBPs) in Mx1-Cre Ezh2 Y641F pro-B cells. We further found that the GBP locus is regulated by Ezh2-mediated H3K27me3, it is associated with poorer survival in Acute Myeloid Leukemia patients and has variable effects on apoptosis in human lymphoma and leukemia cell lines. These findings suggest that the Ezh2 Y641F mutation may alter immune regulatory pathways, cell differentiation and apoptosis, with potential implications for disease progression. Our results highlight the critical role of mutation timing and cellular context in EZH2-driven hematopoietic disease, resulting in distinct downstream changes that shape the oncogenic impact of EZH2.

Stat3-mediated Atg7 expression regulates anti-tumor immunity in mouse melanoma

Epigenetic modifications to DNA and chromatin control oncogenic and tumor-suppressive mechanisms in melanoma. Ezh2, the catalytic component of the Polycomb Repressive Complex 2 (PRC2), which mediates methylation of lysine 27 on histone 3 (H3K27me3), can regulate both melanoma initiation and progression. We previously found that mutant Ezh2Y641F interacts with the immune regulator Stat3 and together they affect anti-tumor immunity. However, given the numerous downstream targets and pathways affected by Ezh2, many mechanisms that determine its oncogenic activity remain largely unexplored. Using genetically engineered mouse models, we further investigated the role of pathways downstream of Ezh2 in melanoma carcinogenesis and identified significant enrichment in several autophagy signatures, along with increased expression of autophagy regulators, such as Atg7. In this study, we investigated the effect of Atg7 on melanoma growth and tumor immunity within the context of a wild-type or Ezh2Y641F epigenetic state. We found that the Atg7 locus is controlled by multiple Ezh2 and Stat3 binding sites, Atg7 expression is dependent on Stat3 expression, and that deletion of Atg7 slows down melanoma cell growth in vivo, but not in vitro. Atg7 deletion also results in increased CD8 + T cells in Ezh2Y641F melanomas and reduced myelosuppressive cell infiltration in the tumor microenvironment, particularly in Ezh2WT melanomas, suggesting a strong immune system contribution in the role of Atg7 in melanoma progression. These findings highlight the complex interplay between genetic mutations, epigenetic regulators, and autophagy in shaping tumor immunity in melanoma.

Stat3-mediated Atg7 expression enhances anti-tumor immunity in melanoma

Epigenetic modifications to DNA and chromatin control oncogenic and tumor suppressive mechanisms in melanoma. EZH2, the catalytic component of the Polycomb repressive complex 2 (PRC2), which mediates methylation of lysine 27 on histone 3 (H3K27me3), can regulate both melanoma initiation and progression. We previously found that mutant Ezh2 Y641F interacts with the immune regulator Stat3 and together they affect anti-tumor immunity. However, given the numerous downstream targets and pathways affected by EZH2, many mechanisms that determine its oncogenic activity remain largely unexplored. Using genetically engineered mouse models we further investigated the role of pathways downstream of EZH2 in melanoma carcinogenesis and identified significant enrichment in several autophagy signatures, along with increased expression of autophagy regulators, such as Atg7. In this study, we investigated the effect of Atg7 on melanoma growth and tumor immunity within the context of an Ezh2 Y641F epigenetic state. We found that expression of Atg7 is largely dependent on Stat3 expression and that deletion of Atg7 slows down melanoma cell growth in vivo, but not in vitro. Atg7 deletion also results in increased CD8+ T cells and reduced myelosuppressive cell infiltration in the tumor microenvironment, suggesting a strong immune system contribution in the role of Atg7 in melanoma progression. These findings highlight the complex interplay between genetic mutations, epigenetic regulators, and autophagy in shaping tumor immunity in melanoma.

EZH2-mediated development of therapeutic resistance in cancer

Enhancer of zeste homolog 2 (EZH2) regulates gene expression and plays a definite role in cell proliferation, apoptosis, and senescence. Overexpression of EZH2 has been found in various human malignancies, including prostate, breast, and ovarian cancers, and is associated with increased metastasis and poor prognosis. EZH2 catalyzes trimethylation of lysine 27 of histone H3 (H3K27me3) as a canonical role in a PRC2-dependent manner. This mechanism silences various tumor suppressor genes through EZH2-mediated histone lysine methyltransferase activity. As a non-canonical role, EZH2 partners with other signaling molecules to undergo post-translational modification to orchestrate its function as a co-activator playing a critical role in cancer progression. Dysregulation of EZH2 has also been associated with therapeutic resistance in cancer cells. Given the role of EZH2 in promoting carcinogenesis and therapy resistance, both canonical and non-canonical EZH2 inhibitors have been used to combat multiple cancer types. Moreover, combining EZH2 inhibitors with other therapeutic modalities have shown to enhance the therapeutic efficacy and overcome potential resistance mechanisms in these cancerous cells. Therefore, targeting EZH2 through canonical and non-canonical modes appears to be a promising therapeutic strategy to enhance efficacy and overcome resistance in multiple cancers.

Tumor-suppressive functions of protein lysine methyltransferases

Protein lysine methyltransferases (PKMTs) play crucial roles in histone and nonhistone modifications, and their dysregulation has been linked to the development and progression of cancer. While the majority of studies have focused on the oncogenic functions of PKMTs, extensive evidence has indicated that these enzymes also play roles in tumor suppression by regulating the stability of p53 and β-catenin, promoting α-tubulin-mediated genomic stability, and regulating the transcription of oncogenes and tumor suppressors. Despite their contradictory roles in tumorigenesis, many PKMTs have been identified as potential therapeutic targets for cancer treatment. However, PKMT inhibitors may have unintended negative effects depending on the specific cancer type and target enzyme. Therefore, this review aims to comprehensively summarize the tumor-suppressive effects of PKMTs and to provide new insights into the development of anticancer drugs targeting PKMTs.

Catalytic domain-dependent and -independent transcriptional activities of the tumour suppressor histone H3K27 demethylase UTX/KDM6A in specific cancer types

The histone H3K27 demethylase, UTX/KDM6A, plays a critical role in the early development of vertebrates, and mutations are frequently found in various cancers. Several studies on developmental and cancer biology have focused on preferential transcriptional regulation by UTX independently of its H3K27 demethylase catalytic activity. Here, we analysed gene expression profiles of wild-type (WT) UTX and a catalytic activity-defective mutant in 786-O and HCT116 cells and confirmed that catalytic activity-dependent and -independent regulation contributes to the expression of most of the target genes. Indeed, the catalytic activity-defective mutant indeed suppressed colony formation similar to the WT in our assay system. However, the expression of several genes was significantly dependent on the catalytic activity of UTX in a cell type-specific manner, which could account for the inherent variation in the transcriptional landscape of various cancer types. The promoter/enhancer regions of the catalytic activity-dependent genes identified here were found to be preferentially modified with H3K4me1 and less with H3K27me3 than those of the independent genes. These findings, combined with previous reports, highlight not only the understanding of determinants for the catalytic activity dependency but also the development and application of pharmaceutical agents targeting the H3K27 or H3K4 modifications.

CUL4B functions as a tumor suppressor in KRAS-driven lung tumors by inhibiting the recruitment of myeloid-derived suppressor cells

Lung cancer is the leading cause of cancer-related death worldwide. KRAS mutations are the most common oncogenic alterations found in lung cancer. Unfortunately, treating KRAS-mutant lung adenocarcinoma (ADC) remains a major oncotherapeutic challenge. Here, we used both autochthonous and transplantable KRAS-mutant tumor models to investigate the role of tumor-derived CUL4B in KRAS-driven lung cancers. We showed that knockout or knockdown of CUL4B promotes lung ADC growth and progression in both models. Mechanistically, CUL4B directly binds to the promoter of Cxcl2 and epigenetically represses its transcription. CUL4B deletion increases the expression of CXCL2, which binds to CXCR2 on myeloid-derived suppressor cells (MDSCs) and promotes their migration to the tumor microenvironment. Targeting of MDSCs significantly delayed the growth of CUL4B knockdown KRAS-mutant tumors. Collectively, our study provides mechanistic insights into the novel tumor suppressor-like functions of CUL4B in regulating KRAS-driven lung tumor development.

Non-canonical functions of EZH2 in cancer

Mutations in chromatin modifying genes frequently occur in many kinds of cancer. Most mechanistic studies focus on their canonical functions, while therapeutic approaches target their enzymatic activity. Recent studies, however, demonstrate that non-canonical functions of chromatin modifiers may be equally important and therapeutically actionable in different types of cancer. One epigenetic regulator that demonstrates such a dual role in cancer is the histone methyltransferase EZH2. EZH2 is a core component of the polycomb repressive complex 2 (PRC2), which plays a crucial role in cell identity, differentiation, proliferation, stemness and plasticity. While much of the regulatory functions and oncogenic activity of EZH2 have been attributed to its canonical, enzymatic activity of methylating lysine 27 on histone 3 (H3K27me3), a repressive chromatin mark, recent studies suggest that non-canonical functions that are independent of H3K27me3 also contribute towards the oncogenic activity of EZH2. Contrary to PRC2's canonical repressive activity, mediated by H3K27me3, outside of the complex EZH2 can directly interact with transcription factors and oncogenes to activate gene expression. A more focused investigation into these non-canonical interactions of EZH2 and other epigenetic/chromatin regulators may uncover new and more effective therapeutic strategies. Here, we summarize major findings on the non-canonical functions of EZH2 and how they are related to different aspects of carcinogenesis.

JARID2 and EZH2, The Eminent Epigenetic Drivers In Human Cancer

Cancer has become a prominent cause of death, accounting for approximately 10 million death worldwide as per the World Health Organization reports 2020. Epigenetics deal with the alterations of heritable phenotypes, except for DNA alterations. Currently, we are trying to comprehend the role of utmost significant epigenetic genes involved in the burgeoning of human cancer. A sundry of studies reported the Enhancer of Zeste Homologue2 (EZH2) as a prime catalytic subunit of Polycomb Repressive Complex2, which is involved in several pivotal activities, including embryogenesis. In addition, EZH2 has detrimental effects leading to the onset and metastasis of several cancers. Jumonji AT Rich Interacting Domain2 (JARID2), an undebated crucial nuclear factor, has strong coordination with the PRC2 family. In this review, we discuss various epigenetic entities, primarily focusing on the possible role and mechanism of EZH2 and the significant contribution of JARID2 in human cancers.

HPIP is an essential scaffolding protein running through the EGFR-RAS-ERK pathway and drives tumorigenesis

The EGFR-RAS-ERK pathway plays a key role in cancer development and progression. However, the integral assembly of EGFR-RAS-ERK signaling complexes from the upstream component EGFR to the downstream component ERK is largely unknown. Here, we show that hematopoietic PBX-interacting protein (HPIP) interacts with all classical components of the EGFR-RAS-ERK pathway and forms at least two complexes with overlapping components. Experiments of HPIP knockout or knockdown and chemical inhibition of HPIP expression showed that HPIP is required for EGFR-RAS-ERK signaling complex formation, EGFR-RAS-ERK signaling activation, and EGFR-RAS-ERK signaling-mediated promotion of aerobic glycolysis as well as cancer cell growth in vitro and in vivo. HPIP expression is correlated with EGFR-RAS-ERK signaling activation and predicts worse clinical outcomes in patients with lung cancer. These results provide insights into EGFR-RAS-ERK signaling complex formation and EGFR-RAS-ERK signaling regulation and suggest that HPIP may be a promising therapeutic target for cancer with dysregulated EGFR-RAS-ERK signaling.

Novel insights into histone lysine methyltransferases in cancer therapy: From epigenetic regulation to selective drugs

The reversible and precise temporal and spatial regulation of histone lysine methyltransferases (KMTs) is essential for epigenome homeostasis. The dysregulation of KMTs is associated with tumor initiation, metastasis, chemoresistance, invasiveness, and the immune microenvironment. Therapeutically, their promising effects are being evaluated in diversified preclinical and clinical trials, demonstrating encouraging outcomes in multiple malignancies. In this review, we have updated recent understandings of KMTs' functions and the development of their targeted inhibitors. First, we provide an updated overview of the regulatory roles of several KMT activities in oncogenesis, tumor suppression, and immune regulation. In addition, we summarize the current targeting strategies in different cancer types and multiple ongoing clinical trials of combination therapies with KMT inhibitors. In summary, we endeavor to depict the regulation of KMT-mediated epigenetic landscape and provide potential epigenetic targets in the treatment of cancers.

Polycomb deficiency drives a FOXP2-high aggressive state targetable by epigenetic inhibitors

Inhibitors of the Polycomb Repressive Complex 2 (PRC2) histone methyltransferase EZH2 are approved for certain cancers, but realizing their wider utility relies upon understanding PRC2 biology in each cancer system. Using a genetic model to delete Ezh2 in KRAS-driven lung adenocarcinomas, we observed that Ezh2 haplo-insufficient tumors were less lethal and lower grade than Ezh2 fully-insufficient tumors, which were poorly differentiated and metastatic. Using three-dimensional cultures and in vivo experiments, we determined that EZH2-deficient tumors were vulnerable to H3K27 demethylase or BET inhibitors. PRC2 loss/inhibition led to de-repression of FOXP2, a transcription factor that promotes migration and stemness, and FOXP2 could be suppressed by BET inhibition. Poorly differentiated human lung cancers were enriched for an H3K27me3-low state, representing a subtype that may benefit from BET inhibition as a single therapy or combined with additional EZH2 inhibition. These data highlight diverse roles of PRC2 in KRAS-driven lung adenocarcinomas, and demonstrate the utility of three-dimensional cultures for exploring epigenetic drug sensitivities for cancer.

Role of EZH2 in Uterine Gland Development

Enhancer of zeste homolog 2 (EZH2) is a core component of polycomb repressive complex 2 that plays a vital role in transcriptional repression of gene expression. Conditional ablation of EZH2 using progesterone receptor (Pgr)-Cre in the mouse uterus has uncovered its roles in regulating uterine epithelial cell growth and stratification, suppressing decidual myofibroblast activation, and maintaining normal female fertility. However, it is unclear whether EZH2 plays a role in the development of uterine glands, which are required for pregnancy success. Herein, we created mice with conditional deletion of Ezh2 using anti-Mullerian hormone receptor type 2 (Amhr2)-Cre recombinase that is expressed in mesenchyme-derived cells of the female reproductive tract. Strikingly, these mice showed marked defects in uterine adenogenesis. Unlike Ezh2 Pgr-Cre conditional knockout mice, deletion of Ezh2 using Amhr2-Cre did not lead to the differentiation of basal-like cells in the uterus. The deficient uterine adenogenesis was accompanied by impaired uterine function and pregnancy loss. Transcriptomic profiling using next generation sequencing revealed dysregulation of genes associated with signaling pathways that play fundamental roles in development and disease. In summary, this study has identified an unrecognized role of EZH2 in uterine gland development, a postnatal event critical for pregnancy success and female fertility.

Serine metabolism orchestrates macrophage polarization by regulating the IGF1-p38 axis

Serine metabolism is reportedly involved in immune cell functions, but whether and how serine metabolism regulates macrophage polarization remain largely unknown. Here, we show that suppressing serine metabolism, either by inhibiting the activity of the key enzyme phosphoglycerate dehydrogenase in the serine biosynthesis pathway or by exogenous serine and glycine restriction, robustly enhances the polarization of interferon-γ-activated macrophages (M(IFN-γ)) but suppresses that of interleukin-4-activated macrophages (M(IL-4)) both in vitro and in vivo. Mechanistically, serine metabolism deficiency increases the expression of IGF1 by reducing the promoter abundance of S-adenosyl methionine-dependent histone H3 lysine 27 trimethylation. IGF1 then activates the p38-dependent JAK-STAT1 axis to promote M(IFN-γ) polarization and suppress STAT6-mediated M(IL-4) activation. This study reveals a new mechanism by which serine metabolism orchestrates macrophage polarization and suggests the manipulation of serine metabolism as a therapeutic strategy for macrophage-mediated immune diseases.

Combined inhibition of PARP and EZH2 for cancer treatment: Current status, opportunities, and challenges

Tumors with BRCA1/2 mutations or homologous recombination repair defects are sensitive to PARP inhibitors through the mechanism of synthetic lethality. Several PARP inhibitors are currently approved for ovarian, breast and pancreatic cancer in clinical practice. However, more than 40% of patients with BRCA1/2 mutations are insensitive to PARP inhibitors, which has aroused attention to the mechanism of PARP resistance and sensitization schemes. PARP inhibitor resistance is related to homologous recombination repair, stability of DNA replication forks, PARylation and epigenetic modification. Studies on epigenetics have become the hotspots of research on PARP inhibitor resistance. As an important epigenetic regulator of transcription mediated by histone methylation, EZH2 interacts with PARP through DNA homologous recombination, DNA replication, posttranslational modification, tumor immunity and other aspects. EZH2 inhibitors have been just shifting from the bench to the bedside, but the combination scheme in cancer therapy has not been fully explored yet. Recently, a revolutionary drug design combining PARP inhibitors and EZH2 inhibitors based on PROTAC techniques has shed light on the resolution of PARP inhibitor resistance. This review summarizes the interactions between EZH2 and PARP, suggests the potential PARP inhibitor sensitization effect of EZH2 inhibitors, and further discusses the potential populations that benefit from the combination of EZH2 inhibitors and PARP inhibitors.

APOBEC3B: Future direction of liver cancer research

Liver cancer is one of the most common cancers in the world, and the rate of liver cancer is high due to the of its illness. The main risk factor for liver cancer is infection with the hepatitis B virus (HBV), but a considerable number of genetic and epigenetic factors are also directly or indirectly involved in the underlying pathogenesis of liver cancer. In particular, the apolipoprotein B mRNA editing enzyme, catalytic peptide-like protein (APOBEC) family (DNA or mRNA editor family), which has been the focus of virology research for more than a decade, has been found to play a significant role in the occurrence and development of various cancers, providing a new direction for the research of liver cancer. APOBEC3B is a cytosine deaminase that controls a variety of biological processes, such as protein expression, innate immunity, and embryonic development, by participating in the process of cytidine deamination to uridine in DNA and RNA. In humans, APOBEC3B has long been known as a DNA editor for limiting viral replication and transcription. APOBEC3B is widely expressed at low levels in a variety of normal tissues and organs, but it is significantly upregulated in different types of tumor tissues and tumor lines. Thus, APOBEC3B has received increasing attention in various cancers, but the role of APOBEC3B in the occurrence and development of liver cancer due to infection with HBV remains unclear. This review provides a brief introduction to the pathogenesis of hepatocellular carcinoma induced by HBV, and it further explores the latest results of APOBEC3B research in the development of HBV and liver cancer, thereby providing new directions and strategies for the treatment and prevention of liver cancer.

Immunohistochemical loss of enhancer of Zeste Homolog 2 (EZH2) protein expression correlates with EZH2 alterations and portends a worse outcome in myelodysplastic syndromes

EZH2 coding mutation (EZH2^MUT), resulting in loss-of-function, is an independent predictor of overall survival in MDS. EZH2 function can be altered by other mechanisms including copy number changes, and mutations in other genes and non-coding regions of EZH2. Assessment of EZH2 protein can identify alterations of EZH2 function missed by mutation assessment alone. Precise evaluation of EZH2 function and gene-protein correlation in clinical MDS cohorts is important in the context of upcoming targeted therapies aimed to restore EZH2 function. In this study, we evaluated the clinicopathologic characteristics of newly diagnosed MDS patients with EZH2^MUT and correlated the findings with protein expression using immunohistochemistry. There were 40 (~6%) EZH2^MUT MDS [33 men, seven women; median age 74 years (range, 55-90)]. EZH2 mutations spanned the entire coding region. Majority had dominant EZH2 clone [median VAF, 30% (1-92)], frequently co-occurring with co-dominant TET2 (38%) and sub-clonal ASXL1 (55%) and RUNX1 (43%) mutations. EZH2^MUT MDS showed frequent loss-of-expression compared to EZH2^WT (69% vs. 27%, p = 0.001). Interestingly, NINE (23%) EZH2^WT MDS also showed loss-of-expression. EZH2^MUT and loss-of-expression significantly associated with male predominance and chr(7) loss. Further, only EZH2 loss-of-expression patients showed significantly lower platelet counts, a trend for higher BM blast% and R-IPSS scores. Over a 14-month median follow-up, both EZH2^MUT (p = 0.027) and loss-of-expression (p = 0.0063) correlated with poor survival, independent of R-IPSS, age and gender. When analyzed together, loss-of-expression showed a stronger correlation than mutation (p = 0.061 vs. p = 0.43). In conclusion, immunohistochemical assessment of EZH2 protein, alongside mutation, is important for prognostic workup of MDS.

miR-126-5p enhances radiosensitivity of lung adenocarcinoma cells by inhibiting EZH2 via the KLF2/BIRC axis

Radiotherapy is a common method for the treatment of lung adenocarcinoma, but it often fails due to the relative non‐susceptibility of lung adenocarcinoma cells to radiation. We aimed to discuss the related mechanisms by which miR‐126‐5p might mediate radiosensitivity of lung adenocarcinoma cells. The binding affinity between miR‐126‐5p and EZH2 and between KLF2 and BIRC5 was identified using multiple assays. A549 and H1650 cells treated with X‐ray were transfected with miR‐126‐5p mimic/inhibitor, oe‐EZH2, or si‐KLF2 to detect cell biological functions and radiosensitivity. Finally, lung adenocarcinoma nude mouse models were established. miR‐126‐5p and KLF2 were poorly expressed, while EZH2 and BIRC5 were upregulated in lung adenocarcinoma tissues and cells. miR‐126‐5p targeted EZH2 to promote the KLF2 expression so as to inhibit BIRC5 activation. Both in vitro and in vivo experiments verified that elevated miR‐126‐5p inhibited cell migration and promoted apoptosis to enhance the sensitivity of lung adenocarcinoma cells to radiotherapy via the EZH2/KLF2/BIRC5 axis. Collectively, miR‐126‐5p downregulated EZH2 to facilitate the sensitivity of lung adenocarcinoma cells to radiotherapy via KLF2/BIRC5.

EZH2 and Endometrial Cancer Development: Insights from a Mouse Model

Enhancer of zeste homolog 2 (EZH2), a core component of polycomb repressive complex 2, plays an important role in cancer development. As both oncogenic and tumor suppressive functions of EZH2 have been documented in the literature, the objective of this study is to determine the impact of Ezh2 deletion on the development and progression of endometrial cancer induced by inactivation of phosphatase and tensin homolog (PTEN), a tumor suppressor gene frequently dysregulated in endometrial cancer patients. To this end, we created mice harboring uterine deletion of both Ezh2 and Pten using Cre recombinase driven by the progesterone receptor (Pgr) promoter. Our results showed reduced tumor burden in Pten^d/d; Ezh2^d/d mice compared with that of Pten^d/d mice during early carcinogenesis. The decreased Ki67 index in EZH2 and PTEN-depleted uteri versus that in PTEN-depleted uteri indicated an oncogenic role of EZH2 during early tumor development. However, mice harboring uterine deletion of both Ezh2 and Pten developed unfavorable disease outcome, accompanied by exacerbated epithelial stratification and heightened inflammatory response. The observed effect was non-cell autonomous and mediated by altered immune response evidenced by massive accumulation of intraluminal neutrophils, a hallmark of endometrial carcinoma in Pten^d/d; Ezh2^d/d mice during disease progression. Hence, these results reveal dual roles of EZH2 in endometrial cancer development.

EZHIP: a new piece of the puzzle towards understanding pediatric posterior fossa ependymoma

Ependymomas (EPN) are tumors of the central nervous system (CNS) that can arise in the supratentorial brain (ST-EPN), hindbrain or posterior fossa (PF-EPN) or anywhere in the spinal cord (SP-EPN), both in children and adults. Molecular profiling studies have identified distinct groups and subtypes in each of these anatomical compartments. In this review, we give an overview on recent findings and new insights what is driving PFA ependymomas, which is the most common group. PFA ependymomas are characterized by a young median age at diagnosis, an overall balanced genome and a bad clinical outcome (56% 10-year overall survival). Sequencing studies revealed no fusion genes or other highly recurrently mutated genes, suggesting that the disease is epigenetically driven. Indeed, recent findings have shown that the characteristic global loss of the repressive histone 3 lysine 27 trimethylation (H3K27me3) mark in PFA ependymoma is caused by aberrant expression of the enhancer of zeste homolog inhibitory protein (EZHIP) or in rare cases by H3K27M mutations, which both inhibit EZH2 thereby preventing the polycomb repressive complex 2 (PRC2) from spreading H3K27me3. We present the current status of the ongoing work on EZHIP and its essential role in the epigenetic disturbance of PFA biology. Comparisons to the oncohistone H3K27M and its role in diffuse midline glioma (DMG) are drawn, highlighting similarities but also differences between the tumor entities and underlying mechanisms. A strong focus is to point out missing information and to present directions of further research that may result in new and improved therapies for PFA ependymoma patients.

Recent Developments in Targeting RAS Downstream Effectors for RAS-Driven Cancer Therapy

Aberrant activity of oncogenic rat sarcoma virus (RAS) protein promotes tumor growth and progression. RAS-driven cancers comprise more than 30% of all human cancers and are refractory to frontline treatment strategies. Since direct targeting of RAS has proven challenging, efforts have been centered on the exploration of inhibitors for RAS downstream effector kinases. Two major RAS downstream signaling pathways, including the Raf/MEK/Erk cascade and the phosphatidylinositol-3-kinase (PI3K) pathway, have become compelling targets for RAS-driven cancer therapy. However, the main drawback in the blockade of a single RAS effector is the multiple levels of crosstalk and compensatory mechanisms between these two pathways that contribute to drug resistance against monotherapies. A growing body of evidence reveals that the sequential or synergistic inhibition of multiple RAS effectors is a more convenient route for the efficacy of cancer therapy. Herein, we revisit the recent developments and discuss the most promising modalities targeting canonical RAS downstream effectors for the treatment of RAS-driven cancers.

Decreased PRC2 activity supports the survival of basal-like breast cancer cells to cytotoxic treatments

Breast cancer (BC) is the most common cancer occurring in women but also rarely develops in men. Recent advances in early diagnosis and development of targeted therapies have greatly improved the survival rate of BC patients. However, the basal-like BC subtype (BLBC), largely overlapping with the triple-negative BC subtype (TNBC), lacks such drug targets and conventional cytotoxic chemotherapies often remain the only treatment option. Thus, the development of resistance to cytotoxic therapies has fatal consequences. To assess the involvement of epigenetic mechanisms and their therapeutic potential increasing cytotoxic drug efficiency, we combined high-throughput RNA- and ChIP-sequencing analyses in BLBC cells. Tumor cells surviving chemotherapy upregulated transcriptional programs of epithelial-to-mesenchymal transition (EMT) and stemness. To our surprise, the same cells showed a pronounced reduction of polycomb repressive complex 2 (PRC2) activity via downregulation of its subunits Ezh2, Suz12, Rbbp7 and Mtf2. Mechanistically, loss of PRC2 activity leads to the de-repression of a set of genes through an epigenetic switch from repressive H3K27me3 to activating H3K27ac mark at regulatory regions. We identified Nfatc1 as an upregulated gene upon loss of PRC2 activity and directly implicated in the transcriptional changes happening upon survival to chemotherapy. Blocking NFATc1 activation reduced epithelial-to-mesenchymal transition, aggressiveness, and therapy resistance of BLBC cells. Our data demonstrate a previously unknown function of PRC2 maintaining low Nfatc1 expression levels and thereby repressing aggressiveness and therapy resistance in BLBC.

High-spatial and colourimetric imaging of histone modifications in single senescent cells using plasmonic nanoprobes

Histones are closely related to the state of chromatin, and epigenetic modification of their tail results in regulation in cells. Therefore, developing various analytical tools to map the changes in position and distribution of histone modifications is helpful in studying underlying mechanisms. Herein, we propose a high-spatial and colourimetric imaging method using plasmonic nanoparticles as probes to visualize heterochromatin histone markers in a single nucleus. We visualized the reorganization between repressive histone markers, H3K9me3 and H3K27me3, caused by oncogene-induced senescence based on the scattering colours and spectral shift of plasmonic nanoprobes to longer wavelengths using their distance-dependent coupling effect. The measured scattering profiles were correlated with the computation results simulating the scattering spectra according to the arrangements and distances among the plasmonic nanoprobes. The plasmonic nanoprobe-based high-spatial hyperspectral imaging provides an advanced way to study the dynamics of histone modifications for predicting the progression of diseases or senescence.

Overexpression of EZH2/NSD2 Histone Methyltransferase Axis Predicts Poor Prognosis and Accelerates Tumor Progression in Triple-Negative Breast Cancer

Two histone methyltransferases, enhancer of zeste homolog 2 (EZH2) and nuclear SET domain-containing 2 (NSD2), are aberrantly expressed in several types of human cancers. However, the regulatory relationship between EZH2 and NSD2 and their prognostic values in breast cancer (BC) have not been fully elucidated. In this study, we demonstrated that EZH2 and NSD2 were overexpressed in BC compared with benign lesions and normal tissues using tissue microarray, immunohistochemistry, and bioinformatic databases. Both EZH2 and NSD2 expression were associated with pathological grade of tumor and lymph node metastasis. A comprehensive survival analysis using Kaplan-Meier Plotter database indicated that EZH2 expression was negatively correlated with relapse-free survival (RFS), overall survival (OS), distant metastasis-free survival (DMFS), and postprogression survival (PPS) in 3951 BC patients, and NSD2 expression was negatively correlated with RFS and DMFS. Notably, EZH2 and NSD2 expression were coordinately higher in triple-negative breast cancer (TNBC) than that in other subtypes. Stable knockdown of EZH2 using lentiviral shRNA vector significantly reduced the proliferation, migration and invasion abilities of TNBC cell line MDA-MB-231 and MDA-MB-468, and downregulated NSD2 expression as well as the levels of H3K27me3 and H3K36me2, two histone methylation markers catalyzed by EZH2 and NSD2, respectively. By contrast, overexpression of EZH2 using adenovirus vector displayed an inverse phenotype. Furthermore, knockdown of NSD2 in EZH2-overexpressing cells could dramatically attenuate EZH2-mediated oncogenic effects. Bioinformatic analysis further revealed the function and pathway enrichments of co-expressed genes and interactive genes of EZH2/NSD2 axis, suggesting that EZH2/NSD2 axis was associated with cell division, mitotic nuclear division and transition of mitotic cell cycle in TNBC. Taken together, EZH2/NSD2 axis may act as a predictive marker for poor prognosis and accelerate the progression of TNBC.

Lysine Methyltransferases Signaling: Histones are Just the Tip of the Iceberg

Protein lysine methylation is a functionally diverse post-translational modification involved in various major cellular processes. Lysine methylation can modulate proteins activity, stability, localization, and/or interaction, resulting in specific downstream signaling and biological outcomes. Lysine methylation is a dynamic and fine-tuned process, deregulation of which often leads to human pathologies. In particular, the lysine methylome and its associated signaling network can be linked to carcinogenesis and cancer progression. Histone modifications and chromatin regulation is a major aspect of lysine methylation importance, but increasing evidence suggests that a high relevance and impact of non-histone lysine methylation signaling has emerged in recent years. In this review, we draw an updated picture of the current scientific knowledge regarding non-histone lysine methylation signaling and its implication in physiological and pathological processes. We aim to demonstrate the significance of lysine methylation as a major and yet underestimated posttranslational modification, and to raise the importance of this modification in both epigenetic and cellular signaling by focusing on the observed activities of SET- and 7β-strandcontaining human lysine methyltransferases. Recent evidence suggests that what has been observed so far regarding lysine methylation's implication in human pathologies is only the tip of the iceberg. Therefore, the exploration of the "methylome network" raises the possibility to use these enzymes and their substrates as promising new therapeutic targets for the development of future epigenetic and methyllysine signaling cancer treatments.

EZH2 facilitates BMI1-dependent hepatocarcinogenesis through epigenetically silencing microRNA-200c

EZH2, a histone methyltransferase, has been shown to involve in cancer development and progression via epigenetic regulation of tumor suppressor microRNAs, whereas BMI1, a driver of hepatocellular carcinoma (HCC), is a downstream target of these microRNAs. However, it remains unclear whether EZH2 can epigenetically regulate microRNA expression to modulate BMI1-dependent hepatocarcinogenesis. Here, we established that high EZH2 expression correlated with enhanced tumor size, elevated metastasis, increased relapse, and poor prognosis in HCC patients. Further clinical studies revealed that EZH2 overexpression was positively correlated to its gene copy number gain/amplification in HCC. Mechanistically, EZH2 epigenetically suppressed miR-200c expression both in vitro and in vivo, and more importantly, miR-200c post-transcriptionally regulated BMI1 expression by binding to the 3'-UTR region of its mRNA. Furthermore, miR-200c overexpression inhibits the growth of HCC cells in vivo. Silencing miR-200c rescued the tumorigenicity of EZH2-depleted HCC cells, whereas knocking down BMI1 reduced the promoting effect of miR-200c depletion on HCC cell migration. Finally, combination treatment of EZH2 and BMI1 inhibitors further inhibited the viability of HCC cells compared with the cells treated with EZH2 or BMI1 inhibitor alone. Our findings demonstrated that alteration of EZH2 gene copy number status induced BMI1-mediated hepatocarcinogenesis via epigenetically silencing miR-200c, providing novel therapeutic targets for HCC treatment.

COCOA: coordinate covariation analysis of epigenetic heterogeneity

A key challenge in epigenetics is to determine the biological significance of epigenetic variation among individuals. We present Coordinate Covariation Analysis (COCOA), a computational framework that uses covariation of epigenetic signals across individuals and a database of region sets to annotate epigenetic heterogeneity. COCOA is the first such tool for DNA methylation data and can also analyze any epigenetic signal with genomic coordinates. We demonstrate COCOA’s utility by analyzing DNA methylation, ATAC-seq, and multi-omic data in supervised and unsupervised analyses, showing that COCOA provides new understanding of inter-sample epigenetic variation. COCOA is available on Bioconductor (http://bioconductor.org/packages/COCOA).

EZH2: a novel target for cancer treatment

Enhancer of zeste homolog 2 (EZH2) is enzymatic catalytic subunit of polycomb repressive complex 2 (PRC2) that can alter downstream target genes expression by trimethylation of Lys-27 in histone 3 (H3K27me3). EZH2 could also regulate gene expression in ways besides H3K27me3. Functions of EZH2 in cells proliferation, apoptosis, and senescence have been identified. Its important roles in the pathophysiology of cancer are now widely concerned. Therefore, targeting EZH2 for cancer therapy is a hot research topic now and different types of EZH2 inhibitors have been developed. In this review, we summarize the structure and action modes of EZH2, focusing on up-to-date findings regarding the role of EZH2 in cancer initiation, progression, metastasis, metabolism, drug resistance, and immunity regulation. Furtherly, we highlight the advance of targeting EZH2 therapies in experiments and clinical studies.

Establishment of a novel cell cycle-related prognostic signature predicting prognosis in patients with endometrial cancer

Background

Endometrial cancer (EnCa) ranks fourth in menace within women’s malignant tumors. Large numbers of studies have proven that functional genes can change the process of tumors by regulating the cell cycle, thereby achieving the goal of targeted therapy.

Methods

The transcriptional data of EnCa samples obtained from the TCGA database was analyzed. A battery of bioinformatics strategies, which included GSEA, Cox and LASSO regression analysis, establishment of a prognostic signature and a nomogram for overall survival (OS) assessment. The GEPIA and CPTAC analysis were applied to validate the dysregulation of hub genes. For mutation analysis, the “maftools” package was used.

Results

GSEA identified that cell cycle was the most associated pathway to EnCa. Five cell cycle-related genes including HMGB3, EZH2, NOTCH2, UCK2 and ODF2 were identified as prognosis-related genes to build a prognostic signature. Based on this model, the EnCa patients could be divided into low- and high-risk groups, and patients with high-risk score exhibited poorer OS. Time-dependent ROC and Cox regression analyses revealed that the 5-gene signature could predict EnCa prognosis exactly and independently. GEPIA and CPTAC validation exhibited that these genes were notably dysregulated between EnCa and normal tissues. Lower mutation rates of PTEN, TTN, ARID1A, and etc. were found in samples with high-risk score compared with that with low-risk score. GSEA analysis suggested that the samples of the low- and high-risk groups were concentrated on various pathways, which accounted for the different oncogenic mechanisms in patients in two groups.

Conclusion

The current research construct a 5-gene signature to evaluate prognosis of EnCa patients, which may innovative clinical application of prognostic assessment.

CAMK2A supported tumor initiating cells of lung adenocarcinoma by upregulating SOX2 through EZH2 phosphorylation

Tumor initiating cells (TIC) of lung cancer are mainly induced by stress-related plasticity. Calcium/Calmodulin dependent protein kinase II alpha (CAMK2A) is a key calcium signaling molecule activated by exogenous and endogenous stimuli with effects on multiple cell functions but little is known about its role on TIC. In human lung adenocarcinomas (AD), CAMK2A was aberrantly activated in a proportion of cases and was an independent risk factor predicting shorter survivals. Functionally, CAMK2A enhanced TIC phenotypes in vitro and in vivo. CAMK2A regulated SOX2 expression by reducing H3K27me3 and EZH2 occupancy at SOX2 regulatory regions, leading to its epigenetic de-repression with functional consequences. Further, CAMK2A caused kinase-dependent phosphorylation of EZH2 at T487 with suppression of EZH2 activity. Together, the data demonstrated the CAMK2A-EZH2-SOX2 axis on TIC regulation. This study provided phenotypic and mechanistic evidence for the TIC supportive role of CAMK2A, implicating a novel predictive and therapeutic target for lung cancer.

The Histone Code of Senescence

Senescence is the end point of a complex cellular response that proceeds through a set of highly regulated steps. Initially, the permanent cell-cycle arrest that characterizes senescence is a pro-survival response to irreparable DNA damage. The maintenance of this prolonged condition requires the adaptation of the cells to an unfavorable, demanding and stressful microenvironment. This adaptation is orchestrated through a deep epigenetic resetting. A first wave of epigenetic changes builds a dam on irreparable DNA damage and sustains the pro-survival response and the cell-cycle arrest. Later on, a second wave of epigenetic modifications allows the genomic reorganization to sustain the transcription of pro-inflammatory genes. The balanced epigenetic dynamism of senescent cells influences physiological processes, such as differentiation, embryogenesis and aging, while its alteration leads to cancer, neurodegeneration and premature aging. Here we provide an overview of the most relevant histone modifications, which characterize senescence, aging and the activation of a prolonged DNA damage response.

APOBEC3B interaction with PRC2 modulates microenvironment to promote HCC progression

OBJECTIVE

APOBEC3B (A3B), a cytidine deaminase acting as a contributor to the APOBEC mutation pattern in many kinds of tumours, is upregulated in patients with hepatocellular carcinoma (HCC). However, APOBEC mutation patterns are absent in HCC. The mechanism of how A3B affects HCC progression remains elusive.

DESIGN

A3B -promoter luciferase reporter and other techniques were applied to elucidate mechanisms of A3B upregulation in HCC. A3B overexpression and knockdown cell models, immunocompetent and immune-deficient mouse HCC model were conducted to investigate the influence of A3B on HCC progression. RNA-seq, flow cytometry and other techniques were conducted to analyse how A3B modulated the cytokine to enhance the recruitment of myeloid--derived suppressor cells (MDSCs) and tumour--associated macrophages (TAMs).

RESULTS

A3B upregulation through non-classical nuclear factor-κB (NF-κB)signalling promotes HCC growth in immunocompetent mice, associated with an increase of MDSCs, TAMs and programmed cell death1 (PD1) exprssed CD8⁺ T cells. A CCR2 antagonist suppressed TAMs and MDSCs infiltration and delayed tumour growth in A3B and A3B^E68Q/E255Q- expressing mouse tumours. Mechanistically, A3B upregulation in HCC depresses global H3K27me3 abundance via interaction with polycomb repressor complex 2 (PRC2) and reduces an occupancy of H3K27me3 on promoters of the chemokine CCL2 to recruit massive TAMs and MDSCs.

CONCLUSION

Our observations uncover a deaminase-independent role of the A3B in modulating the HCC microenvironment and demonstrate a proof for the concept of targeting A3B in HCC immunotherapy.

Epigenetic Regulation of Inflammatory Cytokine-Induced Epithelial-To-Mesenchymal Cell Transition and Cancer Stem Cell Generation

The neoplastic transformation of normal to metastatic cancer cells is a complex multistep process involving the progressive accumulation of interacting genetic and epigenetic changes that alter gene function and affect cell physiology and homeostasis. Epigenetic changes including DNA methylation, histone modifications and changes in noncoding RNA expression, and deregulation of epigenetic processes can alter gene expression during the multistep process of carcinogenesis. Cancer progression and metastasis through an ‘invasion–metastasis cascade’ involving an epithelial-to-mesenchymal cell transition (EMT), the generation of cancer stem cells (CSCs), invasion of adjacent tissues, and dissemination are fueled by inflammation, which is considered a hallmark of cancer. Chronic inflammation is generated by inflammatory cytokines secreted by the tumor and the tumor-associated cells within the tumor microenvironment. Inflammatory cytokine signaling initiates signaling pathways leading to the activation of master transcription factors (TFs) such as Smads, STAT3, and NF-κB. Moreover, the same inflammatory responses also activate EMT-inducing TF (EMT-TF) families such as Snail, Twist, and Zeb, and epigenetic regulators including DNA and histone modifying enzymes and micoRNAs, through complex interconnected positive and negative feedback loops to regulate EMT and CSC generation. Here, we review the molecular regulatory feedback loops and networks involved in inflammatory cytokine-induced EMT and CSC generation.

Dysregulated Tgfbr2/ERK-Smad4/SOX2 Signaling Promotes Lung Squamous Cell Carcinoma Formation

Lung squamous cell carcinoma (SCC) is a common type of lung cancer. There is limited information on the genes and pathways that initiate lung SCC. Here, we report that loss of TGFβ type II receptor (Tgfbr2), frequently deleted in human lung cancer, led to predominant lung SCC development in Kras^G12D mice with a short latency, high penetrance, and extensive metastases. Tgfbr2-loss-driven lung SCCs resembled the salient features of human lung SCC, including histopathology, inflammatory microenvironment, and biomarker expression. Surprisingly, loss of Smad4, a key mediator of Tgfbr2, failed to drive lung SCC; instead, low levels of phosphorylated ERK1/2, a Smad-independent downstream effector of Tgfbr2, were tightly associated with lung SCC in both mouse and human. Mechanistically, inhibition of phosphorylated ERK1/2 significantly upregulated the expression of SOX2, an oncogenic driver of lung SCC, and cooperated with SMAD4 repression to elevate SOX2. Inhibition of ERK1/2 in Smad4^fl/fl ;Kras^G12D mice led to extensive lung SCC formation that resembled the SCC phenotype of Tgfbr2-deficient mice. Overall, we reveal a key role of ERK1/2 in suppressing SCC formation and demonstrate that dysregulated Tgfbr2/ERK-Smad4/SOX2 signaling drives lung SCC formation. We also present a mouse model of metastatic lung SCC that may be valuable for screening therapeutic targets. SIGNIFICANCE: This study sheds new light on the mechanisms underlying lung SCC formation driven by mutated Kras.

Analysis of the role of mutations in the KMT2D histone lysine methyltransferase in bladder cancer

Histone lysine methyltransferases (HMT) comprise a subclass of epigenetic regulators; dysregulation of these enzymes affects gene expression, which may lead to tumorigenesis. Here, we performed an integrated analysis of 50 HMTs in bladder cancer and found intrinsic links between copy number alterations, mutations, gene expression levels, and clinical outcomes. Through integrative analysis, we identified six HMT genes (PRDM9,ASH1L,SETD3,SETD5,WHSC1L1, and KMT2D) that may play a key role in the development and progression of bladder cancer. Of these six HMTs, histone lysine N‐methyltransferase 2D (KMT2D) exhibited the highest mutation rate in bladder cancer. Our comparison of the mRNA and miRNA expression profiles of mutated and wild‐type KMT2D suggested that two signaling pathways (FOX1–miR‐1224‐5p–DLK1 and HIF/GATA5–miR‐133a‐3p–DRD5) may mediate the tumor suppressive effect of the KMT2D mutation. In summary, our findings indicate that mutations in HMT genes, especially KMT2D mutation, may play a role in the development of bladder cancer.

Targeting the cell signaling pathway Keap1-Nrf2 as a therapeutic strategy for adenocarcinomas of the lung

INTRODUCTION

Kelch-like ECH associated protein 1/Nuclear factor erythroid 2-like factor 2 (Keap1-Nrf2) signaling plays a pivotal role in response to oxidative stress in lung cancer. Mutations in KEAP1/NFE2L2 genes always cause persistent Nrf2 activation in lung cancer cells that confer therapeutic resistance and aggressive tumorigenic activity, dictating either poor prognosis or short duration of response to chemotherapy in clinical observations. Areas covered: We provide a review of the mechanisms underlying the regulation of Keap1-Nrf2 at different stages, including genetic mutations, epigenetic modifications, translational/post-translational alterations, and protein-protein interactions. Based on the current knowledge, we discuss the possibilities of intervening Keap1-Nrf2 in lung adenocarcinoma as a therapeutic target. Expert opinion: It is prevalently conceived that Keap1-Nrf2 signaling plays different roles at diverse stages of cancer. Although various Nrf2 or Keap1 inhibitors have been reported during the last decades, none of these inhibitors are currently under clinical studies or in clinical applications, suggesting that sole inhibition of Nrf2 might not be sufficient to suppress tumor growth. On the basis of current studies, we suggest that the rational combination of Nrf2 suppression with chemical agents which cause enhanced oxidative imbalance or abnormal metabolism would be promising in the treatment of lung adenocarcinoma.

Epigenetic Regulation of EMT (Epithelial to Mesenchymal Transition) and Tumor Aggressiveness: A View on Paradoxical Roles of KDM6B and EZH2

EMT (epithelial to mesenchymal transition) is a plastic phenomenon involved in metastasis formation. Its plasticity is conferred in a great part by its epigenetic regulation. It has been reported that the trimethylation of lysine 27 histone H3 (H3K27me3) was a master regulator of EMT through two antagonist enzymes that regulate this mark, the methyltransferase EZH2 (enhancer of zeste homolog 2) and the lysine demethylase KDM6B (lysine femethylase 6B). Here we report that EZH2 and KDM6B are overexpressed in numerous cancers and involved in the aggressive phenotype and EMT in various cell lines by regulating a specific subset of genes. The first paradoxical role of these enzymes is that they are antagonistic, but both involved in cancer aggressiveness and EMT. The second paradoxical role of EZH2 and KDM6B during EMT and cancer aggressiveness is that they are also inactivated or under-expressed in some cancer types and linked to epithelial phenotypes in other cancer cell lines. We also report that new cancer therapeutic strategies are targeting KDM6B and EZH2, but the specificity of these treatments may be increased by learning more about the mechanisms of action of these enzymes and their specific partners or target genes in different cancer types.

Unscheduled HDAC4 repressive activity in human fibroblasts triggers TP53-dependent senescence and favors cell transformation

Expression of the class IIa HDACs is frequently altered in different human cancers. In mouse models these transcriptional repressors can trigger transformation, acting as bona fide oncogenes. Whether class IIa HDACs also exhibit transforming activities in human cells is currently unknown. We infected primary human fibroblasts with retroviruses to investigate the transforming activity of HDAC4 in cooperation with well‐known oncogenes. We have discovered that HDAC4 triple mutant (S246A, S467A, S632A) (HDAC4‐TM), a nuclear resident version of the deacetylase, triggers TP53 stabilization and OIS (oncogene‐induced senescence). Unlike RAS, HDAC4‐induced OIS was TP53‐dependent and characterized by rapid cell cycle arrest and accumulation of an unusual pattern of γH2AX‐positive foci. The inactivation of both TP53 and of the retinoblastoma (pRb) tumor suppressors, as induced by the viral oncogenes large and small T of SV40, triggers anchorage‐independent growth in RAS, HDAC4‐TM and, to a lesser extent, in HDAC4‐wild type (WT)‐expressing cells. Our results suggest an oncogenic function of class IIa HDACs in human cells, and justify further efforts to discover and evaluate isoform‐specific inhibitors of these epigenetic regulators from a therapeutic perspective.