The role of the histone demethylase KDM4A in cancer

The role of JMJD2A in immune evasion and malignant behavior of esophageal squamous cell carcinoma

OBJECTIVE

This study aimed to investigate the role of JMJD2A in radiotherapy tolerance of esophageal squamous cell carcinoma (ESCC).

METHODS

The levels of H3K9me3 modification were analyzed in anti-PD-1 therapy non-responder or responder patients, and the expression differences of H3K9me3-related modifying enzymes were assessed in TCGA-ESCC and ICGC cohorts. Subsequently, JMJD2A was knocked down in ESCC cells using CRISPR-Cas9 or lentivirus-mediated shRNA, and changes in malignant behavior of ESCC cells were observed. RNA-seq, ATAC-seq, and ChIP-seq analyses were then conducted to investigate the genes and downstream signaling pathways regulated by JMJD2A, and functional validation experiments were performed to analyze the role of downstream regulated genes and pathways in ESCC malignant behavior and immune evasion.

RESULTS

JMJD2A was significantly overexpressed in ESCC and anti-PD-1 therapy non-responders. Knockdown or deletion of JMJD2A significantly promoted the malignant behavior and immune evasion of ESCC. JMJD2A facilitated the structural changes in chromatin and promoted the binding of SMARCA4 to super-enhancers, thereby inducing the expression of GPX4. This resulted in the inhibition of radiation-induced DNA damage and cell ferroptosis, ultimately promoting the malignant behavior and immune evasion of ESCC cells.

CONCLUSION

JMJD2A plays an indispensable role in the malignant behavior and immune evasion of ESCC. It regulates the binding of SMARCA4 to super-enhancers and affects the chromatin's epigenetic landscape, thereby promoting the expression of GPX4 and attenuating iron-mediated cell death caused by radiotherapy. Consequently, it triggers the malignant behavior and immune evasion of ESCC cells.

The JMJD family of histone demethylase and their intimate links to cardiovascular disease

The incidence rate and mortality rate of cardiovascular disease rank first in the world. It is associated with various high-risk factors, and there is no single cause. Epigenetic modifications, such as DNA methylation or histone modification, actively participate in the initiation and development of cardiovascular diseases. Histone lysine methylation is a type of histone post-translational modification. The human Jumonji C domain (JMJD) protein family consists of more than 30 members. JMJD proteins participate in many key nuclear processes and play a key role in the specific regulation of gene expression, DNA damage and repair, and DNA replication. Importantly, increasing evidence shows that JMJD proteins are abnormally expressed in cardiovascular diseases, which may be a potential mechanism for the occurrence and development of these diseases. Here, we discuss the key roles of JMJD proteins in various common cardiovascular diseases. This includes histone lysine demethylase, which has been studied in depth, and less-studied JMJD members. Furthermore, we focus on the epigenetic changes induced by each JMJD member, summarize recent research progress, and evaluate their relationship with cardiovascular diseases and therapeutic potential.

The emerging roles of lysine-specific demethylase 4A in cancer: Implications in tumorigenesis and therapeutic opportunities

Lysine-specific demethylase 4 A (KDM4A, also named JMJD2A, KIA0677, or JHDM3A) is a demethylase that can remove methyl groups from histones H3K9me2/3, H3K36me2/3, and H1.4K26me2/me3. Accumulating evidence suggests that KDM4A is not only involved in body homeostasis (such as cell proliferation, migration and differentiation, and tissue development) but also associated with multiple human diseases, especially cancers. Recently, an increasing number of studies have shown that pharmacological inhibition of KDM4A significantly attenuates tumor progression in vitro and in vivo in a range of solid tumors and acute myeloid leukemia. Although there are several reviews on the roles of the KDM4 subfamily in cancer development and therapy, all of them only briefly introduce the roles of KDM4A in cancer without systematically summarizing the specific mechanisms of KDM4A in various physiological and pathological processes, especially in tumorigenesis, which greatly limits advances in the understanding of the roles of KDM4A in a variety of cancers, discovering targeted selective KDM4A inhibitors, and exploring the adaptive profiles of KDM4A antagonists. Herein, we present the structure and functions of KDM4A, simply outline the functions of KDM4A in homeostasis and non-cancer diseases, summarize the role of KDM4A and its distinct target genes in the development of a variety of cancers, systematically classify KDM4A inhibitors, summarize the difficulties encountered in the research of KDM4A and the discovery of related drugs, and provide the corresponding solutions, which would contribute to understanding the recent research trends on KDM4A and advancing the progression of KDM4A as a drug target in cancer therapy.

The role and prospect of lysine-specific demethylases in cancer chemoresistance

Histone methylation plays a key function in modulating gene expression, and preserving genome integrity and epigenetic inheritance. However, aberrations of histone methylation are commonly observed in human diseases, especially cancer. Lysine methylation mediated by histone methyltransferases can be reversed by lysine demethylases (KDMs), which remove methyl marks from histone lysine residues. Currently, drug resistance is a main impediment for cancer therapy. KDMs have been found to mediate drug tolerance of many cancers via altering the metabolic profile of cancer cells, upregulating the ratio of cancer stem cells and drug-tolerant genes, and promoting the epithelial-mesenchymal transition and metastatic ability. Moreover, different cancers show distinct oncogenic addictions for KDMs. The abnormal activation or overexpression of KDMs can alter gene expression signatures to enhance cell survival and drug resistance in cancer cells. In this review, we describe the structural features and functions of KDMs, the KDMs preferences of different cancers, and the mechanisms of drug resistance resulting from KDMs. We then survey KDM inhibitors that have been used for combating drug resistance in cancer, and discuss the opportunities and challenges of KDMs as therapeutic targets for cancer drug resistance.

Carcinogenesis promotion in oral squamous cell carcinoma: KDM4A complex-mediated gene transcriptional suppression by LEF1

Oral squamous cell carcinoma (OSCC) is the most prevalent cancer of the mouth, characterised by rapid progression and poor prognosis. Hence, an urgent need exists for the development of predictive targets for early diagnosis, prognosis determination, and clinical therapy. Dysregulation of lymphoid enhancer-binding factor 1 (LEF1), an important transcription factor involved in the Wnt-β-catenin pathway, contributes to the poor prognosis of OSCC. Herein, we aimed to explore the correlation between LEF1 and histone lysine demethylase 4 A (KDM4A). Results show that the KDM4A complex is recruited by LEF1 and specifically binds the LATS2 promoter region, thereby inhibiting its expression, and consequently promoting cell proliferation and impeding apoptosis in OSCC. We also established NOD/SCID mouse xenograft models using CAL-27 cells to conduct an in vivo analysis of the roles of LEF1 and KDM4A in tumour growth, and our findings show that cells stably suppressing LEF1 or KDM4A have markedly decreased tumour-initiating capacity. Overall, the results of this study demonstrate that LEF1 plays a pivotal role in OSCC development and has potential to serve as a target for early diagnosis and treatment of OSCC.

CTCF and Its Multi-Partner Network for Chromatin Regulation

Architectural proteins are essential epigenetic regulators that play a critical role in organizing chromatin and controlling gene expression. CTCF (CCCTC-binding factor) is a key architectural protein responsible for maintaining the intricate 3D structure of chromatin. Because of its multivalent properties and plasticity to bind various sequences, CTCF is similar to a Swiss knife for genome organization. Despite the importance of this protein, its mechanisms of action are not fully elucidated. It has been hypothesized that its versatility is achieved through interaction with multiple partners, forming a complex network that regulates chromatin folding within the nucleus. In this review, we delve into CTCF's interactions with other molecules involved in epigenetic processes, particularly histone and DNA demethylases, as well as several long non-coding RNAs (lncRNAs) that are able to recruit CTCF. Our review highlights the importance of CTCF partners to shed light on chromatin regulation and pave the way for future exploration of the mechanisms that enable the finely-tuned role of CTCF as a master regulator of chromatin.

Two Onnamide Analogs from the Marine Sponge Theonella conica: Evaluation of Geometric Effects in the Polyene Systems on Biological Activity

Two previously unreported onnamide analogs, 2Z- and 6Z-onnamides A (1 and 2), were isolated from the marine sponge Theonella conica collected at Amami-Oshima Is., Kagoshima Prefecture, Japan. Structures of compounds 1 and 2 were elucidated by spectral analysis. Structure–activity relationships (SARs) for effects on histone modifications and cytotoxicity against HeLa and P388 cells were characterized. The geometry in the polyene systems of onnamides affected the histone modification levels and cytotoxicity.

KDM4A, involved in the inflammatory and oxidative stress caused by traumatic brain injury-hemorrhagic shock, partly through the regulation of the microglia M1 polarization

BACKGROUND

Microglial polarization and the subsequent neuroinflammatory response and oxidative stress are contributing factors for traumatic brain injury (TBI) plus hemorrhagic shock (HS) induced brain injury. In the present work, we have explored whether Lysine (K)-specific demethylase 4 A (KDM4A) modulates microglia M1 polarization in the TBI and HS mice.

RESULTS

Male C57BL/6J mice were used to investigate the microglia polarization in the TBI + HS model in vivo. Lipopolysaccharide (LPS)-induced BV2 cells were used to examine the mechanism of KDM4A in regulating microglia polarization in vitro. We found that TBI + HS resulted in neuronal loss and microglia M1 polarization in vivo, reflected by the increased level of Iba1, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, malondialdehyde (MDA) and the decreased level of reduced glutathione (GSH). Additionally, KDM4A was upregulated in response to TBI + HS and microglia were among the cell types showing the increased level of KDM4A. Similar to the results in vivo, KDM4A also highly expressed in LPS-induced BV2 cells. LPS-induced BV2 cells exhibited enhanced microglia M1 polarization, and enhanced level of pro-inflammatory cytokines, oxidative stress and reactive oxygen species (ROS), while this enhancement was abolished by the suppression of KDM4A.

CONCLUSION

Accordingly, our findings indicated that KDM4A was upregulated in response to TBI + HS and microglia were among the cell types showing the increased level of KDM4A. The important role of KDM4A in TBI + HS-induced inflammatory response and oxidative stress was at least partially realized through regulating microglia M1 polarization.

IRX2 activated by jumonji domain-containing protein 2A is crucial for cardiac hypertrophy and dysfunction in response to the hypertrophic stimuli

BACKGROUND

Iroquois homeobox 2 (IRX2) is a member of the Iroquois family whose upregulation has been potentially correlated to cardiac hypertrophy. This work studied the function of IRX2 and its related molecules in hypertrophic cardiomyopathy (HCM).

METHODS

A GEO dataset GSE32453 was analyzed to identify aberrantly expressed genes in HCM. Altered expression of IRX2 was induced in mice by lentivirus injection, followed by angiotensin II (Ang II) treatment to induce HCM. The function of IRX2 knockdown in ventricular dysfunction, heart volume and pathological changes in mice, and in surface area, oxidative stress and apoptosis of isolated cardiomyocytes were examined. Binding relationship between jumonji domain-containing protein 2A (JMJD2A) and IRX2 was predicted by online tools and validated. The interaction between JMJD2A and IRX2 in HCM development was examined by joint interventions.

RESULTS

IRX2 was highly expressed in heart tissues with HCM. IRX2 knockdown prevented mice from Ang II-induced ventricular dysfunction, cardiac hypertrophy, inflammation and fibrosis in mouse heart, and it decreased the levels of cardiac hypertrophy-related markers, oxidative stress response, and apoptosis of Ang II-treated cardiomyocytes. JMJD2A catalyzed demethylation of H3K9me3 near the IRX2 promoter to activate its transcription. JMJD2A knockdown similarly exerted protective functions against cardiac hypertrophy in vivo and in vitro, but the protection was blocked upon further IRX2 upregulation. IRX2 was found to increase the Wnt/β-catenin signaling activation.

CONCLUSION

This work reports that JMJD2A activates IRX2 transcription and the Wnt/β-catenin signaling to induce cardiac hypertrophy and dysfunction in HCM.

Allele-Specific Chemical Rescue of Histone Demethylases Using Abiotic Cofactors

Closely related protein families evolved from common ancestral genes present a significant hurdle in developing member- and isoform-specific chemical probes, owing to their similarity in fold and function. In this piece of work, we explore an allele-specific chemical rescue strategy to activate a "dead" variant of a wildtype protein using synthetic cofactors and demonstrate its successful application to the members of the alpha-ketoglutarate (αKG)-dependent histone demethylase 4 (KDM4) family. We show that a mutation at a specific residue in the catalytic site renders the variant inactive toward the natural cosubstrate. In contrast, αKG derivatives bearing appropriate stereoelectronic features endowed the mutant with native-like demethylase activity while remaining refractory to a set of wild type dioxygenases. The orthogonal enzyme-cofactor pairs demonstrated site- and degree-specific lysine demethylation on a full-length chromosomal histone in the cellular milieu. Our work offers a strategy to modulate a specific histone demethylase by identifying and engineering a conserved phenylalanine residue, which acts as a gatekeeper in the KDM4 subfamily, to sensitize the enzyme toward a novel set of αKG derivatives. The orthogonal pairs developed herein will serve as probes to study the role of degree-specific lysine demethylation in mammalian gene expression. Furthermore, this approach to overcome active site degeneracy is expected to have general application among all human αKG-dependent dioxygenases.

SUMO Modification of Histone Demethylase KDM4A in Kaposi's Sarcoma-Associated Herpesvirus-Induced Primary Effusion Lymphoma

Primary effusion lymphoma (PEL) is a fatal B-cell lymphoma caused by Kaposi’s sarcoma-associated herpesvirus (KSHV) infection. Inducing KSHV lytic replication that causes the death of host cells is an attractive treatment approach for PE; however, combination therapy inhibiting viral production is frequently needed to improve its outcomes. We have previously shown that the KSHV lytic protein K-bZIP can SUMOylate histone lysine demethylase 4A (KDM4A) at lysine 471 (K471) and this SUMOylation is required for virus production upon KSHV reactivation. Here, we demonstrate that SUMOylation of KDM4A orchestrates PEL cell survival, a major challenge for the success of PEL treatment; and cell movement and angiogenesis, the cell functions contributing to PEL cell extravasation and dissemination. Furthermore, integrated ChIP-seq and RNA-seq analyses identified interleukin-10 (IL-10), an immunosuppressive cytokine, as a novel downstream target of KDM4A. We demonstrate that PEL-induced angiogenesis is dependent on IL-10. More importantly, single-cell RNA sequencing (scRNA-seq) analysis demonstrated that, at the late stage of KSHV reactivation, KDM4A determines the fates of PEL cells, as evidenced by two distinct cell populations; one with less apoptotic signaling expresses high levels of viral genes and the other is exactly opposite, while KDM4A-K417R-expressing cells contain only the apoptotic population with less viral gene expression. Consistently, KDM4A knockout significantly reduced cell viability and virus production in KSHV-reactivated PEL cells. Since inhibiting PEL extravasation and eradicating KSHV-infected PEL cells without increasing viral load provide a strong rationale for treating PEL, this study indicates targeting KDM4A as a promising therapeutic option for treating PEL.

IMPORTANCE PEL is an aggressive and untreatable B-cell lymphoma caused by KSHV infection. Therefore, new therapeutic approaches for PEL need to be investigated. Since simultaneous induction of KSHV reactivation and apoptosis can directly kill PEL cells, they have been applied in the treatment of this hematologic malignancy and have made progress. Epigenetic therapy with histone deacetylase (HDAC) inhibitors has been proved to treat PEL. However, the antitumor efficacies of HDAC inhibitors are modest and new approaches are needed. Following our previous report showing that the histone lysine demethylase KDM4A and its SUMOylation are required for lytic reactivation of KSHV in PEL cells, we further investigated its cellular function. Here, we found that SUMOylation of KDM4A is required for the survival, movement, and angiogenesis of lytic KSHV-infected PEL cells. Together with our previous finding showing the importance of KDM4A SUMOylation in viral production, KDM4A can be a potential therapeutic target for PEL.

Cantharidin Inhibits Proliferation of Liver Cancer by Inducing DNA Damage via KDM4A-Dependent Histone H3K36 Demethylation

Objective

To investigate the effect of cantharidin on DNA damage in hepatocellular carcinoma cells and its possible mechanism.

Methods

Cell proliferation assay and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay were used to analyze the effects of cantharidin on cell proliferation and apoptosis of hepatocellular carcinoma cells. The expression levels of DNA damage markers H2AX and P21 were analyzed by qRT-PCR. The expression of KDM4A and H3K36me3 was observed by western blot. The expression of KDM4A was regulated by siRNA or plasmid transfection. The effect of KDM4A on DNA damage induced by cantharidin in liver cancer was observed after overexpression and addiction of KDM4A.

Results

Cantharidin can significantly inhibit the growth of hepatocellular carcinoma cells and induce apoptosis of hepatocellular carcinoma cells. Cantharidin enhances the chemotherapy sensitivity of liver cancer by targeting the upregulation of KDM4A and the regulation of DNA damage induced by H3K36me3. Overexpression of KDM4A enhances DNA damage induced by cantharidin in HCC. KDM4A silencing attenuated the damage of cantharidin to the DNA of HCC cells.

Conclusion

Cantharidin can inhibit the growth and promote apoptosis of hepatocellular carcinoma cells. Meanwhile, cantharidin can induce DNA damage in HCC cells. Mechanism studies have shown that cantharidin induces DNA damage through the demethylation of KDM4A-dependent histone H3K36.

SETD2: from chromatin modifier to multipronged regulator of the genome and beyond

Histone modifying enzymes play critical roles in many key cellular processes and are appealing proteins for targeting by small molecules in disease. However, while the functions of histone modifying enzymes are often linked to epigenetic regulation of the genome, an emerging theme is that these enzymes often also act by non-catalytic and/or non-epigenetic mechanisms. SETD2 (Set2 in yeast) is best known for associating with the transcription machinery and methylating histone H3 on lysine 36 (H3K36) during transcription. This well-characterized molecular function of SETD2 plays a role in fine-tuning transcription, maintaining chromatin integrity, and mRNA processing. Here we give an overview of the various molecular functions and mechanisms of regulation of H3K36 methylation by Set2/SETD2. These fundamental insights are important to understand SETD2’s role in disease, most notably in cancer in which SETD2 is frequently inactivated. SETD2 also methylates non-histone substrates such as α-tubulin which may promote genome stability and contribute to the tumor-suppressor function of SETD2. Thus, to understand its role in disease, it is important to understand and dissect the multiple roles of SETD2 within the cell. In this review we discuss how histone methylation by Set2/SETD2 has led the way in connecting histone modifications in active regions of the genome to chromatin functions and how SETD2 is leading the way to showing that we also have to look beyond histones to truly understand the physiological role of an ‘epigenetic’ writer enzyme in normal cells and in disease.

Transcriptomic and Drug Discovery Analyses Reveal Natural Compounds Targeting the KDM4 Subfamily as Promising Adjuvant Treatments in Cancer

KDM4 proteins are a subfamily of histone demethylases that target the trimethylation of lysines 9 and 36 of histone H3, which are associated with transcriptional repression and elongation respectively. Their deregulation in cancer may lead to chromatin structure alteration and transcriptional defects that could promote malignancy. Despite that KDM4 proteins are promising drug targets in cancer therapy, only a few drugs have been described as inhibitors of these enzymes, while studies on natural compounds as possible inhibitors are still needed. Natural compounds are a major source of biologically active substances and many are known to target epigenetic processes such as DNA methylation and histone deacetylation, making them a rich source for the discovery of new histone demethylase inhibitors. Here, using transcriptomic analyses we determined that the KDM4 family is deregulated and associated with a poor prognosis in multiple neoplastic tissues. Also, by molecular docking and molecular dynamics approaches, we screened the COCONUT database to search for inhibitors of natural origin compared to FDA-approved drugs and DrugBank databases. We found that molecules from natural products presented the best scores in the FRED docking analysis. Molecules with sugars, aromatic rings, and the presence of OH or O- groups favor the interaction with the active site of KDM4 subfamily proteins. Finally, we integrated a protein-protein interaction network to correlate data from transcriptomic analysis and docking screenings to propose FDA-approved drugs that could be used as multitarget therapies or in combination with the potential natural inhibitors of KDM4 enzymes. This study highlights the relevance of the KDM4 family in cancer and proposes natural compounds that could be used as potential therapies.

Free L-Lysine and Its Methyl Ester React with Glyoxal and Methylglyoxal in Phosphate Buffer (100 mM, pH 7.4) to Form Nε-Carboxymethyl-Lysine, Nε-Carboxyethyl-Lysine and Nε-Hydroxymethyl-Lysine

Glyoxal (GO) and methylglyoxal (MGO) are highly reactive species formed in carbohydrate metabolism. N^ε-Carboxymethyllysine (CML) and N^ε-carboxyethyllysine (CEL) are considered to be the advanced glycation end-products (AGEs) of L-lysine (Lys) with GO and MGO, respectively. Here, we investigated the reaction of free L-lysine (Lys) with GO and MGO in phosphate buffer (pH 7.4) at 37 °C and 80 °C in detail in the absence of any other chemicals which are widely used to reduce Schiff bases. The concentrations of Lys, GO and MGO used in the experiments were 0.5, 2.5, 5.0, 7.5 and 10 mM. The reaction time ranged between 0 and 240 min. Experiments were performed in triplicate. The concentrations of remaining Lys and of CML and CEL formed in the reaction mixtures were measured by stable-isotope dilution gas chromatography-mass spectrometry (GC-MS). Our experiments showed that CML and CEL were formed at higher concentrations at 80 °C compared to 37 °C. CML was found to be the major reaction product. In mixtures of GO and MGO, MGO inhibited the formation of CML from Lys (5 mM) in a concentration-dependent manner. The highest CML concentration was about 300 µM corresponding to a reaction yield of 6% with respect to Lys. An addition of Lys to GO, MGO and their mixtures resulted in strong reversible decreases in the Lys concentration up to 50%. It is assumed that free Lys reacts rapidly with GO and MGO to form many not yet identified reaction products. Reaction mixtures of Lys and MGO were stronger colored than those of Lys and GO, notably at 80 °C, indicating higher reactivity of MGO towards Lys that leads to polymeric colored MGO species. We have a strong indication of the formation of N^ε-(hydroxymethyl)-lysine (HML) as a novel reaction product of Lys methyl ester with MGO. A mechanism is proposed for the formation of HML from Lys and MGO. This mechanism may explain why Lys and GO do not react to form a related product. Preliminary analyses show that HML is formed at higher concentrations than CEL from Lys methyl ester and MGO. No Schiff bases or their hydroxylic precursors were identified as reaction products. In their reactions with Lys, GO and MGO are likely to act both as chemical oxidants on the terminal aldehyde group to a carboxylic group (i.e., R-CHO to R-COOH) and as chemical reductors on labile Schiff bases (R-CH=N-R to R-CH₂-NH-R) presumably via disproportionation and hydride transfer. Our study shows that free non-proteinic Lys reacts with GO and MGO to form CML, CEL and HML in very low yield. Whether proteinic Lys also reacts with MGO to form HML residues in proteins remains to be investigated. The physiological occurrence and concentration of HML in biological fluids and tissues and its relation to CML and CEL are elusive and warrant further investigations in health and disease. Chemical synthesis and structural characterization of HML are expected to advance and accelerate the scientific research in this topic.

Hypoxia Enhances HIF1α Transcription Activity by Upregulating KDM4A and Mediating H3K9me3, Thus Inducing Ferroptosis Resistance in Cervical Cancer Cells

Objective

Cervical cancer (CC) is a prevalent cancer in women. Hypoxia plays a critical role in CC cell ferroptosis resistance. This study explored the mechanism of hypoxia in CC cell ferroptosis resistance by regulating HIF1α/KDM4A/H3K9me3.

Methods

Cultured SiHa and Hela cells were exposed to CoCl2 and treated with Erastin. Cell viability was detected by MTT assay, and concentrations of iron ion, MDA and GSH were determined using corresponding kits. Expressions of KDM4A, HIF1α, TfR1, DMT1, and H3k9me3 were detected by RT-qPCR, Western blot, and ChIP assay. The correlation of KDM4A and HIF1α was analyzed on Oncomine, UALCAN, and Starbase. CC cells were co-transfected with shKDM4A or/and pcDNA3.1-HIF1α. Iron uptake and release were assessed using the isotopic tracer method. The binding relationship between HIF1α and HRE sequence was verified by dual-luciferase assay.

Results

Cell viability and GSH were decreased while iron concentration, MDA, KDM4A, and HIF1α levels were increased in hypoxia conditions. The 2-h hypoxia induced ferroptosis resistance. KDM4A and HIF1α were highly-expressed in CC tissues and positively correlated with each other. KDM4A knockdown attenuated cell resistance to Erastin, increased H3K9me3 level in the HIF1α promoter region, and downregulated HIF1α transcription and translation. H3K9me3 level was increased in the HIF1α promoter after hypoxia. HIF1α overexpression abrogated the function of KDM4A knockdown on ferroptosis in hypoxia conditions. Iron uptake/release and TfR1/DMT1 levels were increased after hypoxia. Hypoxia activated HRE sequence in TfR1 and DMT1 promoters.

Conclusion

Hypoxia upregulated KDM4A, enhanced HIF1α transcription, and activated HRE sequence in TfR1 and DMT1 promoters via H3K9me3, thus inducing ferroptosis resistance in CC cells.

Role of histone demethylases and histone methyltransferases in triple-negative breast cancer: Epigenetic mnemonics

Triple-negative breast cancer (TNBC) is a particularly lethal subtype of breast cancer owing to its heterogeneity, high drug resistance, poor prognosis and lack of therapeutic targets. Recent insights into the complexity of TNBC have been explained by epigenetic regulation and its ability to modulate certain oncogenes and tumour suppressor genes. This has opened an emerging area in anti-cancer therapy using epigenetic modulating drugs, highlighting the epigenetic reprogramming during tumorigenesis and tumour development. Histone methylation and demethylation are such dynamic epigenetic mechanisms mediated by histone methyltransferases (HMTs) and histone demethylases (HDMs), respectively. The interplay between HMTs and HDMs in histone methylation extrapolates their viability as druggable epigenetic targets in TNBC. In this review, we aim to summarize recent progress in the field of epigenetics focusing on HMTs and HDMs in TNBC development and their potential use in targeted therapy for TNBC management.

Novel Therapeutic Targets and Immune Dysfunction in Malignant Pleural Mesothelioma

Advances in the treatment of malignant pleural mesothelioma (MPM) have been disappointing, despite the apparent need for new therapeutic options for this rare and devastating cancer. Drug resistance is common and surgical intervention has brought benefits only to a subset of patients. MPM is a heterogenous disease with a surprisingly low mutation rate and recent sequencing efforts have confirmed alterations in a limited number of tumor suppressors that do not provide apparent insights into the molecular mechanisms that drive this malignancy. There is increasing evidence that epigenetic regulation leads to immune evasion and transformation in MPM. Further, the low efficacy of immune checkpoint inhibitors is consistent with a suppression of genes involved in the anti-tumor immune response. We review three promising emerging therapeutic targets (STAT3, KDM4A, heparanase) and highlight their potential effects on the immune response.

ELF3-AS1 contributes to gastric cancer progression by binding to hnRNPK and induces thrombocytosis in peripheral blood

Numerous studies have reported that a variety of long noncoding RNAs (lncRNAs) can promote the proliferation, invasion, and migration of different tumor cells. However, different lncRNAs regulate cell functions in various forms, and the exact mechanisms are not clear. Here, we investigated the effect of the lncRNA ELF3-AS1 on gastric cancer (GC) cell function and explored the exact mechanism. Quantitative real-time polymerase chain reaction was used to detect the expression of ELF3-AS1 in GC tissues and adjacent nontumor tissues. Knockdown and overexpression of ELF3-AS1 was used to detect the effect of ELF3-AS1 on cell function. Potential downstream target genes were identified using RNA transcriptome sequencing, while RNA immunoprecipitation, chromatin immunoprecipitation, and Western blotting were performed to explore the tumor promotion mechanisms of ELF3-AS1. We observed that ELF3-AS1 was highly expressed in GC tissues, and high ELF3-AS1 expression predicted poor prognosis. The knockdown of ELF3-AS1 significantly inhibited cell proliferation, migration, and epithelial-mesenchymal transition and promoted apoptosis. Mechanistic investigations revealed that ELF3-AS1 may regulate the downstream target gene, C-C motif chemokine 20, by binding with the RNA-binding protein hnRNPK. Additionally, we found that high ELF3-AS1 expression was associated with thrombocytosis. Interleukin-6 and thrombopoietin may be involved in ELF3-AS1-induced paraneoplastic thrombocytosis. Together, our results demonstrate that aberrantly expressed ELF3-AS1 in GC may play important roles in oncogenesis and progression and is expected to become a new target for the diagnosis and treatment of GC.

Essential role of the histone lysine demethylase KDM4A in the biology of malignant pleural mesothelioma (MPM)

BACKGROUND

Malignant pleural mesothelioma (MPM) is a highly aggressive cancer with a dismal prognosis. There is increasing interest in targeting chromatin regulatory pathways in difficult-to-treat cancers. In preliminary studies, we found that KDM4A (lysine-specific histone demethylase 4) was overexpressed in MPM.

METHODS

KDM4A protein expression was determined by immunohistochemistry or immunoblotting. Functional inhibition of KDM4A by targeted knockdown and small molecule drugs was correlated to cell growth using cell lines and a xenograft mouse model. Gene expression profiling was performed to identify KDM4A-dependent signature pathways.

RESULTS

Levels of KDM4A were found to be significantly elevated in MPM patients compared to normal mesothelial tissue. Inhibiting the enzyme activity efficiently reduced cell growth in vitro and reduced tumour growth in vivo. KDM4A inhibitor-induced apoptosis was further enhanced by the BH3 mimetic navitoclax. KDM4A expression was associated with pathways involved in cell growth and DNA repair. Interestingly, inhibitors of the DNA damage and replication checkpoint regulators CHK1 (prexasertib) and WEE1 (adavosertib) within the DNA double-strand break repair pathway, cooperated in the inhibition of cell growth.

CONCLUSIONS

The results establish a novel and essential role for KDM4A in growth in preclinical models of MPM and identify potential therapeutic approaches to target KDM4A-dependent vulnerabilities.

Long non-coding RNA KIKAT/LINC01061 as a novel epigenetic regulator that relocates KDM4A on chromatin and modulates viral reactivation

KDM4A is a histone lysine demethylase that has been described as an oncogene in various types of cancer. The importance of KDM4A-mediated epigenetic regulation in tumorigenesis is just emerging. Here, by using Kaposi’s sarcoma associated herpesvirus (KSHV) as a screening model, we identified 6 oncogenic virus-induced long non-coding RNAs (lncRNAs) with the potential to open chromatin. RNA immunoprecipitation revealed KSHV-induced KDM4A-associated transcript (KIKAT)/LINC01061 as a binding partner of KDM4A. Integrated ChIP-seq and RNA-seq analysis showed that the KIKAT/LINC01061 interaction may mediate relocalization of KDM4A from the transcription start site (TSS) of the AMOT promoter region and transactivation of AMOT, an angiostatin binding protein that regulates endothelial cell migration. Knockdown of AMOT diminished the migration ability of uninfected SLK and iSLK-BAC16 cells in response to KIKAT/LINC01061 overexpression. Thus, we conclude that KIKAT/LINC01061 triggered shifting of KDM4A as a potential epigenetic mechanism regulating gene transactivation. Dysregulation of KIKAT/LINC01061 expression may represent a novel pathological mechanism contributing to KDM4A oncogenicity.

Epigenetic regulation of chromatin structure and gene function connects genotype to phenotype and diseases. Long non-coding RNA (lncRNA) is emerging as a novel type of epigenetic regulator exhibiting diverse biological functions. Aberrant lncRNA expression is associated with various diseases, including cancer. The widespread epigenetic changes that occur during the latent-to-lytic switch of herpes virus life cycle make it an attractive model to study epigenetic regulation. Using Kaposi’s sarcoma associated herpesvirus (KSHV) as a model, we screened the epigenetic function of lncRNAs whose expression was induced by reactivation of this oncogenic virus. KIKAT/LINC01061 was identified as a novel histone lysine-specific demethylase 4A (KDM4A) interacting lncRNA. KDM4A is the first identified histone trimethyl demethylase that has been demonstrated as an oncogene in various cancers. Our data reveal a novel lncRNA-mediated regulation of the epigenetic function of KDM4A and demonstrate this lncRNA-chromatin modifier interaction may serve as a potential target in cancer therapy.

2-Oxoglutarate-dependent dioxygenases in cancer

2-Oxoglutarate-dependent dioxygenases (2OGDDs) are a superfamily of enzymes that play diverse roles in many biological processes, including regulation of hypoxia-inducible factor-mediated adaptation to hypoxia, extracellular matrix formation, epigenetic regulation of gene transcription and the reprogramming of cellular metabolism. 2OGDDs all require oxygen, reduced iron and 2-oxoglutarate (also known as α-ketoglutarate) to function, although their affinities for each of these co-substrates, and hence their sensitivity to depletion of specific co-substrates, varies widely. Numerous 2OGDDs are recurrently dysregulated in cancer. Moreover, cancer-specific metabolic changes, such as those that occur subsequent to mutations in the genes encoding succinate dehydrogenase, fumarate hydratase or isocitrate dehydrogenase, can dysregulate specific 2OGDDs. This latter observation suggests that the role of 2OGDDs in cancer extends beyond cancers that harbour mutations in the genes encoding members of the 2OGDD superfamily. Herein, we review the regulation of 2OGDDs in normal cells and how that regulation is corrupted in cancer.

microRNA-139-3p Inhibits Malignant Behaviors of Laryngeal Cancer Cells via the KDM5B/SOX2 Axis and the Wnt/β-Catenin Pathway

Background

Laryngeal cancer (LCA) is a common head and neck cancer. Lysine demethylase 5B (KDM5B) knockdown is expected as a new target for cancer prevention. We investigated the molecular mechanism of KDM5B in LCA.

Materials and Methods

The levels of KDM5B, microRNA (miR)-139-3p and high-mobility-group box 2 (SOX2) in LCA tissues and cells, normal tissues and cells were detected. The effect of KDM5B on LCA was evaluated. The upstream miR of KDM5B and the downstream gene and pathway of KDM5B were predicted and their effects on LCA were analyzed. The Wnt/β-catenin pathway-specific activator agonist was delivered into LCA cells expressing miR-139-3p mimic to evaluate the role of the Wnt/β-catenin pathway.

Results

KDM5B was highly expressed in LCA, and inhibition of KDM5B suppressed LCA progression. miR-139-3p, downregulated in LCA tissues, was a regulatory miR of KDM5B. Overexpression of miR-139-3p significantly inhibited the malignant biological behaviors of LCA cells. KDM5B promoted SOX2 expression via histone demethylation. SOX2 was highly expressed in LCA, and overexpression of SOX2 promoted LCA progression by inducing the Wnt/β-catenin pathway. Activated Wnt/β-catenin pathway attenuated the inhibitory effect of miR-139-3p mimic on the malignant biological behaviors of LCA cells.

Conclusion

miR-139-3p overexpression inhibited LCA development via regulating the KDM5B/SOX2 axis and inhibiting the Wnt/β-catenin pathway.

Catalysis by the JmjC histone demethylase KDM4A integrates substrate dynamics, correlated motions and molecular orbital control

The N^ε-methyl lysine status of histones is important in the regulation of eukaryotic transcription. The Fe(ii) and 2-oxoglutarate (2OG) -dependent JmjC domain enzymes are the largest family of histone N^ε-methyl lysine demethylases (KDMs). The human KDM4 subfamily of JmjC KDMs is linked with multiple cancers and some of its members are medicinal chemistry targets. We describe the use of combined molecular dynamics (MD) and Quantum Mechanical/Molecular Mechanical (QM/MM) methods to study the mechanism of KDM4A, which catalyzes demethylation of both tri- and di-methylated forms of histone H3 at K9 and K36. The results show that the oxygen activation at the active site of KDM4A is optimized towards the generation of the reactive Fe(iv)-oxo intermediate. Factors including the substrate binding mode, correlated motions of the protein and histone substrates, and molecular orbital control synergistically contribute to the reactivity of the Fe(iv)-oxo intermediate. In silico substitutions were performed to investigate the roles of residues (Lys241, Tyr177, and Asn290) in substrate orientation. The Lys241Ala substitution abolishes activity due to altered substrate orientation consistent with reported experimental studies. Calculations with a macrocyclic peptide substrate analogue reveal that induced conformational changes/correlated motions in KDM4A are sequence-specific in a manner that influences substrate binding affinity. Second sphere residues, such as Ser288 and Thr289, may contribute to KDM4A catalysis by correlated motions with active site residues. Residues that stabilize key intermediates, and which are predicted to be involved in correlated motions with other residues in the second sphere and beyond, are shown to be different in KDM4A compared to those in another JmjC KDM (PHF8), which acts on H3K9 di- and mono-methylated forms, suggesting that allosteric type inhibition is of interest from the perspective of developing selective JmjC KDM inhibitors.

The second sphere residues and regions of the protein in histone demethylase enzymes that makes correlated motion with the active site contribute to efficient catalysis.

RFX5 promotes the progression of hepatocellular carcinoma through transcriptional activation of KDM4A

Regulatory factor X-5 (RFX5) represents a key transcription regulator of MHCII gene expression in the immune system. This study aims to explore the molecular mechanisms and biological significance of RFX5. Firstly, by analyzing ENCODE chromatin immunoprecipitation (ChIP)-seq in HepG2 and TCGA RNA-seq data, we discovered lysine-specific demethylase 4A (KDM4A), also named JMJD2A, to be a major downstream target gene of RFX5. Moreover, RFX5 was verified to bind directly to the KDM4A's promoter region and sequentially promoted its transcription determined by the ChIP-PCR assay and luciferase assay. In addition, RFX5-dependent regulation of KDM4A was demonstrated in HCC. Compared with adjacent non-tumor tissues, the expression levels of KDM4A were significantly raised in HCC tumor tissues. Notably, elevated levels of KDM4A were strongly correlated with HCC patient prognosis. Functionally, KDM4A overexpression largely rescued the growth inhibitory effects of RFX5 deletion, highlighting KDM4A as a downstream effector of RFX5. Mechanistically, the RFX5-KDM4A pathway promoted the progression of the cell cycle from G0/G1 to S phase and was protective against cell apoptosis through regulation of p53 and its downstream genes in HCC. In conclusion, RFX5 could promote HCC progression via transcriptionally activating KDM4A expression.

A New Family of Jumonji C Domain-Containing KDM Inhibitors Inspired by Natural Product Purpurogallin

Aberrant epigenetic modifications are involved in cancer development. Jumonji C domain-containing histone lysine demethylases (KDMs) are found mainly up-regulated in breast, prostate, and colon cancer. Currently, growing interest is focusing on the identification and development of new inhibitors able to block the activity of KDMs and thus reduce tumor progression. KDM4A is known to play a role in several cellular physiological processes, and was recently found overexpressed in a number of pathological states, including cancer. In this work, starting from the structure of purpurogallin 9aa, previously identified as a natural KDM4A inhibitor, we synthesized two main sets of compound derivatives in order to improve their inhibitory activity against KDM4A in vitro and in cells, as well as their antitumor action. Based on the hypothetical biogenesis of the 5-oxo-5H-benzo[7]annulene skeleton of the natural product purpurogallin (Salfeld, 1960; Horner et al., 1961; Dürckheimer and Paulus, 1985; Tanaka et al., 2002; Yanase et al., 2005) the pyrogallol and catechol units were first combined with structural modifications at different positions of the aryl ring using enzyme-mediated oxidative conditions, generating a series of benzotropolone analogs. Two of the synthetic analogs of purpurogallin, 9ac and 9bc, showed an efficient inhibition (50 and 80%) of KDM4A in enzymatic assays and in cells by increasing levels of its specific targets, H3K9me3/2 and H3K36me3. However, these two compounds/derivatives did not induce cell death. We then synthesized a further set of analogs of these two compounds with greater structural diversification. The most potent of these analogs, 9bf, displayed the highest KDM4A inhibitory enzymatic activity in vitro (IC₅₀ of 10.1 and 24.37 μM) in colon cancer cells, and the strongest antitumor action in several solid and hematological human cancer cell lines with no toxic effect in normal cells. Our findings suggest that further development of this compound and its derivatives may lead to the identification of new therapeutic antitumor agents acting through inhibition of KDM4A.

JMJD2A sensitizes gastric cancer to chemotherapy by cooperating with CCDC8

BACKGROUND

Jumonji domain-containing protein 2A (JMJD2A) of the JMJD2 family of histone lysine demethylases has been implicated in tumorigenesis. However, its expression and role in gastric cancer (GC) drug resistance remain unknown. Here, we investigated the role of JMJD2A in GC chemotherapeutic susceptibility and its clinical relevance in GC.

METHODS

We selected 12 relevant genes from previously identified gene signatures that can predict GC susceptibility to docetaxel, cisplatin, and S-1 (DCS) therapy. Each gene was knocked down using siRNA in GC cell lines, and cell viability assays were performed. JMJD2A expression in GC cell lines and tissues was assessed using qRT-PCR and immunohistochemistry, respectively. A JMJD2A downstream target related to drug susceptibility was examined using whole-gene expression array and immunoprecipitation.

RESULTS

Among the 12 candidate genes, down-regulation of JMJD2A showed the maximum effect on GC susceptibility to anti-cancer drugs and increased the IC₅₀ values for 5-FU, cisplatin, and docetaxel 15.3-, 2.7-, and 4.0-fold, respectively. JMJD2A was universally expressed in 12 GC cell lines, and its overexpression in GC tissue was positively correlated with tumor regression in 34 DCS-treated patients. A whole-gene expression array of JMJD2A-knockdown GC cells demonstrated a significant decrease in the expression of pro-apoptotic coiled-coil domain containing 8 (CCDC8), a downstream target of JMJD2A. Direct interaction between CCDC8 and JMJD2A was verified using immunoprecipitation. CCDC8 inhibition restored drug resistance to docetaxel, cisplatin, and S-1.

CONCLUSIONS

Our results indicate that JMJD2A is a novel epigenetic factor affecting GC chemotherapeutic susceptibility, and JMJD2A/CCDC8 is a potential GC therapeutic target.

Isoform-Specific Lysine Methylation of RORα2 by SETD7 Is Required for Association of the TIP60 Coactivator Complex in Prostate Cancer Progression

The retinoid acid-related orphan receptor α (RORα), a member of the orphan nuclear receptor superfamily, functions as an unknown ligand-dependent transcription factor. RORα was shown to regulate a broad array of physiological processes such as Purkinje cell development in the cerebellum, circadian rhythm, lipid and bone metabolism, inhibition of inflammation, and anti-apoptosis. The human RORα gene encodes at least four distinct isoforms (RORα1, -2, -3, -4), which differ only in their N-terminal domain (NTD). Two isoforms, RORα2 and 3, are not expressed in mice, whereas RORα1 and 4 are expressed both in mice and humans. In the present study, we identified the specific NTD of RORα2 that enhances prostate tumor progression and proliferation via lysine methylation-mediated recruitment of coactivator complex pontin/Tip60. Upregulation of the RORα2 isoform in prostate cancers putatively promotes tumor formation and progression. Furthermore, binding between coactivator complex and RORα2 is increased by lysine methylation of RORα2 because methylation permits subsequent interaction with binding partners. This methylation-dependent activation is performed by SET domain containing 7 (SETD7) methyltransferase, inducing the oncogenic potential of RORα2. Thus, post-translational lysine methylation of RORα2 modulates oncogenic function of RORα2 in prostate cancer. Exploration of the post-translational modifications of RORα2 provides new avenues for the development of tumor-suppressive therapeutic agents through modulating the human isoform-specific tumorigenic role of RORα2.

Transcriptional Regulation of Genes by Ikaros Tumor Suppressor in Acute Lymphoblastic Leukemia

Regulation of oncogenic gene expression by transcription factors that function as tumor suppressors is one of the major mechanisms that regulate leukemogenesis. Understanding this complex process is essential for explaining the pathogenesis of leukemia as well as developing targeted therapies. Here, we provide an overview of the role of Ikaros tumor suppressor and its role in regulation of gene transcription in acute leukemia. Ikaros (IKZF1) is a DNA-binding protein that functions as a master regulator of hematopoiesis and the immune system, as well as a tumor suppressor in acute lymphoblastic leukemia (ALL). Genetic alteration or functional inactivation of Ikaros results in the development of high-risk leukemia. Ikaros binds to the specific consensus binding motif at upstream regulatory elements of its target genes, recruits chromatin-remodeling complexes and activates or represses transcription via chromatin remodeling. Over the last twenty years, a large number of Ikaros target genes have been identified, and the role of Ikaros in the regulation of their expression provided insight into the mechanisms of Ikaros tumor suppressor function in leukemia. Here we summarize the role of Ikaros in the regulation of the expression of the genes whose function is critical for cellular proliferation, development, and progression of acute lymphoblastic leukemia.

Identification of eQTLs and sQTLs associated with meat quality in beef

BACKGROUND

Transcription has a substantial genetic control and genetic dissection of gene expression could help us understand the genetic architecture of complex phenotypes such as meat quality in cattle. The objectives of the present research were: 1) to perform eQTL and sQTL mapping analyses for meat quality traits in longissimus dorsi muscle; 2) to uncover genes whose expression is influenced by local or distant genetic variation; 3) to identify expression and splicing hot spots; and 4) to uncover genomic regions affecting the expression of multiple genes.

RESULTS

Eighty steers were selected for phenotyping, genotyping and RNA-seq evaluation. A panel of traits related to meat quality was recorded in longissimus dorsi muscle. Information on 112,042 SNPs and expression data on 8588 autosomal genes and 87,770 exons from 8467 genes were included in an expression and splicing quantitative trait loci (QTL) mapping (eQTL and sQTL, respectively). A gene, exon and isoform differential expression analysis previously carried out in this population identified 1352 genes, referred to as DEG, as explaining part of the variability associated with meat quality traits. The eQTL and sQTL mapping was performed using a linear regression model in the R package Matrix eQTL. Genotype and year of birth were included as fixed effects, and population structure was accounted for by including as a covariate the first PC from a PCA analysis on genotypic data. The identified QTLs were classified as cis or trans using 1 Mb as the maximum distance between the associated SNP and the gene being analyzed. A total of 8377 eQTLs were identified, including 75.6% trans, 10.4% cis, 12.5% DEG trans and 1.5% DEG cis; while 11,929 sQTLs were uncovered: 66.1% trans, 16.9% DEG trans, 14% cis and 3% DEG cis. Twenty-seven expression master regulators and 13 splicing master regulators were identified and were classified as membrane-associated or cytoskeletal proteins, transcription factors or DNA methylases. These genes could control the expression of other genes through cell signaling or by a direct transcriptional activation/repression mechanism.

CONCLUSION

In the present analysis, we show that eQTL and sQTL mapping makes possible positional identification of gene and isoform expression regulators.

Targeting the RNA Polymerase I Transcription for Cancer Therapy Comes of Age

Transcription of the ribosomal RNA genes (rDNA) that encode the three largest ribosomal RNAs (rRNA), is mediated by RNA Polymerase I (Pol I) and is a key regulatory step for ribosomal biogenesis. Although it has been reported over a century ago that the number and size of nucleoli, the site of ribosome biogenesis, are increased in cancer cells, the significance of this observation for cancer etiology was not understood. The realization that the increase in rRNA expression has an active role in cancer progression, not only through increased protein synthesis and thus proliferative capacity but also through control of cellular check points and chromatin structure, has opened up new therapeutic avenues for the treatment of cancer through direct targeting of Pol I transcription. In this review, we discuss the rational of targeting Pol I transcription for the treatment of cancer; review the current cancer therapeutics that target Pol I transcription and discuss the development of novel Pol I-specific inhibitors, their therapeutic potential, challenges and future prospects.

KLF8 overexpression promotes the growth of human lung cancer cells by promoting the expression of JMJD2A

Background

Non-small-cell lung cancer (lung cancer) has become one of the leading causes worldwide and the underlying mechanism is not fully understood. The transcriptional factor Kruppel like factor 8 (KLF8) is involved in the initiation, progression, transformation, and metastasis of diverse cancers. However, the roles of KLF8 in human non-small cell lung cancer remain unknown.

Methods

CCK-8 kit and colony formation assay were performed to determine the cell growth of lung cancer cells. Flow cytometry analysis was used to evaluate apoptosis and cell cycle of lung cancer cells. Luciferase reporter assay was used to examine the activation of JMJD2A promoter by KLF8. Chromatin immunoprecipitation assay was performed to evaluate the binding of KLF8 to JMJD2A promoter. Western blot and polymerase chain reaction were applied to analyze the expression of interested genes.

Results

The mRNA and protein levels of KLF8 in human non-small cell lung cancer tissues were overexpressed compared with the non-cancer tissues. KLF8 was knocked down with lentivirus-mediated short-hairpin RNA (shRNA) in human lung cancer cells (A549 and H1299 cells). The phenotypic results showed that KLF8 knockdown decreased the proliferation rate and colony formation of lung cancer cells. By contrast, lentivirus-mediated KLF8 overexpression promoted the growth of lung cancer cells (A549 and H1299 cells) and non-cancerous bronchial epithelial cell line BEAS-2B. Next, we showed that KLF8 regulated cell cycle at the G0 phase but not regulates cellular apoptosis of lung cancer cells. KLF8 regulated the expression of the cell cycle regulators P21 and CDK4 in a JMJD2A-dependent manner and JMJD2A knockdown significantly blocked the functions of KLF8 in regulating cell cycle and proliferation of lung cancer cells. Finally, we observed that KLF8 bound the promoter of JMJD2A and facilitated the expression of JMJD2A.

Conclusions

Our evidence demonstrated that KLF8 upregulation in human lung cancer promotes the cell proliferation and colony formation of lung cancer cells. KLF8 binds to the promoter of JMJD2A and subsequently regulates the expression of P21 and CDK4, which contributes to the regulation of cell cycle by KLF8. KLF8 may serve as a target for the treatment of human lung cancer.

The Clinically Used Iron Chelator Deferasirox Is an Inhibitor of Epigenetic JumonjiC Domain-Containing Histone Demethylases

Fe(II)- and 2-oxoglutarate (2OG)-dependent JumonjiC domain-containing histone demethylases (JmjC KDMs) are "epigenetic eraser" enzymes involved in the regulation of gene expression and are emerging drug targets in oncology. We screened a set of clinically used iron chelators and report that they potently inhibit JMJD2A (KDM4A) in vitro. Mode of action investigations revealed that one compound, deferasirox, is a bona fide active site-binding inhibitor as shown by kinetic and spectroscopic studies. Synthesis of derivatives with improved cell permeability resulted in significant upregulation of histone trimethylation and potent cancer cell growth inhibition. Deferasirox was also found to inhibit human 2OG-dependent hypoxia inducible factor prolyl hydroxylase activity. Therapeutic effects of clinically used deferasirox may thus involve transcriptional regulation through 2OG oxygenase inhibition. Deferasirox might provide a useful starting point for the development of novel anticancer drugs targeting 2OG oxygenases and a valuable tool compound for investigations of KDM function.

The KDM4A/KDM4C/NF-κB and WDR5 epigenetic cascade regulates the activation of B cells

T follicular helper (Tfh) cell-derived signals promote activation and proliferation of antigen-primed B cells. It remains unclear whether epigenetic regulation is involved in the B cell responses to Tfh cell-derived signals. Here, we demonstrate that Tfh cell-mimicking signals induce the expression of histone demethylases KDM4A and KDM4C, and the concomitant global down-regulation of their substrates, H3K9me3/me2, in B cells. Depletion of KDM4A and KDM4C potentiates B cell activation and proliferation in response to Tfh cell-derived signals. ChIP-seq and de novo motif analysis reveals NF-κB p65 as a binding partner of KDM4A and KDM4C. Their co-targeting to Wdr5, a MLL complex member promoting H3K4 methylation, up-regulates cell cycle inhibitors Cdkn2c and Cdkn3. Thus, Tfh cell-derived signals trigger KDM4A/KDM4C - WDR5 - Cdkn2c/Cdkn3 cascade in vitro, an epigenetic mechanism regulating proper proliferation of activated B cells. This pathway is dysregulated in B cells from systemic lupus erythematosus patients and may represent a pathological link.

Circ_SPECC1 enhances the inhibition of miR-526b on downstream KDM4A/YAP1 pathway to regulate the growth and invasion of gastric cancer cells

Gastric cancer (GC) is a common malignant tumor, and many studies have shown that circular RNAs (circRNAs) play important roles in the progress of GC. This study showed that circ_SPECC1 was down-regulated in various GC cell lines, significantly inhibited GC cell proliferation and invasion, and promote apoptosis, which might play an anti-oncogene role. Circ_SPECC1 was mainly located in the cytoplasm, and its sequence contained multiple potential binding sites of miR-526b. Pull-down experiments with biotinylated miR-526b mimics and circ_SPECC1 probe showed that they could enrich each other. RIP experiments found hat anti-AGO2 antibody could significantly enrich circ_SPECC1. Further dual luciferase reporter gene assay also confirmed that miR-526b could bind directly to circ_SPECC1. miR-526b was also down-regulated in GC cells, and one of its important target genes was KDM4A. Both circ_SPECC1 and miR-526b inhibited the expression of KDM4A and its downstream effector YAP1, but miR-526b inhibitors terminated the above-mentioned inhibition of circ_SPECC1, and KDM4A overexpression reversed the inhibition of circ_SPECC1 and miR-526b on YAP1 expression. Both miR-526b and KDM4A siRNA inhibited GC cell proliferation and invasion, and promote apoptosis; KDM4A overexpression had the opposite effects, and significantly blocked the regulation of miR-526b on cell growth and invasion. Therefore, circ_SPECC1 can enhance miR-526b inhibitory effect on downstream KDM4A/YAP1 pathway by adsorbing it, thus inhibiting GC cell growth and invasion. These findings enrich the mechanism of circRNAs in GC and will provide more new targets for the prevention and treatment of GC.

Dynamic regulation of epigenetic demethylation by oxygen availability and cellular redox

The chromatin structure of the mammalian genome must facilitate both precisely-controlled DNA replication together with tightly-regulated gene transcription. This necessarily involves complex mechanisms and processes which remain poorly understood. It has long been recognised that the epigenetic landscape becomes established during embryonic development and acts to specify and determine cell fate. In addition, the chromatin structure is highly dynamic and allows for both cellular reprogramming and homeostatic modulation of cell function. In this respect, the functions of epigenetic "erasers", which act to remove covalently-linked epigenetic modifications from DNA and histones are critical. The enzymatic activities of the TET and JmjC protein families have been identified as demethylases which act to remove methyl groups from DNA and histones, respectively. Further, they are characterised as members of the Fe(II)- and 2-oxoglutarate-dependent dioxygenase superfamily. This provides the intriguing possibility that their enzymatic activities may be modulated by cellular metabolism, oxygen availability and redox-based mechanisms, all of which are likely to display dynamic cell- and tissue-specific patterns of flux. Here we discuss the current evidence for such [O₂]- and redox-dependent regulation of the TET and Jmjc demethylases and the potential physiological and pathophysiological functional consequences of such regulation.

Jumonji C Demethylases in Cellular Senescence

Senescence is a stable cell cycle arrest that is either tumor suppressive or tumor promoting depending on context. Epigenetic changes such as histone methylation are known to affect both the induction and suppression of senescence by altering expression of genes that regulate the cell cycle and the senescence-associated secretory phenotype. A conserved group of proteins containing a Jumonji C (JmjC) domain alter chromatin state, and therefore gene expression, by demethylating histones. Here, we will discuss what is currently known about JmjC demethylases in the induction of senescence, and how these enzymes suppress senescence to contribute to tumorigenesis.

CXCR7/CXCR4 heterodimer-induced histone demethylation: a new mechanism of colorectal tumorigenesis

Both chemokine receptors (CXCRs) 7 and 4 can facilitate immune cell migration and mediate a vast array of physiological and pathological events. Herein we report, in both human and animal studies, that these two CXCRs can form heterodimers in vivo and promote colorectal tumorigenesis through histone demethylation. Compared with adjacent non-neoplastic tissue, human colorectal cancer (CRC) tissue showed a significant higher expression of CXCR4 and CXCR7, which was colocalized in the cancer cell epithelium. The CXCR/CXCR4 heterodimerization was associated with increased histone demethylase JMJD2A. Villin-CXCR7-CXCR4 transgenic mice demonstrated a greater degree of exacerbated colitis and tumorigenesis than villin-CXCR7 and villin-CXCR4 mice. The CXCR7/CXCR4 heterodimerization also promoted APC mutation-driven colorectal tumorigenesis in APC^Min/+/villin-CXCR7-CXCR4 mice. Further analysis showed that the CXCR7/CXCR4 heterodimer induced nuclear βarr1 recruitment and histone demethylase JMJD2A, leading to histone demethylation and resulting in transcription of inflammatory factors and oncogenes. This study uncovered a novel mechanism of colorectal tumorigenesis through the CXCR7/CXCR4 heterodimer-induced histone demethylation. Inhibition of CXCR7/CXCR4 heterodimer-induced histone demethylation could be an effective strategy for the prevention and treatment of colorectal cancer.

Ubiquitin Regulation: The Histone Modifying Enzyme's Story

Histone post-translational modifications influence many fundamental cellular events by regulating chromatin structure and gene transcriptional activity. These modifications are highly dynamic and tightly controlled, with many enzymes devoted to the addition and removal of these modifications. Interestingly, these modifying enzymes are themselves fine-tuned and precisely regulated at the level of protein turnover by ubiquitin-proteasomal processing. Here, we focus on recent progress centered on the mechanisms regulating ubiquitination of histone modifying enzymes, including ubiquitin proteasomal degradation and the reverse process of deubiquitination. We will also discuss the potential pathophysiological significance of these processes.

Lung Cancer Therapy Targeting Histone Methylation: Opportunities and Challenges

Lung cancer is one of the most common malignancies. In spite of the progress made in past decades, further studies to improve current therapy for lung cancer are required. Dynamically controlled by methyltransferases and demethylases, methylation of lysine and arginine residues on histone proteins regulates chromatin organization and thereby gene transcription. Aberrant alterations of histone methylation have been demonstrated to be associated with the progress of multiple cancers including lung cancer. Inhibitors of methyltransferases and demethylases have exhibited anti-tumor activities in lung cancer, and multiple lead candidates are under clinical trials. Here, we summarize how histone methylation functions in lung cancer, highlighting most recent progresses in small molecular inhibitors for lung cancer treatment.

Small molecule KDM4s inhibitors as anti-cancer agents

Histone demethylation is a vital process in epigenetic regulation of gene expression. A number of histone demethylases are present to control the methylated states of histone. Among these enzymes, KDM4s are one subfamily of JmjC KDMs and play important roles in both normal and cancer cells. The discovery of KDM4s inhibitors is a potential therapeutic strategy against different diseases including cancer. Here, we summarize the development of KDM4s inhibitors and some related pharmaceutical information to provide an update of recent progress in KDM4s inhibitors.

CTCF-KDM4A complex correlates with histone modifications that negatively regulate CHD5 gene expression in cancer cell lines

Histone demethylase KDM4A is involved in H3K9me3 and H3K36me3 demethylation, which are epigenetic modifications associated with gene silencing and RNA Polymerase II elongation, respectively. KDM4A is abnormally expressed in cancer, affecting the expression of multiple targets, such as the CHD5 gene. This enzyme localizes at the first intron of CHD5, and the dissociation of KDM4A increases gene expression. In vitro assays showed that KDM4A-mediated demethylation is enhanced in the presence of CTCF, suggesting that CTCF could increase its enzymatic activity in vivo, however the specific mechanism by which CTCF and KDM4A might be involved in the CHD5 gene repression is poorly understood. Here, we show that CTCF and KDM4A form a protein complex, which is recruited into the first intron of CHD5. This is related to a decrease in H3K36me3/2 histone marks and is associated with its transcriptional downregulation. Depletion of CTCF or KDM4A by siRNA, triggered the reactivation of CHD5 expression, suggesting that both proteins are involved in the negative regulation of this gene. Furthermore, the knockout of KDM4A restored the CHD5 expression and H3K36me3 and H3K36me2 histone marks. Such mechanism acts independently of CHD5 promoter DNA methylation. Our findings support a novel mechanism of epigenetic repression at the gene body that does not involve promoter silencing.

Novel Loci Associated With Attention-Deficit/Hyperactivity Disorder Are Revealed by Leveraging Polygenic Overlap With Educational Attainment

OBJECTIVE

Attention-deficit/hyperactivity disorder (ADHD) is a common and highly heritable psychiatric condition. By exploiting the reported relationship between ADHD and educational attainment (EA), we aimed to improve discovery of ADHD-associated genetic variants and to investigate genetic overlap between these phenotypes.

METHOD

A conditional/conjunctional false discovery rate (condFDR/conjFDR) method was applied to genome-wide association study (GWAS) data on ADHD (2,064 trios, 896 cases, and 2,455 controls) and EA (n=328,917) to identify ADHD-associated loci and loci overlapping between ADHD and EA. Identified single nucleotide polymorphisms (SNPs) were tested for association in an independent population-based study of ADHD symptoms (n=17,666). Genetic correlation between ADHD and EA was estimated using LD score regression and Pearson correlation.

RESULTS

At levels of condFDR<0.01 and conjFDR<0.05, we identified 5 ADHD-associated loci, 3 of these being shared between ADHD and EA. None of these loci had been identified in the primary ADHD GWAS, demonstrating the increased power provided by the condFDR/conjFDR analysis. Leading SNPs for 4 of 5 identified regions are in introns of protein coding genes (KDM4A, MEF2C, PINK1, RUNX1T1), whereas the remaining one is an intergenic SNP on chromosome 2 at 2p24. Consistent direction of effects in the independent study of ADHD symptoms was shown for 4 of 5 identified loci. A polygenic overlap between ADHD and EA was supported by significant genetic correlation (rg=-0.403, p=7.90×10-8) and >10-fold mutual enrichment of SNPs associated with both traits.

CONCLUSION

We identified 5 novel loci associated with ADHD and provided evidence for a shared genetic basis between ADHD and EA. These findings could aid understanding of the genetic risk architecture of ADHD and its relation to EA.

F-box proteins in epigenetic regulation of cancer

Epigenetic abnormalities are now realized as important as genetic alterations in contributing to the initiation and progression of cancer. Recent advancements in the cancer epigenetics field have identified extensive alterations of the epigenetic network in human cancers, including histone modifications and DNA methylation. F-box proteins, the substrate receptors of SCF (SKP1-Cullin1-F-box protein) E3 ubiquitin ligases, can directly and indirectly affect the balance of epigenetic regulation. In this brief review, we discuss our current understanding of F-box proteins in cellular epigenetic regulation and how dysregulation of these processes contribute to cancer development.

Computational characterization of chromatin domain boundary-associated genomic elements

Topologically associated domains (TADs) are 3D genomic structures with high internal interactions that play important roles in genome compaction and gene regulation. Their genomic locations and their association with CCCTC-binding factor (CTCF)-binding sites and transcription start sites (TSSs) were recently reported. However, the relationship between TADs and other genomic elements has not been systematically evaluated. This was addressed in the present study, with a focus on the enrichment of these genomic elements and their ability to predict the TAD boundary region. We found that consensus CTCF-binding sites were strongly associated with TAD boundaries as well as with the transcription factors (TFs) Zinc finger protein (ZNF)143 and Yin Yang (YY)1. TAD boundary-associated genomic elements include DNase I-hypersensitive sites, H3K36 trimethylation, TSSs, RNA polymerase II, and TFs such as Specificity protein 1, ZNF274 and SIX homeobox 5. Computational modeling with these genomic elements suggests that they have distinct roles in TAD boundary formation. We propose a structural model of TAD boundaries based on these findings that provides a basis for studying the mechanism of chromatin structure formation and gene regulation.

Drosophila Histone Demethylase KDM4A Has Enzymatic and Non-enzymatic Roles in Controlling Heterochromatin Integrity

Eukaryotic genomes are broadly divided between gene-rich euchromatin and the highly repetitive heterochromatin domain, which is enriched for proteins critical for genome stability and transcriptional silencing. This study shows that Drosophila KDM4A (dKDM4A), previously characterized as a euchromatic histone H3 K36 demethylase and transcriptional regulator, predominantly localizes to heterochromatin and regulates heterochromatin position-effect variegation (PEV), organization of repetitive DNAs, and DNA repair. We demonstrate that dKDM4A demethylase activity is dispensable for PEV. In contrast, dKDM4A enzymatic activity is required to relocate heterochromatic double-strand breaks outside the domain, as well as for organismal survival when DNA repair is compromised. Finally, DNA damage triggers dKDM4A-dependent changes in the levels of H3K56me3, suggesting that dKDM4A demethylates this heterochromatic mark to facilitate repair. We conclude that dKDM4A, in addition to its previously characterized role in euchromatin, utilizes both enzymatic and structural mechanisms to regulate heterochromatin organization and functions.

Novel inhibitors of lysine (K)-specific Demethylase 4A with anticancer activity

Lysine (K)-specific demethylase 4A (KDM4A) is a histone demethylase that removes methyl residues from trimethylated or dimethylated histone 3 at lysines 9 and 36. Overexpression of KDM4A is found in various cancer types. To identify KDM4A inhibitors with anti-tumor functions, screening with an in vitro KDM4A enzyme activity assay was carried out. The benzylidenehydrazine analogue LDD2269 was selected, with an IC₅₀ of 6.56 μM of KDM4A enzyme inhibition, and the binding mode was investigated using in silico molecular docking. Demethylation inhibition by LDD2269 was confirmed with a cell-based assay using antibodies against methylated histone at lysines 9 and 36. HCT-116 colon cancer cell line proliferation was suppressed by LDD2269, which also interfered with soft-agar growth and migration of HCT-116 cells. AnnexinV staining and PARP cleavage experiments showed apoptosis induction by LDD2269. Derivatives of LDD2269 were synthesized and the structure-activity relationship was explored. LDD2269 is reported here as a strong inhibitor of KDM4A in in vitro and cell-based systems, with anti-tumor functions.