Deregulation of the histone demethylase JMJD2A is involved in human carcinogenesis through regulation of the G(1)/S transition

Targeting histone modifiers in bladder cancer therapy - preclinical and clinical evidence

Bladder cancer in the most advanced, muscle-invasive stage is lethal, and very limited therapeutic advances have been reported for decades. To date, cisplatin-based chemotherapy remains the first-line therapy for advanced bladder cancer. Late-line options have historically been limited. In the past few years, next-generation sequencing technology has enabled chromatin remodelling gene mutations to be characterized, showing that these alterations are more frequent in urothelial bladder carcinoma than in other cancer types. Histone modifiers have functional roles in tumour progression by modulating the expression of tumour suppressors and oncogenes and, therefore, have been considered as novel drug targets for cancer therapy. The roles of epigenetic reprogramming through histone modifications have been increasingly studied in bladder cancer, and the therapeutic efficacy of targeting those histone modifiers genetically or chemically is being assessed in preclinical studies. Results from preclinical studies in bladder cancer encouraged the investigation of some of these drugs in clinical trials, which yield mixed results. Further understanding of how alterations of histone modification mechanistically contribute to bladder cancer progression, drug resistance and tumour microenvironment remodelling will be required to facilitate clinical application of epigenetic drugs in bladder cancer.

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.

TACH101, a first-in-class pan-inhibitor of KDM4 histone demethylase

Histone lysine demethylase 4 (KDM4) is an epigenetic regulator that facilitates the transition between transcriptionally silent and active chromatin states by catalyzing the removal of methyl groups on histones H3K9, H3K36, and H1.4K26. KDM4 overamplification or dysregulation has been reported in various cancers and has been shown to drive key processes linked to tumorigenesis, such as replicative immortality, evasion of apoptosis, metastasis, DNA repair deficiency, and genomic instability. KDM4 also plays a role in epigenetic regulation of cancer stem cell renewal and has been linked to more aggressive disease and poorer clinical outcomes. The KDM4 family is composed of four main isoforms (KDM4A-D) that demonstrate functional redundancy and cross-activity; thus, selective inhibition of one isoform appears to be ineffective and pan-inhibition targeting multiple KDM4 isoforms is required. Here, we describe TACH101, a novel, small-molecule pan-inhibitor of KDM4 that selectively targets KDM4A-D with no effect on other KDM families. TACH101 demonstrated potent antiproliferative activity in cancer cell lines and organoid models derived from various histologies, including colorectal, esophageal, gastric, breast, pancreatic, and hematological malignancies. In vivo , potent inhibition of KDM4 led to efficient tumor growth inhibition and regression in several xenograft models. A reduction in the population of tumor-initiating cells was observed following TACH101 treatment. Overall, these observations demonstrate the broad applicability of TACH101 as a potential anticancer agent and support its advancement into clinical trials.

Engineering human JMJD2A tudor domains for an improved understanding of histone peptide recognition

JMJD2A is a histone lysine demethylase which recognizes and demethylates H3K9me3 and H3K36me3 residues and is overexpressed in various cancers. It utilizes a tandem tudor domain to facilitate its own recruitment to histone sites, recognizing various di- and tri-methyl lysine residues with moderate affinity. In this study, we successfully engineered the tudor domain of JMJD2A to specifically bind to H4K20me3 with a 20-fold increase of affinity and improved selectivity. To reveal the molecular basis, we performed molecular dynamics and free energy decomposition analysis on the human JMJD2A tandem tudor domains bound to H4K20me2, H4K20me3, and H3K23me3 peptides to uncover the residues and conformational changes important for the enhanced binding affinity and selectivity toward H4K20me2/3. These analyses revealed new insights into understanding chromatin reader domains recognizing histone modifications and improving binding affinity and selectivity of these domains. Furthermore, we showed that the tight binding of JMJD2A to H4K20me2/3 is not sufficient to improve the efficiency of CRISPR-CAS9 mediated homology directed repair (HDR), suggesting a complicated relationship between JMJD2A and the DNA damage response beyond binding affinity toward the H4K20me2/3 mark.

Treatment Response Predictors of Neoadjuvant Therapy for Locally Advanced Gastric Cancer: Current Status and Future Perspectives

Neoadjuvant chemotherapy (NAC) for locally advanced gastric cancer (LAGC) has been recognized as an effective therapeutic option because it is expected to improve the curative resection rate by reducing the tumor size and preventing recurrence of micrometastases. However, for patients resistant to NAC, not only will operation timing be delayed, but they will also suffer from side effects. Thus, it is crucial to develop a comprehensive strategy and select patients sensitive to NAC. However, the therapeutic effect of NAC is unpredictable due to tumor heterogeneity and a lack of predictive biomarkers for guiding the choice of optimal preoperative treatment in clinical practice. This article summarizes the related research progress on predictive biomarkers of NAC for gastric cancer. Among the many investigated biomarkers, metabolic enzymes for cytotoxic agents, nucleotide excision repair, and microsatellite instability, have shown promising results and should be assessed in prospective clinical trials. Noninvasive liquid biopsy detection, including miRNA and exosome detection, is also a promising strategy.

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.

RETRACTED: KDM4A promotes the growth of non-small cell lung cancer by mediating the expression of Myc via DLX5 through the Wnt/β-catenin signaling pathway

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the authors as they “found major problems in the data and conclusions through their later research”. 1. When the authors performed flow cytometry to detect apoptosis, the Annexin-V-coupled fluorophore they used was Fluor 647 (as described in the Methods section), which was incorrectly labelled as the Annexin-V-coupled fluorophore as FITC in their Figures (Fig. 5E, 7C and Fig. S1D). The excitation wavelengths of Alexa Fluor 647 (594/633 nm) are different from that of FITC (490 nm/520 nm), this mistake would lead to unreliability of their data. 2. The authors discovered a major error during the traceability of the antibodies used in the experiments. The primary antibody they used to detect KDM4A was actually a primary antibody for KDM6B, as evidenced by the western blots. KDM6B is a 177-kDa protein (consistent with the kDa shown in Fig. 1K and Fig. 2B), while KDM4A is a 150-kDa protein. 3. Lastly, the authors carelessly mislabeled KDM4A as KDM4B in Fig. 7. The authors and the Editors believe that the conclusions of the paper are not dependable, so we have decided to retract the paper. Apologies are offered to readers of the journal that this was not detected during the submission process.

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.

Histone demethylase KDM4A regulates adipogenic and osteogenic differentiation via epigenetic regulation of C/EBPα and canonical Wnt signaling

Epigenetic modifications play a central role in cell differentiation and development. In the current study, we have recognized lysine demethylase 4A (KDM4A) as a novel epigenetic regulator of osteoblast and adipocyte differentiation. Kdm4a expression was upregulated during osteogenesis and adipogenesis of primary marrow stromal cells and established stromal ST2 line. Overexpression of wild-type Kdm4a promoted adipogenic differentiation and blocked osteogenic differentiation of the progenitor cells. This effect was largely alleviated when the catalytically dead mutation was made. Conversely, depletion or inactivation of Kdm4a in undifferentiated progenitor cells inhibited the formation of adipocytes and promoted the differentiation of osteoblasts. Mechanism explorations showed that overexpression of Kdm4a upregulated the expression of secreted frizzled-related protein 4 (Sfrp4) and CCAAT/enhancer-binding protein α (C/ebpα). Chromatin immunoprecipitation assay demonstrated that KDM4A directly bound the promoters of Sfrp4 and C/ebpα, removed the histone methylation mark H3K9me3, and reduced DNA methylation levels of CpG in promoter regions of C/ebpα and Sfrp4. Furthermore, overexpression of Kdm4a inactivated canonical Wnt signaling. Moreover, activation of canonical Wnt signaling through silencing of Sfrp4 in ST2 attenuated the inhibition of osteogenic differentiation and the enhancement of adipogenic differentiation by KDM4A. These data have identified KDM4A as a novel regulator of osteoblast and adipocyte differentiation and suggest KDM4A inhibition as a potential therapeutic target for treating metabolic disorders such as osteoporosis.

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.

The histone demethylase JMJD2A promotes glioma cell growth via targeting Akt-mTOR signaling

Background

A number of JmjC domain-containing histone demethylases have been identified and biochemically characterized in mammalian models and humans. JMJD2A is a transcriptional co-factor and enzyme that catalyzes the demethylation of histone H3 lysine 9 and 36 (H3K9 and H3K36). Here in this study, we reported the role of JMJD2A in human glioma.

Methods

Quantitative real-time PCR and western blot were performed to analyzed JMJD2A expression in glioma. Log-rank was performed to plot the survival curve. JMJD2A was knocked or overexpressed with lentivirus. Cell proliferation and colony formation were performed to assess the effects of JMJD2A on glioma cell growth. Xenograft experiment was performed the evaluate the growth rate of glioma cells in vivo. The signaling pathway was analyzed with western blot and mTOR was inhibited with rapamycin.

Results

Quantitative real-time PCR and western blot experiments revealed higher expression of JMJD2A and lower levels of H3K9me3/H3K36me3 in glioma tissues than that in normal brain tissues. We showed that knockdown of JMJD2A expression attenuated the growth and colony formation in three lines of glioma cells (U251, T98G, and U87MG), whereas JMJD2A overexpression resulted in opposing effects. Furthermore, we performed in vivo xenograft experiments and our data demonstrated that JMJD2A knockdown reduced the growth of glioma T98G cells in vivo. Further mechanism study implicated that JMJD2A activated the Akt-mTOR pathway and promoted protein synthesis in glioma cells via promoting phosphoinositide-dependent kinase-1 (PDK1) expression. The activation of the Akt-mTOR pathway was also validated in human glioma tissues. Finally, we showed that inhibition of mTOR with rapamycin blocked the effects of JMJD2A on protein synthesis, cell proliferation and colony formation of glioma cells.

Conclusions

These findings demonstrated that JMJD2A regulated glioma growth and implicated that JMJD2A might be a promising target for intervention.

IL-6 and IL-8 are involved in JMJD2A-regulated malignancy of ovarian cancer cells

Emerging evidence shows that histone modification and its related regulators are involved in the progression and chemoresistance of ovarian cancer (OC) cells. Our present study found that the expression of Jumonji C domain-containing 2A (JMJD2A), while not JMJD2B or JMJD2C, is increased in OC cells and tissues as compared with that in their corresponding controls. Knockdown of JMJD2A can decrease proliferation while increase cisplatin (CDDP) sensitivity of OC cells. By screening the expression of cytokines involved in the progression of ovarian cancer, we found that knockdown of JMJD2A can inhibit the expression of interleukin-6 (IL-6) and IL-8 in ovarian cancer cells. Recombinant IL-6 (rIL-6) and rIL-8 can attenuate si-JMJD2A-suppressed malignancy of OC cells. Mechanistically, JMJD2A can directly bind with the promoter of IL-6 to trigger its transcription. For IL-8, JMJD2A can increase it mRNA stability in OC cells. Collectively, we revealed that JMJD2A can trigger the malignancy of OC cells via upregulation of IL-6 and IL-8. It suggested that JMJD2A might be a potential target for OC treatment and therapy.

Advances in histone demethylase KDM4 as cancer therapeutic targets

The KDM4 subfamily H3K9 histone demethylases are epigenetic regulators that control chromatin structure and gene expression by demethylating histone H3K9, H3K36, and H1.4K26. The KDM4 subfamily mainly consists of four proteins (KDM4A-D), all harboring the Jumonji C domain (JmjC) but with differential substrate specificities. KDM4A-C proteins also possess the double PHD and Tudor domains, whereas KDM4D lacks these domains. KDM4 proteins are overexpressed or deregulated in multiple cancers, cardiovascular diseases, and mental retardation and are thus potential therapeutic targets. Despite extensive efforts, however, there are very few KDM4-selective inhibitors. Defining the exact physiological and oncogenic functions of KDM4 demethylase will provide the foundation for the discovery of novel potent inhibitors. In this review, we focus on recent studies highlighting the oncogenic functions of KDM4s and the interplay between KDM4-mediated epigenetic and metabolic pathways in cancer. We also review currently available KDM4 inhibitors and discuss their potential as therapeutic agents for cancer treatment.

Epigenetics Analysis and Integrated Analysis of Multiomics Data, Including Epigenetic Data, Using Artificial Intelligence in the Era of Precision Medicine

To clarify the mechanisms of diseases, such as cancer, studies analyzing genetic mutations have been actively conducted for a long time, and a large number of achievements have already been reported. Indeed, genomic medicine is considered the core discipline of precision medicine, and currently, the clinical application of cutting-edge genomic medicine aimed at improving the prevention, diagnosis and treatment of a wide range of diseases is promoted. However, although the Human Genome Project was completed in 2003 and large-scale genetic analyses have since been accomplished worldwide with the development of next-generation sequencing (NGS), explaining the mechanism of disease onset only using genetic variation has been recognized as difficult. Meanwhile, the importance of epigenetics, which describes inheritance by mechanisms other than the genomic DNA sequence, has recently attracted attention, and, in particular, many studies have reported the involvement of epigenetic deregulation in human cancer. So far, given that genetic and epigenetic studies tend to be accomplished independently, physiological relationships between genetics and epigenetics in diseases remain almost unknown. Since this situation may be a disadvantage to developing precision medicine, the integrated understanding of genetic variation and epigenetic deregulation appears to be now critical. Importantly, the current progress of artificial intelligence (AI) technologies, such as machine learning and deep learning, is remarkable and enables multimodal analyses of big omics data. In this regard, it is important to develop a platform that can conduct multimodal analysis of medical big data using AI as this may accelerate the realization of precision medicine. In this review, we discuss the importance of genome-wide epigenetic and multiomics analyses using AI in the era of precision medicine.

Deregulation of the Histone Lysine-Specific Demethylase 1 Is Involved in Human Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and is a leading cause of cancer-related death worldwide. Given that the standard-of-care for advanced liver cancer is limited, there is an urgent need to develop a novel molecular targeted therapy to improve therapeutic outcomes for HCC. In order to tackle this issue, we conducted functional analysis of the histone lysine-specific demethylase (LSD1) to explore the possibility that this enzyme acts as a therapeutic target in HCC. According to immunohistochemical analysis, 232 of 303 (77%) HCC cases showed positive staining of LSD1 protein, and its expression was correlated with several clinicopathological characteristics, such as female gender, AFP (alpha-fetoprotein) levels, and HCV (hepatitis C virus) infectious. The survival curves for HCC using the Kaplan–Meier method and the log-rank test indicate that positive LSD1 protein expression was significantly associated with decreased rates of overall survival (OS) and disease-free survival (DFS); the multivariate analysis indicates that LSD1 expression was an independent prognostic factor for both OS and DFS in patients with HCC. In addition, knockout of LSD1 using the CRISPR/Cas9 system showed a significantly lower number of colony formation units (CFUs) and growth rate in both SNU-423 and SNU-475 HCC cell lines compared to the corresponding control cells. Moreover, LSD1 knockout decreased cells in S phase of SNU-423 and SNU-475 cells with increased levels of H3K4me1/2 and H3K9me1/2. Finally, we identified the signaling pathways regulated by LSD1 in HCC, including the retinoic acid (RA) pathway. Our findings imply that deregulation of LSD1 can be involved in HCC; further studies may explore the usefulness of LSD1 as a therapeutic target of HCC.

SIRT2: Controversy and multiple roles in disease and physiology

Sirtuin 2 (SIRT2) is an NAD+-dependent deacetylase that was under studied compared to other sirtuin family members. SIRT2 is the only sirtuin protein which is predominantly found in the cytoplasm but is also found in the mitochondria and in the nucleus. Recently, accumulating evidence has uncovered a growing number of substrates and additional detailed functions of SIRT2 in a wide range of biological processes, marking its crucial role. Here, we give a comprehensive profile of the crucial physiological functions of SIRT2 and its role in neurological diseases, cancers, and other diseases. This review summarizes the functions of SIRT2 in the nervous system, mitosis regulation, genome integrity, cell differentiation, cell homeostasis, aging, infection, inflammation, oxidative stress, and autophagy. SIRT2 inhibition rescues neurodegenerative disease symptoms and hence SIRT2 is a potential therapeutic target for neurodegenerative disease. SIRT2 is undoubtedly dysfunctional in cancers and plays a dual-faced role in different types of cancers, and although its mechanism is unresolved, SIRT2 remains a promising therapeutic target for certain cancers. In future, the continued rapid growth in SIRT2 research will help clarify its role in human health and disease, and promote the progress of this target in clinical practice.

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.

Bookmarking by histone methylation ensures chromosomal integrity during mitosis

The cell cycle is an orchestrated process that replicates DNA and transmits genetic information to daughter cells. Cell cycle progression is governed by diverse histone modifications that control gene transcription in a timely fashion. Histone modifications also regulate cell cycle progression by marking specific chromatic regions. While many reviews have covered histone phosphorylation and acetylation as regulators of the cell cycle, little attention has been paid to the roles of histone methylation in the faithful progression of mitosis. Indeed, specific histone methylations occurring before, during, or after mitosis affect kinetochore assembly and chromosome condensation and segregation. In addition to timing, histone methylations specify the chromatin regions such as chromosome arms, pericentromere, and centromere. Therefore, spatiotemporal programming of histone methylations ensures epigenetic inheritance through mitosis. This review mainly discusses histone methylations and their relevance to mitotic progression.

JMJD2A facilitates growth and inhibits apoptosis of cervical cancer cells by downregulating tumor suppressor miR‑491‑5p

Cervical cancer remains the second most common malignancy for women worldwide. Jumonji domain containing 2A (JMJD2A), a member of the JmjC domain-containing family of JMJD2 proteins, is capable of regulating cancer-associated genes, including genes involved in the cell cycle, proliferation, apoptosis, invasion and metastasis. However, its role in human cervical cancer has yet to be elucidated. microRNA (miR)-491-5p, a mature form of miR-491, has been shown to function as a tumor suppressor gene in vitro by inducing apoptosis and inhibiting proliferation and invasion in various types of cancer. However, the underlying mechanism remains to be elucidated. In the present study it was observed that JMJD2A expression was significantly upregulated in human cervical cancer cell lines and cervical epithelial carcinoma tissues. A high JMJD2A level predicted poor overall and disease-free survival rate and may serve as an independent prognostic factor for adverse outcome. JMJD2A increased cervical cancer cell and colony numbers in vitro, increased the tumor weight in a mouse xenograft model, and decreased the apoptotic rate by downregulating the pro-apoptotic proteins Bax, p21 and active caspase-3, and upregulating the anti-apoptotic protein Bcl-2. Transfection experiments indicated that the role of JMJD2A in cervical cancer was mediated, at least in part, by the repression of miR-491-5p. In summary, JMJD2A was identified as an oncogenic protein in human cervical cancer that significantly affected cell and colony numbers, tumor weight and apoptosis via the downregulation of miR-491-5p, which acts as a tumor suppressor in cervical cancer. Therefore, JMJD2A may serve as a prognostic factor and potential target for intervention in cervical cancer.

SOX2 Is a Marker for Stem-like Tumor Cells in Bladder Cancer

It has been reported that functionally distinct cancer stem cells (CSCs) exist in human bladder cancer (BCa). Here, we found that Sox2, a transcription factor that is well characterized as a marker for stem cells, is upregulated in both mouse and human BCa. Sox2 expression is absent in normal urothelial cells, but it begins to be expressed in pre-neoplastic bladder tumors and continues to be expressed in invasive mouse BCa. Using s as a reporter of Sox2 transcriptional expression, we demonstrated that Sox2-expressing cells mark a subpopulation of tumor cells that fuel the growth of established BCa. SOX2-positive cells also expressed other previously reported BCa CSC markers, including Keratin14 (KRT14) and CD44v6. Ablation of Sox2-expressing cells within primary invasive BCa led to enhanced tumor regression, supporting the essential role of SOX2-positive cells in regulating BCa maintenance and progression. Our data show that Sox2 is a marker of bladder CSCs and indicate it as a potential clinical target for BCa therapy.

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Sox2 expression marks bladder cancer stem cells in vivo

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SOX2-positive cells are a subpopulation of KRT14-expressing cancer stem cells

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SOX2-positive cells are a subpopulation of CD44v6-expressing cancer stem cells

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Elimination of Sox2-expressing cells led to reduction of bladder cancer progression

SMYD3-mediated lysine methylation in the PH domain is critical for activation of AKT1

AKT1 is a cytosolic serine/threonine kinase that is overexpressed in various types of cancer and has a central role in human tumorigenesis. Although it is known that AKT1 is post-translationally modified in various ways including phosphorylation and ubiquitination, methylation has not been reported so far. Here we demonstrate that the protein lysine methyltransferase SMYD3 methylates lysine 14 in the PH domain of AKT1 both in vitro and in vivo. Lysine 14-substituted AKT1 shows significantly lower levels of phosphorylation at threonine 308 than wild-type AKT1, and knockdown of SMYD3 as well as treatment with a SMYD3 inhibitor significantly attenuates this phosphorylation in cancer cells. Furthermore, substitution of lysine 14 diminishes the plasma membrane accumulation of AKT1, and cancer cells overexpressing lysine 14-substiuted AKT1 shows lower growth rate than those overexpressing wild-type AKT1. These results imply that SMYD3-mediated methylation of AKT1 at lysine 14 is essential for AKT1 activation and that SMYD3-mediated AKT1 methylation appears to be a good target for development of anti-cancer therapy.

JMJD2A promotes the Warburg effect and nasopharyngeal carcinoma progression by transactivating LDHA expression

BACKGROUND

Jumonji C domain 2A (JMJD2A), as a histone demethylases, plays a vital role in tumorigenesis and progression. But, its functions and underlying mechanisms of JMJD2A in nasopharyngeal carcinoma (NPC) metabolism are remained to be clarified. In this study, we investigated glycolysis regulation by JMJD2A in NPC and the possible mechanism.

METHODS

JMJD2A expression was detected by Western blotting and Reverse transcription quantitative real-time PCR analysis. Then, we knocked down and ectopically expressed JMJD2A to detect changes in glycolytic enzymes. We also evaluated the impacts of JMJD2A-lactate dehydrogenase A (LDHA) signaling on NPC cell proliferation, migration and invasion. ChIP assays were used to test whether JMJD2A bound to the LDHA promoter. Finally, IHC was used to verify JMJD2A and LDHA expression in NPC tissue samples and analyze their correlation between expression and clinical features.

RESULTS

JMJD2A was expressed at high levels in NPC tumor tissues and cell lines. Both JMJD2A and LDHA expression were positively correlated with the tumor stage, metastasis and clinical stage. Additionally, the level of JMJD2A was positively correlated with LDHA expression in NPC patients, and higher JMJD2A and LDHA expression predicted a worse prognosis. JMJD2A alteration did not influence most of glycolytic enzymes expression, with the exception of PFK-L, PGAM-1, LDHB and LDHA, and LDHA exhibited the greatest decrease in expression. JMJD2A silencing decreased LDHA expression and the intracellular ATP level and increased LDH activity, lactate production and glucose utilization, while JMJD2A overexpression produced the opposite results. Furthermore, JMJD2A could combine to LDHA promoter region and regulate LDHA expression at the level of transcription. Activated JMJD2A-LDHA signaling pathway promoted NPC cell proliferation, migration and invasion.

CONCLUSIONS

JMJD2A regulated aerobic glycolysis by regulating LDHA expression. Therefore, the novel JMJD2A-LDHA signaling pathway could contribute to the Warburg effects in NPC progression.

SUV420H1 enhances the phosphorylation and transcription of ERK1 in cancer cells

The oncogenic protein ERK, a member of the extracellular signal-regulated kinase (ERK) cascade, is a well characterized signaling molecule involved in tumorigenesis. The ERK signaling pathway is activated in a large proportion of cancers and plays a critical role in tumor development. Functional regulation by phosphorylation of kinases in the ERK pathway has been extensively studied, however methylation of the ERK protein has not been reported to date. Here, we demonstrated that the protein lysine methyltransferase SUV420H1 tri-methylated ERK1 at lysines 302 and 361, and that substitution of methylation sites diminished phosphorylation levels of ERK1. Concordantly, knockdown of SUV420H1 reduced phosphorylated ERK1 and total ERK1 proteins, and interestingly suppressed ERK1 at the transcriptional level. Our results indicate that overexpression of SUV420H1 may result in activation of the ERK signaling pathway through enhancement of ERK phosphorylation and transcription, thereby providing new insights in the regulation of the ERK cascade in human cancer.

Substituted 2-(2-aminopyrimidin-4-yl)pyridine-4-carboxylates as potent inhibitors of JumonjiC domain-containing histone demethylases

Background: Aberrant expression of iron(II)- and 2-oxoglutarate-dependent JumonjiC histone demethylases has been linked to cancer. Potent demethylase inhibitors are drug candidates and biochemical tools to elucidate the functional impact of demethylase inhibition. Methods & results: Virtual screening identified a novel lead scaffold against JMJD2A with low-micromolar potency in vitro. Analogs were acquired from commercial sources respectively synthesized in feedback with biological testing. Optimized compounds were transformed into cell-permeable prodrugs. A cocrystal x-ray structure revealed the mode of binding of these compounds as competitive to 2-oxoglutarate and confirmed kinetic experiments. Selectivity studies revealed a preference for JMJD2A and JARID1A over JMJD3. Conclusion: Virtual screening and rational structural optimization led to a novel scaffold for highly potent and selective JMJD2A inhibitors.

Downregulation of KDM4A Suppresses the Survival of Glioma Cells by Promoting Autophagy

Glioma is the most common type of primary intracranial tumor and has a poor prognosis. It has been reported that lysine-specific demethylase 4A (KDM4A) can promote tumor progression; however, its role in human glioma remains unclear. Western blot and qRT-PCR analyses showed that KDM4A was highly expressed in U87MG and T98G cells. 48 h after transfection with siKDM4A, the protein level of KDM4A was significantly downregulated. The silenced expression of KDM4A in T98G or U87MG cells inhibited cell viability and invasion, and aggravated cell apoptosis. We found that the siKDM4A led to a significant increase in acidic vesicular organelles (AVOs) and upregulated the expression of autophagy-related proteins, including LC3B-phosphatidylethanolamine conjugate, a cytosolic form of LC3B (LC3B-II/LC3B-I) and Beclin 1 in T98G and U87MG cells. Further studies demonstrated that after pretreatment with 3-MA (3 mmol/L) for 48 h, siKDM4A-transfected cells showed a prominent decrease in LC3B-II/LC3B-I and Beclin 1, accompanied by increased viability and invasion and decreased apoptosis. Our results suggest that the inhibition of KDM4A expression might efficiently suppress glioma cell survival by promoting autophagy, providing a promising agent for treating malignant gliomas.

4-Biphenylalanine- and 3-Phenyltyrosine-Derived Hydroxamic Acids as Inhibitors of the JumonjiC-Domain-Containing Histone Demethylase KDM4A

Overexpression of the histone lysine demethylase KDM4A, which regulates H3K9 and H3K36 methylation states, has been related to the pathology of several human cancers. We found that a previously reported hydroxamate-based histone deacetylase (HDAC) inhibitor (SW55) was also able to weakly inhibit this demethylase with an IC50 value of 25.4 μm. Herein we report the synthesis and biochemical evaluations, with two orthogonal in vitro assays, of a series of derivatives of this lead structure. With extensive chemical modifications on the lead structure, also by exploiting the versatility of the radical arylation with aryldiazonium salts, we were able to increase the potency of the derivatives against KDM4A to the low-micromolar range and, more importantly, to obtain demethylase selectivity with respect to HDACs. Cell-permeable derivatives clearly showed a demethylase-inhibition-dependent antiproliferative effect against HL-60 human promyelocytic leukemia cells.

Direct regulation of E-cadherin by targeted histone methylation of TALE-SET fusion protein in cancer cells

TALE-nuclease chimeras (TALENs) can bind to and cleave specific genomic loci and, are used to engineer gene knockouts and additions. Recently, instead of using the FokI domain, epigenetically active domains, such as TET1 and LSD1, have been combined with TAL effector domains to regulate targeted gene expression via DNA and histone demethylation. However, studies of histone methylation in the TALE system have not been performed. Therefore, in this study, we established a novel targeted regulation system with a TAL effector domain and a histone methylation domain. To construct a TALE-methylation fusion protein, we combined a TAL effector domain containing an E-Box region to act as a Snail binding site and the SET domain of EHMT 2 to allow for histone methylation. The constructed TALE-SET module (TSET) repressed the expression of E-cadherin via by increasing H3K9 dimethylation. Moreover, the cells that overexpressed TSET showed increased cell migration and invasion. This is the first phenotype-based study of targeted histone methylation by the TALE module, and this new system can be applied in new cancer therapies to reduce side effects.

PRMT6 increases cytoplasmic localization of p21CDKN1A in cancer cells through arginine methylation and makes more resistant to cytotoxic agents

p21^CDKN1A is known as a potent inhibitor of cyclin-dependent kinase (CDK), which regulates cell cycle in response to various stimuli, including DNA damage, on the p53-dependent manner. Here we demonstrate that protein arginine methyltransferase 6 (PRMT6) methylates p21 at arginine 156 and promotes phosphorylation of threonine 145 on p21, resulting in the increase of cytoplasmic localization of p21. The cytoplasmic presence of p21 makes cancer cells more resistant to cytotoxic agents. Our results indicate that PRMT6 appears to be one of the key proteins to dysregulate p21 functions in human cancer, and targeting this pathway may be an appropriate strategy for development of anticancer drugs.

Ubiquitination-mediated degradation of cell cycle-related proteins by F-box proteins

F-box proteins, subunits of SKP1-cullin 1-F-box protein (SCF) type of E3 ubiquitin ligase complexes, have been validated to play a crucial role in governing various cellular processes such as cell cycle, cell proliferation, apoptosis, migration, invasion and metastasis. Recently, a wealth of evidence has emerged that F-box proteins is critically involved in tumorigenesis in part through governing the ubiquitination and subsequent degradation of cell cycle proteins, and dysregulation of this process leads to aberrant cell cycle progression and ultimately, tumorigenesis. Therefore, in this review, we describe the critical role of F-box proteins in the timely regulation of cell cycle. Moreover, we discuss how F-box proteins involve in tumorigenesis via targeting cell cycle-related proteins using biochemistry studies, engineered mouse models, and pathological gene alternations. We conclude that inhibitors of F-box proteins could have promising therapeutic potentials in part through controlling of aberrant cell cycle progression for cancer therapies.

Depletion of histone demethylase KDM5B inhibits cell proliferation of hepatocellular carcinoma by regulation of cell cycle checkpoint proteins p15 and p27

Background

KDM5B is a jmjc domain-containing histone demethylase which remove tri-, di-, and monomethyl groups from histone H3 lysine 4 (H3K4). KDM5B has been determined as an oncogene in many malignancies. However, its expression and role in hepatocellular carcinoma (HCC) remain unknown.

Methods

We detected the expression of KDM5B in HCC tissues and cell lines. Cell proliferation was performed to reveal the role of KDM5B depletion on HCC cells both in vivo and in vitro. Flow cytometry was used to analyze the cell cycle and chip analysis was conducted to determine the direct target of KDM5B.

Results

KDM5B is frequently up-regulated in HCC specimens compared with adjacent normal tissues and its expression level was significantly correlated with tumor size, TNM stage, and Edmondson grade. Moreover, Kaplan-Meier survival analysis showed that patients with high levels of KDM5B expression had a relatively poor prognosis. Knockdown of KDM5B notably inhibits HCC cell proliferation both in vivo and in vitro via arresting the cell cycle at G1/S phase partly through up-regulation of p15 and p27. Further molecular mechanism study indicates that silencing of KDM5B promotes p15 and p27 expression by increasing histone H3K4 trimethylation in their promoters.

Conclusions

KDM5B could be a potentially therapeutic target, which provides a rationale for the development of histone demethylase inhibitors as a strategy against HCC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0311-5) contains supplementary material, which is available to authorized users.

The histone demethylase JMJD2A/KDM4A links ribosomal RNA transcription to nutrients and growth factors availability

The interplay between methylation and demethylation of histone lysine residues is an essential component of gene expression regulation and there is considerable interest in elucidating the roles of proteins involved. Here we report that histone demethylase KDM4A/JMJD2A, which is involved in the regulation of cell proliferation and is overexpressed in some cancers, interacts with RNA Polymerase I, associates with active ribosomal RNA genes and is required for serum-induced activation of rDNA transcription. We propose that KDM4A controls the initial stages of transition from 'poised', non-transcribed rDNA chromatin into its active form. We show that PI3K, a major signalling transducer central for cell proliferation and survival, controls cellular localization of KDM4A and consequently its association with ribosomal DNA through the SGK1 downstream kinase. We propose that the interplay between PI3K/SGK1 signalling cascade and KDM4A constitutes a mechanism by which cells adapt ribosome biogenesis level to the availability of growth factors and nutrients.

IOX1, a JMJD2A inhibitor, suppresses the proliferation and migration of vascular smooth muscle cells induced by angiotensin II by regulating the expression of cell cycle-related proteins

The epigenetic modification of vascular smooth muscle cell (VSMC) phenotypic switching, proliferation, migration, apoptosis and extracellular matrix synthesis is known to occur in atherosclerosis. The aim of the present study was to investigate the effects of IOX1, a Jumonji domain-containing 2A (JMJD2A) inhibitor, on regulation of the cell cycle in angiotensin II (Ang II)-stimulated VSMCs and to elucidate the possible mechanisms involved. The proliferation and migration of the Ang II-stimulated VSMCs in the presence or absence of IOX1 were evaluated in vitro. Flow cytometric analysis was used to determine the effects of IOX1 on cell cycle progression. RT-qPCR and western blot analysis were carried out to measure the expression levels of cell cycle-related genes. The trimethylation of histone H3 lysine 9 (H3K9me3) at the promoters of these genes was detected by chromatin immunoprecipitation (ChIP) assay. We confirmed that the JMJD2A levels were increased, whereas the H3K9me3 levels were decreased in the Ang II-stimulated VSMCs. The inhibition of JMJD2A by IOX1 suppressed the Ang II-induced cell proliferation, migration and cell cycle progression by inhibiting cyclin D1 expression and increasing p21 expression. The underlying mechanisms were related to the restoration of the H3K9me3 levels at the promoters of these genes. In conclusion, the findings of our study indicate that IOX1 exerts its anti-proliferative and anti-migratory effects by regulating the expression of the cell cycle-related proteins, cyclin D1 and p21.

Jumonji domain containing 2A predicts prognosis and regulates cell growth in lung cancer depending on miR-150

Lung cancer has become the most common cancer worldwide, of which non-small cell lung cancer (NSCLC) accounts for over 80%. Previous studies have shown that the Jumonji domain containing 2A (JMJD2A) was aberrantly expressed in various tumors and involved in the regulation of tumor progression, but the role of JMJD2A on the tumorigenesis in NSCLC and the underlying mechanisms are still unclear. In the present study, we first identified the expression of JMJD2A in NSCLC tissues and cell lines through quantitative RT-PCR (qRT-PCR) and western blotting. Next, the effects of JMJD2A on the progression of NSCLC were analyzed. MTT assay was performed to measure the cell numbers and fluorescence-activated cell sorting (FACS) was adopted to evaluate cell apoptosis. Finally, the relationship between JMJD2A and miR-150 involved in NSCLC was studied. Our results suggested that JMJD2A was significantly overexpressed in NSCLC samples and cell lines. Kaplan-Meier analysis showed that high level of JMJD2A predicted a poor prognosis. Knockdown of JMJD2A inhibited tumor growth and promoted cell apoptosis in NSCLC cells. Additionally, miR-150 was upregulated in NSCLC tissues and positively related with JMJD2A expression. Significant downregulation of miR-150 was observed with JMJD2A knockdown. Furthermore, JMJD2A knockdown inhibited NSCLC cell proliferation while the silencing of miR-150 attenuated the inhibition effect on cell proliferation, suggesting that the effect of JMJD2A on NSCLC cell growth was dependent on miR-150. Thus, our findings identified that JMJD2A played an oncogenic role in NSCLC via regulating miR-150. JMJD2A could possibly serve as a prognostic factor and potential target for NSCLC therapy.

Late Cornified Envelope Group I, a novel target of p53, regulates PRMT5 activity

p53 is one of the most important tumor suppressor genes involved in human carcinogenesis. Although downstream targets of p53 and their biologic functions in cancer cells have been extensively investigated, it is still far from the full understanding. Here, we demonstrate that Late Cornified Envelope Group I (LCE1) genes, which are located in the LCE gene clusters encoding multiple well-conserved stratum-corneum proteins, are novel downstream targets of p53. Exogenous p53 overexpression using an adenoviral vector system significantly enhanced the expression of LCE1 cluster genes. We also observed induction of LCE1 expressions by DNA damage, which was caused by treatment with adriamycin or UV irradiation in a wild-type p53-dependent manner. Concordantly, the induction of LCE1 by DNA damage was significantly attenuated by the knockdown of p53. Among predicted p53-binding sites within the LCE1 gene cluster, we confirmed one site to be a p53-enhancer sequence by reporter assays. Furthermore, we identified LCE1 to interact with protein arginine methyltransferase 5 (PRMT5). Knockdown of LCE1 by specific small interfering RNAs significantly increased the symmetric dimethylation of histone H3 arginine 8, a substrate of PRMT5, and overexpression of LCE1F remarkably decreased its methylation level. Our data suggest that LCE1 is a novel p53 downstream target that can be directly transactivated by p53 and is likely to have tumor suppressor functions through modulation of the PRMT5 activity.

Critical roles of non-histone protein lysine methylation in human tumorigenesis

Several protein lysine methyltransferases and demethylases have been identified to have critical roles in histone modification. A large body of evidence has indicated that their dysregulation is involved in the development and progression of various diseases, including cancer, and these enzymes are now considered to be potential therapeutic targets. Although most studies have focused on histone methylation, many reports have revealed that these enzymes also regulate the methylation dynamics of non-histone proteins such as p53, RB1 and STAT3 (signal transducer and activator of transcription 3), which have important roles in human tumorigenesis. In this Review, we summarize the molecular functions of protein lysine methylation and its involvement in human cancer, with a particular focus on lysine methylation of non-histone proteins.

A coding single-nucleotide polymorphism in lysine demethylase KDM4A associates with increased sensitivity to mTOR inhibitors

SNPs occur within chromatin-modulating factors; however, little is known about how these variants within the coding sequence affect cancer progression or treatment. Therefore, there is a need to establish their biochemical and/or molecular contribution, their use in subclassifying patients, and their impact on therapeutic response. In this report, we demonstrate that coding SNP-A482 within the lysine tridemethylase gene KDM4A/JMJD2A has different allelic frequencies across ethnic populations, associates with differential outcome in patients with non-small cell lung cancer (NSCLC), and promotes KDM4A protein turnover. Using an unbiased drug screen against 87 preclinical and clinical compounds, we demonstrate that homozygous SNP-A482 cells have increased mTOR inhibitor sensitivity. mTOR inhibitors significantly reduce SNP-A482 protein levels, which parallels the increased drug sensitivity observed with KDM4A depletion. Our data emphasize the importance of using variant status as candidate biomarkers and highlight the importance of studying SNPs in chromatin modifiers to achieve better targeted therapy.

SIGNIFICANCE

This report documents the first coding SNP within a lysine demethylase that associates with worse outcome in patients with NSCLC. We demonstrate that this coding SNP alters the protein turnover and associates with increased mTOR inhibitor sensitivity, which identifies a candidate biomarker for mTOR inhibitor therapy and a therapeutic target for combination therapy.

Critical role of lysine 134 methylation on histone H2AX for γ-H2AX production and DNA repair

The presence of phosphorylated histone H2AX (γ-H2AX) is associated with the local activation of DNA-damage repair pathways. Although γ-H2AX deregulation in cancer has previously been reported, the molecular mechanism involved and its relationship with other histone modifications remain largely unknown. Here we find that the histone methyltransferase SUV39H2 methylates histone H2AX on lysine 134. When H2AX was mutated to abolish K134 methylation, the level of γ-H2AX became significantly reduced. We also found lower γ-H2AX activity following the introduction of double-strand breaks in Suv39h2 knockout cells or on SUV39H2 knockdown. Tissue microarray analyses of clinical lung and bladder tissues also revealed a positive correlation between H2AX K134 methylation and γ-H2AX levels. Furthermore, introduction of K134-substituted histone H2AX enhanced radio- and chemosensitivity of cancer cells. Overall, our results suggest that H2AX methylation plays a role in the regulation of γ-H2AX abundance in cancer.

γ-H2AX The Ser139 phosphorylated form of H2AX, γ-H2AX, is generated in response to DNA double-strand breaks and is involved in the repair process. Here, Sone et al. show that H2AX K134 methylation by SUV39H2 is crucial for the production of γ-H2AX, and that loss of methylation correlates with radio- and chemosensitivity.

The role of the histone demethylase KDM4A in cancer

Histone posttranslational modifications are important components of epigenetic regulation. One extensively studied modification is the methylation of lysine residues. These modifications were thought to be irreversible. However, several proteins with histone lysine demethylase functions have been discovered and characterized. Among these proteins, KDM4A is the first histone lysine demethylase shown to demethylate trimethylated residues. This enzyme plays an important role in gene expression, cellular differentiation, and animal development. Recently, it has also been shown to be involved in cancer. In this review, we focus on describing the structure, mechanisms, and function of KDM4A. We primarily discuss the role of KDM4A in cancer development and the importance of KDM4A as a potential therapeutic target.

Epigenetic pathway targets for the treatment of disease: accelerating progress in the development of pharmacological tools: IUPHAR Review 11

The properties of a cell are determined both genetically by the DNA sequence of its genes and epigenetically through processes that regulate the pattern, timing and magnitude of expression of its genes. While the genetic basis of disease has been a topic of intense study for decades, recent years have seen a dramatic increase in the understanding of epigenetic regulatory mechanisms and a growing appreciation that epigenetic misregulation makes a significant contribution to human disease. Several large protein families have been identified that act in different ways to control the expression of genes through epigenetic mechanisms. Many of these protein families are finally proving tractable for the development of small molecules that modulate their function and represent new target classes for drug discovery. Here, we provide an overview of some of the key epigenetic regulatory proteins and discuss progress towards the development of pharmacological tools for use in research and therapy.

Restoration of desmosomal junction protein expression and inhibition of H3K9-specific histone demethylase activity by cytostatic proline-rich polypeptide-1 leads to suppression of tumorigenic potential in human chondrosarcoma cells

Disruption of cell-cell junctions and the concomitant loss of polarity, downregulation of tumor-suppressive adherens junctions and desmosomes represent hallmark phenotypes for several different cancer cells. Moreover, a variety of evidence supports the argument that these two common phenotypes of cancer cells directly contribute to tumorigenesis. In this study, we aimed to determine the status of intercellular junction proteins expression in JJ012 human malignant chondrosarcoma cells and investigate the effect of the antitumorigenic cytokine, proline-rich polypeptide-1 (PRP-1) on their expression. The cell junction pathway array data indicated downregulation of desmosomal proteins, such as desmoglein (1,428-fold), desmoplakin (620-fold) and plakoglobin (442-fold). The tight junction proteins claudin 11 and E-cadherin were also downregulated (399- and 52-fold, respectively). Among the upregulated proteins were the characteristic for tumors gap junction β-5 protein (connexin 31.1) and the pro-inflammatory pathway protein intercellular adhesion molecule (upregulated 129- and 43-fold, respectively). We demonstrated that PRP-1 restored the expression of the abovementioned downregulated in chondrosarcoma desmosomal proteins. PRP-1 inhibited H3K9-specific histone demethylase activity in chondrosarcoma cells in a dose-dependent manner (0.5 µg/ml PRP, 63%; 1 µg/ml PRP, 74%; and 10 µg/ml PRP, 91% inhibition). Members of the H3K9 family were shown to transcriptionally repress tumor suppressor genes and contribute to cancer progression. Our experimental data indicated that PRP-1 restores tumor suppressor desmosomal protein expression in JJ012 human chondrosarcoma cells and inhibits H3K9 demethylase activity, contributing to the suppression of tumorigenic potential in chondrosarcoma cells.

WHSC1 promotes oncogenesis through regulation of NIMA-related kinase-7 in squamous cell carcinoma of the head and neck

Squamous cell carcinoma of the head and neck (SCCHN) is a relatively common malignancy with suboptimal long-term prognosis, thus new treatment strategies are urgently needed. Over the last decade, histone methyltransferases (HMT) have been recognized as promising targets for cancer therapy, but their mechanism of action in most solid tumors, including SCCHN, remains to be elucidated. This study investigated the role of Wolf-Hirschhorn syndrome candidate 1 (WHSC1), an NSD family HMT, in SCCHN. Immunohistochemical analysis of locoregionally advanced SCCHN, dysplastic, and normal epithelial tissue specimens revealed that WHSC1 expression and dimethylation of histone H3 lysine 36 (H3K36me2) were significantly higher in SCCHN tissues than in normal epithelium. Both WHSC1 expression and H3K36me2 levels were significantly correlated with histologic grade. WHSC1 knockdown in multiple SCCHN cell lines resulted in significant growth suppression, induction of apoptosis, and delay of the cell-cycle progression. Immunoblot and immunocytochemical analyses in SCCHN cells demonstrated that WHSC1 induced H3K36me2 and H3K36me3. Microarray expression profile analysis revealed NIMA-related kinase-7 (NEK7) to be a downstream target gene of WHSC1, and chromatin immunoprecipitation (ChIP) assays showed that NEK7 was directly regulated by WHSC1 through H3K36me2. Furthermore, similar to WHSC1, NEK7 knockdown significantly reduced cell-cycle progression, indicating that NEK7 is a key player in the molecular pathway regulated by WHSC1.

IMPLICATIONS

WHSC1 possesses oncogenic functions in SCCHN and represents a potential molecular target for the treatment of SCCHN.

The oncogenic polycomb histone methyltransferase EZH2 methylates lysine 120 on histone H2B and competes ubiquitination

The histone methyltransferase enhancer of zeste 2 (EZH2) is known to be a polycomb protein homologous to Drosophila enhancer of zeste and catalyzes the addition of methyl groups to histone H3 at lysine 27 (H3K27). We previously reported that EZH2 was overexpressed in various types of cancer and plays a crucial role in the cell cycle regulation of cancer cells. In the present study, we demonstrated that EZH2 has the function to monomethylate lysine 120 on histone H2B (H2BK120). EZH2-dependent H2BK120 methylation in cancer cells was confirmed with an H2BK120 methylation-specific antibody. Overexpression of EZH2 significantly attenuated the ubiquitination of H2BK120, a key posttranslational modification of histones for transcriptional regulation. Concordantly, knockdown of EZH2 increased the ubiquitination level of H2BK120, suggesting that the methylation of H2BK120 by EZH2 may competitively inhibit the ubiquitination of H2BK120. Subsequent chromatin immunoprecipitation-Seq and microarray analyses identified downstream candidate genes regulated by EZH2 through the methylation of H2BK120. This is the first report to describe a novel substrate of EZH2, H2BK120, unveiling a new aspect of EZH2 functions in human carcinogenesis.

siRNA delivery to the lung: what's new?

RNA interference (RNAi) has been thought of as the general answer to many unmet medical needs. After the first success stories, it soon became obvious that short interfering RNA (siRNA) is not suitable for systemic administration due to its poor pharmacokinetics. Therefore local administration routes have been adopted for more successful in vivo RNAi. This paper reviews nucleic acid modifications, nanocarrier chemistry, animal models used in successful pulmonary siRNA delivery, as well as clinical translation approaches. We summarize what has been published recently and conclude with the potential problems that may still hamper the efficient clinical application of RNAi in the lung.