Jmjd2c histone demethylase enhances the expression of Mdm2 oncogene

KDM4 Demethylases: Structure, Function, and Inhibitors

KDM4 histone demethylases mainly catalyze the removal of methyl marks from H3K9 and H3K36 to epigenetically regulate chromatin structure and gene expression. KDM4 expression is strictly regulated to ensure proper function in a myriad of biological processes, including transcription, cellular proliferation and differentiation, DNA damage repair, immune response, and stem cell self-renewal. Aberrant expression of KDM4 demethylase has been documented in many types of blood and solid tumors, and thus, KDM4s represent promising therapeutic targets. In this chapter, we summarize the current knowledge of the structures and regulatory mechanisms of KDM4 proteins and our understanding of their alterations in human pathological processes with a focus on development and cancer. We also review the reported KDM4 inhibitors and discuss their potential as therapeutic agents.

MALAT1 in colorectal cancer: Its implication as a diagnostic, prognostic, and predictive biomarker

Metastasis Associated Lung Adenocarcinoma Transcript 1 (MALAT1), originally described as a prognostic biomarker remarkably linked with metastasis potential in lung cancer, has been identified as contributing to many diseases, including colorectal cancer (CRC). This long non-coding RNA (lncRNA) has come to the forefront of lncRNA research for its implications in cancer-related processes, such as cell proliferation and migration. In general, lncRNAs are recognized as enhancers, scaffolds, or decoys for a variety of oncogenes and tumor suppressors, although our understanding of lncRNA functions and mechanisms of action is still limited. Nowadays, cancer research is attracted to lncRNAs' ability to improve the early diagnosis of cancer, determine patients' prognosis, or predict therapy outcomes. In this review, we aimed to evaluate recent publications trying to uncover the cellular mechanisms of MALAT1-mediated regulation, and its potential exploitation in the management of CRC. The conclusions of this review provide robust support for the essential role of MALAT1 in CRC development and future personalized therapy.

The JMJD Family Histone Demethylases in Crosstalk Between Inflammation and Cancer

Inflammation has emerged as a key player in regulating cancer initiation, progression, and therapeutics, acting as a double edged sword either facilitating cancer progression and therapeutic resistance or inducing anti-tumor immune responses. Accumulating evidence has linked the epigenetic modifications of histones to inflammation and cancer, and histone modifications-based strategies have shown promising therapeutic potentials against cancer. The jumonji C domain-containing (JMJD) family histone demethylases have exhibited multiple regulator functions in inflammatory processes and cancer development, and a number of therapeutic strategies targeting JMJD histone demethylases to modulate inflammatory cells and their products have been successfully evaluated in clinical or preclinical tumor models. This review summarizes current understanding of the functional roles and mechanisms of JMJD histone demethylases in crosstalk between inflammation and cancer, and highlights recent clinical and preclinical progress on harnessing the JMJD histone demethylases to regulate cancer-related inflammation for future cancer therapeutics.

JMJD2C mediates the MDM2/p53/IL5RA axis to promote CDDP resistance in uveal melanoma

Chemotherapy resistance poses an obstacle for effective treatment of uveal melanoma. In this study, we aim to investigate the effects of jumonji domain containing 2C (JMJD2C)-mediated mouse double minute-2 homolog (MDM2)/p53/interleukin 5 receptor subunit alpha (IL5RA) axis on cisplatin (CDDP) resistance in uveal melanoma. RT-qPCR and Western blot assay were performed to determine their expression patterns in uveal melanoma cell line (MUM-2B) and CDDP-resistant cell line (MUM-2B/CDDP). The enrichment of H3K9me3 in MDM2 promoter region was examined by ChIP, and the binding between p53 and ubiquitin in MUM-2B cells testified by co-IP assay. Following overexpression or silencing of JMJD2C/MDM2/p53/IL5RA, the 50% concentration of inhibition (IC50) and the biological characteristics of MUM-2B and MUM-2B/CDDP cells were examined using CCK-8 assay, SA-β-gal staining, fluorescence-activated cell sorting analysis, and Transwell assay. Finally, the tumorigenicity of transplanted MUM-2B and MUM-2B/CDDP cells in nude mice was assessed. JMJD2C was documented to be highly expressed in uveal melanoma cells, promoting the CDDP resistance. Histone demethylase JMJD2C removed the H3K9me3 modification of MDM2 promoter, which promoted the expression of MDM2. MDM2 enhanced the IL5RA expression through stimulating the ubiquitination and degradation of p53, thus inducing CDDP resistance of uveal melanoma cells. Furthermore, the results of in vivo experiments revealed that JMJD2C mediated the MDM2/p53/IL5RA axis to expedite the growth of uveal melanoma and augment the CDDP resistance. Taken together, JMJD2C can induce histone demethylation to upregulate MDM2, thereby ubiquitinating p53 and upregulating IL5RA. As a consequence, CDDP resistance in uveal melanoma is ultimately accelerated.

Histone demethylase KDM4C controls tumorigenesis of glioblastoma by epigenetically regulating p53 and c-Myc

Glioblastoma is the most lethal brain tumor and its pathogenesis remains incompletely understood. KDM4C is a histone H3K9 demethylase that contributes to epigenetic regulation of both oncogene and tumor suppressor genes and is often overexpressed in human tumors, including glioblastoma. However, KDM4C’s roles in glioblastoma and the underlying molecular mechanisms remain unclear. Here, we show that KDM4C knockdown significantly represses proliferation and tumorigenesis of glioblastoma cells in vitro and in vivo that are rescued by overexpressing wild-type KDM4C but not a catalytic dead mutant. KDM4C protein expression is upregulated in glioblastoma, and its expression correlates with c-Myc expression. KDM4C also binds to the c-Myc promoter and induces c-Myc expression. Importantly, KDM4C suppresses the pro-apoptotic functions of p53 by demethylating p53K372me1, which is pivotal for the stability of chromatin-bound p53. Conversely, depletion or inhibition of KDM4C promotes p53 target gene expression and induces apoptosis in glioblastoma. KDM4C may serve as an oncogene through the dual functions of inactivation of p53 and activation of c-Myc in glioblastoma. Our study demonstrates KDM4C inhibition as a promising therapeutic strategy for targeting glioblastoma.

The pivotal role of MicroRNAs in glucose metabolism in cancer

Cancer cells are able to undergo aerobic glycolysis and metabolize glucose to lactate instead of oxidative phosphorylation, which is known as Warburg effect. Accumulating evidence has revealed that microRNAs regulate cancer cell metabolism, which manifest a higher rate of glucose metabolism. Various signaling pathways along with glycolytic enzymes are responsible for the emergence of glycolytic dependence. MicroRNAs are a class of non-coding RNAs that are not translated into proteins but regulate target gene expression or in other words function pre-translationally and post-transcriptionally. MicroRNAs have been shown to be involved in various biological processes, including glucose metabolism via targeting major transcription factors, enzymes, oncogenes or tumor suppressors alongside the oncogenic signaling pathways. In this review, we describe the regulatory role of microRNAs of cancer cell glucose metabolism, including in the glucose uptake, glycolysis, tricarboxylic acid cycle and several signaling pathways and further suggest that microRNA-based therapeutics can be used to inhibit the process of glucose metabolism reprogramming in cancer cells and thus suppressing cancer progression.

Benzo[b]tellurophenes as a Potential Histone H3 Lysine 9 Demethylase (KDM4) Inhibitor

Gene expression and tumor growth can be regulated by methylation levels of lysine residues on histones, which are controlled by histone lysine demethylases (KDMs). Series of benzo[b]tellurophene and benzo[b]selenophene compounds were designed and synthesized and they were evaluated for histone H3 lysine 9 demethylase (KDM4) inhibitory activity. Among the carbamates, alcohol and aromatic derivatives, tert-butyl benzo[b]tellurophen-2-ylmethylcarbamate (compound 1c) revealed KDM4 specific inhibitory activity in cervical cancer HeLa cells, whereas the corresponding selenium or oxygen substitute compounds did not display any inhibitory activity toward KDM4. Compound 1c also induced cell death in cervical and colon cancer but not in normal cells. Thus, compound 1c, a novel inhibitor of KDM4, constitutes a potential therapeutic and research tool against cancer.

JMJD2C promotes colorectal cancer metastasis via regulating histone methylation of MALAT1 promoter and enhancing β-catenin signaling pathway

Background

Our previous work demonstrated that lncRNA-MALAT1 was overexpressed in recurrent colorectal cancer (CRC) and metastatic sites in post-surgical patients. However, the upstream regulatory mechanism of MALAT1 is not well-defined. Histone demethylase JMJD2C holds great potential of epigenetic regulating mechanism in tumor diseases, especially the moderating effect on the promoter activity of targeted genes associated closely with tumor development. Therefore, we herein investigated whether JMJD2C could epigeneticly regulate the promoter activity of MALAT1 and the downstream β-catenin signaling pathway, thereby affecting the metastatic abilities of CRC cells.

Methods

JMJD2C expressions in human CRC samples were detected by real-time PCR and immunohistochemistry staining. Gene silencing and overexpressing efficiencies of JMJD2C were confirmed by real-time PCR and western blot. The migration of CRC cells in vitro were tested by transwell and wound healing assays. The protein expression and cellular localization of JMJD2C and β-catenin were characterized by immunofluorescence staining and western blot. The histone methylation level of MALAT1 promoter region (H3K9me3 and H3K36me3) was tested by ChIP-PCR assays. The promoter activity of MALAT1 was detected by luciferase reporter assay. The expressions of MALAT1 and the downstream β-catenin signaling pathway related genes in CRC cells were detected by real-time PCR and western blot, respectively. The nude mice tail vein metastasis model was established to observe the effect of JMJD2C on the lung metastasis of CRC cells in vivo.

Results

Our present results indicated that histone demethylase JMJD2C was overexpressed in matched CRC tumor tissues of primary and metastatic foci, and CRC patients with lower JMJD2C expression in primary tumors had better prognosis with longer OS (Overall Survival). The following biological function observation suggested that JMJD2C promoted CRC metastasis in vitro and in vivo. Further molecular mechanism investigation demonstrated that JMJD2C protein translocated into the nuclear, lowered the histone methylation level of MALAT1 promoter in the sites of H3K9me3 and H3K36me3, up-regulated the expression of MALAT1, and enhanced the β-catenin signaling pathway in CRC cells.

Conclusion

Our data demonstrated that JMJD2C could enhance the metastatic abilities of CRC cells in vitro and in vivo by regulating the histone methylation level of MALAT1 promoter, thereby up-regulating the expression of MALAT1 and enhancing the activity of β-catenin signaling pathway, providing that JMJD2C might be a novel therapeutic target for CRC metastasis.

Glioblastoma initiating cells are sensitive to histone demethylase inhibition due to epigenetic deregulation

Tumor-initiating cells are a subpopulation of cells that have self-renewal capacity to regenerate a tumor. Here, we identify stem cell-like chromatin features in human glioblastoma initiating cells (GICs) and link them to a loss of the repressive histone H3 lysine 9 trimethylation (H3K9me3) mark. Increasing H3K9me3 levels by histone demethylase inhibition led to cell death in GICs but not in their differentiated counterparts. The induction of apoptosis was accompanied by a loss of the activating H3 lysine 9 acetylation (H3K9ac) modification and accumulation of DNA damage and downregulation of DNA damage response genes. Upon knockdown of histone demethylases, KDM4C and KDM7A both differentiation and DNA damage were induced. Thus, the H3K9me3-H3K9ac equilibrium is crucial for GIC viability and represents a chromatin feature that can be exploited to specifically target this tumor subpopulation.

Micromanaging aerobic respiration and glycolysis in cancer cells

BACKGROUND

Cancer cells possess a common metabolic phenotype, rewiring their metabolic pathways from mitochondrial oxidative phosphorylation to aerobic glycolysis and anabolic circuits, to support the energetic and biosynthetic requirements of continuous proliferation and migration. While, over the past decade, molecular and cellular studies have clearly highlighted the association of oncogenes and tumor suppressors with cancer-associated glycolysis, more recent attention has focused on the role of microRNAs (miRNAs) in mediating this metabolic shift. Accumulating studies have connected aberrant expression of miRNAs with direct and indirect regulation of aerobic glycolysis and associated pathways.

SCOPE OF REVIEW

This review discusses the underlying mechanisms of metabolic reprogramming in cancer cells and provides arguments that the earlier paradigm of cancer glycolysis needs to be updated to a broader concept, which involves interconnecting biological pathways that include miRNA-mediated regulation of metabolism. For these reasons and in light of recent knowledge, we illustrate the relationships between metabolic pathways in cancer cells. We further summarize our current understanding of the interplay between miRNAs and these metabolic pathways. This review aims to highlight important metabolism-associated molecular components in the hunt for selective preventive and therapeutic treatments.

MAJOR CONCLUSIONS

Metabolism in cancer cells is influenced by driver mutations but is also regulated by posttranscriptional gene silencing. Understanding the nuanced regulation of gene expression in these cells and distinguishing rapid cellular responses from chronic adaptive mechanisms provides a basis for rational drug design and novel therapeutic strategies.

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.

ERMP1, a novel potential oncogene involved in UPR and oxidative stress defense, is highly expressed in human cancer

Endoplasmic reticulum (ER) stress and unfolded protein response (UPR) are highly activated in cancer and involved in tumorigenesis and resistance to anti-cancer therapy. UPR is becoming a promising target of anti-cancer therapies. Thus, the identification of UPR components that are highly expressed in cancer could offer new therapeutic opportunity.

In this study, we demonstrate that Endoplasmic Reticulum Metallo Protease 1 (ERMP1) is broadly expressed in a high percentage of breast, colo-rectal, lung, and ovary cancers, regardless of their stage and grade. Moreover, we show that loss of ERMP1 expression significantly hampers proliferation, migration and invasiveness of cancer cells. Furthermore, we show that this protein is an important player in the UPR and defense against oxidative stress. ERMP1 expression is strongly affected by reticular stress induced by thapsigargin and other oxidative stresses. ERMP1 silencing during reticular stress impairs the activation of PERK, a key sensor of the UPR activation. Loss of ERMP1 also prevents the expression of GRP78/BiP, a UPR stress marker involved in the activation of the survival pathway. Finally, ERMP1 silencing in cells exposed to hypoxia leads to inhibition of the Nrf2-mediated anti-oxidant response and to reduction of accumulation of HIF-1, the master transcription factor instructing cells to respond to hypoxic stress. Our results suggest that ERMP1 could act as a molecular starter to the survival response induced by extracellular stresses. Moreover, they provide the rationale for the design of ERMP1-targeting drugs that could act by inhibiting the UPR initial adaptive response of cancer cells and impair cell survival.

Targeting the Senescence-Overriding Cooperative Activity of Structurally Unrelated H3K9 Demethylases in Melanoma

Oncogene-induced senescence, e.g., in melanocytic nevi, terminates the expansion of pre-malignant cells via transcriptional silencing of proliferation-related genes due to decoration of their promoters with repressive trimethylated histone H3 lysine 9 (H3K9) marks. We show here that structurally distinct H3K9-active demethylases-the lysine-specific demethylase-1 (LSD1) and several Jumonji C domain-containing moieties (such as JMJD2C)-disable senescence and permit Ras/Braf-evoked transformation. In mouse and zebrafish models, enforced LSD1 or JMJD2C expression promoted Braf-V600E-driven melanomagenesis. A large subset of established melanoma cell lines and primary human melanoma samples presented with a collective upregulation of related and unrelated H3K9 demethylase activities, whose targeted inhibition restored senescence, even in Braf inhibitor-resistant melanomas, evoked secondary immune effects and controlled tumor growth in vivo.

Histone demethylase JMJD2C: epigenetic regulators in tumors

Histone methylation is one of the major epigenetic modifications, and various histone methylases and demethylases participate in the epigenetic regulating. JMJD2C has been recently identified as one of the histone lysine demethylases. As one member of the Jumonji-C histone demethylase family, JMJD2C has the ability to demethylate tri- or di-methylated histone 3 and 2 in either K9 (lysine residue 9) or K36 (lysine residue 36) sites by an oxidative reaction, thereby affecting heterochromatin formation, genomic imprinting, X-chromosome inactivation, and transcriptional regulation of genes. JMJD2C was firstly found to involve in embryonic development and stem cell regulation. Afterwards, aberrant status of JMJD2C histone methylation was observed during the formation and development of various tumors, and it has been reported to play crucial roles in the progression of breast cancer, prostate carcinomas, osteosarcoma, blood neoplasms and so on, indicating that JMJD2C represents a promising anti-cancer target. In this review, we will focus on the research progress and prospect of JMJD2C in tumors, and provide abundant evidence for the functional application and therapeutic potential of targeting JMJD2C in tumors.

microRNA-1827 represses MDM2 to positively regulate tumor suppressor p53 and suppress tumorigenesis

The tumor suppressor p53 plays a central role in tumor prevention. The E3 ubiquitin ligase MDM2 is the most critical negative regulator of p53, which binds to p53 and degrades p53 through ubiquitation. MDM2 itself is a transcriptional target of p53, and therefore, MDM2 forms a negative feedback loop with p53 to tightly regulate p53 levels and function. microRNAs (miRNAs) play a key role in regulation of gene expression. miRNA dysregulation plays an important role in tumorigenesis. In this study, we found that miRNA miR-1827 is a novel miRNA that targets MDM2 through binding to the 3′-UTR of MDM2 mRNA. miR-1827 negatively regulates MDM2, which in turn increases p53 protein levels to increase transcriptional activity of p53 and enhance p53-mediated stress responses, including apoptosis and senescence. Overexpression of miR-1827 suppresses the growth of xenograft colorectal tumors, whereas the miR-1827 inhibitor promotes tumor growth in mice in a largely p53-dependent manner. miR-1827 is frequently down-regulated in human colorectal cancer. Decreased miR-1827 expression is associated with high MDM2 expression and poor prognosis in colorectal cancer. In summary, our results reveal that miR-1827 is a novel miRNA that regulates p53 through targeting MDM2, and highlight an important role and the underlying mechanism of miR-1827 in tumor suppression.

Jmjd2C increases MyoD transcriptional activity through inhibiting G9a-dependent MyoD degradation

Skeletal muscle cell differentiation requires a family of proteins called myogenic regulatory factors (MRFs) to which MyoD belongs. The activity of MyoD is under epigenetic regulation, however, the molecular mechanism by which histone KMTs and KDMs regulate MyoD transcriptional activity through methylation remains to be determined. Here we provide evidence for a unique regulatory mechanism of MyoD transcriptional activity through demethylation by Jmjd2C demethylase whose level increases during muscle differentiation. G9a decreases MyoD stability via methylation-dependent MyoD ubiquitination. Jmjd2C directly associates with MyoD in vitro and in vivo to demethylate and stabilize MyoD. The hypo-methylated MyoD due to Jmjd2C is significantly more stable than hyper-methylated MyoD by G9a. Cul4/Ddb1/Dcaf1 pathway is essential for the G9a-mediated MyoD degradation in myoblasts. By the stabilization of MyoD, Jmjd2C increases myogenic conversion of mouse embryonic fibroblasts and MyoD transcriptional activity with erasing repressive H3K9me3 level at the promoter of MyoD target genes. Collectively, Jmjd2C increases MyoD transcriptional activity to facilitate skeletal muscle differentiation by increasing MyoD stability through inhibiting G9a-dependent MyoD degradation.

A three-gene signature and clinical outcome in esophageal squamous cell carcinoma

It is increasingly apparent that cancer development depends not only on genetic alterations, but also on epigenetic changes involving histone modifications. GASC1, member of the histone demethylases affecting heterochromatin formation and transcriptional repression, has been found to be dysregulation in many types of cancers including breast cancer, prostate cancer, metastatic lung sarcomatoid carcinoma, and leukemia. In this study, we examined the expression of GASC1 and certain GASC1-targeted genes (KLF4, MYC, SOX2, PPARG, MDM2, and NANOG) and identified a three-gene prognostic signature (PPARG, MDM2, and NANOG), using risk scores based on immunohistochemical analyses of 149 tumor specimens from patients with esophageal squamous cell carcinoma (ESCC). The presence of a high-risk three-gene signature in the ESCC tumors was significantly associated with decreased overall survival (OS) of the patients. We validated the predictive value of the three-gene signature in a second independent cohort of 101 patients with ESCC in order to determine whether it had predictive value. The results were similar to those in 149 patients. According to multivariate Cox proportional hazards analyses, the predictive model of a three-gene signature was an independent predictor for OS (p = 0.005 in cohort 1, p = 0.025 in cohort 2). In addition, ROC analysis indicated that the predictive ability of the three-gene model was more robust than that of a single biomarker. Therefore, our three-gene signature is closely associated with OS among patients with ESCC and may serve as a predictor for the poor prognosis of ESCC patients.

Molecular basis for substrate recognition by lysine methyltransferases and demethylases

Lysine methylation has emerged as a prominent covalent modification in histones and non-histone proteins. This modification has been implicated in numerous genomic processes, including heterochromatinization, cell cycle progression, DNA damage response, DNA replication, genome stability, and epigenetic gene regulation that underpins developmental programs defining cell identity and fate. The site and degree of lysine methylation is dynamically modulated through the enzymatic activities of protein lysine methyltransferases (KMTs) and protein lysine demethylases (KDMs). These enzymes display distinct substrate specificities that in part define their biological functions. This review explores recent progress in elucidating the molecular basis of these specificities, highlighting structural and functional studies of the methyltransferases SUV4-20H1 (KMT5B), SUV4-20H2 (KMT5C), and ATXR5, and the demethylases UTX (KDM6A), JMJD3 (KDM6B), and JMJD2D (KDM4D). We conclude by examining these findings in the context of related KMTs and KDMs and by exploring unresolved questions regarding the specificities and functions of these enzymes.

Histone lysine-specific methyltransferases and demethylases in carcinogenesis: new targets for cancer therapy and prevention

Aberrant histone lysine methylation that is controlled by histone lysine methyltransferases (KMTs) and demethylases (KDMs) plays significant roles in carcinogenesis. Infections by tumor viruses or parasites and exposures to chemical carcinogens can modify the process of histone lysine methylation. Many KMTs and KDMs contribute to malignant transformation by regulating the expression of human telomerase reverse transcriptase (hTERT), forming a fused gene, interacting with proto-oncogenes or being up-regulated in cancer cells. In addition, histone lysine methylation participates in tumor suppressor gene inactivation during the early stages of carcinogenesis by regulating DNA methylation and/or by other DNA methylation independent mechanisms. Furthermore, recent genetic discoveries of many mutations in KMTs and KDMs in various types of cancers highlight their numerous roles in carcinogenesis and provide rare opportunities for selective and tumor-specific targeting of these enzymes. The study on global histone lysine methylation levels may also offer specific biomarkers for cancer detection, diagnosis and prognosis, as well as for genotoxic and non-genotoxic carcinogenic exposures and risk assessment. This review summarizes the role of histone lysine methylation in the process of cellular transformation and carcinogenesis, genetic alterations of KMTs and KDMs in different cancers and recent progress in discovery of small molecule inhibitors of these enzymes.

The demethylase JMJD2C localizes to H3K4me3-positive transcription start sites and is dispensable for embryonic development

The histone demethylase JMJD2C, also known as KDM4C/GASC1, has activity against methylated H3K9 and H3K36 and is amplified and/or overexpressed in human cancers. By the generation of Jmjd2c knockout mice, we demonstrate that loss of Jmjd2c is compatible with cellular proliferation, embryonic stem cell (ESC) self-renewal, and embryonic development. Moreover, we report that JMJD2C localizes to H3K4me3-positive transcription start sites in both primary cells and in the human carcinoma KYSE150 cell line containing an amplification of the JMJD2C locus. Binding is dependent on the double Tudor domain of JMJD2C, which recognizes H3K4me3 but not H4K20me2/me3 in vitro, showing a binding specificity different from that of the double Tudor domains of JMJD2A and JMJD2B. Depletion of JMJD2C in KYSE150 cells has a modest effect on H3K9me3 and H3K36me3 levels but impairs proliferation and leads to deregulated expression of a subset of target genes involved in cell cycle progression. Taking these findings together, we show that JMJD2C is targeted to H3K4me3-positive transcription start sites, where it can contribute to transcriptional regulation, and report that the putative oncogene JMJD2C generally is not required for cellular proliferation or embryonic development.

Phospho-ΔNp63α/microRNA network modulates epigenetic regulatory enzymes in squamous cell carcinomas

The tumor protein (TP) p63/microRNAs functional network may play a key role in supporting the response of squamous cell carcinomas (SCC) to chemotherapy. We show that the cisplatin exposure of SCC-11 cells led to upregulation of miR-297, miR-92b-3p, and miR-485-5p through a phosphorylated ΔNp63α-dependent mechanism that subsequently modulated the expression of the protein targets implicated in DNA methylation (DNMT3A), histone deacetylation (HDAC9), and demethylation (KDM4C). Further studies showed that mimics for miR-297, miR-92b-3p, or miR-485-5p, along with siRNA against and inhibitors of DNMT3A, HDAC9, and KDM4C modulated the expression of DAPK1, SMARCA2, and MDM2 genes assessed by the quantitative PCR, promoter luciferase reporter, and chromatin immunoprecipitation assays. Finally, the above-mentioned treatments affecting epigenetic enzymes also modulated the response of SCC cells to chemotherapeutic drugs, rendering the resistant SCC cells more sensitive to cisplatin exposure, thereby providing the groundwork for novel chemotherapeutic venues in treating patients with SCC.

Natural variation in the histone demethylase, KDM4C, influences expression levels of specific genes including those that affect cell growth

DNA sequence variants influence gene expression and cellular phenotypes. In this study, we focused on natural variation in the gene encoding the histone demethylase, KDM4C, which promotes transcriptional activation by removing the repressive histone mark, H3K9me3, from its target genes. We uncovered cis-acting variants that contribute to extensive individual differences in KDM4C expression. We also identified the target genes of KDM4C and demonstrated that variation in KDM4C expression leads to differences in the growth of normal and some cancer cells. Together, our results from genetic mapping and molecular analysis provide an example of how genetic variation affects epigenetic regulation of gene expression and cellular phenotype.

Inositol pyrophosphates regulate JMJD2C-dependent histone demethylation

Epigenetic modifications of chromatin represent a fundamental mechanism by which eukaryotic cells adapt their transcriptional response to developmental and environmental cues. Although an increasing number of molecules have been linked to epigenetic changes, the intracellular pathways that lead to their activation/repression have just begun to be characterized. Here, we demonstrate that inositol hexakisphosphate kinase 1 (IP6K1), the enzyme responsible for the synthesis of the high-energy inositol pyrophosphates (IP7), is associated with chromatin and interacts with Jumonji domain containing 2C (JMJD2C), a recently identified histone lysine demethylase. Reducing IP6K1 levels by RNAi or using mouse embryonic fibroblasts derived from ip6k1(-/-) knockout mice results in a decreased IP7 concentration that epigenetically translates to reduced levels of trimethyl-histone H3 lysine 9 (H3K9me3) and increased levels of acetyl-H3K9. Conversely, expression of IP6K1 induces JMJD2C dissociation from chromatin and increases H3K9me3 levels, which depend on IP6K1 catalytic activity. Importantly, these effects lead to changes in JMJD2C-target gene transcription. Our findings demonstrate that inositol pyrophosphate signaling influences nuclear functions by regulating histone modifications.

Structural investigations of the nickel-induced inhibition of truncated constructs of the JMJD2 family of histone demethylases using X-ray absorption spectroscopy

Occupational and/or environmental exposure to nickel has been implicated in various types of cancer, and in vitro exposure to nickel compounds results in the accumulation of Ni(II) ions in cells. One group of major targets of Ni(II) ions inside the cell consists of Fe(II)- and αKG-dependent dioxygenases. Using JMJD2A and JMJD2C as examples, we show that the JMJD2 family of histone demethylases, which are products of putative oncogenes as well as Fe(II)- and αKG-dependent dioxygenases, are highly sensitive to inhibition by Ni(II) ions. In this work, X-ray absorption spectroscopy (XAS) has been used to investigate the Fe(II) active site of truncated JMJD2A and JMJD2C (1-350 amino acids) in the presence and absence of αKG and/or substrate to obtain mechanistic details of the early steps in catalysis that precede O2 binding in histone demethylation by the JMJD2 family of histone demethylases. Zinc K-edge XAS has been performed on the resting JMJD2A (with iron in the active site) to confirm the presence of the expected structural zinc site. XAS of the Ni(II)-substituted enzymes has also been performed to investigate the inhibition of these enzymes by Ni(II) ions. Our XAS results indicate that the five-coordinate Fe(II) center in the resting enzyme is retained in the binary and ternary complexes. In contrast, the Ni(II) center is six-coordinate in the resting enzyme and binary and ternary complexes. XAS results indicate that both Fe(II) and Ni(II) bind αKG in the binary and ternary complexes. The electron density buildup that is observed at the Fe(II) center in the presence of αKG and substrate is not observed at the Ni(II) center. Thus, both electronic and steric factors are responsible for Ni-induced inhibition of the JMJD2 family of histone demethylases. Ni-induced inhibition of these enzymes may explain the alteration of the epigenetic mechanism of gene expression that is responsible for Ni-induced carcinogenesis.

KDM5B histone demethylase controls epithelial-mesenchymal transition of cancer cells by regulating the expression of the microRNA-200 family

Histone methylation is implicated in various biological and pathological processes including cancer development. In this study, we discovered that ectopic expression of KDM5B, a histone H3 lysine 4 (H3K4) demethylase, promoted epithelial-mesenchymal transition (EMT) of cancer cells. KDM5B increased the expression of transcription factors, ZEB1 and ZEB2, followed by downregulation of E-cadherin and upregulation of mesenchymal marker genes. The expression of the microRNA-200 (miR-200) family, which specifically targets ZEB1 and ZEB2, was reduced in the cells with KDM5B overexpression. We found that KDM5B repressed the expression of the miR-200 family by changing histone H3 methylation status of their regulatory regions. The introduction of miR-200 precursor in the cells inhibited EMT induction by KDM5B, suggesting that miR-200 family was a critical downstream mediator of KDM5B-promoted EMT. Furthermore, knockdown of KDM5B was shown to affect the expression of EMT-related genes, indicating the involvement of endogenous KDM5B. Our study demonstrated a novel role of KDM5B histone lysine demethylase in EMT, which may contribute to malignant progression of cancer.

Roles of histone methyl-modifying enzymes in development and progression of cancer

Retroviral insertional mutagenesis in mice is considered a powerful forward genetic strategy to identify disease genes involved in cancer. Our high-throughput screens led to frequent identification of the genes encoding the enzymes engaged in histone lysine methylation. Histone methylation can positively or negatively impact on gene transcription, and then fulfill important roles in developmental control and cell-fate decisions. A tremendous amount of progress has accelerated the characterization of histone methylations and the enzymes that regulate them. Deregulation of these histone methyl-modifying enzymes has been increasingly recognized as a hallmark of cancer in the last few years. However, in most cases, we have only limited understanding for the molecular mechanisms by which these enzymes contribute to cancer development and progression. In this review, we summarize the current knowledge regarding some of the best-validated examples of histone lysine methyltransferases and demethylases associated with oncogenesis and discuss their potential mechanisms of action.

Heat shock protein 90 (Hsp90) selectively regulates the stability of KDM4B/JMJD2B histone demethylase

The family of KDM4A-D histone demethylases selectively demethylates H3K9 and H3K36 and is implicated in key cellular processes including DNA damage response, transcription, cell cycle regulation, cellular differentiation, senescence, and carcinogenesis. Various human cancers exhibit elevated protein levels of KDM4A-D members, and their depletion impairs tumor formation, suggesting that their enhanced activity promotes carcinogenesis. However, the mechanisms regulating the KDM4 protein stability remain largely unknown. Here, we show that the molecular chaperon Hsp90 interacts with and stabilizes KDM4B protein. Pharmacological inhibition of Hsp90 with geldanamycin resulted in ubiquitin-dependent proteasomal degradation of KDM4B, but not of KDM4C, suggesting that the turnover of these demethylases is regulated by distinct mechanisms. This degradation was accompanied by increased methylation of H3K9. We further show that KDM4B is ubiquitinated on lysines 337 and 562; simultaneous substitution of these residues to arginine suppressed the geldanamycin-induced degradation of KDM4B, suggesting that the ubiquitination of Lys-337 and Lys-562 targets KDM4B for proteasomal degradation upon Hsp90 inhibition. These findings constitute a novel pathway by which Hsp90 activity alters the histone code via regulation of KDM4B stability. This pathway may prove a druggable target for the treatment of tumors driven by enhanced KDM4B activity.

The lysine demethylase, KDM4B, is a key molecule in androgen receptor signalling and turnover

The androgen receptor (AR) is a key molecule involved in prostate cancer (PC) development and progression. Post-translational modification of the AR by co-regulator proteins can modulate its transcriptional activity. To identify which demethylases might be involved in AR regulation, an siRNA screen was performed to reveal that the demethylase, KDM4B, may be an important co-regulator protein. KDM4B enzymatic activity is required to enhance AR transcriptional activity; however, independently of this activity, KDM4B can enhance AR protein stability via inhibition of AR ubiquitination. Importantly, knockdown of KDM4B in multiple cell lines results in almost complete depletion of AR protein levels. For the first time, we have identified KDM4B to be an androgen-regulated demethylase enzyme, which can influence AR transcriptional activity not only via demethylation activity but also via modulation of ubiquitination. Together, these findings demonstrate the close functional relationship between AR and KDM4B, which work together to amplify the androgen response. Furthermore, KDM4B expression in clinical PC specimens positively correlates with increasing cancer grade (P < 0.001). Consequently, KDM4B is a viable therapeutic target in PC.

Histone demethylase GASC1, a potential prognostic and predictive marker in esophageal squamous cell carcinoma

Gene amplified in squamous cell carcinoma 1 (GASC1) is a member of Jumonji C-domain containing histone demethylases that play an essential role in affecting chromatin architecture and gene expression. The purpose of this study was to determine the expression features and the clinical significance of GASC1 in esophageal squamous cell carcinoma (ESCC). GASC1 expression was detected on tissue microarrays of ESCC samples in 185 cases using immunohistochemical staining. Strong nuclear staining for GASC1 was observed in a subset of ESCC samples. The nuclear expression of GASC1 was significantly associated with lymph node metastasis (P=0.030) and tumor-node metastasis stages (P=0.013). Kaplan-Meier survival analysis showed a tendency that high expression of GASC1 in the nucleus was associated with poor survival of ESCC patients, with a 5-year survival rate of 26.5%, as compared to 43.7% for patients with GASC1-negative/low expression. Furthermore, multivariate analysis revealed that high expression of GASC1 likely acts as a predictive factor for overall survival of ESCC patients, despite the P-value failing to reach significance (P=0.059). The findings indicate that histone demethylase GASC1 may play an important role in promoting cancer metastasis, and shed new light on the importance of targeting GASC1 to suppress metastatic disease in various tumor types, including ESCC.

Structural and functional analysis of JMJD2D reveals molecular basis for site-specific demethylation among JMJD2 demethylases

JMJD2 lysine demethylases (KDMs) participate in diverse genomic processes. Most JMJD2 homologs display dual selectivity toward H3K9me3 and H3K36me3, with the exception of JMJD2D, which is specific for H3K9me3. Here, we report the crystal structures of the JMJD2D⋅2-oxoglutarate⋅H3K9me3 ternary complex and JMJD2D apoenzyme. Utilizing structural alignments with JMJD2A, molecular docking, and kinetic analysis with an array of histone peptide substrates, we elucidate the specific signatures that permit efficient recognition of H3K9me3 by JMJD2A and JMJD2D, and the residues in JMJD2D that occlude H3K36me3 demethylation. Surprisingly, these results reveal that JMJD2A and JMJD2D exhibit subtle yet important differences in H3K9me3 recognition, despite the overall similarity in the substrate-binding conformation. Further, we show that H3T11 phosphorylation abrogates demethylation by JMJD2 KDMs. Together, these studies reveal the molecular basis for JMJD2 site specificity and provide a framework for structure-based design of selective inhibitors of JMJD2 KDMs implicated in disease.

The oncogenic potential of Jumonji D2 (JMJD2/KDM4) histone demethylase overexpression

The Jumonji D2 proteins (JMJD2/KDM4) function to demethylate di- and trimethylated (me2/3) histone 3 lysine 9 (H3K9me2/3) and H3K36me3. Knockout mouse models for Kdm4b and Kdm4d have not resulted in gross abnormalities, while mouse models for Kdm4a and Kdm4c have not been reported. However, the KDM4 subfamily of demethylases are overexpressed in several tumor types. Overexpression of KDM4 proteins alters transcription and chromatin remodeling, driving cellular proliferation, anchorage-independent growth, invasion, and migration. Increased proliferation occurs through KDM4-mediated modification of cell cycle timing, as well as through increased numbers of replication forks. Recent evidence also suggests that KDM4C overexpression contributes to the maintenance of a pluripotent state. Together these data suggest that overexpression of KDM4 proteins induces numerous oncogenic effects.

Oncoepigenomics: making histone lysine methylation count

Increasing studies show that methylation of histone lysine residues is implicated in the development and progression of varying disease states such as schizophrenia, diabetes, and multiple human cancers. Targeting the specific enzymes responsible for these processes has fueled global investigation into the understanding and correction of epigenetic pathology. This review aims to assemble a timely account of the current progress against chromatin-modifying histone lysine methyltransferases (KMTs) and demethylases (KDMs) to inform ongoing and future efforts into this promising field. In particular, we report on their role in tumor growth and progression and the development of small molecules that modulate these enzymes.

Loss of microRNA-143/145 disturbs cellular growth and apoptosis of human epithelial cancers by impairing the MDM2-p53 feedback loop

Dysregulated microRNAs (miRNAs) have an important role in many malignant tumors. However, elucidating the roles of miRNAs in cancer biology, especially in epithelial cancers, remains an ongoing process. In this study, we show that both miR-143 and miR-145, which belong to the same miRNA cluster, can negatively modulate expression of their target gene, MDM2. The miR-143 and miR-145 is posttranscriptionally activated by upregulated p53, thereby generating a short miRNAs-MDM2-p53 feedback loop. Re-expression of these miRNAs suppresses cellular growth and triggers the apoptosis of epithelial cancer, in vitro and in vivo, by enhancing p53 activity via MDM2 turnover. Moreover, the miRNA-dependent MDM2 turnover contributes to the equilibrium of repeated p53 pulses in response to DNA damage stress. These findings suggest that MDM2 dysregulation caused by downregulation of miR-143 and miR-145 contributes to epithelial cancer development and has a key role in regulating cellular proliferation and apoptosis. Re-expression of miR-143 and miR-145 may be a reasonable strategy for treatment of epithelial cancers.

Structural and evolutionary basis for the dual substrate selectivity of human KDM4 histone demethylase family

N(ε)-Methylations of histone lysine residues play critical roles in cell biology by "marking" chromatin for transcriptional activation or repression. Lysine demethylases reverse N(ε)-methylation in a sequence- and methylation-selective manner. The determinants of sequence selectivity for histone demethylases have been unclear. The human JMJD2 (KDM4) H3K9 and H3K36 demethylases can be divided into members that act on both H3K9 and H3K36 and H3K9 alone. Kinetic, crystallographic, and mutagenetic studies in vitro and in cells on KDM4A-E reveal that selectivity is determined by multiple interactions within the catalytic domain but outside the active site. Structurally informed phylogenetic analyses reveal that KDM4A-C orthologues exist in all genome-sequenced vertebrates with earlier animals containing only a single KDM4 enzyme. KDM4D orthologues only exist in eutherians (placental mammals) where they are conserved, including proposed substrate sequence-determining residues. The results will be useful for the identification of inhibitors for specific histone demethylases.

PLU1 histone demethylase decreases the expression of KAT5 and enhances the invasive activity of the cells

PLU1 is a candidate oncogene that encodes H3K4 (Lys4 of histone H3) demethylase. In the present study, we found that ectopic expression of PLU1 enhanced the invasive potential of the weakly invasive cells dependent on its demethylase activity. PLU1 was shown to repress the expression of the KAT5 gene through its H3K4 demethylation on the promoter. The regulation of KAT5 by PLU1 was suggested to be responsible for PLU1-induced cell invasion. First, knockdown of KAT5 similarly increased the invasive potential of the cells. Secondly, knockdown of PLU1 in the highly invasive cancer cells increased KAT5 expression and reduced the invasive activity. Thirdly, simultaneous knockdown of KAT5 partially relieved the suppression of cell invasion imposed by PLU1 knockdown. Finally, we found that CD82, which was transcriptionally regulated by KAT5, might be a candidate effector of cell invasion promoted by PLU1. The present study demonstrated a functional contribution of PLU1 overexpression with concomitant epigenetic dysregulation in cancer progression.

Identification and functional analysis of 9p24 amplified genes in human breast cancer

Previously, our group identified a novel amplicon at chromosome 9p24 in human esophageal and breast cancers, and cloned the novel gene, GASC1 (gene amplified in squamous cell carcinoma 1, also known as JMJD2C/KDM4C), from this amplicon. GASC1 is a histone demethylase involved in the deregulation of histone methylation in cancer cells. In the current study, we aimed to comprehensively characterize the genes in the 9p24 amplicon in human breast cancer. We performed extensive genomic analyses on a panel of cancer cell lines and narrowed the shortest region of overlap to approximately 2 Mb. Based on statistical analysis of copy number increase and overexpression, the 9p24 amplicon contains six candidate oncogenes. Among these, four genes (GASC1 UHRF2, KIAA1432 and C9orf123) are overexpressed only in the context of gene amplification while two genes (ERMP1 and IL33) are overexpressed independent of the copy number increase. We then focused our studies on the UHRF2 gene, which has a potential involvement in both DNA methylation and histone modification. Knocking down UHRF2 expression inhibited the growth of breast cancer cells specifically with 9p24 amplification. Conversely, ectopic overexpression of UHRF2 in non-tumorigenic MCF10A cells promoted cell proliferation. Furthermore, we demonstrated that UHRF2 has the ability to suppress the expression of key cell-cycle inhibitors, such as p16(INK4a), p21(Waf1/Cip1) and p27(Kip1). Taken together, our studies support the notion that the 9p24 amplicon contains multiple oncogenes that may integrate genetic and epigenetic codes and have important roles in human tumorigenesis.

Design, synthesis, enzyme-inhibitory activity, and effect on human cancer cells of a novel series of jumonji domain-containing protein 2 histone demethylase inhibitors

Selective inhibitors of Jumonji domain-containing protein (JMJD) histone demethylases are candidate anticancer agents as well as potential tools for elucidating the biological functions of JMJDs. On the basis of the crystal structure of JMJD2A and a homology model of JMJD2C, we designed and prepared a series of hydroxamate analogues bearing a tertiary amine. Enzyme assays using JMJD2C, JMJD2A, and prolyl hydroxylases revealed that hydroxamate analogue 8 is a potent and selective JMJD2 inhibitor, showing 500-fold greater JMJD2C-inhibitory activity and more than 9100-fold greater JMJD2C-selectivity compared with the lead compound N-oxalylglycine 2. Compounds 17 and 18, prodrugs of compound 8, each showed synergistic growth inhibition of cancer cells in combination with an inhibitor of lysine-specific demethylase 1 (LSD1). These findings suggest that combination treatment with JMJD2 inhibitors and LSD1 inhibitors may represent a novel strategy for anticancer chemotherapy.

The tumor suppressor Rb and its related Rbl2 genes are regulated by Utx histone demethylase

Utx is a candidate tumor suppressor gene that encodes histone H3 lysine 27 (H3K27) demethylase. In this study, we found that ectopic expression of Utx enhanced the expression of retinoblastoma tumor suppressor gene Rb and its related gene Rbl2. This activation was dependent on the demethylase activity of Utx, and was suggested to contribute to the decreased cell proliferation induced by Utx. A chromatin immunoprecipitation assay showed that over-expressed Utx was associated with the promoter regions of Rb and Rbl2 resulting in the removal of repressive H3K27 tri-methylation and the increase in active H3K4 tri-methylation. Furthermore, siRNA-mediated knockdown of Utx revealed the recruitment of endogenous Utx protein on the promoters of Rb and Rbl2 genes. These results indicate that Rb and Rbl2 are downstream target genes of Utx and may play important roles in Utx-mediated cell growth control.