Jumonji histone demethylases as emerging therapeutic targets

Tumor-stromal metabolic crosstalk in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy with a dire prognosis. Standard-of-care chemotherapy regimens offer marginal survival benefit and carry risk of severe toxicity, while immunotherapy approaches have uniformly failed in clinical trials. Extensive desmoplasia in the PDAC tumor microenvironment (TME) disrupts blood flow to and from the tumor, thereby creating a nutrient-depleted, hypoxic, and acidic milieu that suppresses the function of antitumor immune cells and imparts chemotherapy resistance. Additionally, recent seminal studies have demonstrated crucial roles for metabolic crosstalk - the exchange of metabolites between PDAC cells and stromal cell populations in the TME - in establishing and maintaining core malignant behaviors of PDAC: tumor growth, metastasis, immune evasion, and therapy resistance. In this review, we provide a conceptual overview of metabolic crosstalk and how it evolves under various selection pressures in the TME, analyze the landscape of proposed tumorigenic metabolic crosstalk pathways, and highlight potentially druggable nodes.

Insights into the role of histone lysine demethylases in bone homeostasis and skeletal diseases: A review

Histone lysine demethylases (KDMs), as important epigenetic regulators, are involved in various biological processes such as energy metabolism, apoptosis, and autophagy. Recent research shows that KDMs activate or silence downstream target genes by removing lysine residues from histone tails, and participate in the regulation of bone marrow mesenchymal stem cells (BM-MSCs), osteoblasts (OB), osteoclasts (OC), chondrocytes and other skeletal cell development, differentiation and formation. Moreover, several members of the KDM family affect the occurrence and development of bone diseases such as osteoporosis (OP), osteoarthritis (OA), osteosarcoma (OS), by regulating target genes. Specific regulation mechanisms of KDMs suggest new strategies for bone disease treatment and prevention. Despite the unique function and importance of KDMs in the skeletal system, previous studies have never systematically summarized their specific role, molecular mechanism, and clinical treatment in bone physiology and pathology. Therefore, this review summarises the expression pattern, intracellular signal transduction, and mechanism of action of the KDM family in several bone physiological and pathological conditions, aiming to highlight the important role of KDMs in bone diseases and provide a reference for the future treatment of bone diseases.

Endothelial KDM5B Regulated by Piezo1 Contributes to Disturbed Flow Induced Atherosclerotic Plaque Formation

Epigenetic modifications play an important role in disturbed flow (d-flow) induced atherosclerotic plaque formation. By analysing a scRNA-seq dataset of the left carotid artery (LCA) under d-flow conditions, we found that Jarid1b (KDM5B) was upregulated primarily in a subcluster of endothelial cells in response to d-flow stimulation. We therefore investigated the mechanism of KDM5B expression and the role of KDM5B in endothelial cell. Intriguingly, activation of Piezo1, a major endothelial mechanosensor, was found to promote KDM5B expression, which was reversed by Piezo1 inhibition in HUVECs. Downstream of Piezo1, ETS1 expression and c-JUN phosphorylation were enhanced by d-flow or Piezo1 activation, leading to an increase in KDM5B expression. Furthermore, knockdown of either KDM5B or Piezo1 was found to prevent d-flow induced H3K4me3 demethylation, which was supported by the pharmacological inhibition of Piezo1 in HUVECs. RNA sequencing on shKdm5b HUVECs implied that KDM5B is associated with endothelial inflammation and atherosclerosis. Using partial carotid ligation surgery on Kdm5bf/f Cdh5cre mice with mAAV-PCSK9D377Y infected, we showed that endothelial KDM5B deficiency reduced atherosclerotic lesions in hypercholesterolemic mice. Our findings indicate that endothelial KDM5B expression induced by d-flow via the Piezo1 pathway promotes atherosclerotic plaque formation, providing targets for the prevention or therapeutic intervention of atherosclerosis.

Stage-Specific Alteration and Prognostic Relationship of Serum Fumarate Hydratase Autoantibodies in Gastric Cancer

The relationship between energy production and cancer is attracting attention. This study aimed to investigate the clinicopathological significance of fumarate hydratase (FH), a tricarboxylic acid cycle enzyme, in gastric cancer using autoantibodies as biomarkers. The study analyzed 116 patients who underwent gastric cancer surgery and 96 healthy controls. Preoperative serum FH autoantibody (s-FH-Ab) titers were analyzed using an immunosorbent assay with an amplified luminescent proximity homogeneous assay. Receiver operating characteristic analysis was used to determine the cutoff s-FH-Ab titer. Clinicopathological factors and prognosis were compared between the high and low s-FH-Ab groups. The s-FH-Ab levels were significantly higher in the gastric cancer group than in the control group (p = 0.01). Levels were elevated even in patients with stage I gastric cancer compared with healthy controls (p = 0.02). A low s-FH-Ab level was significantly associated with distant metastasis (p = 0.01), peritoneal dissemination (p < 0.05), and poor overall survival (p < 0.01). Multivariate analysis revealed that low s-FH-Ab levels were an independent risk factor for poor prognosis (p < 0.01). Therefore, s-FH-Ab levels may be a useful biomarker for early diagnosis and the prediction of prognosis in patients with gastric cancer.

Histone demethylase KDM7A regulates bone homeostasis through balancing osteoblast and osteoclast differentiation

Histone methylation plays a crucial role in various cellular processes. We previously reported the in vitro function of histone lysine demethylase 7 A (KDM7A) in osteoblast and adipocyte differentiation. The current study was undertaken to investigate the physiological role of KDM7A in bone homeostasis and elucidate the underlying mechanisms. A conditional strategy was employed to delete the Kdm7a gene specifically in osterix-expressing osteoprogenitor cells in mice. The resulting mutant mice exhibited a significant increase in cancellous bone mass, accompanied by an increase in osteoblasts and bone formation, as well as a reduction in osteoclasts, marrow adipocytes and bone resorption. The bone marrow stromal cells (BMSCs) and calvarial pre-osteoblastic cells derived from the mutant mice exhibited enhanced osteogenic differentiation and suppressed adipogenic differentiation. Additionally, osteoclastic precursor cells from the mutant mice exhibited impaired osteoclast differentiation. Co-culturing BMSCs from the mutant mice with wild-type osteoclast precursor cells resulted in the inhibition of osteoclast differentiation. Mechanistic investigation revealed that KDM7A was able to upregulate the expression of fibroblast activation protein α (FAP) and receptor activator of nuclear factor κB ligand (RANKL) in BMSCs through removing repressive di-methylation marks of H3K9 and H3K27 from Fap and Rankl promoters. Moreover, recombinant FAP attenuated the dysregulation of osteoblast and adipocyte differentiation in BMSCs from Kdm7a deficient mice. Finally, Kdm7a deficiency prevented ovariectomy-induced bone loss in mice. This study establish the role of KDM7A in bone homeostasis through its epigenetic regulation of osteoblast and osteoclast differentiation. Consequently, inhibiting KDM7A may prove beneficial in ameliorating osteoporosis. KDM7A suppresses osteoblast differentiation and bone formation through. upregulating FAP expression and inactivating canonical Wnt signaling, and conversely promotes osteoclast differentiation and bone resorption through upregulating RANKL expression. These are based on its epigenetic removal of the repressive H3K9me2 and H3K27me2 marks from Fap and Rankl promoters. As a result, the expression of KDM7A in osteoprogenitor cells tends to negatively modulate bone mass.

Recent discoveries of the role of histone modifications and related inhibitors in pathological cardiac hypertrophy

Pathological cardiac hypertrophy is a common response of the heart to various pathological stimuli. In recent years, various histone modifications, including acetylation, methylation, phosphorylation and ubiquitination, have been identified to have crucial roles in regulating chromatin remodeling and cardiac hypertrophy. Novel drugs targeting these epigenetic changes have emerged as potential treatments for pathological cardiac hypertrophy. In this review, we provide a comprehensive summary of the roles of histone modifications in regulating the development of pathological cardiac hypertrophy, and discuss potential therapeutic targets that could be utilized for its treatment.

Recent developments in catalysis and inhibition of the Jumonji histone demethylases

Histone methylation, one of the most common histone modifications, has fundamental roles in regulating chromatin-based processes. Jumonji histone lysine demethylases (JMJC KDMs) influence regulation of gene transcription through both their demethylation and chromatin scaffolding functions. It has recently been demonstrated that dysregulation of JMJC KDMs contributes to pathogenesis and progression of several diseases, including cancer. These observations have led to an increased interest in modulation of enzymes that regulate lysine methylation. Here, we highlight recent progress in understanding catalysis of JMJC KDMs. Specifically, we focus on recent research advances on elucidation of JMJC KDM substrate recognition and interactomes. We also highlight recently reported JMJC KDM inhibitors and describe their therapeutic potentials and challenges. Finally, we discuss alternative strategies to target these enzymes, which rely on targeting JMJC KDMs accessory domains as well as utilization of the targeted protein degradation strategy.

Native lamin A/C proteomes and novel partners from heart and skeletal muscle in a mouse chronic inflammation model of human frailty

Clinical frailty affects ∼10% of people over age 65 and is studied in a chronically inflamed (Interleukin-10 knockout; "IL10-KO") mouse model. Frailty phenotypes overlap the spectrum of diseases ("laminopathies") caused by mutations in LMNA. LMNA encodes nuclear intermediate filament proteins lamin A and lamin C ("lamin A/C"), important for tissue-specific signaling, metabolism and chromatin regulation. We hypothesized that wildtype lamin A/C associations with tissue-specific partners are perturbed by chronic inflammation, potentially contributing to dysfunction in frailty. To test this idea we immunoprecipitated native lamin A/C and associated proteins from skeletal muscle, hearts and brains of old (21-22 months) IL10-KO versus control C57Bl/6 female mice, and labeled with Tandem Mass Tags for identification and quantitation by mass spectrometry. We identified 502 candidate lamin-binding proteins from skeletal muscle, and 340 from heart, including 62 proteins identified in both tissues. Candidates included frailty phenotype-relevant proteins Perm1 and Fam210a, and nuclear membrane protein Tmem38a, required for muscle-specific genome organization. These and most other candidates were unaffected by IL10-KO, but still important as potential lamin A/C-binding proteins in native heart or muscle. A subset of candidates (21 in skeletal muscle, 30 in heart) showed significantly different lamin A/C-association in an IL10-KO tissue (p < 0.05), including AldoA and Gins3 affected in heart, and Lmcd1 and Fabp4 affected in skeletal muscle. To screen for binding, eleven candidates plus prelamin A and emerin controls were arrayed as synthetic 20-mer peptides (7-residue stagger) and incubated with recombinant purified lamin A "tail" residues 385-646 under relatively stringent conditions. We detected strong lamin A binding to peptides solvent exposed in Lmcd1, AldoA, Perm1, and Tmem38a, and plausible binding to Csrp3 (muscle LIM protein). These results validated both proteomes as sources for native lamin A/C-binding proteins in heart and muscle, identified four candidate genes for Emery-Dreifuss muscular dystrophy (CSRP3, LMCD1, ALDOA, and PERM1), support a lamin A-interactive molecular role for Tmem38A, and supported the hypothesis that lamin A/C interactions with at least two partners (AldoA in heart, transcription factor Lmcd1 in muscle) are altered in the IL10-KO model of frailty.

Cyclic peptides target the aromatic cage of a PHD-finger reader domain to modulate epigenetic protein function

Plant homeodomain fingers (PHD-fingers) are a family of reader domains that can recruit epigenetic proteins to specific histone modification sites. Many PHD-fingers recognise methylated lysines on histone tails and play crucial roles in transcriptional regulation, with their dysregulation linked to various human diseases. Despite their biological importance, chemical inhibitors for targeting PHD-fingers are very limited. Here we report a potent and selective de novo cyclic peptide inhibitor (OC9) targeting the Nε-trimethyllysine-binding PHD-fingers of the KDM7 histone demethylases, developed using mRNA display. OC9 disrupts PHD-finger interaction with histone H3K4me3 by engaging the Nε-methyllysine-binding aromatic cage through a valine, revealing a new non-lysine recognition motif for the PHD-fingers that does not require cation-π interaction. PHD-finger inhibition by OC9 impacted JmjC-domain mediated demethylase activity at H3K9me2, leading to inhibition of KDM7B (PHF8) but stimulation of KDM7A (KIAA1718), representing a new approach for selective allosteric modulation of demethylase activity. Chemoproteomic analysis showed selective engagement of OC9 with KDM7s in T cell lymphoblastic lymphoma SUP T1 cells. Our results highlight the utility of mRNA-display derived cyclic peptides for targeting challenging epigenetic reader proteins to probe their biology, and the broader potential of this approach for targeting protein-protein interactions.

Phosphorylation of PHF2 by AMPK releases the repressive H3K9me2 and inhibits cancer metastasis

Epithelial to mesenchymal transition (EMT) plays a crucial role in cancer metastasis, accompanied with vast epigenetic changes. AMP-activated protein kinase (AMPK), a cellular energy sensor, plays regulatory roles in multiple biological processes. Although a few studies have shed light on AMPK regulating cancer metastasis, the inside epigenetic mechanisms remain unknown. Herein we show that AMPK activation by metformin relieves the repressive H3K9me2-mediated silencing of epithelial genes (e.g., CDH1) during EMT processes and inhibits lung cancer metastasis. PHF2, a H3K9me2 demethylase, was identified to interact with AMPKα2. Genetic deletion of PHF2 aggravates lung cancer metastasis and abolishes the H3K9me2 downregulation and anti-metastasis effect of metformin. Mechanistically, AMPK phosphorylates PHF2 at S655 site, enhancing PHF2 demethylation activity and triggering the transcription of CDH1. Furthermore, the PHF2-S655E mutant that mimics AMPK-mediated phosphorylation status further reduces H3K9me2 and suppresses lung cancer metastasis, while PHF2-S655A mutant presents opposite phenotype and reverses the anti-metastasis effect of metformin. PHF2-S655 phosphorylation strikingly reduces in lung cancer patients and the higher phosphorylation level predicts better survival. Altogether, we reveal the mechanism of AMPK inhibiting lung cancer metastasis via PHF2 mediated H3K9me2 demethylation, thereby promoting the clinical application of metformin and highlighting PHF2 as the potential epigenetic target in cancer metastasis.

Development of JmjC-domain-containing histone demethylase (KDM2-7) inhibitors for cancer therapy

Histone methylation is the most common histone modification and a highly dynamic regulator of gene transcription. Methylation of lysine residues can alter the structure of chromatin, helping to regulate DNA-based nuclear activities. Lysine demethylases control and maintain epigenetic factors that affect chromatin structure and cell characteristics. A variety of diseases, including malignant tumors, are connected to their dysregulation. Advances in biochemistry and pathogenesis have prompted the discovery of small molecule inhibitors and tool compounds that disrupt lysine demethylation. In this review, we focus on JmjC-domain-containing histone lysine demethylases (KDM2-7), discussing their structures and biological roles, representative inhibitors, and therapeutic potential in cancer therapy, and aiming to provide unique insights into the development of JmjC-KDM inhibitors.

Inhibitors of Jumonji C domain-containing histone lysine demethylases overcome cisplatin and paclitaxel resistance in non-small cell lung cancer through APC/Cdh1-dependent degradation of CtIP and PAF15

The Jumonji C domain-containing family of histone lysine demethylases (Jumonji KDMs) have emerged as promising cancer therapy targets. These enzymes remove methyl groups from various histone lysines and, in turn, regulate processes including chromatin compaction, gene transcription, and DNA repair. Small molecule inhibitors of Jumonji KDMs have shown promise in preclinical studies against non-small cell lung cancer (NSCLC) and other cancers. However, how these inhibitors influence cancer therapy responses and/or DNA repair is incompletely understood. In this study, we established cell line and PDX tumor model systems of cisplatin and paclitaxel-resistant NSCLC. We showed that resistant cells and tumors express high levels of Jumonji-KDMs. Knockdown of individual KDMs or treatment with a pan-Jumonji KDM inhibitor sensitized the cells and tumors to cisplatin and paclitaxel and blocked NSCLC in vivo tumor growth. Mechanistically, we found inhibition of Jumonji-KDMs triggers APC/Cdh1-dependent degradation of CtIP and PAF15, two DNA repair proteins that promote repair of cisplatin and paclitaxel-induced DNA lesions. Knockdown of CtIP and PAF15 sensitized resistant cells to cisplatin, indicating their degradation when Jumonji KDMs are inhibited contributes to cisplatin sensitivity. Our results support the idea that Jumonji-KDMs are a targetable barrier to effective therapy responses in NSCLC. Inhibition of Jumonji KDMs increases therapy (cisplatin/paclitaxel) sensitivity in NSCLC cells, at least in part, by promoting APC/Cdh1-dependent degradation of CtIP and PAF15.

Targeting Krebs-cycle-deficient renal cell carcinoma with Poly ADP-ribose polymerase inhibitors and low-dose alkylating chemotherapy

Loss-of-function mutations in genes encoding the Krebs cycle enzymes Fumarate Hydratase (FH) and Succinate Dehydrogenase (SDH) induce accumulation of fumarate and succinate, respectively and predispose patients to hereditary cancer syndromes including the development of aggressive renal cell carcinoma (RCC). Fumarate and succinate competitively inhibit αKG-dependent dioxygenases, including Lysine-specific demethylase 4A/B (KDM4A/B), leading to suppression of the homologous recombination (HR) DNA repair pathway. In this study, we have developed new syngeneic Fh1- and Sdhb-deficient murine models of RCC, which demonstrate the expected accumulation of fumarate and succinate, alterations in the transcriptomic and methylation profile, and an increase in unresolved DNA double-strand breaks (DSBs). The efficacy of poly ADP-ribose polymerase inhibitors (PARPis) and temozolomide (TMZ), alone and in combination, was evaluated both in vitro and in vivo. Combination treatment with PARPi and TMZ results in marked in vitro cytotoxicity in Fh1- and Sdhb-deficient cells. In vivo, treatment with standard dosing of the PARP inhibitor BGB-290 and low-dose TMZ significantly inhibits tumor growth without a significant increase in toxicity. These findings provide the basis for a novel therapeutic strategy exploiting HR deficiency in FH and SDH-deficient RCC with combined PARP inhibition and low-dose alkylating chemotherapy.

Targeting histone demethylases as a potential cancer therapy (Review)

Post‑translational modifications of histones by histone demethylases have an important role in the regulation of gene transcription and are implicated in cancers. Recently, the family of lysine (K)‑specific demethylase (KDM) proteins, referring to histone demethylases that dynamically regulate histone methylation, were indicated to be involved in various pathways related to cancer development. To date, numerous studies have been conducted to explore the effects of KDMs on cancer growth, metastasis and drug resistance, and a majority of KDMs have been indicated to be oncogenes in both leukemia and solid tumors. In addition, certain KDM inhibitors have been developed and have become the subject of clinical trials to explore their safety and efficacy in cancer therapy. However, most of them focus on hematopoietic malignancy. This review summarizes the effects of KDMs on tumor growth, drug resistance and the current status of KDM inhibitors in clinical trials.

KDM5B promotes tumorigenesis of Ewing sarcoma via FBXW7/CCNE1 axis

Ewing sarcoma (EwS) is an aggressive tumor that affects children and young adults. Patients with relapsed/refractory diseases have limited treatment options. Targeting the driver fusion oncoproteins of EwS remains a technical problem. Epigenetic mechanisms have been pointed out as key players and alternative therapeutic targets in EwS. Here, we reported that lysine demethylase 5B (KDM5B), a histone demethylase that specifically demethylates tri- and di-methylated H3 Lys-4 (H3K4), was upregulated in EwS and overexpressed KDM5B was correlated with poor outcomes of patients. KDM5B knockdown and KDM5B inhibitor AS-8351 suppressed EwS cell proliferation and induced cell cycle arrest. Bioinformatics analysis revealed that KDM5B mainly influenced the cell cycle pathways in EwS. In mechanistic studies, we found that overexpression of KDM5B resulted in increased CCNE1 protein level, but did not affect the mRNA level of CCNE1. KDM5B upregulation blocked the degradation pathway of CCNE1 by reducing the expression of FBXW7. KDM5B downregulated FBXW7 gene by demethylation of H3K4me3 at promoter region. Moreover, AS-8351 could inhibit tumor growth in nude mice models, indicating the antitumor effect of targeting KDM5B in EwS. Our study uncovered that KDM5B in EwS attenuated FBXW7 transcription and accumulated CCNE1 protein, leading to malignant proliferation of EwS. Epigenetic drug targeting KDM5B could be a potential treatment for EwS.

BIX01294 inhibits EGFR signaling in EGFR-mutant lung adenocarcinoma cells through a BCKDHA-mediated reduction in the EGFR level

BIX01294 (BIX), an inhibitor of the G9a histone methyltransferase, has been reported to have antitumor activity against a variety of cancers. However, the molecular mechanisms underlying its anticancer effects, particularly those against lung cancer, remain unclear. Here, we report that BIX induces apoptotic cell death in EGFR-mutant non-small cell lung cancer (NSCLC) cells but not in their wild-type counterparts. Treatment with BIX resulted in a significant reduction in the EGFR level and inhibition of EGFR signaling only in EGFR-mutant NSCLC cells, leading to apoptosis. BIX also inhibited mitochondrial metabolic function and decreased the cellular energy levels that are critical for maintaining the EGFR level. Furthermore, BIX transcriptionally downregulated the transcription of branched-chain α-keto acid dehydrogenase (BCKDHA), which is essential for fueling the tricarboxylic acid (TCA) cycle. Interestingly, this BCKDHA downregulation was due to inhibition of Jumanji-domain histone demethylases but not the G9a histone methyltransferase. We observed that KDM3A, a Jumonji histone demethylase, epigenetically regulates BCKDHA expression by binding to the BCKDHA gene promoter. BIX exposure also led to a significant decrease in the EGFR level, causing apoptosis in EGFR-TKI (tyrosine kinase inhibitor)-resistant cell lines, which are dependent on EGFR signaling for survival. Taken together, our current data suggest that BIX triggers apoptosis only in EGFR-mutant NSCLC cells via inhibition of BCKDHA-mediated mitochondrial metabolic function.

A drug known as BIX that is effective against bladder and breast cancers may also be effective in fighting non-small cell lung cancer (NSCLC). Although advances have been made in treatment of NSCLC, one of the most effective drugs targets a protein called EGFR, and EGFR gene mutations that lead to acquired drug resistance are common. Jaekyoung Son at the University of Ulsan, Seoul, South Korea, and colleagues investigated whether BIX is effective against NSCLC and attempted to elucidate its mechanism of action. The researchers found that BIX caused death of NSCLC cells, especially those with mutations in the EGFR gene. Further investigation showed that BIX was effective even against drug-resistant NSCLC cells, by acting via a different metabolic pathway. BIX shows promise as an alternative therapy for lung cancer, to overcome drug resistance.

Epigenetic Regulation of Immunotherapy Response in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is defined by the absence of estrogen receptor and progesterone receptor and human epidermal growth factor receptor 2 (HER2) overexpression. This malignancy, representing 15-20% of breast cancers, is a clinical challenge due to the lack of targeted treatments, higher intrinsic aggressiveness, and worse outcomes than other breast cancer subtypes. Immune checkpoint inhibitors have shown promising efficacy for early-stage and advanced TNBC, but this seems limited to a subgroup of patients. Understanding the underlying mechanisms that determine immunotherapy efficiency is essential to identifying which TNBC patients will respond to immunotherapy-based treatments and help to develop new therapeutic strategies. Emerging evidence supports that epigenetic alterations, including aberrant chromatin architecture conformation and the modulation of gene regulatory elements, are critical mechanisms for immune escape. These alterations are particularly interesting since they can be reverted through the inhibition of epigenetic regulators. For that reason, several recent studies suggest that the combination of epigenetic drugs and immunotherapeutic agents can boost anticancer immune responses. In this review, we focused on the contribution of epigenetics to the crosstalk between immune and cancer cells, its relevance on immunotherapy response in TNBC, and the potential benefits of combined treatments.

Human Aspartyl (Asparaginyl) Hydroxylase. A Multifaceted Enzyme with Broad Intra- and Extracellular Activity

Human aspartyl (asparaginyl) β-hydroxylase (HAAH), a unique iron and 2-oxoglutarate dependent oxygenase, has shown increased importance as a suspected oncogenic protein. HAAH and its associated mRNA are upregulated in a wide variety of cancer types, however, the current role of HAAH in the malignant transformation of cells is unknown. HAAH is suspected to play an important role in NOTCH signaling via selective hydroxylation of aspartic acid and asparagine residues of epidermal growth factor (EGF)-like domains. HAAH hydroxylation also potentially mediates calcium signaling and oxygen sensing. In this review we summarize the current state of understanding of the biochemistry and chemical biology of this enzyme, identify key differences from other family members, outline its broader intra- and extracellular roles, and identify the most promising areas for future research efforts.

Histone lysine demethylases and their functions in cancer

Histone lysine demethylases (KDMs) are enzymes that remove the methylation marks on lysines in nucleosomes' histone tails. These changes in methylation marks regulate gene transcription during both development and malignant transformation. Depending on which lysine residue is targeted, the effect of a given KDM on gene transcription can be either activating or repressing, and KDMs can regulate the expression of both oncogenes and tumour suppressors. Thus, the functions of KDMs can be regarded as both oncogenic and tumour suppressive, contingent on cell context and the enzyme isoform. Finally, KDMs also demethylate nonhistone proteins and have a variety of demethylase-independent functions. These epigenetic and other mechanisms that KDMs control make them important regulators of malignant tumours. Here, we present an overview of eight KDM subfamilies, their most-studied lysine targets and selected recent data on their roles in cancer stem cells, tumour aggressiveness and drug tolerance.

Flipside of the Coin: Iron Deficiency and Colorectal Cancer

Iron deficiency, with or without anemia, is the most frequent hematological manifestation in individuals with cancer, and is especially common in patients with colorectal cancer. Iron is a vital micronutrient that plays an essential role in many biological functions, in the context of which it has been found to be intimately linked to cancer biology. To date, however, whereas a large number of studies have comprehensively investigated and reviewed the effects of excess iron on cancer initiation and progression, potential interrelations of iron deficiency with cancer have been largely neglected and are not well-defined. Emerging evidence indicates that reduced iron intake and low systemic iron levels are associated with the pathogenesis of colorectal cancer, suggesting that optimal iron intake must be carefully balanced to avoid both iron deficiency and iron excess. Since iron is vital in the maintenance of immunological functions, insufficient iron availability may enhance oncogenicity by impairing immunosurveillance for neoplastic changes and potentially altering the tumor immune microenvironment. Data from clinical studies support these concepts, showing that iron deficiency is associated with inferior outcomes and reduced response to therapy in patients with colorectal cancer. Here, we elucidate cancer-related effects of iron deficiency, examine preclinical and clinical evidence of its role in tumorigenesis, cancer progression and treatment response. and highlight the importance of adequate iron supplementation to limit these outcomes.

KDM6B (JMJD3) and its dual role in cancer

Epigenetic modifications play a fundamental role in the regulation of gene expression and cell fate. During the development of cancer, epigenetic modifications appear that favor cell proliferation and migration, but at the same time prevent differentiation and apoptosis, among other processes. KDM6B is a histone demethylase that specifically removes methyl groups from H3K27me3, thus allowing re-expression of its target genes. It is currently known that KDM6B can act as both a tumor suppressor and an oncogene depending on the cellular context. Therefore, in this work we summarize the current knowledge of the role that KDM6B plays in different oncological contexts, and we try to orient it towards its clinical application.

Human Papillomavirus 16 (HPV16) E2 Repression of TWIST1 Transcription Is a Potential Mediator of HPV16 Cancer Outcomes

HPV16-positive cancers have a better clinical outcome that their non-HPV anatomical counterparts. Furthermore, the presence of HPV16 E2 RNA predicts a better outcome for HPV16-positive tumors; the reasons for this are not known.

Human papillomaviruses (HPVs) are causative agents in around 5% of all cancers, including cervical and oropharyngeal. A feature of HPV cancers is their better clinical outcome compared with non-HPV anatomical counterparts. In turn, the presence of E2 predicts a better clinical outcome in HPV-positive cancers; the reason(s) for the better outcome of E2-positive patients is not fully understood. Previously, we demonstrated that HPV16 E2 regulates host gene transcription that is relevant to the HPV16 life cycle in N/Tert-1 cells. One of the genes repressed by E2 and the entire HPV16 genome in N/Tert-1 cells is TWIST1. Here, we demonstrate that TWIST1 RNA levels are reduced in HPV-positive versus HPV-negative head and neck cancer and that E2 and HPV16 downregulate both TWIST1 RNA and protein in our N/Tert-1 model; E6/E7 cannot repress TWIST1. E2 represses the TWIST1 promoter in transient assays and is localized to the TWIST1 promoter; E2 also induces repressive epigenetic changes on the TWIST1 promoter. TWIST1 is a master transcriptional regulator of the epithelial to mesenchymal transition (EMT), and a high level of TWIST1 is a prognostic marker indicative of poor cancer outcomes. We demonstrate that TWIST1 target genes are also downregulated in E2-positive N/Tert-1 cells and that E2 promotes a failure in wound healing, a phenotype of low TWIST1 levels. We propose that the presence of E2 in HPV-positive tumors leads to TWIST1 repression and that this plays a role in the better clinical response of E2-positive HPV tumors.

IMPORTANCE HPV16-positive cancers have a better clinical outcome that their non-HPV anatomical counterparts. Furthermore, the presence of HPV16 E2 RNA predicts a better outcome for HPV16-positive tumors; the reasons for this are not known. Here, we demonstrate that E2 represses expression of the TWIST1 gene; an elevated level of this gene is a marker of poor prognosis for a variety of cancers. We demonstrate that E2 directly binds to the TWIST1 promoter and actively represses transcription. TWIST1 is a master regulator promoting EMT, and here, we demonstrate that the presence of E2 reduces the ability of N/Tert-1 cells to wound heal. Overall, we propose that the E2 repression of TWIST1 may contribute to the better clinical outcome of E2-positive HPV16-positive tumors.

The Histone Demethylase KDM3B Promotes Osteo-/Odontogenic Differentiation, Cell Proliferation, and Migration Potential of Stem Cells from the Apical Papilla

Understanding the regulation mechanisms of mesenchymal stem cells (MSCs) can assist in tissue regeneration. The histone demethylase (KDM) family has a crucial role in differentiation and cell proliferation of MSCs, while the function of KDM3B in MSCs is not well understood. In this study, we used the stem cells from the apical papilla (SCAPs) to test whether KDM3B could regulate the function of MSCs. By an alkaline phosphatase (ALP) activity assay, Alizarin red staining, real-time RT-PCR, and western blot analysis, we found that KDM3B enhanced the ALP activity and mineralization of SCAPs and promoted the expression of runt-related transcription factor 2 (RUNX2), osterix (OSX), dentin sialophosphoprotein (DSPP), and osteocalcin (OCN). Additionally, the CFSE, CCK-8, and flow cytometry assays revealed that KDM3B improved cell proliferation by accelerating cell cycle transition from the G1 to S phase. Scratch and transwell migration assays displayed that KDM3B promoted the migration potential of SCAPs. Mechanically, microarray results displayed that 98 genes were upregulated, including STAT1, CCND1, and FGF5, and 48 genes were downregulated after KDM3B overexpression. Besides, we found that the Toll-like receptor and JAK-STAT signaling pathway may be involved in the regulating function of KDM3B in SCAPs. In brief, we discovered that KDM3B promoted the osteo-/odontogenic differentiation, cell proliferation, and migration potential of SCAPs and provided a novel target and theoretical basis for regenerative medicine.

Oncometabolites and the response to radiotherapy

Radiotherapy (RT) is applied in 45-60% of all cancer patients either alone or in multimodal therapy concepts comprising surgery, RT and chemotherapy. However, despite technical innovations approximately only 50% are cured, highlight a high medical need for innovation in RT practice. RT is a multidisciplinary treatment involving medicine and physics, but has always been successful in integrating emerging novel concepts from cancer and radiation biology for improving therapy outcome. Currently, substantial improvements are expected from integration of precision medicine approaches into RT concepts.Altered metabolism is an important feature of cancer cells and a driving force for malignant progression. Proper metabolic processes are essential to maintain and drive all energy-demanding cellular processes, e.g. repair of DNA double-strand breaks (DSBs). Consequently, metabolic bottlenecks might allow therapeutic intervention in cancer patients.Increasing evidence now indicates that oncogenic activation of metabolic enzymes, oncogenic activities of mutated metabolic enzymes, or adverse conditions in the tumor microenvironment can result in abnormal production of metabolites promoting cancer progression, e.g. 2-hyroxyglutarate (2-HG), succinate and fumarate, respectively. Interestingly, these so-called "oncometabolites" not only modulate cell signaling but also impact the response of cancer cells to chemotherapy and RT, presumably by epigenetic modulation of DNA repair.Here we aimed to introduce the biological basis of oncometabolite production and of their actions on epigenetic regulation of DNA repair. Furthermore, the review will highlight innovative therapeutic opportunities arising from the interaction of oncometabolites with DNA repair regulation for specifically enhancing the therapeutic effects of genotoxic treatments including RT in cancer patients.

KDM2B promotes IL-6 production and inflammatory responses through Brg1-mediated chromatin remodeling

IL-6 plays important and pleiotropic roles in infection and inflammatory diseases, and its production needs to be tightly regulated. However, the epigenetic mechanism underlying Il6 gene transcription remains to be fully elucidated. Here, we report that lysine-specific demethylase 2b (KDM2B), which demethylates H3K4me3 and H3K36me2, is required in macrophages and dendritic cells for the induction of IL-6 but not TNF-α, IL-1, and IFN-β. Compared to wild-type mice, KDM2B-deficient mice were more resistant to endotoxin shock and colitis, with a less severe inflammatory pathogenesis phenotype and decreased IL-6 production in sera. KDM2B selectively bound the Il6 promoter but did not alter histone demethylation; instead, KDM2B interacted with Brahma-related gene 1 (Brg1), the core ATPase subunit of SWI/SNF chromatin remodeling complexes, to facilitate chromatin accessibility of the Il6 promoter. Furthermore, KDM2B directly recruited RNA Polymerase II to further initiate and promote Il6 transcription. Thus, our finding identifies a novel nonclassical function of KDM2B in gene-specific transcription initiation and enhancement of Il6 independent of its demethylase activity and adds new insight into the specific epigenetic modification mechanism of inflammatory immune responses.

Therapeutic Potentials of Inhibition of Jumonji C Domain-containing Demethylases in Acute Myeloid Leukemia

Objective:

Acute myeloid leukemia (AML) is a complex disease affected by both genetic and epigenetic factors. Histone methylation and demethylation are types of epigenetic modification in chromatin remodeling and gene expression. Abnormal expression of histone demethylases is indicated in many types of cancer including AML. Although many commercial drugs are available to treat AML, an absolute cure has not been discovered yet. However, inhibition of demethylases could be a potential cure for AML. Methylstat is a chemical agent that inhibits the Jumonji C domain-containing demethylases.

Materials and Methods:

The cytotoxic and apoptotic effects of methylstat and doxorubicin on HL-60 cells were detected by MTT cell viability assay, double staining of treated cells with annexin-V/propidium iodide, and caspase-3 activity assay. Mitochondrial activity was analyzed using JC-1 dye. The expression levels of the BCL2 and BCL2L1 anti-apoptotic genes in HL-60 cells were determined using real-time polymerase chain reaction (PCR). Lastly, the cytostatic effect was determined by cell cycle analysis.

Results:

In our research, cytotoxic, cytostatic, and apoptotic effects of methylstat on human HL-60 cells were investigated. Cytotoxic and cytostatic analyses revealed that methylstat decreased cell proliferation in a dose-dependent cytotoxic manner and arrested HL-60 cells in the G2/M and S phases. Methylstat also induced apoptosis through the loss of mitochondrial membrane potential and increases in caspase-3 enzyme activity. The expression levels of BCL2 and BCL2L1 were also decreased according to real-time PCR results. Finally, the combination of methylstat with doxorubicin resulted in synergistic cytotoxic effects on HL-60 cells.

Conclusion:

Taken together, these results demonstrate that methylstat may be a powerful candidate as a drug component of AML treatment protocols.

Targeted Downregulation of kdm4a Ameliorates Tau-engendered Defects in Drosophila melanogaster

BACKGROUND

Tauopathies, a class of neurodegenerative diseases that includes Alzheimer's disease (AD), are characterized by the deposition of neurofibrillary tangles composed of hyperphosphorylated tau protein in the human brain. As abnormal alterations in histone acetylation and methylation show a cause and effect relationship with AD, we investigated the role of several Jumonji domain-containing histone demethylase (JHDM) genes, which have yet to be studied in AD pathology.

METHODS

To examine alterations of several JHDM genes in AD pathology, we performed bioinformatics analyses of JHDM gene expression profiles in brain tissue samples from deceased AD patients. Furthermore, to investigate the possible relationship between alterations in JHDM gene expression profiles and AD pathology in vivo, we examined whether tissue-specific downregulation of JHDM Drosophila homologs (kdm) can affect tau^R406W-induced neurotoxicity using transgenic flies containing the UAS-Gal4 binary system.

RESULTS

The expression levels of JHDM1A, JHDM2A/2B, and JHDM3A/3B were significantly higher in postmortem brain tissue from patients with AD than from non-demented controls, whereas JHDM1B mRNA levels were downregulated in the brains of patients with AD. Using transgenic flies, we revealed that knockdown of kdm2 (homolog to human JHDM1), kdm3 (homolog to human JHDM2), kdm4a (homolog to human JHDM3A), or kdm4b (homolog to human JHDM3B) genes in the eye ameliorated the tau^R406W-engendered defects, resulting in less severe phenotypes. However, kdm4a knockdown in the central nervous system uniquely ameliorated tau^R406W-induced locomotion defects by restoring heterochromatin.

CONCLUSION

Our results suggest that downregulation of kdm4a expression may be a potential therapeutic target in AD.

Epigenetic Regulation of Adipogenic Differentiation by Histone Lysine Demethylation

Obesity is a rising public health problem that contributes to the development of several metabolic diseases and cancer. Adipocyte precursors outside of adipose depots that expand due to overweight and obesity may have a negative impact on human health. Determining how progenitor cells acquire a preadipocyte commitment and become mature adipocytes remains a significant challenge. Over the past several years, we have learned that the establishment of cellular identity is widely influenced by changes in histone marks, which in turn modulate chromatin structure. In this regard, histone lysine demethylases (KDMs) are now emerging as key players that shape chromatin through their ability to demethylate almost all major histone methylation sites. Recent research has shown that KDMs orchestrate the chromatin landscape, which mediates the activation of adipocyte-specific genes. In addition, KDMs have functions in addition to their enzymatic activity, which are beginning to be revealed, and their dysregulation seems to be related to the development of metabolic disorders. In this review, we highlight the biological functions of KDMs that contribute to the establishment of a permissive or repressive chromatin environment during the mesenchymal stem cell transition into adipocytes. Understanding how KDMs regulate adipogenesis might prompt the development of new strategies for fighting obesity-related diseases.

Fumarate hydratase in cancer: A multifaceted tumour suppressor

Cancer is now considered a multifactorial disorder with different aetiologies and outcomes. Yet, all cancers share some common molecular features. Among these, the reprogramming of cellular metabolism has emerged as a key player in tumour initiation and progression. The finding that metabolic enzymes such as fumarate hydratase (FH), succinate dehydrogenase (SDH) and isocitrate dehydrogenase (IDH), when mutated, cause cancer suggested that metabolic dysregulation is not only a consequence of oncogenic transformation but that it can act as cancer driver. However, the mechanisms underpinning the link between metabolic dysregulation and cancer remain only partially understood. In this review we discuss the role of FH loss in tumorigenesis, focusing on the role of fumarate as a key activator of a variety of oncogenic cascades. We also discuss how these alterations are integrated and converge towards common biological processes. This review highlights the complexity of the signals elicited by FH loss, describes that fumarate can act as a bona fide oncogenic event, and provides a compelling hypothesis of the stepwise neoplastic progression after FH loss.

The Role of DNA/Histone Modifying Enzymes and Chromatin Remodeling Complexes in Testicular Germ Cell Tumors

It is well established that cancer cells exhibit alterations in chromatin structure and accessibility. Indeed, the dysregulation of many protein-coding players with enzymatic activity (DNA and histone-modifying enzymes) and chromatin remodelers have been depicted in various tumor models in recent years. Still, little attention has been directed towards testicular germ cell tumors (TGCTs)-representing the most common neoplasm among young adult Caucasian men-with most studies focusing on exploring the role of DNA methyltransferases (DNMTs) and DNA demethylases (TETs). TGCTs represent a complex tumor model, associated with developmental and embryogenesis-related phenomena, and display seldom (cyto)genetic aberrations, leaving room for Epigenetics to explain such morphological and clinical diversity. Herein, we have summarized the major findings that were reported in literature regarding the dysregulation of DNA/histone-modifying enzymes and chromatin remodelers in TGCTs. Additionally, we performed in silico analysis of The Cancer Genome Atlas database to find the most relevant of those players in TGCTs. We concluded that several DNA/histone-modifying enzymes and chromatin remodelers may serve as biomarkers for subtyping, dictating prognosis and survival, and, possibly, for serving as targets of directed, less toxic therapies.

α-Amine Desaturation of d-Arginine by the Iron(II)- and 2-(Oxo)glutarate-Dependent l-Arginine 3-Hydroxylase, VioC

When challenged with substrate analogues, iron(II)- and 2-(oxo)glutarate-dependent (Fe/2OG) oxygenases can promote transformations different from those they enact upon their native substrates. We show here that the Fe/2OG enzyme, VioC, which is natively an l-arginine 3-hydroxylase, catalyzes an efficient oxidative deamination of its substrate enantiomer, d-Arg. The reactant complex with d-Arg retains all interactions between enzyme and substrate functional groups, but the required structural adjustments and opposite configuration of C2 position this carbon more optimally than C3 to donate hydrogen (H^•) to the ferryl intermediate. The simplest possible mechanism, C2 hydroxylation followed by elimination of ammonia, is inconsistent with the demonstrated solvent origin of the ketone oxygen in the product. Rather, the reaction proceeds via a hydrolytically labile C2-iminium intermediate, demonstrated by its reductive trapping in solution with NaB²H₄ to produce racemic [²H]Arg. Of two alternative pathways to the iminium species, C2 hydroxylation followed by dehydration versus direct desaturation, the latter possibility appears to be more likely, because the former mechanism would be expected to result in detectable incorporation of ¹⁸O from ¹⁸O₂. The direct desaturation of a C-N bond implied by this analysis is analogous to that recently posited for the reaction of the l-Arg 4,5-desaturase, NapI, thus lending credence to the prior mechanistic proposal. Such a pathway could also potentially be operant in a subset of reactions catalyzed by Fe/2OG N-demethylases, which have instead been purported to enact C-N bond cleavage by methyl hydroxylation and elimination of formaldehyde.

Hairless regulates p53 target genes to exert tumor suppressive functions in glioblastoma

Glioblastoma (GBM) is the most common malignant brain tumor and is associated with a poor prognosis, with most patients living less than a year after diagnosis. Given that GBM nearly always recurs after conventional treatments, there is an urgent need to identify novel molecular targets. Hairless (HR) is a nuclear factor enriched in the skin and has been previously implicated in hair cycling. HR is also highly expressed in the brain, but its significance is unknown. We found that human hairless gene (HR) expression is significantly decreased in all GBM subtypes compared with normal brain tissue and is predictive of prognosis, which suggests that loss of HR expression can contribute to GBM pathogenesis. HR was recently discovered to bind to and regulate p53 responsive elements, and thus we hypothesized that HR may have a tumor suppressive function in GBM by modulating p53 target gene expression. We found that HR indeed regulates p53 target genes, including those implicated in cell cycle progression and apoptosis in the GBM-derived U87 cell line, and restoring HR expression triggered G2/M arrest and apoptosis. An analysis of sequenced genomes from patients with GBM revealed 10 HR somatic mutations in patients with glioma, two of which are located in the histone demethylase domain of HR. These two mutations, P996S and K1004N, were reconstructed and found to have impaired p53 transactivating properties. Collectively, the results of our study suggest that HR has tumor suppressive functions in GBM, which may be clinically relevant and a potential avenue for therapeutic intervention.

The Jumonji-domain histone demethylase inhibitor JIB-04 deregulates oncogenic programs and increases DNA damage in Ewing Sarcoma, resulting in impaired cell proliferation and survival, and reduced tumor growth

Ewing Sarcoma is an aggressive malignant neoplasm affecting children and young adults. Ewing Sarcoma is driven by transcription factor fusion oncoproteins, most commonly EWS/Fli1. While some patients can be cured with high-dose, multi-agent, chemotherapy, those that cannot currently have few options. Targeting of the driver oncofusion remains a logical therapeutic approach, but has proven difficult. Recent work has pointed to epigenetic mechanisms as key players, and potential new therapeutic targets, in Ewing Sarcoma. In this study we examined the activity of the pan-JHDM pharmacologic inhibitor JIB-04 in this disease. We show that JIB-04 potently inhibits the growth and viability of Ewing Sarcoma cells, and also impairs tumor xenograft growth. Effects on histone methylation at growth-inhibitory doses vary among cell lines, with most cell lines exhibiting increased total H3K27me3 levels, and some increased H3K4me3 and H3K9me3. JIB-04 treatment widely alters expression of oncogenic and tumor suppressive pathways, including downregulation of known oncogenic members of the Homeobox B and D clusters. JIB-04 also disrupts the EWS/Fli1 expression signature, including downregulation of pro-proliferative pathways normally under positive oncofusion control. Interestingly, these changes are accompanied by increased levels of the EWS/Fli1 oncofusion, suggesting that the drug could be uncoupling EWS/Fli1 from its oncogenic program. All Ewing Sarcoma cell lines examined also manifest increased DNA damage upon JIB-04 treatment. Together, the findings suggest that JIB-04 acts via multiple mechanisms to compromise Ewing Sarcoma cell growth and viability.

The Methylation Status of the Epigenome: Its Emerging Role in the Regulation of Tumor Angiogenesis and Tumor Growth, and Potential for Drug Targeting

Approximately 50 years ago, Judah Folkman raised the concept of inhibiting tumor angiogenesis for treating solid tumors. The development of anti-angiogenic drugs would decrease or even arrest tumor growth by restricting the delivery of oxygen and nutrient supplies, while at the same time display minimal toxic side effects to healthy tissues. Bevacizumab (Avastin)—a humanized monoclonal anti VEGF-A antibody—is now used as anti-angiogenic drug in several forms of cancers, yet with variable results. Recent years brought significant progresses in our understanding of the role of chromatin remodeling and epigenetic mechanisms in the regulation of angiogenesis and tumorigenesis. Many inhibitors of DNA methylation as well as of histone methylation, have been successfully tested in preclinical studies and some are currently undergoing evaluation in phase I, II or III clinical trials, either as cytostatic molecules—reducing the proliferation of cancerous cells—or as tumor angiogenesis inhibitors. In this review, we will focus on the methylation status of the vascular epigenome, based on the genomic DNA methylation patterns with DNA methylation being mainly transcriptionally repressive, and lysine/arginine histone post-translational modifications which either promote or repress the chromatin transcriptional state. Finally, we discuss the potential use of “epidrugs” in efficient control of tumor growth and tumor angiogenesis.

The PHD Transcription Factor Rum1 Regulates Morphogenesis and Aflatoxin Biosynthesis in Aspergillus flavus

Aspergillus flavus produces mycotoxins especially aflatoxin B₁ and infects crops worldwide. As a PHD transcription factor, there is no report on the role of Rum1 in the virulence of Aspergillus spp. yet. This study explored the biological function of Rum1 in A. flavus through the construction of rum1 deletion mutants and rum1 complementation strains with the method of homologous recombination. It was found, in the study, that Rum1 negatively regulates conidiation through abaA and brlA, positively regulates sclerotia formation through nsdC, nsdD, and sclR, triggers aflatoxin biological synthesis, and enhances the activity of amylase. Our findings suggested that Rum1 plays a major role in the growth of mycelia, conidia, and sclerotia production along with aflatoxin biosynthesis in A. flavus.

Cancer-associated 2-oxoglutarate analogues modify histone methylation by inhibiting histone lysine demethylases

Histone lysine demethylases (KDMs) are 2-oxoglutarate-dependent dioxygenases (2-OGDDs) that regulate gene expression by altering chromatin structure. Their dysregulation has been associated with many cancers. We set out to study the catalytic and inhibitory properties of human KDM4A, KDM4B, KDM5B, KDM6A and KDM6B, aiming in particular to reveal which of these enzymes are targeted by cancer-associated 2-oxoglutarate (2-OG) analogues. We used affinity-purified insect cell-produced enzymes and synthetic peptides with trimethylated lysines as substrates for the in vitro enzyme activity assays. In addition, we treated breast cancer cell lines with cell-permeable forms of 2-OG analogues and studied their effects on the global histone methylation state. Our data show that KDMs have substrate specificity. Among the enzymes studied, KDM5B had the highest affinity for the peptide substrate but the lowest affinity for the 2-OG and the Fe²⁺ cosubstrate/cofactors. R-2-hydroxyglutarate (R-2HG) was the most efficient inhibitor of KDM6A, KDM4A and KDM4B, followed by S-2HG. This finding was supported by accumulations of the histone H3K9me3 and H3K27me3 marks in cells treated with the cell-permeable forms of these compounds. KDM5B was especially resistant to inhibition by R-2HG, while citrate was the most efficient inhibitor of KDM6B. We conclude that KDM catalytic activity is susceptible to inhibition by tumorigenic 2-OG analogues and suggest that the inhibition of KDMs is involved in the disease mechanism of cancers in which these compounds accumulate, such as the isocitrate dehydrogenase mutations.

KDM5B demethylates H3K4 to recruit XRCC1 and promote chemoresistance

Chemotherapy is the main treatment for human cancers including gastric cancer. However, in response to chemotherapeutic drugs, tumor cells can develop drug resistance by reprogramming intracellular metabolic and epigenetic networks to maintain their intrinsic homeostasis. Previously, we have established cisplatin-resistant gastric cancer cells as a drug resistant model, and elucidated the XRCC1 as the core DNA repair mechanism of drug resistance. This study investigated the regulation of XRCC1 by lysine demethylase 5B (KDM5B) in drug resistance. We found that the methylation level of H3K4 decreased significantly in drug-resistant cells. The chemical inhibitor of H3K4 demethylases, JIB-04, restored the methylation of H3K4 and blocked the co-localization of XRCC1 and γH2AX, eventually improved drug sensitivity. We further found that the expression level of KDM5B increased significantly in drug-resistant cells. Knockdown of KDM5B increased the methylation level of H3K4 and blocked the localization of XRCC1 to the DNA damage site, leads to increased drug sensitivity. In the sensitive cells, overexpression of KDM5B suppressed H3K4 methylation levels, which resulted to resistance to cisplatin. Moreover, we found that the posttranslational modification of KDM5B is responsible for its high expression in drug-resistant cells. Through mass spectrometry screening and co-immunoprecipitation validation, we found that the molecular chaperone HSP90 forms a complex with KDM5B in drug resistance cells. Interestingly, HSP90 inhibitor 17-AAG induced KDM5B degradation in a time-and-dose-dependent manner, indicating that HSP90 protected KDM5B from protein degradation. Targeting inhibition of HSP90 and KDM5B reversed drug resistance both in vitro and in vivo. Taken together, molecular chaperon HSP90 interacted with KDM5B to protect it from ubiquitin-dependent proteasomal degradation. Increased KDM5B demethylated H3K4 and facilitated the recruitment of XRCC1 to repair damaged DNA. Therefore, inhibition of HSP90 or KDM5B represented a novel approach to reverse chemoresistance in human cancers.

Lung Cancer Therapy Targeting Histone Methylation: Opportunities and Challenges

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

APIM-peptide targeting PCNA improves the efficacy of docetaxel treatment in the TRAMP mouse model of prostate cancer

Docetaxel is the chemotherapeutic choice for metastatic hormone-refractory prostate cancer, however, it only marginally improves the survival rate. The purpose of the present study was to examine if a peptide targeting the cellular scaffold protein PCNA could improve docetaxel's efficacy. We found that docetaxel given in combination with a cell penetrating peptide containing the AlkB homolog 2 PCNA interacting motif (APIM-peptide), reduced the prostate volume and limited prostate cancer regrowth in vivo in the immunocompetent transgenic adenocarcinoma model of prostate cancer (TRAMP). In accordance with this, we found that the APIM-peptide enhanced the efficacy of docetaxel in vitro. Gene expression analysis on prostate cancer cell lines indicated that the combination of docetaxel and APIM-peptide alters expression of genes involved in cellular signaling, apoptosis, and prostate cancer development. These changes were not detected in single agent treated cells. Our results suggest that targeting PCNA and thereby affecting multiple cellular pathways simultaneously has the potential to improve docetaxel therapy of advanced prostate cancer.

Statin and Bisphosphonate Induce Starvation in Fast-Growing Cancer Cell Lines

Statins and bisphosphonates are increasingly recognized as anti-cancer drugs, especially because of their cholesterol-lowering properties. However, these drugs act differently on various types of cancers. Thus, the aim of this study was to compare the effects of statins and bisphosphonates on the metabolism (NADP⁺/NADPH-relation) of highly proliferative tumor cell lines from different origins (PC-3 prostate carcinoma, MDA-MB-231 breast cancer, U-2 OS osteosarcoma) versus cells with a slower proliferation rate like MG-63 osteosarcoma cells. Global gene expression analysis revealed that after 6 days of treatment with pharmacologic doses of the statin simvastatin and of the bisphosphonate ibandronate, simvastatin regulated more than twice as many genes as ibandronate, including many genes associated with cell cycle progression. Upregulation of starvation-markers and a reduction of metabolism and associated NADPH production, an increase in autophagy, and a concomitant downregulation of H3K27 methylation was most significant in the fast-growing cancer cell lines. This study provides possible explanations for clinical observations indicating a higher sensitivity of rapidly proliferating tumors to statins and bisphosphonates.

Interplay between Metabolism and Epigenetics: A Nuclear Adaptation to Environmental Changes

The physiological identity of every cell is maintained by highly specific transcriptional networks that establish a coherent molecular program that is in tune with nutritional conditions. The regulation of cell-specific transcriptional networks is accomplished by an epigenetic program via chromatin-modifying enzymes, whose activity is directly dependent on metabolites such as acetyl-coenzyme A, S-adenosylmethionine, and NAD+, among others. Therefore, these nuclear activities are directly influenced by the nutritional status of the cell. In addition to nutritional availability, this highly collaborative program between epigenetic dynamics and metabolism is further interconnected with other environmental cues provided by the day-night cycles imposed by circadian rhythms. Herein, we review molecular pathways and their metabolites associated with epigenetic adaptations modulated by histone- and DNA-modifying enzymes and their responsiveness to the environment in the context of health and disease.

Inhibitor of H3K27 demethylase JMJD3/UTX GSK-J4 is a potential therapeutic option for castration resistant prostate cancer

Androgen receptor (AR) mediates initiation and progression of prostate cancer (PCa); AR-driven transcription is activated by binding of androgens to the ligand-binding domain (LBD) of AR. Androgen ablation therapy offers only a temporary relief of locally advanced and metastatic PCa, and the disease eventually recurs as a lethal castration-resistant PCa (CRPC) as there is no effective treatment for CRPC patients. Thus, it is critical to identify novel targeted and combinatorial regimens for clinical management of CRPC. Reduction of the repressive epigenetic modification H3K27me2/3 correlates with PCa aggressiveness, while corresponding demethylases JMJD3/UTX are overexpressed in PCa. We found that JMJD3/UTX inhibitor GSK-J4 reduced more efficiently proliferation of AR-ΔLBD cells (CRPC model) compared with isogenic AR-WT cells. Inhibition of JMJD3/UTX protects demethylation of H3K27Me2/3, thus reducing levels of H3k27Me1. We observed that the reduction dynamics of H3K27Me1 was faster and achieved at lower inhibitor concentrations in AR-ΔLBD cells, suggesting that inhibition of JMJD3/UTX diminished proliferation of these cells by hindering AR-driven transcription. In addition, we observed synergy between GSK-J4 and Cabazitaxel, a taxane derivative that is approved for CRPC treatment. Collectively, our results point at the H3K27 demethylation pathway as a new potential therapeutic target in CRPC patients.

Epigenetics in endometrial carcinogenesis - part 2: histone modifications, chromatin remodeling and noncoding RNAs

Carcinogenesis is a multistep multifactorial process that involves the accumulation of genetic and epigenetic alterations. In the past two decades, there has been an exponential growth of knowledge establishing the importance of epigenetic changes in cancer. Our work focused on reviewing the main role of epigenetics in the pathogenesis of endometrial carcinoma, highlighting the reported results concerning each epigenetic mechanistic layer. In a previous review, we assessed DNA methylation alterations. The present review examines the contribution of histone modifications, chromatin remodeling and noncoding RNA alterations for endometrial carcinogenesis.

Structure-function relationships of human JmjC oxygenases-demethylases versus hydroxylases

The Jumonji-C (JmjC) subfamily of 2-oxoglutarate (2OG)-dependent oxygenases are of biomedical interest because of their roles in the regulation of gene expression and protein biosynthesis. Human JmjC 2OG oxygenases catalyze oxidative modifications to give either chemically stable alcohol products, or in the case of Nɛ-methyl lysine demethylation, relatively unstable hemiaminals that fragment to give formaldehyde and the demethylated product. Recent work has yielded conflicting reports as to whether some JmjC oxygenases catalyze N-methyl group demethylation or hydroxylation reactions. We review JmjC oxygenase-catalyzed reactions within the context of structural knowledge, highlighting key differences between hydroxylases and demethylases, which have the potential to inform on the possible type(s) of reactions catalyzed by partially characterized or un-characterized JmjC oxygenases in humans and other organisms.

KDM4C Activity Modulates Cell Proliferation and Chromosome Segregation in Triple-Negative Breast Cancer

The Jumonji-containing domain protein, KDM4C, is a histone demethylase associated with the development of several forms of human cancer. However, its specific function in the viability of tumoral lineages is yet to be determined. This work investigates the importance of KDM4C activity in cell proliferation and chromosome segregation of three triple-negative breast cancer cell lines using a specific demethylase inhibitor. Immunofluorescence assays show that KDM4C is recruited to mitotic chromosomes and that the modulation of its activity increases the number of mitotic segregation errors. However, 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) cell proliferation assays demonstrate that the demethylase activity is required for cell viability. These results suggest that the histone demethylase activity of KDM4C is essential for breast cancer progression given its role in the maintenance of chromosomal stability and cell growth, thus highlighting it as a potential therapeutic target.