To clarify the role of HDACs in erythropoiesis, expression, activity and function of class I (HDAC1, HDAC2, HDAC3) and class IIa (HDAC4, HDAC5) HDACs during in vitro maturation of human erythroblasts were compared. During erythroid maturation, expression of HDAC1, HDAC2 and HDAC3 remained constant and activity and GATA1 association (its partner of the NuRD complex), of HDAC1 increased. By contrast, HDAC4 content drastically decreased and HDAC5 remained constant in content but decreased in activity. In erythroid cells, pull down experiments identified the presence of a novel complex formed by HDAC5, GATA1, EKLF and pERK which was instead undetectable in cells of the megakaryocytic lineage. With erythroid maturation, association among HDAC5, GATA1 and EKLF persisted but levels of pERK sharply decreased. Treatment of erythroleukemic cells with inhibitors of ERK phosphorylation reduced by >90% the total and nuclear content of HDAC5, GATA1 and EKLF, suggesting that ERK phosphorylation is required for the formation of this complex. Based on the function of class IIa HDACs as chaperones of other proteins to the nucleus and the erythroid-specificity of HDAC5 localization, this novel HDAC complex was named nuclear remodeling shuttle erythroid (NuRSERY). Exposure of erythroid cells to the class II-selective HDAC inhibitor (HDACi) APHA9 increased γ/(γ+β) globin expression ratios (Mai et al., 2007), suggesting that NuRSERY may regulate globin gene expression. In agreement with this hypothesis, exposure of erythroid cells to APHA9 greatly reduced the association among HDAC5, GATA1 and EKLF. Since exposure to APHA9 did not affect survival rates or p21 activation, NuRSERY may represent a novel, possibly less toxic, target for epigenetic therapies of hemoglobinopaties and other disorders.
Histone deacetylases; GATA1; EKLF; Erythropoiesis; Hemoglobin; Histone deacetylase inhibitors
We designed and synthesized two novel nitrobenzoxadiazole (NBD) analogues of the
anticancer agent 6-((7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)thio)hexan-1-ol
(NBDHEX). The new compounds, namely MC3165 and MC3181, bear one and two oxygen
atoms within the hydroxy-containing alkyl chain at the C4 position of the NBD
scaffold, respectively. This insertion did not alter the chemical reactivity
with reduced glutathione, while it conferred a remarkable increase in water
solubility. MC3181 was more selective than NBDHEX towards the target protein,
glutathione transferase P1-1, and highly effective in vitro
against a panel of human melanoma cell lines, with IC50 in the
submicromolar-low micromolar range. Interestingly, the cellular response to
MC3181 was cell-type-specific; the compound triggered a JNK-dependent apoptosis
in the BRAF-V600E-mutated A375 cells, while it induced morphological changes
together with an increase in melanogenesis in BRAF wild-type SK23-MEL cells.
MC3181 exhibited a remarkable therapeutic activity against BRAF-V600E-mutant
xenografts, both after intravenous and oral administration. Outstandingly, no
treatment-related signs of toxicity were observed both in healthy and
tumor-bearing mice after single and repeated administrations.
Taken together, these results indicate that MC3181 may represent a potential
novel therapeutic opportunity for BRAF-mutated human melanoma, while being safe
and water-soluble and thus overcoming all the critical aspects of NBDHEX
Glutathione Transferase P1-1; c-Jun N-terminal Kinase; 6-((7-nitrobenzo[c][1,2,5]oxadiazoles; Human Melanoma Xenografts
methyltransferases (DNMTs) are important enzymes involved in
epigenetic control of gene expression and represent valuable targets
in cancer chemotherapy. A number of nucleoside DNMT inhibitors (DNMTi)
have been studied in cancer, including in cancer stem cells, and two
of them (azacytidine and decitabine) have been approved for treatment
of myelodysplastic syndromes. However, only a few non-nucleoside DNMTi
have been identified so far, and even fewer have been validated in
cancer. Through a process of hit-to-lead optimization, we report here
the discovery of compound 5 as a potent non-nucleoside
DNMTi that is also selective toward other AdoMet-dependent protein
methyltransferases. Compound 5 was potent at single-digit
micromolar concentrations against a panel of cancer cells and was
less toxic in peripheral blood mononuclear cells than two other compounds
tested. In mouse medulloblastoma stem cells, 5 inhibited
cell growth, whereas related compound 2 showed high cell
differentiation. To the best of our knowledge, 2 and 5 are the first non-nucleoside DNMTi tested in a cancer stem
Background: 4-Aminoquinoline SGI-1027 and analogs inhibit DNA methylation, which is deregulated in cancers.
Results: These compounds induce deviations from Michaelis-Menten equations in DNA competition experiments and interact with DNA.
Conclusion: They are competitive inhibitors for the DNA substrate of the DNA methyltransferase and non-competitive for the methyl group donor, S-adenosyl-l-methionine.
Significance: These findings suggest a mechanism of inhibition for these 4-aminoquinoline-based DNMT inhibitors.
Among the epigenetic marks, DNA methylation is one of the most studied. It is highly deregulated in numerous diseases, including cancer. Indeed, it has been shown that hypermethylation of tumor suppressor genes promoters is a common feature of cancer cells. Because DNA methylation is reversible, the DNA methyltransferases (DNMTs), responsible for this epigenetic mark, are considered promising therapeutic targets. Several molecules have been identified as DNMT inhibitors and, among the non-nucleoside inhibitors, 4-aminoquinoline-based inhibitors, such as SGI-1027 and its analogs, showed potent inhibitory activity. Here we characterized the in vitro mechanism of action of SGI-1027 and two analogs. Enzymatic competition studies with the DNA substrate and the methyl donor cofactor, S-adenosyl-l-methionine (AdoMet), displayed AdoMet non-competitive and DNA competitive behavior. In addition, deviations from the Michaelis-Menten model in DNA competition experiments suggested an interaction with DNA. Thus their ability to interact with DNA was established; although SGI-1027 was a weak DNA ligand, analog 5, the most potent inhibitor, strongly interacted with DNA. Finally, as 5 interacted with DNMT only when the DNA duplex was present, we hypothesize that this class of chemical compounds inhibit DNMTs by interacting with the DNA substrate.
DNA; DNA Methyltransferase; DNA-Protein Interaction; Enzyme Inhibitor; Gene Regulation; SGI-1027; Competition; Inhibition Mechanism
IκB kinase ε (IKK-ε) has an essential role as a regulator of innate immunity, functioning downstream of pattern recognition receptors to modulate NF-κB and interferon (IFN) signaling. In the present study, we investigated IKK-ε activation following T cell receptor (TCR)/CD28 stimulation of primary CD4+ T cells and its role in the stimulation of a type I IFN response. IKK-ε was activated following TCR/CD28 stimulation of primary CD4+ T cells; however, in T cells treated with poly(I·C), TCR/CD28 costimulation blocked induction of IFN-β transcription. We demonstrated that IKK-ε phosphorylated the transcription factor IFN regulatory factor 1 (IRF-1) at amino acid (aa) 215/219/221 in primary CD4+ T cells and blocked its transcriptional activity. At the mechanistic level, IRF-1 phosphorylation impaired the physical interaction between IRF-1 and the NF-κB RelA subunit and interfered with PCAF-mediated acetylation of NF-κB RelA. These results demonstrate that TCR/CD28 stimulation of primary T cells stimulates IKK-ε activation, which in turn contributes to suppression of IFN-β production.
Among neurodegenerative disorders, Alzheimer’s disease (AD) represents the most common cause of dementia in the elderly. Several genetic and environmental factors have been identified; however, aging represents the most important risk factor in the development of AD. To date, no effective treatments to prevent or slow this dementia are available. Sirtuins (SIRTs) are a family of NAD+-dependent enzymes, implicated in the control of a variety of biological processes that have the potential to modulate neurodegeneration. Here we tested the hypothesis that activation of SIRT1 or inhibition of SIRT2 would prevent reactive gliosis which is considered one of the most important hallmark of AD. Primary rat astrocytes were activated with beta amyloid 1-42 (Aβ 1-42) and treated with resveratrol (RSV) or AGK-2, a SIRT1 activator and a SIRT2-selective inhibitor, respectively. Results showed that both RSV and AGK-2 were able to reduce astrocyte activation as well as the production of pro-inflammatory mediators. These data disclose novel findings about the therapeutic potential of SIRT modulators, and suggest novel strategies for AD treatment.
resveratrol; AGK-2; sirtuins; beta-amyloid; astrocyte; reactive gliosis; Alzheimer’s disease
Chemical manipulations performed on the histone H3 lysine 9 methyltransferases (G9a/GLP) inhibitor BIX-01294 afforded novel desmethoxyquinazolines able to inhibit the DNA methyltransferase DNMT3A at low micromolar levels without any significant inhibition of DNMT1 and G9a. In KG-1 cells such compounds, when tested at sub-toxic doses, induced the luciferase re-expression in a stable construct controlled by a cytomegalovirus (CMV) promoter silenced by methylation (CMV-luc assay). Finally, in human lymphoma U-937 and RAJI cells, the N-(1-benzylpiperidin-4-yl)-2-(4-phenylpiperazin-1-yl)quinazolin-4-amine induced the highest proliferation arrest and cell death induction starting from 10 µM, in agreement with its DNMT3A inhibitory potency.
Chromatin modifications are sensitive to environmental and nutritional stimuli. Abnormalities in epigenetic regulation are associated with metabolic disorders such as obesity and diabetes that are often linked with defects in oxidative metabolism. Here, we evaluated the potential of class-specific synthetic inhibitors of histone deacetylases (HDACs), central chromatin-remodeling enzymes, to ameliorate metabolic dysfunction. Cultured myotubes and primary brown adipocytes treated with a class I–specific HDAC inhibitor showed higher expression of Pgc-1α, increased mitochondrial biogenesis, and augmented oxygen consumption. Treatment of obese diabetic mice with a class I– but not a class II–selective HDAC inhibitor enhanced oxidative metabolism in skeletal muscle and adipose tissue and promoted energy expenditure, thus reducing body weight and glucose and insulin levels. These effects can be ascribed to increased Pgc-1α action in skeletal muscle and enhanced PPARγ/PGC-1α signaling in adipose tissue. In vivo ChIP experiments indicated that inhibition of HDAC3 may account for the beneficial effect of the class I–selective HDAC inhibitor. These results suggest that class I HDAC inhibitors may provide a pharmacologic approach to treating type 2 diabetes.
Embryonal Rhabdomyosarcoma (RMS) is a pediatric soft-tissue sarcoma derived from myogenic precursors that is characterized by a good prognosis in patients with localized disease. Conversely, metastatic tumors often relapse, leading to a dismal outcome. The histone methyltransferase EZH2 epigenetically suppresses skeletal muscle differentiation by repressing the transcription of myogenic genes. Moreover, de-regulated EZH2 expression has been extensively implied in human cancers. We have previously shown that EZH2 is aberrantly over-expressed in RMS primary tumors and cell lines. Moreover, it has been recently reported that EZH2 silencing in RD cells, a recurrence-derived embryonal RMS cell line, favors myofiber-like structures formation in a pro-differentiation context. Here we evaluate whether similar effects can be obtained also in the presence of growth factor-supplemented medium (GM), that mimics a pro-proliferative microenvironment, and by pharmacological targeting of EZH2 in RD cells and in RD tumor xenografts.
Embryonal RMS RD cells were cultured in GM and silenced for EZH2 or treated with either the S-adenosylhomocysteine hydrolase inhibitor 3-deazaneplanocin A (DZNep) that induces EZH2 degradation, or with a new class of catalytic EZH2 inhibitors, MC1948 and MC1945, which block the catalytic activity of EZH2. RD cell proliferation and myogenic differentiation were evaluated both in vitro and in vivo.
Here we show that EZH2 protein was abnormally expressed in 19 out of 19 (100%) embryonal RMS primary tumors and cell lines compared to their normal counterparts. Genetic down-regulation of EZH2 by silencing in GM condition reduced RD cell proliferation up-regulating p21Cip1. It also resulted in myogenic-like differentiation testified by the up-regulation of myogenic markers Myogenin, MCK and MHC. These effects were reverted by enforced over-expression of a murine Ezh2, highlighting an EZH2-specific effect. Pharmacological inhibition of EZH2 using either DZNep or MC inhibitors phenocopied the genetic knockdown of EZH2 preventing cell proliferation and restoring myogenic differentiation both in vitro and in vivo.
These results provide evidence that EZH2 function can be counteracted by pharmacological inhibition in embryonal RMS blocking proliferation even in a pro-proliferative context. They also suggest that this approach could be exploited as a differentiation therapy in adjuvant therapeutic intervention for embryonal RMS.
EZH2; Histone methyltransferase; rhabdomyosarcoma; Polycomb proteins; Differentiation; DZnep; EZH2 catalytic inhibitors
Arginine methylation is a common post-translational modification that is crucial in modulating gene expression at multiple critical levels. The arginine methyltransferases (PRMTs) are envisaged as promising druggable targets but their role in physiological and pathological pathways is far from being clear, due to the limited number of modulators reported to date. In this effort, enzyme activators can be invaluable tools useful as gain-of-function reagents to interrogate the biological roles in cells and in vivo of PRMTs. Yet the identification of such molecules is rarely pursued. Herein we describe a series of aryl ureido acetamido indole carboxylates (dubbed “uracandolates”), able to increase the methylation of histone- (H3) or non-histone (polyadenylate-binding protein 1, PABP1) substrates induced by coactivator-associated arginine methyltransferase 1 (CARM1), both in in vitro and cellular settings. To the best of our knowledge, this is the first report of compounds acting as CARM1 activators.
CARM1 activator; PRMT inhibitors; arginine methyltransferase; histone modifying enzyme; epigenetics
Recent statistics indicate that the human population is ageing rapidly. Healthy, but also diseased, elderly people are increasing. This trend is particularly evident in Western countries, where healthier living conditions and better cures are available. To understand the process leading to age-associated alterations is, therefore, of the highest relevance for the development of new treatments for age-associated diseases, such as cancer, diabetes, Alzheimer and cardiovascular accidents. Mechanistically, it is well accepted that the accumulation of intracellular damage determined by reactive oxygen species (ROS) might orchestrate the progressive loss of control over biological homeostasis and the functional impairment typical of aged tissues. Here, we review how epigenetics takes part in the control of stress stimuli and the mechanisms of ageing physiology and physiopathology. Alteration of epigenetic enzyme activity, histone modifications and DNA-methylation is, in fact, typically associated with the ageing process. Specifically, ageing presents peculiar epigenetic markers that, taken altogether, form the still ill-defined “ageing epigenome”. The comprehension of mechanisms and pathways leading to epigenetic modifications associated with ageing may help the development of anti-ageing therapies.
epigenetics; ageing; oxidative stress; cardiovascular; endothelial; cardiac
It is well established that the activity of chromatin-modifying enzymes is crucial for regulating gene expression associated with hippocampal-dependent memories. However, very little is known about how these epigenetic mechanisms influence the formation of cortically-dependent memory, particularly when there is competition between opposing memory traces such as that which occurs during the acquisition and extinction of conditioned fear. Here we demonstrate, in C57/Bl6 mice, that the activity of p300/CBP-associated factor (PCAF) within the infralimbic prefrontal cortex is required for long-term potentiation and is necessary for the formation of memory associated with fear extinction, but not for fear acquisition. Further, systemic administration of the PCAF activator SPV106 enhances memory for fear extinction and prevents fear renewal. The selective influence of PCAF on fear extinction is mediated, in part, by a transient recruitment of the repressive transcription factor ATF4 to the promoter of the immediate early gene zif268, which competitively inhibits its expression. Thus, within the context of fear extinction, PCAF functions as a transcriptional co-activator, which may facilitate the formation of memory for fear extinction by interfering with reconsolidation of the original memory trace.
PCAF; fear extinction; infralimbic prefrontal cortex; ATF4; zif268; memory; H3-CoA-20-Tat; SPV106
BIX-01294 and its analogs were originally identified and subsequently designed as potent inhibitors against histone H3 lysine 9 (H3K9) methyltransferases G9a and G9a-like protein (GLP). Here we show BIX-01294 and its analog E67 can also inhibit H3K9 Jumonji demethylase KIAA1718 with half-maximal inhibitory concentrations in low micro-molar range. Crystallographic analysis of KIAA1718 Jumonji domain in complex with E67 indicated the benzylated six-membered piperidine ring was disordered and exposed to solvent. Removing the moiety (generating compound E67-2) has no effect on the potency against KIAA1718, but unexpectedly lost inhibition against GLP by a factor of 1500. Furthermore, E67 and E67-2 have no effect on the activity against histone H3 lysine 4 (H3K4) demethylase JARID1C. Thus our study provides a new avenue for designing and improving the potency and selectivity of inhibitors against H3K9 Jumonji demethylases over H3K9 methyltransferases as well as H3K4 demethylases.
Epigenetics; Histone lysine demethylation; Enzymatic inhibition; BIX analogs
The conversion of a quiescent vitamin A storing hepatic stellate cell (HSC) to a matrix producing, contractile myofibroblast-like activated HSC is a key event in the onset of liver disease following injury of any aetiology. Previous studies have shown that class I histone deacetylases (HDACs) are involved in the phenotypical changes occurring during stellate cell activation in liver and pancreas.
In the current study we investigate the role of class II HDACs during HSC activation.
We characterized the expression of the class II HDACs freshly isolated mouse HSCs. We inhibited HDAC activity by selective pharmacological inhibition with MC1568, and by repressing class II HDAC gene expression using specific siRNAs.
Inhibition of HDAC activity leads to a strong reduction of HSC activation markers α-SMA, lysyl oxidase and collagens as well as an inhibition of cell proliferation. Knock down experiments showed that HDAC4 contributes to HSC activation by regulating lysyl oxidase expression. In addition, we observed a strong up regulation of miR-29, a well-known anti-fibrotic miR, upon treatment with MC1568. Our in vivo work suggests that a successful inhibition of class II HDACs could be promising for development of future anti-fibrotic compounds.
In conclusion, the use of MC1568 has enabled us to identify a role for class II HDACs regulating miR-29 during HSC activation.
Coactivator-associated arginine methyltransferase 1 (CARM1) represents a valuable target for hormone-dependent tumors such as prostate and breast cancers. Here we report the enzyme and cellular characterization of the 1-benzyl-3,5-bis(3-bromo-4-hydroxybenzylidene) piperidin-4-one (7g) and its analogues 8a-l. Among them, 7g, 8e, and 8l displayed high and selective CARM1 inhibition, with lower or no activity against a panel of different PRMTs or HKMTs. In human LNCaP cells, 7g showed a significant dose-dependent reduction of the PSA promoter activity.
Class IIa histone deacetylases (HDACs) belong to a large family of enzymes involved in protein deacetylation and play a role in regulating gene expression and cell differentiation. Previously, we showed that HDAC inhibitors modify the timing and determination of pancreatic cell fate. The aim of this study was to determine the role of class IIa HDACs in pancreas development.
RESEARCH DESIGN AND METHODS
We took a genetic approach and analyzed the pancreatic phenotype of mice lacking HDAC4, -5, and -9. We also developed a novel method of lentiviral infection of pancreatic explants and performed gain-of-function experiments.
We show that class IIa HDAC4, -5, and -9 have an unexpected restricted expression in the endocrine β- and δ-cells of the pancreas. Analyses of the pancreas of class IIa HDAC mutant mice revealed an increased pool of insulin-producing β-cells in Hdac5−/− and Hdac9−/− mice and an increased pool of somatostatin-producing δ-cells in Hdac4−/− and Hdac5−/− mice. Conversely, HDAC4 and HDAC5 overexpression showed a decreased pool of insulin-producing β-cells and somatostatin-producing δ-cells. Finally, treatment of pancreatic explants with the selective class IIa HDAC inhibitor MC1568 enhances expression of Pax4, a key factor required for proper β-and δ-cell differentiation and amplifies endocrine β- and δ-cells.
We conclude that HDAC4, -5, and -9 are key regulators to control the pancreatic β/δ-cell lineage. These results highlight the epigenetic mechanisms underlying the regulation of endocrine cell development and suggest new strategies for β-cell differentiation-based therapies.
Early prostate cancer (PCa) is generally treatable and associated with good prognosis. After a variable time, PCa evolves into a highly metastatic and treatment-refractory disease: castration-resistant PCa (CRPC). Currently, few prognostic factors are available to predict the emergence of CRPC, and no curative option is available. Epigenetic gene regulation has been shown to trigger PCa metastasis and androgen-independence. Most epigenetic studies have focused on DNA and histone methyltransferases. While DNA methylation leads to gene silencing, histone methylation can trigger gene activation or inactivation, depending on the target amino acid residues and the extent of methylation (me1, me2, or me3). Interestingly, some histone modifiers are essential for PCa tumor-initiating cell (TIC) self-renewal. TICs are considered the seeds responsible for metastatic spreading and androgen-independence. Histone Lysine Demethylases (KDMs) are a novel class of epigenetic enzymes which can remove both repressive and activating histone marks. KDMs are currently grouped into 7 major classes, each one targeting a specific methylation site. Since their discovery, KDM expression has been found to be deregulated in several neoplasms. In PCa, KDMs may act as either tumor suppressors or oncogenes, depending on their gene regulatory function. For example, KDM1A and KDM4C are essential for PCa androgen-dependent proliferation, while PHF8 is involved in PCa migration and invasion. Interestingly, the possibility of pharmacologically targeting KDMs has been demonstrated. In the present paper, we summarize the emerging role of KDMs in regulating the metastatic potential and androgen-dependence of PCa. In addition, we speculate on the possible interaction between KDMs and other epigenetic effectors relevant for PCa TICs. Finally, we explore the role of KDMs as novel prognostic factors and therapeutic targets. We believe that studies on histone demethylation may add a novel perspective in our efforts to prevent and cure advanced PCa.
Prostate cancer; Epigenetics; Tumor-initiating cells; Histone demethylase; Androgen receptor
From February 12–16, 2012, leading members of the sirtuin scientific community assembled in Tahoe, CA to attend the Keystone Symposium “Sirtuins in Aging, Metabolism, and Disease.” It was a vibrant and lively meeting, and in the spirit of Keystone Symposia, both established sirtuin researchers and those new to the field enjoyed a unique opportunity to interact and exchange ideas.
Endothelial barrier dysfunction (EBD) involves microtubule disassembly and enhanced cell contractility. Histone deacetylase 6 (HDAC6) deacetylates α-tubulin, and thereby destabilizes microtubules. This study investigates a role for HDAC6 in EBD.
EBD was induced with thrombin±HDAC6 inhibitors (tubacin and MC1575), and assessed by transendothelial electrical resistance (TEER). Markers for microtubule disassembly (α-tubulin and acetylated α-tubulin) and contraction (phosporylated myosin light chain 2, P-MLC2) were measured using immunoblots and immunofluorescence.
Results and Conclusion
Thrombin induced a ~50% decrease in TEER that was abrogated by the HDAC6 inhibitors. Moreover, inhibition of HDAC6 diminished edema in the lung injured by lipopolysacchride. Lastly, inhibition of HDAC6 attenuated thrombin- induced microtubule disassembly and P-MLC2. Our results suggest that HDAC6 can be targeted to limit EBD.
Ovarian cancer frequently acquires resistance to platinum chemotherapy, representing a major challenge for improving patient survival. Recent work suggests resistant clones exist within a larger drug sensitive cell-population prior to chemotherapy, implying that resistance is selected for rather than generated by treatment. We sought to compare clinically-derived, intra-patient paired models of initial platinum response and subsequent resistant relapse to define molecular determinants of evolved resistance. Transcriptional analysis of a matched cell-line series from three patients with high-grade serous ovarian cancer before and after development of clinical platinum resistance (PEO1/PEO4/PEO6, PEA1/PEA2, PEO14/PEO23) identified 91 up- and 126 down-regulated genes common to acquired resistance. Significantly enhanced apoptotic response to platinum treatment in resistant cells was observed following knockdown of HDAC4, FOLR2, PIK3R1 or STAT1 (p<0.05). Interestingly, HDAC4 and STAT1 were found to physically interact. Acetyl-STAT1 was detected in platinum sensitive but not HDAC4 over-expressing platinum resistant cells from the same patient. In resistant cells, STAT1 phosphorylation/nuclear translocation was seen following platinum exposure, whereas silencing of HDAC4 increased acetyl-STAT1 levels, prevented platinum induced STAT1 activation and restored cisplatin sensitivity. Conversely, matched sensitive cells were refractory to STAT1 phosphorylation on platinum treatment. Analysis of 16 paired tumor biopsies taken before and after development of clinical platinum resistance showed significantly increased HDAC4 expression in resistant tumors (n=7/16[44%]; p=0.04). Therefore, clinical selection of HDAC4 overexpressing tumor cells upon exposure to chemotherapy promotes STAT1 deacetylation and cancer cell survival. Together, our findings identify HDAC4 as a novel, therapeutically tractable target to counter platinum resistance in ovarian cancer.
How regeneration cues are converted into the epigenetic information that controls gene expression in adult stem cells is currently unknown. We identified a novel inflammation-activated signalling in muscle stem (satellite) cells, by which the Polycomb Repressive Complex 2 (PRC2) represses Pax7 expression during muscle regeneration. TNF-activated p38alpha kinase promotes the interaction between YY1 and PRC2, via threonine 372 phosphorylation of EzH2, the enzymatic sub-unit of the complex, leading to the formation of repressive chromatin on Pax7 promoter. Anti-TNF antibodies stimulate satellite cell proliferation in regenerating muscles of dystrophic or normal mice. Genetic knockdown or pharmacological inhibition of the enzymatic components of the p38/PRC2 signalling – p38alpha and EzH2 - invariably promote Pax7 expression and expansion of satellite cells that retain their differentiation potential upon signalling resumption. Genetic knockdown of Pax7 impaired satellite cell proliferation in response to p38 inhibition, thereby establishing the biological link between p38/PRC2 signalling to Pax7 and satellite cell decision to proliferate or differentiate.
Pax7; p38; muscle stem (satellite) cells; regeneration; chromatin; Polycomb complex
Histone deacetylases (HDAC) are key enzymes in the epigenetic control of gene expression. Recently, inhibitors of class I and class II HDAC have been successfully employed for the treatment of different inflammatory diseases such as rheumatoid arthritis, colitis, airway inflammation and asthma. So far, little is known so far about a similar therapeutic effect of inhibitors specifically directed against sirtuins, the class III HDAC. In this study, we investigated the expression and localization of endogenous sirtuins in primary human dermal microvascular endothelial cells (HDMEC), a cell type playing a key role in the development and maintenance of skin inflammation. We then examined the biological activity of sirtinol, a specific sirtuin inhibitor, in HDMEC response to pro-inflammatory cytokines. We found that, even though sirtinol treatment alone affected only long-term cell proliferation, it diminishes HDMEC inflammatory responses to tumor necrosis factor (TNF)α and interleukin (IL)-1β. In fact, sirtinol significantly reduced membrane expression of adhesion molecules in TNFã- or IL-1β-stimulated cells, as well as the amount of CXCL10 and CCL2 released by HDMEC following TNFα treatment. Notably, sirtinol drastically decreased monocyte adhesion on activated HDMEC. Using selective inhibitors for Sirt1 and Sirt2, we showed a predominant involvement of Sirt1 inhibition in the modulation of adhesion molecule expression and monocyte adhesion on activated HDMEC. Finally, we demonstrated the in vivo expression of Sirt1 in the dermal vessels of normal and psoriatic skin. Altogether, these findings indicated that sirtuins may represent a promising therapeutic target for the treatment of inflammatory skin diseases characterized by a prominent microvessel involvement.
In addition to genetic disorders, epigenetic alterations have been shown to be involved in cancer, through misregulation of histone modifications. Miswriting, misreading, and mis-erasing of histone acetylation as well as methylation marks can be actually associated with oncogenesis and tumor proliferation. Historically, methylation of Arg and Lys residues has been considered a stable, irreversible process due to the slow turnover of methyl groups in chromatin. The discovery in recent years of a large number of histone Lys demethylases (KDMs, belonging to either the amino oxidase or the JmjC family) totally changed this point of view and suggested a new role for dynamic histone methylation in biological processes. Since overexpression, alteration, or mutation of a number of KDMs has been found in many types of cancers, such enzymes could represent diagnostic tools as well as epigenetic targets to modulate for obtaining novel therapeutic weapons against cancer. The first little steps in this direction are described here.
LSD1; Jumonji-containing enzymes; FAD; 2-oxoglutarate; cancer