RETRACTED: Zinc moderates circular RNA CircFOXP1 expression in order to regulate ferroptosis during lung adenocarcinoma

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. After a thorough investigation, the Editor has concluded that the acceptance of this article was partly based upon the positive advice of one illegitimate reviewer report. The report was submitted from an email account which was provided to the journal as a suggested reviewer during the submission of the article. Although purportedly a real reviewer account, the Editor has concluded that this was not of an appropriate, independent reviewer. This manipulation of the peer-review process represents a clear violation of the fundamentals of peer review, our publishing policies, and publishing ethics standards. Apologies are offered to the reviewer whose identity was assumed and to the readers of the journal that this deception was not detected during the submission process. Also, a section of the ‘circFOXP1/Merge’ panel from Fig. 1B appears similar to a section of the ‘18s/Merge’ panel from Figure 1B of the article.

Ellagic Acid Alleviates Rheumatoid Arthritis in Rats through Inhibiting MTA1/HDAC1-Mediated Nur77 Deacetylation

Ellagic acid (EA) was reported to play protective roles in rheumatoid arthritis (RA). It was found that the level of metastasis-associated gene 1 (MTA1)/histone deacetylase 1 (HDAC1) protein complex was downregulated by polyphenols in several human disorders. Notably, inhibition of MTA1 or HDAC1 has anti-inflammatory effects on RA. Therefore, our study is aimed at investigating whether EA prevents RA progression through regulating the MTA1/HDAC1 complex. Herein, the human fibroblast-like synoviocyte (FLS) cell line MH7A was treated with TNF-α to induce an inflammation model in vitro and then incubated with different concentrations of EA. Western blot analysis showed that EA reduced MTA1 expression in a dose-dependent manner in MH7A cells. Then, TNF-α-treated MH7A cells were incubated with EA alone or together with MTA1 overexpression plasmid (pcDNA-MTA1), and we found that EA inhibited proliferation, inflammation cytokine levels, and oxidative stress marker protein levels and promoted apoptosis in MH7A cells, while MTA1 overexpression abolished these effects. Moreover, coimmunoprecipitation assay verified the interaction between MTA1 and HDAC1. EA downregulated the MTA1/HDAC1 complex in MH7A cells. MTA1 knockdown inhibited proliferation, inflammation, and oxidative stress and promoted apoptosis in MH7A cells, while HDAC1 overexpression reversed these effects. Moreover, chromatin immunoprecipitation assay indicated that EA inhibited HDAC1-mediated Nur77 deacetylation. Rescue experiments demonstrated that Nur77 knockdown reversed the effects of EA on MH7A cell biological behaviors. Additionally, EA treatment attenuated arthritis index, paw swelling, synovial hyperplasia, and inflammation in collagen-induced arthritis (CIA) rats. In conclusion, EA inhibited proliferation, inflammation, and oxidative stress and promoted apoptosis in MH7A cells and alleviated the severity of RA in CIA rats though downregulating MTA1/HDAC1 complex and promoting HDAC1 deacetylation-mediated Nur77 expression.

G3BP1 inhibits Cul3SPOP to amplify AR signaling and promote prostate cancer

SPOP, an E3 ubiquitin ligase, acts as a prostate-specific tumor suppressor with several key substrates mediating oncogenic function. However, the mechanisms underlying SPOP regulation are largely unknown. Here, we have identified G3BP1 as an interactor of SPOP and functions as a competitive inhibitor of Cul3SPOP, suggesting a distinctive mode of Cul3SPOP inactivation in prostate cancer (PCa). Transcriptomic analysis and functional studies reveal a G3BP1-SPOP ubiquitin signaling axis that promotes PCa progression through activating AR signaling. Moreover, AR directly upregulates G3BP1 transcription to further amplify G3BP1-SPOP signaling in a feed-forward manner. Our study supports a fundamental role of G3BP1 in disabling the tumor suppressive Cul3SPOP, thus defining a PCa cohort independent of SPOP mutation. Therefore, there are significantly more PCa that are defective for SPOP ubiquitin ligase than previously appreciated, and these G3BP1high PCa are more susceptible to AR-targeted therapy.

Inhibition of CNOT2 Induces Apoptosis via MID1IP1 in Colorectal Cancer Cells by Activating p53

CCR4-NOT transcription complex subunit 2 (CNOT2), a subunit of the CCR4-NOT complex, has been described in cancer progression. The CNOT complex plays an important role in multiple cellular functions. Recent studies in our laboratory showed that CNOT2 promotes breast cancer cell proliferation and angiogenesis. In addition, CNOT2 signals are critically related to apoptosis induced by atorvastatin in lung cancer cells. Furthermore, depletion of CNOT2 was shown to enhance the antitumor effect of midline 1 interacting protein 1 (MID1IP1) depletion, thus inhibiting c-Myc expression in liver cancer cells. However, the molecular mechanisms related to its oncogenic role remain unclear. Herein, for the first time, we report that CNOT2 inhibition can induce apoptosis in colorectal cancer cells by activating p53. Inhibition of CNOT2 markedly induced apoptosis in various cancer cells like that of the wild-type p53. Furthermore, inhibition of CNOT2 elongated p53 s half-life. Previously, our laboratory demonstrated that MID1IP1 promoted colocalization with c-Myc mediated by CNOT2. Interestingly, inhibition of CNOT2 cannot induce p53 expression without MID1IP1 or apoptosis in cancer cells. In conclusion, our results demonstrate that CNOT2 inhibition induces apoptosis through MID1IP1 by activating p53.

Histone Deacetylase 4 Controls Extracellular Matrix Production in Orbital Fibroblasts from Graves' Ophthalmopathy Patients

Background: Graves' ophthalmopathy (GO) is an autoimmune eye disease with the characteristic symptoms of eyelid retraction and proptosis. Orbital fibroblast activation induced by platelet-derived growth factor-BB (PDGF-BB) stimulation plays a crucial role in GO pathogenesis, leading to excessive proliferation and extracellular matrix production by orbital fibroblasts. Currently, GO treatment options remain limited and novel therapies including targeted drugs are needed. Histone deacetylases (HDACs) are associated with the development and progression of several cancers and autoimmune diseases by epigenetically controlling gene transcription, and HDAC inhibitors (HDACis) may have therapeutic potential. Nevertheless, the role of HDACs in orbital fibroblasts from GO is unknown. Therefore, we studied the expression of HDACs as well as their contribution to extracellular matrix production in orbital fibroblasts. Methods: Orbital tissues were obtained from GO patients (n = 18) who underwent decompression surgery with approval from the Institutional Review Board of the Faculty of Medicine (Protocol number 401/61), Chulalongkorn University (Bangkok, Thailand). Furthermore, orbital tissue was obtained from control patients (n = 3) without inflammatory or thyroid disease who underwent surgery for cosmetic reasons. Orbital fibroblast cultures were established from the orbital tissues. HDAC mRNA and protein expression in orbital fibroblasts was analyzed by reverse transcription-quantitative real-time PCR and Western blot. PDGF-BB-activated orbital fibroblast and orbital tissues were treated with HDACis or HDAC4 small-interfering RNA. Results: PDGF-BB-stimulated orbital fibroblasts had upregulated HDAC4 mRNA and protein expression. HDAC4 mRNA expression was significantly higher in GO compared with healthy control orbital fibroblasts. Histone H3 lysine 9 acetylation (H3K9ac) decreased upon PDGF-BB stimulation. Treatment with HDAC4i (tasquinimod) and HDAC4/5i (LMK-235) significantly decreased both proliferation and hyaluronan production in PDGF-BB-stimulated orbital fibroblasts. HDAC4 silencing reduced mRNA expression of hyaluronan synthase 2 (HAS2), collagen type I alpha 1 chain (COL1A1), Ki67, and α-smooth muscle actin (α-SMA), as well as hyaluronan production in PDGF-BB-stimulated orbital fibroblasts. Tasquinimod significantly reduced HAS2 and α-SMA mRNA expression in whole orbital tissue. Conclusion: Our data indicated, for the first time, that altered HDAC4 regulation along with H3K9 hypoacetylation might represent a mechanism that contributes to excessive proliferation and extracellular matrix production by orbital fibroblasts in GO. HDAC4 might represent a novel target for GO therapy.

Double-edged Swords: Diaryl pyrazoline thiazolidinediones synchronously targeting cancer epigenetics and angiogenesis

In the present study, two novel series of compounds incorporating naphthyl and pyridyl linker were synthesized and biological assays revealed 5-((6-(2-(5-(2-chlorophenyl)-3-(4-fluorophenyl)-4,5-dihydro-1H-pyrazol-1-yl)-2-oxoethoxy) naphthalene-2-yl)methylene)thiazolidine-2,4-dione (14b) as the most potent dual inhibitors of vascular endothelial growth factors receptor-2 (VEGFR-2) and histone deacetylase 4 (HDAC4). Compounds 13b, 14b, 17f, and 21f were found to stabilize HDAC4; where, pyridyl linker swords were endowed with higher stabilization effects than naphthyl linker. Also, 13b and 14b showed best inhibitory activity on VEGFR-2 as compared to others. Compound 14b was most potent as evident by in-vitro and in-vivo biological assessments. It displayed anti-angiogenic potential by inhibiting endothelial cell proliferation, migration, tube formation and also suppressed new capillary formation in the growing chick chorioallantoic membranes (CAMs). It showed selectivity and potency towards HDAC4 as compared to other HDAC isoforms. Compound 14b (25 mg/kg, i.p.) also indicated exceptional antitumor efficacy on in-vivo animal xenograft model of human colorectal adenocarcinoma (HT-29). The mechanism of action of 14b was also confirmed by western blot.

Targeting HDAC8 to ameliorate skeletal muscle differentiation in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) causes progressive skeletal muscle degeneration and currently there are few therapeutic options. The identification of new drug targets and their validation in model systems of DMD could be a promising approach to make progress in finding new treatments for this lethal disease. Histone deacetylases (HDACs) play key roles in myogenesis and the therapeutic approach targeting HDACs in DMD is in an advanced phase of clinical trial. Here, we show that the expression of HDAC8, one of the members of the HDAC family, is increased in DMD patients and dystrophic zebrafish. The selective inhibition of HDAC8 with the PCI-34051 inhibitor rescues skeletal muscle defects, similarly to the treatment with the pan-HDAC inhibitor Givinostat. Through acetylation profile of zebrafish with HDAC8 dysregulation, we identified new HDAC8 targets involved in cytoskeleton organization such as tubulin that, when acetylated, is a marker of stable microtubules. Our work provides evidence of HDAC8 overexpression in DMD patients and zebrafish and supports its specific inhibition as a new valuable therapeutic approach in the treatment of this pathology.

Methylation of dual-specificity phosphatase 4 controls cell differentiation

Mitogen-activated protein kinases (MAPKs) are inactivated by dual-specificity phosphatases (DUSPs), the activities of which are tightly regulated during cell differentiation. Using knockdown screening and single-cell transcriptional analysis, we demonstrate that DUSP4 is the phosphatase that specifically inactivates p38 kinase to promote megakaryocyte (Mk) differentiation. Mechanistically, PRMT1-mediated methylation of DUSP4 triggers its ubiquitinylation by an E3 ligase HUWE1. Interestingly, the mechanistic axis of the DUSP4 degradation and p38 activation is also associated with a transcriptional signature of immune activation in Mk cells. In the context of thrombocytopenia observed in myelodysplastic syndrome (MDS), we demonstrate that high levels of p38 MAPK and PRMT1 are associated with low platelet counts and adverse prognosis, while pharmacological inhibition of p38 MAPK or PRMT1 stimulates megakaryopoiesis. These findings provide mechanistic insights into the role of the PRMT1-DUSP4-p38 axis on Mk differentiation and present a strategy for treatment of thrombocytopenia associated with MDS.

Epigenetics Involvement in Oxaliplatin-Induced Potassium Channel Transcriptional Downregulation and Hypersensitivity

Peripheral neuropathy is the most frequent dose-limiting adverse effect of oxaliplatin. Acute pain symptoms that are induced or exacerbated by cold occur in almost all patients immediately following the first infusions. Evidence has shown that oxaliplatin causes ion channel expression modulations in dorsal root ganglia neurons, which are thought to contribute to peripheral hypersensitivity. Most dysregulated genes encode ion channels involved in cold and mechanical perception, noteworthy members of a sub-group of potassium channels of the K2P family, TREK and TRAAK. Downregulation of these K2P channels has been identified as an important tuner of acute oxaliplatin-induced hypersensitivity. We investigated the molecular mechanisms underlying this peripheral dysregulation in a murine model of neuropathic pain triggered by a single oxaliplatin administration. We found that oxaliplatin-mediated TREK-TRAAK downregulation, as well as downregulation of other K+ channels of the K2P and Kv families, involves a transcription factor known as the neuron-restrictive silencer factor (NRSF) and its epigenetic co-repressors histone deacetylases (HDACs). NRSF knockdown was able to prevent most of these K+ channel mRNA downregulation in mice dorsal root ganglion neurons as well as oxaliplatin-induced acute cold and mechanical hypersensitivity. Interestingly, pharmacological inhibition of class I HDAC reproduces the antinociceptive effects of NRSF knockdown and leads to an increased K+ channel expression in oxaliplatin-treated mice.

A Pan-Inhibitor for Protein Arginine Methyltransferase Family Enzymes

Protein arginine methyltransferases (PRMTs) play important roles in transcription, splicing, DNA damage repair, RNA biology, and cellular metabolism. Thus, PRMTs have been attractive targets for various diseases. In this study, we reported the design and synthesis of a potent pan-inhibitor for PRMTs that tethers a thioadenosine and various substituted guanidino groups through a propyl linker. Compound II757 exhibits a half-maximal inhibition concentration (IC50) value of 5 to 555 nM for eight tested PRMTs, with the highest inhibition for PRMT4 (IC50 = 5 nM). The kinetic study demonstrated that II757 competitively binds at the SAM binding site of PRMT1. Notably, II757 is selective for PRMTs over a panel of other methyltransferases, which can serve as a general probe for PRMTs and a lead for further optimization to increase the selectivity for individual PRMT.

A Multipronged Screening Approach Targeting Inhibition of ETV6 PNT Domain Polymerization

ETV6 is an ETS family transcriptional repressor for which head-to-tail polymerization of its PNT domain facilitates cooperative binding to DNA by its ETS domain. Chromosomal translocations frequently fuse the ETV6 PNT domain to one of several protein tyrosine kinases. The resulting chimeric oncoproteins undergo ligand-independent self-association, autophosphorylation, and aberrant stimulation of downstream signaling pathways, leading to a variety of cancers. Currently, no small-molecule inhibitors of ETV6 PNT domain polymerization are known and no assays targeting PNT domain polymerization have been described. In this study, we developed complementary experimental and computational approaches for identifying such inhibitory compounds. One mammalian cellular approach utilized a mutant PNT domain heterodimer system covalently attached to split Gaussia luciferase fragments. In this protein-fragment complementation assay, inhibition of PNT domain heterodimerization reduces luminescence. A yeast assay took advantage of activation of the reporter HIS3 gene upon heterodimerization of mutant PNT domains fused to DNA-binding and transactivation domains. In this two-hybrid screen, inhibition of PNT domain heterodimerization prevents cell growth in medium lacking histidine. The Bristol University Docking Engine (BUDE) was used to identify virtual ligands from the ZINC8 library predicted to bind the PNT domain polymerization interfaces. More than 75 hits from these three assays were tested by nuclear magnetic resonance spectroscopy for binding to the purified ETV6 PNT domain. Although none were found to bind, the lessons learned from this study may facilitate future approaches for developing therapeutics that act against ETV6 oncoproteins by disrupting PNT domain polymerization.

NBM-BMX, an HDAC8 Inhibitor, Overcomes Temozolomide Resistance in Glioblastoma Multiforme by Downregulating the β-Catenin/c-Myc/SOX2 Pathway and Upregulating p53-Mediated MGMT Inhibition

Although histone deacetylase 8 (HDAC8) plays a role in glioblastoma multiforme (GBM), whether its inhibition facilitates the treatment of temozolomide (TMZ)-resistant GBM (GBM-R) remains unclear. By assessing the gene expression profiles from short hairpin RNA of HDAC8 in the new version of Connectivity Map (CLUE) and cells treated by NBM-BMX (BMX)-, an HDAC8 inhibitor, data analysis reveals that the Wnt signaling pathway and apoptosis might be the underlying mechanisms in BMX-elicited treatment. This study evaluated the efficacy of cotreatment with BMX and TMZ in GBM-R cells. We observed that cotreatment with BMX and TMZ could overcome resistance in GBM-R cells and inhibit cell viability, markedly inhibit cell proliferation, and then induce cell cycle arrest and apoptosis. In addition, the expression level of β-catenin was reversed by proteasome inhibitor via the β-catenin/ GSK3β signaling pathway to reduce the expression level of c-Myc and cyclin D1 in GBM-R cells. BMX and TMZ cotreatment also upregulated WT-p53 mediated MGMT inhibition, thereby triggering the activation of caspase-3 and eventually leading to apoptosis in GBM-R cells. Moreover, BMX and TMZ attenuated the expression of CD133, CD44, and SOX2 in GBM-R cells. In conclusion, BMX overcomes TMZ resistance by enhancing TMZ-mediated cytotoxic effect by downregulating the β-catenin/c-Myc/SOX2 signaling pathway and upregulating WT-p53 mediated MGMT inhibition. These findings indicate a promising drug combination for precision personal treating of TMZ-resistant WT-p53 GBM cells.

Generalized-ensemble method study: A helix-mimetic compound inhibits protein-protein interaction by long-range and short-range intermolecular interactions

A heterocyclic compound mS-11 is a helix-mimetic designed to inhibit binding of an intrinsic disordered protein neural restrictive silence factor/repressor element 1 silencing factor (NRSF/REST) to a receptor protein mSin3B. We apply a generalized ensemble method, multi-dimensional virtual-system coupled molecular dynamics developed by ourselves recently, to a system consisting of mS-11 and mSin3B, and obtain a thermally equilibrated distribution, which is comprised of the bound and unbound states extensively. The lowest free-energy position of mS-11 coincides with the NRSF/REST position in the experimentally-determined NRSF/REST-mSin3B complex. Importantly, the molecular orientation of mS-11 is ordering in a wide region around mSin3B. The resultant binding scenario is: When mS-11 is distant from the binding site of mSin3B, mS-11 descends the free-energy slope toward the binding site maintaining the molecular orientation to be advantageous for binding. Then, finally a long and flexible hydrophobic sidechain of mS-11 fits into the binding site, which is the lowest-free-energy complex structure inhibiting NRSF/REST binding to mSin3B.

Molecular Dynamics of Cobalt Protoporphyrin Antagonism of the Cancer Suppressor REV-ERBβ

Nuclear receptor REV-ERBβ is an overexpressed oncoprotein that has been used as a target for cancer treatment. The metal-complex nature of its ligand, iron protoporphyrin IX (Heme), enables the REV-ERBβ to be used for multiple therapeutic modalities as a photonuclease, a photosensitizer, or a fluorescence imaging agent. The replacement of iron with cobalt as the metal center of protoporphyrin IX changes the ligand from an agonist to an antagonist of REV-ERBβ. The mechanism behind that phenomenon is still unclear, despite the availability of crystal structures of REV-ERBβ in complex with Heme and cobalt protoporphyrin IX (CoPP). This study used molecular dynamic simulations to compare the effects of REV-ERBβ binding to Heme and CoPP, respectively. The initial poses of Heme and CoPP in complex with agonist and antagonist forms of REV-ERBβ were predicted using molecular docking. The binding energies of each ligand were calculated using the MM/PBSA method. The computed binding affinity of Heme to REV-ERBβ was stronger than that of CoPP, in agreement with experimental results. CoPP altered the conformation of the ligand-binding site of REV-ERBβ, disrupting the binding site for nuclear receptor corepressor, which is required for REV-ERBβ to regulate the transcription of downstream target genes. Those results suggest that a subtle change in the metal center of porphyrin can change the behavior of porphyrin in cancer cell signaling. Therefore, modification of porphyrin-based agents for cancer therapy should be conducted carefully to avoid triggering unfavorable effects.

Thiazolidinedione "Magic Bullets" Simultaneously Targeting PPARγ and HDACs: Design, Synthesis, and Investigations of their In Vitro and In Vivo Antitumor Effects

Monotargeting anticancer agents suffer from resistance and target nonspecificity concerns, which can be tackled with a multitargeting approach. The combined treatment with HDAC inhibitors and PPARγ agonists has displayed potential antitumor effects. Based on these observations, this work involves design and synthesis of molecules that can simultaneously target PPARγ and HDAC. Several out of 25 compounds inhibited HDAC4, and six compounds acted as dual-targeting agents. Compound 7i was the most potent, with activity toward PPARγ EC50 = 0.245 μM and HDAC4 IC50 = 1.1 μM. Additionally, compounds 7c and 7i were cytotoxic to CCRF-CEM cells (CC50 = 2.8 and 9.6 μM, respectively), induced apoptosis, and caused DNA fragmentation. Furthermore, compound 7c modulated the expression of c-Myc, cleaved caspase-3, and caused in vivo tumor regression in CCRF-CEM tumor xenografts. Thus, this study provides a basis for the rational design of dual/multitargeting agents that could be developed further as anticancer therapeutics.

Inhibition of MTA2 and MTA3 induces mesendoderm specification of human embryonic stem cells

Fully understanding the regulatory network under the pluripotency of embryonic stem cells (ESC) is a prerequisite for their safe application. Here, we addressed the characteristics of metastasis-associated (MTA) family members in human ESCs and found that knockdown of the expression of MTA2 and MTA3, but not MTA1, would induce differentiation. High-throughput sequence and quantitative real-time PCR showed that the decreased MTA2 or MTA3 gene transcript mainly led to the emergence of mesendoderm associated markers. Finally, based on the chemical small molecule library screening, we observed that addition of ID8, a specific inhibitor of the dual-specificity tyrosine phosphorylation-regulated kinases (DYRKs), was able to impair the differentiation phenotype induced by MTA2 and MTA3 reduction. Functional assay showed that ID8 could mediate differentiation caused by MTA2 or MTA3 knockdown mainly through inhibition of DYRK4 activity. Therefore, our finding provides the evidence that the functions of MTA family genes in human ESCs are different. Revealing the function of MTA in ESCs with different pluripotency states will help us better understand and apply stem cells.

HDAC8 promotes daunorubicin resistance of human acute myeloid leukemia cells via regulation of IL-6 and IL-8

The chemoresistance is one of the major challenges for acute myeloid leukemia (AML) treatment. We found that the expression of histone deacetylase 8 (HDAC8) was increased in daunorubicin (DNR) resistant AML cells, while targeted inhibition of HDAC8 by its specific siRNA or inhibitor can restore sensitivity of DNR treatment . Further, targeted inhibition of HDAC8 can suppress expression of interleukin 6 (IL-6) and IL-8. While recombinant IL-6 (rIL-6) and rIL-8 can reverse si-HDAC8-resored DNR sensitivity of AML cells. Mechanistical study revealed that HDAC8 increased the expression of p65, one of key components of NF-κB complex, to promote the expression of IL-6 and IL-8. It might be due to that HDAC8 can directly bind with the promoter of p65 to increase its transcription and expression. Collectively, our data suggested that HDAC8 promotes DNR resistance of human AML cells via regulation of IL-6 and IL-8.

THAP11 down-regulation may contribute to cardio-protective effects of sevoflurane anesthesia: Evidence from clinical and molecular evidence

This study aimed to explore the potential target of the cardio-protective effect induced by sevoflurane anesthesia based on evidence from clinical samples and in vitro model. Forty patients undergoing mitral valve replacement were randomly allocated to receive sevoflurane or propofol-based anesthesia. Atrial muscle specimens were collected from all patients, of which 5 were used to perform transcriptomics analysis. The cTn-I concentration was tested before, at the end of, and 24 h after surgery. In in vitro study, the expression level of the identified target gene, i.e., THAP11, was studied in H9C2 cells treated with sevoflurane or propofol. Then, we studied cell viability using CCK-8 staining, apoptosis by using flow cytometry, and cell death by lactic acid dehydrogenase (LDH) detection in H9C2 cells exposed to oxygen glucose deprivation/reoxygenation (OGD/R) injury. THAP11 was the most significantly down-regulated gene in the transcriptomics analysis (P < 0.001), as confirmed in validation samples (P = 0.006). THAP11 mRNA levels in atrial muscle specimens were positively associated with cTn-I levels at 24-h postoperatively (determination coefficient = 0.564; P < 0.001). Sevoflurane treatment down-regulated THAP11 in H9C2 cell models, which promoted cell viability, inhibited cell apoptosis, and death in the OGD/R injury cell model. Up-regulation of THAP11 reduced the protective effect of sevoflurane treatment against OGD/R injury. Sevoflurane anesthesia down-regulates the expression of THAP11, which contributes to a cardio-protective effect. THAP11 down-regulation promotes cell viability, and inhibits cell apoptosis and death, thereby protecting again myocardial injury; it may therefore be a novel target for perioperative cardio-protection.

ZBTB2 represses HIV-1 transcription and is regulated by HIV-1 Vpr and cellular DNA damage responses

Previously, we reported that cellular transcription factor ZASC1 facilitates DNA-dependent/RNA-independent recruitment of HIV-1 TAT and the cellular elongation factor P-TEFb to the HIV-1 promoter and is a critical factor in regulating HIV-1 transcriptional elongation (PLoS Path e1003712). Here we report that cellular transcription factor ZBTB2 is a novel repressor of HIV-1 gene expression. ZBTB2 strongly co-immunoprecipitated with ZASC1 and was dramatically relocalized by ZASC1 from the cytoplasm to the nucleus. Mutations abolishing ZASC1/ZBTB2 interaction prevented ZBTB2 nuclear relocalization. We show that ZBTB2-induced repression depends on interaction of cellular histone deacetylases (HDACs) with the ZBTB2 POZ domain. Further, ZASC1 interaction specifically recruited ZBTB2 to the HIV-1 promoter, resulting in histone deacetylation and transcription repression. Depleting ZBTB2 by siRNA knockdown or CRISPR/CAS9 knockout in T cell lines enhanced transcription from HIV-1 vectors lacking Vpr, but not from these vectors expressing Vpr. Since HIV-1 Vpr activates the viral LTR by inducing the ATR kinase/DNA damage response pathway, we investigated ZBTB2 response to Vpr and DNA damaging agents. Expressing Vpr or stimulating the ATR pathway with DNA damaging agents impaired ZASC1’s ability to localize ZBTB2 to the nucleus. Moreover, the effects of DNA damaging agents and Vpr on ZBTB2 localization could be blocked by ATR kinase inhibitors. Critically, Vpr and DNA damaging agents decreased ZBTB2 binding to the HIV-1 promoter and increased promoter histone acetylation. Thus, ZBTB2 is recruited to the HIV-1 promoter by ZASC1 and represses transcription, but ATR pathway activation leads to ZBTB2 removal from the promoter, cytoplasmic sequestration and activation of viral transcription. Together, our data show that ZASC1/ZBTB2 integrate the functions of TAT and Vpr to maximize HIV-1 gene expression.

The Human immunodeficiency virus 1 (HIV-1) TAT and VPR proteins, in combination with cellular transcription factors, regulate the switch between transcriptionally active productive infection and the transcriptionally inactive latent state. Previously we reported that ZASC1, a cellular transcription factor linked to multiple squamous cell carcinomas and inherited ataxias, contributes to an RNA-independent, DNA-dependent step in recruiting the TAT/P-TEFb complex that is critical for HIV-1 transcription elongation to the HIV-1 promoter. Here we show ZASC1 interacts with ZBTB2, another cellular transcription factor with strong links to cancer. ZASC1 interaction relocalizes ZBTB2 from the cytoplasm to the HIV-1 promoter in the nucleus where ZBTB2 interacts with cellular HDACs, increases HIV-1 promoter histone deacetylation and represses viral transcription. We show that Vpr-mediated activation of the ATR/DNA damage pathway regulates ZBTB2 relocalization by ZASC1. Thus, the cellular transcription factors ZASC1 and ZBTB2 regulate the transcription elongation activities of HIV-1 TAT and the Vpr activation of the cellular DNA damage response pathway to determine the transcriptional fate of the HIV-1 provirus. These results also have strong implications for the role of ZASC1/ZBTB2 and the DNA damage response in cancer and inherited ataxias.

Developing protein arginine methyltransferase 1 (PRMT1) inhibitor TC-E-5003 as an antitumor drug using INEI drug delivery systems

Injectable implants with the ability to form in situ are one of the most promising carriers for the delivery of chemotherapeutic drugs to tumor sites. We have reported a novel injectable in situ-forming implant system composed of n-butyl-2-cyanoacrylate (NBCA), ethyl oleate, along with the sol-gel phase transition. The chemotherapeutic drug-loaded injectable NBCA ethyl oleate implant (INEI) exhibited excellent therapeutic efficacy for local chemotherapy. Herein, we utilize this INEI to carry N, N'-(Sulfonyldi-4,1-phenylene)bis(2-chloroacetamide) (TE-C-5003), which is a selective protein arginine methyltransferase 1 (PRMT1) inhibitor, to treat the lung cancer mice model. The in vitro experiment shows that TE-C-5003 has a good anti-tumor effect on lung cancer (IC50 = 0.7022 µM for A549; IC50 = 0.6844 µM for NCL-H1299) and breast cancer (IC50 = 0.4128 µM for MCF-7; IC50 = 0.5965 µM for MDA-MB-231). Anti-tumor experiments in animal models showed that the average growth inhibition rate of xenografted human lung cancer cells by the TE-C-5003-loaded INEI (40% NBCA) was 68.23%, which is far more than TC-E-5003 alone (31.76%). Our study further confirms that INEI is an effective technique to improve the anti-tumor effect. The druggability of small molecule compounds can be improved with the help of the mentioned technology. Also, TC-E-5003 may be developed as a broad spectrum anti-tumor drug.

PRMT1 inhibition induces differentiation of colon cancer cells

Differentiation therapy has been recently revisited as a prospective approach in cancer therapy by targeting the aberrant growth, and repairing the differentiation and cell death programs of cancer cells. However, differentiation therapy of solid tumors is a challenging issue and progress in this field is limited. We performed High Throughput Screening (HTS) using a novel dual multiplex assay to discover compounds, which induce differentiation of human colon cancer cells. Here we show that the protein arginine methyl transferase (PRMT) type 1 inhibitor, MS023, is a potent inducer of colon cancer cell differentiation with a large therapeutic window. Differentiation changes in the highly aggressive human colon cancer cell line (HT-29) were proved by proteomic and genomic approaches. Growth of HT-29 xenograft in nude mice was significantly delayed upon MS023 treatment and immunohistochemistry of tumor indicated differentiation changes. These findings may lead to development of clinically effective anti-cancer drugs based on the mechanism of cancer cell differentiation.

Identification of Differentially Methylated Regions Associated with a Knockout of SUV39H1 in Prostate Cancer Cells

Epigenetic alterations, such as histone methylations, affect the pathogenesis of tumors including prostate cancer (PCa). Previously, we reported that metformin reduced SUV39H1, a histone methyltransferase of H3 Lys9, to inhibit the migration of PCa cells. Since histone methylation is functionally linked to DNA methylation, we speculate that the knockout of the SUV39H1 gene will affect the genomic DNA methylation profile to regulate PCa cell migration and invasion. The genome-wide DNA methylation level is lower in SUV39H1 knockout (KO) cells than wild-type (WT) ones. However, the methylation levels in functional regions of CpG Islands (CGI), 5' untranslated region (UTR5), and exon regions are higher in KO cells than WT cells. Analysis of differentially methylated regions (DMRs) identified 1241 DMR genes that have differential methylation on CG sites when comparing the KO and WT samples. Gene ontology enrichment and Kyoto Encyclopedia of Genes and Genomes Pathways analysis showed that knockout of SUV39H1 affects gene sets and pathways that are heavily involved in cell shapes, cell recognition, adhesion, motility, and migration. Our study suggests that SUV39H1 plays an important role in PCa migration via the epigenetic regulation of methylation on CG sites, and is a novel and legitimate target to inhibit PCa cell migration.

Chromatin modifier MTA1 regulates mitotic transition and tumorigenesis by orchestrating mitotic mRNA processing

Dysregulated alternative splicing (AS) driving carcinogenetic mitosis remains poorly understood. Here, we demonstrate that cancer metastasis-associated antigen 1 (MTA1), a well-known oncogenic chromatin modifier, broadly interacts and co-expresses with RBPs across cancers, contributing to cancerous mitosis-related AS. Using developed fCLIP-seq technology, we show that MTA1 binds abundant transcripts, preferentially at splicing-responsible motifs, influencing the abundance and AS pattern of target transcripts. MTA1 regulates the mRNA level and guides the AS of a series of mitosis regulators. MTA1 deletion abrogated the dynamic AS switches of variants for ATRX and MYBL2 at mitotic stage, which are relevant to mitosis-related tumorigenesis. MTA1 dysfunction causes defective mitotic arrest, leads to aberrant chromosome segregation, and results in chromosomal instability (CIN), eventually contributing to tumorigenesis. Currently, little is known about the RNA splicing during mitosis; here, we uncover that MTA1 binds transcripts and orchestrates dynamic splicing of mitosis regulators in tumorigenesis.

The transcriptional repressor REV-ERB as a novel target for disease

REV-ERB is a member of the nuclear receptor superfamily of transcription factors involved in the regulation of many physiological processes, from circadian rhythm, to immune function and metabolism. Accordingly, REV-ERB has been considered as a promising, but difficult drug target for the treatment of numerous diseases. Here, we concisely review current understanding of the function of REV-ERB, modulation by endogenous factors and synthetic ligands, and the involvement of REV-ERB in select human diseases. Particular focus is placed on the medicinal chemistry of synthetic REV-ERB ligands, which demonstrates the need for higher quality ligands to aid in robust validation of this exciting target.

Simultaneous inhibition of MarR by salicylate and efflux pumps by curcumin sensitizes colistin resistant clinical isolates of Enterobacteriaceae

Carbapenem resistant Enterobacteriaceae (CRE) infection has been widely treated with last resort antibiotics like colistin. Resistance to colistin has further jeopardized the situation. We have previously reported a combination of MarR inhibitor - salicylate (Sal) and an efflux pump inhibitor (BC1) that successfully restored colistin (Col) sensitivity in multidrug and colistin resistant clinical isolate of E. coli U3790. Since synthetic compounds usually fail during drug development initiatives, we attempted to replace synthetic efflux pump inhibitor (BC1) with plant metabolite as efflux pump inhibitor to restore colistin sensitivity in CRE. Screening 13 plant metabolites, we narrowed on curcumin (CUR) to effectively inhibit efflux in both colistin resistant E. coli U3790 and K. pneumoniae BC936. Combination of Col + CUR showed a remarkable reversal in colistin MIC by 128 fold and 32 fold in E. coli U3790 and K. pneumoniae BC936 respectively. Studies with knock out mutant strains of AcrAB-TolC pump components show that curcumin's efflux inhibition is partly mediated by acrB. Thus, curcumin reduced colistin MIC well below the CLSI breakpoint (<2 μg/ml). Curcumin also exhibited synergy with colistin against most of the clinical isolates of Enterobacteriaceae tested. Efficiency of Col + Sal + CUR was evident in time kill curve analysis, which displayed a 6 log and a 4 log decline in CFU/ml by 24 h in U3790 and BC936 strains respectively. In vivo intramuscular fish infection studies showed that the triad combination reduced the bacterial bioburden of E. coli U3790 by 2.6 log and that of K. pneumoniae BC936 by 1.6 log. Hence, our study shows the efficacy of inhibiting MarR by salicylate and inhibiting efflux pump with curcumin restores colistin sensitivity in colistin resistant Enterobacteriaceae in vitro and in vivo.

A distal regulatory region of a class I human histone deacetylase

Histone deacetylases (HDACs) are key enzymes in epigenetics and important drug targets in cancer biology. Whilst it has been established that HDACs regulate many cellular processes, far less is known about the regulation of these enzymes themselves. Here, we show that HDAC8 is allosterically regulated by shifts in populations between exchanging states. An inactive state is identified, which is stabilised by a range of mutations and resembles a sparsely-populated state in equilibrium with active HDAC8. Computational models show that the inactive and active states differ by small changes in a regulatory region that extends up to 28 Å from the active site. The regulatory allosteric region identified here in HDAC8 corresponds to regions in other class I HDACs known to bind regulators, thus suggesting a general mechanism. The presented results pave the way for the development of allosteric HDAC inhibitors and regulators to improve the therapy for several disease states.

Design and Synthesis of Dihydroxamic Acids as HDAC6/8/10 Inhibitors

We report the synthesis and evaluation of a class of selective multitarget agents for the inhibition of HDAC6, HDAC8, and HDAC10. The concept for this study grew out of a structural analysis of the two selective inhibitors Tubastatin A (HDAC6/10) and PCI-34051 (HDAC8), which we recognized share the same N-benzylindole core. Hybridization of the two inhibitor structures resulted in dihydroxamic acids with benzyl-indole and -indazole core motifs. These substances exhibit potent activity against HDAC6, HDAC8, and HDAC10, while retaining selectivity over HDAC1, HDAC2, and HDAC3. The best substance inhibited the viability of the SK-N-BE(2)C neuroblastoma cell line with an IC50 value similar to a combination treatment with Tubastatin A and PCI-34051. This compound class establishes a proof of concept for such hybrid molecules and could serve as a starting point for the further development of enhanced HDAC6/8/10 inhibitors.

Discovery of novel N-substituted thiazolidinediones (TZDs) as HDAC8 inhibitors: in-silico studies, synthesis, and biological evaluation

Epigenetics plays a fundamental role in cancer progression, and developing agents that regulate epigenetics is crucial for cancer management. Among Class I and Class II HDACs, HDAC8 is one of the essential epigenetic players in cancer progression. Therefore, we designed, synthesized, purified, and structurally characterized novel compounds containing N-substituted TZD (P1-P25). Cell viability assay of all compounds on leukemic cell lines (CEM, K562, and KCL22) showed the cytotoxic potential of P8, P9, P10, P12, P19, and P25. In-vitro screening of different HDACs isoforms revealed that P19 was the most potent and selective inhibitor for HDAC8 (IC50 - 9.3 μM). Thermal shift analysis (TSA) confirmed the binding of P19 to HDAC8. In-vitro screening of all compounds on the transport activity of GLUT1, GLUT4, and GLUT5 indicated that P19 inhibited GLUT1 (IC50 - 28.2 μM). P10 and P19 induced apoptotic cell death in CEM cells (55.19% and 60.97% respectively) and P19 was less cytotoxic on normal WBCs (CC50 - 104.2 μM) and human fibroblasts (HS27) (CC50 - 105.0 μM). Thus, among this novel series of TZD derivatives, compound P19 was most promising HDAC8 inhibitor and cytotoxic on leukemic cells. Thus, P19 could serve as a lead for further development of optimized molecules with enhanced selectivity and potency.

Purpurin modulates Tau-derived VQIVYK fibrillization and ameliorates Alzheimer's disease-like symptoms in animal model

Neurofibrillary tangles of the Tau protein and plaques of the amyloid β peptide are hallmarks of Alzheimer's disease (AD), which is characterized by the conversion of monomeric proteins/peptides into misfolded β-sheet rich fibrils. Halting the fibrillation process and disrupting the existing aggregates are key challenges for AD drug development. Previously, we performed in vitro high-throughput screening for the identification of potent inhibitors of Tau aggregation using a proxy model, a highly aggregation-prone hexapeptide fragment 306VQIVYK311 (termed PHF6) derived from Tau. Here we have characterized a hit molecule from that screen as a modulator of Tau aggregation using in vitro, in silico, and in vivo techniques. This molecule, an anthraquinone derivative named Purpurin, inhibited ~ 50% of PHF6 fibrillization in vitro at equimolar concentration and disassembled pre-formed PHF6 fibrils. In silico studies showed that Purpurin interacted with key residues of PHF6, which are responsible for maintaining its β-sheets conformation. Isothermal titration calorimetry and surface plasmon resonance experiments with PHF6 and full-length Tau (FL-Tau), respectively, indicated that Purpurin interacted with PHF6 predominantly via hydrophobic contacts and displayed a dose-dependent complexation with FL-Tau. Purpurin was non-toxic when fed to Drosophila and it significantly ameliorated the AD-related neurotoxic symptoms of transgenic flies expressing WT-FL human Tau (hTau) plausibly by inhibiting Tau accumulation and reducing Tau phosphorylation. Purpurin also reduced hTau accumulation in cell culture overexpressing hTau. Importantly, Purpurin efficiently crossed an in vitro human blood-brain barrier model. Our findings suggest that Purpurin could be a potential lead molecule for AD therapeutics.

siRNA inhibition and not chemical inhibition of Suv39h1/2 enhances pre-implantation embryonic development of bovine somatic cell nuclear transfer embryos

The efficiency of somatic cell nuclear transfer (SCNT) is low due to the strong resistance of somatic donor cells to epigenetic reprogramming. Many epigenetic drugs targeting DNA methylation and histone acetylation have been used in attempts to improve the in vitro and in vivo development of SCNT embryos. H3K9me3 has been shown to be an important reprogramming barrier for generating induced pluripotent stem cells (iPSCs) and SCNT embryos in mice and humans. In this study, we examined the effects of selective siRNA and chemical inhibition of H3K9me3 in somatic donor cells on the in vitro development of bovine SCNT embryos. Chaetocin, an inhibitor of SUV39H1/H2, was supplemented during the culture of donor cells. In addition, the siRNA knockdown of SUV39H1/H2 was performed in the donor cells. The effects of chaetocin and siSUV39H1/H2 on H3K9me3 and H3K9ac were quantified using flow cytometry. Furthermore, we assessed chaetocin treatment and SUV39H1/H2 knockdown on the blastocyst formation rate. Both chaetocin and siSUV39H1/H2 significantly reduced and elevated the relative intensity level of H3K9me3 and H3K9ac in treated fibroblast cells, respectively. siSUV39H1/H2 transfection, but not chaetocin treatment, improved the in vitro development of SCNT embryos. Moreover, siSUV39H1/H2 altered the expression profile of the selected genes in the derived blastocysts, similar to those derived from in vitro fertilization (IVF). In conclusion, our results demonstrated H3K9me3 as an epigenetic barrier in the reprogramming process mediated by SCNT in bovine species, a finding which supports the role of H3K9me3 as a reprogramming barrier in mammalian species. Our findings provide a promising approach for improving the efficiency of mammalian cloning for agricultural and biomedical purposes.

Inhibition of REV-ERBs stimulates microglial amyloid-beta clearance and reduces amyloid plaque deposition in the 5XFAD mouse model of Alzheimer's disease

A promising new therapeutic target for the treatment of Alzheimer's disease (AD) is the circadian system. Although patients with AD are known to have abnormal circadian rhythms and suffer sleep disturbances, the role of the molecular clock in regulating amyloid-beta (Aβ) pathology is still poorly understood. Here, we explored how the circadian repressors REV-ERBα and β affected Aβ clearance in mouse microglia. We discovered that, at Circadian time 4 (CT4), microglia expressed higher levels of the master clock protein BMAL1 and more rapidly phagocytosed fibrillary Aβ1-42 (fAβ1-42 ) than at CT12. BMAL1 directly drives transcription of REV-ERB proteins, which are implicated in microglial activation. Interestingly, pharmacological inhibition of REV-ERBs with the small molecule antagonist SR8278 or genetic knockdown of REV-ERBs-accelerated microglial uptake of fAβ1-42 and increased transcription of BMAL1. SR8278 also promoted microglia polarization toward a phagocytic M2-like phenotype with increased P2Y12 receptor expression. Finally, constitutive deletion of Rev-erbα in the 5XFAD model of AD decreased amyloid plaque number and size and prevented plaque-associated increases in disease-associated microglia markers including TREM2, CD45, and Clec7a. Altogether, our work suggests a novel strategy for controlling Aβ clearance and neuroinflammation by targeting REV-ERBs and provides new insights into the role of REV-ERBs in AD.

PRMT1-mediated methylation of the microprocessor-associated proteins regulates microRNA biogenesis

MicroRNA (miRNA) biogenesis is a tightly controlled multi-step process operated in the nucleus by the activity of the Microprocessor and its associated proteins. Through high resolution mass spectrometry (MS)- proteomics we discovered that this complex is extensively methylated, with 84 methylated sites associated to 19 out of its 24 subunits. The majority of the modifications occurs on arginine (R) residues (61), leading to 81 methylation events, while 30 lysine (K)-methylation events occurs on 23 sites of the complex. Interestingly, both depletion and pharmacological inhibition of the Type-I Protein Arginine Methyltransferases (PRMTs) lead to a widespread change in the methylation state of the complex and induce global decrease of miRNA expression, as a consequence of the impairment of the pri-to-pre-miRNA processing step. In particular, we show that the reduced methylation of the Microprocessor subunit ILF3 is linked to its diminished binding to the pri-miRNAs miR-15a/16, miR-17-92, miR-301a and miR-331. Our study uncovers a previously uncharacterized role of R-methylation in the regulation of miRNA biogenesis in mammalian cells.

The emerging role of SPOP protein in tumorigenesis and cancer therapy

The nuclear speckle-type pox virus and zinc finger (POZ) protein (SPOP), a representative substrate-recognition subunit of the cullin-RING E3 ligase, has been characterized to play a dual role in tumorigenesis and cancer progression. Numerous studies have determined that SPOP suppresses tumorigenesis in a variety of human malignancies such as prostate, lung, colon, gastric, and liver cancers. However, several studies revealed that SPOP exhibited oncogenic function in kidney cancer, suggesting that SPOP could exert its biological function in a cancer type-specific manner. The role of SPOP in thyroid, cervical, ovarian, bone and neurologic cancers has yet to be determined. In this review article, we describe the structure and regulation of SPOP in human cancer. Moreover, we highlight the critical role of SPOP in tumorigenesis based on three major categories: physiological evidence (animal models), pathological evidence (human cancer specimens) and biochemical evidence (downstream ubiquitin substrates). Furthermore, we note that SPOP could be a promising therapeutic target for cancer treatment.

The VHL/HIF Axis in the Development and Treatment of Pheochromocytoma/Paraganglioma

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors originating from chromaffin cells in the adrenal medulla (PCCs) or extra-adrenal sympathetic or parasympathetic paraganglia (PGLs). About 40% of PPGLs result from germline mutations and therefore they are highly inheritable. Although dysfunction of any one of a panel of more than 20 genes can lead to PPGLs, mutations in genes involved in the VHL/HIF axis including PHD, VHL, HIF-2A (EPAS1), and SDHx are more frequently found in PPGLs. Multiple lines of evidence indicate that pseudohypoxia plays a crucial role in the tumorigenesis of PPGLs, and therefore PPGLs are also known as metabolic diseases. However, the interplay between VHL/HIF-mediated pseudohypoxia and metabolic disorder in PPGLs cells is not well-defined. In this review, we will first discuss the VHL/HIF axis and genetic alterations in this axis. Then, we will dissect the underlying mechanisms in VHL/HIF axis-driven PPGL pathogenesis, with special attention paid to the interplay between the VHL/HIF axis and cancer cell metabolism. Finally, we will summarize the currently available compounds/drugs targeting this axis which could be potentially used as PPGLs treatment, as well as their underlying pharmacological mechanisms. The overall goal of this review is to better understand the role of VHL/HIF axis in PPGLs development, to establish more accurate tools in PPGLs diagnosis, and to pave the road toward efficacious therapeutics against metastatic PPGLs.

The role of hypoxia-inducible factors in neovascular age-related macular degeneration: a gene therapy perspective

Understanding the mechanisms that underlie age-related macular degeneration (AMD) has led to the identification of key molecules. Hypoxia-inducible transcription factors (HIFs) have been associated with choroidal neovascularization and the progression of AMD into the neovascular clinical phenotype (nAMD). HIFs regulate the expression of multiple growth factors and cytokines involved in angiogenesis and inflammation, hallmarks of nAMD. This knowledge has propelled the development of a new group of therapeutic strategies focused on gene therapy. The present review provides an update on current gene therapies in ocular angiogenesis, particularly nAMD, from both basic and clinical perspectives.

Induction of Apoptosis and Autophagy in Breast Cancer Cells by a Novel HDAC8 Inhibitor

Epigenetic therapy has been demonstrated to be a viable strategy for breast cancer treatment. In this study, we report the anti-tumor activity of a hydroxamate-based histone deacetylase (HDAC)8-selective inhibitor, HMC, in breast cancer cells. MTT assays showed that HMC inhibited cell viability of MCF-7 and MDA-MB-231 cells with IC₅₀ values of 7.7 μM and 9.5 μM, respectively. HMC induced caspase-dependent apoptosis in MCF-7 cells, which was associated with its ability to modulate a series of cell survival-related signaling effectors, including Akt, mTOR, Bax, Mcl-1, and Bcl-2. Additionally, HMC was capable of activating PPARγ, which was accompanied by reduced expression of PPARγ target gene products, such as cyclin D1 and CDK6. HMC increased the production of ROS in MCF-7 cells, which could be partially reversed by the cotreatment with a ROS scavenger (N-acetylcysteine or glutathione). Furthermore, HMC induced autophagy, as characterized by the formation of acidic vesicular organelles and autophagic biomarkers including LC3B-II and Atg5. Notably, pharmacological blockade of autophagy by 3-MA or CQ could attenuate HMC-induced apoptosis, suggesting that autophagy played a self-protective role in HMC-induced cell death. Together, these data suggest the translational potential of HMC to be developed into a potential therapeutic agent for breast cancer therapy.

Discovery of 3,3'-pyrrolidinyl-spirooxindoles as cardioprotectant prohibitin ligands

The scaffold proteins prohibitins-1 and 2 (PHB1/2) play many important roles in coordinating many cell signaling pathways and represent emerging targets in cardiology and oncology. We previously reported that a family of natural products derivatives, flavaglines, binds to PHB1/2 to exert cardioprotectant and anti-cancer effects. However, flavaglines also target the initiation factor of translation eIF4A, which doesn't contribute to cardioprotection and may even induce some adverse effects. Herein, we report the development of a convenient and robust synthesis of the new PHB2 ligand 2'-phenylpyrrolidinyl-spirooxindole, and its analogues. We discovered that these compounds displays cardioprotective effect against doxorubicin mediated cardiotoxicity and uncovered the structural requirement for this activity. We identified in particular some analogues that are more cardioprotectant than flavaglines. Pull-down experiments demonstrated that these compounds bind not only to PHB2 but also PHB1. These novel PHB ligands may provide the basis for the development of new drugs candidates to protect the heart against the adverse effects of anticancer treatments.

A novel small-molecule inhibitor of the human papillomavirus E6-p53 interaction that reactivates p53 function and blocks cancer cells growth

Despite prophylactic vaccination campaigns, human papillomavirus (HPV)-induced cancers still represent a major medical issue for global population, thus specific anti-HPV drugs are needed. Since the ability of HPV E6 oncoprotein to promote p53 degradation is linked to tumor progression, E6 has been proposed as an ideal target for cancer treatment. Using the crystal structure of the E6/E6AP/p53 complex, we performed an in silico screening of small-molecule libraries against a highly conserved alpha-helix in the N-terminal domain of E6 involved in the E6-p53 interaction. We discovered a compound able to inhibit the E6-mediated degradation of p53 through disruption of E6-p53 binding both in vitro and in cells. This compound could restore p53 intracellular levels and transcriptional activity, reduce the viability and proliferation of HPV-positive cancer cells, and block 3D cervospheres formation. Mechanistic studies revealed that the compound anti-tumor activity mainly relies on induction of cell cycle arrest and senescence. Our data demonstrate that the disruption of the direct E6-p53 interaction can be obtained with a small-molecule compound leading to specific antitumoral activity in HPV-positive cancer cells and thus represents a new approach for anti-HPV drug development.

Deep Protein Methylation Profiling by Combined Chemical and Immunoaffinity Approaches Reveals Novel PRMT1 Targets

Protein methylation has been implicated in many important biological contexts including signaling, metabolism, and transcriptional control. Despite the importance of this post-translational modification, the global analysis of protein methylation by mass spectrometry-based proteomics has not been extensively studied because of the lack of robust, well-characterized techniques for methyl peptide enrichment. Here, to better investigate protein methylation, we compared two methods for methyl peptide enrichment: immunoaffinity purification (IAP) and high pH strong cation exchange (SCX). Using both methods, we identified 1720 methylation sites on 778 proteins. Comparison of these methods revealed that they are largely orthogonal, suggesting that the usage of both techniques is required to provide a global view of protein methylation. Using both IAP and SCX, we then investigated changes in protein methylation downstream of protein arginine methyltransferase 1 (PRMT1). PRMT1 knockdown resulted in significant changes to 127 arginine methylation sites on 78 proteins. In contrast, only a single lysine methylation site was significantly changed upon PRMT1 knockdown. In PRMT1 knockdown cells, we found 114 MMA sites that were either significantly downregulated or upregulated on proteins enriched for mRNA metabolic processes. PRMT1 knockdown also induced significant changes in both asymmetric dimethyl arginine (ADMA) and symmetric dimethyl arginine (SDMA). Using characteristic neutral loss fragmentation ions, we annotated dimethylarginines as either ADMA or SDMA. Through integrative analysis of methyl forms, we identified 18 high confidence PRMT1 substrates and 12 methylation sites that are scavenged by other non-PRMT1 arginine methyltransferases in the absence of PRMT1 activity. We also identified one methylation site, HNRNPA1 R206, which switched from ADMA to SDMA upon PRMT1 knockdown. Taken together, our results suggest that deep protein methylation profiling by mass spectrometry requires orthogonal enrichment techniques to identify novel PRMT1 methylation targets and highlight the dynamic interplay between methyltransferases in mammalian cells.

Inhibition of Polycomb Repressive Complex 2 activity reduces trimethylation of H3K27 and affects development in Arabidopsis seedlings

BACKGROUND

Polycomb repressive complex 2 (PRC2) is an epigenetic transcriptional repression system, whose catalytic subunit (ENHANCER OF ZESTE HOMOLOG 2, EZH2 in animals) is responsible for trimethylating histone H3 at lysine 27 (H3K27me3). In mammals, gain-of-function mutations as well as overexpression of EZH2 have been associated with several tumors, therefore making this subunit a suitable target for the development of selective inhibitors. Indeed, highly specific small-molecule inhibitors of EZH2 have been reported. In plants, mutations in some PRC2 components lead to embryonic lethality, but no trial with any inhibitor has ever been reported.

RESULTS

We show here that the 1,5-bis (3-bromo-4-methoxyphenyl)penta-1,4-dien-3-one compound (RDS 3434), previously reported as an EZH2 inhibitor in human leukemia cells, is active on the Arabidopsis catalytic subunit of PRC2, since treatment with the drug reduces the total amount of H3K27me3 in a dose-dependent fashion. Consistently, we show that the expression level of two PRC2 targets is significantly increased following treatment with the RDS 3434 compound. Finally, we show that impairment of H3K27 trimethylation in Arabidopsis seeds and seedlings affects both seed germination and root growth.

CONCLUSIONS

Our results provide a useful tool for the plant community in investigating how PRC2 affects transcriptional control in plant development.

Inhibition of anti-viral responses in intestinal epithelial cells by epigenetic modifying drugs is mediated by a reduction in viral pattern recognition receptor expression and activity

Background: Pattern recognition receptors form an essential part of the host defenses against pathogens, in particular in the intestinal epithelium. However, despite their importance relatively little is understood about the regulation of their expression. Increasing evidence suggesting that epigenetic mechanisms such as DNA methylation and histone acetylation have substantial effects on gene expression and regulation. Epigenetic modifying drugs are now used to treat certain cancers but not a lot is known about their effects on the innate immune system. Thus, we set out to examine the role of such drugs in the expression and function of Toll-like receptors. Methods: Using the HCT116 epithelial cell line, we determined the effects of genetic knockout of the DNA methyltransferases enzymes (DNMTs), as well as pharmacological inhibition of the DNMTs and histone deacetylase complexes (HDACs) on TLR responses to their ligands. Results: Our initial results showed that anti-viral responses were affected by changes in the epigenome, with TLR3 responses showing the most dramatic differences. We determined that inhibition of methylation and acetylation inhibited poly I:C induced increases in signaling protein phosphorylation, as well as increases in cytokine mRNA expression and release. We also observed that treatment with epigenetic modifying drugs were leading to large increases in IRF8 expression, a protein that is a known negative regulator of TLR3. When we overexpressed IRF8 in our WT cells we noticed inhibition of poly I:C responses. Conclusion: This research highlighted the potential immunoregulatory role of epigenetic modifying drugs specifically in response to viral stimulation.

BAP1 regulates epigenetic switch from pluripotency to differentiation in developmental lineages giving rise to BAP1-mutant cancers

The BAP1 tumor suppressor is mutated in many human cancers such as uveal melanoma, leading to poor patient outcome. It remains unclear how BAP1 functions in normal biology or how its loss promotes cancer progression. Here, we show that Bap1 is critical for commitment to ectoderm, mesoderm, and neural crest lineages during Xenopus laevis development. Bap1 loss causes transcriptional silencing and failure of H3K27ac to accumulate at promoters of key genes regulating pluripotency-to-commitment transition, similar to findings in uveal melanoma. The Bap1-deficient phenotype can be rescued with human BAP1, by pharmacologic inhibition of histone deacetylase (HDAC) activity or by specific knockdown of Hdac4. Similarly, BAP1-deficient uveal melanoma cells are preferentially vulnerable to HDAC4 depletion. These findings show that Bap1 regulates lineage commitment through H3K27ac-mediated transcriptional activation, at least in part, by modulation of Hdac4, and they provide insights into how BAP1 loss promotes cancer progression.

MTA1 promotes the invasion and migration of oral squamous carcinoma by inducing epithelial-mesenchymal transition via the hedgehog signaling pathway

The metastasis-associated gene 1 (MTA1) has previously been recognized as an oncogene in many tumors, and aberrant MTA1 expression has been related to invasion and migration; however, its role and underlying molecular mechanism in oral squamous carcinoma (OSCC) remain largely unexplored. In this work, we determined the expression of MTA1 in OSCC tissues and cell lines. The effect of MTA1 on metastasis and the role of MTA1 in the epithelial-to-mesenchymal transition (EMT) of OSCC cells were evaluated by assays both in vitro and in vivo. We also identified the key Hedgehog signaling pathway-related protein involved in the MTA1-induced EMT. We found that MTA1 expression was upregulated and positively related to the metastasis in OSCC tissues and cell lines. MTA1 overexpression promoted OSCC invasion, migration, and induced EMT, while its silencing had the opposite effect both in vitro and in vivo. Additionally, our data further revealed the relevant molecular mechanism, Hedgehog(Hh) signaling pathway contributed to the effect of MTA1 on the aggressive phenotypes of OSCC cells.These findings indicate that MTA1 enhances OSCC cells invasion and migration by inducing EMT via the Hedgehog signaling pathway, which suggests MTA1 may be an effective anti-OSCC therapeutic target.

Systemic Delivery of CRISPR/Cas9 Targeting HPV Oncogenes Is Effective at Eliminating Established Tumors

The recent advancements in CRISPR/Cas9 engineering have resulted in the development of more targeted and potentially safer gene therapies. The challenge in the cancer setting is knowing the driver oncogenes responsible, and the translation of these therapies is hindered by effective and safe delivery methods to target organs with minimal systemic toxicities, on-target specificity of gene editing, and demonstrated lack of long-term adverse events. Using a model system based on cervical cancer, which is driven by the ongoing expression of the human papillomavirus E6 and E7 proteins, we show that CRISPR/Cas9 delivered systemically in vivo using PEGylated liposomes results in tumor elimination and complete survival in treated animals. We compared treatment and editing efficiency of two Cas9 variants, wild-type (WT) Cas9 and the highly specific FokI-dCas9, and showed that the latter was not effective. We also explored high-fidelity repair but found that repair was inefficient, occurring in 6%-8% of cells, whereas non-homologous end joining (NHEJ) was highly efficient, occurring in ∼80% of the cells. Finally, we explored the post gene-editing events in tumors and showed that cell death is induced by apoptosis. Overall, our work demonstrates that in vivo CRISPR/Cas editing treatment of preexisting tumors is completely effective despite the large payloads.

Therapeutic Targeting of RNA Splicing Catalysis through Inhibition of Protein Arginine Methylation

Cancer-associated mutations in genes encoding RNA splicing factors (SFs) commonly occur in leukemias, as well as in a variety of solid tumors, and confer dependence on wild-type splicing. These observations have led to clinical efforts to directly inhibit the spliceosome in patients with refractory leukemias. Here, we identify that inhibiting symmetric or asymmetric dimethylation of arginine, mediated by PRMT5 and type I protein arginine methyltransferases (PRMTs), respectively, reduces splicing fidelity and results in preferential killing of SF-mutant leukemias over wild-type counterparts. These data identify genetic subsets of cancer most likely to respond to PRMT inhibition, synergistic effects of combined PRMT5 and type I PRMT inhibition, and a mechanistic basis for the therapeutic efficacy of PRMT inhibition in cancer.

Etv6 activates vegfa expression through positive and negative transcriptional regulatory networks in Xenopus embryos

VEGFA signaling controls physiological and pathological angiogenesis and hematopoiesis. Although many context-dependent signaling pathways downstream of VEGFA have been uncovered, vegfa transcriptional regulation in vivo remains unclear. Here, we show that the ETS transcription factor, Etv6, positively regulates vegfa expression during Xenopus blood stem cell development through multiple transcriptional inputs. In agreement with its established repressive functions, Etv6 directly inhibits expression of the repressor foxo3, to prevent Foxo3 from binding to and repressing the vegfa promoter. Etv6 also directly activates expression of the activator klf4; reflecting a genome-wide paucity in ETS-binding motifs in Etv6 genomic targets, Klf4 then recruits Etv6 to the vegfa promoter to activate its expression. These two mechanisms (double negative gate and feed-forward loop) are classic features of gene regulatory networks specifying cell fates. Thus, Etv6's dual function, as a transcriptional repressor and activator, controls a major signaling pathway involved in endothelial and blood development in vivo.

Abnormal activity of transcription factors gli in high-grade gliomas

Malignant transformation is associated with loss of cell differentiation, anaplasia. Transcription factors gli, required for embryonic development, may be involved in this process. We studied the activity of transcription factors gli in high-grade gliomas and their role in maintenance of stem cell state and glioma cell survival. 20 glioma cell lines and a sample of a normal adult brain tissue were used in the present study. We found the expression of gli target genes, including GLI1 and FOXM1, in all tested glioma cell lines, but not in the normal tissue. Interestingly, the expression of gli target genes in some glioma cell lines was observed together with a high level of their transcriptional repressor, Gli3R. Knockdown of GLI3 in one of these lines resulted in decrease of gli target gene expression. These data suggest that Gli3R does not prevent the gli target genes transcription, and gli3 acts in glioma cells more as an activator, than a repressor of transcription. We observed that gli regulated the expression of such genes, as SOX2 or OCT4 that maintain stem cell state, and TET1, involving in DNA demethylation. Treatment with GANT61 or siRNA against GLI1, GLI2, or GLI3 could result in complete glioma cell death, while cyclopamine had a weaker and line-specific effect on glioma cell survival. Thus, the gli transcription factors are abnormally active in high-grade gliomas, regulate expression of genes, maintaining the stem cell state, and contribute to glioma cell survival.

SUV39H1 Represses the Expression of Cytotoxic T-Lymphocyte Effector Genes to Promote Colon Tumor Immune Evasion

Despite the presence of CTLs in the tumor microenvironment, the majority of immunogenic human colon cancer does not respond to immune checkpoint inhibitor immunotherapy, and microsatellite instable (MSI) tumors are not naturally eliminated. The molecular mechanism underlying the inactivity of tumor-infiltrating CTLs is unknown. We report here that CTLs were present in both MSI and microsatellite stable colon tumors. The expression of the H3K9me3-specific histone methyltransferase SUV39H1 was significantly elevated in human colon carcinoma compared with normal colon tissues. Using a mouse colon carcinoma model, we further determined that tumor-infiltrating CTLs in the colon tumor microenvironment have high expression of SUV39H1. To target SUV39H1 in the tumor microenvironment, a virtual chemical library was screened on the basis of the SET (suppressor of variegation 3-9, enhancer of zeste and trithorax) domain structure of the human SUV39H1 protein. Functional enzymatic activity assays identified a small molecule that inhibits SUV39H1 enzymatic activity. On the basis of the structure of this small molecule, we modified it and chemically synthesized a small molecule, termed F5446, which has an EC₅₀ of 0.496 μmol/L for SUV39H1 enzymatic activity. H3K9me3 was enriched in the promoters of GZMB, PRF1, FASLG, and IFNG in quiescent T cells. F5446 inhibited H3K9me3, thereby upregulating expression of these effectors in tumor-infiltrating CTLs and suppressing colon carcinoma growth in a CD8⁺ CTL-dependent manner in vivo Our data indicate that SUV39H1 represses CTL effector gene expression and, in doing so, confers colon cancer immune escape.

HDAC8 inhibition ameliorates pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fibroproliferative lung disease, and fibroblast-myofibroblast differentiation (FMD) is thought to be a key event in the pathogenesis of IPF. Histone deacetylase-8 (HDAC8) has been shown to associate with α-smooth muscle actin (α-SMA; a marker of FMD) and regulates cell contractility in vascular smooth muscle cells. However, the role of HDAC8 in FMD or pulmonary fibrosis has never been reported. This study investigated the role of HDAC8 in pulmonary fibrosis with a focus on FMD. We observed that HDAC8 expression was increased in IPF lung tissue as well as transforming growth factor (TGF)β1-treated normal human lung fibroblasts (NHLFs). Immunoprecipitation experiments revealed that HDAC8 was associated with α-SMA in TGFβ1-treated NHLFs. HDAC8 inhibition with NCC170 (HDAC8-selective inhibitor) repressed TGFβ1-induced fibroblast contraction and α-SMA protein expression in NHLFs cultured in collagen gels. HDAC8 inhibition with HDAC8 siRNA also repressed TGFβ1-induced expression of profibrotic molecules such as fibronectin and increased expression of antifibrotic molecules such as peroxisome proliferator-activated receptor-γ (PPARγ). Chromatin immunoprecipitation quantitative PCR using an antibody against H3K27ac (histone H3 acetylated at lysine 27; a known HDAC8 substrate and a marker for active enhancers) suggested that HDAC8 inhibition with NCC170 ameliorated TGFβ1-induced loss of H3K27ac at the PPARγ gene enhancer. Furthermore, NCC170 treatment significantly decreased fibrosis measured by Ashcroft score as well as expression of type 1 collagen and fibronectin in bleomycin-treated mouse lungs. These data suggest that HDAC8 contributes to pulmonary fibrosis and that there is a therapeutic potential for HDAC8 inhibitors to treat IPF as well as other fibrotic lung diseases.

In Vitro Anticancer Properties of Table Grape Powder Extract (GPE) in Prostate Cancer

Although the link between diet and cancer is complex, epidemiological data confirm that diet is a risk factor for prostate cancer and indicate a reduced prostate cancer incidence associated with a diet rich in vegetables and fruits. Because of the known protective effect of grape seed extract (GSE) against prostate cancer, we evaluated the effects of grape powder extract (GPE) on cell viability, proliferation, and metastatic capability. Importantly, we explored the possible novel mechanism of GPE through metastasis-associated protein 1 (MTA1) downregulation in prostate cancer, since our previous studies indicated resveratrol (Res)- and pterostilbene (Pter)-induced MTA1-mediated anticancer activities in prostate cancer. We found that GPE inhibited the cell viability and growth of prostate cancer cells only at high 100 μg/mL concentrations. However, at low 1.5⁻15 μg/mL concentrations, GPE significantly reduced the colony formation and wound healing capabilities of both DU145 and PC3M cells. Moreover, we found that GPE inhibited MTA1 in a dose-dependent manner in these cells, albeit with considerably less potency than Res and Pter. These results indicate that stilbenes such as Res and Pter specifically and potently inhibit MTA1 and MTA1-associated proteins compared to GPE, which contains low concentrations of Res and mainly consists of other flavonoids and anthocyanidins. Our findings support continued interest in GPE as a chemopreventive and anti-cancer agent against prostate cancer but also emphasize the unique and specific properties of stilbenes on MTA1-mediated anticancer effects on prostate cancer.