Synthesis of a selective HDAC6 inhibitor active in neuroblasts.

In recent years, the role of HDAC6 in neurodegeneration has been partially elucidated, which led some authors to propose HDAC6 inhibitors as a therapeutic strategy to treat neurodegenerative diseases. In an effort to develop a selective HDAC6 inhibitor which can cross the blood brain barrier (BBB), a modified hydroxamate derivative (compound 3) was designed and synthetized. This compound was predicted to have potential for BBB penetration based on in silico and in vitro evaluation of passive permeability. When tested for its HDAC inhibitory activity, the IC50 value of compound 3 towards HDAC6 was in the nM range in both enzymatic and cell-based assays. Compound 3 showed a cell-based selectivity profile close to that of tubastatin A in SH-SY5Y human neuroblastoma cells, and a good BBB permeability profile.

Cross metathesis with hydroxamate and benzamide BOC-protected alkenes to access HDAC inhibitors and their biological evaluation highlighted intrinsic activity of BOC-protected dihydroxamates.

Conditions for the metathesis of alkenes in the convergent synthesis of HDAC inhibitors have been improved by continuous catalyst flow injection in the reaction media. Intermediate and target compounds obtained were tested for their ability to induce HDAC inhibition and tubulin acetylation, revealing the key role of the tert-butyloxycarbonyl (BOC) group for more HDAC6 selectivity. Molecular modelling added rationale for this BOC effect.

Relationship between genome and epigenome--challenges and requirements for future research.

Understanding the links between genetic, epigenetic and non-genetic factors throughout the lifespan and across generations and their role in disease susceptibility and disease progression offer entirely new avenues and solutions to major problems in our society. To overcome the numerous challenges, we have come up with nine major conclusions to set the vision for future policies and research agendas at the European level.

Current and upcoming approaches to exploit the reversibility of epigenetic mutations in breast cancer.

DNA methylation and histone modifications are important epigenetic modifications associated with gene (dys)regulation. The epigenetic modifications are balanced by epigenetic enzymes, so-called writers and erasers, such as DNA (de)methylases and histone (de)acetylases. Aberrant epigenetic alterations have been associated with various diseases, including breast cancer. Since aberrant epigenetic modifications are potentially reversible, they might represent targets for breast cancer therapy. Indeed, several drugs have been designed to inhibit epigenetic enzymes (epi-drugs), thereby reversing epigenetic modifications. US Food and Drug Administration approval has been obtained for some epi-drugs for hematological malignancies. However, these drugs have had very modest anti-tumor efficacy in phase I and II clinical trials in breast cancer patients as monotherapy. Therefore, current clinical trials focus on the combination of epi-drugs with other therapies to enhance or restore the sensitivity to such therapies. This approach has yielded some promising results in early phase II trials. The disadvantage of epi-drugs, however, is genome-wide effects, which may cause unwanted upregulation of, for example, pro-metastatic genes. Development of gene-targeted epigenetic modifications (epigenetic editing) in breast cancer can provide a novel approach to prevent such unwanted events. In this context, identification of crucial epigenetic modifications regulating key genes in breast cancer is of critical importance. In this review, we first describe aberrant DNA methylation and histone modifications as two important classes of epigenetic mutations in breast cancer. Then we focus on the preclinical and clinical epigenetic-based therapies currently being explored for breast cancer. Finally, we describe epigenetic editing as a promising new approach for possible applications towards more targeted breast cancer treatment.

Cell differentiation along multiple pathways accompanied by changes in histone acetylation status.

Post-translational modification of histones is fundamental to the regulation of basic nuclear processes and subsequent cellular events, including differentiation. In this study, we analyzed acetylated forms of histones H2A, H2B, and H4 during induced differentiation in mouse (mESCs) and human (hESCs) embryonic stem cells and during induced enterocytic differentiation of colon cancer cells in vitro. Endoderm-like differentiation of mESCs induced by retinoic acid and enterocytic differentiation induced by histone deacetylase inhibitor sodium butyrate were accompanied by increased mono-, di-, and tri-acetylation of histone H2B and a pronounced increase in di- and tri-acetylation of histone H4. In enterocytes, mono-acetylation of histone H2A also increased and tetra-acetylation of histone H4 appeared only after induction of this differentiation pathway. During differentiation of hESCs, we observed increased mono-acetylation and decreased tri-acetylation of H2B. Mono-, di-, and tri-acetylation of H4 were reduced, manifested by a significant increase in nonacetylated H4 histones. Levels of acetylated histones increased during induced differentiation in mESCs and during histone deacetylase (HDAC) inhibitor-induced enterocytic differentiation, whereas differentiation of human ESCs was associated with reduced acetylation of histones H2B and H4.

Aurones as histone deacetylase inhibitors: identification of key features.

In this study, a total of 22 flavonoids were tested for their HDAC inhibitory activity using fluorimetric and BRET-based assays. Four aurones were found to be active in both assays and showed IC50 values below 20 µM in the enzymatic assay. Molecular modelling revealed that the presence of hydroxyl groups was responsible for good compound orientation within the isoenzyme catalytic site and zinc chelation.

Quinazolinecarboline alkaloid evodiamine as scaffold for targeting topoisomerase I and sirtuins.

This paper reports the synthesis of a series of evodiamine derivatives. We assayed the ability to inhibit cell growth on three human tumour cell lines (H460, MCF-7 and HepG2) and we evaluated the capacity to interfere with the catalytic activity of topoisomerase I both by the relaxation assay and the occurrence of the cleavable complex. Moreover, whose effect on sirtuins 1, 2 and 3 was investigated. Finally, molecular docking analyses were performed in an attempt to rationalize the biological results.

Signalling with retinoids in the human lung: validation of new tools for the expression study of retinoid receptors.

BACKGROUND: Retinoid Receptors are involved in development and cell homeostasis. Alterations of their expressions have been observed in lung cancer. However, retinoid chemoprevention trials in populations at risk to develop such tumors have failed. Therefore, the pertinence of new clinical trials using second generation retinoid requires prior better understanding of retinoid signalling. This is our aim when validating extensively research tools, focused on Retinoic Acid Receptor beta, whose major role in lung cancer is documented. METHODS: Biocomputing was used to assess the genomic organization of RAR beta. Its putative RAR-beta1' promoter features were investigated experimentally. Specific measures realized, with qRT-PCR Syber Green assays and a triplex of Taqman probes, were extensively validated to establish Retinoid Receptors mRNAs reference values for in vivo normal human bronchial cells, lung tumors and cell lines. Finally, a pan-RAR-beta antibody was generated and extensively validated by western-blot and immunoprecipitation. RESULTS: No promoter-like activity was found for RAR-beta1'. RAR-beta2 mRNAs increase signs the normal differentiation of the human bronchial epithelium while a decrease is observed in most lung cancer cell lines. Accordingly, it is also, along with RXR beta, down-regulated in lung tumors. When using nuclear extracts of BEAS-2B and normal lung cells, only the RAR-beta2 long protein isoform was recognized by our antibody. CONCLUSION: Rigorous samples processing and extensive biocomputing, were the key factors for this study. mRNA reference values and validated tools can now be used to advance researches on retinoid signalling in the lung.

Imidazo[2,1-b]benzothiazol Derivatives as Potential Allosteric Inhibitors of the Glucocorticoid Receptor.

Glucocorticoid receptor (GCR) transactivation reporter gene assays were used as an initial high-throughput screening on a diversified library of 1200 compounds for their evaluation as GCR antagonists. A class of imidazo[2,1-b]benzothiazole and imidazo[2,1-b]benzoimidazole derivatives were identified for their ability to modulate GCR transactivation and anti-inflammatory transrepression effects utilizing GCR and NF-κB specific reporter gene assays. Modeling studies on the crystallographic structure of the GCR ligand binding domain provided three new analogues bearing the tetrahydroimidazo[2,1-b]benzothiazole scaffold able to antagonize the GCR in the presence of dexamethasone (DEX) and also defined their putative binding into the GCR structure. Both mRNA level measures of GCR itself and its target gene GILZ, on cells treated with the new analogues, showed a GCR transactivation inhibition, thus suggesting a potential allosteric inhibition of the GCR.

The retinoblastoma gene and its product are targeted by ICBP90: a key mechanism in the G1/S transition during the cell cycle.

The retinoblastoma protein (pRB) is encoded by the RB1 gene whose promoter contains several putative binding sites for ICBP90 (Inverted CCAAT box Binding Protein of 90 kDa), a transcriptional regulator of the topoisomerase IIalpha gene. ICBP90 has two consensus binding sites for pRB in its primary sequence. Here, we show that pRB and ICBP90 co-immunoprecipitate in cell extracts of proliferating human lung fibroblasts and of proliferating or confluent Jurkat cells. GST pull-down assays and immunocytochemistry, after cell synchronization in late G1 phase, confirmed this interaction. Overexpression of ICBP90 induces downregulation of pRB expression in lung fibroblasts as a result of mRNA decrease. DNA chromatin immunoprecipitation experiment shows that ICBP90 binds to the RB1 gene promoter under its methylated status. Overexpression of ICBP90 increases the S and G2/M phase cell fractions of serum-starved lung fibroblasts as assessed by flow cytometry analysis and increases topoisomerase IIalpha expression. Together, these results show that ICBP90 regulates pRB at the protein and gene transcription levels, thus favoring the entry into the S phase of the cells. We propose that ICBP90 overexpression, found in cancer cells, is involved in the altered checkpoint controls occurring in cancerogenesis.

Smoking cessation--but not smoking reduction--improves the annual decline in FEV1 in occupationally exposed workers.

INTRODUCTION: Individuals exposed both to cigarette smoke and respiratory pollutants at work incur a greater risk of development of airway hyperresponsiveness (AHR) and accelerated decline in forced expiratory volume in 1 s (FEV1) than that incurred by subjects undergoing each exposure separately. We examined whether smoking cessation or smoking reduction improves AHR and thereby slows down the decline in FEV1 in occupationally exposed workers. METHODS: We examined 165 workers (137 males and 28 females) participating in a smoking cessation programme. Nicotine tablets were used for smoking cessation or smoking reduction. Respiratory symptoms were assessed by questionnaire, FEV1 by spirometry and AHR by methacholine challenge test. At 1 year, subjects were classified into quitters, reducers, or continuing smokers. RESULTS: Sixty-seven subjects completed the study (32 quitters; 17 reducers; 18 continuing smokers). Respiratory symptoms improved markedly in quitters (P<0.001 for all comparisons) and less so in reducers (P values between 0.163 and 0.027). At 1 year, FEV1 had slightly but significantly improved in quitters (P=0.006 vs. smokers; P=0.038 vs. reducers) and markedly deteriorated in reducers and continuing smokers. Concurrent, 1-year change in AHR did not differ significantly among the groups. CONCLUSION: In occupationally exposed workers, stopping smoking markedly improved respiratory symptoms and, in males, slowed the annual decline in FEV1. Smoking reduction resulted in smaller improvements in symptoms but deterioration in FEV1. These findings were independent of AHR. While smoking cessation should remain the ultimate goal in workplace cessation programmes more studies are necessary to better ascertain the benefits of smoking reduction.

Tandem virtual screening targeting the SRA domain of UHRF1 identifies a novel chemical tool modulating DNA methylation.

Ubiquitin-like protein UHRF1 that contains PHD and RING finger domain 1 is a key epigenetic protein enabling maintenance of the DNA methylation status through replication. A tandem virtual screening approach was implemented for identifying small molecules able to bind the 5-methylcytosine pocket of UHRF1 and inhibit its functionality. The NCI/DTP small molecules Repository was screened in silico by a combined protocol implementing structure-based and ligand-based methodologies. Consensus ranking was utilized to select a set of 27 top-ranked compounds that were subsequently evaluated experimentally in a stepwise manner for their ability to demethylate DNA in cellulo using PCR-MS and HPLC-MS/MS. The most active molecules were further assessed in a cell-based setting by the Proximity Ligation In Situ Assay and the ApoTome technology. Both evaluations confirmed that the DNMT1/UHRF1 interactions were significantly reduced after 4 h of incubation of U251 glioma cells with the most potent compound NSC232003, showing a 50% interaction inhibition at 15 µM as well as induction of global DNA cytosine demethylation as measured by ELISA. This is the first report of a chemical tool that targets UHRF1 and modulates DNA methylation in a cell context by potentially disrupting DNMT1/UHRF1 interactions. Compound NSC232003, a uracil derivative freely available by the NCI/DTP Repository, provides a versatile lead for developing highly potent and cell-permeable UHRF1 inhibitors that will enable dissection of DNA methylation inheritance.

Natural Products and Cancer Stem Cells.

The development of modern technologies casts a new light on the natural products as an invaluable source of lead compounds that could guide drug discovery. Cancer stem cells are a subpopulation of cancer cells with a high clonogenic capacity and the ability to reform the parental tumours upon transplantation. They have been proposed to drive tumorigenesis and metastases. In this review, we present the ability of forty-nine different natural products to influence the biology of cancer stem cells.

Boehmeriasin A as new lead compound for the inhibition of topoisomerases and SIRT2.

Two synthetic approaches to boehmeriasin A are described. A gram scale racemic preparation is accompanied by an efficient preparation of both the pure enantiomers using the conformationally stable 2-piperidin-2-yl acetaldehyde as starting material. The anti-proliferative activity in three cancer cell lines (CEM, HeLa and L1210) and two endothelial cell lines (HMEC-1, BAEC) indicates promising activity at the nanomolar range. Topoisomerases and SIRT2 are identified as biological targets and the experimental data has been supported by docking studies.

High DNA damage by benzo[a]pyrene 7,8-diol-9,10-epoxide in bronchial epithelial cells from patients with lung cancer: comparison with lung parenchyma.

In the present study, the level of benzo[a]pyrene 7,8-diol-9,10-epoxide-N(2)-deoxyguanosine (BPDE-N(2)-dG) in normal bronchial epithelial cells from non-cancerous bronchus of 22 lung cancer subjects was evaluated and compared to the lung parenchyma. We found very high formation of BPDE-N(2)-dG adduct in samples corresponding to a pure preparation of bronchial epithelial cells with 4-fold interindividual differences in the DNA adduct levels in the range of 36.5-175.4 BPDE-N(2)-dG adducts/10(8) nucleotides in smokers (mean: 84.7+/-38.4; n = 13) and 3-fold differences in the range of 19.7-62.4 in non-smokers (mean: 37.6+/-22.2; n = 3). DNA isolated from the bronchial tissue consisting of bronchial lining epithelium with adjacent lamina propria showed significantly lower BPDE-N(2)-dG formation (P < 0.001) in the range of 0.4-4.2 BPDE-N(2)-dG adducts/10(8) nucleotides (mean: 1.8+/-0.56; n = 6). This difference is clearly related to the procedure used to prepare the bronchial tissue samples leading to the presence of different types of cells. Eight samples from the normal parenchyma did not show measurable adducts, the other 14 samples showed 50-fold variation (mean: 1.7+/-1.5; range 0.1-5.2 adducts/10(8) nucleotides; n = 14). There were considerably higher adduct levels in pure bronchial epithelial cells than in parenchymal tissue (75.8+/-38.8 vs 0.9+/-1.5 adducts/10(8) nucleotides) (P < 0.0002) BPDE-N(2)-dG adduct concentrate almost exclusively in bronchial epithelial cells. The adduct values obtained in bronchial epithelial cells could be considered as 'critical' for the initiation of human lung cancer. The high formation of BPDE-N(2)-dG adducts in bronchial epithelial cells and investigations showing that the profile of mutations induced by BPDE in these cells is similar to that seen in the p53 gene isolated from human lung tumors implicates benzo[a]pyrene as important carcinogen in tobacco-induced lung cancer in human beings.

Delivery of epidrugs.

Inhibitors of epigenetic targets have entered clinical trials with some success, in particular for combined therapies. Like many other chemotherapeutics these new classes of molecules have dose-limiting toxicities and highly active metabolism in vivo resulting in lower efficacy than expected. This review presents drug delivery strategies proposed to prolong epigenetic inhibitor effects while reducing toxicities and metabolic clearance. Inspired from the work done in cancer-targeted strategies, prodrugs and nanoparticle-based drug delivery systems are discussed in a comprehensive way, detailing the chemical and physiological principles of the selected releasing method and, when available, how epigenetic chemistry can be exploited.

Basic nuclear processes affected by histone acetyltransferases and histone deacetylase inhibitors.

AIM: The optimal balance between histone acetylation and deacetylation is important for proper gene function. Therefore, we addressed how inhibitors of histone-modifying enzymes can modulate nuclear events, including replication, transcription, splicing and DNA repair. MATERIALS & METHODS: Changes in cell signaling pathways upon treatment with histone acetyltransferases and/or histone deacetylase inhibitors were studied by cDNA microarrays and western blots. RESULTS: We analyzed the effects of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) and the histone acetylase inhibitor MG149. SAHA altered the expression of factors involved in DNA replication complexes, basal transcription and the spliceosome pathway. DNA repair-related genes, including Rad51, Rad54 and BRCA2, were significantly downregulated by SAHA. However, MG149 had no effect on the investigated nuclear processes, with the exception of the spliceosome network and Sestrins, involved in DNA repair. CONCLUSION: Based on our results, we propose that the studied epigenetic drugs have the distinct potential to affect specific cell signaling pathways depending on their respective molecular targets.

Retinoid acid receptor expression is helpful to distinguish between adenoma and well-differentiated carcinoma in the thyroid.

Retinoid receptors (RRs) play a key role in cell proliferation and differentiation. We characterized the expression of RA receptors and retinoid X receptors (RARs and RXRs) in a series of 111 thyroid tumors and investigated the mechanisms responsible for their deregulation: hypermethylation of the RARB2 promoter, loss of heterozygosity (LOH) in the regions of RARB and RXRA, and altered expression of CRBP1 and enzymes involved in RA biosynthesis (RDH10 and RALDH2). Expression of RALDH2 and RDH10 was conserved in 100 % of adenomas and in 90 and 98 %, respectively, of carcinomas, whereas staining for CRBP1 was decreased in 9 % of FAs and 28 % of carcinomas, mainly anaplastic carcinomas (55 %). We found an abnormal expression of RARA, RARB, RXRA, and RXRB in 67, 69, 66, and 73 %, respectively, of thyroid carcinomas (n = 78) and in 9, 9, 9, and 33 % of follicular adenomas (n = 33) (p < 0.001). An abnormal staining pattern of at least two of these markers had 90 % sensitivity and 91 % specificity for a diagnosis of malignancy. Promoter hypermethylation of RARB2 was observed in some anaplastic carcinomas (14 %). LOH was found to be common at the RARB locus (3p24-3p25) and the RXRA locus (9q34), respectively, in 44 and 55 % of carcinomas and in 27 and 43 % of adenomas. In conclusion, immunohistochemical staining for RARs and RXRs may help in the differential diagnosis between well-differentiated carcinoma and follicular adenoma. Further investigation should be carried out to determine whether the characterization of RR expression might identify patients who could benefit from therapy with RA derivatives.

Interpreting clinical assays for histone deacetylase inhibitors.

As opposed to genetics, dealing with gene expressions by direct DNA sequence modifications, the term epigenetics applies to all the external influences that target the chromatin structure of cells with impact on gene expression unrelated to the sequence coding of DNA itself. In normal cells, epigenetics modulates gene expression through all development steps. When "imprinted" early by the environment, epigenetic changes influence the organism at an early stage and can be transmitted to the progeny. Together with DNA sequence alterations, DNA aberrant cytosine methylation and microRNA deregulation, epigenetic modifications participate in the malignant transformation of cells. Their reversible nature has led to the emergence of the promising field of epigenetic therapy. The efforts made to inhibit in particular the epigenetic enzyme family called histone deacetylases (HDACs) are described. HDAC inhibitors (HDACi) have been proposed as a viable clinical therapeutic approach for the treatment of leukemia and solid tumors, but also to a lesser degree for noncancerous diseases. Three epigenetic drugs are already arriving at the patient's bedside, and more than 100 clinical assays for HDACi are registered on the National Cancer Institute website. They explore the eventual additive benefits of combined therapies. In the context of the pleiotropic effects of HDAC isoforms, more specific HDACi and more informative screening tests are being developed for the benefit of the patients.

An adult tissue-specific stem cell molecular phenotype is activated in epithelial cancer stem cells and correlated to patient outcome.

Recent studies have shown that embryonic stem cell-like molecular phenotypes are commonly activated in human epithelial primary tumors and are linked to adverse patient prognosis.(1,2) However it remains unclear whether these correlations to outcome are linked to the differentiation status of the human primary tumors(1) or represent molecular reminiscences of epithelial cancer stem cells.(2) In addition, while it has been demonstrated that leukemic cancer stem cells re-acquire an embryonic stem cell-like phenotype,(3,4) the molecular basis of stem cell function in epithelial cancer stem cells has not been investigated. Here we show that a normal adult tissue-specific stem cell molecular phenotype is commonly activated in epithelial cancer stem cells and for the first time provide evidence that enrichment in cancer stem cells-specific molecular signatures are correlated to highly aggressive tumor phenotypes in human epithelial cancers.