Abstract: HDAC inhibitors (HDACi) are gaining increasing attention in the treatment of cancer, particularly in view of their therapeutic effectiveness and assumed mild toxicity profile. While numerous studies have investigated the role of HDACi in tumor cells, little is known about their effects on normal tissue cells. We studied the effect of suberoylanilide hydroxamic acid (SAHA), MS275, sodium-butyrate and valproic acid in healthy human fibroblasts and found HDACi-treatment to go along with increased radiosensitivity and reduced DSB repair capacity. In view of the potential genotoxic effects of HDACi-treatment, particularly when being administered long-term for chronic disease or when given to children, to women of childbearing age or their partners or in combination with radiotherapy, an extensive education of patients and prescribing physicians as well as a stringent definition of clinical indications is urgently required.
Abstract: Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase, which belongs to the silent information regulator 2 (Sir2) family of histone deacetylases (HDACs). The yeast Sir2 protein and its mammalian derivatives play a central role in epigenetic gene silencing, DNA repair and recombination, the cell cycle, microtubule organization, and in the regulation of aging. We isolated and characterized the murine Sirt1 genomic sequence, which spans 19,910 bp and has one single genomic locus. Determination of the exon-intron splice junctions established that SIRT1 is encoded by 9 exons ranging in size from 80 bp (exon 6) to 1,927 bp (exon 9). Characterization of the 5' flanking genomic region, which precedes the Sirt1 open reading frame, revealed a number of NFkappaB and GATA transcription factor binding sites in addition to a 393-bp CpG island. The 3,882-bp murine Sirt1 transcript has an open reading frame of 2,211 bp and encodes a 737 aa protein with a predicted molecular weight of 80.4 kDa and an isoelectric point of 4.60. Next to this transcript, a shorter, 3,765 bp splice variant with an open reading frame of 2,094 bp, that lacks exon 2 and encodes a 698 aa protein with a predicted molecular weight of 76.0 kDa and an isoelectric point of 4.62 has been reported. Fluorescence in situ hybridization analysis identified a single genomic locus for the murine Sirt1 gene on chromosome 10 B4 and is neighbored by the Herc4 and Dnajc12 genes.
Abstract: The sirtuins (SIRT1-7), also being referred to as class III HDACs, exert NAD-dependent deacetylase and/or ADP-ribosyltransferase activities in various cellular compartments including the cell nucleus, the cytoplasm and the mitochondria. The sirtuins play a central role in epigenetic gene silencing, DNA repair and recombination, cell-cycle, microtubule organization, and in the regulation of aging. SIRT4 is a mitochondrial protein that lacks deacetylase activities but efficiently works as an ADP-ribosyltransferase. We have isolated and characterized the murine Sirt4 genomic sequence, which spans a region of 12kb and which has one single genomic locus. Determination of the exon-intron splice junctions established that SIRT4 is encoded by 6 exons. The 1648bp murine Sirt4 transcript encodes a 418 aa protein with a predictive molecular weight of 47.3kDa. Fluorescence in situ hybridization analysis identified a single genomic locus for murine Sirt4 gene on chromosome 5F and is neighbored by the PLA2G1B and PXN genes.
Abstract: Previous analyses of the sirtuin family of histone deacetylases and its most prominent member SIRT1 have focused primarily on the identification of cellular targets exploring the underlying molecular mechanisms of its implicated function in the control of metabolic homeostasis, differentiation, apoptosis and cell survival. So far, little is known about the regulation of SIRT1 itself. In the study presented herein, we assigned the main region of SIRT1 in vivo phosphorylation to amino acids 643-691 of the unique carboxy-terminal domain. Furthermore, we demonstrate that SIRT1 is a substrate for protein kinase CK2 both in vitro and in vivo. Both, deletion construct analyses and serine-to-alanine mutations identified SIRT1 Ser-659 and Ser-661 as major CK2 phosphorylation sites that are phosphorylated in vivo as well.
Abstract: Abstract Chromosomal instability (CIN), defined by an elevated frequency of the occurrence of novel chromosomal aberrations, is strongly implicated in the generation of aneuploidy, one of the hallmarks of human cancers. As for aneuploidy itself, the role of CIN in the evolution and progression of malignancy is a matter still open to debate. We investigated numerical as well as structural CIN in primary CD34-positive cells by determining the cell-to-cell variability of the chromosome content using fluorescence-in situ-hybridization (FISH). Thereby, CIN was measured in 65 patients with myelodysplastic syndromes (MDS), acute myeloid leukemia (AML) and control subjects. Among MDS patients, a subgroup with elevated levels of CIN was identified. At a median follow up of 17.2 months, all patients within this "high CIN" subgroup had died or progressed to AML, while 80% of MDS patients with normal CIN levels had stable disease (p<0.001). Notably, there was no statistically significant difference between "normal CIN" and "high CIN" MDS patients regarding established risk factors. Hence, elevated CIN levels were associated with poor outcome, and our method provided additional prognostic information beyond conventional cytogenetics. Furthermore, in all three MDS patients for whom serial measurements were available, development of AML was preceded by increasing CIN levels. In conclusion, elevated CIN levels may be valuable as an early indicator of poor prognosis in MDS, hence corroborating the concept of CIN as a driving force in tumor progression.
Abstract: The sirtuin 1 protein (SIRT1) is a member of the class III NAD+-dependent histone deacetylases, which are also referred to as the 'sirtuins'. The sirtuins and silent information regulator 1 (SIRT1) in particular, are known to play a role in the response to DNA damage, metabolism, longevity and carcinogenesis. SIRT1 regulates different cellular processes such as proliferation, differentiation and apoptosis through deacetylation of important regulatory proteins such as p53, FOXO3a and NFkappaB. A number of different modifiers of SIRT1 expression and activity have been discovered and even food and cosmetic additives (e.g. resveratrol and dihydrocoumarin) have been suggested to either activate or inhibit the activity of human SIRT1. We screened a panel of 18 different drugs which are frequently used in everyday clinical practice with regard to their influence on cell survival and SIRT1 expression in freshly isolated peripheral blood mononuclear cells (PBMCs) from young and healthy volunteers. In this context, we identified L-thyroxin, insulin and sodium nitroprusside to be potent activators of human SIRT1 expression. In addition, treatment of PBMCs with sodium nitroprusside was associated with a significant cellular lifespan extension, while L-thyroxin and insulin were unable to prolong lifespan, suggesting that isolated upregulation of SIRT1 is in fact insufficient to promote longevity. These findings have an important impact on the long-term use of a number of frequently used clinical agents in the treatment of chronic disease with respect to aging and carcinogenesis.
Abstract: Chronic lymphocytic leukemia (CLL) is one of the most common leukemias in adults in the developed world. Despite significant advances in the treatment of cancer, CLL remains incurable. The main feature of the disease is the generation of circulating B-cells with prolonged survival caused by aberrant apoptosis. In this study, we observe that valproic acid (VPA), a well-established histone deacetylase (HDAC) inhibitor, mediates apoptosis in CLL cells ex vivo through caspase activation via both the extrinsic and the intrinsic apoptosis pathways, as indicated by the activation of the caspase proteins 8 and 9, and cleavage of the proapoptotic protein BID. The Bcl-2/Bax ratio was decreased as a consequence of decreased bcl-2 mRNA levels in response to treatment with VPA. With the results presented in this study, we have identified the HDAC inhibitor VPA as restoring the apoptotic pathways in CLL cells and thus their ability to undergo apoptosis.
Abstract: The alpha4beta1 integrin very late activation antigen-4 (VLA-4) is an alpha4 (CD49d)/beta1 (CD29) heterodimer. It plays a key role in the adhesion of both hematopoietic progenitor cells and leukemic blast cells to bone marrow stromal cells which express the vascular cell adhesion molecule-1 (VCAM-1) or produce fibronectin. VLA-4 expression has been associated with bone-marrow minimal residual disease, which causes relapse after chemotherapy in patients with acute myelogenous leukemia. Conversely, the absence of VLA-4 reduces bone marrow retention of both hematopoietic progenitor and leukemic blast cells. We report on the downregulation of VLA-4/CD49d for various acute myelogenous leukemia cells lines, on primary cells from patients with acute myelogenous leukemia, and on hematopoietic stem cells and peripheral blood mononuclear cells from healthy donors on treatment with the histone deacetylase inhibitors suberoylanilide hydroxamic acid and valproic acid, which is associated with decreased adhesion to mesenchymal stromal cells. These findings suggest that HDAC-inhibitor treatment may on the one hand impair stem cell homing, while on the other it may improve peripheral blood stem cell mobilization and significantly help to reduce minimal residual disease from acute myelogenous leukemia.
Abstract: HIV-1 two-exon transactivator protein (Tat) is a 101-aa protein. We investigated the possible contribution of the extreme C terminus of HIV-1 Tat to maximize nuclear transcription factor NF-kappaB activation, long terminal repeat (LTR) transactivation, and viral replication in T cells. C-terminal deletion and substitution mutants made with the infectious clone HIV-89.6 were assayed for their ability to transactivate NF-kappaB-secreted alkaline phosphatase and HIV-1 LTR-luciferase reporter constructs for low concentrations of Tat. A mutant infectious clone of HIV-89.6 engineered by introducing a stop codon at aa 72 in the Tat open-reading frame (HIVDeltatatexon2) replicated at a significantly lower rate than the wild-type HIV-89.6 in phytohemagglutinin-A/IL-2-stimulated primary peripheral blood lymphocytes. Altogether, our results suggest a critical role for the glutamic acids at positions 92, 94, and 96 or lysines at positions 88, 89, and 90, present in the second encoding Tat exon in activating NF-kappaB, transactivating the HIV-1 LTR and enhancing HIV-1 replication in T cells.
Abstract: The human immunodeficiency virus (HIV) Nef protein is myristoylated and plays a critical role in AIDS pathogenesis by enhancing viral replication, survival of the virus within infected cells and by facilitating its spread in vivo. We observed that, in the promonocytic cell line U937, myristoylated exogenous Nef protein activates NF-kappaB and AP-1, whereas unmyristoylated exogenous Nef protein does not. Using methyl-beta-cyclodextrin (MbetaC) treatment, we observed that the activation of NF-kappaB and AP-1 by exogenous Nef protein is mediated primarily via lipid rafts both in U937 cells and in primary human macrophages. In agreement with this observation, exogenous Nef protein colocalized with GM1 ganglioside, a major component of lipid rafts, in U937 cells as detected by confocal microscopy. Since tumor necrosis factor alpha (TNFalpha) activates NF-kappaB and AP-1, we investigated the role of exogenous Nef protein in TNFalpha-stimulated U937 cells and primary macrophages. We observed that exogenous Nef and TNFalpha synergistically activate NF-kappaB and AP-1 in U937 cells and primary macrophages resulting in enhanced stimulation of the HIV-1 long terminal repeat (LTR), and subsequently in enhanced viral replication in both chronically infected promonocytic U1 cells and acutely HIV-1-infected primary macrophages. Both enhanced LTR stimulation and viral replication following treatment with exogenous Nef and TNFalpha were mediated via lipid rafts. Therefore, our results indicate that exogenous Nef protein and enhanced TNFalpha production detected in HIV-infected subjects could synergize to fuel the progression of the disease via lipid raft-dependent stimulation of the HIV-1 provirus present in such cellular reservoirs as mononuclear phagocytes.
Abstract: Currently, no standard treatment is available for elderly patients with de novo/secondary acute myeloid leukemia (AML) who are not eligible for intensive chemotherapy. New, less aggressive therapies are therefore needed. Histone deacetylase inhibitors (HDACi) are known to reduce proliferation and induce differentiation in hematological malignancies. With all-trans retinoic acid (ATRA) these effects have been reported to be even enhanced. Valproic acid (VPA) is an HDACi and has been known as anti-epileptic agent for many years. We treated 21 patients with de novo/secondary AML and 1 patient with myelodysplastic syndrome with ATRA (45 mg/m(2)/day in 2 doses, 14 days, q29 days) and VPA (150 mg/day 1 week, then 300 mg/day, continuously). Treatment was tolerated well with moderate side effects. 4 patients revealed hematological improvement and another 4 patients experienced a reduction in transfusion dependency. The overall response rate was 27%. Our study is presented together with an overview of the literature on the topic.
Abstract: Aberrant DNA methylation patterns play an important role in the pathogenesis of hematologic malignancies. The DNA methyltransferase inhibitors azacytidine and decitabine have shown significant clinical benefits in the treatment of myelodysplastic syndrome (MDS), but their precise mode of action remains to be established. Both drugs have been shown the ability to deplete DNA methyltransferase enzymes and to induce DNA demethylation and epigenetic reprogramming in vitro. However, drug-induced methylation changes have remained poorly characterized in patients and therapy-related models. We have now analyzed azacytidine-induced demethylation responses in myeloid leukemia cell lines. These cells showed remarkable differences in the drug-induced depletion of DNA methyltransferases that coincided with their demethylation responses. In agreement with these data, DNA methylation analysis of blood and bone marrow samples from MDS patients undergoing azacytidine therapy also revealed substantial differences in the epigenetic responses of individual patients. Significant, transient demethylation could be observed in 3 of 6 patients and affected many hypermethylated loci in a complex pattern. Our results provide important proof-of-mechanism data for the demethylating activity of azacytidine in MDS patients and provide detailed insight into drug-induced demethylation responses.
Abstract: Earlier analyses on the sirtuin family of histone deacetylases and its well-known member SIRT1 had their primary focus mostly on the identification of cellular targets exploring molecular mechanisms and functional networks in the control of metabolic homeostasis, differentiation, apoptosis and cell survival. However, only little is known about the regulation of SIRT1 itself, so far. Presently, SIRT1 is gaining increasing importance in the development of innovative treatment strategies for cancer, neurodegenerative disorders and metabolic disease. Based on differences in their catalytic activities, SIRT1 and the sirtuins in general, are insensitive to the classical class I and II HDAC inhibitors which are increasingly becoming part of treatment regimens for solid tumors and hematological malignancies. In this review we outline recent research advances on the regulation of SIRT1 which may provide the basis for the development of therapeutic inhibitors with improved specificity.
Abstract: With an increasing cancer rate worldwide, there is an urgent quest for the improvement of anticancer drugs. One of the main problems of present chemotherapy in treatment of tumor patients is the toxicity of drugs. Most of the existent anticancer drugs, unfortunately, attack also proliferating normal cells. In recent years, traditional Chinese herbal remedies have gradually gained considerable attention as a new source of anticancer drugs. Although their healing mechanisms are still largely unknown, some of the drugs have been used to help cancer patients fight their disease at reduced side effects compared to other treatments. In our study, we show that Rocaglamide (Roc), derived from the traditional Chinese medicinal plants Aglaia, induces apoptosis through the intrinsic death pathway in various human leukemia cell lines and in acute lymphoblastic leukemia, chronic myeloid leukemia and acute myeloid leukemia cells freshly isolated from patients. Investigation of the molecular mechanisms by which Roc kills tumors revealed that it induces a consistent activation of the stress-response mitogen-activated protein kinase (MAPK) p38 accompanied with a long-term suppression of the survival MAPK extracellular signal-regulated kinase. These events affect proapoptotic Bcl-2 family proteins leading to depolarization of the mitochondrial membrane potential and trigger caspase-mediated apoptosis involving caspase-9, -8, -3 and -2. Importantly, Roc shows no effects on MAPKs in normal lymphocytes and therefore has no or very low toxicity on healthy cells. Up to now, more than 50 different Roc derivatives have been isolated from Aglaia. Our study suggests that Roc derivatives may be promising candidates for the development of new drugs against hematologic malignancies.
Abstract: OBJECTIVES: In order to establish an international standard of cold provocation test in the assessment of vibration-induced white finger (VWF) disease, an ISO-working group tentatively created the DIN ISO 14835-1. Based on this new standard, previously existing testing conditions had to be modified. Since a comparison of current and previous evaluation procedures is necessary for both the individual assessment and the performance of metaanalyses, the revision and validation of criteria for the examination of the cold provocation tests are appropriate and necessary. METHODS: Twenty-one individuals suffering from VWF disease whose disorder was accepted as an occupational disease underwent the cold provocation test on two successive days following a 2- and a 5-min-long exposure to the cold. As a benchmark for classification as 'normal' or 'pathological', the 15-min mark after a 2-min-long exposure was chosen. A skin temperature of 28 degrees C was selected for discrimination between 'non-pathological' (at least 28 degrees C) and 'pathological' test results. RESULTS: It could be shown, that exposures to cold water (12 degrees C) over 2 and 5 min lead to similar rewarming profiles, who differ in median systematically by 1 degrees C. A modification of the former classification rule should be considered. After a 5 min exposure, the classification criterion can be based on the temperature assessments measured after 20 min; alternatively the cut point can be reduced from 28 to 27 degrees C while maintaining the previous assessment time of t = 15 min. CONCLUSIONS: The shown results represent the first attempt of modifying the previous classification criteria of the cold provocation test within the scope of the VWF disease. In view of the described problems of the study design there is no doubt that continuing modifications and their validation on the base of larger collectives groups are necessary.
Abstract: Sirtuin 6 (SIRT6) is a member of the sirtuin deacetylases (sirtuins), which are derivatives of the yeast Silent information regulator 2 (Sir2) protein. SIR2 and its mammalian derivatives play a central role in epigenetic gene silencing, recombination, metabolism, cell differentiation and in the regulation of aging. In contrast to most sirtuins, SIRT6 lacks NAD+-dependent protein deacetylase activity. We have isolated and characterized the human Sirt6 genomic sequence, which spans a region of 8,427 bp and which has one single genomic locus. Determination of the exon-intron splice junctions found the full-length SIRT6 protein to consist of 8 exons ranging in size from 60 bp (exon 4) to 838 bp (exon 8). The human Sirt6 open reading frame encodes a 355-aa protein with a predictive molecular weight of 39.1 kDa and an isoelectric point of 9.12. Characterization of the 5' flanking genomic region, which precedes the Sirt6 open reading frame, revealed a TATA- and CCAAT-box less promoter with an approximately 300-bp long CpG island. A number of AML-1 and GATA-x transcription factor binding sites were found which remain to be further evaluated experimentally. Fluorescence in situ hybridization analysis localized the human Sirt6 gene to chromosome 19p13.3; a region which is frequently affected by chromosomal alterations in acute leukemia. Human SIRT6 appears to be most predominantly expressed in bone cells and in the ovaries while, in the bone marrow, it is practically absent. The functional characteristics of SIRT6 are essentially unknown at present and remain to be elucidated.
Abstract: Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase, which belongs to the silent information regulator 2 (Sir2) family of sirtuin histone deacetylases (HDACs). The yeast Sir2 protein and its mammalian derivatives play a central role in epigenetic gene silencing, DNA repair and recombination, cell-cycle, microtubule organization, and in the regulation of aging. We have isolated and characterized the human Sirt1 genomic sequence, which spans a region of 33,660 bp and which has one single genomic locus. Determination of the exon-intron splice junctions established that SIRT1 is encoded by 9 exons ranging in size from 80 bp (exon 6) to 2,120 bp (exon 9). Characterization of the 5' flanking genomic region, which precedes the Sirt1 open reading frame, revealed a CCAAT-box and a number of NF-kappaB and GATA transcription factor binding sites in addition to a small 350 bp CpG island. The 4,107 bp human Sirt1 mRNA has an open reading frame of 2,244 bp and encodes a 747 aa protein with a predictive molecular weight of 81.7 kDa and an isoelectric point of 4.55. Fluorescence in situ hybridization analysis localized the human Sirt1 gene to chromosome 10q21.3.
Abstract: TNFalpha has previously been used in anticancer therapy. However, the therapeutic application of TNFalpha was largely limited due to its general toxicity and the fact that it activates the NF-kappaB-family transcription factors, which are proinflammatory and antiapoptotic. To overcome this problem in vitro, specific NF-kappaB inhibitors or transcription or protein synthesis inhibitors such as actinomycin D and cycloheximide are usually used in combination to increase TNFalpha killing of tumor cells. However, these agents also cause harmful side effects in vivo. We show here that wogonin, derived from the popular Chinese herb Huang-Qin, attenuates NF-kappaB activity by shifting TNFalpha-induced free radical .O(2)(-) to a more reduced nonradical product, H(2)O(2), and thereby sensitizes TNFalpha-resistant leukemia cells to TNFalpha-induced apoptosis. Importantly, wogonin does not affect the viability of normal peripheral blood T cells. Wogonin also sensitizes TRAIL-induced apoptosis. Our data suggest a potential use of wogonin as a TNFalpha or TRAIL adjuvant for cancer treatment. Our data also demonstrate how a herbal compound enhances killing of tumor cells with reduced side effects compared with other treatments.
Abstract: Sirtuin 5 (SIRT5) is a nicotinamide adenine dinucleotide (NAD+)-dependent deacetylase and belongs to the Silent information regulator 2 (Sir2) family of sirtuin histone deacetylases (HDACs), which play a central role in epigenetic gene silencing, DNA repair and recombination, cell-cycle, microtubule organization, and in the regulation of aging. We have isolated and characterized the human SIRT5 genomic sequence, which spans a region of 28,182 bp and which has one single genomic locus. Human SIRT5 consists of eight exons and is found in two isoforms, which encode a 310 aa and a 299 aa protein, respectively. Human SIRT5 is most predominantly expressed in heart muscle cells and in lymphoblasts. Fluorescence in situ hybridization analysis localized the human SIRT5 gene to chromosome 6p23.
Abstract: BACKGROUND: Interferons have been reported to significantly contribute to tumor suppression via both induction of p53 gene expression and inhibition of angiogenesis. OBJECTIVE: The assessment of treatment toxicity and antitumoral effectiveness of continuous IV administration of interferon-beta based on an overall evaluation of laboratory, radiographic, and clinical parameters observed during the trial. METHODS: The authors treated patients with advanced malignant melanoma with continuous IV infusions of 1 x 10(6) IU interferon-beta daily ( approximately 0.6 x 10(6) IU interferon-beta/m2 daily). RESULTS: Continuous IV administration of interferon-beta had no significant effect on overall patient outcome. Interferon side effects were not a reason for treatment discontinuation in any of the patients observed during this trial. CONCLUSIONS: Continuous IV interferon-beta had no significant effect on overall patient outcome in a group of patients with advanced malignant melanoma. To our knowledge, this is the first report on the continuous IV administration of interferon-beta in patients with advanced malignant melanoma.
Abstract: Sirtuin 7 (SIRT7) is a member of the sirtuin family of protein deacetylases and is, therefore, a derivative of yeast Silent information regulator 2 (SIR2). SIR2 and its mammalian orthologs play an important role in epigenetic gene silencing, DNA recombination, cellular differentiation and metabolism, and the regulation of aging. In contrast to most sirtuins, SIRT7 does not exert characteristic NAD+-dependent deacetylase activity. We have isolated and characterized the human Sirt7 genomic sequence, which spans a region of 6.2 kb and which has one single genomic locus. Determination of the exon/intron splice junctions found the full-length SIRT7 protein to consist of 10 exons ranging in size from 71 bp (exon 4) to 237 bp (exon 7). The human Sirt7 open reading frame encodes a 400-aa protein with a predictive molecular weight of 44.9 kDa and an isoelectric point of 9.80. Characterization of the 5' flanking genomic region, which precedes the Sirt7 open reading frame, revealed a TATA- and CCAAT-box less promoter that lacks CpG islands. A number of AML-1 and GATA-x transcription factor binding sites were found, which remain to be further evaluated experimentally. Fluorescence in situ hybridization analysis localized the human Sirt7 gene to chromosome 17q25.3; a region which is frequently affected by chromosomal alterations in acute leukemias and lymphomas. Human SIRT7 appears to be most predominantly expressed in the blood and in CD33+ myeloid bone marrow precursor cells, while the lowest levels are found in the ovaries and skeletal muscle. Functional characteristics of SIRT7 are essentially unknown at present and remain to be further elucidated.
Abstract: In chronic myelocytic leukemia (CML) the activity of the Bcr-Abl tyrosine kinase is known to activate a number of molecular mechanisms, which inhibit apoptosis. In the present study, we show that the histone deacetylase inhibitor SAHA (suberoylanilide hydroxamic acid) markedly decreases protein expression levels of Bcr-Abl and c-Myc in BV-173 cells, while in K562 cells only a minor decrease of Bcr-Abl protein levels is observed while a considerable reduction of c-Myc protein expression may only be achieved at higher concentrations of SAHA. In addition, we found BV-173 cells to be more sensitive to SAHA-induced apoptosis when compared to K562 cells. Even though earlier reports on SAHA considerably focused on its inhibitory effect on HDAC enzymatic activity, we report herein a significant down-regulation of HDAC3 protein expression levels following treatment with SAHA in BV-173 cells, but not in K562 cells. In conclusion, our results imply a molecular mechanism for SAHA-induced apoptosis in BV-173 cells, which involves decreased protein expression levels of Bcr-Abl, c-Myc and HDAC3.
Abstract: The progressively aging population in the western world, rising socioeconomic expenditure and increasing costs for the treatment of adverse drug reactions, lead to increasing pressure on public spending. The public acceptance of pharmacogenomics is high, therefore, because it promises individualized safe and effective treatment at lower cost. Pharmacogenomics studies the genetic polymorphisms that underlie the variability in drug response between individuals. Despite the great benefits being awaited from this new field, a number of ethical, social and legal concerns arise, which demand rapid strict international regulations in order to prevent discrimination or harm of any kind from society, industry, groups or individuals.
Abstract: Sirtuin 2 (SIRT2) is a nicotinamide adenine dinucleotide (NAD(+))-dependent deacetylase, which belongs to the Silent information regulator 2 (Sir2) family of sirtuin histone deacetylases (HDACs). The yeast Sir2 protein and its mammalian derivatives play a central role in epigenetic gene silencing, DNA repair and recombination, cell-cycle, microtubule organization, and in the regulation of aging. We have isolated and characterized the human Sirt2 genomic sequence, which spans a region of 20,960 bp and which has one single genomic locus. Determination of the exon-intron splice junctions found the full-length SIRT2 protein to consist of 16 exons ranging in size from 16 bp (exon 1) to 749 bp (exon 9). The 1,963-bp human Sirt2 mRNA has an open reading frame of 1,167 bp that encodes two isoforms of the SIRT2 protein: isoform 1 encodes a 389-aa protein with a predictive molecular weight of 43.2 kDa and an isoelectric point of 5.22, while isoform 2, which is lacking the first three exons, encodes a 352-aa protein with a predictive molecular weight of 39.5 kDa and an isoelectric point of 6.05. Characterization of the 5' flanking genomic region, which precedes the Sirt2 open reading frame, revealed a TATA- and CCAAT-box less promoter that contains a 0.67-kb CpG island and a number of NFkappaB and GATA transcription factor binding sites. Fluorescence in situ hybridization analysis localized the human Sirt2 gene to chromosome 19q13.1. Human SIRT2 is known to be most predominantly expressed in the brain. Since it is however severely reduced in a large number of human brain tumor cell lines, the absence of SIRT2, a potential tumor suppressor, could play a key role in the regulation of the cell-cycle within a multistep pathway that leads to full cellular transformation and, finally, the development of cellular malignancy.
Abstract: Histone deacetylases (HDACs) play a central role in the modification of chromatin structure and thus in the regulation of transcription and cellular differentiation. Based on structural and functional similarities, mammalian histone deacetylases may be grouped into four categories: class I HDACs, which are homologs of the yeast histone deacetylase RPD3; class II HDACs, which share a significant degree of homology with the yeast histone deacetylase HDA1; class III HDACs, which are closely related to the yeast SIR2 protein; and the most recently described class IV of HDACs, which comprises HDAC11-related enzymes. We have isolated and characterized the human HDAC11 genomic sequence, which spans a region of 24,074 bp and has a single genomic locus. Determination of the exon-intron splice junctions established that HDAC11 is encoded by 9 exons ranging in size from 43 bp (exon 4) to 867 bp (exon 9). Characterization of the 5' flanking genomic region, which precedes the HDAC11 open reading frame, revealed a TATA and CCAAT box-less promoter that contains a 1-kb CpG island. The 1,733-bp human HDAC11 mRNA encodes a 347 aa protein with a predictive molecular weight of 39.1 kDa and an isoelectric point of 6.88. Fluorescence in situ hybridization analysis localized the human HDAC11 gene to chromosome 3p25, a region characterized by frequent gains and losses of chromosomal material in a number of various types of cancer.
Abstract: During inflammatory events, the induction of immediate-early genes, such as TNF-alpha, is regulated by signaling cascades including the JAK/STAT, NF-kappaB, and the p38 MAPK pathways, which result in phosphorylation-dependent activation of transcription factors. We observed the direct interaction of histone deacetylase (HDAC) 3, a class I histone deacetylase, with MAPK11 (p38 beta isoform) by West-Western-based screening analysis, pull-down assay, and two-hybrid system analysis. Results further indicated that HDAC3 decreases the MAPK11 phosphorylation state and inhibits the activity of the MAPK11-dependent transcription factor, activating transcription factor-2 (ATF-2). LPS-mediated activation of ATF-2 was inhibited by HDAC3 in a time- and dose-dependent manner. Inhibition of HDAC3 expression by RNA interference resulted in increased ATF-2 activation in response to LPS stimulation. In agreement with decreased ATF-2 transcriptional activity by HDAC3, HDAC3-repressed TNF gene expression, and TNF protein production observed in response to LPS stimulation. Therefore, our results indicate that HDAC3 interacts directly and selectively with MAPK11, represses ATF-2 transcriptional activity, and acts as a regulator of TNF gene expression in LPS-stimulated cells, especially in mononuclear phagocytes.
Abstract: Acetylation and deacetylation of nucleosomal histones play an important role in the modulation of chromatin structure, chromatin function and in the regulation of gene expression. Histone acetyltransferases (HATs) and histone deacetylases (HDACs) are two opposing classes of enzymes, which tightly control the equilibrium of histone acetylation. An imbalance in the equilibrium of histone acetylation has been associated with carcinogenesis and cancer progression. So far, a number of structurally distinct classes of compounds have been identified as HDAC inhibitors including the short-chain fatty acids, hydroxamates, cyclic tetrapeptides and benzamides. These compounds lead to an accumulation of acetylated histone proteins both in tumor cells and in normal tissues. HDAC inhibitors are able to activate differentiation, to arrest the cell cycle in G1 and/or G2, and to induce apoptosis in transformed or cancer cells. Attention is currently being drawn to molecular mechanisms involving histone deacetylases. An induction of p21(WAF/CIP1) and a suppression of angiogenic stimulating factors have been observed in tumor cells following exposure to HDAC inhibitors. In xenograft models, several HDAC inhibitors have demonstrated antitumor activity with only few side effects. Several clinical trials showed that HDAC inhibitors in well tolerated doses have significant antitumoral activities. A combination of HDAC inhibitors with differentiation-inducing agents and cytotoxic drugs is an innovative therapeutic strategy that carries the potential for significant improvements in the treatment of cancer.
Abstract: PFKFB (6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase) is a bifunctional enzyme that regulates the steady-state concentration of fructose-2,6-bisphosphate, which is a potent activator of the key regulatory enzyme of glycolysis, phosphofructokinase. PFKFB3 (iPFK2) is one of four tissue-specific PFKFB isozymes that have been identified to date. PFKFB3 also has been implicated in the high glycolytic rate of cancer cells that occurs despite adequate oxygen, a phenomenon known as the Warburg effect. We have isolated and characterized the human PFKFB3 genomic sequence, which spans a region of 32.5 kb and which has a single chromosomal locus. Determination of the exon-intron splice junctions established that PFKFB3 is encoded by 19 exons of which only 15 are normally expressed. Exon sizes range between 23 and 208 bp, the largest intron is 10,286 bp long. The full-length human PFKFB3 open reading frame is 4,675 bp long and encodes a 590 aa protein with a predicted molecular weight of 66.9 kDa and an isoelectric point of 8.64. Fluorescence in situ hybridization analysis localized the human PFKFB3 gene to chromosome 10p15.3-p15.2, and its locus is 3 million bp centromeric to PFKP, the platelet-type phosphofructokinase. PFKFB3 has been shown to be abundantly expressed in human tumors and its expression linked to long-standing observations concerning the apparent coupling of enhanced glycolysis and cell proliferation.
Abstract: Histone deacetylases (HDACs) play a central role in the modification of chromatin structure and thus in the regulation of transcription and cellular differentiation. Based on structural and functional similarities, mammalian histone deacetylases may be grouped into three categories, class I HDACs, which are homologs of the yeast histone deacetylase RPD3, class II HDACs, which share a significant degree of homology with the yeast histone deacetylase HDA1 and class III HDACs which are closely related to the yeast SIR2 protein. We have isolated and characterized the human HDAC6 genomic sequence, which spans a region of 21,923 bp and which has one single genomic locus. Determination of the exon-intron splice junctions established that HDAC6 is encoded by 28 exons ranging in size from 41 bp (exon 5) to 677 bp (exon 24). Characterization of the 5' flanking genomic region, which precedes the HDAC6 open reading frame, revealed a TATA- and CCAAT-boxless promoter that contains a 1 kb CpG island. The 3,648 bp human HDAC6 mRNA encodes a 1,215 aa protein with a predictive molecular weight of 131.4 kDa. Fluorescence in situ hybridization analysis localized the human HDAC6 gene to the subband border of chromosome Xp11.22-23, a region which is characterized by frequent gains and losses of chromosomal material in several types of cancer and neurological disorders.
Abstract: Epigenetically mediated modulation of gene promoter function through histone acetylation modifying enzymes, which regulate the acetylation state of histone proteins and other promoter-bound transcription factors, is increasingly appreciated as a key component in the regulation of reversible gene expression. While histone acetyltransferases (HATs), which are frequently part of multisubunit coactivator complexes, lead to the relaxation of chromatin structure and transcriptional activation, histone deacetylases (HDACs) tend to associate with multisubunit corepressor complexes, which result in chromatin condensation and transcriptional repression of specific target genes. We have isolated and characterized the human HDAC9 genomic sequence, which spans a region of 458 kb and which has one single chromosomal locus. Determination of the exon-intron splice-junctions established that HDAC9 is encoded by 23 exons ranging in size from 22 bp (exon 1) to 264 bp (exon 11). Characterization of the 5' flanking genomic region revealed that the human HDAC9 promoter lacks both the canonical TATA and CCAAT boxes; CpG elements are missing. The human HDAC9 open reading frame is 3036 bp long and encodes a 1011 aa protein with a predictive molecular weight of 111.3 kDa and an isoelectric point of 6.41. Fluorescence in situ hybridization analysis localized the human HDAC9 gene to chromosome 7p21, a region which has been associated particularly with the pathogenesis of gynecological tumors.
Abstract: Recent studies indicate that macrophages modulate T-cell apoptosis in HIV infection. Macrophages have been shown to trigger apoptosis of uninfected bystander T cells and to protect HIV-infected T cells from apoptosis. This article raises the possibility that macrophages, via modulation of T-cell apoptosis, play a crucial role in both immune suppression and the formation of viral reservoirs during HIV infection.
Abstract: Even though a rough sketch of the human genome is now available and the number of newly discovered genes, which carry the potential of being biologically and medically relevant is currently greater than ever, only a small proportion has been assigned a biological function. Therefore, enormous attention is now increasingly being drawn towards functional genomics, i.e. the functional characterization of these newly identified sequences. In order to elucidate the role of a particular gene product within its cellular context, we have screened high-density protein filter arrays for protein-protein interactions on the basis of a 'Far-Western' based approach. The methodology described herein easily allows the identification and isolation of cDNAs of proteins, which interact with specific ligands (interacting proteins, antibodies and DNA/RNA sequences), and represents an alternative to tedious conventional protein interaction analyses. Far-Western screening in the context of a whole-genome expression analysis not only facilitates the assignment of biological functions to specific, newly identified protein and DNA sequences, but also is useful in studies that assess the binding capacity of mutant proteins to their interaction partner and in the identification of domains and amino acids involved in known protein-protein interactions. Taken together, we describe an approach that allows the easy and reproducible identification of protein ligands on the basis of a whole-genome expression analysis.
Abstract: Increasing evidence from recent research suggests a connection between cancer and a deranged equilibrium of histone acetylation, which is maintained by two competing enzymatic activities, histone acetyltransferases (HATs) and histone deacetylases (HDACs). It is our hypothesis that a significant proportion of leukemias and possibly also solid tumors have abnormalities involving HATs or HDACs at the genomic level through genetic mutations or chromosomal alterations. In these cases, altered levels of HATs or HDACs may derange the tightly regulated equilibrium of histone acetylation, which may affect the expression of a broad spectrum of cellular genes. On the other hand, HATs and HDACs may be carried to defined target promoters as cofactors of transcription factor-bound repressor or enhancer complexes and thereby carry out unwanted enzymatic activities in the wrong place at the wrong time. We therefore propose a model for disease being associated with a deranged equilibrium of acetylation that affects histone proteins and promoter-bound transcription factors.
Abstract: Histone deacetylases (HDACs) are important participants in the remodeling of chromatin structure and in the regulation of eukaryotic proliferation and differentiation. We have isolated and characterized the human HDAC5 genomic sequence, which spans a region of 39,138 bp and which has one single chromosomal locus. Determination of the exon-intron splice junctions established that HDAC5 is encoded by 26 exons ranging in size from 22 bp (exon 1) to 285 bp (exon 12). Characterization of the 5' flanking genomic region revealed that the human HDAC5 promoter lacks both the canonical TATA and CCAAT boxes. The human HDAC5 mRNA encodes a 1122 aa protein with a predictive molecular mass of 121.9 kDa and an isoelectric point of 5.84. Fluorescence in situ hybridization analysis localized the human HDAC5 gene to chromosome 17q21, a region which is characterized by frequent gains and losses of chromosomal material in several types of cancer.
Abstract: Chromatin structure is gaining increasing attention as a potential target in the treatment of cancer. Relaxation of the chromatin fiber facilitates transcription and is regulated by two competing enzymatic activities, histone acetyltransferases (HATs) and histone deacetylases (HDACs), which modify the acetylation state of histone proteins and other promoter-bound transcription factors. While HATs, which are frequently part of multisubunit coactivator complexes, lead to the relaxation of chromatin structure and transcriptional activation, HDACs tend to associate with multisubunit core-pressor complexes, which result in chromatin condensation and transcriptional repression of specific target genes. HATs and HDACs are known to be involved both in the pathogenesis as well as in the suppression of cancer. Some of the genes encoding these enzymes have been shown to be rearranged in the context of chromosomal translocations in human acute leukemias and solid tumors, where fusions of regulatory and coding regions of a variety of transcription factor genes result in completely new gene products that may interfere with regulatory cascades controlling cell growth and differentiation. On the other hand, some histone acetylation-modifying enzymes have been located within chromosomal regions that are particularly prone to chromosomal breaks. In these cases gains and losses of chromosomal material may affect the availability of functionally active HATs and HDACs, which in turn disturbs the tightly controlled equilibrium of histone acetylation. We review herein the recent achievements, which further help to elucidate the biological role of histone acetylation modifying enzymes and their potential impact on our current understanding of the molecular changes involved in the development of solid tumors and leukemias.
Abstract: Apoptosis or programmed cell death may play a critical role in AIDS pathogenesis through depletion of both CD4(+) and CD8(+) T lymphocytes. Using a reporter virus, a recombinant HIV infectious clone expressing the green fluorescent protein (GFP), apoptosis was measured in productively infected CD4(+) T lymphocytes, in the presence and absence of autologous macrophages. The presence of macrophages in the culture increased the frequency of nonapoptotic GFP-positive productively infected CD4(+) T lymphocytes. The appearance of nonapoptotic productively infected CD4(+) T lymphocytes in the culture required intercellular contacts between macrophages and PBLs and the expression of the HIV Nef protein. The presence of macrophages did not reduce apoptosis when CD4(+) T lymphocytes were infected with a GFP-tagged virus deleted for the nef gene. TNF-alpha (TNF) expressed on the surface of macrophages prevented apoptosis in nef-expressing, productively infected CD4(+) T lymphocytes. Similarly, following TNF stimulation, apoptosis was diminished in Jurkat T cells transfected with a nef-expressing plasmid. TNF stimulation of nef-expressing Jurkat T cells resulted in NF-kappaB hyperactivation, which has been shown to deliver anti-apoptotic signals. Our results indicate that intercellular contacts with macrophages increase the rate of productively infected nonapoptotic CD4(+) T lymphocytes. The survival of productively infected CD4(+) T lymphocytes requires Nef expression as well as activation by TNF expressed on the surface of macrophages and might participate in the formation and maintenance of viral reservoirs in HIV-infected persons.
Abstract: Reversible acetylation of histone proteins plays a critical role in transcriptional regulation, cell cycle progression, and developmental events. The steady state of histone acetylation is controlled by the enzymatic activities of multiple histone acetyltransferases and histone deacetylases (HDACs). Three distinct human HDACs are homologous to RPD3, a yeast transcriptional regulator. We have isolated and sequenced a genomic clone for the human HDAC3 gene. This is a single-copy gene spanning a region of at least 13 kb. Determination of the intron-exon splice junctions established that the gene is encoded by 15 exons ranging in size from 56 to 657 bp. Fluorescence in situ hybridization studies localized this gene to 5q31. Double-target experiments in which both HDAC3 and the early-growth response 1 gene (EGR1), which is localized in the 5q31.2 region, were used as probes showed that the HDAC3 gene lies in region 5q31.3, immediately distal to EGR1 with respect to the centromere.
Abstract: Histone acetylation modifiers have been described to participate as cofactors in mammalian transcriptional complexes involved in the regulation of cellular proliferation and differentiation. The acetylation of core histone proteins is reversible and regulated by two competing enzymatic activities, histone acetyltransferases (HATs) and histone deacetylases (HDACs). Increasing evidence suggests a connection between histone acetylation and the development of cancer and leukemia. We have recently mapped HDAC3 to mouse chromosome 18B3, a region which is syntenic with human chromosome 5q31, where HDAC3 is imbedded in a group of potential tumor suppressor genes and which has been reported to be the smallest commonly deleted segment in malignant myeloid disease. We report herein the identification and characterization of HDAC3, a yeast RPD3 ortholog in the mouse. Studies on murine HDAC3 may yield important insights on the understanding of myeloproliferative disease in humans.
Abstract: Histone deacetylases have been described as crucial cofactors of mammalian transcriptional complexes. We have recently identified human histone deacetylase HDAC3 on chromosome 5q31 by fluorescence in situ hybridization (FISH) in a region commonly deleted in malignant myeloid disease. Since HDAC3 carries strong potential to be a tumor suppressor gene, we report herein its exact position between the CD14 and GRIA1 genes within the 5q31.1 subband.
Abstract: CD8-positive T cells are thought to play an important role in the control of infection by human immunodeficiency virus (HIV) as a result of their cytotoxic activity and by releasing soluble factors. In AIDS patients, the absolute number of CD8+ T lymphocytes is decreased in peripheral blood and their turnover rate is increased, suggesting that there is more cell renewal and cell death occurring. Anti-retroviral therapy raises CD8+ T-cell counts in HIV-infected patients. Here we report that the death rate of CD8+ T cells by apoptosis increased markedly during HIV infection of peripheral blood mononuclear cells in vitro. Apoptosis is induced in a dose-dependent manner by recombinant envelope glycoprotein gp120 from HIV strain X4, or by stromal-derived factor-1 (SDF-1), the physiological ligand of the chemokine receptor CXCR4. Apoptosis is mediated by the interaction between tumour-necrosis factor-alpha bound to the membrane of macrophages (mbTNF) and a receptor on CD8+ T cells (TNF-receptor II, or TNFRII). The expression of both of these cell-surface proteins is upregulated by HIV infection or by treatment with recombinant gp120 or SDF-1. Apoptosis of CD8+ T cells isolated from HIV-infected patients is also mediated by macrophages through the interaction between mbTNF and TNFRII. These results indicate that the increased turnover of CD8+ T cells in HIV-infected subjects is mediated by the HIV envelope protein through the CXCR4 chemokine receptor.
Abstract: Invasive opportunistic mycoses are common complications in patients suffering from hematological disorders. Brain abscesses in the immunocompromised host are known to be most frequently caused by fungi of the Aspergillus species and are often associated with concomitant pulmonary disease. As the penetration of the currently available antifungal agents into the brain tissue is limited, only very few patients have been described to survive this life-threatening condition. We report the case of a 62 year old female patient who presented with multiple aspergillus brain abscesses during prolonged neutropenia following induction chemotherapy for acute myeloblastic leukemia and was successfully treated with high dose (8 mg/kg/day) liposomal amphotericin B.
Abstract: TSST-1 is a Staphylococcus aureus-derived superantigen which has been implicated in the pathogenesis of toxic shock syndrome. In mice, superantigen-induced proliferation is followed by deletion or anergy of reactive T cells. So far, superantigen-induced T-cell anergy has not been observed in humans. We therefore examined PBMCs derived from a 15-year-old patient suffering from severe toxic shock syndrome. Markedly elevated levels of circulating TSST-1-reactive T cells were found by cytofluorometric analysis. Upon in vitro restimulation with TSST-1, hyporesponsiveness of TSST-1-responsive V beta 2+ T cells was detected, thus confirming results obtained in the murine system.
Abstract: Superantigens interact with and activate a sizeable fraction of T cells characterized by expression of specific V beta gene segments of their antigen receptor. The massive activation of T cells in an organism is considered responsible for clinical symptoms associated with superantigen-producing bacteria. Here we studied the in vitro activation of human T cells by the superantigen Staphylococcus Enterotoxin B on a cell by cell basis. Superantigen-reactive T cells were stained with a V beta 12-specific monoclonal antibody and analyzed in a cytofluorograph. Blast formation of SEB-reactive T cells occurs within 12 h and reaches a plateau after 24 h. Double-staining of V beta 12+ T cells with antibodies against different T cell activation or adhesion surface molecules revealed a time-dependent differential upregulation for CD2, CD11 = LFA-1, CD25, CD28, CD69, and HLA-DR. The expression of CD3, CD4 and CD5 was not influenced by the superantigen. The rapid phenotypic changes of superantigen reactive T cells in terms of marker expression and cell size could provide early tools in diagnosing diseases caused by superantigens.
