PubMed Health⌕ Search

Biomedical subjects

Ulrich Mahlknecht

Publications and source records attributed to Ulrich Mahlknecht.

16 recordsLinked to original sources
PubMed2006

Wogonin sensitizes resistant malignant cells to TNFalpha- and TRAIL-induced apoptosis.

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.

Apoptosis↗
PubMed2006

Cloning, chromosomal characterization and mapping of the NAD-dependent histone deacetylases gene sirtuin 1.

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.

Amino Acid Sequence↗
PubMed2006

Chromosomal organization and fluorescence in situ hybridization of the human Sirtuin 6 gene.

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.

Alu Elements↗
PubMed2006

Fluorescence in situ hybridization and chromosomal organization of the human Sirtuin 7 gene.

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.

5' Flanking Region↗
PubMed2005

Pharmacogenomics: questions and concerns.

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.

Delivery of Health Care↗
PubMed2005

The histone deacetylase inhibitor suberoylanilide hydroxamic acid down-regulates expression levels of Bcr-abl, c-Myc and HDAC3 in chronic myeloid leukemia cell lines.

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.

Apoptosis↗
PubMed2005

Chromosomal organization and localization of the novel class IV human histone deacetylase 11 gene.

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.

Amino Acid Sequence↗
PubMed2005

FISH-mapping and genomic organization of the NAD-dependent histone deacetylase gene, Sirtuin 2 (Sirt2).

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.

Amino Acid Sequence↗
PubMed2004

Histone deacetylase 3, a class I histone deacetylase, suppresses MAPK11-mediated activating transcription factor-2 activation and represses TNF gene expression.

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.

Activating Transcription Factor 2↗
PubMed2004

Role of histone deacetylase inhibitors in the treatment of cancer (Review).

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.

Animals↗
PubMed2003

Cloning and structural characterization of the human histone deacetylase 6 gene.

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.

Amino Acid Sequence↗
PubMed2003

Cloning and chromosomal characterization of the 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 gene (PFKFB3, iPFK2).

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.

Amino Acid Sequence↗
PubMed2002

Chromosomal organization and localization of the human histone deacetylase 9 gene (HDAC9).

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.

Amino Acid Sequence↗
PubMedDate not supplied

Phase 2 trial of the continuous IV administration of interferon-beta in patients with disseminated malignant melanoma.

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.

Aged↗