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Dieter Hoelzer

Publications and source records attributed to Dieter Hoelzer.

At least 91 records · Page 5Linked to original sources
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↗
PubMed2002

Folinic acid antagonizes methotrexate-induced differentiation of monocyte progenitors.

OBJECTIVE: The anti-inflammatory action of low-dose methoxetrate (MTX) in the treatment of rheumatoid arthritis (RA) appears to be partially impaired by folate supplementation. Here we investigated whether a folate excess impairs monocyte differentiation, a putative anti-inflammatory action of low-dose MTX. METHODS: Monocyte differentiation of U937 promonocytic cells was assessed by CD11b and CD14 immunostaining and fluorescent absorbent cell sorting (FACS) analysis. Cell proliferation and viability were determined by cell counts and trypan-blue staining, respectively. Nuclear apoptosis was assessed by 7-actinomycin staining. Cells were treated with 10(-10)-10(-6) M MTX in the presence or absence of folinic acid. Exposure to 1,25-OH-vitamine D(3) and TGF-beta served as a positive control of monocyte differentiation in U937 cells. RESULTS: Low-dose MTX-induced monocyte differentiation was marginal when compared with 1,25-OH-D(3) + TGF-beta treatment. Low-dose MTX inhibited cell proliferation, induced apoptosis, and reduced cell viability. All the antiproliferative, cytotoxic, and monocyte differentiating effects of MTX were completely reversed by folinic acid. CONCLUSIONS: Monocyte differentiation is part of the folate-dependent MTX actions.

Antirheumatic Agents↗
PubMed2002

Differential effects of histone deacetylase inhibitors on interleukin-18 gene expression in myeloid cells.

Histone deacetyrase (HDAC) inhibitors induce growth arrest and differentiation of leukemia cell lines and tumor cells derived from a large variety of human tissues. Here we showed that HDAC inhibitors sodium butyrate, TSA, and valproate regulated the expression of Interleukin-18 (IL-18), a cytokine with antitumor and proinflammatory properties, in human acute myeloid leukemia cell lines U937 and HEL. Sodium butyrate increased expression of IL-18 protein and mRNA and activated 1357bp IL-18 gene promoter construct. IL-18 mRNA level was up-regulated by TSA or valproate, which also activated IL-18 full-length promoter. While sodium butyrate or TSA stimulated the 108-bp IL-18 minimal promoter, valproate failed to activate it, indicating that valproate may use a distinct mechanism from sodium butyrate and TSA to activate IL-18 gene expression.

Blotting, Northern↗
PubMed2002

In lymphatic cells par-4 sensitizes to apoptosis by down-regulating bcl-2 and promoting disruption of mitochondrial membrane potential and caspase activation.

Inhibition of apoptosis is a hallmark of malignancies of the hematopoetic system. Previous studies in nonhematopoetic cells demonstrated that the prostate-apoptosis-response-gene-4 (Par-4) is up-regulated in cells undergoing programmed cell death and that Par-4 exerts its proapoptotic effect by down-regulating Bcl-2. After showing the aberrant expressional pattern of Par-4 in neoplastic lymphocytes as well as demonstrating inverse expressional patterns of Par-4 and Bcl-2 in malignant cells of patients suffering from acute lymphocytic leukemia, we assessed the functional consequences of Par-4 overexpression during apoptosis in Jurkat T lymphocytes. We show that in lymphatic cells Par-4 overexpression decreases the level of Bcl-2, whereas Bax, the proapoptotic counterpart of Bcl-2, retains unaltered levels. Moreover, Par-4 overexpression is accompanied by cleavage of poly(ADP-ribose) polymerase (PARP). Despite these effects, overexpression of Par-4 alone is not sufficient to induce apoptosis but markedly increases the rate of apoptosis on treatment with different chemotherapeutic agents. On chemotherapeutic treatment Par-4 overexpression enhances disruption of mitochondrial membrane potential, PARP-cleaving activity, as well as activation of caspase-3. The hypothesis of caspase-dependency of Par-4-promoted apoptosis is additionally supported by demonstrating complete abrogation of programmed cell death after pretreatment with a broad spectrum caspase-inhibitor. On inhibition of caspase-3 overexpression of Par-4 enables lymphatic cells to alternatively activate caspases-9, -6, and -7 by diminishing the influence of the inhibitors of apoptosis proteins (IAPs) cIAP1 and XIAP. Our study is the first to identify Par-4 as a proapoptotic protein in lymphatic cells, outlining a model of action evaluating the role of Bcl-2/Bax, as well as demonstrating the impact of Par-4 expression on PARP cleavage, disruption of mitochondrial membrane potential, caspase activation, and interactions with inhibitors of apoptosis proteins.

Antineoplastic Agents↗
PubMed2002

Leading prognostic relevance of the BCR-ABL translocation in adult acute B-lineage lymphoblastic leukemia: a prospective study of the German Multicenter Trial Group and confirmed polymerase chain reaction analysis.

The BCR-ABL fusion, the molecular equivalent of the Philadelphia translocation, gains importance for treatment stratification in adult acute lymphoblastic leukemia (ALL). In this prospective study, samples from 478 patients with CD10(+) B-cell precursor ALL (c-ALL and pre-B ALL) underwent BCR-ABL reverse transcription-polymerase chain reaction (RT-PCR) analysis with double testing of positive samples. Patients were stratified according to the PCR result and treated in 2 German Multicenter Trials of Adult ALL. The outcome was followed and the prognostic impact of BCR-ABL was compared to clinical risk features. Of the 478 samples, 432 had an evaluable BCR-ABL result. Thirty-seven percent of the c-ALL and pre-B ALL patients were BCR-ABL(+) (p190, 77%; p210, 20%; simultaneous p190/p210, 3%). BCR-ABL positivity was associated with the high-risk features of older age (45 years versus 30 years median age; P =.0001) and higher white blood cell counts (23 500/microL versus 11 550/microL; P =.0001). Univariate and multivariate analyses revealed BCR-ABL as the leading factor for a poor prognosis (P =.0001) in comparison to clinical risk criteria. Irrespective of the breakpoint, presence of any BCR-ABL transcript predicted a lower chance of initial treatment response (68.4% versus 84.6%; P =.001) and a lower probability of disease-free survival at 3 years (0.13 versus 0.47; P =.0001). This bad outcome was not influenced by postinduction high-dose treatment stratifications. The results show a high prevalence of BCR-ABL fusion transcripts with predominance of p190. BCR-ABL RT-PCR is confirmed as a sensitive, rapid method to diagnose t(9;22), and p190 and p210 are unequivocally demonstrated as the most important predictors of poor long-term survival despite intensified chemotherapy.

Adolescent↗
PubMed2002

Ph(+) acute lymphoblastic leukemia resistant to the tyrosine kinase inhibitor STI571 has a unique BCR-ABL gene mutation.

The tyrosine kinase inhibitor STI571 is a promising agent for the treatment of advanced Philadelphia chromosome positive (Ph(+)) acute lymphoblastic leukemia (ALL), but resistance develops rapidly in most patients after an initial response. To identify mechanisms of resistance to STI571, 30 complementary DNAs (including 9 matched samples) obtained from the bone marrow of individuals with Ph(+) ALL were analyzed by direct sequencing of a 714-base pair region of ABL encoding for the adenosine triphosphate (ATP)-binding site and the kinase activation loop. A single point mutation was found at nucleotide 1127 (GI6382056) resulting in Glu255Lys. This mutation occurred in 6 of 9 patients (67%) following their treatment with STI571 but not in the samples from patients before beginning treatment with STI571. Glu255Lys is within the motif important for forming the pocket of the ATP-binding site in ABL and it is highly conserved across species. In conclusion, Ph(+) ALL samples resistant to STI571 have a unique mutation Glu255Lys of BCR-ABL.

Antineoplastic Agents↗
PubMed2002

Mutations in the gene encoding the transcription factor CCAAT/enhancer binding protein alpha in myelodysplastic syndromes and acute myeloid leukemias.

The CCAAT/enhancer binding protein alpha (C/EBPalpha) protein is essential for proper lung and liver function and granulocytic and adipose tissue differentation. It was hypothesized that abnormalties in C/EBPalpha function contribute to the development of malignancies in a variety of tissues. To test this, genomic DNA from 408 patient samples and 5 cell lines representing 11 different cancers was screened for mutations in the C/EBPalpha gene. Two silent polymorphisms termed P1 and P2 were present at frequencies of 13.5% and 2.2%, respectively. Of the 12 mutations detected in 10 patients, silent changes were identified in one nonsmall cell lung cancer, one prostate cancer, and one acute myelogenous leukemia (AML) subtype M4. The 9 remaining mutations were detected in 1 of 92 (1.1%) myelodysplastic syndrome (MDS) samples and 6 of 78 (7.7%) AML (AML-M2 and AML-M4) samples. Some mutations truncated the predicted protein with loss of the DNA-binding (basic region) and dimerization (leucine zipper [ZIP]) domains by either deletions or nonsense codons. Also, inframe deletions or insertions in the fork region located between the leucine zipper and basic region, or within the leucine zipper, disrupted the alpha-helical phase of the bZIP domain. The inframe deletion and insertion mutations abrogated the transcriptional activation function of C/EBPalpha on the granulocyte colony-stimulating factor receptor promoter. These mutants localized properly to the nucleus, but were unable to bind to the C/EBP site in the promoter and did not possess dominant-negative activity. The mutations in the MDS patient and one AML-M2 patient were biallelic, indicating a loss of C/EBPalpha function. These results suggest that mutation of C/EBPalpha is involved in specific subtypes of AML and in MDS, but may occur rarely in other types of leukemias or nonhematologic malignancies.

Acute Disease↗
PubMed2002

Relation between resistance of Philadelphia-chromosome-positive acute lymphoblastic leukaemia to the tyrosine kinase inhibitor STI571 and gene-expression profiles: a gene-expression study.

BACKGROUND: The ABL tyrosine kinase inhibitor STI571 is a promising agent for treatment of advanced Philadelphia-chromosome-positive (Ph+) acute lymphoblastic leukaemia. However, resistance to this drug develops within a few months in most patients. We aimed to predict resistance to STI571. METHODS: Total RNA was extracted from 25 bone-marrow samples from 19 patients with Ph+ acute lymphoblastic leukaemia who were enrolled into a phase II study. 17 samples were obtained before STI571 treatment was started: ten from individuals who were classified as good responders to STI571 (sensitive), and seven from individuals who did not to respond to STI571 (primary resistance). Eight samples were obtained from patients during treatment with STI571. We analysed six matched samples, which were obtained before and during treatment with STI571. Oligonucleotide microarray analysis of samples was done with high-density microarrays. FINDINGS: We identified 95 genes whose expression could be used to predict sensitivity of leukaemic cells to STI571. On this basis, all the STI571-sensitive samples could clearly be distinguished from the resistant cases. 56 highly differentially expressed genes were identified in leukaemic cells that were secondarily resistant to STI571. Resistant leukaemic cells expressed high levels of Bruton's tyrosine kinase and two ATP synthetases (ATP5A1 and ATP5C1), and showed significantly reduced expression of the proapoptotic gene BAK1 and the cell-cycle control gene p15 INK4b. INTERPRETATION: We have shown the clinical relevance of gene expression data for the pretreatment assessment of acute lymphoblastic leukaemia. Our results have implications for future clinical studies of tyrosine kinase inhibitors.

Adult↗
PubMed2002

[Therapy of Philadelphia chromosome positive acute lymphatic leukemia (Ph+ ALL) with an inhibitor of abl-tyrosine kinase (Glivec)].

BACKGROUND: Ph+/bcr-abl positive ALL has the worst prognosis of all subgroups of ALL; only a small minority of patients are cured with currently established treatment regimens. The central pathogenetic role of the constitutively activated and deregulated abl-tyrosine kinase that is a direct consequence of the bcr-abl rearrangement opens the possibility of treating this disease using a molecularly targeted approach. The recent development of the selective abl-tyrosine kinase inhibitor Glivec (formerly STI571) opens the opportunity of blocking the signal transduction pathways critically involved in bcr-abl induced leukemogenesis. TREATMENT RESULTS AND CONCLUSIONS: Glivec exerts a significant anti-leukemic effect in patients with Ph+ ALL, with a remarkably favorable toxicity profile. This enables transfer of a subset of the responding patients to a potentially curative allogeneic stem cell transplantation. Despite promising initial therapeutic effects, treatment with Glivec alone is not able to achieve cures in the majority of patients with relapsed or refractory Ph+ ALL. The earlier administration of Glivec in patients with "de novo" ALL as well as combining it with other treatment modalities is likely to improve treatment results. The identification of specific resistance mechanisms towards Glivec should provide valuable information regarding the development of clinical strategies to circumvent resistance. Glivec can already be considered an important element in the treatment of Ph+ ALL, although the most effective ways of employing this novel agent remain to be established.

Antineoplastic Agents↗
PubMed2002

Enhanced production of IL-18 in butyrate-treated intestinal epithelium by stimulation of the proximal promoter region.

Expression of IL-18 in intestinal epithelial cells (IEC) has been implicated in Th1 cell-mediated chronic intestinal inflammation and anti-tumor immunity. However, physiological regulatory factors have not been identified. Besides their effects on proliferation and restitution, immunomodulatory functions have been attributed to short chain fatty acids (SCFA). We investigated the effect of SCFA (butyrate, propionate, acetate) on expression of IL-18 in IEC in vitro and in vivo. Expression of IL-18 mRNA and protein in human carcinoma-derived HT-29 and Caco-2 cells was analyzed by reverse transcription-PCR and Western blot. Transcriptional regulation of IL-18 gene expression was determined by transient transfection of wild-type and mutated IL-18 promoter. Further, in vivo expression of IL-18 in the intestine from butyrate-treated and untreated mice was assessed by immunohistochemistry. IL-18 mRNA and the IL-18 protein were expressed in IEC, while IL-18 secretion was not observed. Butyrate and acetate increased intracellular IL-18 content in a time- and dose-dependent fashion. In contrast to proinflammatory stimuli butyrate potently activated the IL-18 promoter, indicating that IL-18 is regulated at the transcriptional level by SCFA. Furthermore, a 108-bp sequence in the proximal region was identified to be essential for IL-18 promoter activation by butyrate. As proof of principle butyrate effects were confirmed in vivo by demonstration of increased IL-18 protein expression in IEC from butyrate-treated mice. In conclusion, SCFA up-regulate IL-18 protein expression in IEC, suggesting a potential regulatory contribution of these luminal constituents to T cell mediated inflammatory and neoplastic intestinal conditions.

Acetates↗
PubMed2002

Inhibiting effects on the induction of cytotoxic T lymphocytes by dendritic cells pulsed with lysates from acute myeloid leukemia blasts.

Dendritic cells (DCs) were established from 25 patients in complete remission of acute myeloid leukemia (AML). In patients during hematopoietic regeneration following chemotherapy the yield of DC was comparable to that of healthy donors. In patients, more than 2 months after chemotherapy, significantly less DC were generated. Comparison of the antigen-presenting capacity using tetanus toxoid of six AML patients and six healthy volunteers did not show significant differences. In six AML patients, lymphocytes stimulated with blast cell lysate pulsed DC were analyzed for cytotoxic activity against autologous blast cells. 8.4-35.6% of autologous blast cells were lysed by DC stimulated lymphocytes. In three of the six patients maximum lysis of target cells was achieved by unpulsed DC. Thus, it seems that in some patients blast cell lysates mediate inhibitory effects, which may explain to some extend immune escape mechanisms in AML.

Acute Disease↗
PubMed2002

Loss of genomic imprinting of insulin-like growth factor 2 is strongly associated with cellular proliferation in normal hematopoietic cells.

OBJECTIVE: The human insulin-like growth factor 2 (IGF2) gene was thought to be imprinted and expressed only from the paternal allele in normal tissue. MATERIALS AND METHODS: Initially, we analyzed the imprinting status of IGF2 in bone marrow cells from 49 patients with myelodysplastic syndromes (MDS) utilizing the Apa I polymorphism of IGF2. Thirteen bone marrow and 14 peripheral blood samples from normal individuals served as controls. We utilized normal peripheral blood T lymphocytes to examine the relationship between genomic imprinting and cell proliferation. Expression of IGF2 was quantified by real-time PCR and proliferation of T cells was measured by 3H-thymidine incorporation. Furthermore, methylation status of the imprinting controlling region (ICR) was analyzed by subcloning and sequencing of genomic DNA after sodium bisulfite modification. RESULTS: Among 24 patients who were heterozygous for IGF2, loss of imprinting (LOI) occurred in 22 cases (92%). Surprisingly, LOI of IGF2 occurred in the normal bone marrow cells, but the normal peripheral blood cells showed retention of imprinting (ROI). Unstimulated normal T cells showed ROI. After 24 hours of exposure to PHA, these cells changed their IGF2 imprinting status from ROI to LOI. Concomitantly, their IGF2 RNA levels increased up to sixfold and their proliferation increased 10- to 20-fold. In contrast, normal T cells not stimulated with PHA did not develop LOI of IGF2, had negligible levels of IGF2 RNA, and did not increase their proliferation. In unstimulated T cells, the CpG islands of the ICR were completely methylated on one allele and nearly completely unmethylated on the other allele. After PHA stimulation, the CpG islands at the ICR became completely methylated on both alleles. CONCLUSION: LOI of IGF2 is strongly associated with cell proliferation and is not limited to cancer cells.

Bone Marrow Cells↗
PubMed2002

Reciprocal alterations of Th1/Th2 function in gammadelta T-cell subsets of human immunodeficiency virus-1-infected patients.

While T cells that express Vgamma9 as a variable T-cell receptor chain dominate among peripheral blood gammadelta T cells in healthy adults, Vdelta1 cells are the major subpopulation of gammadelta T cells in human immunodeficiency virus (HIV)-infected patients. We used intracellular cytokine staining and flow cytometry to analyse whether an imbalance of T helper 1 (Th1)/T helper 2 (Th2) cytokine patterns, as observed in alphabeta T cells, also occurs in gammadelta T cells. When compared with healthy HIV-negative subjects, HIV+ patients had a decreased number of interferon-gamma (IFN-gamma)+gammadelta T cells, which showed a linear relation to the CD4+ cell count but not to the plasma viral load. Similar results were obtained when Vgamma9 cells were analysed. In contrast, in the Vdelta1 subpopulation, the number of IFN-gamma+ cells was increased in HIV+ donors when compared with healthy subjects. Even though less impressive, the number of interleukin 4 (IL-4)- and IL-10-producing cells was uniformly inversely correlated with the number of tumour necrosis factor-alpha+ and IFN-gamma+ cells. The increased IFN-gamma-producing capacity of Vdelta1 cells might represent a compensatory mechanism for the progressive loss of Vgamma9 gammadelta T cells during the course of HIV infection.

Adolescent↗
PubMed2002

Recent approaches in acute lymphoblastic leukemia in adults.

In the last decades outcome of adult acute lymphoblastic leukemia (ALL) has improved considerably. In large multicenter studies remission rates range from 75% to 89%, and long-term leukemia-free survival (LFS) from 28% to 39%. Major progress has also been made regarding better characterization of subtypes of ALL. Complete diagnostic procedures are essential to identify these subtypes which have significant differences in clinical and laboratory features and prognosis. LFS of > 50% can be expected in favorable subtypes such as T-ALL or mature B-ALL, while LFS of < 20% is expected in Ph/BCR-ABL positive ALL. Prognostic factors can be used for risk stratification and selection of treatment strategies can be adapted to the subtype and relapse risk. This includes measurement of minimal residual disease (MRD) to evaluate individualized treatment strategies adapted to the molecular response. Several new approaches for improvement in chemotherapy and stem cell transplantation (SCT) are under investigation. They include the use of intensified anthracyclines, asparaginase, cyclophosphamide or high-dose cytarabine during induction and intensive rotational chemotherapy during consolidation. Also SCT - mainly from sibling donors - is now part of standard treatment of de novo ALL, although it remains open whether indications should be based on prognostic factors or whether SCT should be offered to all patients with sibling donor. However, substantial progress can only be achieved by new, experimental strategies. These include new approaches for SCT, such as nonmyeloablative SCT, measurement of MRD, causal treatment with molecular targeting, e.g. with kinase inhibitors, and antibody therapy.

Adult↗
PubMed2002

Risk-adapted treatment according to minimal residual disease in adult ALL.

The evaluation of minimal residual disease (MRD) is a new diagnostic method which is applicable in various malignant disorders. Acute lymphoblastic leukaemia (ALL) is a somewhat ideal disease in this respect because >90% of the patients show individual clonal markers and because several methods for MRD evaluation are already established. Futhermore, it was demonstrated that level and course of MRD are significantly correlated with relapse risk in childhood and in adult ALL. In clinical practice MRD evaluation may serve for several purposes such as follow-up of individual course of disease, identification of new prognostic factors or evaluation of single treatment elements. We discuss these options as well as general considerations for MRD-based risk stratification and treatment options for risk groups. Practical applications are analysed because prospective MRD-based clinical trials have been recently started. Finally, future options for application of MRD evaluation and also limitations and pitfalls of this method are reviewed.

Age Factors↗