W Verbeek

Klinikum Braunschweig, Brunswyck, Lower Saxony, Germany

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Publications (32)156.93 Total impact

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    ABSTRACT: Epigenetic changes play an important role in leukemia pathogenesis. DNA methylation is among the most common alterations in leukemia. The potential role of DNA methylation as a biomarker in leukemia is unknown. In addition, the lack of molecular markers precludes minimal residual disease (MRD) estimation for most patients with hematologic malignancies. We analyzed the potential of aberrant DNA promoter methylation as a biomarker for MRD in acute leukemias. Quantitative real-time PCR methods with bisulfite-modified DNA were established to quantify MRD based on estrogen receptor alpha (ERalpha) and/or p15(INK4B) methylation. Methylation analyses were done in >370 DNA specimens from 180 acute leukemia patients and controls. Methylation of ERalpha and/or p15(INK4B) occurred frequently and specifically in acute leukemia but not in healthy controls or in nonmalignant hematologic diseases. Aberrant DNA methylation was detectable in >20% of leukemia patients during clinical remission. In pediatric acute lymphoblastic leukemia, methylation levels during clinical remission correlated closely with T-cell receptor/immunoglobulin MRD levels (r = +0.7, P < 0.01) and were associated with subsequent relapse. In acute myelogenous leukemia patients in clinical remission, increased methylation levels were associated with a high relapse risk and significantly reduced relapse-free survival (P = 0.003). Many patients with acute leukemia in clinical remission harbor increased levels of aberrant DNA methylation. Analysis of methylation MRD might be used as a novel biomarker for leukemia patients' relapse risk.
    Cancer Research 02/2007; 67(3):1370-7. · 8.65 Impact Factor
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    ABSTRACT: Nongestational choriocarcinomas are rare tumors. In the gastrointestinal tract, they are characterized by a biphasic tumor growth with separated areas of adenocarcinomatous and choriocarcinomatous differentiation. We here report a case of a combined adenocarcinoma-choriocarcinoma of the rectum. The tumor showed an aggressive clinical behavior with metastasis to the liver and lungs. A transient partial remission was achieved after 4 cycles of cisplatinum, etoposide, and ifosfamide chemotherapy, with normalization of serum beta-human chorionic gonadotropin levels. At this time, viable residual choriocarcinoma cells were found in surgically resected lung metastasis. The patient succumbed 8 months after initial diagnosis to a rapid abdominal relapse. We used comparative genomic hybridization (CGH) and fluorescence in situ hybridization to elucidate the genetic relationship of adenocarcinoma and choriocarcinoma in this neoplasm. We found genetic changes characteristic for colorectal adenocarcinomas, a loss of chromosomal regions 8p21-pter as well as 18q21-pter, and a gain of 5p and 20q, in both tumor parts. This provides evidence for the common origin of both components. A differential pattern of additional genetic changes suggests a clonal evolution from a common ancestor cell. In contrast to findings from a comparative study on a choriocarcinoma of the renal pelvis, we did not find an amplification of the germ cell cancer-associated chromosomal region 12p11.2-p12.1 in the areas of choriocarcinoma but found instead a loss of Xp11.3-pter. To our knowledge, this is the first report of a CGH comparison of the adenocarcinomatous and choriocarcinomatous tumor parts in a nongestational choriocarcinoma of the gastrointestinal tract.
    Human Pathlogy 12/2004; 35(11):1427-30. · 2.84 Impact Factor
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    ABSTRACT: Internal tandem duplications (ITDs) of the juxtamembrane region of the FLT3 tyrosine kinase receptor are the most frequent genetic alterations in acute myeloid leukemia (AML). The presence of this mutation has been recognized as an independent poor prognostic factor. In this study, we compared the FLT3 mutational status between diagnosis and subsequent relapses in 31 patients with AML. At diagnosis, seven patients were identified to contain FLT3-ITD mutations and one patient to harbor the D835 mutation. Five patients remained FLT3-ITD positive throughout the disease course (+/+). Three patients lost the FLT3 gene mutation at first (one FLT3-ITD, one D835 mutation), or second relapse (one FLT3-ITD) (+/-). One additional patient lost a small FLT3-ITD positive clone at relapse and at the same time gained an apparently unrelated FLT3-ITD positive clone. One patient without FLT3 mutation at diagnosis relapsed with an FLT3-ITD mutation (-/+). A shorter median duration of first remission (6 months versus 11.5 months) and a higher relapse rate after salvage therapy (e.g. allogeneic peripheral blood stem cell transplantation) resulted in a lower leukemia-free survival in the FLT3 mutated group (11% versus 31%). The loss of a clone with a mutation in the FLT3 gene at relapse did not improve the prognosis.
    Leukemia Research 11/2004; 28(10):1069-74. · 2.76 Impact Factor
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    ABSTRACT: Immunosuppression has recently been proposed for low-risk myelodysplastic syndromes (MDS) to reverse bone marrow failure by inhibiting intramedullary secretion of proapoptotic cytokines. We treated 35 MDS patients (24 refractory anaemia (RA), 10 RA with excess blasts and one chronic myelomonocytic leukaemia) with either horse antithymocyte globulin 15 mg/kg/day or rabbit antithymocyte globulin 3.75 mg/kg/day, each for 5 days. Median age was 63 years (range: 41-75). After 1 to 34+ months of follow-up (mean: 15+), four patients experienced complete haematological responses (CR), six good responses (GR) and two minor responses. All CRs and GRs occurred in patients with RA, in whom both horse and rabbit ATG yielded five responses out of 12 (42%). Time to response varied between 1 and 10 (mean: 3) months. The median duration of response was 9+ (1-17+) months; five patients are in continuing response. In all, 23 patients suffered side effects > degrees II WHO (the degree of toxicity encountered according to the internationally accepted WHO toxicity grading); one patient died 2 weeks after rabbit ATG from rhinocerebral mucormycosis. Parameters that correlated with response were duration of disease and RA subgroup. In our experience, immune-modulating therapy with either horse or rabbit ATG is feasible in patients with RA and short duration of disease.
    Leukemia 04/2004; 18(3):460-5. · 10.16 Impact Factor
  • Pathology Research and Practice - PATHOL RES PRACT. 01/2004; 200(4):323-323.
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    ABSTRACT: Transcription factor CCAAT/enhancer binding protein alpha (C/EBPalpha) is mutated in 6-10% of patients with acute myeloid leukaemia (AML). Recently, we reported the emergence of an N-terminal C/EBPalpha mutation after chemotherapy in a patient with secondary AML. The clone carrying the mutation became the dominant clone at relapse. This observation prompted us to compare the C/EBPalpha mutational status of 26 de novo non-core binding factor AML patients at diagnosis and at relapse after induction and consolidation chemotherapy. Four mutations in the C/EBPalpha gene were identified in two out of 26 patients. In both these cases, a biallelic mutation was present at diagnosis and at relapse: an amino-terminal frameshift mutation and a mutation of the fork/leucine finger 1 region. In patient 1, the amino-terminal frameshift mutation was duplicated and found on both alleles at relapse. In patient 2, the amino-terminal frameshift mutation and a mutation in the fork region were found either alone or combined on the same allele, suggesting a subclone formation. None of the patients without a C/EBPalpha mutation at diagnosis showed a mutation at relapse. This is the first report of an evolution of the C/EBPalpha gene between diagnosis and relapse in AML.
    British Journal of Haematology 12/2003; 123(3):413-9. · 4.94 Impact Factor
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    ABSTRACT: Recently, mutations in the transcription factor CCAAT/ enhancer binding protein alpha (C/EBPalpha) have been described in acute myeloid leukemia (AML). We performed a mutational analysis of the C/EBPalpha gene in the myelodysplastic syndromes and AML with antecedent MDS. No mutations were found in patients with refractory anemia (0/27), refractory anemia with ringed sideroblasts (0/7), refractory anemia with excess of blasts (RAEB 0/16) or chronic myelomonocytic leukemia (CMML 0/5). One out of 13 patients with RAEB-T/AML secondary to MDS showed a mutation in the C/EBPalpha gene. In this patient a 4 bp insertion disrupted codon 69 in one allele. This novel +1 frame shift is predicted to result in a truncated protein of 107 amino acids. However, the dominant protein translated was the C/EBPalpha isoform p30, which was previously shown to inhibit the DNA-binding and transactivation properties of C/EBPalpha p42. Interestingly this mutation could not be detected at diagnosis in the initial RAEB and RAEB-T stage. The mutation appeared at relapse after chemotherapy for RAEB-T. We conclude that the C/EBPalpha mutation was not essential for the initial blast accumulation. The emergence of a bast clone carrying a C/EBPalpha mutation at relapse indicates that this mutation may confer a growth advantage in a myeloid cell with an established differentiation block.
    Leukemia 03/2003; 17(2):343-9. · 10.16 Impact Factor
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    ABSTRACT: To evaluate a potential therapeutic role for megakaryocyte growth and development factor (MGDF) in myelodysplastic syndromes (MDS) we compared the in vitro response of normal and myelodysplastic megakaryopoiesis to MGDF on bone marrow mononuclear cells from nine MDS patients and four healthy donors in a short term liquid culture system. The cells were incubated with MGDF alone (1 ng/ml, 10 ng/ml and 100 ng/ml) and in combination with 20 ng/ml stem cell factor, 2 U/ml erythropoietin (EPO) and 100 ng/ml interleukin-3 (IL-3). Cytospins were prepared after 4 days and 10 days for CD61 APAAP staining. In addition, the ploidy of propidium iodide stained CD61 positive cells were detected by flow cytometry. The CD61+ cell number significantly increased (13-fold after 4 days, 56-fold after 10 days of culture) when MGDF (100 ng/ml) was added to the normal bone marrow (NBM) cultures (P=0.0003; P=0.0001). In the MDS cultures the absolute number of endomitotic cells as well as the percentage of polyploid cells remained significantly lower than in NBM after 10 days (P=0.0001). The effect of MGDF on polyploidization of MDS cells was significantly dose dependent (P=0.0051). We found no correlation between peripheral platelet count, cellularity of the bone marrow, number of bone marrow megakaryocytes or FAB-subtype and response to MGDF. Additional administration of IL-3 resulted in a left-shift of megakaryopoiesis in both groups. Even though the response of myelodysplastic megakaryocytic progenitors to MGDF shows inter-individual variations, it is significantly impaired overall. Our data suggest that higher doses of MGDF may be able to ameliorate thrombocytopenia in a subgroup of MDS patients.
    Annals of Hematology 01/2003; 81(12):695-700. · 2.87 Impact Factor
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    ABSTRACT: Human C/EBPepsilon is a recently cloned member of the C/EBP family of transcriptional factors. Previous studies demonstrated that the expression of this gene is tightly regulated in a tissue-specific manner; it is expressed almost exclusively in myeloid cells. To understand the mechanism by which the expression of C/EBPepsilon gene is controlled, we cloned a large genomic region surrounding the C/EBPepsilon gene and performed a DNase I hypersensitivity analysis of this locus. These sites probably represent areas of binding of proteins modulating gene transcription. Hypersensitive (HS) regions in 30 kb of DNA surrounding the C/EBPepsilon gene were examined in C/EBPepsilon high-expressing (NB4, HL-60), low-expressing (Jurkat), very-low-expressing (KG-1), and non-expressing (K562) hematopoietic cells as well as in non-hematopoietic-non-expressing cells (MCF-7, DU 145, PC-3). Three HS sites were detected near the first exon of C/EBPepsilon gene. They were found only in hematopoietic cells and were especially prominent in C/EBPepsilon expressing cells, suggesting that these sites play an important role in transcribing the gene. These hypersensitive bands did not change when the cells were cultured with retinoids. Gel-shift assays using 200 bp of nucleotide sequences that encompassed the hypersensitive sites and nuclear extracts from NB4 and Jurkat cells (C/EBPepsilon expressing) as well as K562 and MCF-7 cells (non-expressing) showed different retarded bands on gel electrophoresis. A fourth HS site, located about 11 kb upstream of exon 1, was found only in cells highly expressing C/EBPepsilon. Two sites, one about 4.5 kb upstream of exon 1 and another about 8.5 kb downstream of exon 2, were positive only in non-expressing cell lines, suggesting that repressors may bind in these areas. Taken together, we have found six specific DNase I hypersensitive sites in the region of C/EBPepsilon that may be involved in regulating transcription of this gene.
    Leukemia Research 12/2001; 25(11):981-95. · 2.76 Impact Factor
  • W Verbeek, A Ganser
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    ABSTRACT: Myelodysplastic syndromes (MDS) comprise a heterogenous group of myeloid stem cell disorders characterized by peripheral cytopenias and dysplasia of bone marrow progenitor cells. A clonal evolution can result in progressive bone marrow failure and transformation towards acute myelogenous leukemia. A patient's prognosis as estimated by the International Prognostic Scoring System, age, and co-morbidities have to be considered for the selection of various treatment options. Although supportive care remains standard therapy for low-risk MDS, a number of treatment approaches that aim to improve cytopenia in transfusion-dependent patients are currently under investigation. Among others, immunosuppressive, anticytokine, and antiangiogenic therapy will be discussed. The demethylating agents 5-azacytidine and decitabine are promising for the treatment of elderly patients with high-risk MDS. An increase of the upper age limit for allogeneic stem cell transplantation, the only curative treatment option, by the development of dose-reduced conditioning regimens may have implications for the treatment of MDS patients in the future.
    Annals of Hematology 10/2001; 80(9):499-509. · 2.87 Impact Factor
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    ABSTRACT: CCAAT/enhancer binding protein epsilon (C/EBPepsilon) is essential for terminal granulocytic differentiation. Its expression begins at the transition between the proliferative and non-proliferative compartments of myelopoiesis. We studied the effect of targeted disruption of the C/EBPepsilon gene on murine myeloid proliferation and apoptosis. Bone marrow cellularity of C/EBPepsilon -/- and wild-type mice was 95% and 65%, respectively. The C/EBPepsilon -/- mice had an expansion in the number of their CFU-GM/femur. The number of myeloid committed progenitor cells in the peripheral blood and the spleen of these mice was also increased. Bromodeoxyuridine (BrDU) pulse labeling studies demonstrated that the fraction of actively proliferating cells was two-fold higher in the bone marrow of C/EBPepsilon -/- mice. However, the number of myeloid colonies arising from purified Sca-1+/lin- early hematopoietic progenitor cells and from bone marrow mononuclear cells grown in different cytokine combinations was not significantly different between wild-type and knock-out mice. Also, long-term marrow growth, and CFU were not different between the wild-type and C/EBPepsilon -/- mice. The sensitivity to induction of apoptosis in the committed progenitor cell compartment after either withdrawal of growth factor or brief exposure to etoposide was normal. However, Gr-1 antigen-positive C/EBPepsilon -/- granulocytic cells showed an increased rate of apoptosis in comparison to their wild-type counterparts. In summary, the myeloid compartment appears to be expanded in mice lacking C/EBPepsilon. However, this is not the consequence of an intrinsic myeloproliferation but due to an indirect, possibly cytokine-mediated stimulation of myelopoiesis in vivo. C/EBPepsilon may have a role in the inhibition of apoptosis in maturing granulocytic cells.
    Leukemia 02/2001; 15(1):103-11. · 10.16 Impact Factor
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    ABSTRACT: Human C/EBPε is a recently cloned member of the C/EBP family of transcriptional factors. Previous studies demonstrated that the expression of this gene is tightly regulated in a tissue-specific manner; it is expressed almost exclusively in myeloid cells. To understand the mechanism by which the expression of C/EBPε gene is controlled, we cloned a large genomic region surrounding the C/EBPε gene and performed a DNase I hypersensitivity analysis of this locus. These sites probably represent areas of binding of proteins modulating gene transcription. Hypersensitive (HS) regions in 30 kb of DNA surrounding the C/EBPε gene were examined in C/EBPε high-expressing (NB4, HL-60), low-expressing (Jurkat), very-low-expressing (KG-1), and non-expressing (K562) hematopoietic cells as well as in non-hematopoietic-non-expressing cells (MCF-7, DU 145, PC-3). Three HS sites were detected near the first exon of C/EBPε gene. They were found only in hematopoietic cells and were especially prominent in C/EBPε expressing cells, suggesting that these sites play an important role in transcribing the gene. These hypersensitive bands did not change when the cells were cultured with retinoids. Gel-shift assays using 200 bp of nucleotide sequences that encompassed the hypersensitive sites and nuclear extracts from NB4 and Jurkat cells (C/EBPε expressing) as well as K562 and MCF-7 cells (non-expressing) showed different retarded bands on gel electrophoresis. A fourth HS site, located about 11 kb upstream of exon 1, was found only in cells highly expressing C/EBPε. Two sites, one about 4.5 kb upstream of exon 1 and another about 8.5 kb downstream of exon 2, were positive only in non-expressing cell lines, suggesting that repressors may bind in these areas. Taken together, we have found six specific DNase I hypersensitive sites in the region of C/EBPε that may be involved in regulating transcription of this gene.
    Leukemia Research - LEUK RES. 01/2001; 25(11):981-995.
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    ABSTRACT: CCAAT/enhancer binding protein epsilon (C/EBPε) is essential for terminal granulocytic differentiation. Its expression begins at the transition between the proliferative and non-proliferative compartments of myelopoiesis. We studied the effect of targeted disruption of the C/EBPε gene on murine myeloid proliferation and apoptosis. Bone marrow cellularity of C/EBPε −/− and wild-type mice was 95% and 65%, respectively. The C/EBPε −/− mice had an expansion in the number of their CFU-GM/femur. The number of myeloid committed progenitor cells in the peripheral blood and the spleen of these mice was also increased. Bromodeoxyuridine (BrDU) pulse labeling studies demonstrated that the fraction of actively proliferating cells was two-fold higher in the bone marrow of C/EBPε −/− mice. However, the number of myeloid colonies arising from purified Sca-1+/lin− early hematopoietic progenitor cells and from bone marrow mononuclear cells grown in different cytokine combinations was not significantly different between wild-type and knock-out mice. Also, long-term marrow growth, and CFU were not different between the wild-type and C/EBPε −/− mice. The sensitivity to induction of apoptosis in the committed progenitor cell compartment after either withdrawal of growth factor or brief exposure to etoposide was normal. However, Gr-1 antigen-positive C/EBPε −/− granulocytic cells showed an increased rate of apoptosis in comparison to their wild-type counterparts. In summary, the myeloid compartment appears to be expanded in mice lacking C/EBPε. However, this is not the consequence of an intrinsic myeloproliferation but due to an indirect, possibly cytokine-mediated stimulation of myelopoiesis in vivo. C/EBPε may have a role in the inhibition of apoptosis in maturing granulocytic cells.
    Leukemia. 01/2001; 15(1):103-111.
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    ABSTRACT: Platelet production is primarily regulated by the thrombopoietic cytokine thrombopoietin (TPO). In most cases thrombopoietin serum levels are determined by the rate of c-mpl receptor-mediated degradation after TPO uptake into platelets and megakaryocytes. The contribution of increased TPO protein synthesis by a translational mechanism was recently appreciated as the cause for hereditary thrombocythemia and will have to be elucidated in other conditions of thrombocytosis in association with increased TPO levels.
    Current Opinion in Hematology 06/2000; 7(3):143-9. · 4.11 Impact Factor
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    ABSTRACT: Cyclin A1 differs from other cyclins in its highly restricted expression pattern. Besides its expression during spermatogenesis, cyclin A1 is also expressed in hematopoietic progenitor cells and in acute myeloid leukemia. We investigated mechanisms that might contribute to cyclin A1 expression in hematopoietic cells. Comparison of cyclin A1 and cyclin A promoter activity in adherent and myeloid leukemia cell lines showed that the cyclin A1 promoter is preferentially active in myeloid cell lines. This preferential activity was present in a small, 335-bp cyclin A1 promoter fragment that contained several potential c-myb binding sites. Coexpression of a c-myb expression vector with the cyclin A1 promoter constructs significantly increased the reporter activity in adherent CV-1 as well as in myeloid U937 cells. Gel-shift assays demonstrated that c-myb could bind to the cyclin A1 promoter at a binding site located near the transcription start site. Site-directed mutagenesis of this site decreased promoter transactivation by 50% in both KCL22 cells that express high levels of c-myb and in CV-1 cells that were transfected with c-myb. In addition, transfection of primary human embryonic fibroblasts with a c-myb expression vector led to induction of the endogenous cyclin A1 gene. Taken together, c-myb can directly transactivate the promoter of cyclin A1, and c-myb might be involved in the high-level expression of cyclin A1 observed in acute myeloid leukemia. These findings suggest that c-myb induces hematopoiesis-specific mechanisms of cell cycle regulation.
    Blood 01/2000; 94(12):4255-62. · 9.06 Impact Factor
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    ABSTRACT: Peroxisome proliferator activated receptor gamma (PPARgamma) plays a central role in the process of adipocyte differentiation. This receptor and its heterodimeric partner, retinoid X receptor alpha (RXRalpha), form a DNA-binding complex that regulates transcription of adipocyte-specific genes. Troglitazone, an antidiabetic drug, has recently been identified as a synthetic ligand for PPARgamma. We studied the effects of troglitazone on proliferation and differentiation of normal and malignant hematopoietic cells. Expression of PPARgamma was easily detectable by Western blot analyses in all five myeloid leukemia cell lines. Troglitazone alone (10-5 M) did not induce differentiation in any of the cell lines; however, this compound suppressed the clonal growth (10-75% of inhibition) of all five myeloid leukemia cell lines. Myelomonocytic U937 cells, which were the most responsive to the growth suppressing effects of troglitazone, were arrested in the G1 phase of the cell cycle when cultured with this compound. Simultaneous treatment of myeloid leukemia cell lines with both troglitazone and a ligand that specifically binds either RXR (LG100268), or retinoic acid receptors (RAR, ATRA, ALART1550), or both (9-cis RA) resulted in additive suppression of clonal growth. In summary, our studies showed that troglitazone when combined with a retinoid was a moderately potent inhibitor of clonogenic growth of acute myeloid leukemia cells.
    International Journal of Oncology 12/1999; 15(5):1027-31. · 2.66 Impact Factor
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    ABSTRACT: Targeted mutation of the myeloid transcription factor C/EBPepsilon in mice results in gram-negative septic death at 3 to 5 months of age. This study defines the underlying molecular defects in their terminal granulocytic differentiation. The mRNA for the precursor protein of the cathelin-related antimicrobial peptides was almost completely absent in the bone marrow cells of C/EBPepsilon-/- mice. This finding may help explain their susceptibility to gram-negative sepsis, because both are bacteriocidal peptides with potent activity against gram-negative bacteria. Superoxide production was found to be reduced in both granulocytes and monocytes of C/EBPepsilon-/- mice. While gp91 phox protein levels were normal, p47phox protein levels were considerably reduced in C/EBPepsilon -/- granulocytes/monocytes, possibly limiting the assembly of the NADPH oxidase. In addition, expression of mRNA of the secondary and tertiary granule proteins, lactoferrin and gelatinase, were not detected, and levels of neutrophil collagenase mRNA were reduced in bone marrow cells of the knock-out mice. The murine lactoferrin promoter has a putative C/EBP site close to the transcription start site. C/EBPepsilon bound to this site in electromobility shift assay studies and mutation of this site abrogated binding to it. A mutation in the C/EBP site reduced the activity of the promoter by 35%. Furthermore, overexpression of C/EBPepsilon in U937 cells increased the activity of the wild-type lactoferrin promoter by 3-fold. In summary, our data implicate C/EBPepsilon as a critical factor of host antimicrobial defense and suggests that it has a direct role as a positive regulator of expression of lactoferrin in vivo.
    Blood 12/1999; 94(9):3141-50. · 9.06 Impact Factor
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    ABSTRACT: C/EBPepsilon is essential for granulocytic differentiation. We investigated the role of C/EBPepsilon in the transcriptional activation of various myeloid-specific genes. We found that two C/EBPepsilon isoforms, p32 and p30, possessing transcriptional activation domains were coexpressed in myeloid cells. Interestingly, isoform C/EBPepsilon p30 but not p32 was differentially upregulated in NB-4 promyelocytic leukemia cells treated with retinoids. Both isoforms bound specifically to C/EBP sites in myeloid promoters. The kd for C/EBPepsilon binding to the C/EBP site of the neutrophil elastase promoter was 4.2 nmol/L. In transfection assays using the nonhematopoietic cell line, CV-1, the p32 isoform activated promoters from the myeloid-specific mim-1, neutrophil elastase, and granulocyte colony-stimulating factor (G-CSF) receptor genes by 2.5-, 1.8-, and 1.6-fold, respectively. The p30 isoform lacked significant transcriptional activity, suggesting that other hematopoietic-specific factors were required for its function. Consistent with this prediction, transfections into the hematopoietic cell line Jurkat showed a 9.0- and 2.5-fold activation of the mim-1 promoter by the p32 and p30 isoforms, respectively. The additional 32 NH2-terminal residues made p32 a significantly more potent transcriptional activator than p30. T lymphoblasts (Jurkat cells) and immature myeloid cells (eg, Kcl22 cells) expressed high levels of the c-myb hematopoietic transcription factor. Cotransfection of c-myb with either the p32 or p30 isoform of C/EBPepsilon in CV-1 cells cooperatively transactivated the mim-1 promoter by 20- and 16-fold, respectively, and the neutrophil elastase promoter by 10-and 7-fold, respectively. Pulldown assays showed that each C/EBPepsilon isoform interacted directly with the DNA binding domain of the c-myb protein. Further studies showed that Kcl22 myeloid cells only contained active C/EBPepsilon, but not C/EBPalpha, C/EBPbeta, or C/EBPdelta. A mutation of the C/EBP site in the neutrophil elastase promoter markedly decreased the transactivation of the promoter in Kcl22 myeloblasts. These results demonstrate a role for C/EBPepsilon in regulating myeloid promoters, such as neutrophil elastase, probably through a direct interaction with c-myb.
    Blood 06/1999; 93(10):3327-37. · 9.06 Impact Factor
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    ABSTRACT: Cyclin A1 is a recently cloned cyclin with high level expression in meiotic cells in the testis. However, it is also frequently expressed at high levels in acute myeloid leukemia. To elucidate the regulation of cyclin A1 gene expression, we cloned and analyzed the genomic structure of cyclin A1. It consists of 9 exons within 13 kilobase pairs. The TATA-less promoter initiates transcription from several start sites with the majority of transcripts beginning within a 4-base pair stretch. A construct containing a fragment from -190 to +145 showed the highest transcriptional activity. Transfection of cyclin A1 promoter constructs into S2 Drosophila cells demonstrated that Sp1 is essential for the activity of the promoter. Sp1, as well as Sp3, bound to four GC boxes between nucleotides -130 and -80 as observed by gel shift analysis. Mutations in two or more of the four GC boxes decreased promoter activity by >80%. The promoter was found to be cell cycle-regulated with highest activities found in late S and G2/M phase. Further analyses suggested that cell cycle regulation was accomplished by periodic repression of the GC boxes in G1 phase. Taken together, our data show that cyclin A1 promoter activity critically depends on four GC boxes, and members of the Sp1 family appear to be involved in directing expression of cyclin A1 in both a tissue- and cell cycle-specific manner.
    Journal of Biological Chemistry 04/1999; 274(16):11220-8. · 4.65 Impact Factor
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    ABSTRACT: A prospective, randomized, double-blind placebo-controlled trial was designed to evaluate the impact of granulocyte/macrophage-colony-stimulating factor (GM-CSF) on the efficacy of sequential high-dose cytosine arabinoside/mitoxantrone chemotherapy (S-HAM) in adult patients with high-risk myelodysplastic syndromes (MDS). GM-CSF or placebo was given subcutaneously once daily at a dose of 250 microg/m2, starting 48 h prior to chemotherapy, and continued until neutrophil recovery. Owing to high toxicity and slow patient recruitement the study was closed and unblinded after 31 patients had been enrolled; 15 were randomized to receive placebo and 16 to receive GM-CSF. A total of 29 patients were evaluable for response; their median age was 57 years. Ten patients achieved a complete remission (34.5%), 9 patients had persistent MDS (31%), 10 patients died within 6 weeks after the onset of treatment (early death) (34.5%). The median remission duration was 190 days (range: 2.5-45 months). Among the 29 evaluable patients no significant differences could be found between the two study arms regarding complete remission rate [GM-CSF: 31% (5/16) versus placebo: 38% (5/13) P = 0.45], rate of persistent MDS [GM-CSF: 25% (4/16) versus 38% (5/13) P = 0.35), early death rate [44% (7/16) versus 23% (3/13) P = 0.22] and remission duration (GM-CSF: 87 days versus placebo 221 days). Duration of granulocytopenia (median: 33 days with GM-CSF) versus 35 days with placebo) and frequency of infectious episodes were not significantly influenced by GM-CSF. The small number of patients finally analyzed means that no definite conclusions about the effect of GM-CSF can be reached.
    Journal of Cancer Research and Clinical Oncology 02/1999; 125(6):369-74. · 2.91 Impact Factor

Publication Stats

640 Citations
156.93 Total Impact Points

Institutions

  • 2004
    • Klinikum Braunschweig
      Brunswyck, Lower Saxony, Germany
  • 2001–2004
    • Hannover Medical School
      Hanover, Lower Saxony, Germany
  • 1997–2001
    • Cedars-Sinai Medical Center
      • • Division of Hematology and Oncology
      • • Cedars Sinai Medical Center
      • • Department of Medicine
      Los Angeles, CA, United States
  • 1995–2000
    • Universitätsmedizin Göttingen
      • • Division of Legal Medicine
      • • Department of Hematology and Oncology
      Göttingen, Lower Saxony, Germany
  • 1999
    • Hiroshima University
      • Medical Research Institute for Bio Functions
      Hiroshima-shi, Hiroshima-ken, Japan
  • 1998–1999
    • University of California, Los Angeles
      • Department of Medicine
      Los Angeles, CA, United States
  • 1995–1997
    • Georg-August-Universität Göttingen
      • Faculty of Medicine
      Göttingen, Lower Saxony, Germany