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Michael Lübbert

Publications and source records attributed to Michael Lübbert.

9 recordsLinked to original sources
PubMed2003

Upstream and downstream targets of RUNX proteins.

In recent years, the in vivo role of the three members of the RUNX family of transcription factors has in part been elucidated. While Runx1 is essential for mature haematopoiesis and Runx2 for osteochondrogenesis, Runx3 has a function in the nervous system. Translocations and mutations affecting the RUNX1 gene are clearly implicated in leukemogenesis whereas recent data suggest that changed expression levels of RUNX3 may be involved in gastric carcinogenesis. Germ line mutations in RUNX2 have been identified in patients with an autosomal dominant skeletal disorder, cleidocranial dysplasia. While a number of pathways have been delineated that regulate RUNX activity, transcription factors binding to RUNX promoters are only beginning to be identified. A growing number of genes have been characterised that are being regulated in their transcriptional activity by different RUNX proteins. Whether a particular RUNX protein specifically targets a defined subset of downstream genes or whether there is some redundancy as to which RUNX protein activates which target promoter remains to be elucidated.

Animals↗
PubMed2003

Side-population cells from different precursor compartments.

The rapid efflux of the fluorescent DNA-binding dye Hoechst 33342 identifies a rare, so-called side population (SP), which rapidly expels the dye, can reconstitute the bone marrow (BM) of lethally irradiated mice, and has proven negative for most lineage markers including CD34. Because SP cells from human cell sources, such as mobilized peripheral blood [apheresis products (AP)], cord blood (CB), or BM have not been extensively characterized to date, we sought to analyze SP cells from various cell sources. We detected murine SP cells with a median frequency of 0.04% (n = 23) and a 52-fold colony-forming units (CFU) increase compared to unsorted cells (p = 0.028). The median frequency of human SP cells was 0.02% (n = 90), with highest numbers in donor AP, and lower in CB and BM. Human SP cells were mostly CD34(-) and lineage marker-negative. These showed no enrichment in CFU before expansion; however, they displayed a CFU increase after 5-7 days of cytokine-supported suspension culture (10.7-fold at day 5, 7.2-fold at day 7; n = 17) that was significant compared to both input (day 0) SP and to non-SP cells before and after expansion (p < 0.05). SP cells demonstrated a significant long-term culture-initiating cell (LTC-IC) increase of 167-fold (n = 17) as compared to non-SP cells (p = 0.002), with the highest numbers from AP specimens. We conclude that human primitive hematopoietic cells can be isolated via Hoechst staining and that SP cells of various human sources show substantial differences and represent a rare CD34(-) population with stem cell potential.

Animals↗
PubMed2003

CD34- hematopoietic stem cells: current concepts and controversies.

Recent data have suggested that human CD34(-) hematopoietic stem cells (HSCs) exist, challenging the concept that HSCs necessarily and exclusively express the CD34 antigen. In mice, quiescent HSCs have been shown to be mostly CD34(-), but as a consequence of 5-fluorouracil treatment or cytokine stimulation, differentiate into CD34(+) cells. Of particular interest is a novel, specific marker to identify HSCs, namely the Hoechst dye efflux property, with which a distinct side population (SP) is identified. These SP cells are mostly CD34(-), highly enriched for long-term repopulating cells, and durably engraft in sublethally irradiated non-obese diabetic/severe combined immunodeficient mice. Using a semiquantitative reverse transcription-polymerase chain reaction, one of the ATP-binding cassette (ABC) transporters, the breast cancer resistance protein (Bcrp) or ABC transporter G2 (ABCG2), was found to be highly expressed in SP cells as well as other primitive HSCs and to sharply drop with hematopoietic differentiation. Enforced expression of the ABCG2 cDNA resulted in a robust SP phenotype and a reduction in hematopoietic maturation. These data suggest that the Bcrp/ABCG2 gene contributes importantly to the generation of the SP phenotype, which allows for the selection of immature, pluripotent HSCs. The isolation of Bcrp/ABCG2(+) cells appears to be an attractive tool to analyze and characterize HSCs, and may eventually allow for the purification of these cells for clinical purposes. In this review, current concepts on murine and human CD34(-) HSCs and their relationship with CD34(+) HSCs are discussed.

Animals↗
PubMed2002

Demethylation of a hypermethylated P15/INK4B gene in patients with myelodysplastic syndrome by 5-Aza-2'-deoxycytidine (decitabine) treatment.

p16 and p15, 2 inhibitors of cyclin-dependent kinases, are frequently hypermethylated in hematologic neoplasias. Decitabine, or 5-Aza-2'-deoxycytidine, reverts hypermethylation of these genes in vitro, and low-dose decitabine treatment improves cytopenias and blast excess in ~50% of patients with high-risk myelodysplastic syndrome (MDS). We examined p15 and p16 methylation status in bone marrow mononuclear cells from patients with high-risk MDS during treatment with decitabine, using a methylation-sensitive primer extension assay (Ms-SNuPE) to quantitate methylation, and denaturing gradient gel electrophoresis (DGGE) and bisulfite-DNA sequencing to distinguish individually methylated alleles. p15 expression was serially examined in bone marrow biopsies by immunohistochemistry. Hypermethylation in the 5' p15 gene region was detected in 15 of 23 patients (65%), whereas the 5' p16 region was unmethylated in all patients. Among 12 patients with hypermethylation sequentially analyzed after at least one course of decitabine treatment, a decrease in p15 methylation occurred in 9 and was associated with clinical response. DGGE and sequence analyses were indicative of hypomethylation induction at individual alleles. Immunohistochemical staining for p15 protein in bone marrow biopsies from 8 patients with p15 hypermethylation revealed low or absent expression in 4 patients, which was induced to normal levels during decitabine treatment. In conclusion, frequent, selective p15 hypermethylation was reversed in responding MDS patients following treatment with a methylation inhibitor. The emergence of partially demethylated epigenotypes and re-establishment of normal p15 protein expression following the initial decitabine courses implicate pharmacologic demethylation as a possible mechanism resulting in hematologic response in MDS.

Adult↗
PubMed2002

p53 Germline mutation in a patient with Li-Fraumeni Syndrome and three metachronous malignancies.

PURPOSE: Germline mutations of the p53 coding region are present in approximately 50-70% of patients with Li-Fraumeni Syndrome (LFS), a rare hereditary disorder of familial and intraindividual clustering of different malignancies such as sarcoma (index tumor), breast cancer, brain tumors, leukemias, and adrenocortical carcinomas, the latter usually in young children. Both onset and spectrum of malignancies in individuals with LFS are thus heterogenous and may, less frequently, also include other epithelial and mesenchymal tumors. A 32-year-old female presented for genetic counseling with a history of leiomyosarcoma at age 22, malignant melanoma (a rare component of LFS) at age 26, and breast cancer at age 30. All three tumors had been treated surgically. Astrocytoma and breast cancer, respectively, had been diagnosed in her brother and mother before age 30. Other malignancies diagnosed early in life in relatives of the mother were: prostate cancer, stomach cancer, and carcinoma of the larynx. METHODS: Upon written informed consent, DNA was extracted from peripheral blood mononuclear cells of the proband, and p53 exons 4-8 analyzed for mutations by SSCP and DNA sequencing. RESULTS: A G:C to A:T mutation at codon 175 of p53 resulting in an arginine --> histidine substitution was detected, confirming the clinical diagnosis of LFS. CONCLUSIONS: The patient and her family are being followed further, but testing of her children for the presence of this mutation is currently being withheld. The difficulties in the management and treatment of patients with this clinically heterogenous disorder are discussed.

Adult↗
PubMed2002

Myelodysplastic syndrome in transformation to acute myeloid leukemia presenting with diabetes insipidus: due to pituitary infiltration association with abnormalities of chromosomes 3 and 7.

A 31-yr-old woman with myelodysplastic syndrome (MDS) in transformation to acute myeloid leukemia (AML) presented with initial symptoms of polyuria and polydipsia. Cytogenetics revealed monosomy 7 and translocation (3;3)(q21;q26). The initial symptoms, in conjunction with a low serum level of anti-diuretic hormone (ADH) and magnetic resonance imaging (MRI) findings demonstrating loss of the "bright spot" of the neurohypophysis, indicated diabetes insipidus (DI), e.g. caused by leukemic infiltration of the neurohypophysis. After induction chemotherapy the patient's bone marrow revealed blast persistence, and following a second course of chemotherapy and normalisation of MRI, an allogeneic peripheral blood stem cell transplantation (PBSCT) from the patient's HLA-identical brother was performed, resulting in ongoing complete remission. Recently, Lavabre-Bertrand et al. reported an association of AML with DI, elevated platelet counts, and monosomy 7 and chromosome 3 abnormalities in three patients (Eur. J. Haematol. 2001: 66: 66-69). Our report of an MDS with trilineage dysplasia and these karyotypic changes associated with DI indicates that this new entity may also include preleukemic cases.

Acute Disease↗
PubMed2002

DNA methylation and demethylating drugs in myelodysplastic syndromes and secondary leukemias.

BACKGROUND AND OBJECTIVES: Methylation of DNA is a common epigenetic modification that plays an important role in the control of gene expression in mammalian cells. This process involves CpG dinucleotide sequences and is catalyzed by DNA-methyltransferase enzymes. Under physiological conditions, methylated CpG sites are only present in DNA sequences typical of bulk chromatin, where the DNA is inaccessible to transcription factors. In contrast, CpG islands of promoter regions are usually unmethylated (with few exceptions such as the genes on the inactive X-chromosome). DNA methylation abnormalities have recently emerged as the most frequent molecular changes in hematopoietic neoplasms. INFORMATION SOURCES: The authors of the present review are currently working in the field of myelodysplastic syndromes and secondary leukemias and have contributed original papers to peer-reviewed journals. The material analyzed in the present review includes articles and reviews published in journals covered by the Science Citation Index, and abstracts presented at recent international oncology and hematology meetings. STATE OF THE ART: Methylation and transcriptional status are inversely correlated, the hypermethylation of genes involved in cell-cycle control and apoptosis could have a pathogenetic role in the development of cancer. In particular, high-risk myelodysplastic syndromes (MDS) and secondary leukemias (SL) show a high prevalence of tumor-suppressor gene hypermethylation. The use of irreversible DNA methyltransferase inhibitors, such as 5-azacytidine and decitabine, appears to be a promising therapeutic option for the treatment of MDS and SL. Large clinical trials are still ongoing, but preliminary data recently published indicate for the first time that the natural history of MDS may be changed by a non-intensive treatment. CONCLUSIONS AND PERSPECTIVES: Treatment with demethylating agents, 5-azacytidine and decitabine, at present results in significantly higher response rates, improved quality of life, reduced risk of leukemic transformation, and improved survival, when compared to supportive care. Azacytidine and decitabine provide a new treatment option, and should be the treatment choice for elderly patients with high risk MDS. It is whorty in fact that azacytidine and decitabine are especially active in patients with poor prognosis MDS. The combination with histone deacetylase inhibitors may increase the efficacy of hypomethylating agents in vivo.

Antimetabolites, Antineoplastic↗