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Biomedical subjects

L Ohler

Publications and source records attributed to L Ohler.

At least 19 recordsLinked to original sources
PubMed2004

Human leukaemic stem cells: a novel target of therapy.

Acute myeloid leukaemia (AML) is a life-threatening haematopoietic disease that is characterized by clonal growth and the accumulation of myelopoietic progenitor cells. Although AML cells only have a limited potential to undergo differentiation and maturation, each AML clone is organized in a hierarchical manner similar to normal haematopoiesis. Recent data have shown that each AML clone consists of leukaemic stem cells and their progeny, and that AML stem cells differ from more mature cells in several aspects, including survival and target antigen profiles. Most importantly, AML stem cells, but not their progeny, have the capacity to repopulate haematopoietic tissues with leukaemias in NOD/SCID mice. Furthermore, AML stem cells are thought to be responsible for the infinite growth of leukaemias in patients with AML. The phenotypic properties of AML stem cells have also been described. In most cases, these cells are detectable within the CD34+, CD38-, Lin-, CD123+ subpopulation of AML cells. Because of their AML-initiating and -renewing capacity and their unique phenotype, which includes several molecular targets of drug therapy, AML stem cells have recently been proposed as novel important target cell populations in the context of curative therapies. The present article gives an overview of our knowledge about AML stem cells, their phenotype, and their role as a 'therapy-target' in new concepts to treat and to cure patients with AML.

Forecasting↗
PubMed2003

High spontaneous colony growth in chronic myelomonocytic leukemia correlates with increased disease activity and is a novel prognostic factor for predicting short survival.

We have originally shown that spontaneous granulocyte/macrophage colony (CFU-GM) formation in semisolid medium is a characteristic in vitro feature of chronic myelomonocytic leukemia (CMML). However, the clinical significance of spontaneous CFU-GM growth in CMML is unknown so far. CFU-GM growth characteristics were studied in semisolid cultures in the absence of exogenous cytokines using peripheral blood mononuclear cells in 30 patients with CMML at first presentation. The median number of CFU-GM/10(5) MNC of all patients was 48.5 (range 0-622) with 18 patients having colony numbers below 100 (low CFU-GM growth) and 12 patients above 100 (high CFU-GM growth). Kaplan-Meier analysis revealed that patients with high CFU-GM growth had a significantly shorter survival than patients with low CFU-GM growth (median 6.5 vs. 44.5 months, p<0.00002). The probability of survival after 2 years was 60.5% for patients with low colony growth but 0% in those with high colony formation. Patients with CFU-GM >100 had a significantly higher WBC count, a higher LDH, and a higher number of blast cells in blood and bone marrow than patients with low colony growth. Moreover, patients with high colony growth had more often splenomegaly and lower platelet counts. In seven patients, in whom semisolid in vitro cultures were performed after transformation into RAEBT/AML, spontaneous colony growth was significantly increased as compared to CFU-GM growth in patients before transformation (median number/10(5) MNC 533, range 212-4553, p<0.005). This study demonstrates that high (>100) spontaneous CFU-GM formation in CMML at presentation correlates with increased disease activity and represents a novel and important prognostic factor predicting for short survival of CMML patients.

Aged↗
PubMed2003

Circulating myeloid colony-forming cells predict survival in myelodysplastic syndromes.

The growth characteristics and the prognostic value of cytokine-stimulated myeloid colony formation from peripheral blood mononuclear cells (PBMC) of patients with myelodysplastic syndromes (MDS) are largely unknown. In this study we have determined the number of myeloid colony-forming units (mCFUs) in semisolid medium from 112 MDS patients and correlated them with French-American-British (FAB) type, the international prognostic scoring system (IPSS), karyotype, peripheral blood (PB) and bone marrow (BM) blast cells, cytopenias, lactate dehydrogenase (LDH), and survival data. Concerning the FAB classification, lower median mCFUs were found in patients with refractory anemia (RA) and refractory anemia with ringed sideroblasts (RARS) compared to refractory anemia with excess of blast cells (RAEB) and refractory anemia with excess of blasts cells in transformation (RAEB-T). In vitro growth in MDS clearly correlated with the cytogenetic risk groups defined by the IPSS (30.5/10(5) PBMCs with favorable karyotypes, 191 in the intermediate prognostic group, 677 with unfavorable cytogenetics, p=0.015 favorable vs unfavorable). BM blast cells >5% (60.5 vs 255 colonies, p=0.032) as well as LDH levels above the normal limit (64.5 vs 425 colonies, p=0.045) were also associated with higher colony formation. Patients were stratified according to the number of circulating mCFUs into a low growth, intermediate growth and high growth group. Median survival was 343 days in the high growth, 1119 days in the low growth, and 2341 days in the intermediate growth group ( p=0.0002). Multivariate analyses revealed colony growth ( p=0.0056), PB blast cells ( p=0.0069), cytogenetic risk group ( p=0.024), and platelet count ( p=0.018) to predict survival in our patients. After inclusion of the IPSS risk categories, mCFU levels remained a highly predictive parameter for survival ( p=0.0056) and acute myeloblastic leukemia (AML) transformation ( p=0.0003).

Blood Cells↗
PubMed2003

Numbers of colony-forming progenitors in patients with systemic mastocytosis: potential diagnostic implications and comparison with myeloproliferative disorders.

BACKGROUND: An increase in colony-forming progenitor cells (CFU) is typically seen in myeloproliferative disorders (MPD). Systemic mastocytosis (SM) is a haemopoietic neoplasm involving myeloid progenitors similar to MPD. In the present study, we measured the levels of peripheral blood (pb) and bone marrow (bm) CFU in patients with different categories of SM, and compared them with those obtained in MPD patients and healthy controls. MATERIALS AND METHODS: Numbers of CFU (CFU-GM, BFU-E, CFU-GEMM) were measured in a colony assay in 25 patients with SM [indolent SM (ISM), n = 15; smouldering SM (SSM), n = 3; SM with an associated haematologic clonal non-mast cell lineage disease (SM-AHNMD), n = 5; aggressive SM (ASM), n = 1; mast cell leukaemia (MCL), n = 1] and 37 with MPD [chronic myeloid leukaemia (CML), n = 10; polycythemia vera (PV), n = 8; essential thrombocytosis (ET), n = 9; idiopathic myelofibrosis (IMF), n = 10]. RESULTS: In the patients with MPD, elevated numbers of pb CFU were detected in all groups when compared with healthy controls (P < 0.05). In most of the patients with ISM, circulating CFU levels (CFU-GM, BFU-E, and CFU-GEMM) were within the normal range. In SSM, pb CFU-GM levels were normal in two patients, and elevated in a third patient. In the "SM-AHNMD-group", CFU levels were found to reflect the nature of the AHNMD: in SM with concomitant acute myeloid leukaemia (SM-AML, n = 2), the levels of CFU were low or undetectable, whereas in SM with chronic myelomonocytic leukaemia (SM-CMML, n = 2), elevated numbers of pb CFU-GM were found. CONCLUSION: The numbers of CFU are normal in patients with ISM, but elevated in some patients with SSM and SM-CMML. An elevated CFU level in SM should raise the suspicion of an associated MPD (CMML) or smouldering SM, a novel SM-subtype that shares several features with MPD and sometimes progresses to an overt SM-MPD.

Adult↗
PubMed2001

Cytogenetic risk groups in acute myeloblastic leukaemia differ greatly in their semi-solid colony growth.

We have analysed the results of semi-solid bone marrow cultures in 296 patients with de novo acute myeloblastic leukaemia (AML) and correlated them with the leukaemic karyotype. A favourable prognostic karyotype was found in 52 patients (group A, 18.3%), an intermediate karyotype in 163 patients (group B, 57.4%), and unfavourable cytogenetics were observed in 69 patients (group C, 24.3%). Median colony growth according to the three risk groups was 2 (range 0--344) in group A, 14.5 (range 0--5000) in group B and 50.0 (0--3000) in group C (A vs. B, P < 0.001; A vs. C, P < 0.001; B vs. C, P < 0.01). Among the patients treated with chemotherapy (n = 257), median colony growth was 10 (range 0-5000) in those who achieved complete remission (CR) compared with 56.5 (range 0-1000) in patients without remission (NR) (P = 0.002). The median colony growth of all patients [13/10(5) bone marrow mononuclear cells (BMMCs); range 0--5000] significantly discriminated between patients regarding survival (OS 11 vs. 7 months, P = 0.044). However, multiple Cox regression analysis revealed cytogenetic risk groups as the most important predictor for achieving CR, disease-free and overall survival, with colony growth adding no additional prognostic information. In 64 patients, colony growth was also investigated without the addition of exogenous cytokines. Interestingly, none of the patients with a favourable karyotype exhibited autonomous growth, whereas 50% with an intermediate and 73% of patients with an unfavourable karyotype displayed either partial or full autonomous growth in vitro (P = 0.0004). Our data suggest that the growth potential of the leukaemic clone seems to be critically influenced by the molecular changes emerging from chromosomal abnormalities.

Adolescent↗
PubMed2000

Decrease of circulating hematopoietic progenitor cells During interleukin-2 treatment is associated with an increase of vascular cell adhesion molecule-1, a critical molecule for progenitor cell adhesion.

Administration of interleukin-2 (IL-2) to cancer patients has been shown to transiently decrease the number of circulating hematopoietic progenitor cells, but the mechanism of this phenomenon is unknown. Recently, the interaction of vascular adhesion molecule-1 (VCAM-1) with leukocyte very late antigen-4 (VLA-4) has been demonstrated to play a crucial role in the adhesion of progenitor cells to bone marrow stromal elements. Cytokine induced upregulation of VCAM-1 leads to increased binding of progenitor cells to stromal cells in vitro, and inhibition of this interaction by monoclonal antibodies is associated with marked progenitor cell mobilisation in vivo. In the present study we serially determined peripheral blood progenitor cell numbers during IL-2 treatment (10 courses) in 6 cancer patients and determined in parallel levels of soluble VCAM-1 as a surrogate marker for the in vivo activation of this molecule. Our data indicate that continuous intravenous administration of IL-2 for 5 days leads to a marked decrease of circulating progenitor cells associated with a substantial increase of circulating VCAM-1. Circulating myeloid progenitor cells (CFU-GM) dropped from a mean value of 167 +/- 187 / ml pre IL-2 to 16 +/- 15 / ml on day 3 (p < 0.01). Similarily, mean erythroid progenitors (BFU-E) decreased from 282 +/- 204 / ml before IL-2 administration to 86 +/- 61 / ml on day 3 (p < 0.005). In contrast, soluble VCAM-1 rose from a mean value of 1814 +/- 451 ng/ml before to 4607 +/- 736 ng/ml at the end of IL-2 therapy (p < 0.0001). Sera from IL-2 treated patients did not inhibit hematopoietic colony formation from normal bone marrow. These results suggest redistribution and increased adhesion of progenitor cells to stromal and/or endothelial elements during IL-2 via the VCAM-1/VLA-4 interaction as a possible mechanism for the decrease of circulating progenitor cells during IL-2 therapy.

Adult↗
PubMed1999

Long-term improvement of hematopoiesis following cyclosporine treatment in a patient with myelodysplastic syndrome.

Current treatment of patients with myelodysplastic syndrome (MDS) is unsatisfactory. Very recently, immunosuppressive treatment strategies have been gaining interest. We report a patient with transfusion-dependent MDS who achieved significant hematopoietic improvement following cyclosporine (CsA) therapy and who is now transfusion independent for more than 5 years. This single observation supports the view that CsA, among other immunosuppressive agents, could play an important role in future treatment concepts in MDS and may lead to clinically relevant and sustained improvement of hematopoiesis in a subset of patients.

Adult↗
PubMed1999

Single nucleotide polymorphism determination using primer extension and time-of-flight mass spectrometry.

The high frequency of single nucleotide polymorphisms (SNPs) in the human genome makes them a valuable source of genetic markers for identity testing, genome mapping, and medical diagnostics. Conventional technologies for detecting SNPs are laborious and time-consuming, often prohibiting large-scale analysis. A rapid, accurate, and cost-effective method is needed to meet the demands of a high-throughput DNA assay. We demonstrate here that analysis of these genetic markers can now be performed routinely in a rapid, automated, and high-throughput fashion using time-of-flight mass spectrometry and a primer extension assay with a novel cleavable primer. SNP genotyping by mass spectrometry involves detection of single-base extension products of a primer immediately adjacent to the SNP site. Measurement of the mass difference between the SNP primer and the extension peak reveals which nucleotide is present at the polymorphic site. The primer is designed such that its extension products can be purified and chemically released from the primer in an automated format. The reduction in size of the products as a result of this chemical cleavage allows more accurate identification of the polymorphic base, especially in samples from a heterozygotic population. All six possible heterozygotes are resolved unambiguously, including an A/T heterozygote with extension products differing by only 9 Da. Multiplex SNP determination is demonstrated by simultaneously probing multiple SNP sites from a single polymerase chain reaction (PCR) product as well as from multiplexed PCR amplicons. Samples are processed in parallel on a robotic workstation, and analyzed serially in an automated mass spectrometer with analysis times of only a few seconds per sample, making it possible to process thousands of samples per day.

DNA Primers↗