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J Vormoor

Publications and source records attributed to J Vormoor.

At least 37 records · Page 2Linked to original sources
PubMed1999

Expression of AC133 and CD117 on candidate normal stem cell populations in childhood B-cell precursor acute lymphoblastic leukaemia.

To identify residual candidate normal progenitor/stem cell populations in childhood B-cell precursor acute lymphoblastic leukaemia (ALL), expression of AC133 and CD117 was analysed on the leukaemic cell clone and on immature B-lineage-negative CD34+CD19- bone marrow cells. 10/25 patients (40%) had no detectable expression of AC133 within the leukaemic cell clone. 24/26 patients (92%) lacked expression of CD117 on the leukaemic blast cell population. In contrast, a distinct AC133-positive cell population was found in 8/8 children with AC133-negative ALL and a CD117-positive cell population could be identified in 12/12 children with CD117-negative ALL, within the CD34+CD19- progenitor/stem cell compartment. These observations provide further evidence that in B-cell precursor ALL, unlike in acute myelogenous leukaemia, it may be possible to distinguish residual normal progenitor/stem cells from the leukaemic cell clone.

AC133 Antigen↗
PubMed1998

Flow cytometric identification of candidate normal stem cell populations in CD45-negative B-cell precursor acute lymphoblastic leukaemia.

CD45-negative B-cell precursor acute lymphoblastic leukaemia (ALL) provides a unique model to study the stem cell compartment in ALL as leukaemic CD34-positive cells, unlike their normal counterparts, do not express CD45. By increasing the number of events analysed to 10(6), storing only the events in the region of interest (storage gate), using appropriate isotype controls and stringent washing procedures, a flow cytometric protocol was established to characterize rare CD34+ CD19- events. In eight of 12 patients (67%) with CD45-negative B-cell precursor ALL, a distinct CD34+ CD19- CD45+ candidate normal stem cell population could be detected. In one patient analysed by four-colour staining, the CD34+ CD19- CD45+ cells, unlike the CD45-negative leukaemic cells, expressed CD117 (c-kit), providing further evidence that these cells represent residual nonleukaemic normal cells. By multiparameter analysis, this population of candidate normal stem cells could be separated from contaminating leukaemic CD34+ CD19- CD45- cells, which were detected in 11 of the 12 patients within the CD34+ CD19- compartment.

Acute Disease↗
PubMed1996

Identification of human juvenile chronic myelogenous leukemia stem cells capable of initiating the disease in primary and secondary SCID mice.

Most juvenile chronic myelogenous leukemia (JCML) cells have limited long-term proliferative capacity, and only a minority of immature cells give rise to colonies in semisolid cultures. Clonogenic JCML progenitors cannot be maintained in culture because they differentiate, and within a few weeks the leukemic clone is lost. This makes it difficult to identify the cell that initiates and maintains the disease in patients. To determine the proliferative capacity of JCML cells in vivo, bone marrow (BM), peripheral blood, or spleen cells from eight patients with JCML either at diagnosis or during treatment were transplanted into sublethally irradiated severe combined immune deficient (SCID) mice. JCML cells from all patients homed to the murine BM and proliferated extensively in response to exogenous stimulation with granulocyte-macrophage colony-stimulating factor. Within a few weeks, highly engrafted mice became ill and cachectic due to infiltration of leukemic cells and secretion of tumor necrosis factor-alpha. Murine BM, spleen, and liver were infiltrated with leukemic blasts, and typical JCML colony-forming progenitors could be recovered. Kinetic experiments demonstrated that only a small minority of transplanted cells homed to the murine BM, and that these cells initiated and maintained the disease in vivo by extensive proliferation and differentiation. To characterize the cell-surface phenotype of the JCML initiating cell (JCML-IC), JCML blood or spleen cells were fractionated on the basis of CD34/CD38 marker expression and transplanted into SCID mice. Only immature CD34+ cells could initiate the disease, while mature CD34- cells did not engraft. Within the CD34+ compartment, there was enrichment for JCML-ICs by immature cells with a CD34+/CD38- stem-cell-like phenotype. Mice transplanted with more mature CD34+/CD38+ populations that also contained clonogenic JCML progenitors were poorly engrafted. These results indicate that the JCML-IC is an earlier stage of development than clonogenic JCML progenitors. Additional evidence that the JCML-IC has stem-cell properties comes from secondary transplant experiments that test the self-renewal capacity. The JCML-IC from all three patients tested could successfully reinitiate the disease in secondary murine recipients. Thus, we have developed a functional in vivo model that replicates many aspects of human JCML, and have used this model to identify and characterize JCML-ICs and their stem-cell properties.

Animals↗
PubMed1996

Normal and leukemic SCID-repopulating cells (SRC) coexist in the bone marrow and peripheral blood from CML patients in chronic phase, whereas leukemic SRC are detected in blast crisis.

Progress in understanding the abnormal regulation of hematopoiesis in chronic myelogenous leukemia (CML) would be facilitated if neoplastic cells, at all stages of the disease, could be studied in an animal model. In this report, we show that irradiated severe combined immunodeficient (SCID) mice can be transplanted with both normal (Philadelphia chromosome [Ph]-negative) and neoplastic (Ph+) cells from CML patients with either chronic or blast phase disease. Mice transplanted with peripheral blood (PB) or bone marrow (BM) cells from 9 of 12 chronic phase CML patients were well engrafted with human cells including multilineage colony-forming progenitors and CD34+ cells for at least 90 days posttransplantation. Repeated posttransplant injections of cytokines did not enhance the number of engrafted human cells. Interestingly, approximately 70% of the human progenitors found in the engrafted SCID BM were Ph-, suggesting that the growth of primitive normal cells is favored in this in vivo transplant model. A similar number of normal cells were found in mice transplanted with either PB or BM cells, suggesting that elevated numbers of primitive normal cells are present in CML PB. When cells from patients with CML in either myeloid or lymphoid blast crisis were transplanted into SCID mice, the BM of these mice was more rapidly repopulated and to a higher level than that observed with transplants of chronic phase cells. Moreover, all human colony-forming progenitors present in the BM of mice transplanted with blast crisis cells were Ph+, and the majority of cells showed the same morphological features of the blast crisis cells originally transplanted. These experiments provide a starting point for the creation of an animal model of CML and establish the feasibility of using this model for the future characterization of transplantable CML stem cells during disease progression.

Animals↗
PubMed1996

Therapy of childhood acute myelogenous leukemias.

Acute myelogenous leukemia (AML) accounts for approximately 20% of acute leukemias in children. Although AML is more resistant to chemotherapy than acute lymphoblastic leukemia (ALL), significant progress in improving outcome for AML patients has been achieved over the past 15 years. This can be attributed to intensification of chemotherapy, increased use of bone marrow transplantation, and improved supportive care. Thus 30-50% of children with AML achieve long-term event-free survival with current treatment strategies [61, 66, 85, 96]. This review gives an overview about the evolution of and rationale for current pediatric treatment protocols, with special emphasis on the German Berlin-Frankfurt-Münster (BFM) studies, and discusses new directions for the future.

Antineoplastic Agents↗
PubMed1996

Identification of primitive human hematopoietic cells capable of repopulating NOD/SCID mouse bone marrow: implications for gene therapy.

The development of stem-cell gene therapy is hindered by the absence of repopulation assays for primitive human hematopoietic cells. Current methods of gene transfer rely on in vitro colony-forming cell (CFC) and long-term culture-initiating cell (LTC-IC) assays, as well as inference from other mammalian species. We have identified a novel human hematopoietic cell, the SCID-repopulating cell (SRC), a cell more primitive than most LTC-ICs and CFCs. The SRC, exclusively present in the CD4+CD8- fraction, is capable of multilineage repopulation of the bone marrow of nonobese diabetic mice with severe combined immunodeficiency disease (NOD/SCID mice). SRCs were rarely transduced with retroviruses, distinguishing them from most CFCs and LTC-ICs. This observation is consistent with the low level of gene marking seen in human gene therapy trials. An SRC assay may aid in the characterization of hematopoiesis, as well as the improvement of transduction methods.

ADP-ribosyl Cyclase↗
PubMed1996

Myelodysplasia and acute myelogenous leukemia in Down's syndrome. A report of 40 children of the AML-BFM Study Group.

Forty children with Down's syndrome have been identified among 633 patients in the cooperative pediatric BFM studies for acute myelogenous leukemia (AML) since 1987. The following features were characteristic for these patients: (1) a 500-fold higher than expected incidence of megakaryoblastic leukemia (M7) with a peak incidence under 4 years of age; (2) a myelodysplastic prephase with thrombocytopenia lasting for several months up to a few years; (3) frequent involvement of the red cell lineage as suggested by dyserythropoiesis in the bone marrow; (4) coexpression of the lymphoid cell surface antigen CD7 on the leukemic blasts; (5) absence of the translocation t(1;22), instead presence of complete or partial trisomies involving chromosomes 8 and 1; and (6) a good response to chemotherapy. Nearly half of the patients did not receive any or only palliative chemotherapy and subsequently died. In 21 patients treatment according to the AML-BFM protocols was intended, however, with major dose or protocol reductions in six patients. Four died early, 15 (71%) achieved remission. Nine of 11 patients remaining alive for 0.6-6.5 years had received intensive treatment including high-dose cytosine arabinoside (HD-Ara-C). The 5-year survival estimate of 48% +/- 12% was similar to patients without Down's syndrome. In conclusion, these clinical and biological features suggest that M7 leukemia in children with Down's syndrome (M7-Down) is distinct from megakaryoblastic leukemia in other children. Children with Down's syndrome show a favorable outcome if treated adequately. However, overtreatment should be avoided and life-threatening infections pose a particular problem. Therefore, standard-risk AML therapy (including HD-Ara-C) should be considered in children with Down's syndrome and AML.

Adolescent↗
PubMed1995

Engraftment of immune-deficient mice with primitive hematopoietic cells from beta-thalassemia and sickle cell anemia patients: implications for evaluating human gene therapy protocols.

Permanent correction of genetic deficiencies of the hematopoietic system requires gene transfer into stem cells and long-term lineage specific expression after autologous transplantation. However, progress to develop gene therapy protocols has been hampered by the absence of in vivo assays that detect genetically deficient human hematopoietic stem cells and their diseased differentiated progeny. The establishment of systems to transplant human cells into immune-deficient SCID mice provides such an assay. We report that primitive bone marrow cells from beta-thalassemia major and sickle cell anemia patients engraft immune-deficient mice, giving rise to high levels of human erythroid and myeloid cells in response to treatment with human cytokines. The bone marrow of transplanted mice contained the entire erythroid lineage from BFU-E to mature erythrocytes expressing human gamma, beta or beta s-globin. Moreover, human erythroid cells from mice transplanted with sickle cell anemia bone marrow showed characteristic sickling under reducing conditions in an in vitro assay. This model provides a powerful in vivo system that can be used to evaluate the efficiency of globin gene transfer into primitive human hematopoietic cells, lineage-specific expression in mature erythrocytes, and ultimately correction of the cellular defect found in the erythroid lineage.

Anemia, Sickle Cell↗
PubMed1994

Immature human cord blood progenitors engraft and proliferate to high levels in severe combined immunodeficient mice.

Unseparated or Ficoll-Hypaque (Pharmacia, Piscataway, NJ)--fractionated human cord blood cells were transplanted into sublethally irradiated severe combined immunodeficient (SCID) mice. High levels of multilineage engraftment, including myeloid and lymphoid lineages, were obtained with 80% of the donor samples as assessed by DNA analysis, fluorescence-activated cell sorting (FACS), and morphology. In contrast to previous and concurrent studies with adult human bone marrow (BM), treatment with human cytokines was not required to establish high-level human cell engraftment, suggesting that neonatal cells either respond differently to the murine microenvironment or they provide their own cytokines in a paracrine fashion. Committed and multipotential myelo-erythroid progenitors were detected using in vitro colony assays and FACS analysis of the murine BM showed the presence of immature CD34+ cells. In addition, human hematopoiesis was maintained for at least 14 weeks providing further evidence that immature hematopoietic precursors had engrafted the murine BM. This in vivo model for human cord blood-derived hematopoiesis will be useful to gain new insights into the biology of neonatal hematopoietic cells and to evaluate their role in gene therapy. There is growing evidence that there are ontogeny-related changes in immature human hematopoietic cells, and therefore, the animal models we have developed for adult and neonatal human hematopoiesis provide useful tools to evaluate these changes in vivo.

Animals↗
PubMed1994

A cell initiating human acute myeloid leukaemia after transplantation into SCID mice.

Most human acute myeloid leukaemia (AML) cells have limited proliferative capacity, suggesting that the leukaemic clone may be maintained by a rare population of stem cells. This putative leukaemic stem cell has not been characterized because the available in vitro assays can only detect progenitors with limited proliferative and replating potential. We have now identified an AML-initiating cell by transplantation into severe combined immune-deficient (SCID) mice. These cells homed to the bone marrow and proliferated extensively in response to in vivo cytokine treatment, resulting in a pattern of dissemination and leukaemic cell morphology similar to that seen in the original patients. Limiting dilution analysis showed that the frequency of these leukaemia-initiating cells in the peripheral blood of AML patients was one engraftment unit in 250,000 cells. We fractionated AML cells on the basis of cell-surface-marker expression and found that the leukaemia-initiating cells that could engraft SCID mice to produce large numbers of colony-forming progenitors were CD34+ CD38-; however, the CD34+ CD38+ and CD34- fractions contained no cells with these properties. This in vivo model replicates many aspects of human AML and defines a new leukaemia-initiating cell which is less mature than colony-forming cells.

ADP-ribosyl Cyclase↗
PubMed1994

Increased DNA-repair capacity and the modulation of 2 proteins in and metallothionein overexpressing Chinese hamster cell line.

Elevated intracellular levels of metallothionein have been associated with resistance to the cytotoxic effects of some alkylating agents. In order to study the mechanisms responsible for this resistance, we used a pair of CHO cell lines consisting of normal K1-2 cells and their derivative K1-2MT, which overexpresses the human metallothionein II-A gene (Lohrer et al., 1989). K1-2MT cells were found to be resistant to cadmium chloride and the alkylating agents N-methyl-N'-nitro-N- nitrosoguanidine (MNNG), but resistance did not extend to the alkylating agent, 1,3-bis(2-chloroethyl)- 1-nitrosourea, nor to adriamycin, an inhibitor of DNA synthesis. The DNA damage caused by MNNG, was only marginally less in resistant cells compared with the parental cell line, thus excluding drug scavenging as a possible mechanism for resistance. Also, glutathione S-transferases (GSTs) were present at equal levels in both cell lines (acidic and basic type GST) or slightly reduced in drug resistant K1-2MT cells (neutral type GST), thereby ruling out metabolic inactivation of the alkylating agents. However, the drug resistant phenotype was accompanied by a more efficient block of DNA synthesis after MNNG treatment and by a 3-h delay in the G2 phase of the cell cycle. Using two-dimensional gel electrophoresis of total protein extracts, we identified a 24-kDa protein (MIP1), which is only present in the resistant K1-2MT cells, and a 23.5-kDa protein (MIP2) which is 2-3 times over-synthesized in K1-2MT cells. MNNG treatment reduced the level of both proteins MIP1 and MIP2. These results suggest that the proteins MIP1 and possibly MIP2 may be responsible for the alkylating agent resistant phenotype and are probably modulated by the human metallothionein II-A protein.

Alkylating Agents↗
PubMed1994

SCID mice as an in vivo model of human cord blood hematopoiesis.

Cord blood is increasingly used as an alternative stem cell source for autologous and allogeneic transplantation, particularly in pediatric patients. We therefore adopted our protocol for transplanting human adult bone marrow cells into severe combined immunodeficient (SCID) mice [1] to develop an in vivo model for cord blood hematopoiesis. Intravenous injection of unfractionated or Ficoll-separated cord blood cells into sublethally irradiated SCID mice led to high levels of human hematopoiesis in the majority of the recipients [2]. Multilineage human hematopoiesis including committed and multipotential myeloerythroid progenitors as well as CD19+ B-lymphoid cells were observed in the murine bone marrow for at least 18 weeks. Together, these data indicate that the SCID mice were engrafted with an immature cell that was able to maintain multiple progenitor lineages in vivo. In contrast to our experiences with adult bone marrow, high levels of human cell engraftment in the mouse could be achieved without exogenous cytokine treatment, suggesting that the cord blood cells respond differently to the murine microenvironment. Alternatively, the cord blood cells might have been able to provide themselves with the necessary growth factors in a paracrine fashion. This model will be useful in gaining new insights into the biology of immature human cord blood progenitors and cord blood transplantation.

Animals↗
PubMed1992

Acute myelogenous leukaemia in children under 2 years--experiences of the West German AML studies BFM-78, -83 and -87. AML-BFM Study Group.

Clinical, morphological, immunological, cytogenetical and prognostic features of 84 children under 2 years of age with AML in studies AML-BFM-78, -83 and -87 were retrospectively analysed. There was a high incidence of acute monoblastic leukaemia (FAB M5) (41 patients--49%) and acute megakaryoblastic leukaemia (FAB M7) (study AML-BFM-87: five patients--13%) in this age group. Acute monoblastic leukaemia was associated with hepatosplenomegaly, extramedullary organ manifestations and chromosomal abnormalities involving 11q23. The probability of an 11-year event-free survival of all patients under 2 years of the three studies combined was 39% (SD 6%). While the event-free survival rates of patients aged 2 years and older could be improved in studies AML-BFM-83 and -87 compared with study AML-BFM-78, overall prognosis in children under 2 years in the three consecutive studies remained unchanged. The event-free survival rate of children with acute monoblastic leukaemia in both age groups was comparable (7 yr-EFS (AML-BFM-83 and -87): much less than 2 years--43% (SD 9%), =/much greater than 2 years--33% (SD 9%); P much greater than 0.5). This also applied to other risk groups. In conclusion, taking the high incidence of acute monoblastic and megakaryoblastic leukaemia in children under 2 years into account, no significant differences between children under 2 years or older children concerning response to therapy and overall prognosis could be evaluated.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1989

Prognostic significance of Auer rods in childhood acute myelogenous leukemia: results of the studies AML-BFM-78 and -83.

The prognostic significance of Auer rods in predicting response rate and remission duration was investigated in 257 patients of the two West German acute myelogenous leukemia (AML) studies BFM-78 and -83. Auer rods were found in 129 children (50%) in the initial bone marrow smear. The incidence was higher in myeloid subtypes M1 (63%) and M2 (78%) compared with subtypes M4 (47%) and M5 (5%) with monocytic differentiation. In both studies, the remission rate was significantly higher in patients with Auer rods (P = 0.01), and in the study AML-BFM-83 a significantly longer remission duration was evaluated for Auer rod-positive patients (P = 0.007). In the M1 type, Auer rods were of high prognostic significance regarding both the induction success (P = 0.003) and the remission duration (P = 0.004), whereas no significant differences between Auer rod-positive and -negative patients in other subtypes were found. Occurrence of Auer rods was independent of hyperleukocytosis, the most powerful prognostic parameter in the studies AML-BFM-78 and -83, whereas absence of Auer rods was associated with the AML risk group M5. In the M1 type, Auer rod-negative leukemias appears to represent cases of poorly differentiated AML. Auer rods were therefore useful in differentiating between patients with a poor and a more favorable prognosis, particularly in the M1 type.

Adolescent↗
PubMedDate not supplied

[Current state of cord blood transplantation in childhood].

In 1989 E. Gluckman reported the successful cord blood transplantation in a boy with Fanconi anemia. Since then more than 1500 allogeneic cord blood transplantations have been performed worldwide. This has been possible because non-profit cord blood banks have been established that provide cryopreserved cord blood products from unrelated donors. However, cord blood transplantation is associated with specific risks that have sofar limited its more widespread use. Its main problem is the limited stem cell dose that is associated with a long aplasia and a high rate of engraftment failure. Therefore, cord blood is used as the stem cell source in only about 1 - 2 % of stem cell transplantations in childhood. The main advantage of cord blood transplantation lies in its low risk for graft-versus-host-disease (GvHD), one of the major causes for posttransplant morbidity and mortality particularly with unrelated stem cell donors. The low risk for GvHD is attributed to the low number of transplanted T cells and their functional immaturity. Another advantage of cord blood transplantation lies in the immediate availability of the cord blood units. Based on the experiences with allogeneic cord blood transplantation the indications for cord blood donation will be discussed.

Blood Donors↗
PubMedDate not supplied

[Minimal residual disease in acute myeloid leukemia in children--standardization and evaluation of immunophenotyping in the AML-BFM-98 study].

BACKGROUND: Minimal residual disease is a prognostic factor in AML. However, the impact on treatment stratification is not established. The AML-BFM 98 MRD study started in 1/2000 in order to evaluate, standardize and establish immunophenotyping in AML in children. METHODS: In a first phase the participating laboratories in Muenster, Goettingen, Vienna and Prague agreed on identical antibody-panels and standardized procedures of sample processing, analysis and data management. The consensus panel was evaluated and adapted to 3- and 4-color flowcytometry. The complete panel was applied to each follow-up sample in orderto minimize the risk offalse negative results due to the loss or shift of antigens during treatment, a known phenomenon in myeloid blasts. Between 1/2000 and 9/2001 165 of 198 protocol patients were analysed at diagnosis, in 149 children at least two follow-up samples were available. RESULTS: Three kinds of immunophenotypes could be defined. Asynchronous expression of stem cell and myeloid antigens i. e. CD34/CD117 combined with CD13/CD15 had a low specificity because precursors in regenerating or normal bone marrow expressed this pattern in 0.47 % (0.1 to 1.5 %). The aberrant co-expression of stem cell antigens and lymphatic antigens such as CD7 or CD2 showed a median level of specificity (0.07 % (0.04 to 0.19 %). Aberrant expression ofstem cell antigens combined with B-lymphatic (CD19, CD10) or NK-cell antigen (CD56) showed the best specificity. The maximal level in normal bone marrow was 0.05 %. Sensitivity of different immunophenotypes was evaluated by diluting known leukemic blasts in regenerating bone marrow. Minimal level of sensitivity was found to be at 10 (-3) to 5 x 10 (-4). According to these data highiy specific immunophenotypes could be detected in 33 %, median specificity was seen in 71 % and low specificity was seen in 88 % of the protocol patients. Two laboratories analyzed simultaneously 17 samples of children with AML from diagnosis and during therapy. A high correlation of blast quantification could be demonstrated (correlation r (2) = 0.98; blasts < 5 % r (2) = 0.91). In addition, two independent explorers quantified the raw data of 16 samples. All results correlated well (r (2) = 0.97; blasts < 5 % r (2) = 90.94). CONCLUSION: The prospective study phase, started 1/2002, aims to test the impact of MRD diagnostics as an independent prognostic factor in AML in children. This might facilitate future treatment stratification and consequently optimize outcome.

Adolescent↗
PubMedDate not supplied

Adoptive cellular immunotherapy with CD19-specific T cells.

BACKGROUND: No effective therapeutic modalities exist for the treatment of relapsed high risk acute lymphoblastic leukemia (ALL). Adoptive cellular immunotherapy by transfusion of polyclonal donor lymphocytes is not always effective and is limited by cellular cross-reactivity with normal tissues, leading to development of clinical graft-versus-host disease (GVHD). METHOD: To develop an immunotherapeutic strategy for targeted elimination of residual leukemic blasts, human T cells were gene-modified to express CD19-specific chimeric receptors. RESULTS: Gene-modified T cells specifically lyse CD19-expressing lymphatic blast cells, however, they show a limited proliferative response to stimulation with CD19. Integration of the signal transduction domain of the costimulatory molecule CD28 enhances the proliferative properties of the gene-modified T cells. CONCLUSIONS: Adoptive transfer of gene-modified virus-specific T cells may provide a useful strategy for prevention and early treatment of ALL relapses following allogeneic stem cell transplantation.

Antigens, CD19↗