A primitive hematopoietic cell is the target for the leukemic transformation in human philadelphia-positive acute lymphoblastic leukemia.
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BCR-ABL is a chimeric oncogene generated by translocation of sequences from the chromosomal counterpart (c-ABL gene) on chromosome 9 into the BCR gene on chromosome 22. Alternative chimeric proteins, BCR-ABL(p190) and BCR-ABL(p210), are produced that are characteristic of chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph(1)-ALL). In CML, the transformation occurs at the level of pluripotent stem cells. However, Ph(1)-ALL is thought to affect progenitor cells with lymphoid differentiation. Here we demonstrate that the cell capable of initiating human Ph(1)-ALL in non-obese diabetic mice with severe combined immunodeficiency disease (NOD/SCID), termed SCID leukemia-initiating cell (SL-IC), possesses the differentiative and proliferative capacities and the potential for self-renewal expected of a leukemic stem cell. The SL-ICs from all Ph(1)-ALL analyzed, regardless of the heterogeneity in maturation characteristics of the leukemic blasts, were exclusively CD34(+ )CD38(-), which is similar to the cell-surface phenotype of normal SCID-repopulating cells. This indicates that normal primitive cells, rather than committed progenitor cells, are the target for leukemic transformation in Ph(1)-ALL. (+info)
Prognostic implications of differences in telomere length between normal and malignant cells from patients with chronic myeloid leukemia measured by flow cytometry.
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Chronic myeloid leukemia (CML) is a clonal, multilineage myeloproliferative disorder characterized by the Philadelphia chromosome (Ph) and a marked expansion of myeloid cells. Previous studies have indicated that the telomere length in blood cells may indicate their replicative history. However, the large variation in telomere length between individuals complicates the use of this parameter in CML and other hematologic disorders. To circumvent this problem, we compared the telomere length in peripheral blood or bone marrow cells with purified normal (Ph(-)) T lymphocytes from the same CML patient using fluorescence in situ hybridization and flow cytometry. Overall telomere fluorescence was significantly reduced in Ph(+) cells from patients with CML compared to blood leukocytes from normal individuals (P < 0.001) or normal (Ph(-)) T lymphocytes from the same individuals (n = 51, P < 0.001). Cells from patients in accelerated phase or blast phase (AP/BP) showed significantly shorter average telomere length than cells from patients in chronic phase (CP, P = 0.02) or cytogenetic remission (CR, P = 0.03). Patients in CP who subsequently developed BP within 2 years had significantly shorter telomeres than those who did not develop BP for at least 2 years (P < 0.05). Accelerated replication-dependent telomere shortening in Ph(+ )versus Ph(-) leukocytes supports previous evidence that Ph(+) stem cells cycle more actively than their counterparts in normal individuals. Our data further suggest that telomere shortening may serve as a surrogate marker of disease progression in patients with CP CML, supporting a mechanistic link between CML stem cell turnover, genetic instability, and malignant evolution in this disease. (Blood. 2000;95:1883-1890) (Blood. 2000;95:1883-1890) (+info)
BCR-ABL tyrosine kinase activity regulates the expression of multiple genes implicated in the pathogenesis of chronic myeloid leukemia.
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The BCR-ABL chimeric protein is thought to play a central role in the pathogenesis of Philadelphia (Ph) chromosome-positive leukemias, notably chronic myeloid leukemia (CML). There is compelling evidence that malignant transformation by BCR-ABL is critically dependent on its protein tyrosine kinase (PTK) activity. As a result, multiple signaling pathways are activated in a kinase-dependent manner, and thus the activation of such pathways may affect the expression of genes that confer the malignant phenotype. In this study, we used differential display to investigate the alterations of gene expression in BV173, a CML cell line derived from lymphoid blast crisis, after exposure to ST1571, which selectively inhibits ABL PTK activity. We show that the expression of a set of 12 genes is correlated with the kinase activity and that the profile of these genes reflects mechanisms implicated in the pathogenesis of CML. Several of the genes show a consistent pattern of altered regulation in all Ph-positive lymphoid cell lines, whereas others appear to be unique to BV173 cells. We conclude that BCR-ABL PTK activity drives the expression of specific target genes that contribute to the malignant transformation of Ph-positive cells. The identification of downstream molecules with a consistent regulation pattern may provide suitable targets for therapeutic intervention in the future. (+info)
Early detection of relapse by hypermetaphase fluorescence in situ hybridization after allogeneic bone marrow transplantation for chronic myeloid leukemia.
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PURPOSE: Standard G-band cytogenetic analysis (CG) provides information on approximately 25 metaphases for monitoring the presence of Philadelphia chromosome positive (Ph+) cells in chronic myelogenous leukemia (CML) patients, making the detection of a low frequency of Ph+ cells problematic. The purpose of this study was to improve the detection of a low frequency of Ph+ cells. PATIENTS AND METHODS: We combined fluorescence in situ hybridization (FISH) with long-term colcemid exposure, capturing several hundred metaphases in bone marrow cultures (hypermetaphase FISH [HMF]). Using probes that identify Ph+ cells, HMF was compared with CG analysis in the follow-up evaluations of 51 patients with CML at various time points after allogeneic bone marrow transplant (BMT). RESULTS: Thirty-five patients never showed the presence of Ph+ cells by either method. In four patients, high frequencies of Ph+ cells were detected by both methods. In the remaining 12 patients, Ph+ cells were detected by HMF at time points after BMT when they were not detected by CG. In seven of the 12 patients, low but statistically significant frequencies of Ph+ cells (0.37% to 5.20%) were detected 3 months or later after BMT, and when no intervention was initiated, all seven patients later relapsed. Based on those data, an eighth patient with mixed chimerism and a similar HMF-detected Ph+ frequency (1.8% at 27 months after BMT) was reinfused with donor lymphocytes and achieved remission with 0% Ph+ cells studied by HMF (up to 50 months after BMT). Ph+ cells detected by HMF but not by CG less than 3 months after BMT disappeared on later examination in two of four patients. After detection of Ph+ cells by HMF only, the median time to cytogenetic progression (detection of Ph+ cells by CG) was 101 days. CONCLUSION: The results demonstrate the ability of HMF to detect low but clinically relevant levels of leukemic cells not detected by CG in transplant patients. The data indicate that HMF can detect low levels of Ph+ cells before standard cytogenetics at a time that may be useful in monitoring disease status and planning clinical interventions. (+info)
Mobilisation of haemopoietic progenitors in CML: a second course of intensive chemotherapy does not improve Ph-negativity in stem cell harvests.
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We collected peripheral blood stem cells (PBSC) in 19 early chronic phase CML patients following each of two consecutive cycles of intensive chemotherapy (CT) to evaluate whether an additional cycle of CT would increase Philadelphia (Ph)-negativity of the PBSC harvest. Autologous SCT (autoSCT) was performed if a major cytogenetic response (MCR) of the PBSC harvest was obtained. CT consisted of cytarabine 200 mg/ m2/day (days 1-7)/idarubicin 12 mg/m2/day (days 1-2) (cycle one) and cytarabine 2000 mg/m2/day (days 1-6)/amsacrine 120 mg/m2/day (days 1-3) (cycle two). One patient died of fungal pneumonia after the first cycle. Stem cells were harvested in 18 patients after cycle one and in 16 patients after cycle two. After the first cycle, all patients showed a cytogenetic response of their graft (MCR in eight patients: three complete, five partial), after cycle two, seven patients obtained an MCR (one complete, six partial). Seven patients became eligible for autoSCT. All patients proceeded with IFNalpha maintenance. Currently, 16 patients are alive. At the latest cytogenetic examination of bone marrow, four patients showed an MCR and four a minor response. In conclusion, although a second cycle of CT may contribute to elimination of leukemia residing in the patient, it appeared to be ineffective in improving the Ph-negativity of the PBSC graft. (+info)
A Philadelphia chromosome positive acute lymphoblastic leukemia of donor origin after allogeneic bone marrow transplantation for chronic myelogenous leukemia in chronic phase.
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We report here a case of donor cell leukemia in a female Ph-positive CML patient who received an allogeneic BMT from her HLA-identical brother in the chronic phase and subsequently developed a donor cell Ph-positive ALL. The number of cases of donor cell leukemia after BMT so far reported is less than 20 and in this case, as in the first cases reported by Marmont et aland McCane et al, the original leukemia and donor cell leukemia share the presence of a Ph chromosome. Furthermore, we analyzed the patient during different stages of her disease by RT-PCR and determined the type of bcr-abl junctions (M bcr-abl junction; b3a2 transcript, p210) in both the recipient and donor cell leukemia. (+info)
Collection of Ph-negative progenitor cells from interferon responsive patients with chronic myeloid leukemia: effect of granulocyte-colony-stimulating factor mobilization.
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BACKGROUND AND OBJECTIVE: The observation that patients with chronic myeloid leukemia (CML) may relapse following stem cell transplantation because of Philadelphia positive cells contaminating the graft have led to a variety of strategies to reduce this contamination. This study investigate the feasibility of collective, Ph-re cells from patients with CML in chronic phase. DESIGN AND METHODS: A total of 18 patients with chronic myeloid leukemia in chronic phase who had responded to varying degrees to treatment with interferon-a (IFN) were subjected to mobilization with granulocyte colony-stimulating factors and peripheral blood progenitor cell collection. Nine patients were in complete cytogenetic remission (CCR) and nine were partial responders. IFN was stopped 2 to 4 weeks before the procedure. G-CSF was given by subcutaneous injection once daily at a dose of 10 microg/kg. RESULTS: Five patients underwent one collection procedure only, 10 underwent two procedures and 3 patients had three collections. The median number of nucleated cells (NC) per patient collected was 10.2 x 10(8)/kg (4.4-19.7) and the median number of CD34(+) cells was 2.5 x 10(6)/kg (0.4-9.4). Analyzable cytogenetic data were available for 26/34 (76%) leukapheresis procedures. The median percentage of Ph- negative metaphases for patients in CCR was 100% (73-100). Patients not in CCR had a higher level of Ph-positive cells in their collections (median 23%, range 0-79%, p=0.01). Of the nine patients in CCR, 8 had at least one apheresis from which progenitor cells were 100% Ph-negative; conversely, patients not in CCR had detectable Ph-positive cells in every collection. Four patients have undergone autologous stem cell transplantation. INTERPRETATION AND CONCLUSIONS: It was possible to collect sufficient Ph negative progenitor cells from patients in CCR but collections from other patients contained significant numbers of Ph-positive cells. (+info)
BCR-ABL mediates arsenic trioxide-induced apoptosis independently of its aberrant kinase activity.
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In the prechemotherapy era arsenic derivatives were used for treatment of chronic myelogenous leukemia, a myeloproliferative disorder characterized by the t(9;22) translocation, the Philadelphia chromosome (Ph+). In acute promyelocytic leukemia response to arsenic trioxide (As2O3) has been shown to be genetically determined by the acute promyelocytic leukemia-specific t(15;17) translocation product PML/RARalpha. Hence, we reasoned that As2O3 might have a selective inhibitory effect on proliferation of BCR-ABL-expressing cells. Here, we report that: (a) As2O3 induced apoptosis in Ph+ but not in Ph- lymphoblasts; (b) enforced expression of BCR-ABL in U937 cells dramatically increased the sensitivity to As2O3; (c) the effect of As2O3 was independent of BCR-ABL kinase activity; and (d) As2O3 reduced proliferation of chronic myelogenous leukemia blasts but not of peripheral CD34+ progenitors. In summary, these data establish As2O3 as a tumor cell-specific agent, making its clinical application in Ph+ leukemia feasible. (+info)