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At least 361 records · Page 20Linked to original sources
PubMed2006

Epigenetic heterochromatin markers distinguish terminally differentiated leukocytes from incompletely differentiated leukemia cells in human blood.

OBJECTIVE: During terminal cell differentiation, nuclear chromatin becomes condensed and the repertoire of epigentic heterochromatin proteins responsible for chromatin condensation is dramatically changed. In order to identify the chromatin regulatory factors associated with incomplete cell differentiation and impaired chromatin condensation in hematological malignancies, we examined expression levels of major heterochromatin proteins in normal blood cells and cells derived from a number of chronic and acute myeloid leukemia patients exhibiting different degrees of differentiation. METHODS: We used immunoblotting and immunofluorescence to examine the levels and localization of epigenetic heterochromatin factors in isolated cell nuclei and fractionated peripheral blood cells. RESULTS: While the major epigenetic heterochromatin factor, histone H3 methylated at lysine 9, is present in all cell types, its main counterparts, nonhistone proteins, heterochromatin proteins 1 (HP1) alpha, beta, and gamma, are dramatically reduced in peripheral blood leukocytes of normal donors and chronic myeloid leukemia patients, but are substantially increased in the blood of accelerated phase and blast crisis patients. In the terminally differentiated cells, nuclear chromatin accumulates a nucleocytoplasmic serpin, monocyte and neutrophil elastase inhibitor (MNEI). HP1 and MNEI levels inversely correlate in a number of normal and leukemia myeloid cells and show strikingly opposite coordinated changes during differentiation of U937 cell line induced by retinoic acid. CONCLUSIONS: Our results suggest that repression of HP1 and accumulation of MNEI are linked to terminal cell differentiation and that their levels may be monitored in blood cell populations to detect transitions in cell differentiation associated with leukemia progression and treatment.

Antineoplastic Agents↗
PubMed2006

Chronic myeloid leukemia cells express tumor-associated antigens eliciting specific CD8+ T-cell responses and are lacking costimulatory molecules.

Specific immunotherapies for patients with chronic myeloid leukemia (CML) might eliminate residual CML cells after therapy with imatinib or chemotherapy and might enhance a specific graft-versus-leukemia effect after allogeneic stem cell transplantation. Here, we investigated the mRNA expression and T-cell recognition of tumor-associated antigens or leukemia-associated antigens (LAAs) in 34 patients with CML. Several LAAs are expressed in CML and therefore are candidate structures for specific immunotherapies: bcr-abl (100%), G250 (24%), hTERT (53%), MPP11 (91%), NEWREN60 (94%), PRAME (62%), Proteinase3 (71%), RHAMM/CD168 (83%), and WT1 (53%), but not BAGE, MAGE-A1, SSX2, or NY-ESO-1. The frequency of mRNA expression of RHAMM/CD168, Proteinase3, and PRAME was higher in acceleration phase and blast crisis. In flow cytometry, CD34+ progenitor cells typed positive for HLA molecules but were deficient for CD40, CD80, CD83, and CD86. However, RHAMM/CD168 R3-peptide (ILSLELMKL)-specific T-cell responses in CML patients were demonstrated by ELISPOT analysis and specific lysis of RHAMM/CD168 R3-pulsed T2 cells and CD34+ CML cells in chromium-51 release assays. RHAMM-R3-specific T cells could be phenotyped as CD8+R3*tetramer+CD45RA+CCR7-CD27- early effector T cells by tetramer staining. Therefore, vaccination strategies inducing such RHAMM-R3-directed effector T cells might be a promising approach to enhance specific immune responses against CML cells.

Adult↗
PubMed2004

Imatinib mesylate (STI571) prevents the mutator phenotype of Bcr-Abl in hematopoietic cell lines.

Progression of CML from chronic phase to blast crisis is accompanied by accumulating genetic alterations. To analyze whether this abnormality can be prevented by inhibition of Bcr-Abl, we measured the frequency of spontaneous and irradiation-induced HPRT mutations in cells treated with or without imatinib mesylate (Gleevec, STI571). Imatinib treatment of cells expressing Bcr-Abl reversed the mutation frequency to a value comparable to that of Bcr-Abl negative cells. Experiments with a Bcr-Abl deletion mutant indicate that in addition to the kinase activity, protein-protein interactions are required for induction of the mutator phenotype by Bcr-Abl.

Animals↗
PubMed2003

BCR/ABL activates mdm2 mRNA translation via the La antigen.

In a BCR/ABL-expressing myeloid precursor cell line, p53 levels were markedly downmodulated. Expression of MDM2, the negative regulator of p53, was upregulated in a tyrosine kinase-dependent manner in growth factor-independent BCR/ABL-expressing cells, and in accelerated phase and blast crisis CML samples. Increased MDM2 expression was associated with enhanced mdm2 mRNA translation, which required the interaction of the La antigen with mdm2 5' UTR. Expression of MDM2 correlated with that of La and was suppressed by La siRNAs and by a dominant negative La mutant, which also enhanced the susceptibility to drug-induced apoptosis of BCR/ABL-transformed cells. By contrast, La overexpression led to increased MDM2 levels and enhanced resistance to apoptosis. Thus, La-dependent activation of mdm2 translation might represent an important molecular mechanism involved in BCR/ABL leukemogenesis.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Extramedullary T lymphoblastic transformation of chronic myeloid leukaemia occurring after double allogeneic transplantation.

The clinical course of chronic myeloid leukaemia (CML) is characterised by a chronic phase followed by an acute phase or blast crisis. Lymphoid transformation accounts for 20-30% of such events, with the majority of cases being of B cell origin. Extramedullary transformation occurs in approximately 10% of cases. We report a case of T cell lymphoblastic transformation in CML presenting as an extramedullary mass after allogeneic stem cell transplant. This case supports the growing evidence that CML arises in the pluripotent stem cell.

Adult↗
PubMed1997

Absence of microsatellite instability during the progression of chronic myelocytic leukemia.

Microsatellites are highly polymorphic, short-tandem repeat sequences dispersed throughout the genome. To test the occurrence of genetic instability in the progression of chronic myelocytic leukemia (CML), we studied microsatellite instability (MSI) in 17 patients with CML. The DNAs from both chronic phase and blast crisis were analyzed at 10 loci. No MSI was observed in any of the 17 cases of blast crisis. These results indicate that MSI is rare and is not associated with progression to blast crisis in most cases of CML.

Blast Crisis↗
PubMed2001

Proliferating status of peripheral blood progenitor cells from patients with BCR/ABL-positive chronic myelogenous leukemia.

To investigate the mechanisms behind the leukemic expansion of BCR/ABL-positive chronic myelogenous leukemia (CML), we examined the cell cycle status of hematopoietic progenitor cells from peripheral blood (PB) and bone marrow (BM) of 37 patients with newly diagnosed BCR/ABL-positive CML. We found a high proportion of 12.51 +/- 1.19% of CD34+ peripheral blood progenitor cells (PBPC) in S/G2M phase. Comparison of PB and BM from 19 cases revealed similar proliferation rates (10.74 +/- 1.41% vs 15.97 +/- 1.95%). Furthermore, even primitive CD34+/CD38- PBPC displayed high proliferation rates (17.45 +/- 2.98%) in 10 cases examined. In contrast, PBPC from 11 patients with BCR/ABL-negative myeloproliferative disorders were almost noncycling (S/G2M 1.46 +/- 0.47%). When matched pairs of PB and BM from six patients with BCR/ABL-negative myeloproliferative disorders were examined, only 0.89 +/- 0.41% of the CD34+ PBPC, but 8.29 +/- 3.13% CD34+ cells from BM were in S/G2M phase. Consistently, as compared to 19 patients with newly diagnosed BCR/ABL-positive CML, a significantly lower PB/BM ratio of CD34+ cells in S/G2M phase was found in these six patients with BCR/ABL-negative myeloprolifrative disorders. Administration of the tyrosine kinase inhibitor STI571 to 13 patients with CML in chronic phase, accelerated phase, or blast crisis lead to an inhibition of PBPC proliferation within a few days. Interestingly, CD34+ hematopoietic progenitor cells from BM remained proliferating in five cases examined, indicating that CML PBPC are more easily inhibited by STI571 as compared to CD34+ CML hematopoietic progenitor cells from BM. These data suggest that BCR/ABL leads to an enhanced cell cycle activation of CD34+ cells, which seems to be, at least in part, independent of additional factors provided by the bone marrow microenvironment.

Adult↗
PubMed2002

Stevens-Johnson syndrome after treatment with STI571: a case report.

Between seven and 21% of patients treated with the specific tyrosine kinase inhibitor STI571 have been reported to develop mild-to-moderate severity of adverse cutaneous reactions. We report a patient in the blast crisis phase of chronic myeloid leukaemia who developed a life-threatening cutaneous reaction, Stevens-Johnson syndrome, following 1 week of STI571 therapy. This report may serve to remind the clinician about the possible severe cutaneous side-effects of STI571 before instituting more extensive clinical application of this agent in the future.

Adult↗
PubMed2003

Molecular mechanisms of transformation by the BCR-ABL oncogene.

The BCR-ABL oncogene is generated by the Philadelphia chromosome (Ph) translocation, fusing the BCR gene to the ABL gene. The BCR-ABL fusion protein has elevated ABL tyrosine kinase activity that is critical for transformation of hematopoietic cells. Chronic myelogenous leukemia (CML) cells transformed by BCR-ABL show reduced growth factor requirements and apoptosis, as well as enhanced viability and altered adhesion. The elevated ABL kinase activity leads to chronic activation of signaling pathways that are required for all aspects of transformation. Progression of the disease from chronic phase to blast crisis correlates with additional cytogenetic alterations that are likely to contribute to the failure of traditional therapy. This review describes molecular mechanisms that are thought to be important for transformation by the BCR-ABL oncoprotein and points at pathways for targeted drug development in the treatment of CML.

Cell Transformation, Neoplastic↗
PubMed2003

Prediction of response to imatinib by cDNA microarray analysis.

Clinical introduction of imatinib mesylate (Gleevec) (formerly STI571) has marked a major advance in the treatment of chronic myeloid leukemia (CML), inducing major cytogenetic response in 60% to 80% of patients with chronic-phase disease. Since its remarkable effect has made it difficult to decide the timing for potentially curative but life-threatening stem cell transplantation (SCT), it would be very useful to predict imatinib's effectiveness in individual patients beforehand. We analyzed gene expression profiles of peripheral leukemia cells from 18 CML patients (16 chronic phase, two blast crisis) who were treated with imatinib alone. cDNA microarrays representing 23,040 genes identified 79 genes that were expressed differentially between cytogenetically defined responders and nonresponders to imatinib. We then established a "prediction score" system using 15 or 30 of these genes that could clearly separate the responder group from the nonresponder group. Four additional patients' responses to imatinib were successfully predicted, validating the process. Thus, gene-expression profiles can predict clinical effectiveness of CML to imatinib, and may eventually lead to the achievement of "personalized therapy" for this disease.

Adult↗
PubMed2003

Imatinib in patients with newly diagnosed chronic-phase chronic myeloid leukemia.

The International Randomized Study of Interferon and STI571 (IRIS) study prospectively compared imatinib with interferon-alpha/low-dose cytarabine (IFN/LDAC) in 1,106 newly diagnosed patients with Philadelphia chromosome-positive chronic myeloid leukemia (CML). Patients not responding to or intolerant of their assigned treatment were allowed to cross over. At 18 months, the projected probability of achieving a complete cytogenetic response was 76.2% for imatinib and 14.5% for IFN/LDAC, respectively (P <.01). Freedom from progression to accelerated phase or blast crisis was 96.7% for imatinib versus 91.5% for IFN/LDAC (P <.01). At the time of the analysis, 85.7% of imatinib-treated patients continued on first-line therapy, but only 10.8% of patients continued with IFN/LDAC. Most cross-overs to imatinib were due to interferon-intolerance. Overall survival was not different in the two groups at 19 months, reflecting efficient rescue of IFN/LDAC failures with imatinib. Imatinib should now be considered the standard therapy for newly diagnosed patients with CML.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1985

Cell lines and clinical isolates derived from Ph1-positive chronic myelogenous leukemia patients express c-abl proteins with a common structural alteration.

The Philadelphia chromosome (Ph1), observed in greater than 90% of chronic myelogenous leukemia (CML) patients, results from a specific chromosomal translocation involving the c-abl gene. The translocation breakpoint occurs near c-abl and correlates with the production of an altered c-abl mRNA. In the CML-derived cell line K562, Ph1 is accompanied by a structurally altered c-abl protein (P210c-abl) with in vitro tyrosine kinase activity not detected with the normal c-abl protein (P145c-abl). We have examined c-abl proteins in other Ph1-positive CML cell lines and found that they all express P210c-abl. P210c-abl was also detected in bone marrow cells from CML patients with Ph1 in the accelerated and blast crisis phases of the disease. Comparison of the [35S]methionine-labeled tryptic peptides generated from the normal P145c-abl and P210c-abl showed that they have closely related structures, but additional polypeptide sequences are present in P210c-abl. Based on these results we propose that translocation of c-abl in Ph1-positive CML results in the creation of a chimeric gene leading to the production of a structurally altered c-abl protein with activated tyrosine kinase activity. The altered P210 c-abl protein is strongly implicated in the pathogenesis of CML.

Cell Line↗
PubMed2002

Quantitative monitoring of BCR/ABL transcript during STI-571 therapy.

PCR for the BCR/ABL fusion transcript provides a highly sensitive and specific method for detecting minimal residual disease in patients with chronic myeloid leukemia (CML). We sought to determine if quantitative PCR measurement of peripheral blood BCR/ABL transcript can be used to monitor response in CML patients with clinically evident disease while receiving the protein tyrosine kinase inhibitor STI-571. Serial bone marrow cytogenetics and peripheral blood BCR/ABL mRNA levels were measured in 17 patients [9 with chronic phase (CP) and 8 with accelerated phase or blast crisis (AP/BC)] during 1 year of treatment. Overall, quantitative PCR BCR/ABL transcript level decreased by a median of 0.9 log during the first 3 months, and by 1.6 logs by 12 months. Among cytogenetic responders (6 CP and 2 AP/BC), median BCR/ABL copy number was 0.9 and 2.1 logs lower than baseline after 3 and 12 months of treatment, respectively. No patient became PCR-negative for BCR/ABL. Among cytogenetic non-responders, BCR/ABL transcript level decreased by 0.4 logs after 3 months, with no subsequent reductions. At study entry, BCR/ABL expression in cytogenetic responders and non-responders was similar. However, BCR/ABL expression became significantly different 3 months after treatment (p = 0.02), and increasingly different with continued therapy (p = 0.04, 0.005, 0.0008 at 6, 9 and 12 months, respectively). Our results demonstrate that PBMC BCR/ABL mRNA levels correlate well with response to STI-571. This non-invasive, rapid and sensitive PCR-based assay can be used to monitor response to STI-571.

Adult↗
PubMed1983

Plasma fibronectin in myeloproliferative disorders and chronic granulocytic leukaemia.

A significant reduction of plasma fibronectin levels was found in polycythaemia vera and myelofibrosis, the lowest levels being found in patients with marked splenomegaly. Plasma fibronectin concentration was normal in essential thrombocythaemia, and only modest reduction was seen in chronic granulocytic leukaemia in either controlled chronic phase or blast cell crisis. In a patient with myelofibrosis, the plasma fibronectin rose from less than 100 mg/l to 177 mg/l after splenectomy. Possible explanations include increased consumption of plasma fibronectin in the expanded mononuclear phagocyte system present in the liver and spleen, reduced hepatic synthesis, and the clearance of circulating immune complexes. Low plasma fibronectin concentrations may increase susceptibility to infection.

Adult↗
PubMed1991

Second transplants for leukaemic relapse after bone marrow transplantation: high early mortality but favourable effect of chronic GVHD on continued remission. A report by the EBMT Leukaemia Working Party.

Ninety second bone marrow transplants (BMT) for relapsed leukaemia were carried out in 30 European BMT centres. At second BMT, after further treatment in 64 cases, 43 patients were in complete remission or in chronic phase of CML, and 47 were in continuing relapse, accelerated phase or blast crisis of CML. Seventy patients died, 37 from early transplant-related toxicity and relapse or failure to eradicate leukaemia which occurred in 23. There were 20 survivors. The actuarial disease-free survival was 11% with a relapse probability of 69% at 3 years. Associated with reduced graft-versus-host disease (GVHD) prophylaxis during second BMT, the incidence and severity of acute and chronic GVHD, was increased when compared with the first BMT (P = 0.02, and 0.002 respectively for acute and chronic GVHD). In multivariate analysis survival was shown to be favoured by a prolonged interval between first and second BMT (relative risk 1.3/year, P = 0.02), and no or mild chronic GVHD following first BMT (relative risk 2.3, P = 0.02). Continuing remission was favoured by chronic GVHD occurring after second BMT (relative risk 8.1, P = 0.004). These results confirm the high treatment-related mortality following second BMT, but identify superior survival in selected patients. Improved results might be achieved by further reduction in preparative regimen intensity, and increasing graft-versus-leukaemia reactivity.

Acute Disease↗
PubMed1981

The effect of daily low dose gamma irradiation on growth and differentiation of human myeloid leukaemic bone marrow in diffusion chambers.

Bone marrow from each of 8 untreated patients with myeloproliferative disorders was grown in diffusion chambers in 760 rad total body irradiated rats. Rats were then exposed to 11.5, 57.5, or 108.5 rad daily for 14-2l d and cell growth compared to that detected in unirradiated chambers. Cells from acute myelogenous leukaemia patients exposed to 11.5 rad per d grew for 11-21 d and there was no consistent stimulation of differentiation of immature granulocytic cells to mature granulocytes that was attributable to irradiation. Cells from a chronic myeloid leukaemia patient in chronic phase or blast crisis, and a polycythaemia vera patient with myeloid metaplasia showed significant morphologic differentiation from immature to mature granulocytes in control chambers with no additional effect of daily irradiation. Marrow specimens from 2 AML patients exposed to each of 3 daily dose fractions over 14 d revealed a dose-dependent decrease in immature granulocytes with no persistent increase in mature granulocytes. In both irradiated and control chambers, macrophages increased over 21 d. Thus, cells from patients with myeloproliferative disorders may not necessarily differentiate to mature granulocytes following in vivo exposure to ionizing irradiation.

Adult↗
PubMed2004

Roles of Bim in apoptosis of normal and Bcr-Abl-expressing hematopoietic progenitors.

Bcr-Abl kinase is known to reverse apoptosis of cytokine-dependent cells due to cytokine deprivation, although it has been controversial whether chronic myeloid leukemia (CML) progenitors have the potential to survive under conditions in which there are limited amounts of cytokines. Here we demonstrate that early hematopoietic progenitors (Sca-1(+) c-Kit(+) Lin(-)) isolated from normal mice rapidly undergo apoptosis in the absence of cytokines. In these cells, the expression of Bim, a proapoptotic relative of Bcl-2 which plays a key role in the cytokine-mediated survival system, is induced. In contrast, those cells isolated from our previously established CML model mice resist apoptosis in cytokine-free medium without the induction of Bim expression, and these effects are reversed by the Abl-specific kinase inhibitor imatinib mesylate. In addition, the expression levels of Bim are uniformly low in cell lines established from patients in the blast crisis phase of CML, and imatinib induced Bim in these cells. Moreover, small interfering RNA that reduces the expression level of Bim effectively rescues CML cells from apoptosis caused by imatinib. These findings suggest that Bim plays an important role in the apoptosis of early hematopoietic progenitors and that Bcr-Abl supports cell survival in part through downregulation of this cell death activator.

Animals↗
PubMed2000

Histiocytic lymphoma presenting as a testicular tumour and terminating in acute monoblastic leukaemia.

A 58 year old man presented in 1995 with a swollen testicle. After orchidectomy, a diagnosis of poorly differentiated lymphoma was made. Lymphoid, epithelial, and seminoma markers were all negative. Six months later he developed a buccal lesion, which was biopsied and reported as a high grade non-Hodgkin's lymphoma. It responded completely to chemotherapy but within a year he developed a forearm swelling, which was biopsied and imprints made before fixation of the material. Immunocytochemistry on the imprints showed positivity with antibodies to CD4, CD68, and muramidase, and the non-specific esterase cytochemical stain was strongly positive, leading to a diagnosis of true histiocytic lymphoma. Despite further treatment, the patient entered a terminal acute leukaemic phase, the blasts marking as monoblasts. Review of all the biopsies, including molecular investigations and further immunohistochemistry studies performed retrospectively on the original biopsy, demonstrated that this was the same malignant cell line throughout, and we conclude that this is a case of histiocytic lymphoma, initially presenting as a testicular tumour and terminating in acute monoblastic leukaemia. A diagnosis of histiocytic lymphoma should be considered when lymphoid markers are negative in an apparent lymphoma, but should not be made without recourse to appropriate immunophenotypic and molecular studies.

Disease Progression↗