Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Imatinib mesylate, an Abl-specific kinase inhibitor, produces sustained complete hematologic responses (CHR) and major cytogenetic responses (MCR) in chronic myeloid leukemia (CML) patients, but long-term outcomes in these patients are not yet known. This article reports the identification of clonal abnormalities in cells lacking detectable Philadelphia (Ph) chromosome/BCR-ABL rearrangements from seven patients with chronic- or accelerated-phase CML, who were treated with imatinib. All seven patients were refractory or intolerant to interferon therapy. Six of seven patients demonstrated MCR and one patient, who had a cryptic translocation, achieved low-level positivity (2.5%) for BCR-ABL by fluorescence in situ hybridization. The median duration of imatinib treatment before the identification of cytogenetic abnormalities in BCR-ABL-negative cells was 13 months. The most common cytogenetic abnormality was trisomy 8, documented in three patients. All patients had varying degrees of dysplastic morphologic abnormalities. One patient exhibited increased numbers of marrow blasts, yet consistently demonstrated no Ph-positive metaphases and the absence of morphologic features of CML. The presence of clonal abnormalities in Ph-negative cells of imatinib-treated CML patients with MCR and CHR highlights the importance of routine metaphase cytogenetic testing and long-term follow-up of all imatinib-treated patients.
Leukemia 2003 Mar
PMID:Demonstration of Philadelphia chromosome negative abnormal clones in patients with chronic myelogenous leukemia during major cytogenetic responses induced by imatinib mesylate. 1264 34

The c-Abl tyrosine kinase is inhibited by mechanisms that are poorly understood. Disruption of these mechanisms in the Bcr-Abl oncoprotein leads to several forms of human leukemia. We found that like Src kinases, c-Abl 1b is activated by phosphotyrosine ligands. Ligand-activated c-Abl is particularly sensitive to the anti-cancer drug STI-571/Gleevec/imatinib (STI-571). The SH2 domain-phosphorylated tail interaction in Src kinases is functionally replaced in c-Abl by an intramolecular engagement of the N-terminal myristoyl modification with the kinase domain. Functional studies coupled with structural analysis define a myristoyl/phosphotyrosine switch in c-Abl that regulates docking and accessibility of the SH2 domain. This mechanism offers an explanation for the observed cellular activation of c-Abl by tyrosine-phosphorylated proteins, the intracellular mobility of c-Abl, and it provides new insights into the mechanism of action of STI-571.
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PMID:A myristoyl/phosphotyrosine switch regulates c-Abl. 1265 40

Chronic myeloid leukaemia (CML) is a malignant disease of the bone marrow characterised by the presence of the Philadelphia (Ph) chromosome. About 20% of acute lymphoblastic leukaemia (ALL) patients also show this genetic abnormality. A new drug, imatinib (Glivec, Novartis Pharma AG, Basel, Switzerland, and formerly STI571) is having a profound effect on the treatment and management of all stages of CML and Philadelphia chromosome positive (Ph+) ALL. New treatment algorithms are being developed. Should imatinib replace or be combined with existing therapies? To address this question, we review the pros and cons of therapy with interferon-alpha (IFN-alpha), allogeneic transplantation, autologous transplantation, imatinib, and in the case of Ph+ ALL, chemotherapy and experimental approaches. Conservative and aggressive treatments will be discussed and new molecular methods of monitoring cytogenetic response and their significance will also be reviewed.
Leukemia 2003 Apr
PMID:Perspectives on the treatment of chronic phase and advanced phase CML and Philadelphia chromosome positive ALL(1). 1268 26

Imatinib mesylate is useful for facilitating allogeneic stem cell transplantation (allo-SCT) in advanced-phase chronic myelogenous leukaemia (AP-CML) patients. However, although the side-effects of imatinib are usually minor, cardiac morbidity can develop as a latent adverse effect post SCT when a myeloablative SCT is given to patients taking imatinib. Two AP-CML patients who were treated with imatinib manifested severe cardiac dysfunction after an allo-SCT, whereas cardiac morbidity was not observed in 45 other patients who had not received imatinib. It would appear that exposure to imatinib may have an adverse impact on the heart in AP-CML patients who receive an allo-SCT conditioned with busulphan/cyclophosphamide.
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PMID:Cardiac morbidity in advanced chronic myelogenous leukaemia patients treated by successive allogeneic stem cell transplantation with busulphan/cyclophosphamide conditioning after imatinib mesylate administration. 1271 70

Interactions between the Bcr/Abl kinase inhibitor STI571 (Gleevec, imatinib mesylate) and histone deacetylase inhibitors (HDIs) have been examined in STI571-sensitive and -resistant Bcr/Abl(+) human leukemia cells (K562 and LAMA 84). Cotreatment of K562 cells with 250 nM imatinib mesylate and 2.0 micro M suberoylanilide hydroxamic acid (SAHA) for 24 h, exposures that were minimally toxic alone, resulted in a marked increase in mitochondrial damage (e.g., cytochrome c, Smac/DIABLO, and apoptosis-inducing factor release), caspase activation, and apoptosis. Similar events were observed in other Bcr/Abl(+) cells (i.e., LAMA 84), and in cells exposed to STI571 in combination with the HDI sodium butyrate. Coexposure of cells to HDIs in conjunction with STI571 resulted in multiple perturbations in signaling and cell cycle-regulatory proteins, including down-regulation of Raf, phospho-mitogen-activated protein kinase kinase (MEK), phospho-extracellular signal-regulated kinase (ERK), phospho-Akt, phospho-signal transducers and activators of transcription 5, cyclin D1, and Mcl-1, accompanied by dephosphorylation and cleavage of retinoblastoma protein and a striking increase in phosphorylation of c-Jun NH(2)-terminal kinase. Coexposure of Bcr/Abl(+) cells to STI571 also blocked SAHA-mediated induction of p21(CIP1) and resulted in down-regulation of Bcr/Abl protein expression. STI571 and SAHA also interacted synergistically to induce apoptosis in STI571-resistant K562 and LAMA 84 cells that display increased Bcr/Abl protein expression. Lastly, inducible expression of a constitutively active MEK1/2 construct significantly attenuated SAHA/STI571-mediated apoptosis in K562 cells, implicating disruption of the Raf/MEK/ERK axis in synergistic antileukemic effects of this drug combination. Together, these findings indicate that combined exposure of Bcr/Abl(+) cells to the kinase inhibitor STI571 and HDIs leads to diverse perturbations in signaling and cell cycle-regulatory proteins, associated with a marked increase in mitochondrial damage and cell death. They also raise the possibility that this strategy may be effective in some Bcr/Abl(+) cells that are resistant to STI571 through increased Bcr/Abl expression.
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PMID:Histone deacetylase inhibitors promote STI571-mediated apoptosis in STI571-sensitive and -resistant Bcr/Abl+ human myeloid leukemia cells. 1272 28

Imatinib mesylate (Glivec) is a selective inhibitor of bcr-abl tyrosine kinase, the product of the Philadelphia chromosome, which is the hallmark of chronic myeloid leukaemia (CML). With imatinib, complete cytogenetic response (CCR) can be achieved in over 70% of newly diagnosed patients with CML. However, the optimal long-term management of patients who achieve CCR after imatinib is unknown. With longer follow-up, it is anticipated that some patients are likely to progress and become candidates for autologous transplantation. We studied filgrastim (r-metHuG-CSF) mobilisation of peripheral blood stem cells (PBSC) in 32 patients who have achieved CCR with imatinib. Our data demonstrate that (1) the target CD34(+) cell yields of >/=2.0 x 10(6)/kg were attained with filgrastim 10 microg/kg/day, in 9/18 (50%) of patients during uninterrupted imatinib therapy, and in 10/14 (70%) when imatinib was temporarily withheld. The median CD34(+) cell yield per aphaeresis was 0.70 x 10(6)/kg (range 0.14-2.18) and 2.90 x 10(6)/kg (range 0.15-8.71) in the two groups, respectively (P&<0.005). (2) The cell yields did not correlate with the duration of imatinib administration. (3) There was no impact of the mobilisation procedure on the level of leukaemia as measured by serial blood bcr-abl levels using real-time quantitative PCR with either protocol. (4) bcr-abl remained detectable at low levels in the harvests in most but not all patients. In conclusion, filgrastim can safely be used to mobilise PBSC in patients who have achieved CCR with imatinib, but CD34(+) cell yields are significantly improved when imatinib is temporarily withheld.
Leukemia 2003 May
PMID:Successful peripheral blood stem cell mobilisation with filgrastim in patients with chronic myeloid leukaemia achieving complete cytogenetic response with imatinib, without increasing disease burden as measured by quantitative real-time PCR. 1275 Jun 92

Cancer research within the last decades elucidated signaling pathways and identified genes and proteins that lead or contribute to malignant transformation of a cell. Discovery of the Bcr-Abl oncoprotein as the molecular abnormality causing chronic myeloid leukemia (CML) paved the way for the development of a targeted anticancer therapy. The substantial activity of imatinib mesylate (STI571, Glivec) in CML and Philadelphia (Ph)-chromosome positive acute lymphoblastic leukemia (Ph+ ALL) changed the therapeutic approach to Ph+ leukemia and rang the bell for a new era of anticancer treatment. However, when the phenomenon of relapse occurred despite continued imatinib treatment, we had to learn the lesson that imatinib can select for a resistant disease clone. If such a clone still depends on Bcr-Abl, it either carries a BCR-ABL point mutation that prevents binding of the drug or expresses the fusion protein at high levels. Alternatively, leukemia cells that harbor secondary genetic alterations resulting in Bcr-Abl-independent proliferation are selected for their growth advantage in the presence of imatinib. Point mutations in the BCR-ABL kinase domain prevent binding of imatinib but still allow binding of ATP, thus retaining Bcr-Abl kinase activity. Mutated BCR-ABL is frequently detected in cases of imatinib-resistant Ph+ leukemia and therefore represents the main challenge for the investigation of alternative strategies to either overcome resistance or to prevent the emergence of a resistant leukemic clone.
Leukemia 2003 May
PMID:Resistance of Philadelphia-chromosome positive leukemia towards the kinase inhibitor imatinib (STI571, Glivec): a targeted oncoprotein strikes back. 1275 Jun 93

Imatinib mesylate, a competitive inhibitor of Abl tyrosine kinase, is highly effective for the early stages of chronic myelogenous leukemia (CML), but remissions induced in advanced-phase CML and Philadelphia chromosome-positive (Ph+) acute lymphoblastic leukemia tend to be relatively short-lived. Therefore, the search for agents that enhance the anti-Ph+ effect of imatinib mesylate is warranted. We investigated the combined effects of imatinib mesylate and the third-generation bisphosphonate zoledronate (ZOL) on Ph+ leukemias, because ZOL inhibited the prenylation of Ras-related proteins downstream of Bcr/Abl. First, we identified the potency of ZOL in vitro against human leukemic cell lines, including 2 Ph+ and a P-glycoprotein-overexpressing leukemic cell line. ZOL was also effective in vivo because as it prolonged the survival of nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice who were given xenografts with Ph+ BV173 leukemic cells. Next, we showed the in vitro synergistic effects with ZOL and imatinib mesylate for Ph+ cell lines. ZOL combined with imatinib mesylate showed synergistic effects in vivo that prolonged the survival of mice inoculated with BV173. ZOL only minimally inhibited the growth of normal hematopoietic progenitors in vitro, and mice receiving ZOL or imatinib mesylate or both tolerated these treatments well. These findings indicate that ZOL is a potent antileukemic agent that augments synergistically the anti-Ph+ leukemia activity of imatinib mesylate.
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PMID:The third-generation bisphosphonate zoledronate synergistically augments the anti-Ph+ leukemia activity of imatinib mesylate. 1276 30

In BCR-ABL-positive cells, the transcription factor STAT-5 is constitutively activated by tyrosine phosphorylation. STAT-5 activation results in upregulation of bcl-X(L) and increased resistance to induction of apoptosis. Here, we investigated the effects of imatinib mesylate and cytosine arabinoside (Ara-C) on STAT-5 tyrosine-phosphorylation, cellular proliferation and induction of apoptosis in cell lines and primary hematopoietic cells. Imatinib mesylate treatment strongly suppressed STAT-5 tyrosine-phosphorylation in K562 and primary CML blasts. In contrast to JAK-2 and PI-3-kinase inhibition, exposure of K562 cells to imatinib mesylate resulted in obvious suppression of proliferation. Reduced cell growth was due to specific induction of caspase activation followed by apoptotic cell death. In addition, we investigated the effects of Ara-C on STAT-5 tyrosine-phosphorylation. Exposure to Ara-C resulted in significant downregulation of STAT-5 tyrosine-phosphorylation and inhibition of DNA binding. Treatment of K562 cells with Ara-C in combination with imatinib mesylate revealed synergistic effects at the level of STAT-5 tyrosine-phosphorylation and DNA binding, Hck tyrosine-phosphorylation, cell growth and induction of apoptosis. Overall, in this report we demonstrate that STAT-5 tyrosine-phosphorylation is a specific target of imatinib mesylate and Ara-C. Our results suggest that, in combination therapy, inhibition of STAT-5 tyrosine-phosphorylation may be responsible for synergistic or additive effects on BCR-ABL-positive cells.
Leukemia 2003 Jun
PMID:In BCR-ABL-positive cells, STAT-5 tyrosine-phosphorylation integrates signals induced by imatinib mesylate and Ara-C. 1276 61

Chronic myeloid leukemia (CML) is arguably the best understood of all human malignancies. Its origins in the hematopoietic stem cell can be traced to a reciprocal translocation involving chromosomes 9 and 22, dubbed the Philadelphia chromosome, which is observed in essentially all patients. The resulting fusion gene, BCR/ABL, encodes an activated tyrosine kinase that can act alone to induce a CML-like syndrome in mouse models. These animal models have validated BCR/ABL as a target for the development of specific pharmaceutical inhibitors. The kinase inhibitor imatinib mesylate (Gleevec) is highly specific, effective, and minimally toxic, but may not effect cures as a single agent, particularly in patients with accelerated and blast-phase disease. Resistance to imatinib can confound therapy. Surprisingly, a high percentage of resistant cases manifest intact or augmented BCR/ABL signaling, suggesting that this oncoprotein, or signaling pathways emanating from it, remain viable targets. Combination chemotherapy is under active investigation, and among the most compelling strategies is dual treatment with agents that both target BCR/ABL signal transduction. BCR/ABL activates Ras, and compounds designed to antagonize Ras function called farnesyl transferase inhibitors (FTIs) have shown potent activity in vitro and in animal models of BCR/ABL-induced leukemia. Initial clinical trials in patients with refractory acute myeloid leukemia and CML in blast crisis have shown significant activity, suggesting that trials combining imatinib and FTIs are warranted.
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PMID:Towards combination target-directed chemotherapy for chronic myeloid leukemia: role of farnesyl transferase inhibitors. 1278 69


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