Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0023473 (chronic myeloid leukemia)
 18,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

One of the undoubted major breakthroughs in the recent treatment of cancer is imatinib, a tyrosine-kinase inhibitor of the bcr-abl fusion protein, the stem-cell factor receptor c-kit (KIT) and the platelet-derived growth-factor receptor. The successes obtained with imatinib in the treatment of chronic myeloid leukaemia (CML), gastrointestinal stroma-cell tumours (GIST), and dermatofibrosarcoma protuberans, demonstrate that targeted therapy with a rationally designed, small, synthetic molecule can be highly successful. However, experience so far with imatinib in KIT-positive tumours indicates that imatinib seems only to be effective in those tumours with a gain-of-function mutation in c-kit. There are arguments in favour of investigating a combined therapy of imatinib and classical chemotherapy.
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PMID:[New oncological treatment principle with imatinib]. 1460 47

Modulation of the signaling pathways that are aberrant in cancer cells has the potential to provide an effective nontoxic approach to patient management in a broad range of cancers. This quest has taken a major leap forward with the demonstration that STI-571 (imatinib mesylate) induces clinical and molecular remissions in the majority of patients with interferon-refractory chronic myelogenous leukemia and gastrointestinal stromal tumors through inhibition of the Bcr/Abl fusion protein required for the initiation and progression of chronic myelogenous leukemia and inhibition of a mutant, activated c-kit present in gastrointestinal stromal tumors. Support for the concept of targeting products of fusion genes found in specific cancers was first provided by the efficacy of all-trans retinoic acid in acute promyelocytic leukemia where the RARalpha all-trans retinoic acid target is the target of multiple different chromosomal rearrangements. In breast cancer, trastuzumab, which alters the function of the HER2 proto-oncogene overexpressed in a portion of breast cancers, provides an additional example of targeting specific molecular aberrations present in cancer cells. Although the target for these signal transduction modulators is functional in normal cells, acceptable therapeutic indices sufficient to prevent tumor growth without unacceptable toxicities have been observed. Whether STI-571 and other signal transduction modulators also target the stroma, and specifically the neovasculature, in addition to the tumor remains an open question. The presence of the target in the cancer cells or in the surrounding stroma appears to be required but not sufficient for the action of molecular therapeutics. Thus, linking molecular diagnostics to identify patients where the target is amplified or activated and driving the pathophysiology of the patients' tumor to effective molecular therapeutics will be necessary to translate these concepts into approaches that will alter the outcome for breast cancer patients. This review will focus on the phosphatidylinositol 3-kinase pathway and novel molecules targeting this pathway to illustrate the questions and challenges underlying the implementation of molecular therapeutics in breast cancer.
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PMID:Linking molecular diagnostics to molecular therapeutics: targeting the PI3K pathway in breast cancer. 1461 30

Imatinib mesylate targets the adenosine triphosphate (ATP)-binding sites of the protein tyrosine kinase domains associated with Bcr-abl, the platelet-derived growth factor (PDGF) and c-kit. In idiopathic myelofibrosis (IMF) PDGF is considered to be one of the growth factors responsible for the development of bone marrow fibrosis. Recently, it has been shown that imatinib has antifibrogenic effect on bone marrow fibrosis in chronic myelogenous leukemia. Treatment with imatinib alone in IMF has been associated with significant side effects. In this study, the safety and efficacy of imatinib therapy in IMF, either administered as a single agent or in combination with hydroxyurea (HU) and/or alpha-interferon (IFN-alpha) are evaluated. Eleven patients (median age, 63 years; range, 33-82 years) with IMF (n = 8) or postpolycythemic myelofibrosis (PPMF) (n = 3) were studied All patients had been treated with HU (n = 9) and/or IFN (n = 7) before study entry. In all but one patient, treatment with these agents was discontinued when imatinib therapy was instituted. One patient continued IFN when treatment with imatinib was started. Imatinib was given at a dose of 400 mg/day. Nine patients were in an advanced disease phase. The patients have been followed for a median period of 2 months (range, 0.5-12 months). Treatment with imatinib has been stopped in six patients (55%), because of overt side effects (n = 4), recurrence of transitory dizziness and visual defects owing to a rising platelet count (n = 1), or the occurrence of an acute subdural hemorrhage that was evacuated without neurological deficits (n = 1). In nine patients imatinib treatment was followed by a rise in leukocyte and platelet counts that required combination with HU or IFN. The combined treatment modalities were followed by a rapid decrease in cell counts and were well tolerated apart from IFN side effects. A beneficial effect of imatinib was documented in three patients. It is concluded that leukocytosis and thrombocytosis are seen in most patients with myelofibrosis during treatment with imatinib. Combination therapy with HU or IFN seems safe and well tolerated and followed by a decrease in disease activity. A subgroup of patients in an early disease phase might benefit from imatinib therapy alone.
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PMID:Imatinib mesylate in idiopathic and postpolycythemic myelofibrosis. 1463 3

The Philadelphia chromosome found in leukemia cells of chronic myelogenous leukemia (CML) patients is produced by translocation between chromosomes 9 and 22, resulting in expression of a chimera protein of Bcr and Abl kinase in the cytoplasm. Bcr-Abl kinase attracted oncology researchers as a molecular target for CML therapy, and a variety of small Abl kinase inhibitors were synthesized. STI571 (imatinib mesylate) was produced by modification of 2-phenylaminopyrimidine, a core structure of protein kinase C inhibitor, to improve selectivity, stability, solubility, and bioavailability. STI571 competitively binds to the ATP binding site of Bcr-Abl kinase and inhibits Abl tyrosine kinase activity. STI571 showed significant efficacy in the clinical study with CML patients at all stages: chronic phase, accelerated phase, and blast crisis. More than 90% of the patients showed good hematologic response to STI571. STI571 is also a potent inhibitor of a receptor-type c-Kit tyrosine kinase. Therefore, STI571 was examined for therapeutic efficacy against malignant Gastro-Intestinal Stromal Tumors (GIST), which are mainly caused by aberrant expression of a mutated c-Kit that is constitutively active without binding of a ligand, stem cell factor (SCF). More than a half of the metastatic GIST patients enrolled in the clinical study responded to STI571. Thus, STI571 is now used as a therapeutic drug for both CML and GIST in more than 80 countries worldwide. Certain point mutations in the ATP binding site were found to be a cause of resistance to STI571 in both Bcr-Abl and c-Kit kinases. Therefore, it would be better to make a precise therapeutic strategy with STI571 based on the gene analysis data. It is also expected that it will be possible to design an inhibitor to overcome such resistance by using the structural information on the mutants.
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PMID:Tyrosine kinase inhibitor as a therapeutic drug for chronic myelogenous leukemia and gastrointestinal stromal tumor. 1463 2

The new knowledge in molecular biology and pathophysiology of chronic myeloid leukemia enabled the development of imatinib mesylate (Glivec, formerly STI571). Imatinib potently inhibits several protein tyrosine kinases, including BCR-ABL, c-Kit, and PDGF receptor. Imatinib blocks the phosphorylation of downstream target proteins and interrupts the malignant transformation leading to the development of CML. Phase I and II studies demonstrated that imatinib is highly effective and well tolerated in all phase of CML. We got our experience with imatinib on more than two-year monitoring 34 patients within the Expanded Access Study CST1571 0113. Imatinib 400 mg/d was administered orally to 10 women and 24 men in median age of 53 years (22-70) who were hematologically (n = 9) or cytogenetically (n = 13) resistant, cytogenetically refractory (n = 3) or intolerant (n = 9) to interferon alpha. The median follow-up time was 97.5 weeks (23-115), the median time from CML diagnosis to the start of the study was 32.3 months (6-140.5). Complete hematologic response was achieved in 33 of 34 (97%) pts, total major cytogenetic response (complete plus major) in 21 of 33 (63%) pts. Cytogenetic relapse was observed in 2 of 33 pts (6%), cytogenetic progression in 4 (12%) pts. Non-hematologic toxicity was mild (grade 1 or 2) and no patient was excluded from the study due to it. Hematological toxicity grade 3 limited dose of imatinib in 26% of patients and probably caused lower rate of cytogenetic responses in heavy pretreated patients. Both quantitative RT-PCR methods (competitive RT-PCR and real-time RT-PCR Light-Cycler) were found useful to monitor patients with CML on imatinib therapy. Our results confirmed high efficacy and safety of imatinib in late-chronic phase CML patients failing prior interferon therapy. The lower incidence of hematological toxicity and higher rate of cytogenetic responses in patients treated with imatinib in early-chronic phase CML justify according to our opinion the recommendation to administer imatinib early after the diagnosis of CML in patients who are not indicated for allogeneic transplantation.
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PMID:[Imatinib mesylate (Glivec) in treatment of chronic phase chronic myeloid leukemia]. 1501 23

Imatinib mesylate is a new drug that can inhibit the tyrosine kinase activity of Bcr-Abl, the receptors for platelet-derived growth factor receptor(PDGF) and stem cell factor, or c-kit. Chronic myeloid leukemia (CML) is distinguished by the presence of a reciprocal translocation between chromosomes 9 and 22 that results in a shortened chromosome 22, termed the Philadelphia(Ph) chromosome. As a result of the translocation, a fusion gene called the Bcr-Abl gene is created from two normal cellular genes, encoding a chimeric Bcr-Abl protein with a deregulated tyrosine kinase activity. The expression of Bcr-Abl tyrosine kinase has been shown to be necessary and sufficient for the transformed phenotype of CML cells. Imatinib can block the kinase activity of Bcr-Abl, thus inhibiting the proliferation of Ph-positive progenitors, and has shown activity against all phases of CML, though responses are most substantial and durable in patients in the chronic phase. An international phase III study which compared the efficacy of imatinib with that of interferon alpha combined with low-dose cytarabine in newly diagnosed chronic-phase CML showed the rate of major cytogenetic response at 24 months was 90%, including 82% of complete cytogenetic response. These results indicated that imatinib was superior to interferon-containing treatment as a first-line therapy. More than 10,000 patients worldwide, including those in Japan, have been treated with imatinib in clinical trials, and a lot of information has been accumulated on the use of this drug. The aim of this article is to review the use of this drug and the practical management of patients with chronic myeloid leukemia.
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PMID:[Molecular targeted treatment--new treatment strategy for patients with chronic myeloid leukemia]. 1502 17

Several mechanisms of development of hepatocellular carcinoma (HCC) in patients with liver cirrhosis have been discussed. One hypothesis suggests that the somatic stem cells of the liver, the so-called oval cells, may undergo malignant transformation. Oval cells are derived from the biliary cells of the canal of Hering and are characterized by c-kit-positivity, the transmembrane receptor of stem cell factor. Constitutively activated tyrosine kinases have been identified as major pathogenetic mechanisms in the development of malignant diseases like gastrointestinal stromal tumors (c-kit) and chronic myelogenous leukemia (bcr-abl). The prognosis of these diseases improved enormously since the drug imatinib, a tyrosine kinase inhibitor of c-kit and bcr-abl, was introduced. Here we report the successful cure of a patient with liver cancer by this tyrosine kinase inhibitor.
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PMID:Successful treatment of hepatocellular carcinoma with the tyrosine kinase inhibitor imatinib in a patient with liver cirrhosis. 1505 46

c-Kit receptor (CD117) is expressed by erythroid, megakaryocytic, and myeloid precursors and mature mast cells and has been reported to be expressed in CD30+ lymphomas such as Hodgkin's disease and anaplastic large-cell lymphoma. Imatinib mesylate, a well-established inhibitor of bcr-abl tyrosine kinase, and currently used for the treatment of patients with chronic myeloid leukemia, also inhibits c-kit receptor kinase activity. In view of the possible use of imatinib as experimental therapy for patients with c-kit-positive tumors, we assessed c-kit expression in CD30+ cell lines and lymphomas. The cell lines were assessed using multiple methods (RT-PCR, flow cytometry, and Western blot). c-Kit expression was also immunohistochemically assessed in 168 CD30+ lymphomas including 87 classical Hodgkin's disease, 63 anaplastic large-cell lymphoma, and 15 cutaneous anaplastic large-cell lymphoma. We also studied 18 cases of lymphomatoid papulosis, a CD30+ lesion closely related to cutaneous anaplastic large-cell lymphoma. Neither c-kit mRNA nor protein was detected in any of the cell lines assessed. Furthermore, treatment with imatinib did not inhibit proliferation of cell lines in vitro. Using immunohistochemistry, only one of 183 (0.5%) lesions was positive for c-kit, the positive case being an ALK-negative anaplastic large-cell lymphoma. Our data demonstrate that expression of c-kit receptor is exceedingly rare among CD30+ lymphomas and lymphomatoid papulosis, suggesting that c-kit receptor is unlikely to be an appropriate target for therapeutic options such as imatinib in patients with these tumors.
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PMID:Lack of c-kit (CD117) expression in CD30+ lymphomas and lymphomatoid papulosis. 1510 13

The myeloproliferative disorders (MPDs) are chronic malignant conditions originating from the clonal expansion of a multipotential hematopoietic stem cell. These diseases include polycythemia vera (PV), essential thrombocythenia, atypical chronic myeloid leukemia, idiopathic hypereosinophilic syndrome (HES), agnogenic myeloid metaplasia with myelofibrosis, and others. Receptor tyrosine kinases-the platelet-derived growth factor receptors (PDGFRs) and c-Kit-and their respective ligands have been implicated in the pathogenesis of MPDs. For example, a constitutively activated PDGFR fusion tyrosine kinase (FIP1L1-PDGFRA) was identified in some patients with HES, a disease characterized by sustained overproduction of eosinophils that has been classified by the World Health Organization as a chronic subtype of the MPDs. Imatinib is a selective inhibitor of PDGFRs, c-Kit, Abl and Arg protein-tyrosine kinases, as well as Bcr-Abl, the oncogenic tyrosine kinase that causes chronic myeloid leukemia. The efficacy of imatinib in treating HES, systemic mast cell disease, chronic myelomonocytic leukemia associated with PDGFRbeta fusion genes, and (to a lesser extent) PV and idiopathic myelofibrosis was reviewed from institutional experience and a review of the literature. In 3 studies that involved 11 patients with PV, 10 patients had reductions in phlebotomy with imatinib. Eight studies of 42 patients with HES indicated that 70% achieved complete hematologic remissions with imatinib. Four studies of 6 patients with MPD indicated responses with imatinib in 5 patients. Insight into the molecular pathogenesis of MPDs will improve the definitions of different disease categories and suggests that signal transduction inhibition is likely to be an increasingly important treatment option in the future.
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PMID:Beyond chronic myelogenous leukemia: potential role for imatinib in Philadelphia-negative myeloproliferative disorders. 1513 47

Myeloid leukaemias are frequently associated with translocations and mutations of tyrosine kinase genes. The products of these oncogenes, including BCR-ABL, TEL-PDGFR, Flt3 and c-Kit, have elevated tyrosine kinase activity and transform haematopoietic cells, mainly by augmentation of proliferation and enhanced viability. Activated ABL kinases are associated with chronic myeloid leukaemia. Mutations in platelet-derived growth factor receptor beta are associated with chronic myelomonocytic leukaemia. Flt3 or c-Kit cooperate with other types of oncogenes to create fully transformed acute leukaemias. Elevated activity of these tyrosine kinases is crucial for transformation, thus making the kinase domain an ideal target for therapeutic intervention. Tyrosine kinase inhibitors for various kinases are currently being evaluated in clinical trials and are potentially useful therapeutic agents in myeloid leukaemias. Here, the authors review the signalling activities, mechanism of transformation and therapeutic targeting of several tyrosine kinase oncogenes important in myeloid leukaemias.
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PMID:Targeting mutated tyrosine kinases in the therapy of myeloid leukaemias. 1516 29


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