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)

Imatinib mesylate, an orally administered 2-phenylaminopyrimidine derivative that inhibits BCR/ABL tyrosine kinase activity, has shown great promise in the treatment of chronic myelogenous leukemia (CML). This small molecule, tyrosine kinase inhibitor, has also been shown to be effective against metastatic gastrointestinal stromal tumors (GISTs) expressing the stem cell factor (SCF) receptor kit. However, the threat of resistance in patients has prompted investigators to uncover the mechanisms whereby malignant cells develop resistance to imatinib, and has also led to the establishment of strategies designed to over-ride imatinib resistance. Here, we provide a comprehensive overview of the effectiveness of imatinib in the treatment of chronic, accelerated and blast crisis-phase CML, Philadelphia chromosome-positive (Ph+) acute lymphoid leukemia (ALL) and metastatic GIST. Established mechanisms of resistance to imatinib are discussed, as are novel therapeutic approaches to improving drug responsiveness by reversing development of imatinib resistance in patients.
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PMID:Resistance to imatinib (Glivec): update on clinical mechanisms. 1464 93

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

Imatinib mesylate is a small molecule drug that in vitro inhibits the Abelson (Abl), Arg (abl-related gene), stem cell factor receptor (Kit), and platelet-derived growth factor receptor A and B (PDGFRA and PDGFRB) tyrosine kinases. The drug has acquired therapeutic relevance because of similar inhibitory activity against certain activating mutations of these molecular targets. The archetypical disease in this regard is chronic myeloid leukemia, where abl is constitutively activated by fusion with the bcr gene (bcr/abl). Similarly, the drug has now been shown to display equally impressive therapeutic activity in eosinophilia-associated chronic myeloproliferative disorders that are characterized by activating mutations of either the PDGFRB or the PDGFRA gene. The former usually results from translocations involving chromosome 5q31-33, and the latter usually results from an interstitial deletion involving chromosome 4q12 (FIP1L1-PDGFRA). In contrast, imatinib is ineffective, in vitro and in vivo, against the mastocytosis-associated c-kit D816V mutation. However, wild-type and other c-kit mutations might be vulnerable to the drug, as has been the case in gastrointestinal stomal cell tumors. Imatinib is considered investigational for the treatment of hematologic malignancies without a defined molecular drug target, such as polycythemia vera, myelofibrosis with myeloid metaplasia, and acute myeloid leukemia.
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PMID:Imatinib targets other than bcr/abl and their clinical relevance in myeloid disorders. 1516 33

Imatinib mesylate (Gleevec/Glivec, Novartis, Basel, Switzerland), formerly called STI571, is a specific and potent inhibitor of the BCR-ABL tyrosine kinase, the molecular hallmark of chronic myeloid leukaemia. Several clinical trials have demonstrated the efficacy of imatinib in different phases of this disease. On the other hand, imatinib is also active against other tyrosine kinases, such as ABL, the stem cell factor receptor (c-kit) and the platelet-derived growth factor receptor, whose inhibition might have potential implications for the treatment of several malignancies. In this regard, imatinib has already shown a remarkable activity in patients with hypereosinophilic syndrome and gastrointestinal stromal tumours. Imatinib is an example of how a better understanding of the pathogenetic mechanisms of a neoplastic disease can lead to the development of a molecular-targeted therapy.
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PMID:Imatinib mesylate (Gleevec/Glivec) a molecular-targeted therapy for chronic myeloid leukaemia and other malignancies. 1520 9

The proto-oncogene c-kit is a receptor tyrosine kinase recognized to initiate essential signal transduction pathways that transmit biological signals for cellular proliferation, differentiation, and metastasis. Aberrant expression or mutation of c-kit has been shown to be involved in the pathogenesis of many cancers. Studies using imatinib mesylate (STI 571, Gleevec, Novartis, East Hannover, NJ, USA), an inhibitor of the tyrosine kinases brc-abl, c-kit, and PDGFR, have shown significant response in patients with chronic myelogenous leukemia and gastrointestinal stromal tumor. With the aim of identifying additional groups of tumors that may use the stem cell factor/c-kit pathway and, secondarily, may be responsive to imatinib mesylate treatment, we looked at the expression of c-kit in medulloblastoma. Medulloblastoma, a highly invasive primitive neuroectodermal tumor of the cerebellum, is the most common, malignant central nervous system tumor of childhood. Histologic features of medulloblastoma have failed to provide an accurate prediction of the clinical-biological behavior of these tumors. Characterizing the genetic events that play a role in the biology of these tumors may allow for molecular sub-typing and could lead to the development of novel therapeutic strategies. This study evaluated c-kit expression and mutational status in 10 medulloblastoma tumor samples. All 10 medulloblastoma tumors expressed c-kit by reverse transcriptase-polymerase chain reaction and 9 by immunohistochemical analysis. All tumor samples were screened for mutations in exons 9, 11, and 13 of the c-kit gene by direct sequencing. No sequence abnormalities were detected in these exons. These experiments lead us to the conclusion that c-kit activation in medulloblastoma is independent of mutation.
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PMID:C-kit expression and mutational analysis in medulloblastoma. 1554 73

Imatinib is a tyrosine kinase inhibitor that has been reported to specifically inhibit the growth of bcr-abl expressing chronic myeloid leukaemia progenitors. This drug functions by blocking the ATP-binding site of the kinase domain of bcr-abl, and has also been found to inhibit the c-abl, platelet-derived growth factor receptor, ARG and stem cell factor receptor tyrosine kinases. Reports have recently emerged demonstrating that imatinib also inhibits the growth of non-malignant haemopoietic cells. Here, we demonstrate that concentrations of imatinib within the therapeutic dose range inhibit the function of cultured monocytes (CM) from normal donors. A decrease in the response of CM to LPS was observed morphologically and functionally, with CM grown in the presence of imatinib showing decreased pseudopodia formation and inhibition of IL-6 and TNF-alpha production following LPS stimulation. Imatinib also reduced the ability of M-CSF and GM-CSF stimulated CM to phagocytose zymosan particles, with uptake of non-opsonized zymosan by M-CSF stimulated CM (M-CM) being most affected. M-CM that had been cultured in the presence of imatinib were also impaired in their ability to stimulate responder cells in a mixed lymphocyte reaction. These results demonstrate that human monocytes cultured in the presence of imatinib are functionally impaired, and suggest that imatinib displays inhibitory activity against other kinase(s) that play a role in monocyte/macrophage development.
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PMID:Imatinib inhibits the functional capacity of cultured human monocytes. 1566 Oct 41

Imatinib is a selective protein tyrosine kinase inhibitor currently used in the treatment of chronic myeloid leukaemia (CML). It specifically suppresses the growth of bcr-abl expressing CML progenitor cells by blocking the ATP-binding site of the kinase domain of bcr-abl. Imatinib also inhibits the c-abl, platelet derived growth factor receptor (PDGFR), abl-related gene and stem cell factor receptor, c-kit, protein tyrosine kinases. It is through inhibition of c-kit that imatinib is also used clinically in the treatment of gastrointestinal stromal tumours. We have recently demonstrated that imatinib also specifically targets the macrophage colony stimulating factor receptor, c-fms, at therapeutic concentrations. Although this finding has important implications with regard to potential side effects in patients currently receiving imatinib therapy, these results suggest that imatinib may also be useful in the treatment of diseases where c-fms is implicated. This includes breast and ovarian cancer and inflammatory conditions such as rheumatoid arthritis. We also speculate that imatinib may be used in diseases where bone destruction occurs due to excessive osteoclast activity, such as in the haematologic malignancy, multiple myeloma.
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PMID:Inhibition of c-fms by imatinib: expanding the spectrum of treatment. 1591 50

Signaling by stem cell factor and Kit, its receptor, play important roles in gametogenesis, hematopoiesis, mast cell development and function, and melanogenesis. Moreover, human and mouse embryonic stem cells express Kit transcripts. Stem cell factor exists as both a soluble and a membrane-bound glycoprotein while Kit is a glycoprotein receptor protein-tyrosine kinase. The complete absence of stem cell factor or Kit is lethal. Gain-of-function mutations of Kit are associated with several human neoplasms including acute myelogenous leukemia, gastrointestinal stromal tumors, mastocytomas, and nasal T-cell lymphomas. Binding of stem cell factor to Kit results in receptor dimerization and activation of protein kinase activity. The activated receptor becomes autophosphorylated at tyrosine residues that serve as docking sites for signal transduction molecules containing SH2 domains. Kit activates Akt, Src family kinases, phosphatidylinositol 3-kinase, phospholipase Cgamma, and Ras/mitogen-activated protein kinases. Kit exists in active and inactive conformations as determined by X-ray crystallography. Kit consists of an extracellular domain, a transmembrane segment, a juxtamembrane domain, and a protein kinase domain that contains an insert of about 80 amino acid residues. The juxtamembrane domain inhibits enzyme activity in cis by maintaining the control alphaC-helix and the activation loop in their inactive conformations. The juxtamembrane domain also inhibits receptor dimerization. STI-571, a clinically effective targeted protein-tyrosine kinase inhibitor, binds to an inactive conformation of Kit. The majority of human gastrointestinal stromal tumors have Kit gain-of-function mutations in the juxtamembrane domain, and most people with these tumors respond to STI-571. STI-571 binds to Kit and Bcr-Abl (the oncoprotein of chronic myelogenous leukemia) at their ATP-binding sites.
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PMID:Structure and regulation of Kit protein-tyrosine kinase--the stem cell factor receptor. 1622 10

Imatinib-refractory chronic myelogenous leukemia (CML) patients can experience long-term disease-free survival with myeloablative therapy and allogeneic hematopoietic cell transplantation; however, associated complications carry a significant risk of mortality. Transplantation of autologous hematopoietic cells has a reduced risk of complications, but residual tumor cells in the autograft may contribute to relapse. Development of methods for purging tumor cells that do not compromise the engraftment potential of the normal hematopoietic cells in the autograft has been a long-standing goal. Since primitive CML cells differentiate more rapidly in vitro than their normal counterparts and are also preferentially killed by mafosfamide and imatinib, we examined the purging effectiveness on CD34(+) CML cells using a strategy that combines a brief exposure to imatinib (0.5-1.0 microM for 72 h) and then mafosfamide (30-90 microg/ml for 30 min) followed by 2 weeks in culture with cytokines (100 ng/ml each of stem cell factor, granulocyte colony-stimulating factor and thrombopoietin). Treatment with 1.0 microM imatinib, 60 microg/ml mafosfamide and 14 days of culture with cytokines eliminated BCR-ABL(+) cells from chronic phase CML patient aphereses, while preserving normal progenitors. This novel purging strategy may offer a new approach to improving the effectiveness of autologous transplantation in imatinib-refractory CML patients.
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PMID:A novel triple purge strategy for eliminating chronic myelogenous leukemia (CML) cells from autografts. 1643 11


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