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)

Previous studies have shown that K562 chronic myelogenous leukemia cells are resistant to induction of apoptosis by a variety of agents, including the topoisomerase II (topo II) poison etoposide, when examined 4 to 24 hours after treatment with an initiating stimulus. In the present study, the responses of K562 cells and apoptosis-proficient HL-60 acute myelomonocytic leukemia cells to etoposide were compared, with particular emphasis on determining the long-term fate of the cells. When cells were treated with varying concentrations of etoposide for 1 hour and subsequently plated in soft agar, the two cell lines displayed similar sensitivities, with a 90% reduction in colony formation at 5 to 10 mu mol/L etoposide. After treatment with 17 mu mol/L etoposide for 1 hour, cleavage of the caspase substrate poly(ADP-ribose) polymerase (PARP), DNA fragmentation, and apoptotic morphological changes were evident in HL-60 cells in less than 6 hours. After the same treatment, K562 cells arrested in G2 phase of the cell cycle but otherwise appeared normal for 3 to 4 days before developing similar apoptotic changes. When the etoposide dose was increased to 68 mu mol/L, apoptotic changes were evident in HL-60 cells after 2 to 3 hours, whereas the same changes were observed in K562 cells after 24 to 48 hours. This delay in the development of apoptotic changes in K562 cells was accompanied by delayed release of cytochrome c to the cytosol and delayed appearance of peptidase activity that cleaved the fluorogenic substrates Asp-Glu-Val-Asp-aminotrifluoromethylcoumarin (DEVD-AFC) and Val-Glu-Ile-Asp-aminomethylcoumarin (VEID-AMC) as well as an altered spectrum of active caspases that were affinity labeled with N-(Nalpha-benzyloxycarbonylglutamyl-Nepsilon-biotin yllysyl) aspartic acid [(2,6-dimethylbenzoyl)oxy]methyl ketone [z-EK(bio)D-aomk]. On the other hand, the activation of caspase-3 under cell-free conditions occurred with indistinguishable kinetics in cytosol prepared from the two cell lines. Collectively, these results suggest that a delay in the signaling cascade upstream of cytochrome c release and caspase activation leads to a long latent period before the active phase of apoptosis is initiated in etoposide-treated K562 cells. Once the active phase of apoptosis is initiated, the spectrum and subcellular distribution of active caspase species differ between HL-60 and K562 cells, but a similar proportion of cells are ultimately killed in both cell lines.
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PMID:Comparison of caspase activation and subcellular localization in HL-60 and K562 cells undergoing etoposide-induced apoptosis. 937 39

Clinical studies with the Abl tyrosine kinase inhibitor STI-571 in chronic myeloid leukemia demonstrate that many patients with advanced stage disease respond initially but then relapse. Through biochemical and molecular analysis of clinical material, we find that drug resistance is associated with the reactivation of BCR-ABL signal transduction in all cases examined. In six of nine patients, resistance was associated with a single amino acid substitution in a threonine residue of the Abl kinase domain known to form a critical hydrogen bond with the drug. This substitution of threonine with isoleucine was sufficient to confer STI-571 resistance in a reconstitution experiment. In three patients, resistance was associated with progressive BCR-ABL gene amplification. These studies provide evidence that genetically complex cancers retain dependence on an initial oncogenic event and suggest a strategy for identifying inhibitors of STI-571 resistance.
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PMID:Clinical resistance to STI-571 cancer therapy caused by BCR-ABL gene mutation or amplification. 1156 95

STI571, a selective inhibitor of Bcr-Abl, has been a successful therapeutic agent in clinical trials for chronic myelogenous leukemia. Chronic phase chronic myelogenous leukemia patients treated with STI571 have durable responses; however, most responding blast phase patients relapse despite continued therapy. Co-crystallization studies of Abl kinase and an STI571-related compound identify specific amino acid residues as critical to STI571 binding, one of which, T315, has been characterized as an acquired Thr to Ile mutation in relapsed patients. Other studies, however, suggest that mutations other than these predicted contact points are capable of conferring STI571 resistance in relapsed patients. Using a variety of models of STI571 binding to the Abl kinase, we have performed an extensive mutational analysis of sites that might alter the sensitivity of the Abl kinase to STI571. Although mutation of many of the predicted contact points between Abl and STI571 result in a kinase-inactive protein, additional mutations that render the Abl kinase less sensitive to STI571 demonstrate a broad range of possibilities for clinical resistance that are now becoming evident.
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PMID:Analysis of the structural basis of specificity of inhibition of the Abl kinase by STI571. 1207 14

The Abl tyrosine kinase inhibitor STI-571 is effective therapy for stable phase chronic myeloid leukemia (CML) patients, but the majority of CML blast-crisis patients that respond to STI-571 relapse because of reactivation of Bcr-Abl signaling. Mutations of Thr-315 in the Abl kinase domain to Ile (T315I) were previously described in STI-571-resistant patients and likely cause resistance from steric interference with drug binding. Here we identify mutations of Tyr-253 in the nucleotide-binding (P) loop of the Abl kinase domain to Phe or His in patients with advanced CML and acquired STI-571 resistance. Bcr-Abl Y253F demonstrated intermediate resistance to STI-571 in vitro and in vivo when compared with Bcr-Abl T315I. The response of Abl proteins to STI-571 was influenced by the regulatory state of the kinase and by tyrosine phosphorylation. The sensitivity of purified c-Abl to STI-571 was increased by a dysregulating mutation (P112L) in the Src homology 3 domain of Abl but decreased by phosphorylation at the regulatory Tyr-393. In contrast, the Y253F mutation dysregulated c-Abl and conferred intrinsic but not absolute resistance to STI-571 that was independent of Tyr-393 phosphorylation. The Abl P-loop is a second target for mutations that confer resistance to STI-571 in advanced CML, and the Y253F mutation may impair the induced-fit interaction of STI-571 with the Abl catalytic domain rather than sterically blocking binding of the drug. Because clinical resistance induced by the Y253F mutation might be overcome by dose escalation of STI-571, molecular genotyping of STI-571-resistant patients may provide information useful for rational therapeutic management.
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PMID:Clinical resistance to the kinase inhibitor STI-571 in chronic myeloid leukemia by mutation of Tyr-253 in the Abl kinase domain P-loop. 1214 56

In an attempt to identify novel mHas that induce GVL effect on chronic myeloid leukemia (CML), we analyzed peripheral blood T cells of 4 CML patients who relapsed after allogeneic stem cell transplantation and received donor leukocyte infusion (DLI), for the presence of antigen-specific T-cell proliferation. When peripheral blood lymphocyte collected from patients every 2-4 weeks after DLI were subjected to complementarity determining region (CDR) 3 size distribution analysis of T-cell receptor beta chain, clonal proliferation of a limited number of CD4+ T cells was detected in all patients 2-4 months after DLI in association with the occurrence of GVL effect. To identify an epitope of the T-cell clone that probably mediates GVL effect, we determined nucleotide sequence of CDR3 of the T cells and screened the database for the presence of T cells with a CDR3 sequence similar to that of the GVL-mediating T cells. In one of 4 patients who showed clonal proliferation of a BV16+ T cell, a CDR3 motif QDR was shared by a T-cell clone that recognized an 85-99 peptide of myelin basic protein presented by HLA-DRB1*1501. When the I domain of CD49b, a candidate peptides that could bind to this CDR3 motif in the context of DRB1*1501, was studied, codon 256 in the I domain of the recipient was ATT (Ile) while that of the donor was GTT (Val). The BV16+ T cells showed proliferative response to DRB1*1501 L-cell transfectant pulsed with the recipient type CD49b. Thus, identification of a clonotype of T cells that mediate GVL effect in patients receiving DLI and a search for T-cell clones with a similar clonotype to the GVL-mediating T cells followed by screening of polymorphic peptides that could stimulate the T cells appears to be useful in identifying novel mHas serving a target antigens of GVL effect.
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PMID:Identification of novel minor histocompatibility antigens responsible for graft-versus-leukemia (GVL) effect on chronic myeloid leukemia: usefulness of determining the clonotype of T cells associated with GVL effect after donor leukocyte infusion. 1243 Aug 63

Small molecule inhibitors of protein tyrosine kinases such as STI571 represent a major new class of therapeutics for target-selective treatment of human cancer. Clinical resistance formation to the BCR-ABL inhibitor STI571 has been observed in patients with advanced chronic myeloid leukemia and was frequently caused by a C to T single nucleotide change in the Abl kinase domain, which substituted Thr-315 with isoleucine and rendered BCR-ABL resistant to STI571 inhibition. The corresponding mutation in the epidermal growth factor receptor (EGFR) tyrosine kinase replaced Thr-766 of the EGFR by methionine and dramatically reduced the sensitivity of EGFR to inhibition by selective 4-anilinoquinazoline inhibitors such as PD153035. Inhibitor-resistant EGFR exhibited the same signaling capacity as wild-type receptor in vivo and provides a useful tool for analyzing EGFR-mediated signal transduction. Our data identify Thr-766 of the EGFR as a structural determinant that bears the potential to become a relevant feature in resistance formation during cancer therapy with EGFR-specific 4-anilinoquinazoline inhibitors.
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PMID:Mutation of threonine 766 in the epidermal growth factor receptor reveals a hotspot for resistance formation against selective tyrosine kinase inhibitors. 1259 13

The success of targeting kinases in cancer with small molecule inhibitors has been tempered by the emergence of drug-resistant kinase domain mutations. In patients with chronic myeloid leukemia treated with ABL inhibitors, BCR-ABL kinase domain mutations are the principal mechanism of relapse. Certain mutations are occasionally detected before treatment, suggesting increased fitness relative to wild-type p210 BCR-ABL. We evaluated the oncogenicity of eight kinase inhibitor-resistant BCR-ABL mutants and found a spectrum of potencies greater or less than p210. Although most fitness alterations correlate with changes in kinase activity, this is not the case with the T315I BCR-ABL mutation that confers clinical resistance to all currently approved ABL kinase inhibitors. Through global phosphoproteome analysis, we identified a unique phosphosubstrate signature associated with each drug-resistant allele, including a shift in phosphorylation of two tyrosines (Tyr253 and Tyr257) in the ATP binding loop (P-loop) of BCR-ABL when Thr315 is Ile or Ala. Mutational analysis of these tyrosines in the context of Thr315 mutations demonstrates that the identity of the gatekeeper residue impacts oncogenicity by altered P-loop phosphorylation. Therefore, mutations that confer clinical resistance to kinase inhibitors can substantially alter kinase function and confer novel biological properties that may impact disease progression.
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PMID:Phosphorylation of the ATP-binding loop directs oncogenicity of drug-resistant BCR-ABL mutants. 1716 33

Varicella zoster virus (VZV) infection is uncommon in patients with gastrointestinal stromal tumour (GIST) and who have not been exposed to extensive radiotherapy and/or high-dose chemotherapy. We report a 56-year-old Nigerian man with GIST who developed VZV infection while on imatinib mesylate therapy. From August 2003 to November 2005, 64 patients (GIST/CML = 6/58) were enrolled into an ongoing Glivec (imatinib mesylate) international patient-assistance programme therapy for Philadelphia/bcr-abl-positive chronic myeloid leukaemia (CML) and CD117-positive GIST patients at Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Nigeria. The patient developed herpes zoster (HZ) infection 23 months into therapy with Glivec. With his absolute lymphocyte count at 2,774 cells per microlitre and CD4 count at 950 cells per microlitre, no obvious immunological defect was observed. Prompt resolution of symptoms without sequelae was achieved by treating with acyclovir, analgesic and dressing of lesions with desiccant. To our knowledge, this is the first reported case of HZ infection in a patient with GIST on Glivec therapy, and the response is similar to that of CML patients who developed VZV while on similar therapy.
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PMID:Herpes zoster complicating imatinib mesylate for gastrointestinal stromal tumour. 1724 98

The lessons learned from the remarkably successful use of the first-generation tyrosine kinase inhibitor (TKI) imatinib in patients with chronic myeloid leukemia resulted in a major paradigm shift in the treatment of many human cancers, and now further lessons are being learned from our enhanced understanding of the molecular mechanisms of resistance to imatinib and second-generation TKIs, particularly dasatinib and nilotinib. Although diverse mechanisms seem to be involved, the principal cause appears to be the emergence of point mutations in the Abl kinase domain that affect drug affinity and some of which impair the efficacy with which the drugs bind. Currently, > 50 different mutations have been identified, and the extent to which they confer resistance varies considerably. One of the more common mutations results from the substitution of isoleucine for threonine at Abl amino acid position 351, known as the T315I mutation. It appears that the precise position of the substitution within the kinase domain dictates the degree of resistance to TKIs, and patients with the T315I mutation develop almost complete resistance to imatinib, dasatinib, and nilotinib. Herein, we discuss the emerging strategies for circumventing resistance associated with the Bcr-Abl T315I mutation.
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PMID:Emerging strategies for the treatment of mutant Bcr-Abl T315I myeloid leukemia. 1738 17

Dasatinib is a small-molecule kinase inhibitor used for the treatment of imatinib-resistant chronic myelogenous leukemia (CML). We have analyzed the kinases targeted by dasatinib by using an unbiased chemical proteomics approach to detect binding proteins directly from lysates of CML cells. Besides Abl and Src kinases, we have identified the Tec kinases Btk and Tec, but not Itk, as major binders of dasatinib. The kinase activity of Btk and Tec, but not of Itk, was inhibited by nanomolar concentrations of dasatinib in vitro and in cultured cells. We identified the gatekeeper residue as the critical determinant of dasatinib susceptibility. Mutation of Thr-474 in Btk to Ile and Thr-442 in Tec to Ile conferred resistance to dasatinib, whereas mutation of the corresponding residue in Itk (Phe-435) to Thr sensitized the otherwise insensitive Itk to dasatinib. The configuration of this residue may be a predictor for dasatinib sensitivity across the kinome. Analysis of mast cells derived from Btk-deficient mice suggested that inhibition of Btk by dasatinib may be responsible for the observed reduction in histamine release upon dasatinib treatment. Furthermore, dasatinib inhibited histamine release in primary human basophils and secretion of proinflammatory cytokines in immune cells. The observed inhibition of Tec kinases by dasatinib predicts immunosuppressive (side) effects of this drug and may offer therapeutic opportunities for inflammatory and immunological disorders.
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PMID:The Btk tyrosine kinase is a major target of the Bcr-Abl inhibitor dasatinib. 1768 99


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