Lyn regulates BCR-ABL and Gab2 tyrosine phosphorylation and c-Cbl protein stability in imatinib-resistant chronic myelogenous leukemia cells.

Department of Experimental Therapeutics, The University of Texas, M. D. Anderson Cancer Center, Houston, USA.
Blood (Impact Factor: 9.78). 05/2008; 111(7):3821-9. DOI: 10.1182/blood-2007-08-109330
Source: PubMed

ABSTRACT Lyn kinase functions as a regulator of imatinib sensitivity in chronic myelogenous leukemia (CML) cells through an unknown mechanism. In patients who fail imatinib therapy but have no detectable BCR-ABL kinase mutation, we detected persistently activated Lyn kinase. In imatinib-resistant CML cells and patients, Lyn activation is BCR-ABL independent, it is complexed with the Gab2 and c-Cbl adapter/scaffold proteins, and it mediates persistent Gab2 and BCR-ABL tyrosine phosphorylation in the presence or absence of imatinib. Lyn silencing or inhibition is necessary to suppress Gab2 and BCR-ABL phosphorylation and to recover imatinib activity. Lyn also negatively regulates c-Cbl stability, whereas c-Cbl tyrosine phosphorylation is mediated by BCR-ABL. These results suggest that Lyn exists as a component of the BCR-ABL signaling complex and, in cells with high Lyn expression or activation, BCR-ABL kinase inhibition alone (imatinib) is not sufficient to fully disengage BCR-ABL-mediated signaling and suggests that BCR-ABL and Lyn kinase inhibition are needed to prevent or treat this form of imatinib resistance.

1 Bookmark
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cancer cells are dependent on protein kinase signalling networks to drive proliferation and to promote survival, and, accordingly, kinases continue to represent a major target class for development of anti-cancer therapeutics. Kinase inhibitors nevertheless have yielded only limited success with many different malignancies due to the inability of single agents to sustain a durable clinical response. Cancer cell kinomes are highly resilient and able to bypass targeted kinase inhibition, leading to tumour resistance. A novel platform has been developed to analyse the activity of the expressed kinome using MIBs (multiplexed inhibitor beads), which consist of Sepharose beads with covalently immobilized inhibitors that preferentially bind activated kinases. Coupling MIB capture with MS (MIB-MS) allows simultaneous determination of the activity of over 75% of the expressed kinome, facilitating high-throughput assessment of adaptive kinase responses resulting from deregulated feedback and feedforward regulatory mechanisms. The adaptive response frequently involves transcriptional up-regulation of specific kinases that allow bypass of the targeted kinase. Understanding how the kinome reprogrammes to targeted kinase inhibition will allow novel therapeutic strategies to be developed for durable clinical responses.
    Biochemical Society Transactions 08/2014; 42(4):765-9. · 3.24 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Attachment of stem leukemic cells to the bone marrow extracellular matrix increases their resistance to chemotherapy and contributes to the disease persistence. In chronic myelogenous leukemia (CML), the activity of the fusion BCR-ABL kinase affects adhesion signaling. Using real-time monitoring of microimpedance, we studied in detail the kinetics of interaction of human CML cells (JURL-MK1, MOLM-7) and of control BCR-ABL-negative leukemia cells (HEL, JURKAT) with fibronectin-coated surface. The effect of two clinically used kinase inhibitors, imatinib (a relatively specific c-ABL inhibitor) and dasatinib (dual ABL/SRC family kinase inhibitor), on cell binding to fibronectin is described. Both imatinib and low-dose (several nM) dasatinib reinforced CML cell interaction with fibronectin while no significant change was induced in BCR-ABL-negative cells. On the other hand, clinically relevant doses of dasatinib (100 nM) had almost no effect in CML cells. The efficiency of the inhibitors in blocking the activity of BCR-ABL and SRC-family kinases was assessed from the extent of phosphorylation at autophosphorylation sites. In both CML cell lines, SRC kinases were found to be transactivated by BCR-ABL. In the intracellular context, EC50 for BCR-ABL inhibition was in subnanomolar range for dasatinib and in submicromolar one for imatinib. EC50 for direct inhibition of LYN kinase was found to be about 20 nM for dasatinib and more than 10 mM for imatinib. Cells pretreated with 100 nM dasatinib were still able to bind to fibronectin and SRC kinases are thus not necessary for the formation of cell-matrix contacts. However, a minimal activity of SRC kinases might be required to mediate the increase in cell adhesivity induced by BCR-ABL inhibition. Indeed, active (autophosphorylated) LYN was found to localize in cell adhesive structures which were visualized using interference reflection microscopy. Citation: Obr A, Rö selová P, Grebeň ová D, Kuželová K (2014) Real-Time Analysis of Imatinib-and Dasatinib-Induced Effects on Chronic Myelogenous Leukemia Cell Interaction with Fibronectin. PLoS ONE 9(9): e107367. doi:10.1371/journal.pone.0107367 Copyright: ß 2014 Obr et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files. Funding: The work was supported by the Ministry of Health of the Czech Republic (Project for conceptual development of research organization No. 00023736) and by European Union (grants ERDF OPPK CZ.2.16/3.1.00/24001 and CZ.2.16/3.1.00/28007). AO acknowledges the support of the Grant Agency of Charles University (grant No. 498214). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist.
    PLoS ONE 09/2014; · 3.53 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This corrected version of the original paper includes an erratum displaying the right Figure 2 (at the end of the document).

Full-text (2 Sources)

Available from
Jun 4, 2014