Wu J, Meng F, Lu H, Kong L, Bornmann W, Peng Z et al.. Lyn regulates BCR-ABL and Gab2 tyrosine phosphorylation and c-Cbl protein stability in imatinib resistant chronic myelogenous leukemia cells. Blood 7: 3821-3829

Department of Experimental Therapeutics, The University of Texas, M. D. Anderson Cancer Center, Houston, USA.
Blood (Impact Factor: 10.45). 05/2008; 111(7):3821-9. DOI: 10.1182/blood-2007-08-109330
Source: PubMed


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.

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    • "Both imatinib and low-dose dasatinib were found to reduce the phosphorylation (activity) of SFKs in BCR-ABL-positive cells. This effect is probably indirect, resulting from the loss of SFK stimulation by BCR-ABL [30], [31], as 1 µM imatinib does not significantly reduce SFK phosphorylation in BCR-ABL-negative HEL cells (Figure 6, Figure S4) although IC50 values for isolated LYN were reported to be 0.35–2.2 µM [17], [32], [33]. "
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    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 mu M 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.
    Full-text · Article · Sep 2014 · PLoS ONE
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    • "Imatinib (Figure 1(a)), as we know, is a phenylamino pyrimidine derivative and a member of a new class of drugs collectively known as signal transduction inhibitors which interferes with cellular proliferation and induces apoptosis of BCR-ABL cells [1]; also imatinib interferes with the receptor tyrosine kinases for platelet-derived growth factor (PDGF), stem cell factor (SCF), and c-Kit and inhibits PDGF and SCF-mediated cellular activity in vitro [2, 3]. "
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    ABSTRACT: The purpose of this study was to determine the effect of apigenin on the pharmacokinetics of imatinib and N-desmethyl imatinib in rats. Healthy male SD rats were randomly divided into four groups: A group (the control group), B group (the long-term administration of 165 mg/kg apigenin for 15 days), C group (a single dose of 165 mg/kg apigenin), and D group (a single dose of 252 mg/kg apigenin). The serum concentrations of imatinib and N-desmethyl imatinib were measured by HPLC, and pharmacokinetic parameters were calculated using DAS 3.0 software. The parameters of AUC(0-t), AUC(0-∞), T max, V z /F, and CL z /F for imatinib in group B were different from those in group A (P < 0.05). Besides, MRT(0-t) and MRT(0-∞) in groups C and D differed distinctly from those in group A as well. The parameters of AUC(0-t) and C max for N-desmethyl imatinib in group C were significantly lower than those in group A (P < 0.05); however, compared with groups B and D, the magnitude of effect was modest. Those results indicated that apigenin in the short-term study inhibited the metabolism of imatinib and its metabolite N-desmethyl imatinib, while in the long-term study the metabolism could be accelerated.
    Full-text · Article · Nov 2013
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    • "Lyn kinase further regulates survival and responsiveness of CML cells to inhibition of Bcr-Abl kinase [19]. Interestingly, Lyn can also phosphorylate Tyr177 in Bcr-Abl [26], resulting in a potential feedback mechanism. The Gab2-Bcr-Abl complex is mediated by Grb2 [3] and results in activation of downstream proliferative/survival pathways, such as Ras-ERK and PI3K-Akt. "
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    ABSTRACT: Emergence of resistance to Tyrosine-Kinase Inhibitors (TKIs), such as imatinib, dasatinib and nilotinib, in Chronic Myelogenous Leukemia (CML) demands new therapeutic strategies. We and others have previously established bortezomib, a selective proteasome inhibitor, as an important potential treatment in CML. Here we show that the combined regimens of bortezomib with mitotic inhibitors, such as the microtubule-stabilizing agent Paclitaxel and the PLK1 inhibitor BI2536, efficiently kill TKIs-resistant and -sensitive Bcr-Abl-positive leukemic cells. Combined treatment activates caspases 8, 9 and 3, which correlate with caspase-induced PARP cleavage. These effects are associated with a marked increase in activation of the stress-related MAP kinases p38MAPK and JNK. Interestingly, combined treatment induces a marked decrease in the total and phosphorylated Bcr-Abl protein levels, and inhibits signaling pathways downstream of Bcr-Abl: downregulation of STAT3 and STAT5 phosphorylation and/or total levels and a decrease in phosphorylation of the Bcr-Abl-associated proteins CrkL and Lyn. Moreover, we found that other mitotic inhibitors (Vincristine and Docetaxel), in combination with bortezomib, also suppress the Bcr-Abl-induced pro-survival signals and result in caspase 3 activation. These results open novel possibilities for the treatment of Bcr-Abl-positive leukemias, especially in the imatinib, dasatinib and nilotinib-resistant CML cases.
    Full-text · Article · Oct 2013 · PLoS ONE
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