FLT3-ITD-TKD dual mutants associated with AML confer resistance to FLT3 PTK inhibitors and cytotoxic agents by overexpression of Bcl-x(L)

Blood ◽  
2005 ◽  
Vol 105 (9) ◽  
pp. 3679-3685 ◽  
Author(s):  
Ksenia Bagrintseva ◽  
Stefanie Geisenhof ◽  
Ruth Kern ◽  
Sabine Eichenlaub ◽  
Carola Reindl ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Tyrosine Kinase ◽  
Molecular Mechanisms ◽  
Kinase Domain ◽  
Model Systems ◽  
Cytotoxic Agents ◽  
Tyrosine Kinase Domain ◽  
Vitro Model ◽  
G2m Phase

AbstractFLT3 (fms-like tyrosine kinase 3) is constitutively activated in about 30% of patients with acute myeloid leukemia (AML) and represents a disease-specific molecular marker. Although FLT3-LM (length mutation) and TKD (tyrosine kinase domain) mutations have been considered to be mutually exclusive, 1% to 2% of patients carry both mutations. However, the functional and clinical significance of this observation is unclear. We demonstrate that FLT3-ITD-TKD dual mutants induce drug resistance toward PTK inhibitors and cytotoxic agents in in vitro model systems. As molecular mechanisms of resistance, we found that FLT3-ITD-TKD mutants cause hyperactivation of STAT5 (signal transducer and activator of transcription-5), leading to upregulation of Bcl-x(L) and RAD51 and arrest in the G2M phase of the cell cycle. Overexpression of Bcl-x(L) was identified as the critical mediator of drug resistance and recapitulates the PTK inhibitor and daunorubicin-resistant phenotype in FLT3-ITD cells. The combination of rapamycin, a selective mTOR inhibitor, and FLT3 PTK inhibitors restored the drug sensitivity in FLT3 dual mutant–expressing cells. Our data provide the molecular basis for understanding clinical FLT3 PTK inhibitor resistance and point to therapeutical strategies to overcome drug resistance in patients with AML.

scholarly journals Lyn Physically Associates With the Erythropoietin Receptor and May Play a Role in Activation of the Stat5 Pathway

Blood ◽  
1998 ◽  
Vol 91 (10) ◽  
pp. 3734-3745 ◽  
Author(s):  
Hiroshi Chin ◽  
Ayako Arai ◽  
Hiroshi Wakao ◽  
Ryuichi Kamiyama ◽  
Nobuyuki Miyasaka ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Kinase Domain ◽  
Sh2 Domain ◽  
Erythropoietin Receptor ◽  
Tyrosine Kinase Domain ◽  
Binding Studies ◽  
In Vitro Binding ◽  
Vitro Binding

Abstract Protein tyrosine phosphorylation plays a crucial role in signaling from the receptor for erythropoietin (Epo), although the Epo receptor (EpoR) lacks the tyrosine kinase domain. We have previously shown that the Jak2 tyrosine kinase couples with the EpoR to transduce a growth signal. In the present study, we demonstrate that Lyn, a Src family tyrosine kinase, physically associates with the EpoR in Epo-dependent hematopoietic cell lines, 32D/EpoR-Wt and F36E. Coexpression experiments in COS7 cells further showed that Lyn induces tyrosine phosphorylation of the EpoR and that both LynA and LynB, alternatively spliced forms of Lyn, bind with the membrane-proximal 91-amino acid region of the EpoR cytoplasmic domain. In vitro binding studies using GST-Lyn fusion proteins further showed that the Src homology (SH)-2 domain of Lyn specifically binds with the tyrosine-phosphorylated EpoR in lysate from Epo-stimulated cells, whereas the tyrosine kinase domain of Lyn binds with the unphosphorylated EpoR. Far-Western blotting and synthetic phosphopeptide competition assays further indicated that the Lyn SH2 domain directly binds to the tyrosine-phosphorylated EpoR, most likely through its interaction with phosphorylated Y-464 or Y-479 in the carboxy-terminal region of the EpoR. In vitro binding studies also demonstrated that the Lyn SH2 domain directly binds to tyrosine-phosphorylated Jak2. In vitro reconstitution experiments in COS7 cells further showed that Lyn induces tyrosine phosphorylation of Stat5, mainly on Y-694, and activates the DNA-binding and transcription-activating abilities of Stat5. In agreement with this, Lyn enhanced the Stat5-dependent transcriptional activation when overexpressed in 32D/EpoR-Wt cells. In addition, Lyn was demonstrated to phosphorylate the EpoR and Stat5 on tyrosines in vitro. These results suggest that Lyn may play a role in activation of the Jak2/Stat5 and other signaling pathways by the EpoR.

scholarly journals Gilteritinib is a clinically active FLT3 inhibitor with broad activity against FLT3 kinase domain mutations

2020 ◽  
Vol 4 (3) ◽  
pp. 514-524 ◽  
Author(s):  
Theodore C. Tarver ◽  
Jason E. Hill ◽  
Leena Rahmat ◽  
Alexander E. Perl ◽  
Erkut Bahceci ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Kinase Inhibitor ◽  
Kinase Domain ◽  
Tyrosine Kinase Domain ◽  
Flt3 Mutations ◽  
Tki Resistance ◽  
Sequencing Studies ◽  
Moderate Resistance ◽  
Vitro Analysis

Abstract Gilteritinib is the first FMS-like tyrosine kinase 3 (FLT3) tyrosine kinase inhibitor (TKI) approved as monotherapy in acute myeloid leukemia with FLT3 internal tandem duplication and D835/I836 tyrosine kinase domain (TKD) mutations. Sequencing studies in patients have uncovered less common, noncanonical (NC) mutations in FLT3 and have implicated secondary TKD mutations in FLT3 TKI resistance. We report that gilteritinib is active against FLT3 NC and TKI resistance-causing mutations in vitro. A mutagenesis screen identified FLT3 F691L, Y693C/N, and G697S as mutations that confer moderate resistance to gilteritinib in vitro. Analysis of patients treated with gilteritinib revealed that 2/9 patients with preexisting NC FLT3 mutations responded and that secondary TKD mutations are acquired in a minority (5/31) of patients treated with gilteritinib. Four of 5 patients developed F691L mutations (all treated at <200 mg). These studies suggest that gilteritinib has broad activity against FLT3 mutations and limited vulnerability to resistance-causing FLT3 TKD mutations, particularly when used at higher doses.

BMS-354825 Is a SRC/ABL Inhibitor with High Nanomolar Activity Against the Kit D816v Mutation, Which Drives Systemic Mastocytosis and Is Imatinib-Resistant.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 797-797 ◽  
Author(s):  
Neil P. Shah ◽  
Francis Y. Lee ◽  
Charles L. Sawyers ◽  
Cem Akin
Keyword(s):  
Tyrosine Kinase ◽  
Ex Vivo ◽  
Systemic Mastocytosis ◽  
Kinase Domain ◽  
Pharmacokinetic Analysis ◽  
Tyrosine Kinase Domain ◽  
Independent Manner ◽  
Kit Mutation ◽  
Imatinib Resistant

Abstract The vast majority of systemic mastocytosis cases are associated with a somatic KIT oncoprotein point mutation which substitutes a valine for aspartic acid (D816V), resulting in KIT receptor auto-phosphorylation in a ligand-independent manner. Previous reports have demonstrated that this mutation is inherently imatinib-resistant. Although interferon-alpha has some activity against aggressive systemic mastocytosis, major responses are uncommon, and the drug is associated with significant toxicity. To date, there remains no effective therapy for systemic mastocytosis. We recently described BMS-354825, a novel orally bioavailable SRC/ABL inhibitor that has activity against multiple imatinib-resistant BCR-ABL isoforms in vitro (Shah et al, Science 305:399, 2004). BMS-354825 is presently undergoing evaluation in a phase I clinical trial of imatinib-resistant CML patients, and is showing signs of clinical efficacy. Pharmacokinetic analysis suggests that high nanomolar concentrations of the compound can be safely achieved in humans (see Sawyers et al, Talpaz et al, abstracts submitted for this meeting). To determine if this compound warrants study in other human hematologic conditions, we tested BMS-354825 for activity against human mastocytosis cell lines HMC-1560 and HMC-1560,816, carrying an activating c-kit mutation in juxtamembrane domain (codon 560) with or without a second mutation in tyrosine kinase domain (codon 816), respectively. While 1 um imatinib failed to inhibit the growth of HMC-1560,816 cells carrying the tyrosine kinase domain c-kit mutation, BMS-354825 led to an almost complete growth inhibition at the same concentration, with an IC50 of 0.1–1 uM. In addition, growth of HMC-1560 cells carrying the juxtamembrane c-kit mutation alone was more effectively inhibited by BMS-354825 as compared to imatinib (IC50 of <0.01 vs 0.01–0.1 micromolars respectively). Significantly, detection of phospho-KIT by Western blot analysis was significantly reduced in the presence of BMS-354825 at nanomolar concentrations. An ex vivo assessment of D816V-harboring mast cell sensitivity using a flow cytometric method in systemic mastocytosis bone marrow samples is ongoing. Our findings suggest that studies to evaluate BMS-354825 for the treatment of systemic mastocytosis are warranted. Additionally, the compound may harbor activity in other disease settings that contain activating KIT mutations.

Transforming and Tumorogenic Activity of JAK2 by Fusion to BCR: Molecular Mechanisms of Action of a Novel BCR-JAK2 Tyrosin-Kinase.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 4683-4683
Author(s):  
Álvaro Cuesta-Domínguez ◽  
Mara Ortega ◽  
Cristina Ormazabal ◽  
Matilde Santos-Roncero ◽  
Marta Galán-Díez ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Nude Mice ◽  
Molecular Mechanisms ◽  
Conflicts Of Interest ◽  
Fusion Gene ◽  
Lymphoblastic Leukemia ◽  
Chimeric Protein ◽  
Tyrosine Kinase Domain ◽  
Molecular Response

Abstract Abstract 4683 Chromosomal translocations in human tumors frequently produce fusion genes whose chimeric protein products play an essential role in oncogenesis. Recent reports have found a BCR-JAK2 fusion gene in cases of chronic or acute myeloid leukemia, but the protein had not been characterized. We describe a BCR-JAK2 fusion gene by fluorescence in situ hybridization and RT-PCR amplification from bone marrow at diagnosis of a patient with acute lymphoblastic leukemia. After induction therapy, real time PCR showed persistent molecular response correlating with hematological remission maintained up to present. BCR-JAK2 is a 110 KDa chimeric protein containing the BCR oligomerization domain fused to the JAK2 tyrosine-kinase domain. In vitro analysis showed that BCR-JAK2 was constitutively phosphorylated and was located to the cytoplasm. BCR-JAK2 transformed the IL-3-dependent murine hematopoietic cell line Ba/F3 into IL-3 independent growth and induced STAT5b phosphorylation and translocation into the cell nuclei. The treatment with a JAK2 inhibitor abrogated BCR-JAK2 and STAT5b phosphorylation, leading to apoptosis of transformed Ba/F3 cells. To test whether BCR-JAK2 has tumorogenic ability in vivo, we performed experiments with nude mice, in which we injected subcutaneously cells transduced with the control vector and cells expressing BCR-JAK2. Notably, we only obtained tumors in the flank injected with BCR-JAK2 expressing cells, thus confirming the tumorogenic activity of the BCR-JAK2 fusion protein. We conclude that BCR-JAK2 is a new tyrosine-kinase that induces proliferation and cell survival, which can be abrogated by JAK2 inhibitors. In vitro studies demonstrate that BCR-JAK2 displays transforming activity. Moreover, the nude mice model reveals its ability to cause tumors. Disclosures: No relevant conflicts of interest to declare.

scholarly journals A Novel Activating Mutation in the RET Tyrosine Kinase Domain Mediates Neoplastic Transformation

2006 ◽  
Vol 20 (7) ◽  
pp. 1633-1643 ◽  
Author(s):  
Aaron Cranston ◽  
Cristiana Carniti ◽  
Sam Martin ◽  
Piera Mondellini ◽  
Yvette Hooks ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Cell Line ◽  
Glial Cell ◽  
Neurotrophic Factor ◽  
Functional Characterization ◽  
Kinase Domain ◽  
Tyrosine Kinase Domain ◽  
Exogenous Substrate

Abstract We report the finding of a novel missense mutation at codon 833 in the tyrosine kinase of the RET proto-oncogene in a patient with a carcinoma of the thyroid. In vitro experiments demonstrate that the R833C mutation induces transformed foci only when present in the long 3′ splice isoform and, in keeping with a model in which the receptor has to dimerize to be completely activated, glial cell line-derived neurotrophic factor stimulation leads the RETR833C receptor to a higher level of activation. Tyrosine kinase assays show that the RETR833C long isoform has weak intrinsic kinase activity and phosphorylation of an exogenous substrate is not elevated even in the presence of glial cell line-derived neurotrophic factor. Furthermore, the R833C mutation is capable of sustaining the transformed phenotype in vivo but does not confer upon the transformed cells the ability to degrade the basement membrane in a manner analogous to metastasis. Our functional characterization of the R833C substitution suggests that, like the V804M and S891A mutations, this tyrosine kinase mutation confers a weak activating potential upon RET. This is the first report demonstrating that the introduction of an intracellular cysteine can activate RET. However, this does not occur via dimerization in a manner analogous to the extracellular cysteine mutants.

scholarly journals Comparison of tyrosine kinase domain properties for the neurotrophin receptors TrkA and TrkB

2020 ◽  
Vol 477 (20) ◽  
pp. 4053-4070
Author(s):  
Stephen C. Artim ◽  
Anatoly Kiyatkin ◽  
Mark A. Lemmon
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Kinases ◽  
Catalytic Efficiency ◽  
Kinase Domain ◽  
Tyrosine Kinase Domain ◽  
Signaling Dynamics ◽  
Cellular Context ◽  
And Function ◽  
High Degree

The tropomyosin-related kinase (Trk) family consists of three receptor tyrosine kinases (RTKs) called TrkA, TrkB, and TrkC. These RTKs are regulated by the neurotrophins, a class of secreted growth factors responsible for the development and function of neurons. The Trks share a high degree of homology and utilize overlapping signaling pathways, yet their signaling is associated with starkly different outcomes in certain cancers. For example, in neuroblastoma, TrkA expression and signaling correlates with a favorable prognosis, whereas TrkB is associated with poor prognoses. To begin to understand how activation of the different Trks can lead to such distinct cellular outcomes, we investigated differences in kinase activity and duration of autophosphorylation for the TrkA and TrkB tyrosine kinase domains (TKDs). We find that the TrkA TKD has a catalytic efficiency that is ∼2-fold higher than that of TrkB, and becomes autophosphorylated in vitro more rapidly than the TrkB TKD. Studies with mutated TKD variants suggest that a crystallographic dimer seen in many TrkA (but not TrkB) TKD crystal structures, which involves the kinase-insert domain, may contribute to this enhanced TrkA autophosphorylation. Consistent with previous studies showing that cellular context determines whether TrkB signaling is sustained (promoting differentiation) or transient (promoting proliferation), we also find that TrkB signaling can be made more transient in PC12 cells by suppressing levels of p75NTR. Our findings shed new light on potential differences between TrkA and TrkB signaling, and suggest that subtle differences in signaling dynamics can lead to substantial shifts in the cellular outcome.

Location of FLT3-ITDs within the beta1-Sheet of FLT3 Kinase Confers Resistance to Tyrosine Kinase Inhibitors (TKI) in Vitro.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 2440-2440
Author(s):  
Thomas S. Mack ◽  
Patricia Arreba-Tutusaus ◽  
Tina M Schnoeder ◽  
Florian H Heidel ◽  
Thomas Fischer
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinase ◽  
Tyrosine Kinase Inhibitors ◽  
Kinase Inhibitors ◽  
Kinase Domain ◽  
Expression Vectors ◽  
Tyrosine Kinase Domain ◽  
Hematopoietic Cell Lines ◽  
Constitutive Phosphorylation

Abstract Abstract 2440 Introduction: In AML, the recently described tyrosine kinase domain-1 (TKD1)-ITDs of FLT3 (Breitenbuecher et al., Blood 2009, Kayser-S et al., Blood 2009) are located within the beta1-sheet, nucleotide binding loop and beta2-sheet of tyrosine kinase domain 1 (TKD1), respectively. Multivariate analysis of clinical data revealed that location of FLT3-ITDs within the beta1-sheet of TKD1 is an unfavorable prognostic factor (Kayser-S et al., Blood 2009). Recently, we uncovered a novel mechanism of primary resistance to FLT3 tyrosine kinase inhibitors (TKIs) in a patient displaying an atypical localization within the beta2-sheet-ITD (A627E). Here, we characterized in-vitro sensitivity to FLT3-TKI in growth factor dependent hematopoietic cell lines expressing a representative panel of FLT3-ITDs isolated from patient material. In particular, we compared sensitivity of beta1-sheet ITDs with typical ITDs located in the juxtamembrane domain of FLT3. Methods: FLT3-ITDs isolated from patient material, were sequenced, subcloned in parallel into two expression vectors (pAL and pMSCV-Puromycin-IRES-GFP), and stably expressed in growth-factor dependent hematopoietic Ba/F3 cells and in parallel in 32D cells. Constitutive phosphorylation of FLT3-ITD receptors and of downstream signaling pathways was analyzed by Western-blotting. Transformation of Ba/F3 and 32D cells was investigated by colony formation assays and by withdrawal of IL-3. Induction of apoptosis in response to various concentrations of FLT3-kinase inhibitors midostaurin (PKC412) and quizartinib (AC220) was measured by flow-cytometry at 24h and 48h, respectively. For statistical analysis of replicates t-test was employed. Results: Biological characteristics of FLT3-ITD mutations located in two different structural domains of FLT3-kinase were characterized: (1) beta1-sheet-ITDs E611V(96nt) and Q613E(99nt) and (2) nucleotide binding loop-ITD A620V(84nt). (Our nomenclature used for description of ITDs indicates position of amino-acid where ITD is located, possible exchange of amino-acid residues at this position and nucleotide length of ITD) Hematopoietic cells (32D and Ba/F3) expressing these ITD mutations showed colony formation in methylcellulose medium, growth-factor independent proliferation upon IL-3 withdrawal and constitutive phosphorylation of FLT3 signaling. Three ‘typical’ juxtamembrane domain (JMD) ITDs were used as controls; ITD598/599(36nt), ITD598/599(66nt) and ITDK602R(21nt). As compared to these JM-ITDs, we observed significantly less apoptosis of beta1-sheet-ITDs at all concentrations of FLT3-kinase inhibitors applied. However, this difference in sensitivity gradually decreased when incubating with midostaurin or quizartinib for longer periods of time as 48h. Of note, length of FLT3-ITD mutations did not appear to influence sensitivity to TKI treatment. Conclusion: Investigating representative FLT3-ITD-mutations located within the TKD1 revealed that beta1-sheet-ITDs mediate constitutive activation of FLT3 receptors leading to transformation of hematopoietic cell lines 32D and Ba/F3. In comparison to typical JMD-ITDs, beta1-sheet-ITDs analyzed here revealed resistance to FLT3-inhibitors as midostaurin and quizartinib across two cellular reconstitution models (32D and Ba/F3) and using two different expression vectors (pAL and pMSCV). Our results indicate that differential sensitivity is rather an effect of ITD-localization within a functional domain of FLT3 and not necessarily conferred by the length of ITDs. Taken together, our data provide a rationale to prospectively analyze not only the FLT3-ITD mutation status or FLT3-ITD allelic ratio but also location of ITD-mutations in ongoing clinical trials as this may have direct impact on response to therapy (tyrosine kinase inhibitors, chemotherapy, allogeneic stem cell transplantation) in FLT3-ITD positive AML. Disclosures: Heidel: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Fischer:Novartis: Honoraria.

Modeling targeted inhibition of wild type and mutated c-MET receptor

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 14010-14010
Author(s):  
P. C. Ma ◽  
S. Jiang ◽  
R. Du ◽  
S. Dietrich ◽  
Z. Tang ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Kinase Inhibitor ◽  
Receptor Activation ◽  
Kinase Domain ◽  
Cell System ◽  
Tyrosine Kinase Domain ◽  
Wild Type ◽  
Juxtamembrane Domain ◽  
Met Receptor

14010 Background: c-MET belongs to the semaphorin superfamily of signaling proteins, containing three protein families (semaphorins, plexins, c-MET and RON) that have central roles in cell signaling. The c-MET receptor tyrosine kinase is involved in regulating cell growth/proliferation, survival, angiogenesis, cell scattering, cell motility and migration. Mutations in c-MET have been identified in various human cancers including lung cancer and papillary renal cell carcinomas. c-MET mutations occur within the extracellular seven-blade β-propeller fold sema domain (E168D, L229F, S325G, N375S), juxtamembrane domain (R988C, T1010I), and kinase domain (M1268T). We hypothesized that these mutations would have differential effects on the kinase inhibition. Methods: We modeled the various c-MET mutations from different functional domains of the receptor using a G418-resistant stable Cos-7 transfection cell system to determine their effect on sensitivity to a selective c-MET kinase inhibitor SU11274. Sensitivity to SU11274 inhibition was assayed by phospho-immunoblotting using phospho- specific antibody against the major tyrosine kinase phosphorylation epitopes pY1234/1235 of the c-MET kinase in vitro. Results: First, we identified that mutations in the sema and juxtamembrane domain were activating as defined by ligand-independent constitutive receptor activation. SU11274 was capable of inhibiting ligand induced signaling through the wild-type c-MET as well as mutant c-MET receptors harboring mutations in the sema, juxtamembrane and tyrosine kinase domain. However, SU11274 inhibition of mutant c-MET was mutation-dependent, with the juxtamembrane domain mutations R988C and T1010I resulting in a receptor form that was less sensitive to SU11274. Mutations in the sema and kinase domain also resulted in varying sensitivity to inhibition by SU11274 inhibition. Conclusions: Mutations in the sema and juxtamembrane domain of c-MET result in receptor activation. The small molecule inhibitor SU11274 is active against wild type and mutated c- MET receptor. Further studies to characterize the signaling effects and the mechanism of sensitivity and resistance of c-MET mutations to specific inhibitors are crucial in the successful development of therapeutic c-MET and mutant c-MET inhibitors. No significant financial relationships to disclose.

Sensitivity to EGFR inhibitors based on location of EGFR exon 20 insertion mutations within the tyrosine kinase domain of EGFR.

2012 ◽  
Vol 30 (15_suppl) ◽  
pp. 7523-7523 ◽  
Author(s):  
Daniel Botelho Costa ◽  
Hiroyuki Yasuda ◽  
Natasha J Sng ◽  
Wee-Lee Yeo ◽  
Lorena Lobo de Figueiredo-Pontes ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Cell Line ◽  
Molecular Mechanisms ◽  
Site Directed Mutagenesis ◽  
Egfr Mutations ◽  
Tyrosine Kinase Domain ◽  
Exon 20 ◽  
Insertion Mutations ◽  
Egfr Tkis

7523 Background: Epidermal growth factor receptor (EGFR) mutations (M) define an important subgroup of non-small-cell lung cancer (NSCLC). Most patients whose tumors harbor exon 19 deletions or L858R EGFR M have responses to reversible ATP-mimetic EGFR tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib. Exon 20 insertion M comprise ~5% of EGFR M, occur at the N-lobe of EGFR after its C-helix (AA M766), and nearly all NSCLCs with EGFR exon 20 insertion M display lack of responses to EGFR TKIs (Yasuda H. Lancet Oncol 2011). Methods: We have 1) compiled genotype-clinical outcomes of EGFR exon 20 insertion M NSCLCs to EGFR TKIs, 2) generated a comprehensive panel of exon 20 EGFR M constructs using site-directed mutagenesis and introduced them into Ba/F3 cells for in vitro analysis, and 3) compared NSCLC cell lines with EGFR M to a novel malignant pleural effusion-derived cell line. Results: The disease control rate of gefitinib or erlotinib was significantly higher in EGFR exon 20 insertion M located within the C-helix (3/3,100%) when compared to M following the C-helix (1/14, 7%; p=0.00059). The NSCLC with EGFR-A763_Y764insFQEA (located within the C-helix of EGFR) achieved a partial response to erlotinib that lasted 18 months. Most other exon 20 insertion M-positive NSCLCs did not respond (p=0.07). Eight representative exon 20 insertion M were studied (including EGFR-A763_Y764insFQEA, Y764_S765insHH, A767_V769dupASV, D770_N771insNPG, H773_V774insH). All, but A763_Y764insFQEA, were resistant to micromolar concentrations (C) of EGFR TKIs. Ba/F3 cells with EGFR-A763_Y764insFQEA underwent apoptosis upon exposure to nanomolar C of erlotinib. A patient-derived cell line with EGFR-A763_Y764insFQEA had phosphorylated EGFR, ERK and AKT inhibited by nanomolar C of erlotinib. Conclusions: Not all EGFR exon 20 insertion mutations are resistant to EGFR TKIs, and in specific EGFR-A763_Y764insFQEA is an EGFR TKI-sensitive M. This finding has clinical implications for the care of the 10,000 cases of EGFR exon 20 insertion M NSCLC diagnosed yearly and points towards the need to define the molecular mechanisms that underlie differential responses to EGFR TKIs.

scholarly journals Lyn Physically Associates With the Erythropoietin Receptor and May Play a Role in Activation of the Stat5 Pathway

Blood ◽  
1998 ◽  
Vol 91 (10) ◽  
pp. 3734-3745 ◽  
Author(s):  
Hiroshi Chin ◽  
Ayako Arai ◽  
Hiroshi Wakao ◽  
Ryuichi Kamiyama ◽  
Nobuyuki Miyasaka ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Kinase Domain ◽  
Sh2 Domain ◽  
Erythropoietin Receptor ◽  
Tyrosine Kinase Domain ◽  
Binding Studies ◽  
In Vitro Binding ◽  
Vitro Binding

Protein tyrosine phosphorylation plays a crucial role in signaling from the receptor for erythropoietin (Epo), although the Epo receptor (EpoR) lacks the tyrosine kinase domain. We have previously shown that the Jak2 tyrosine kinase couples with the EpoR to transduce a growth signal. In the present study, we demonstrate that Lyn, a Src family tyrosine kinase, physically associates with the EpoR in Epo-dependent hematopoietic cell lines, 32D/EpoR-Wt and F36E. Coexpression experiments in COS7 cells further showed that Lyn induces tyrosine phosphorylation of the EpoR and that both LynA and LynB, alternatively spliced forms of Lyn, bind with the membrane-proximal 91-amino acid region of the EpoR cytoplasmic domain. In vitro binding studies using GST-Lyn fusion proteins further showed that the Src homology (SH)-2 domain of Lyn specifically binds with the tyrosine-phosphorylated EpoR in lysate from Epo-stimulated cells, whereas the tyrosine kinase domain of Lyn binds with the unphosphorylated EpoR. Far-Western blotting and synthetic phosphopeptide competition assays further indicated that the Lyn SH2 domain directly binds to the tyrosine-phosphorylated EpoR, most likely through its interaction with phosphorylated Y-464 or Y-479 in the carboxy-terminal region of the EpoR. In vitro binding studies also demonstrated that the Lyn SH2 domain directly binds to tyrosine-phosphorylated Jak2. In vitro reconstitution experiments in COS7 cells further showed that Lyn induces tyrosine phosphorylation of Stat5, mainly on Y-694, and activates the DNA-binding and transcription-activating abilities of Stat5. In agreement with this, Lyn enhanced the Stat5-dependent transcriptional activation when overexpressed in 32D/EpoR-Wt cells. In addition, Lyn was demonstrated to phosphorylate the EpoR and Stat5 on tyrosines in vitro. These results suggest that Lyn may play a role in activation of the Jak2/Stat5 and other signaling pathways by the EpoR.

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