Advertisement
JBC

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Originally published In Press as doi:10.1074/jbc.M400590200 on March 31, 2004

J. Biol. Chem., Vol. 279, Issue 24, 25345-25352, June 11, 2004
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
279/24/25345    most recent
M400590200v1
Right arrow Submit a Letter to Editor
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowRequest Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Parmar, S.
Right arrow Articles by Platanias, L. C.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Parmar, S.
Right arrow Articles by Platanias, L. C.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

Role of the p38 Mitogen-activated Protein Kinase Pathway in the Generation of the Effects of Imatinib Mesylate (STI571) in BCR-ABL-expressing Cells*

Simrit Parmar{ddagger}, Efstratios Katsoulidis{ddagger}, Amit Verma{ddagger}, Yongzhong Li{ddagger}, Antonella Sassano{ddagger}, Lakhvir Lal{ddagger}, Beata Majchrzak§, Farhad Ravandi¶, Martin S. Tallman{ddagger}, Eleanor N. Fish§, and Leonidas C. Platanias{ddagger}||

From the {ddagger}Robert H. Lurie Comprehensive Cancer Center and Division of Hematology Oncology, Northwestern University Medical School, Chicago, Illinois 60611, the Section of Hematology-Oncology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60607, and the §Division of Cell & Molecular Biology, Toronto Research Institute, University Network and Department of Immunology, University of Toronto, Toronto, Ontario M5G 2M1, Canada

Received for publication, January 20, 2004 , and in revised form, March 15, 2004.


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Imatinib mesylate (STI571), a specific inhibitor of the BCR-ABL tyrosine kinase, exhibits potent antileukemic effects in vitro and in vivo. Despite the well established role of STI571 in the treatment of chronic myelogenous leukemia, the precise mechanisms by which inhibition of BCR-ABL tyrosine kinase activity results in generation of antileukemic responses remain unknown. In the present study we provide evidence that treatment of CML-derived BCR-ABL-expressing leukemia cells with STI571 results in activation of the p38 mitogen-activated protein (MAP) kinase signaling pathway. Our data indicate that STI571 induces phosphorylation of the p38 and activation of its kinase domain, in KT-1 cells and other BCR-ABL-expressing cell lines. We also identify the kinases MAP kinase-activated protein kinase-2 and Msk1 as two downstream effectors of p38, activated during inhibition of BCR-ABL activity by STI571. Importantly, pharmacological inhibition of p38 reverses the growth inhibitory effects of STI571 on primary leukemic colony-forming unit granulocyte/macrophage progenitors from patients with CML. Altogether, our data establish that activation of the p38 MAP kinase signaling cascade plays an important role in the generation of the effects of STI571 on BCR-ABL-expressing cells. They also suggest that, in addition to activation of mitogenic pathways, BCR-ABL promotes leukemogenesis by suppressing the function of growth inhibitory signaling cascades.


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
The introduction of STI571 (imatinib mesylate) in the treatment of chronic myelogenous leukemia (CML)1 has been a major medical advance for the management of this disease and has provided an important paradigm for the development of tyrosine kinase inhibitors in the treatment of human malignancies (1–7). CML is a clonal myeloproliferative disorder of stem cells, whose hallmark is the expression of the BCR-ABL oncoprotein in the leukemic cells. BCR-ABL is the protein product of the bcr-abl oncogene, which results from the fusion of bcr to c-abl, as a consequence of the reciprocal translocation between chromosomes 9 and 22 (8–10). The abnormal BCR-ABL tyrosine kinase is constitutively activated and plays a critical role in the pathogenesis of CML (11, 12), likely via phosphorylation of multiple downstream protein targets, resulting in activation of mitogenic cellular pathways (13).

STI571 is an ABL tyrosine kinase inhibitor (14) that selectively inhibits the kinase activity of the abnormal BCR-ABL protein and suppresses the growth of BCR-ABL-expressing leukemic progenitors (14, 15). Extensive clinical studies have established the efficacy of this agent in the treatment of CML patients, including patients in the chronic phase of the disease, as well as patients in the accelerated or blast phases of this malignancy (1–7). The recent approval of STI571 by the Food and Drug Administration for the treatment of CML and its introduction in clinical oncology practice has had a dramatic impact on the way this leukemia is managed. Importantly, it has provided a paradigm for the development of specific therapeutic approaches for other leukemias and malignancies where tyrosine kinases are known to play pathogenetic roles.

Previous studies have shown that STI571 acts by binding the inactive form of the Abl kinase domain of BCR-ABL (reviewed in Ref. 7), and the structural basis for the autoinhibition of the c-Abl tyrosine kinase has been solved (16, 17). Because BCR-ABL activates multiple downstream mitogenic effectors and anti-apoptotic pathways (7, 13), it is presumed that the anti-neoplastic effects of imatinib mesylate are primarily mediated by the blockade of BCR-ABL-generated mitogenic signals. However, the downstream targets of BCR-ABL, whose inhibition accounts for the antileukemic effects of STI571, remain to be precisely defined. Another potential mechanism by which STI571 exhibits antileukemic activity may involve the restoration of function of growth inhibitory pathways that may be abnormally suppressed by BCR-ABL. It is of interest that overexpression of BCR-ABL has been shown to suppress gene transcription in response to IFN{alpha} (18), a cytokine to which CML cells exhibit unique sensitivity in vitro and in vivo (reviewed in Refs. 19 and 20). Furthermore, recent studies have indicated that overexpression of BCR-ABL in embryonic stem cell-derived hematopoietic progenitors suppresses the p38 MAP kinase pathway (21), whose function is required for IFN{alpha}-dependent gene transcription (22–24) and generation of growth inhibitory responses (25).

In the present study we examined whether STI571-dependent suppression of leukemic cell growth is in part mediated by restoration of activation of the p38 MAP kinase. Our studies establish that pharmacological inhibition of p38 reverses the suppressive effects of STI571 on primary leukemic CFU-GM progenitors, indicating that activation of this signaling cascade is essential for the antileukemic effects of imatinib mesylate. In other studies we identify the p38-dependent kinases Map-KapK-2 and Msk1 as putative downstream mediators of the STI571-activated form of p38. Altogether, our studies strongly suggest that reversal of the inhibitory effects of BCR-ABL on the activation of the p38 MAP kinase pathway plays a critical role in the induction of STI571 responses in CML cells.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Cells and Reagents—The CML-derived KT-1 cell line was grown in RPMI 1640 medium supplemented with 10% fetal bovine serum and antibiotics. The EM3 and EM2 cell lines were also grown in RPMI 1640–10% fetal bovine serum. IFN{alpha} was provided by Hoffman Laroche. STI571 was provided by Novartis. Antibodies against the phosphorylated forms of p38 and Msk1 were obtained from Cell Signaling Technology (Beverly, MA). Antibodies against p38 were obtained from Santa Cruz Biotechnology (Santa Cruz, CA) and BD Transduction Laboratories. A monoclonal antibody against phosphotyrosine (4G-10) was obtained from Upstate Biotechnology Inc. Antibodies against phospho-Erk1/2 and an anti-Erk antibody were obtained from Cell Signaling Technology (Beverly MA). The p38 MAP kinase inhibitors SB203580 and SB202190 and the MEK kinase inhibitor PD098059 were purchased from Calbiochem Inc.

Cell Lysis and Immunoblotting—The cells were treated with 1 µM of STI571 for the indicated times and lysed as described previously (26, 27). Immunoprecipitations and immunoblotting using an ECL method were performed as described previously (26, 27).

Isolation of Peripheral Blood Granulocytes—Informed consent was obtained from patients with CML, according to the guidelines established by the Institutional Review Board of Northwestern University Medical School. Polymorphonuclear leukocytes were separated from peripheral venous blood using the mono-poly resolving medium (ICN Biomedicals, Aurora, OH), as described previously (25). Briefly, after centrifugation at 300 x g for 30 min at room temperature, the polymorphonuclear band was transferred into an individual tube. The cells were washed with culture medium and were subsequently resuspended in culture medium prior to treatment with STI571.

Cell Proliferation Assays—The cells were incubated in the presence or absence of the indicated doses of STI571 for 7 days. Cell proliferation assays using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay system were performed as in previous studies (25).

In Vitro Kinase Assays—In vitro kinase assays to detect the activation of the MapKapK-2 by STI571 were performed as described previously (28, 29). To examine the induction of Msk1 kinase activity, cell lysates from STI571-treated cells were immunoprecipitated with either an anti-Msk1 antibody or control nonimmune RIgG, and in vitro kinase assays were performed as described previously (24). The values were calculated by subtracting nonspecific activity, detected in RIgG immunoprecipitates, from kinase activity detected in anti-Msk1 immunoprecipitates.

Hematopoietic Progenitor Cell Assays—The effects of STI571 on the growth of hematopoietic progenitors from patients with CML was determined in methylcellulose assays as described previously (30, 31). Briefly, bone marrow aspirate specimens were obtained under local anesthesia from patients with CML, after obtaining Institutional Review Board-approved informed consent. Bone marrow mononuclear cells were separated by Ficoll-Hypaque sedimentation, and the cells were cultured in a methylcellulose mixture containing hematopoietic growth factors (30, 31) in the presence or absence of STI571 (1 µM) and/or pharmacological inhibitors of MAP kinases. The concentrations of the different MAP kinase inhibitors that were used were 10 µM for SB202190, 10 µM for SB203580, and 2 µM for PD98059, as in previous studies (29–31, 71). In patients where bone marrow aspirate was not available, peripheral blood was collected after obtaining informed consent, and peripheral blood hematopoietic progenitors were separated and used for the clonogenic assays in methylcellulose. CFU-GM from leukemic samples were scored on day 14 of culture.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
We initially examined whether treatment of KT-1 cells with imatinib mesylate results in phosphorylation of the p38 MAP kinase. The initial concentration of STI571 that was used for these experiments was 1 µM, because this concentration appears to be clinically relevant and has been previously shown to block growth of BCR-ABL-expressing cell lines and CML-derived hematopoietic progenitors (1, 64, 72). KT-1 cells were incubated in the presence or absence of STI571. The cells were subsequently lysed, and equal amounts of total cell lysates were analyzed by SDS-PAGE and immunoblotted with an anti-phospho-p38 antibody. Some weak base-line phosphorylation of p38 was detectable in untreated cells, and such phosphorylation was strongly increased after STI571 treatment (Fig. 1, A and B). Such phosphorylation of p38 was also seen in the EM2 (Fig. 1, C and D) and EM3 (Fig. 1, E and F) cell lines, which also express BCR-ABL (32). On the other hand and consistent with previous reports (41), STI571 treatment induced dephosphorylation of Erk1/2 kinases (Fig. 1, G and H), which are activated by BCR-ABL (41). The phosphorylation of p38 in response to STI571 treatment of cells was dose-dependent, with the signal maximizing at 1 µM concentration of STI571 (Fig. 2, A and B), at which concentration there was also strong inhibition of cell proliferation of KT-1 cells, as determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays (Fig. 2C).



View larger version (31K):
[in this window]
[in a new window]
  		FIG. 1.
STI571 induces phosphorylation of p38 in BCR-ABL-expressing cell lines. A, KT-1 cells were incubated for 30 min in the presence or absence of 1 µM of STI571, as indicated. Equal amounts of total cell lysates (100 µg/lane) were analyzed by SDS-PAGE and immunoblotted with an antibody against the phosphorylated/activated form of p38 MapK. B, the blot shown in A was stripped and reprobed with an antibody against p38 MapK to control for protein loading. C, EM2 cells were incubated with STI571 (1 µM) for different time points as indicated. Equal amounts of total cell lysates (100 µg/lane) were analyzed by SDS-PAGE and immunoblotted with an antibody against the phosphorylated/activated form of p38 MapK. D, the blot shown in C was stripped and reprobed with an antibody against p38 to control for protein loading. E, EM3 cells were incubated with STI571 (1 µM) for different time points as indicated. Equal amounts of total cell lysates (100 µg/lane) were analyzed by SDS-PAGE and immunoblotted with an antibody against the phosphorylated/activated form of p38 MapK. F, the blot shown in E was stripped and reprobed with an antibody against p38 to control for protein loading. G, KT-1 cells were incubated for the indicated times in the presence or absence of 1 µM of STI571 as indicated. Equal amounts of total cell lysates (100 µg/lane) were analyzed by SDS-PAGE and immunoblotted with an antibody against that recognizes the phosphorylated forms of Erk1 and Erk2. H, the blot shown in G was stripped and reprobed with an anti-Erk1/2 antibody, to control for protein loading.

 



View larger version (9K):
[in this window]
[in a new window]
  		FIG. 2.
STI571-dependent phosphorylation of the p38 MAP kinase. A, KT-1 cells were treated with the indicated doses of STI571 for 30 min. Equal amounts of total cell lysates (100 µg/lane) were analyzed by SDS-PAGE and immunoblotted with an antibody against the phosphorylated/activated form of p38 MapK. B, the blot shown in A was stripped and reprobed with an antibody against p38 MapK to control for protein loading. C, KT-1 cells were incubated with the indicated concentrations of STI571, and cell proliferation was assessed using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay.

 
To directly examine whether STI571-dependent phosphorylation of p38 results in activation of its kinase domain, in vitro kinase assays were carried out on p38 immunoprecipitates from STI571-treated KT-1 cells. Treatment of KT-1 cells with STI571 resulted in strong induction of p38 MAP kinase activity, evidenced by the phosphorylation of ATF-2 used as an exogenous substrate (Fig. 3, A and B), demonstrating that STI571-dependent phosphorylation of p38 results in functional activation of its kinase domain. As expected, treatment of KT-1 cells with STI571 also resulted in dephosphorylation of BCR-ABL (Fig. 3, C and D), suggesting that activation of p38 in response to STI571 results from reversal of BCR-ABL-generated inhibitory effects on p38 activity. Consistent with this, STI571 did not induce phosphorylation/activation of p38 in the U-266 (Fig. 4, A and B) and Molt-4 (Fig. 4, C and D) hematopoietic cell lines that do not express BCR-ABL. On the other hand, STI571-induced phosphorylation of p38 in primary peripheral blood granulocytes from a CML patient (Fig. 4, A and B), suggesting that such phosphorylation occurs under physiological conditions and may play an important role in the generation of the effects of STI571 in CML.



View larger version (23K):
[in this window]
[in a new window]
  		FIG. 3.
STI571-dependent induction of p38 MAP kinase activity. A, KT-1 cells were treated with STI571 (1 µM) for the indicated times. The cells were lysed, and the total cell lysates were immunoprecipitated (IP) with an antibody against p38. Immunoprecipitated proteins were subjected to in vitro kinase assays, using ATF-2 as an exogenous substrate. The proteins were resolved by SDS-PAGE and transferred to Immobilon. The phosphorylated form of ATF-2 was detected by autoradiography. B, The membrane shown in A was subsequently immunoblotted with an antibody against phospho-ATF-2. C, KT-1 cells were treated with STI571 (1 µM) for the indicated times. Equal amounts of total cell lysates were analyzed by SDS-PAGE and immunoblotted with an anti-phospho-ABL antibody to detected phosphorylated BCR-ABL. D, the blot shown in C was stripped and reprobed with an antibody against ABL, to detect BCR-ABL.

 



View larger version (32K):
[in this window]
[in a new window]
  		FIG. 4.
Lack of STI571-inducible phosphorylation/activation of p38 in non-BCR-ABL-expressing cell lines. A, U266 cells or primary granulocytes from the peripheral blood of a patient with CML were incubated for the indicated time points in the presence or absence of 1 µM of STI571. Equal amounts of total cell lysates (100 µg/lane) were resolved by SDS-PAGE and immunoblotted with an antibody against the phosphorylated/activated form of p38 MapK. B, the blot shown in A was stripped and reprobed with an antibody against p38 MapK to control for protein loading. C, Molt-4 cells were incubated for the indicated time points in the presence or absence of 1 µm of STI571. Equal amounts of total cell lysates (100 µg/lane) were resolved by SDS-PAGE and immunoblotted with an antibody against the phosphorylated/activated form of p38 MapK. D, the blot shown in C was stripped and reprobed with an antibody against p38 MapK to control for protein loading.

 
The p38 MAP kinase has been previously shown to be activated by IFN{alpha} in BCR-ABL-expressing cells and to mediate the generation of the antiproliferative effects of IFN{alpha} on CML progenitors (25). There is also evidence that STI571 and IFN{alpha} exhibit synergistic effects on the suppression of growth of CML cells (38–40). The fact that treatment of CML-derived cell lines with STI571 resulted in activation of the p38 MAP kinase raised the possibility that STI571 may be modulating other Type I IFN-signaling pathways, as well. To determine whether other IFN-regulated pathways are modulated by STI571 treatment of CML cells, experiments were performed in which the effects of STI571 on the IFN-dependent activation of STAT proteins were evaluated. As shown in Fig. 5, treatment of cells with STI571 did not induce tyrosine phosphorylation of STAT1 (Fig. 5, A and B), STAT3 (Fig. 5, C and D), or STAT5 (Fig. 5, E and F), nor did it have any effects on the IFN{alpha}-dependent phosphorylation of these STAT proteins (Fig. 5). Consistent with this, STI571 did not affect the formation of STAT-containing DNA-binding complexes that bind to IFN-stimulated response element or IFN-{gamma}-activated site elements, as shown by gel shift assays (Fig. 5, G and H). Thus, STI571 selectively activates the p38 MAP kinase pathway in CML cells, whereas it does not appear to have any effects on the activation of IFN{alpha}-regulated STAT pathways.



View larger version (25K):
[in this window]
[in a new window]
  		FIG. 5.
STI571 does not exhibit regulatory effects on the activation of STAT proteins and the IFN{alpha}-dependent formation of ISGF3 and SIF DNA-binding complexes. A, KT-1 cells were incubated in the presence or absence of the indicated concentrations of STI571 (STI) for 60 min, as indicated. The cells were subsequently treated with IFN{alpha} as indicated, and after cell lysis, the proteins were resolved by SDS-PAGE and immunoblotted with an antibody against the phosphorylated form of STAT 1 on tyrosine 701. B, the blot shown in A was stripped and reprobed with an anti-STAT1 antibody to control for loading. C, KT-1 cells were incubated in the presence or absence of the indicated concentrations of STI571 for 60 min, as indicated. The cells were subsequently treated with IFN{alpha} as indicated, and after cell lysis, the proteins were resolved by SDS-PAGE and immunoblotted with an antibody against the phosphorylated form of STAT3 on tyrosine 705. D, the blot shown in C was stripped and reprobed with an anti-STAT1 antibody, to control for loading. E, KT-1 cells were incubated in the presence or absence of the indicated concentrations of STI571 for 60 min, as indicated. The cells were subsequently treated with IFN{alpha} as indicated, and after cell lysis, the lysates were immunoprecipitated (IP) with an antibody against STAT5. Immunoprecipitated proteins were resolved by SDS-PAGE and immunoblotted with an antiphosphotyrosine antibody. F, the blot shown in E was stripped and reprobed with an anti-STAT5 antibody, to control for loading. G and H, actively growing KT-1 cells were preincubated for 30 min with 1 µM STI571 as indicated. The cells were subsequently treated with 10,000 IU of IFN{alpha} in the continuous presence or absence of STI571 as indicated. The nuclear extracts were reacted with 40,000 cpm of a 32P-labeled IFN-stimulated response element probe (G) or a 32P-labeled SIS-inducible element probe (H), and the complexes were resolved by native gel electrophoresis and visualized by autoradiography. WB, Western blot.

 
To better understand the mechanisms by which the p38 MAP kinase pathway may participate in the generation of STI571-dependent responses, we sought to identify p38-regulated downstream effector kinases that may be activated in an STI571-inducible manner. The kinase MapKapK-2 is activated in response to stress signals, as well as during engagement of the Type I IFN receptor in BCR-ABL-expressing cells, and mediates p38-dependent functional responses (24). We determined whether this kinase is activated in response to STI571 treatment of BCR-ABL cells by performing in vitro kinase assays in anti-MapKapK-2 immunoprecipitates from STI571-treated cell lysates. Treatment of KT-1 (Fig. 6A) or EM3 (Fig. 6B) cells with STI571 resulted in strong activation of the Map-KapK-2 kinase, evidenced by the phosphorylation of Hsp-25 in the in vitro kinase assays. Such activation was blocked by pretreatment of cells with SB203580, indicating that it occurs downstream of p38 (Fig. 6, A and B). In a similar manner, STI571 treatment of the cells resulted in phosphorylation/activation of Msk1 (Fig. 6, C and D), a kinase that acts as a downstream effector for p38, and whose function has been implicated in the regulation of stress-induced nuclear histone phosphorylation, chromatin remodeling, and immediate early gene expression (33–37). To examine whether STI571-dependent phosphorylation of Msk1 results in activation of its kinase domain, experiments were performed in which lysates from STI571-treated cells were immunoprecipitated with an anti-Msk1 antibody, and in vitro kinase assays were carried out on the immunoprecipitates. STI571 treatment resulted in induction of Msk1 kinase activity (Fig. 6E). Such activation was blocked by pretreatment of cells with SB203580 (Fig. 6E), strongly suggesting that Msk1 acts as a downstream effector of the STI571-activated p38 MAP kinase.



View larger version (19K):
[in this window]
[in a new window]
  		FIG. 6.
STI571-dependent activation of MapKapK-2 and Msk-1. A, KT-1 cells were preincubated for 30 min at 37 °C in the presence or absence of SB203580 (10 µM) as indicated. The cells were subsequently incubated in the presence or absence of STI571 (STI, 1 µM) for 30 min as indicated in the continuous presence or absence of SB203580. The cells were subsequently lysed; the cell lysates were immunoprecipitated (IP) with an antibody against MapKapK-2; and in vitro kinase assays were carried out on the immunoprecipitates using Hsp25 as an exogenous substrate. The proteins were analyzed by SDS-PAGE, and the phosphorylated form of Hsp25 was detected by autoradiography. B, EM3 cells were preincubated for 30 min at 37 °C in the presence or absence of SB203580 (10 µM) as indicated. The cells were subsequently incubated in the presence or absence of STI571 (1 µM) for 30 min as indicated in the continuous presence or absence of SB203580. The cells were subsequently lysed; the cell lysates were immunoprecipitated with an antibody against MapKapK-2, and in vitro kinase assays were carried out on the immunoprecipitates using Hsp25 as an exogenous substrate. The proteins were analyzed by SDS-PAGE, and the phosphorylated form of Hsp25 was detected by autoradiography. C, KT-1 cells were incubated with STI571 for the indicated times. Equal amounts of total cell lysates were analyzed by SDS-PAGE and immunoblotted with an antibody against the phosphorylated form of Msk-1 on serine 376. D, the blot shown in C was stripped and reprobed with an anti-tubulin antibody to control for protein loading. E, KT-1 cells were preincubated in the presence or absence of SB203580 for 60 min as indicated. The cells were subsequently treated with STI571 for 30 min, in the continuous absence or presence of SB203580. The cell lysates were immunoprecipitated with an anti-Msk1 antibody, and in vitro kinase assays were performed on the immunoprecipitates. The means ± S.E. of two independent experiments are shown.

 
In subsequent studies, we sought to identify the functional relevance of imatinib-dependent activation of p38 in BCR-ABL-expressing cells. We determined whether activation of p38 MAP kinase is required for the generation of inhibitory effects of STI571 on primary leukemic progenitors from patients with chronic myelogenous leukemia. For this purpose, the effect of SB203580 on the suppression of bone marrow- or peripheral blood-derived leukemic CFU-GM progenitors was evaluated in clonogenic assays in methylcellulose. Samples from different patients with CML were evaluated. STI571 inhibited colony formation of myeloid progenitors from all patients with CML studied (Fig. 7). Concomitant treatment of cells with SB203580 partially reversed the growth inhibitory effects of STI571 on the leukemic progenitors (Fig. 7, A and B), indicating that restoration of activation of p38 activity is essential for the induction of an antileukemic response. Similarly, another p38 inhibitor, SB202190, also reversed STI571-dependent suppression of leukemic CFU-GM progenitors (Fig. 7, C and D). On the other hand, the MEK/Erk inhibitor PD98059 did not reverse such effects and, on the contrary, slightly enhanced the suppression of leukemic CFU-GM growth (Fig. 7D).



View larger version (14K):
[in this window]
[in a new window]
  		FIG. 7.
STI571 inhibits the growth of leukemic myeloid progenitors from CML patients in a p38 MAP kinase-dependent manner. Peripheral blood mononuclear cells from three different CML patients (A, C, and D) or bone marrow mononuclear cells from one patient (B) were plated in a methylcellulose culture assay system with 1 µM of STI571 in the presence or absence of SB203580, SB202190, or PD98059, as indicated. Leukemic CFU-GM progenitor colonies were scored on day 14 of culture. The data are expressed as percent control of CFU-GM colony numbers for untreated cells. The absolute untreated colony numbers were 33 for A, 22 for B, 166 for C, and 70 for D.

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
The remarkable clinical efficacy of STI571 in the treatment of CML has provided an important paradigm for the development of pharmacological agents that specifically target tyrosine kinases that regulate survival and growth of malignant cells. STI571 exhibits its activity by blocking the function of the abnormal BCR-ABL tyrosine kinase, which causes the malignant transformation in CML, and is currently the first line of treatment for patients with this leukemia. Despite the substantial advances in this research area over the last few years, the precise mechanisms and pathways that regulate induction of STI571 responses after blocking the kinase activity of BCR-ABL are not known. STI571 has been shown to regulate the phosphorylation and/or activation of several proteins that are direct or indirect downstream targets for the kinase activity of BCR-ABL. These include the adaptor protein CrkL (41–43), the multisite docking proteins CBL (43) and IRS-1 (44), the Shc oncogenic protein (42), the Erk kinase (41), the Akt kinase (45), and the forkhead transcription factor FKHRL1 (46). Apparently, the inhibition of mitogenic signals induced by BCR-ABL plays a major role in the induction of the antileukemic effects of imatinib mesylate. However, it is possible that reversal of BCR-ABL-mediated suppression of pathways that mediate growth inhibitory signals is also required for the antineoplastic effects of STI571 in chronic myelogenous leukemia.

In the current report we provide the first evidence that the p38 MAP kinase pathway is activated during STI571 treatment of BCR-ABL-expressing cells. Our data demonstrate that STI571 induces phosphorylation of the p38 MAP kinase and activation of its kinase domain. We also demonstrate that MapKapK-2 and Msk1 are activated in a p38-dependent manner during STI571 treatment of CML cells. The latter findings provide further evidence that imatinib mesylate induces functional activation of p38, resulting in downstream signaling events that regulate p38-mediated biological responses. Most importantly, our findings directly establish that inhibition of p38 MAP kinase activity reverses the growth inhibitory effects of STI571 on primary CML-derived leukemic progenitors. This is demonstrated by studies using the pyridinyl imidazole compounds SB203580 and SB202190, whose high selectivity and specificity for the p38 MAP kinase has been established by mutagenesis studies and x-ray crystallography (47–51). In contrast, inhibition of the MEK/Erk pathway, using the PD98059 pharmacological inhibitor, enhances the inhibitory effects of STI571 on the growth of primary leukemic CFU-GM progenitors. These findings are in agreement with a previous study demonstrating that MEK kinase inhibitors enhance the effects of STI571 on BCR-ABL-expressing cell lines (52) and further support the concept that combined use of STI571 with MEK inhibitors may prove useful in the future treatment of CML.

The members of the p38 family of kinases (53–58) are activated in response to stress and regulate signals essential for important biological responses, such as phosphorylation of transcription factors and gene transcription, cellular differentiation, cytokine production, and apoptosis (53–58). The p38 MAP kinase pathway is activated by IFN{alpha} and appears to play an important in the regulation of gene transcription by the Type I IFN receptor and the induction of interferon responses (22–24, 59). This is of particular interest, because IFN{alpha} is a cytokine that has important clinical activity in the treatment of CML, and prior to the introduction of STI571, it was the pharmacological agent of choice for patients with this leukemia (reviewed in Refs. 60 and 61). Our previous studies have shown that IFN{alpha} activates the p38 MAP kinase cascade in BCR-ABL-expressing cells and that pharmacological inhibition of such activation reverses the growth inhibitory effects of this cytokine on bone marrow-derived leukemic progenitors from patients with CML (25). Taken together with the results of the current study, these findings suggest that the p38 pathway is a common effector for the generation of the antileukemic effects of IFN{alpha} and STI571 in CML cells. They also further support the hypothesis that one of the mechanisms by which BCR-ABL promotes leukemogenesis may be suppression of the p38 pathway and are consistent with the observed suppression of p38 in embryonic cell-derived hematopoietic progenitors in which BCR-ABL is exogenously expressed (21).

There is now accumulating evidence that resistance to the effects of STI571 occurs in vitro and in vivo (6, 7, 62, 63). The most common mechanism of resistance appears to result from point mutations of the kinase domain of BCR-ABL, which result in decrease or abrogation of the affinity of STI571 (reviewed in Ref. 6). However, additional mechanisms of resistance, unrelated to point mutation of BCR-ABL, also occur and may play a role in the development of clinical refractoriness to the drug. For instance, recent studies have implicated overexpression of the Lyn and/or Hck kinases of the Src family in the development of BCR-ABL independence (65), whereas other studies have demonstrated that MDR1 gene overexpression in CML cells also accounts for STI571 resistance (66). Based on our findings, the function of p38 and its downstream effectors are essential for the generation of an antileukemic response by STI571. It is therefore possible that resistance to imatinib may also result from defects on the activation of the p38 MAP kinase pathway in certain cases of CML, and this should be directly examined in future studies. It should be also pointed out that pharmacological inhibitors of p38 are currently under development for the treatment of rheumatoid arthritis, bronchial asthma, and other inflammatory diseases (67–70), based on their well documented ability to decrease production of proinflammatory cytokines. Our findings raise the possibility that concomitant use of STI571 with such pharmacological inhibitors may abrogate the antitumor effects of STI571 in vivo. Perhaps, pharmacological inhibitors of the p38 pathway should be avoided in the design and development of future trials including STI571 in CML.


   FOOTNOTES
 
* This work was supported by National Institutes of Health Grants CA94079 and CA77816 (to L. C. P.), a merit review grant from the Department of Veterans Affairs (to L. C. P.), Grant DAMD 17-03-1-0254 from the Department of Defense (to L. C. P.), and Canadian Institutes of Health Research Grant MOP 15094 (to E. N. F.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Back

|| To whom correspondence should be addressed: Robert H. Lurie Comprehensive Cancer Center, Northwestern University Medical School, 710 North Fairbanks St., Olson 8250, Chicago, IL 60611. Tel.: 312-503-4267; Fax: 312-908-1372; E-mail: l-platanias{at}northwestern.edu.

1 The abbreviations used are: CML, chronic myelogenous leukemia; MAP, mitogen-activated protein; IFN{alpha}, interferon {alpha}; MapK, mitogen-activated protein kinase, MapKapK; MAP kinase-activated protein kinase; Msk, mitogen and stress-activated kinase; CFU-GM, colony-forming unit granulocyte/macrophage; Erk, extracellular signal-regulated kinase; STAT, signal transducer and activator of transcription; MEK, MapK/Erk kinase. Back



   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 

  1. Druker, B. J., Talpaz, M., Resta, D. J., Peng, B., Buchdunger, E., Ford, J. M., Lydon, N. B., Kantarjian, H., Capdeville, R., Ohno-Jones, S., and Sawyers, C. L. (2001) N. Engl. J. Med. 344, 1031-1037[Abstract/Free Full Text]
  2. Druker, B. J., Sawyers, C. L., Kantarjian, H., Resta, D. J., Reese, S. F., Ford, J. M., Capdeville, R., and Talpaz, M. (2001) N. Engl. J. Med. 344, 1038-1042[Abstract/Free Full Text]
  3. O'Brien, S. G., Guilhot, F., Larson, R. A., Gathmann, I., Baccarani, M., Cervantes, F., Cornelissen, J. J., Fischer, T., Hochhaus, A., Hughes, T., Lechner, K., Nielsen, J. L., Rousselot, P., Reiffers, J., Saglio, G., Shepherd, J., Simonsson, B., Gratwohl, A., Goldman, J. M., Kantarjian, H., Taylor, K., Verhoef, G., Bolton, A. E., Capdeville, R., and Druker, B. J. (2003) N. Engl. J. Med. 348, 994-1004[Abstract/Free Full Text]
  4. Mauro, M. J., O'Dwyer, M., Heinrich, M. C., and Druker, B. J. (2002) J. Clin. Oncol. 20, 325-334[Abstract/Free Full Text]
  5. Kurzrock, R., Kantarjian, H. M., Druker, B. J., and Talpaz, M. (2003) Ann. Int. Med. 138, 819-830[Abstract/Free Full Text]
  6. Druker, B. J. (2003) Semin. Hematol. 40, 50-58[Medline] [Order article via Infotrieve]
  7. Deininger, M. W. N., and Druker, B. J. (2003) Pharmacol. Rev. 55, 401-423[Abstract/Free Full Text]
  8. Groffen, J., Stephenson, J. R., Heisterkamp, N., de Klein, A., Bartram, C. R., and Grosveld, G. (1984) Cell 36, 93-99[CrossRef][Medline] [Order article via Infotrieve]
  9. Heisterkamp, N., Stam, K., Groffen, J., de Klein, A., and Grosveld, G. (1985) Nature 315, 758-761[CrossRef][Medline] [Order article via Infotrieve]
  10. Ben-Neriah, Y., Daley, G. Q., Mess-Mason, A.-M., Witte, O. N., and Baltimore, D. (1986) Science 233, 212-214[Abstract/Free Full Text]
  11. Daley, G. Q., Van Etten, R. A., and Baltimore, D. (1990) Science 247, 824-830[Abstract/Free Full Text]
  12. Lugo, T. G., Pendergast, A. M., Muller, A. J., and Witte, O. N. (1990) Science 247, 1079-1082[Abstract/Free Full Text]
  13. Sattler, M., and Salgia, R. (1998) Leukemia 12, 637-644[CrossRef][Medline] [Order article via Infotrieve]
  14. Buchdunger, E., Zimmermann, J., Mett, H., Meyer, T., Muller, M., Druker, B. J., and Lydon, N. B. (1996) Cancer Res. 56, 100-104[Abstract/Free Full Text]
  15. Druker, B. J., Tamura, S., Buchdunger, E., Ohno, S., Segal, G. M., Fanning, S., Zimmermann, J., and Lydon, N. B. (1996) Nat. Med. 2, 561-566[CrossRef][Medline] [Order article via Infotrieve]
  16. Nagar, B., Bornmann, W. G., Pellicena, P., Schindler, T., Veach, D. R., Miller, W. T., Clarkson, B., and Kuriyan, J. (2002) Cancer Res. 62, 4236-4243[Abstract/Free Full Text]
  17. Nagar, B., Hantschel, O., Young, M. A., Scheffzek, K., Veach, D., Bornmann, W., Clarkson, B., Superti-Furga, G., and Kuriyan, J. (2003) Cell 112, 859-871[CrossRef][Medline] [Order article via Infotrieve]
  18. Grumbach, I. M., Mayer, I. A., Uddin, S., Lekmine, F., Majchrzak, B., Yamauchi, H., Fujita, S., Druker, B., Fish, E. N., and Platanias, L. C. (2001) Br. J. Haematol. 112, 327-336[CrossRef][Medline] [Order article via Infotrieve]
  19. Verma, A., and Platanias, L. C. (2002) Leuk. Lymphoma 43, 703-709[CrossRef][Medline] [Order article via Infotrieve]
  20. Wetzler, M., Kantarjian, H., and Talpaz, M. (1995) Am. J. Med. 99, 402-411[CrossRef][Medline] [Order article via Infotrieve]
  21. Wong, S., McLaughlin, J., Cheng, D., and Witte, O. N. (2003) Blood 101, 4088-4097[Abstract/Free Full Text]
  22. Uddin, S., Majchrzak, B., Woodson, J. Arunkumar, P., Alsayed, Y., Pine, R, Young, P. R., Fish, E. N., and Platanias, L. C. (1999) J. Biol. Chem. 274, 30127-30131[Abstract/Free Full Text]
  23. Uddin, S., Lekmine, F., Sharma, N., Majchrzak, B., Mayer, I., Young, P. R., Bokoch, G. M., Fish, E. N., and Platanias, L. C. (2000) J. Biol. Chem. 275, 27634-27640[Abstract/Free Full Text]
  24. Li, Y., Sassano, A., Majchrzak, B., Deb, D. K., Levy, D. E., Gaestel, M., Nebreda, A. R., Fish, E. N., and Platanias, L. C. (2004) J. Biol. Chem. 279, 970-979[Abstract/Free Full Text]
  25. Mayer, I. A., Verma, A., Grumbach, I. M., Uddin, S., Lekmine, F., Ravandi, F., Majchrzak, B., Fujita, S., Fish, E. N., and Platanias, L. C. (2001) J. Biol. Chem. 276, 28570-28577[Abstract/Free Full Text]
  26. Uddin, S., Yenush, L., Sun, X. J., Sweet, M. E., White, M. F., and Platanias, L. C. (1995) J. Biol. Chem. 270, 15938-15941[Abstract/Free Full Text]
  27. Ahmad, S., Alsayed, Y. M., Druker, B. J., and Platanias, L. C. (1997) J. Biol. Chem. 272, 29991-29994[Abstract/Free Full Text]
  28. Alsayed, Y., Uddin, S., Mahmud, N., Lekmine, F., Kalvakolanu, D. V., Minucci, S., Bokoch, G., and Platanias, L. C. (2001) J. Biol. Chem. 276, 4012-4019[Abstract/Free Full Text]
  29. Verma, A., Mohindru, M., Deb, D. K., Sassano, A., Kambhampati, S., Ravandi, F., Minucci, S., Kalvakolanu, D. V., and Platanias, L. C. (2002) J. Biol. Chem. 277, 44988-44995[Abstract/Free Full Text]
  30. Verma, A., Deb, D. K., Sassano, A., Uddin, S., Varga, J., Wickrema, A., and Platanias, L. C. (2002) J. Biol. Chem. 277, 7726-7735[Abstract/Free Full Text]
  31. Verma, A., Deb, D. K., Sassano, A., Kambhampati, S., Wickrema, A., Uddin, S., Mohindru, M., Van Besien, K., and Platanias, L. C. (2002) J. Immunol. 168, 5984-5988[Abstract/Free Full Text]
  32. Raskind, W. H., Disteche C. M., Keating, A., and Singer, J. W. (1987) Cancer Genet. Cytogenet. 25, 271-284[CrossRef][Medline] [Order article via Infotrieve]
  33. Deak, M., Clifton, A. D., Lucocq, J. M., and Alessi, D. R. (1998) EMBO J. 17, 4426-4441[CrossRef][Medline] [Order article via Infotrieve]
  34. Thonpson, S., Clayton, A. L., Hazzalin, C. A., Rose, S., Barratt, M. J., and Mahadevan L. C. (1999) EMBO J. 18, 4779-4793[CrossRef][Medline] [Order article via Infotrieve]
  35. Soloaga, A., Thomson, S., Wiggin, G. R., Rampersaud, N., Dyson, M. H., Hazzalin, C. A., Mahadevan, L. C., and Arthur, J. S. (2003) EMBO J. 22, 2788-2797[CrossRef][Medline] [Order article via Infotrieve]
  36. Thomson, S., Mahadevan, L. C., and Clayton A. L. (1999) Semin. Cell Dev. Biol. 10, 205-214[CrossRef][Medline] [Order article via Infotrieve]
  37. Thomson, S., Clayton, A. L., and Mahadevan, L. C. (2001) Mol. Cell. 8, 1231-1241[CrossRef][Medline] [Order article via Infotrieve]
  38. Thiesing, J. T., Ohno-Jones, S., Kolibaba, K. S., and Druker, B. J. (2000) Blood 96, 3195-3199[Abstract/Free Full Text]
  39. Kano, Y., Akutsu, M., Tsunoda, S., Mano, H., Sato, Y., Honma, Y., and Furukawa, Y. (2001) Blood 97, 1999-2007[Abstract/Free Full Text]
  40. Marley, S. B., Davidson, R. J., Goldman, J. M., and Gordon, M. Y. (2002) Br. J. Haematol. 116, 162-165[CrossRef][Medline] [Order article via Infotrieve]
  41. Dan, S., Naito, M., and Tsuruo, T. (1998) Cell Death Differ. 5, 710-715[CrossRef][Medline] [Order article via Infotrieve]
  42. Wolff, N. C., and Ilaria, R. L., Jr. (2001) Blood 98, 2808-2816[Abstract/Free Full Text]
  43. Nishihara, T., Miura, Y., Tohyama, Y., Mizutani, C., Hishita, T., Ichiyama, S., Uchiyama, T., and Tohyama, K. (2003) Int. J. Hematol. 78, 233-240[Medline] [Order article via Infotrieve]
  44. Traina, F., Carvalheira, J. B., Saad, M. J., Costa, F. F., and Saad, S. T. (2003) FEBS Lett. 535, 17-22[CrossRef][Medline] [Order article via Infotrieve]
  45. Kawauchi, K., Ogasawara, T., Yasuyama, M., and Ohkawa, S. (2003) Blood Cells Mol. Dis. 31, 11-17[CrossRef][Medline] [Order article via Infotrieve]
  46. Komatsu, N., Watanabe, T., Uchida, M., Mori, M., Kirito, K., Kikuchi, S., Liu, Q., Tauchi, T., Miyazawa, K., Endo, H., Nagai, T., and Ozawa, K. (2003) J. Biol. Chem. 278, 6411-6419[Abstract/Free Full Text]
  47. Tong, L., Pav, S., White, D. M., Rogers, S., Crane, K. M., Cywin, C. L., Brown, M. L., and Pargellis, C. A. (1997) Nat. Struct. Biol. 4, 311-316[CrossRef][Medline] [Order article via Infotrieve]
  48. Wilson, K. P., McCaffrey, P. G., Hsiao, K., Pazhanisamy, S., Galullo, V., Bemis, G. W., Fitzgibbon, M. J., Caron, P. R., Murcko, M. A., and Su, M. S. (1997) Chem. Biol. 4, 423-431[CrossRef][Medline] [Order article via Infotrieve]
  49. Wang, Z., Canagarajah, B. J., Boehm, J. C., Kassisa, S., Cobb, M. H., Young, P. R., Abdel-Meguid, S., Adams, J. L., and Goldsmith, E. J. (1998) Structure 6, 1117-1128[Medline] [Order article via Infotrieve]
  50. Kumar, S., McDonnell, P. C., Gum, R. J., Hand, A. T., Lee, J. C., and Young, P. R. (1997) Biochem. Biophys. Res. Commun. 235, 533-538[CrossRef][Medline] [Order article via Infotrieve]
  51. Fitzgerald, C. E., Patel, S. B., Becker, J. W., Cameron, P. M., Zaller, D., Pikounis, V. B., O'Keefe, S. J., and Scapin, G. (2003) Nat. Struct. Biol. 10, 764-769[CrossRef][Medline] [Order article via Infotrieve]
  52. Yu, C., Krystal, G., Varticovksi, L., McKinstry, R., Rahmani, M., Dent, P., and Grant, S. (2002) Cancer Res. 62, 188-199[Abstract/Free Full Text]
  53. Platanias, L. C. (2003) Pharmacol. Ther. 98, 129-142[CrossRef][Medline] [Order article via Infotrieve]
  54. Robinson, M. J., and Cobb, M. H. (1997) Curr. Opin. Cell Biol. 9, 180-186[CrossRef][Medline] [Order article via Infotrieve]
  55. Schaeffer, H. J., and Weber, M. J. (1999) Mol. Cell. Biol. 19, 2435-2444[Free Full Text]
  56. Dong, C., Davis, R. J., and Flavell, R. A. (2002) Annu. Rev. Immunol. 20, 55-72[CrossRef][Medline] [Order article via Infotrieve]
  57. Rincon, M., Flavell, R. A., and Davis, R. J. (2001) Oncogene 20, 2490-2497[CrossRef][Medline] [Order article via Infotrieve]
  58. Platanias, L. C. (2003) Blood 101, 4667-4679[Abstract/Free Full Text]
  59. Goh, K. C., Haque, S. J., and Williams, B. R. G. (1999) EMBO J. 18, 5601-5608[CrossRef][Medline] [Order article via Infotrieve]
  60. Kantarjian, H. M., O'Brien, S., Anderlini, P., and Talpaz, M. (1996) Blood 87, 3069-3081[Free Full Text]
  61. Faderl, S., Talpaz, M., Estrov, Z., and Kantarjian, H. M. (1999) Ann. Intern. Med. 131, 207-219[Abstract/Free Full Text]
  62. Shah, N. P., and Sawyers, C. L. (2003) Oncogene 22, 7389-7395[CrossRef][Medline] [Order article via Infotrieve]
  63. von Bubnoff, N., Peschel, C., and Duyster, J. (2003) Leukemia 17, 829-838[CrossRef][Medline] [Order article via Infotrieve]
  64. Holtz, M. S., Slovak, M. L., Zhang, F., Sawyers, C. L., Forman, S. J., and Bhatia, R. (2002) Blood 99, 3792-3800[Abstract/Free Full Text]
  65. Donato, N. J., Wu, J. Y., Stapley, J., Gallick, G., Lin, H., Arlinghaus, R., and Talpaz, M. (2003) Blood. 101, 690-698[Abstract/Free Full Text]
  66. Mahon, F. X., Belloc, F., Lagarde, V., Chollet, C., Moreau-Gaudry, F., Reiffers, J., Goldman, J. M., and Melo, J. V. (2003) Blood 101, 2368-2373[Abstract/Free Full Text]
  67. Andreakos, E. T., Foxwell, B. M., Brennan, F. M., Maini, R. N., and Feldmann, M. (2002) Cytokine Growth Factor Rev. 13, 299-313[CrossRef][Medline] [Order article via Infotrieve]
  68. Pargellis, C., and Regan, J. (2003) Curr. Opin. Investig. Drugs 4, 566-571[Medline] [Order article via Infotrieve]
  69. Newton, R., and Holden, N. (2003) BioDrugs 17, 113-129[CrossRef][Medline] [Order article via Infotrieve]
  70. Kumar, S., Boehm, J., and Lee, J. C. (2003) Nat. Rev. Drug Discov. 2, 717-726[CrossRef][Medline] [Order article via Infotrieve]
  71. Yen, A., Roberson, M. S., Varvayanis, S., and Lee, A. T. (1998) Cancer Res. 58, 3163-3172[Abstract/Free Full Text]
  72. Ebos, J. M., Tran, J., Master, Z., Dumont, D., Melo, J. V., Buchdunger, E., and Kerbel, R. S. (2002) Mol. Cancer Res. 1, 89-95[Abstract/Free Full Text]

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?


This article has been cited by other articles:


Home page
 J. Biol. Chem.Home page
A. J. Redig, A. Sassano, B. Majchrzak-Kita, E. Katsoulidis, H. Liu, J. K. Altman, E. N. Fish, A. Wickrema, and L. C. Platanias
Activation of Protein Kinase C{eta} by Type I Interferons
J. Biol. Chem., April 17, 2009; 284(16): 10301 - 10314.
[Abstract] [Full Text] [PDF]

Home page
 J. Biol. Chem.Home page
E. Katsoulidis, A. Sassano, B. Majchrzak-Kita, N. Carayol, P. Yoon, A. Jordan, B. J. Druker, E. N. Fish, and L. C. Platanias
Suppression of Interferon (IFN)-inducible Genes and IFN-mediated Functional Responses in BCR-ABL-expressing Cells
J. Biol. Chem., April 18, 2008; 283(16): 10793 - 10803.
[Abstract] [Full Text] [PDF]

Home page
 Molecular Cancer TherapeuticsHome page
F. Huguet, N. Giocanti, C. Hennequin, M. Croisy, E. Touboul, and V. Favaudon
Growth inhibition by STI571 in combination with radiation in human chronic myelogenous leukemia K562 cells
Mol. Cancer Ther., February 1, 2008; 7(2): 398 - 406.
[Abstract] [Full Text] [PDF]

Home page
 BloodHome page
T. A. Navas, M. Mohindru, M. Estes, J. Y. Ma, L. Sokol, P. Pahanish, S. Parmar, E. Haghnazari, L. Zhou, R. Collins, et al.
Inhibition of overactivated p38 MAPK can restore hematopoiesis in myelodysplastic syndrome progenitors
Blood, December 15, 2006; 108(13): 4170 - 4177.
[Abstract] [Full Text] [PDF]

Home page
 ASH ANNUAL MEETING ABSTRACTSHome page
M. Mancini, E. Zuffa, P. Corrado, G. Brusa, S. Petta, E. Pagnotta, and M. A. Santucci
Apoptotic Death of Bcr-Abl-Expressing Myeloid Progenitors in Response to the m-Tor Inhibitor RAD001 (Everolimus) Is Promoted by the Nuclear Import of c-Abl.
Blood (ASH Annual Meeting Abstracts), November 1, 2006; 108(11): 2133 - 2133.
[Abstract] [PDF]

Home page
 JEMHome page
M. K. Middleton, A. M. Zukas, T. Rubinstein, M. Jacob, P. Zhu, L. Zhao, I. Blair, and E. Pure
Identification of 12/15-lipoxygenase as a suppressor of myeloproliferative disease
J. Exp. Med., October 30, 2006; 203(11): 2529 - 2540.
[Abstract] [Full Text] [PDF]

Home page
 Mol. Cell. ProteomicsHome page
N. S. Azad, N. Rasool, C. M. Annunziata, L. Minasian, G. Whiteley, and E. C. Kohn
Proteomics in Clinical Trials and Practice: Present Uses and Future Promise
Mol. Cell. Proteomics, October 1, 2006; 5(10): 1819 - 1829.
[Abstract] [Full Text] [PDF]

Home page
 Clin. Cancer Res.Home page
S. V. Sharma, M. A. Fischbach, D. A. Haber, and J. Settleman
"Oncogenic Shock": Explaining Oncogene Addiction through Differential Signal Attenuation.
Clin. Cancer Res., July 15, 2006; 12(14): 4392s - 4395s.
[Abstract] [Full Text] [PDF]

Home page
 BloodHome page
C. Guerzoni, M. Bardini, S. A. Mariani, G. Ferrari-Amorotti, P. Neviani, M. L. Panno, Y. Zhang, R. Martinez, D. Perrotti, and B. Calabretta
Inducible activation of CEBPB, a gene negatively regulated by BCR/ABL, inhibits proliferation and promotes differentiation of BCR/ABL-expressing cells
Blood, May 15, 2006; 107(10): 4080 - 4089.
[Abstract] [Full Text] [PDF]

Home page
 Cancer Res.Home page
E. Katsoulidis, Y. Li, P. Yoon, A. Sassano, J. Altman, P. Kannan-Thulasiraman, L. Balasubramanian, S. Parmar, J. Varga, M. S. Tallman, et al.
Role of the p38 Mitogen-Activated Protein Kinase Pathway in Cytokine-Mediated Hematopoietic Suppression in Myelodysplastic Syndromes
Cancer Res., October 1, 2005; 65(19): 9029 - 9037.
[Abstract] [Full Text] [PDF]

Home page
 BloodHome page
S. Parmar, J. Smith, A. Sassano, S. Uddin, E. Katsoulidis, B. Majchrzak, S. Kambhampati, E. A. Eklund, M. S. Tallman, E. N. Fish, et al.
Differential regulation of the p70 S6 kinase pathway by interferon {alpha} (IFN{alpha}) and imatinib mesylate (STI571) in chronic myelogenous leukemia cells
Blood, October 1, 2005; 106(7): 2436 - 2443.
[Abstract] [Full Text] [PDF]

Home page
 BloodHome page
G. Bandyopadhyay, T. Biswas, K. C. Roy, S. Mandal, C. Mandal, B. C. Pal, S. Bhattacharya, S. Rakshit, D. K. Bhattacharya, U. Chaudhuri, et al.
Chlorogenic acid inhibits Bcr-Abl tyrosine kinase and triggers p38 mitogen-activated protein kinase-dependent apoptosis in chronic myelogenous leukemic cells
Blood, October 15, 2004; 104(8): 2514 - 2522.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
279/24/25345    most recent
M400590200v1
Right arrow Submit a Letter to Editor
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrowRequest Permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Parmar, S.
Right arrow Articles by Platanias, L. C.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Parmar, S.
Right arrow Articles by Platanias, L. C.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
 All ASBMB Journals   Molecular and Cellular Proteomics 
 Journal of Lipid Research   ASBMB Today 
Copyright © 2004 by the American Society for Biochemistry and Molecular Biology.
Advertisement
spacer
Advertisement
Advertisement