The Experts below are selected from a list of 2010 Experts worldwide ranked by ideXlab platform
Jan Cools - One of the best experts on this subject based on the ideXlab platform.
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The fusion proteins TEL-PDGFRβ and FIP1L1-PDGFRα escape ubiquitination and degradation
2020Co-Authors: Jan Cools, Peter Vandenberghe, Lucienne Michaux, Pascal Pierre, Federica Toffalini, Anders Kallin, Jean-baptiste DemoulinAbstract:The online version of this article contains a supplementary appendix. Background Chimeric oncogenes encoding constitutively active protein tyrosine kinases are associated with chronic myeloid neoplasms. TEL-PDGFRβ (TPβ, also called ETV6-PDGFRB) is a hybrid protein produced by the t(5;12) translocation, FIP1L1-PDGFRα (FPα) results from a deletion on chromosome 4q12 and ZNF198-FGFR1 is created by the t(8;13) translocation. These fusion proteins are found in patients with myeloid neoplasms associated with eosinophilia. Wild-type receptor tyrosine kinases are efficiently targeted for degradation upon activation, in a process that requires Cbl-mediated monoubiquitination of receptor lysines. Since protein degradation pathways have been identified as useful targets for cancer therapy, the aim of this study was to compare the degradation of hybrid and wild-type receptor tyrosine kinases. Design and Methods We used Ba/F3 as a model cell line, as well as leukocytes from two patients, to analyze hybrid protein degradation. Results In contrast to the corresponding wild-type receptors, which are quickly degraded upon activation, we observed that TPβ, FPα and the ZNF198-FGFR1 hybrids escaped down-regulation in Ba/F3 cells. The high stability of TPβ and FPα hybrid proteins was confirmed in leukocytes from leukemia patients. Ubiquitination of TPβ and FPα was much reduced compared to that of wild-type receptors, despite marked Cbl phosphorylation in cells expressing hybrid receptors. The fusion of a destabilizing domain to TPβ induced protein degradation. Instability was reverted by adding the destabilizing domain ligand, Shield1. The destabilization of this modified TPβ reduced cell transformation and STAT5 activation. Conclusions We have shown that chimeric receptor tyrosine kinases escape ubiquitination and downregulation and that their stabilization is critical to efficient stimulation of cell proliferation. Key words: PDGF receptor, oncogenes, protein degradation, ubiquitin. Citation: Toffalini F, Kallin A, Vandenberghe P, Pierre P, Michaux L, Cools J, and Demoulin J-B. The fusion proteins TEL-PDGFRβ and FIP1L1-PDGFRα escape ubiquitination and degradation Haematologica 2009;94:1085-1093.doi:10.3324/haematol.2008 This is an open-access paper. The fusion proteins TEL-PDGFRβ and FIP1L1-PDGFRα escape ubiquitination and degradatio
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NEOPLASIA Brief report Sorafenib is a potent inhibitor of FIP1L1-PDGFR and the imatinib-resistant FIP1L1-PDGFRT674I mutant
2016Co-Authors: Els Lierman, Elizabeth H Stover, Cedric Folens, Nicole Mentens, Helen Van Miegroet, Werner Scheers, Marc Boogaerts, Peter Marynen, Jan CoolsAbstract:The FIP1L1-PDGFRA oncogene is a com-mon cause of chronic eosinophilic leukemia (CEL), and encodes an activated tyrosine kinase that is inhibited by imatinib. FIP1L1-PDGFRA–positive patients with CEL re-spond to low-dose imatinib therapy, but resistance due to acquired T674I mutation has been observed. We report here the identification of sorafenib as a potent inhibi-tor of the FIP1 like 1–platelet-derived growth factor receptor alpha (FIP1L1-PDGFR) (T674I) mutant. Sorafenib inhibited the prolif-eration of FIP1L1-PDGFR and FIP1L1-PDGFR(T674I)–transformed Ba/F3 cells and induced apoptosis of the EOL-1 cell line at a low nanomolar concentration. Western blot analysis confirmed that these effects were due to a direct effect on FIP1L1-PDGFR and FIP1L1-PDGFR(T674I). Sorafenib was recently approved for the treatment of renal cell carcinoma. Our data suggest that low doses of sorafenib could be efficient for the treatment of FIP1L1-PDGFRA–positive CEL and could be used to overcome resistance to imatinib associ-ated with the T674I mutation. (Blood. 2006
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recent breakthroughs in the understanding and management of chronic eosinophilic leukemia
Expert Review of Anticancer Therapy, 2009Co-Authors: Els Lierman, Jan CoolsAbstract:The term hypereosinophilic syndrome (HES) was initially introduced to describe a group of diseases all characterized by persistent unexplained hypereosinophilia. Additional names have subsequently been introduced to describe specific variants of HES, such as the myeloid variant and the lymphoid variant, or to indicate idiopathic HES, for which the cause of the eosinophilia is completely unknown. Molecular analysis led to the identification of the clonal origin of several subgroups of HES, clearly establishing these diseases as true leukemias. These cases of hypereosinophilia are now referred to as 'myeloid neoplasms associated with eosinophilia and abnormalities of PDGF receptor A and B (PDGFRA and PDGFRB), or FGF receptor 1 (FGFR1)'. In cases for which clonality is clear, but no PDGFRA, PDGFRB or FGFR1 rearrangement could be demonstrated, the term 'chronic eosinophilic leukemia, not otherwise specified' is preferred. Most importantly, patients with rearrangements of PDGFRA or PDGFRB can be efficiently treated with the kinase inhibitor imatinib. Additional potent kinase inhibitors have been identified, also including inhibitors that target FGFR1 and imatinib-resistant variants of PDGFRalpha. For treatment of unexplained hypereosinophilia and 'chronic eosinophilic leukemia, not otherwise specified; different therapeutic strategies are currently under investigation and promising results have been obtained using humanized anti-IL-5 antibodies. Further molecular understanding of the cause of these 'idiopathic' diseases may lead to the development of novel targeted therapies.
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fip1l1 pdgfr alpha d842v a novel panresistant mutant emerging after treatment of fip1l1 pdgfr alpha t674i eosinophilic leukemia with single agent sorafenib
Leukemia, 2009Co-Authors: Els Beullens, Jan Cools, Els Lierman, Peter Marynen, Lucienne Michaux, Pascal Pierre, Peter VandenbergheAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions or other genetic lesions. Most FIP1L1–PDGFRA positive patients enjoy durable and complete molecular responses to low-dose imatinib (Glivec/Gleevec). However, resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease, and sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, is active against this mutant in vitro. We describe a case of FIP1L1-PDGFRα T674I CEL in blast crisis that responded to sorafenib (Nexavar). However, this clinical response was short-lived because of the rapid emergence of a FIP1L1-PDGFRα D842V mutant. An N-Nitroso-N-ethylurea-mutagenesis screen indeed identified this mutant as a major sorafenib-resistant mutant. In vitro, the novel FIP1L1-PDGFRα D842V mutant is highly resistant to sorafenib, imatinib, dasatinib (Sprycell) and PKC412 (Midostaurin). Thus, sorafenib is clinically active in imatinib-resistant FIP1L1-PDGFRα T674I CEL, but the rapid emergence of other mutants may limit the response duration. The identification of new PDGFR inhibitors will be required to overcome resistance by this D842V mutant.
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FIP1L1-PDGFRα D842V, a novel panresistant mutant, emerging after treatment of FIP1L1-PDGFRα T674I eosinophilic leukemia with single agent sorafenib
Leukemia, 2009Co-Authors: Els Lierman, Jan Cools, Peter Marynen, Lucienne Michaux, Pascal Pierre, Els Beullens, J Cools, Peter VandenbergheAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions or other genetic lesions. Most FIP1L1–PDGFRA positive patients enjoy durable and complete molecular responses to low-dose imatinib (Glivec/Gleevec). However, resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease, and sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, is active against this mutant in vitro. We describe a case of FIP1L1-PDGFRα T674I CEL in blast crisis that responded to sorafenib (Nexavar). However, this clinical response was short-lived because of the rapid emergence of a FIP1L1-PDGFRα D842V mutant. An N -Nitroso- N -ethylurea-mutagenesis screen indeed identified this mutant as a major sorafenib-resistant mutant. In vitro, the novel FIP1L1-PDGFRα D842V mutant is highly resistant to sorafenib, imatinib, dasatinib (Sprycell) and PKC412 (Midostaurin). Thus, sorafenib is clinically active in imatinib-resistant FIP1L1-PDGFRα T674I CEL, but the rapid emergence of other mutants may limit the response duration. The identification of new PDGFR inhibitors will be required to overcome resistance by this D842V mutant.
Hongbing Zhang - One of the best experts on this subject based on the ideXlab platform.
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abstract 3551 a microrna 1280 jag2 network comprises a novel biological target in high risk medulloblastoma
Cancer Research, 2015Co-Authors: Fengfei Wang, Kruttika Bhat, Saeed Salem, Adrian M Dubuc, Marc Remke, Ekokobe Fonkem, Vijay Ramaswamy, Eric T Wong, Shuang Zhou, Hongbing ZhangAbstract:Over-expression of PDGF receptors (PDGFRs) has been previously implicated in high-risk medulloblastoma (MB) pathogenesis. However, the exact biological functions of PDGFRα and PDGFRβ signaling in MB biology remain poorly understood. Here, we report the subgroup specific expression of PDGFRα and PDGFRβ and their associated biological pathways in MB tumors. c-MYC, a downstream target of PDGFRβ but not PDGFRα, is involved in PDGFRβ signaling associated with cell proliferation, cell death, and invasion. Concurrent inhibition of PDGFRβ and c-MYC blocks MB cell proliferation and migration synergistically. Integrated analysis of miRNA and miRNA targets regulated by both PDGFRβ and c-MYC reveals that increased expression of JAG2, a target of miR-1280, is associated with high metastatic dissemination at diagnosis and a poor outcome in MB patients. Our study may resolve the controversy on the role of PDGFRs in MB and unveils JAG2 as a key downstream effector of a PDGFRβ-driven signaling cascade and a potential therapeutic target. Citation Format: Fengfei Wang, Marc Remke, Kruttika Bhat, Eric Wong, Shuang Zhou, Vijay Ramaswamy, Adrian Dubuc, Ekokobe Fonkem, Saeed Salem, Hongbing Zhang, Tze-chen Hsieh, Stephen O9Rourke, Lizi Wu, David Li, Cynthia Hawkins, Isaac Kohane, Joseph Wu, Min Wu, Michael Taylor, Erxi Wu. A microRNA-1280/JAG2 network comprises a novel biological target in high-risk medulloblastoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3551. doi:10.1158/1538-7445.AM2015-3551
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a microrna 1280 jag2 network comprises a novel biological target in high risk medulloblastoma
Oncotarget, 2015Co-Authors: Fengfei Wang, Kruttika Bhat, Saeed Salem, Adrian M Dubuc, Marc Remke, Ekokobe Fonkem, Vijay Ramaswamy, Eric T Wong, Shuang Zhou, Hongbing ZhangAbstract:Over-expression of PDGF receptors (PDGFRs) has been previously implicated in high-risk medulloblastoma (MB) pathogenesis. However, the exact biological functions of PDGFRα and PDGFRβ signaling in MB biology remain poorly understood. Here, we report the subgroup specific expression of PDGFRα and PDGFRβ and their associated biological pathways in MB tumors. c-MYC, a downstream target of PDGFRβ but not PDGFRα, is involved in PDGFRβ signaling associated with cell proliferation, cell death, and invasion. Concurrent inhibition of PDGFRβ and c-MYC blocks MB cell proliferation and migration synergistically. Integrated analysis of miRNA and miRNA targets regulated by both PDGFRβ and c-MYC reveals that increased expression of JAG2, a target of miR-1280, is associated with high metastatic dissemination at diagnosis and a poor outcome in MB patients. Our study may resolve the controversy on the role of PDGFRs in MB and unveils JAG2 as a key downstream effector of a PDGFRβ-driven signaling cascade and a potential therapeutic target.
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loss of tsc1 tsc2 activates mtor and disrupts pi3k akt signaling through downregulation of pdgfr
Journal of Clinical Investigation, 2003Co-Authors: Hongbing Zhang, Gregor Cicchetti, Kirsten Asrican, Natalia Bajraszewski, Henry B. Koon, Francisca Vazquez, Christopher L. Carpenter, Hiroaki Onda, David J KwiatkowskiAbstract:Tuberous sclerosis (TSC) is a familial tumor syndrome due to mutations in TSC1 or TSC2, in which progression to malignancy is rare. Primary Tsc2–/– murine embryo fibroblast cultures display early senescence with overexpression of p21CIP1/WAF1 that is rescued by loss of TP53. Tsc2–/–TP53–/– cells, as well as tumors from Tsc2+/– mice, display an mTOR-activation signature with constitutive activation of S6K, which is reverted by treatment with rapamycin. Rapamycin also reverts a growth advantage of Tsc2–/–TP53–/– cells. Tsc1/Tsc2 does not bind directly to mTOR, however, nor does it directly influence mTOR kinase activity or cellular phosphatase activity. There is a marked reduction in Akt activation in Tsc2–/–TP53–/– and Tsc1–/– cells in response to serum and PDGF, along with a reduction in cell ruffling. PDGFRα and PDGFRβ expression is markedly reduced in both the cell lines and Tsc mouse renal cystadenomas, and ectopic expression of PDGFRβ in Tsc2-null cells restores Akt phosphorylation in response to serum, PDGF, EGF, and insulin. This activation of mTOR along with downregulation of PDGFR PI3K-Akt signaling in cells lacking Tsc1 or Tsc2 may explain why these genes are rarely involved in human cancer. This is in contrast to PTEN, which is a negative upstream regulator of this pathway.
Peter Marynen - One of the best experts on this subject based on the ideXlab platform.
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NEOPLASIA Brief report Sorafenib is a potent inhibitor of FIP1L1-PDGFR and the imatinib-resistant FIP1L1-PDGFRT674I mutant
2016Co-Authors: Els Lierman, Elizabeth H Stover, Cedric Folens, Nicole Mentens, Helen Van Miegroet, Werner Scheers, Marc Boogaerts, Peter Marynen, Jan CoolsAbstract:The FIP1L1-PDGFRA oncogene is a com-mon cause of chronic eosinophilic leukemia (CEL), and encodes an activated tyrosine kinase that is inhibited by imatinib. FIP1L1-PDGFRA–positive patients with CEL re-spond to low-dose imatinib therapy, but resistance due to acquired T674I mutation has been observed. We report here the identification of sorafenib as a potent inhibi-tor of the FIP1 like 1–platelet-derived growth factor receptor alpha (FIP1L1-PDGFR) (T674I) mutant. Sorafenib inhibited the prolif-eration of FIP1L1-PDGFR and FIP1L1-PDGFR(T674I)–transformed Ba/F3 cells and induced apoptosis of the EOL-1 cell line at a low nanomolar concentration. Western blot analysis confirmed that these effects were due to a direct effect on FIP1L1-PDGFR and FIP1L1-PDGFR(T674I). Sorafenib was recently approved for the treatment of renal cell carcinoma. Our data suggest that low doses of sorafenib could be efficient for the treatment of FIP1L1-PDGFRA–positive CEL and could be used to overcome resistance to imatinib associ-ated with the T674I mutation. (Blood. 2006
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fip1l1 pdgfr alpha d842v a novel panresistant mutant emerging after treatment of fip1l1 pdgfr alpha t674i eosinophilic leukemia with single agent sorafenib
Leukemia, 2009Co-Authors: Els Beullens, Jan Cools, Els Lierman, Peter Marynen, Lucienne Michaux, Pascal Pierre, Peter VandenbergheAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions or other genetic lesions. Most FIP1L1–PDGFRA positive patients enjoy durable and complete molecular responses to low-dose imatinib (Glivec/Gleevec). However, resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease, and sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, is active against this mutant in vitro. We describe a case of FIP1L1-PDGFRα T674I CEL in blast crisis that responded to sorafenib (Nexavar). However, this clinical response was short-lived because of the rapid emergence of a FIP1L1-PDGFRα D842V mutant. An N-Nitroso-N-ethylurea-mutagenesis screen indeed identified this mutant as a major sorafenib-resistant mutant. In vitro, the novel FIP1L1-PDGFRα D842V mutant is highly resistant to sorafenib, imatinib, dasatinib (Sprycell) and PKC412 (Midostaurin). Thus, sorafenib is clinically active in imatinib-resistant FIP1L1-PDGFRα T674I CEL, but the rapid emergence of other mutants may limit the response duration. The identification of new PDGFR inhibitors will be required to overcome resistance by this D842V mutant.
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FIP1L1-PDGFRα D842V, a novel panresistant mutant, emerging after treatment of FIP1L1-PDGFRα T674I eosinophilic leukemia with single agent sorafenib
Leukemia, 2009Co-Authors: Els Lierman, Jan Cools, Peter Marynen, Lucienne Michaux, Pascal Pierre, Els Beullens, J Cools, Peter VandenbergheAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions or other genetic lesions. Most FIP1L1–PDGFRA positive patients enjoy durable and complete molecular responses to low-dose imatinib (Glivec/Gleevec). However, resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease, and sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, is active against this mutant in vitro. We describe a case of FIP1L1-PDGFRα T674I CEL in blast crisis that responded to sorafenib (Nexavar). However, this clinical response was short-lived because of the rapid emergence of a FIP1L1-PDGFRα D842V mutant. An N -Nitroso- N -ethylurea-mutagenesis screen indeed identified this mutant as a major sorafenib-resistant mutant. In vitro, the novel FIP1L1-PDGFRα D842V mutant is highly resistant to sorafenib, imatinib, dasatinib (Sprycell) and PKC412 (Midostaurin). Thus, sorafenib is clinically active in imatinib-resistant FIP1L1-PDGFRα T674I CEL, but the rapid emergence of other mutants may limit the response duration. The identification of new PDGFR inhibitors will be required to overcome resistance by this D842V mutant.
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FIP1L1-PDGFRα D842V, a Novel Panresistant Mutant, Emerges after Treatment of FIP1L1-PDGFRα T674I Eosinophilic Leukemia with Single Agent Sorafenib
Blood, 2008Co-Authors: Peter Vandenberghe, Els Lierman, Peter Marynen, Lucienne Michaux, Pascal Pierre, Jan CoolsAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions, or other genetic lesions. Most FIP1L1-PDGFRA positive patients enjoy durable complete molecular responses to low-dose imatinib, but resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease. Sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, has been shown to be active against this mutant in vitro. We explored a case of FIP1L1-PDGFRα T674I CEL in blast crisis that was treated with sorafenib as single agent. A partial hematological response was induced, but three months later, progression to blast crisis again occurred. At this time point, sequencing of FIP1L1-PDGFRA revealed the presence of a novel FIP1L1-PDGFRα D842V mutant, while FIP1L1-PDGFRα T674I was no longer detected. The sensitivity of this mutant to different inhibitors was further explored using FIP1L1-PDGFRα D842V transformed Ba/F3 cells. The growth of FIP1L1-PDGFRα D842V transformed Ba/F3 cells was highly resistant to sorafenib and PKC412, in addition to imatinib and dasatinib (IC 50 ≥ 1000 nM for imatinib, sorafenib and dasatinib; IC 50 of PKC412 not reached due to toxicity above 500 nM). Consistent with these dose response curves, FIP1L1-PDGFRα D842V cells did not undergo apoptosis when cultured in 500 nM sorafenib, imatinib or dasatinib, while 30% of FIP1L1-PDGFRα cells did under the same conditions. Analysis of FIP1L1-PDGFRα autophosphorylation and phosphorylation of the downstream signaling proteins ERK1 and ERK2 confirmed that the D842V mutant protein was not inhibited by sorafenib, imatinib or dasatinib at concentrations up to 1000 nM, in contrast to FIP1L1-PDGFRα itself or the T674I mutant. Intriguingly, FIP1L1-PDGFRα D842V cells are significantly less sensitive to dasatinib than PDGFRα D842V expressing cells. Finally, an ENU-mutagenesis screen indeed identified this mutant as a major sorafenib resistant mutant. In summary, this case represents the fifth reported case of acquired resistance to imatinib in FIP1L1-PDGFRA positive CEL. Our data illustrate the efficacy of sorafenib against FIP1L1-PDGFRα T674I as a single agent in vivo . Yet, selection of secondary sorafenib resistant clones is likely to occur, as has also been observed in imatinib resistant CML treated with second line tyrosine kinase inhibitors. While FIP1L1-PDGFRα D842V is a novel panresistant mutation in CEL, the PDGFRα D842V mutation is a known activating mutation of PDGFRα and causes primary imatinib resistance in a small percentage of gastro-intestinal stromal tumors. The homologous KIT D816V mutation in systemic mastocytosis is also associated with imatinib resistance. Of note, the latter two mutations respond better to dasatinib than FIP1L1-PDGFRα D842V. Our observation highlights the difficult challenge of treating resistant mutations and provides a basis for further proactive development of inhibitors with activity against sorafenib resistance mutants.
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activity of imatinib in systemic mastocytosis with chronic basophilic leukemia and a prkg2 PDGFRB fusion
Haematologica, 2008Co-Authors: Idoya Lahortiga, Jan Cools, Nicole Mentens, Cem Akin, Todd M Wilson, Diane C Arthur, Irina Maric, Pierre Noel, Can N Kocabas, Peter MarynenAbstract:Background Translocations involving region 5q31-32 ( PDGFRB ) have been reported in a variety of myeloproliferative diseases and are often associated with significant peripheral eosinophilia. We report an unusual case of a patient presenting with peripheral basophilia and systemic mastocytosis in whom cytogenetic analysis revealed a t(4;5)(q21.1;q31.3). Design and Methods We used molecular analyses to determine the role of PDGFRB in this case. The patient was treated with imatinib. Results Fluorescence in situ hybridization (FISH) documented a breakpoint in PDGFRB . In agreement with this, the patient responded very well to imatinib with resolution of clinical symptoms, basophilia, and mast cell disease. Molecular analyses revealed that PDGFRB , encoding an imatinib-sensitive tyrosine kinase, was fused to PRKG2 . The fusion gene incorporates the first two exons of PRKG2 fused to the truncated exon 12 of PDGFRB , resulting in the disruption of its juxtamembrane domain. Functional studies confirmed that the activity and transforming properties of PRKG2-PDGFRβ were dependent on the disruption of the auto-inhibitory juxtamembrane domain. Conclusions Our results identify a second case of the PRKG2-PDGFRB fusion and confirm the unusual PDGFRB breakpoint associated with this fusion. This work also illustrates the use of imatinib for the treatment of specific cases of systemic mastocytosis.
Peter Vandenberghe - One of the best experts on this subject based on the ideXlab platform.
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The fusion proteins TEL-PDGFRβ and FIP1L1-PDGFRα escape ubiquitination and degradation
2020Co-Authors: Jan Cools, Peter Vandenberghe, Lucienne Michaux, Pascal Pierre, Federica Toffalini, Anders Kallin, Jean-baptiste DemoulinAbstract:The online version of this article contains a supplementary appendix. Background Chimeric oncogenes encoding constitutively active protein tyrosine kinases are associated with chronic myeloid neoplasms. TEL-PDGFRβ (TPβ, also called ETV6-PDGFRB) is a hybrid protein produced by the t(5;12) translocation, FIP1L1-PDGFRα (FPα) results from a deletion on chromosome 4q12 and ZNF198-FGFR1 is created by the t(8;13) translocation. These fusion proteins are found in patients with myeloid neoplasms associated with eosinophilia. Wild-type receptor tyrosine kinases are efficiently targeted for degradation upon activation, in a process that requires Cbl-mediated monoubiquitination of receptor lysines. Since protein degradation pathways have been identified as useful targets for cancer therapy, the aim of this study was to compare the degradation of hybrid and wild-type receptor tyrosine kinases. Design and Methods We used Ba/F3 as a model cell line, as well as leukocytes from two patients, to analyze hybrid protein degradation. Results In contrast to the corresponding wild-type receptors, which are quickly degraded upon activation, we observed that TPβ, FPα and the ZNF198-FGFR1 hybrids escaped down-regulation in Ba/F3 cells. The high stability of TPβ and FPα hybrid proteins was confirmed in leukocytes from leukemia patients. Ubiquitination of TPβ and FPα was much reduced compared to that of wild-type receptors, despite marked Cbl phosphorylation in cells expressing hybrid receptors. The fusion of a destabilizing domain to TPβ induced protein degradation. Instability was reverted by adding the destabilizing domain ligand, Shield1. The destabilization of this modified TPβ reduced cell transformation and STAT5 activation. Conclusions We have shown that chimeric receptor tyrosine kinases escape ubiquitination and downregulation and that their stabilization is critical to efficient stimulation of cell proliferation. Key words: PDGF receptor, oncogenes, protein degradation, ubiquitin. Citation: Toffalini F, Kallin A, Vandenberghe P, Pierre P, Michaux L, Cools J, and Demoulin J-B. The fusion proteins TEL-PDGFRβ and FIP1L1-PDGFRα escape ubiquitination and degradation Haematologica 2009;94:1085-1093.doi:10.3324/haematol.2008 This is an open-access paper. The fusion proteins TEL-PDGFRβ and FIP1L1-PDGFRα escape ubiquitination and degradatio
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fip1l1 pdgfr alpha d842v a novel panresistant mutant emerging after treatment of fip1l1 pdgfr alpha t674i eosinophilic leukemia with single agent sorafenib
Leukemia, 2009Co-Authors: Els Beullens, Jan Cools, Els Lierman, Peter Marynen, Lucienne Michaux, Pascal Pierre, Peter VandenbergheAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions or other genetic lesions. Most FIP1L1–PDGFRA positive patients enjoy durable and complete molecular responses to low-dose imatinib (Glivec/Gleevec). However, resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease, and sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, is active against this mutant in vitro. We describe a case of FIP1L1-PDGFRα T674I CEL in blast crisis that responded to sorafenib (Nexavar). However, this clinical response was short-lived because of the rapid emergence of a FIP1L1-PDGFRα D842V mutant. An N-Nitroso-N-ethylurea-mutagenesis screen indeed identified this mutant as a major sorafenib-resistant mutant. In vitro, the novel FIP1L1-PDGFRα D842V mutant is highly resistant to sorafenib, imatinib, dasatinib (Sprycell) and PKC412 (Midostaurin). Thus, sorafenib is clinically active in imatinib-resistant FIP1L1-PDGFRα T674I CEL, but the rapid emergence of other mutants may limit the response duration. The identification of new PDGFR inhibitors will be required to overcome resistance by this D842V mutant.
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FIP1L1-PDGFRα D842V, a novel panresistant mutant, emerging after treatment of FIP1L1-PDGFRα T674I eosinophilic leukemia with single agent sorafenib
Leukemia, 2009Co-Authors: Els Lierman, Jan Cools, Peter Marynen, Lucienne Michaux, Pascal Pierre, Els Beullens, J Cools, Peter VandenbergheAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions or other genetic lesions. Most FIP1L1–PDGFRA positive patients enjoy durable and complete molecular responses to low-dose imatinib (Glivec/Gleevec). However, resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease, and sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, is active against this mutant in vitro. We describe a case of FIP1L1-PDGFRα T674I CEL in blast crisis that responded to sorafenib (Nexavar). However, this clinical response was short-lived because of the rapid emergence of a FIP1L1-PDGFRα D842V mutant. An N -Nitroso- N -ethylurea-mutagenesis screen indeed identified this mutant as a major sorafenib-resistant mutant. In vitro, the novel FIP1L1-PDGFRα D842V mutant is highly resistant to sorafenib, imatinib, dasatinib (Sprycell) and PKC412 (Midostaurin). Thus, sorafenib is clinically active in imatinib-resistant FIP1L1-PDGFRα T674I CEL, but the rapid emergence of other mutants may limit the response duration. The identification of new PDGFR inhibitors will be required to overcome resistance by this D842V mutant.
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FIP1L1-PDGFRα D842V, a Novel Panresistant Mutant, Emerges after Treatment of FIP1L1-PDGFRα T674I Eosinophilic Leukemia with Single Agent Sorafenib
Blood, 2008Co-Authors: Peter Vandenberghe, Els Lierman, Peter Marynen, Lucienne Michaux, Pascal Pierre, Jan CoolsAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions, or other genetic lesions. Most FIP1L1-PDGFRA positive patients enjoy durable complete molecular responses to low-dose imatinib, but resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease. Sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, has been shown to be active against this mutant in vitro. We explored a case of FIP1L1-PDGFRα T674I CEL in blast crisis that was treated with sorafenib as single agent. A partial hematological response was induced, but three months later, progression to blast crisis again occurred. At this time point, sequencing of FIP1L1-PDGFRA revealed the presence of a novel FIP1L1-PDGFRα D842V mutant, while FIP1L1-PDGFRα T674I was no longer detected. The sensitivity of this mutant to different inhibitors was further explored using FIP1L1-PDGFRα D842V transformed Ba/F3 cells. The growth of FIP1L1-PDGFRα D842V transformed Ba/F3 cells was highly resistant to sorafenib and PKC412, in addition to imatinib and dasatinib (IC 50 ≥ 1000 nM for imatinib, sorafenib and dasatinib; IC 50 of PKC412 not reached due to toxicity above 500 nM). Consistent with these dose response curves, FIP1L1-PDGFRα D842V cells did not undergo apoptosis when cultured in 500 nM sorafenib, imatinib or dasatinib, while 30% of FIP1L1-PDGFRα cells did under the same conditions. Analysis of FIP1L1-PDGFRα autophosphorylation and phosphorylation of the downstream signaling proteins ERK1 and ERK2 confirmed that the D842V mutant protein was not inhibited by sorafenib, imatinib or dasatinib at concentrations up to 1000 nM, in contrast to FIP1L1-PDGFRα itself or the T674I mutant. Intriguingly, FIP1L1-PDGFRα D842V cells are significantly less sensitive to dasatinib than PDGFRα D842V expressing cells. Finally, an ENU-mutagenesis screen indeed identified this mutant as a major sorafenib resistant mutant. In summary, this case represents the fifth reported case of acquired resistance to imatinib in FIP1L1-PDGFRA positive CEL. Our data illustrate the efficacy of sorafenib against FIP1L1-PDGFRα T674I as a single agent in vivo . Yet, selection of secondary sorafenib resistant clones is likely to occur, as has also been observed in imatinib resistant CML treated with second line tyrosine kinase inhibitors. While FIP1L1-PDGFRα D842V is a novel panresistant mutation in CEL, the PDGFRα D842V mutation is a known activating mutation of PDGFRα and causes primary imatinib resistance in a small percentage of gastro-intestinal stromal tumors. The homologous KIT D816V mutation in systemic mastocytosis is also associated with imatinib resistance. Of note, the latter two mutations respond better to dasatinib than FIP1L1-PDGFRα D842V. Our observation highlights the difficult challenge of treating resistant mutations and provides a basis for further proactive development of inhibitors with activity against sorafenib resistance mutants.
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Sorafenib is a potent inhibitor of FIP1L1-PDGFRα and the imatinib-resistant FIP1L1-PDGFRα T674I mutant
Blood, 2006Co-Authors: Els Lierman, Elizabeth H Stover, Cedric Folens, Nicole Mentens, Helen Van Miegroet, Werner Scheers, Marc Boogaerts, Peter Vandenberghe, Peter Marynen, Jan CoolsAbstract:The FIP1L1-PDGFRA oncogene is a common cause of chronic eosinophilic leukemia (CEL), and encodes an activated tyrosine kinase that is inhibited by imatinib. FIP1L1-PDGFRA–positive patients with CEL respond to low-dose imatinib therapy, but resistance due to acquired T674I mutation has been observed. We report here the identification of sorafenib as a potent inhibitor of the FIP1 like 1–platelet-derived growth factor receptor alpha (FIP1L1-PDGFRα) (T674I) mutant. Sorafenib inhibited the proliferation of FIP1L1-PDGFRα and FIP1L1-PDGFRα(T674I)–transformed Ba/F3 cells and induced apoptosis of the EOL-1 cell line at a low nanomolar concentration. Western blot analysis confirmed that these effects were due to a direct effect on FIP1L1-PDGFRα and FIP1L1-PDGFRα(T674I). Sorafenib was recently approved for the treatment of renal cell carcinoma. Our data suggest that low doses of sorafenib could be efficient for the treatment of FIP1L1-PDGFRA–positive CEL and could be used to overcome resistance to imatinib associated with the T674I mutation.
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NEOPLASIA Brief report Sorafenib is a potent inhibitor of FIP1L1-PDGFR and the imatinib-resistant FIP1L1-PDGFRT674I mutant
2016Co-Authors: Els Lierman, Elizabeth H Stover, Cedric Folens, Nicole Mentens, Helen Van Miegroet, Werner Scheers, Marc Boogaerts, Peter Marynen, Jan CoolsAbstract:The FIP1L1-PDGFRA oncogene is a com-mon cause of chronic eosinophilic leukemia (CEL), and encodes an activated tyrosine kinase that is inhibited by imatinib. FIP1L1-PDGFRA–positive patients with CEL re-spond to low-dose imatinib therapy, but resistance due to acquired T674I mutation has been observed. We report here the identification of sorafenib as a potent inhibi-tor of the FIP1 like 1–platelet-derived growth factor receptor alpha (FIP1L1-PDGFR) (T674I) mutant. Sorafenib inhibited the prolif-eration of FIP1L1-PDGFR and FIP1L1-PDGFR(T674I)–transformed Ba/F3 cells and induced apoptosis of the EOL-1 cell line at a low nanomolar concentration. Western blot analysis confirmed that these effects were due to a direct effect on FIP1L1-PDGFR and FIP1L1-PDGFR(T674I). Sorafenib was recently approved for the treatment of renal cell carcinoma. Our data suggest that low doses of sorafenib could be efficient for the treatment of FIP1L1-PDGFRA–positive CEL and could be used to overcome resistance to imatinib associ-ated with the T674I mutation. (Blood. 2006
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recent breakthroughs in the understanding and management of chronic eosinophilic leukemia
Expert Review of Anticancer Therapy, 2009Co-Authors: Els Lierman, Jan CoolsAbstract:The term hypereosinophilic syndrome (HES) was initially introduced to describe a group of diseases all characterized by persistent unexplained hypereosinophilia. Additional names have subsequently been introduced to describe specific variants of HES, such as the myeloid variant and the lymphoid variant, or to indicate idiopathic HES, for which the cause of the eosinophilia is completely unknown. Molecular analysis led to the identification of the clonal origin of several subgroups of HES, clearly establishing these diseases as true leukemias. These cases of hypereosinophilia are now referred to as 'myeloid neoplasms associated with eosinophilia and abnormalities of PDGF receptor A and B (PDGFRA and PDGFRB), or FGF receptor 1 (FGFR1)'. In cases for which clonality is clear, but no PDGFRA, PDGFRB or FGFR1 rearrangement could be demonstrated, the term 'chronic eosinophilic leukemia, not otherwise specified' is preferred. Most importantly, patients with rearrangements of PDGFRA or PDGFRB can be efficiently treated with the kinase inhibitor imatinib. Additional potent kinase inhibitors have been identified, also including inhibitors that target FGFR1 and imatinib-resistant variants of PDGFRalpha. For treatment of unexplained hypereosinophilia and 'chronic eosinophilic leukemia, not otherwise specified; different therapeutic strategies are currently under investigation and promising results have been obtained using humanized anti-IL-5 antibodies. Further molecular understanding of the cause of these 'idiopathic' diseases may lead to the development of novel targeted therapies.
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fip1l1 pdgfr alpha d842v a novel panresistant mutant emerging after treatment of fip1l1 pdgfr alpha t674i eosinophilic leukemia with single agent sorafenib
Leukemia, 2009Co-Authors: Els Beullens, Jan Cools, Els Lierman, Peter Marynen, Lucienne Michaux, Pascal Pierre, Peter VandenbergheAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions or other genetic lesions. Most FIP1L1–PDGFRA positive patients enjoy durable and complete molecular responses to low-dose imatinib (Glivec/Gleevec). However, resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease, and sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, is active against this mutant in vitro. We describe a case of FIP1L1-PDGFRα T674I CEL in blast crisis that responded to sorafenib (Nexavar). However, this clinical response was short-lived because of the rapid emergence of a FIP1L1-PDGFRα D842V mutant. An N-Nitroso-N-ethylurea-mutagenesis screen indeed identified this mutant as a major sorafenib-resistant mutant. In vitro, the novel FIP1L1-PDGFRα D842V mutant is highly resistant to sorafenib, imatinib, dasatinib (Sprycell) and PKC412 (Midostaurin). Thus, sorafenib is clinically active in imatinib-resistant FIP1L1-PDGFRα T674I CEL, but the rapid emergence of other mutants may limit the response duration. The identification of new PDGFR inhibitors will be required to overcome resistance by this D842V mutant.
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FIP1L1-PDGFRα D842V, a novel panresistant mutant, emerging after treatment of FIP1L1-PDGFRα T674I eosinophilic leukemia with single agent sorafenib
Leukemia, 2009Co-Authors: Els Lierman, Jan Cools, Peter Marynen, Lucienne Michaux, Pascal Pierre, Els Beullens, J Cools, Peter VandenbergheAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions or other genetic lesions. Most FIP1L1–PDGFRA positive patients enjoy durable and complete molecular responses to low-dose imatinib (Glivec/Gleevec). However, resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease, and sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, is active against this mutant in vitro. We describe a case of FIP1L1-PDGFRα T674I CEL in blast crisis that responded to sorafenib (Nexavar). However, this clinical response was short-lived because of the rapid emergence of a FIP1L1-PDGFRα D842V mutant. An N -Nitroso- N -ethylurea-mutagenesis screen indeed identified this mutant as a major sorafenib-resistant mutant. In vitro, the novel FIP1L1-PDGFRα D842V mutant is highly resistant to sorafenib, imatinib, dasatinib (Sprycell) and PKC412 (Midostaurin). Thus, sorafenib is clinically active in imatinib-resistant FIP1L1-PDGFRα T674I CEL, but the rapid emergence of other mutants may limit the response duration. The identification of new PDGFR inhibitors will be required to overcome resistance by this D842V mutant.
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FIP1L1-PDGFRα D842V, a Novel Panresistant Mutant, Emerges after Treatment of FIP1L1-PDGFRα T674I Eosinophilic Leukemia with Single Agent Sorafenib
Blood, 2008Co-Authors: Peter Vandenberghe, Els Lierman, Peter Marynen, Lucienne Michaux, Pascal Pierre, Jan CoolsAbstract:Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions, or other genetic lesions. Most FIP1L1-PDGFRA positive patients enjoy durable complete molecular responses to low-dose imatinib, but resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease. Sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, has been shown to be active against this mutant in vitro. We explored a case of FIP1L1-PDGFRα T674I CEL in blast crisis that was treated with sorafenib as single agent. A partial hematological response was induced, but three months later, progression to blast crisis again occurred. At this time point, sequencing of FIP1L1-PDGFRA revealed the presence of a novel FIP1L1-PDGFRα D842V mutant, while FIP1L1-PDGFRα T674I was no longer detected. The sensitivity of this mutant to different inhibitors was further explored using FIP1L1-PDGFRα D842V transformed Ba/F3 cells. The growth of FIP1L1-PDGFRα D842V transformed Ba/F3 cells was highly resistant to sorafenib and PKC412, in addition to imatinib and dasatinib (IC 50 ≥ 1000 nM for imatinib, sorafenib and dasatinib; IC 50 of PKC412 not reached due to toxicity above 500 nM). Consistent with these dose response curves, FIP1L1-PDGFRα D842V cells did not undergo apoptosis when cultured in 500 nM sorafenib, imatinib or dasatinib, while 30% of FIP1L1-PDGFRα cells did under the same conditions. Analysis of FIP1L1-PDGFRα autophosphorylation and phosphorylation of the downstream signaling proteins ERK1 and ERK2 confirmed that the D842V mutant protein was not inhibited by sorafenib, imatinib or dasatinib at concentrations up to 1000 nM, in contrast to FIP1L1-PDGFRα itself or the T674I mutant. Intriguingly, FIP1L1-PDGFRα D842V cells are significantly less sensitive to dasatinib than PDGFRα D842V expressing cells. Finally, an ENU-mutagenesis screen indeed identified this mutant as a major sorafenib resistant mutant. In summary, this case represents the fifth reported case of acquired resistance to imatinib in FIP1L1-PDGFRA positive CEL. Our data illustrate the efficacy of sorafenib against FIP1L1-PDGFRα T674I as a single agent in vivo . Yet, selection of secondary sorafenib resistant clones is likely to occur, as has also been observed in imatinib resistant CML treated with second line tyrosine kinase inhibitors. While FIP1L1-PDGFRα D842V is a novel panresistant mutation in CEL, the PDGFRα D842V mutation is a known activating mutation of PDGFRα and causes primary imatinib resistance in a small percentage of gastro-intestinal stromal tumors. The homologous KIT D816V mutation in systemic mastocytosis is also associated with imatinib resistance. Of note, the latter two mutations respond better to dasatinib than FIP1L1-PDGFRα D842V. Our observation highlights the difficult challenge of treating resistant mutations and provides a basis for further proactive development of inhibitors with activity against sorafenib resistance mutants.