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Jonathan A. Fletcher

Bio: Jonathan A. Fletcher is an academic researcher from Brigham and Women's Hospital. The author has contributed to research in topics: GiST & PDGFRA. The author has an hindex of 109, co-authored 413 publications receiving 53642 citations. Previous affiliations of Jonathan A. Fletcher include Albany Medical College & Oregon Health & Science University.


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Journal ArticleDOI
TL;DR: Imatinib induced a sustained objective response in more than half of patients with an advanced unresectable or metastatic gastrointestinal stromal tumor, indicating that inhibition of the KIT signal-transduction pathway is a promising treatment for advanced gastrointestinalStromal tumors, which resist conventional chemotherapy.
Abstract: Background Constitutive activation of KIT receptor tyrosine kinase is critical in the pathogenesis of gastrointestinal stromal tumors. Imatinib mesylate, a selective tyrosine kinase inhibitor, has been shown in preclinical models and preliminary clinical studies to have activity against such tumors. Methods We conducted an open-label, randomized, multicenter trial to evaluate the activity of imatinib in patients with advanced gastrointestinal stromal tumor. We assessed antitumor response and the safety and tolerability of the drug. Pharmacokinetics were assessed in a subgroup of patients. Results A total of 147 patients were randomly assigned to receive 400 mg or 600 mg of imatinib daily. Overall, 79 patients (53.7 percent) had a partial response, 41 patients (27.9 percent) had stable disease, and for technical reasons, response could not be evaluated in 7 patients (4.8 percent). No patient had a complete response to the treatment. The median duration of response had not been reached after a median follow...

4,057 citations

Journal ArticleDOI
Rameen Beroukhim, Craig H. Mermel1, Craig H. Mermel2, Dale Porter3, Guo Wei1, Soumya Raychaudhuri1, Soumya Raychaudhuri4, Jerry Donovan3, Jordi Barretina2, Jordi Barretina1, Jesse S. Boehm1, Jennifer Dobson2, Jennifer Dobson1, Mitsuyoshi Urashima5, Kevin T. Mc Henry3, Reid M. Pinchback1, Azra H. Ligon4, Yoon Jae Cho6, Leila Haery2, Leila Haery1, Heidi Greulich, Michael R. Reich1, Wendy Winckler1, Michael S. Lawrence1, Barbara A. Weir2, Barbara A. Weir1, Kumiko E. Tanaka2, Kumiko E. Tanaka1, Derek Y. Chiang1, Derek Y. Chiang7, Derek Y. Chiang2, Adam J. Bass2, Adam J. Bass4, Adam J. Bass1, Alice Loo3, Carter Hoffman1, Carter Hoffman2, John R. Prensner2, John R. Prensner1, Ted Liefeld1, Qing Gao1, Derek Yecies2, Sabina Signoretti4, Sabina Signoretti2, Elizabeth A. Maher8, Frederic J. Kaye, Hidefumi Sasaki9, Joel E. Tepper7, Jonathan A. Fletcher4, Josep Tabernero10, José Baselga10, Ming-Sound Tsao11, Francesca Demichelis12, Mark A. Rubin12, Pasi A. Jänne4, Pasi A. Jänne2, Mark J. Daly2, Mark J. Daly1, Carmelo Nucera13, Ross L. Levine14, Benjamin L. Ebert2, Benjamin L. Ebert4, Benjamin L. Ebert1, Stacey Gabriel1, Anil K. Rustgi15, Cristina R. Antonescu14, Marc Ladanyi14, Anthony Letai2, Levi A. Garraway2, Levi A. Garraway1, Massimo Loda4, Massimo Loda2, David G. Beer16, Lawrence D. True17, Aikou Okamoto5, Scott L. Pomeroy6, Samuel Singer14, Todd R. Golub18, Todd R. Golub1, Todd R. Golub2, Eric S. Lander19, Eric S. Lander2, Eric S. Lander1, Gad Getz1, William R. Sellers3, Matthew Meyerson2, Matthew Meyerson1 
18 Feb 2010-Nature
TL;DR: It is demonstrated that cancer cells containing amplifications surrounding the MCL1 and BCL2L1 anti-apoptotic genes depend on the expression of these genes for survival, and a large majority of SCNAs identified in individual cancer types are present in several cancer types.
Abstract: A powerful way to discover key genes with causal roles in oncogenesis is to identify genomic regions that undergo frequent alteration in human cancers. Here we present high-resolution analyses of somatic copy-number alterations (SCNAs) from 3,131 cancer specimens, belonging largely to 26 histological types. We identify 158 regions of focal SCNA that are altered at significant frequency across several cancer types, of which 122 cannot be explained by the presence of a known cancer target gene located within these regions. Several gene families are enriched among these regions of focal SCNA, including the BCL2 family of apoptosis regulators and the NF-kappaBeta pathway. We show that cancer cells containing amplifications surrounding the MCL1 and BCL2L1 anti-apoptotic genes depend on the expression of these genes for survival. Finally, we demonstrate that a large majority of SCNAs identified in individual cancer types are present in several cancer types.

3,375 citations

Journal ArticleDOI
31 Jan 2003-Science
TL;DR: Tumors expressing KIT or PDGFRA oncoproteins were indistinguishable with respect to activation of downstream signaling intermediates and cytogenetic changes associated with tumor progression, suggesting KIT and PDGFra mutations appear to be alternative and mutually exclusive oncogenic mechanisms in GISTs.
Abstract: Most gastrointestinal stromal tumors (GISTs) have activating mutations in the KIT receptor tyrosine kinase, and most patients with GISTs respond well to Gleevec, which inhibits KIT kinase activity. Here we show that approximately 35% (14 of 40) of GISTs lacking KIT mutations have intragenic activation mutations in the related receptor tyrosine kinase, platelet-derived growth factor receptor alpha (PDGFRA). Tumors expressing KIT or PDGFRA oncoproteins were indistinguishable with respect to activation of downstream signaling intermediates and cytogenetic changes associated with tumor progression. Thus, KIT and PDGFRA mutations appear to be alternative and mutually exclusive oncogenic mechanisms in GISTs.

2,249 citations

Journal ArticleDOI
TL;DR: Activating mutations of KIT or PDGFRA are found in the vast majority of GISTs, and the mutational status of these oncoproteins is predictive of clinical response to imatinib.
Abstract: Purpose: Most gastrointestinal stromal tumors (GISTs) express constitutively activated mutant isoforms of KIT or kinase platelet-derived growth factor receptor alpha (PDGFRA) that are potential therapeutic targets for imatinib mesylate. The relationship between mutations in these kinases and clinical response to imatinib was examined in a group of patients with advanced GIST. Patients and Methods: GISTs from 127 patients enrolled onto a phase II clinical study of imatinib were examined for mutations of KIT or PDGFRA. Mutation types were correlated with clinical outcome. Results: Activating mutations of KIT or PDGFRA were found in 112 (88.2%) and six (4.7%) GISTs, respectively. Most KIT mutations involved exon 9 (n = 23) or exon 11 (n = 85). All KIT mutant isoforms, but only a subset of PDGFRA mutant isoforms, were sensitive to imatinib, in vitro. In patients with GISTs harboring exon 11 KIT mutations, the partial response rate (PR) was 83.5%, whereas patients with tumors containing an exon 9 KIT mutation ...

2,180 citations

Journal ArticleDOI
TL;DR: The rapid progress that has established GIST as a model for understanding the role of oncogenic kinase mutations in human tumorigenesis is charted and a molecular-based classification of GIST is proposed.
Abstract: Once a poorly defined pathologic oddity, in recent years, gastrointestinal stromal tumor (GIST) has emerged as a distinct oncogenetic entity that is now center stage in clinical trials of kinase-targeted therapies. This review charts the rapid progress that has established GIST as a model for understanding the role of oncogenic kinase mutations in human tumorigenesis. Approximately 80% to 85% of GISTs harbor activating mutations of the KIT tyrosine kinase. In a series of 322 GISTs (including 140 previously published cases) studied by the authors in detail, mutations in the KIT gene occurred with decreasing frequency in exons 11 (66.1%), 9 (13%), 13 (1.2%), and 17 (0.6%). In the same series, a subset of tumors had mutations in the KIT-related kinase gene PDGF receptor alpha (PDGFRA), which occurred in either exon 18 (5.6%) or 12 (1.5%). The remainder of GISTs (12%) were wild type for both KIT and PDGFRA. Comparative studies of KIT-mutant, PDGFRA-mutant, and wild-type GISTs indicate that there are many similarities between these groups of tumors but also important differences. In particular, the responsiveness of GISTs to treatment with the kinase inhibitor imatinib varies substantially depending on the exonic location of the KIT or PDGFRA mutation. Given these differences, which have implications both for the diagnosis and treatment of GISTs, we propose a molecular-based classification of GIST. Recent studies of familial GIST, pediatric GIST, and variant forms of GIST related to Carney's triad and neurofibromatosis type 1 are discussed in relationship to this molecular classification. In addition, the role of mutation screening in KIT and PDGFRA as a diagnostic and prognostic aid is emphasized in this review.

1,129 citations


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Book
29 Sep 2017
TL;DR: Thank you very much for reading who classification of tumours of haematopoietic and lymphoid tissues, and maybe you have knowledge that, people have look hundreds of times for their chosen readings like this, but end up in malicious downloads.
Abstract: WHO CLASSIFICATION OF TUMOURS OF HAEMATOPOIETIC AND LYMPHOID TISSUES , WHO CLASSIFICATION OF TUMOURS OF HAEMATOPOIETIC AND LYMPHOID TISSUES , کتابخانه مرکزی دانشگاه علوم پزشکی تهران

13,835 citations

Journal ArticleDOI
TL;DR: A subgroup of patients with non-small-cell lung cancer have specific mutations in the EGFR gene which correlate with clinical responsiveness to the tyrosine kinase inhibitor gefitinib, and these mutations lead to increased growth factor signaling and confer susceptibility to the inhibitor.
Abstract: BACKGROUND Most patients with non-small-cell lung cancer have no response to the tyrosine kinase inhibitor gefitinib, which targets the epidermal growth factor receptor (EGFR). However, about 10 percent of patients have a rapid and often dramatic clinical response. The molecular mechanisms underlying sensitivity to gefitinib are unknown. METHODS We searched for mutations in the EGFR gene in primary tumors from patients with non-small-cell lung cancer who had a response to gefitinib, those who did not have a response, and those who had not been exposed to gefitinib. The functional consequences of identified mutations were evaluated after the mutant proteins were expressed in cultured cells. RESULTS Somatic mutations were identified in the tyrosine kinase domain of the EGFR gene in eight of nine patients with gefitinib-responsive lung cancer, as compared with none of the seven patients with no response (P<0.001). Mutations were either small, in-frame deletions or amino acid substitutions clustered around the ATP-binding pocket of the tyrosine kinase domain. Similar mutations were detected in tumors from 2 of 25 patients with primary non-small-cell lung cancer who had not been exposed to gefitinib (8 percent). All mutations were heterozygous, and identical mutations were observed in multiple patients, suggesting an additive specific gain of function. In vitro, EGFR mutants demonstrated enhanced tyrosine kinase activity in response to epidermal growth factor and increased sensitivity to inhibition by gefitinib. CONCLUSIONS A subgroup of patients with non-small-cell lung cancer have specific mutations in the EGFR gene, which correlate with clinical responsiveness to the tyrosine kinase inhibitor gefitinib. These mutations lead to increased growth factor signaling and confer susceptibility to the inhibitor. Screening for such mutations in lung cancers may identify patients who will have a response to gefitinib.

10,879 citations

Journal ArticleDOI
TL;DR: A unified analytic framework to discover and genotype variation among multiple samples simultaneously that achieves sensitive and specific results across five sequencing technologies and three distinct, canonical experimental designs is presented.
Abstract: Recent advances in sequencing technology make it possible to comprehensively catalogue genetic variation in population samples, creating a foundation for understanding human disease, ancestry and evolution. The amounts of raw data produced are prodigious and many computational steps are required to translate this output into high-quality variant calls. We present a unified analytic framework to discover and genotype variation among multiple samples simultaneously that achieves sensitive and specific results across five sequencing technologies and three distinct, canonical experimental designs. Our process includes (1) initial read mapping; (2) local realignment around indels; (3) base quality score recalibration; (4) SNP discovery and genotyping to find all potential variants; and (5) machine learning to separate true segregating variation from machine artifacts common to next-generation sequencing technologies. We discuss the application of these tools, instantiated in the Genome Analysis Toolkit (GATK), to deep whole-genome, whole-exome capture, and multi-sample low-pass (~4×) 1000 Genomes Project datasets.

10,056 citations

Journal ArticleDOI
04 Jun 2004-Science
TL;DR: Results suggest that EGFR mutations may predict sensitivity to gefitinib, and treatment with the EGFR kinase inhibitor gefitsinib causes tumor regression in some patients with NSCLC, more frequently in Japan.
Abstract: Receptor tyrosine kinase genes were sequenced in nonsmall cell lung cancer (NSCLC) and matched normal tissue. Somatic mutations of the epidermal growth factor receptor gene EGFR were found in 15 of 58 unselected tumors from Japan and 1 of 61 from the United States. Treatment with the EGFR kinase inhibitor gefitinib (Iressa) causes tumor regression in some patients with NSCLC, more frequently in Japan. EGFR mutations were found in additional lung cancer samples from U.S. patients who responded to gefitinib therapy and in a lung adenocarcinoma cell line that was hypersensitive to growth inhibition by gefitinib, but not in gefitinibinsensitive tumors or cell lines. These results suggest that EGFR mutations may predict sensitivity to gefitinib. Protein kinase activation by somatic mutation or

9,265 citations