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      Gastrointestinal Stromal Tumor – An Evolving Concept

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          Abstract

          Gastrointestinal stromal tumors (GISTs) are the most frequent mesenchymal tumors of the gastrointestinal tract. The discovery that these tumors, formerly thought of smooth muscle origin, are indeed better characterized by specific activating mutation in genes coding for the receptor tyrosine kinases (RTKs) CKIT and PDGFRA and that these mutations are strongly predictive for the response to targeted therapy with RTK inhibitors has made GISTs the typical example of the integration of basic molecular knowledge in the daily clinical activity. The information on the mutational status of these tumors is essential to predict (and subsequently to plan) the therapy. As resistant cases are frequently wild type, other possible oncogenic events, defining other “entities,” have been discovered (e.g., succinil dehydrogenase mutation/dysregulation, insuline growth factor expression, and mutations in the RAS-RAF-MAPK pathway). The classification of disease must nowadays rely on the integration of the clinico-morphological characteristics with the molecular data.

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          Most cited references 154

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          Gain-of-function mutations of c-kit in human gastrointestinal stromal tumors.

          Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the human digestive tract, but their molecular etiology and cellular origin are unknown. Sequencing of c-kit complementary DNA, which encodes a proto-oncogenic receptor tyrosine kinase (KIT), from five GISTs revealed mutations in the region between the transmembrane and tyrosine kinase domains. All of the corresponding mutant KIT proteins were constitutively activated without the KIT ligand, stem cell factor (SCF). Stable transfection of the mutant c-kit complementary DNAs induced malignant transformation of Ba/F3 murine lymphoid cells, suggesting that the mutations contribute to tumor development. GISTs may originate from the interstitial cells of Cajal (ICCs) because the development of ICCs is dependent on the SCF-KIT interaction and because, like GISTs, these cells express both KIT and CD34.
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            Succinate links TCA cycle dysfunction to oncogenesis by inhibiting HIF-alpha prolyl hydroxylase.

            Several mitochondrial proteins are tumor suppressors. These include succinate dehydrogenase (SDH) and fumarate hydratase, both enzymes of the tricarboxylic acid (TCA) cycle. However, to date, the mechanisms by which defects in the TCA cycle contribute to tumor formation have not been elucidated. Here we describe a mitochondrion-to-cytosol signaling pathway that links mitochondrial dysfunction to oncogenic events: succinate, which accumulates as a result of SDH inhibition, inhibits HIF-alpha prolyl hydroxylases in the cytosol, leading to stabilization and activation of HIF-1alpha. These results suggest a mechanistic link between SDH mutations and HIF-1alpha induction, providing an explanation for the highly vascular tumors that develop in the absence of VHL mutations.
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              PDGFRA activating mutations in gastrointestinal stromal tumors.

              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.
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                Author and article information

                Affiliations
                1Institute of Pathology, University of Basel , Basel, Switzerland
                Author notes

                Edited by: Dolores Di Vizio, Harvard Medical School, USA

                Reviewed by: Rosa Marina Melillo, University of Naples Federico II, Italy; Renato Franco, Istituto Tumori Fondazione Giovanni Pascale, Italy

                *Correspondence: Luigi Tornillo, Institute of Pathology, University of Basel, Schönbeinstrasse 40, CH-4003 Basel, Switzerland e-mail: tornillol@ 123456uhbs.ch

                This article was submitted to Pathology, a section of the journal Frontiers in Medicine.

                Contributors
                Journal
                Front Med (Lausanne)
                Front Med (Lausanne)
                Front. Med.
                Frontiers in Medicine
                Frontiers Media S.A.
                2296-858X
                11 November 2014
                2014
                : 1
                10.3389/fmed.2014.00043
                4291900
                Copyright © 2014 Tornillo.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

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                Figures: 4, Tables: 1, Equations: 0, References: 154, Pages: 12, Words: 9637
                Categories
                Medicine
                Reviews in Medicine

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