Abstract Gastrointestinal stromal tumors (GISTs) were originally thought to harbor either KIT or platelet-derived growth factor receptor A ( PDGFRA) mutations only. However, more recent discoveries ...have highlighted additional, less common oncogenic driver mutations including NF1 , BRAF , and succinate dehydrogenase ( SDH ) mutations. Genotyping GISTs has become more important since not all genotypes respond equally to FDA-approved tyrosine kinase inhibitors. GIST is a paradigm for personalized cancer therapy. Recent studies demonstrate how immunohistochemistry can be used both to diagnose GIST and to screen for specific mutations. DOG1 is particularly useful in the diagnosis of KIT-negative GIST, including tumors with PDGFRA mutations, which can also potentially be identified by immunohistochemistry for PDGFRA. SDHB immunohistochemistry is useful in characterizing GISTs with SDHA-D mutations, whereas SDHA immunohistochemistry is able to identify SDHA mutant GISTs.
Tenosynovial giant-cell tumor (TGCT) and pigmented villonodular synovitis (PVNS) are related conditions with features of both reactive inflammatory disorders and clonal neoplastic proliferations. ...Chromosomal translocations involving chromosome 1p13 have been reported in both TGCT and PVNS. We confirm that transiocations involving p1pl3 are present in a majority of cases of TGCT and PVNS and show that CSF1 is the gene at the chromosome lp13 breakpoint. In some cases of both TGCT and PVNS, CSF1 is fused to COL6A3 (2q35). The CSF1 translocations result in overexpression of CSF1. In cases of TGCT and PVNS carrying this translocation, it is present in a minority of the intratumoral cells, leading to CSF1 expression only in these cells, whereas the majority of cells express CSFIR but not CSF1, suggesting a tumor-landscaping effect with aberrant CSF1 expression in the neoplastic cells, leading to the abnormal accumulation of nonneoplastic cells that form a tumorous mass.
Although gastrointestinal stromal tumors (GISTs) harboring activating KIT or platelet-derived growth factor receptor A (PDGFRA) mutations respond to treatment with targeted KIT/PDGFRA inhibitors such ...as imatinib mesylate, these treatments are rarely curative. Most often, a sizeable tumor cell subpopulation survives and remains quiescent for years, eventually resulting in acquired resistance and treatment failure. Here, we report that imatinib induces autophagy as a survival pathway in quiescent GIST cells. Inhibiting autophagy, using RNAi-mediated silencing of autophagy regulators (ATGs) or antimalarial lysosomotrophic agents, promotes the death of GIST cells both in vitro and in vivo. Thus, combining imatinib with autophagy inhibition represents a potentially valuable strategy to promote GIST cytotoxicity and to diminish both cellular quiescence and acquired resistance in GIST patients.
Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms arising in the gastrointestinal tract. GISTs express the KIT receptor tyrosine kinase, and many cases have activating ...mutations in the KIT juxtamembrane region. We now report an analysis of
KIT
cDNA and genomic sequences in eight GISTs that lack juxtamembrane region mutations. Six cases contained heterozygous exon 9 mutations in which six nucleotides, encoding Ala-Tyr, were duplicated. The other two cases contained homozygous exon 13 missense mutations, resulting in substitution of Glu for Lys
642, that were associated with constitutive KIT tyrosine phosphorylation. Sequence analysis of DNAs from nonneoplastic companion tissues revealed that both the exon 9 and exon 13 mutations were somatic. These are the first descriptions, in any tumor, of mutations in
KIT
exons encoding the C-terminal end of the extracellular domain and the first part of the split kinase domain. These findings indicate that KIT may be activated by mutations in at least three domains—extracellular, juxtamembrane, and kinase—in GISTs.
Rhabdomyosarcoma is the most commonly occurring soft-tissue sarcoma in childhood. Most rhabdomyosarcoma falls into one of two biologically distinct subgroups represented by alveolar or embryonal ...histology. The alveolar subtype harbors a translocation-mediated PAX3:FOXO1A fusion gene and has an extremely poor prognosis. However, tumor cells have heterogeneous expression for the fusion gene. Using a conditional genetic mouse model as well as human tumor cell lines, we show that that Pax3:Foxo1a expression is enriched in G2 and triggers a transcriptional program conducive to checkpoint adaptation under stress conditions such as irradiation in vitro and in vivo. Pax3:Foxo1a also tolerizes tumor cells to clinically-established chemotherapy agents and emerging molecularly-targeted agents. Thus, the surprisingly dynamic regulation of the Pax3:Foxo1a locus is a paradigm that has important implications for the way in which oncogenes are modeled in cancer cells.
Retinal pigment epithelial (RPE) cells are central to retinal health and homoeostasis. Oxidative stress-induced damage to the RPE occurs as part of the pathogenesis of age-related macular ...degeneration and neovascular retinopathies (e.g., retinopathy of prematurity, diabetic retinopathy). The xanthophyll carotenoids, lutein and zeaxanthin, are selectively taken up by the RPE, preferentially accumulated in the human macula, and transferred to photoreceptors. These macular xanthophylls protect the macula (and the broader retina) via their antioxidant and photo-protective activities. This study was designed to investigate effects of various carotenoids (β-carotene, lycopene, and lutein) on RPE cells subjected to either hypoxia or oxidative stress, in order to determine if there is effect specificity for macular pigment carotenoids. Using human RPE-derived ARPE-19 cells as an in vitro model, we exposed RPE cells to various concentrations of the specific carotenoids, followed by either graded hypoxia or oxidative stress using
-butyl hydroperoxide (tBHP). The results indicate that lutein and lycopene, but not β-carotene, inhibit cell growth in undifferentiated ARPE-19 cells. Moreover, cell viability was decreased under hypoxic conditions. Pre-incubation of ARPE-19 cells with lutein or lycopene protected against tBHP-induced cell loss and cell co-exposure of lutein or lycopene with tBHP essentially neutralized tBHP-dependent cell death at tBHP concentrations up to 500 μM. Our findings indicate that lutein and lycopene inhibit the growth of human RPE cells and protect the RPE against oxidative stress-induced cell loss. These findings contribute to the understanding of the protective mechanisms attributable to retinal xanthophylls in eye health and retinopathies.
We have observed a significant enhancement in the energy deposition by 25–
100
GeV
photons in a
1
cm
thick tungsten crystal oriented along its
⟨
111
⟩
lattice axes. At
100
GeV
, this enhancement, ...with respect to the value observed without axial alignment, is more than twofold. This effect, together with the measured huge increase in secondary particle generation is ascribed to the acceleration of the electromagnetic shower development by the strong axial electric field. The experimental results have been critically compared with a newly developed Monte Carlo adapted for use with crystals of multi-
X
0
thickness. The results presented in this paper may prove to be of significant interest for the development of high-performance photon absorbers and highly compact electromagnetic calorimeters and beam dumps for use at the energy and intensity frontiers.
Embryonal rhabdomyosarcoma (eRMS) shows the most myodifferentiation among sarcomas, yet the precise cell of origin remains undefined. Using
Ptch1,
p53 and/or
Rb1 conditional mouse models and ...controlling prenatal or postnatal myogenic cell of origin, we demonstrate that eRMS and undifferentiated pleomorphic sarcoma (UPS) lie in a continuum, with satellite cells predisposed to giving rise to UPS. Conversely, p53 loss in maturing myoblasts gives rise to eRMS, which have the highest myodifferentiation potential. Regardless of origin,
Rb1 loss modifies tumor phenotype to mimic UPS. In human sarcomas that lack pathognomic chromosomal translocations,
p53 loss of function is prevalent, whereas Shh or
Rb1 alterations likely act primarily as modifiers. Thus, sarcoma phenotype is strongly influenced by cell of origin and mutational profile.
Display omitted
► Embryonal rhabdomyosarcoma and undifferentiated pleomorphic sarcoma form a continuum ► Mutant
p53,
Ptch1, or
Rb1 in satellite cells gives rise to undifferentiated sarcoma ► Embryonal rhabdomyosarcoma arise from myoblasts but express satellite cell markers ►
Rb1 loss acts as an apparent modifier for sarcomas by inducing dedifferentiation
As a result of major recent advances in understanding the biology of gastrointestinal stromal tumors (GISTs), specifically recognition of the central role of activating KIT mutations and associated ...KIT protein expression in these lesions, and the development of novel and effective therapy for GISTs using the receptor tyrosine kinase inhibitor STI-571, these tumors have become the focus of considerable attention by pathologists, clinicians, and patients. Stromal/mesenchymal tumors of the gastrointestinal tract have long been a source of confusion and controversy with regard to classification, line(s) of differentiation, and prognostication. Characterization of the KIT pathway and its phenotypic implications has helped to resolve some but not all of these issues. Given the now critical role of accurate and reproducible pathologic diagnosis in ensuring appropriate treatment for patients with GIST, the National Institutes of Health convened a GIST workshop in April 2001 with the goal of developing a consensus approach to diagnosis and morphologic prognostication. Key elements of the consensus, as described herein, are the defining role of KIT immunopositivity in diagnosis and a proposed scheme for estimating metastatic risk in these lesions, based on tumor size and mitotic count, recognizing that it is probably unwise to use the definitive term “benign” for any GIST, at least at the present time. HUM PATHOL 33:459-465. Copyright 2002, Elsevier Science (USA). All rights reserved.
Background & Aims Depletion of interstitial cells of Cajal (ICCs) is common in diabetic gastroparesis. However, in approximately 20% of patients with diabetes, gastric emptying (GE) is accelerated. ...GE also occurs faster in obese individuals, and is associated with increased blood levels of glucose in patients with type 2 diabetes. To understand the fate of ICCs in hyperinsulinemic, hyperglycemic states characterized by rapid GE, we studied mice with mutation of the leptin receptor ( Leprdb/db ), which in our colony had accelerated GE. We also investigated hyperglycemia-induced signaling in the ICC lineage and ICC dependence on glucose oxidative metabolism in mice with disruption of the succinate dehydrogenase complex, subunit C gene ( Sdhc ). Methods Mice were given breath tests to analyze GE of solids. ICCs were studied by flow cytometry, intracellular electrophysiology, isometric contractility measurement, reverse-transcription polymerase chain reaction, immunoblot, immunohistochemistry, enzyme-linked immunosorbent assays, and metabolite assays; cells and tissues were manipulated pharmacologically and by RNA interference. Viable cell counts, proliferation, and apoptosis were determined by methyltetrazolium, Ki-67, proliferating cell nuclear antigen, bromodeoxyuridine, and caspase–Glo 3/7 assays. Sdhc was disrupted in 2 different strains of mice via cre recombinase. Results In obese, hyperglycemic, hyperinsulinemic female Leprdb/db mice, GE was accelerated and gastric ICC and phasic cholinergic responses were increased. Female KitK641E/+ mice, which have genetically induced hyperplasia of ICCs, also had accelerated GE. In isolated cells of the ICC lineage and gastric organotypic cultures, hyperglycemia stimulated proliferation by mitogen-activated protein kinase 1 (MAPK1)- and MAPK3-dependent stabilization of ets variant 1—a master transcription factor for ICCs—and consequent up-regulation of v-kit Hardy–Zuckerman 4 feline sarcoma viral oncogene homolog (KIT) proto-oncogene receptor tyrosine kinase (KIT). Opposite changes occurred in mice with disruption of Sdhc. Conclusions Hyperglycemia increases ICCs via oxidative metabolism-dependent, MAPK1- and MAPK3-mediated stabilization of ets variant 1 and increased expression of KIT, causing rapid GE. Increases in ICCs might contribute to the acceleration in GE observed in some patients with diabetes.
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