Sriram Venneti

Institut Claudius Regaud, Tolosa de Llenguadoc, Midi-Pyrénées, France

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Publications (48)274.33 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Receptor tyrosine kinase (RTK) signaling promotes the growth and progression of glioblastoma (GBM), a highly aggressive type of brain tumor. We previously reported that decreased miR-218 expression in GBM directly promotes RTK activity by increasing the expression of key RTKs and their signaling mediators, including the RTK epidermal growth factor receptor (EGFR), phospholipase C-γ1 (PLCγ1), and the kinases PIK3CA and ARAF. However, increased RTK signaling usually activates negative feedback mechanisms to maintain homeostasis. We found that decreased miR-218 expression in GBM cells also increased the expression of genes encoding additional upstream and downstream components of RTK signaling pathways, including the RTK platelet-derived growth factor receptor α (PDGFRα) and the kinases ribosomal S6 kinase 2 (RSK2) and S6 kinase 1 (S6K1), that collectively overrode the negative feedback mechanism. Furthermore, increased RTK signaling itself suppressed miR-218 expression. Mass spectrometry and DNA pull-down identified binding of signal transducer and activator of transcription 3 (STAT3) along with the transcriptional repressor BCL2-associated transcription factor 1 (BCLAF1) directly to the miR-218 locus. These data identify previously unknown feedback loops by which miR-218 repression promotes increased RTK signaling in high-grade gliomas. Copyright © 2015, American Association for the Advancement of Science.
    Science Signaling 05/2015; 8(375):ra42. DOI:10.1126/scisignal.2005978 · 7.65 Impact Factor
  • Neuro-Oncology 04/2015; 17(suppl 3):iii12-iii12. DOI:10.1093/neuonc/nov061.44 · 5.29 Impact Factor
  • Sriram Venneti, Jason T Huse
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    ABSTRACT: Low-grade gliomas (LGG) constitute grades I and II tumors of astrocytic and grade II tumors of oligodendroglial lineage. Although these tumors are typically slow growing, they may be associated with significant morbidity and mortality because of recurrence and malignant progression, even in the setting of optimal resection. LGG in pediatric and adult age groups are currently classified by morphologic criteria. Recent years have heralded a molecular revolution in understanding brain tumors, including LGG. Next-generation sequencing has definitively demonstrated that pediatric and adult LGG fundamentally differ in their underlying molecular characteristics, despite being histologically similar. Pediatric LGG show alterations in FGFR1 and BRAF in pilocytic astrocytomas and FGFR1 alterations in diffuse astrocytomas, each converging on the mitogen-activated protein kinase signaling pathway. Adult LGG are characterized by IDH1/2 mutations and ATRX mutations in astrocytic tumors and IDH1/2 mutations and 1p/19q codeletions in oligodendroglial tumors. TERT promoter mutations are also noted in LGG and are mainly associated with oligodendrogliomas. These findings have considerably refined approaches to classifying these tumors. Moreover, many of the molecular alterations identified in LGG directly impact on prognosis, tumor biology, and the development of novel therapies.
    Advances in Anatomic Pathology 03/2015; 22(2):94-101. DOI:10.1097/PAP.0000000000000049 · 3.10 Impact Factor
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    ABSTRACT: Glucose and glutamine are the two principal nutrients that cancer cells use to proliferate and survive. Many cancers show altered glucose metabolism, which constitutes the basis for in vivo positron emission tomography (PET) imaging with (18)F-fluorodeoxyglucose ((18)F-FDG). However, (18)F-FDG is ineffective in evaluating gliomas because of high background uptake in the brain. Glutamine metabolism is also altered in many cancers, and we demonstrate that PET imaging in vivo with the glutamine analog 4-(18)F-(2S,4R)-fluoroglutamine ((18)F-FGln) shows high uptake in gliomas but low background brain uptake, facilitating clear tumor delineation. Chemo/radiation therapy reduced (18)F-FGln tumor avidity, corresponding with decreased tumor burden. (18)F-FGln uptake was not observed in animals with a permeable blood-brain barrier or neuroinflammation. We translated these findings to human subjects, where (18)F-FGln showed high tumor/background ratios with minimal uptake in the surrounding brain in human glioma patients with progressive disease. These data suggest that (18)F-FGln is avidly taken up by gliomas, can be used to assess metabolic nutrient uptake in gliomas in vivo, and may serve as a valuable tool in the clinical management of gliomas. Copyright © 2015, American Association for the Advancement of Science.
    Science translational medicine 02/2015; 7(274):274ra17. DOI:10.1126/scitranslmed.aaa1009 · 14.41 Impact Factor
  • Cancer Research 01/2015; 75(1 Supplement):B68-B68. DOI:10.1158/1538-7445.CHTME14-B68 · 9.28 Impact Factor
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    ABSTRACT: Choroid plexus tumors (CPTs) are rare neoplasms arising from the choroid plexus epithelium, and occur predominantly in infants and children. CPTs may be associated with TP53 germline mutations (Li–Fraumeni syndrome), but the majority of CPTs are sporadic. Most commonly, CPTs present with signs of increased intracranial pressure; on imaging they are characterized as intraventricular contrast-enhancing masses. Histopathologically, CPTs comprise benign choroid plexus papilloma (CPP, WHO grade I), atypical choroid plexus papilloma (APP, WHO grade II), and malignant choroid plexus carcinoma (CPC, WHO grade III). Complete surgical resection may be curative for CPPs, while CPCs are additionally treated with chemotherapy and radiation. In this chapter we discuss these features in detail, as well as differential diagnosis and immunohistochemical studies. Particular emphasis is placed on the molecular alterations, how they can be detected in the laboratory using immunohistochemistry and molecular testing, and how they may lead to novel-targeted therapeutic approaches.
    01/2015: pages 163-175;
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    ABSTRACT: Atypical teratoid/rhabdoid tumors (AT/RTs) are highly aggressive and lethal tumors encountered primarily in the pediatric age group. These tumors are defined by mutations and deletions in the SMARCB1 (SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1) gene (also referred to as SNF5/BAF47/INI1) or, in very rare cases, other genes related to the SWI/SNF chromatin remodeling complex. Histologically, these tumors are variable in their appearance and show a spectrum of features, including characteristic rhabdoid cells and immunohistochemical evidence of polyphenotypic differentiation. We discuss the clinical manifestations including epidemiology, neuroradiologic features, histopathology, differential diagnosis, and immunohistochemical studies that aid in the diagnosis of AT/RT. Emphasis is placed on the molecular genetic alterations encountered in this tumor, how detection of genetic alterations in SMARCB1 can be accomplished in the clinical laboratory using immunohistochemistry and molecular approaches, and how these alterations contribute to the elucidation of the pathogenesis of AT/RT. Finally, we outline the poor clinical prognosis borne by patients with AT/RT and discuss the current and potential new treatment regimens that could be used to treat these deadly tumors.
    Molecular Pathology of Nervous System Tumors, 01/2015: pages 177-189;
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    ABSTRACT: Many cancer cells consume large quantities of glutamine to maintain TCA cycle anaplerosis and support cell survival. It was therefore surprising when RNAi screening revealed that suppression of citrate synthase (CS), the first TCA cycle enzyme, prevented glutamine-withdrawal-induced apoptosis. CS suppression reduced TCA cycle activity and diverted oxaloacetate, the substrate of CS, into production of the nonessential amino acids aspartate and asparagine. We found that asparagine was necessary and sufficient to suppress glutamine-withdrawal-induced apoptosis without restoring the levels of other nonessential amino acids or TCA cycle intermediates. In complete medium, tumor cells exhibiting high rates of glutamine consumption underwent rapid apoptosis when glutamine-dependent asparagine synthesis was suppressed, and expression of asparagine synthetase was statistically correlated with poor prognosis in human tumors. Coupled with the success of L-asparaginase as a therapy for childhood leukemia, the data suggest that intracellular asparagine is a critical suppressor of apoptosis in many human tumors.
    Molecular Cell 09/2014; 56(2). DOI:10.1016/j.molcel.2014.08.018 · 14.46 Impact Factor
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    ABSTRACT: Pediatric glioblastomas (GBM) are highly aggressive and lethal tumors. Recent sequencing studies have shown that ~30 % of pediatric GBM and ~80 % of diffuse intrinsic pontine gliomas show K27M mutations in the H3F3A gene, a variant encoding histone H3.3. H3F3A K27M mutations lead to global reduction in H3K27me3. Our goal was to develop biomarkers for the histopathologic detection of these tumors. Therefore, we evaluated the utility of measuring H3K27me3 global reduction as a histopathologic and prognostic biomarker and tested an antibody directed specifically against the H3.3 K27M mutation in 290 samples. The study cohort included 203 pediatric (including 38 pediatric high-grade astrocytomas) and 38 adult brain tumors of various subtypes and grades and 49 non-neoplastic reactive brain tissues. Detection of H3.3 K27M by immunohistochemistry showed 100 % sensitivity and specificity and was superior to global reduction in H3K27me3 as a biomarker in diagnosing H3F3A K27M mutations. Moreover, cases that stained positive for H3.3 K27M showed a significantly poor prognosis compared to corresponding negative tumors. These results suggest that immunohistochemical detection of H3.3 K27M is a sensitive and specific surrogate for the H3F3A K27M mutation and defines a prognostically poor subset of pediatric GBM. Electronic supplementary material The online version of this article (doi:10.1007/s00401-014-1338-3) contains supplementary material, which is available to authorized users.
    Acta Neuropathologica 09/2014; 128(5). DOI:10.1007/s00401-014-1338-3 · 9.78 Impact Factor
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    ABSTRACT: The de novo synthesis of the non-essential amino acid serine is often upregulated in cancer. In this study we demonstrate that the serine catabolic enzyme, mitochondrial serine hydroxymethyltransferase (SHMT2) is induced when Myc-transformed cells are subjected to hypoxia. In mitochondria, SHMT2 can initiate the degradation of serine to CO2 and NH4+ resulting in net production of NADPH from NADP+. Knockdown of SHMT2 in Myc-dependent cells reduced cellular NADPH/NADP+ ratio, increased cellular reactive oxygen species (ROS) and triggered hypoxia-induced cell death. In vivo, SHMT2 suppression led to impaired tumor growth. In myc-amplified neuroblastoma patient samples, there was a significant correlation between SHMT2 and Hypoxia-inducible factor-1 α (HIF-1α) and SHMT2 expression correlated with unfavorable patient prognosis. Together these data demonstrate that mitochondrial serine catabolism supports tumor growth by maintaining mitochondrial redox balance and cell survival.
    Cancer Discovery 09/2014; 4(12). DOI:10.1158/2159-8290.CD-14-0250 · 15.93 Impact Factor
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    ABSTRACT: Histone acetylation plays important roles in gene regulation, DNA replication, and the response to DNA damage, and it is frequently deregulated in tumors. We postulated that tumor cell histone acetylation levels are determined in part by changes in acetyl coenzyme A (acetyl-CoA) availability mediated by oncogenic metabolic reprogramming. Here, we demonstrate that acetyl-CoA is dynamically regulated by glucose availability in cancer cells and that the ratio of acetyl-CoA:coenzyme A within the nucleus modulates global histone acetylation levels. In vivo, expression of oncogenic Kras or Akt stimulates histone acetylation changes that precede tumor development. Furthermore, we show that Akt's effects on histone acetylation are mediated through the metabolic enzyme ATP-citrate lyase and that pAkt(Ser473) levels correlate significantly with histone acetylation marks in human gliomas and prostate tumors. The data implicate acetyl-CoA metabolism as a key determinant of histone acetylation levels in cancer cells.
    Cell Metabolism 07/2014; 20(2). DOI:10.1016/j.cmet.2014.06.004 · 16.75 Impact Factor
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    ABSTRACT: Up to 30% of pediatric glioblastomas (GB) demonstrate mutations in H3F3A, a gene variant encoding histone H3.3. Global reduction in H3K27me3 is associated with H3F3A K27M mutation.
    Neuro-Oncology 07/2014; 16 Suppl 3:iii29-iii30. DOI:10.1093/neuonc/nou208.26 · 5.29 Impact Factor
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    ABSTRACT: Glioblastomas are aggressive adult brain tumors, characterized by inadequately organized vasculature and consequent nutrient and oxygen (O2)-depleted areas. Adaptation to low nutrients and hypoxia supports glioblastoma cell survival, progression and therapeutic resistance. However, specific mechanisms promoting cellular survival under nutrient and O2 deprivation remain incompletely understood. Here, we show that miR-124 expression is negatively correlated with a hypoxic gene signature in glioblastoma patient samples, suggesting that low miR-124 levels contribute to pro-survival adaptive pathways in this disease. As miR-124 expression is repressed in various cancer types (including glioblastoma), we quantified miR-124 abundance in normoxic and hypoxic regions in glioblastoma patient tissue, and investigated whether ectopic miR-124 expression compromises cell survival during tumor ischemia. Our results indicate that miR-124 levels are further diminished in hypoxic/ischemic regions within individual glioblastoma patient samples, compared with regions replete in O2 and nutrients. Importantly, we also show that increased miR-124 expression affects the ability of tumor cells to survive under O2 and/or nutrient deprivation. Moreover, miR-124 re-expression increases cell death in vivo and enhances the survival of mice bearing intracranial xenograft tumors. miR-124 exerts this phenotype in part by directly regulating TEAD1, MAPK14/p38α and SERP1, factors involved in cell proliferation and survival under stress. Simultaneous suppression of these miR-124 targets results in similar levels of cell death as caused by miR-124 restoration. Importantly, we further demonstrate that SERP1 reintroduction reverses the hypoxic cell death elicited by miR-124, indicating the importance of SERP1 in promoting tumor cell survival. In support of our experimental data, we observed a significant correlation between high SERP1 levels and poor patient outcome in glioblastoma patients. Collectively, among the many pro-tumorigeneic properties of miR-124 repression in glioblastoma, we delineated a novel role in promoting tumor cell survival under stressful microenvironments, thereby supporting tumor progression.Oncogene advance online publication, 23 June 2014; doi:10.1038/onc.2014.168.
    Oncogene 06/2014; 34(17). DOI:10.1038/onc.2014.168 · 8.56 Impact Factor
  • Cancer Research 05/2014; 73(13 Supplement):A01-A01. DOI:10.1158/1538-7445.CEC13-A01 · 9.28 Impact Factor
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    ABSTRACT: Glioblastoma multiforme (GBM) and the mesenchymal GBM subtype in particular are highly malignant tumors that frequently exhibit regions of severe hypoxia and necrosis. Because these features correlate with poor prognosis, we investigated microRNAs whose expression might regulate hypoxic GBM cell survival and growth. We determined that the expression of microRNA-218 (miR-218) is decreased significantly in highly necrotic mesenchymal GBM, and orthotopic tumor studies revealed that reduced miR-218 levels confer GBM resistance to chemotherapy. Importantly, miR-218 targets multiple components of receptor tyrosine kinase (RTK) signaling pathways, and miR-218 repression increases the abundance and activity of multiple RTK effectors. This elevated RTK signaling also promotes the activation of hypoxia-inducible factor (HIF), most notably HIF2α. We further show that RTK-mediated HIF2α regulation is JNK dependent, via jun proto-oncogene. Collectively, our results identify an miR-218-RTK-HIF2α signaling axis that promotes GBM cell survival and tumor angiogenesis, particularly in necrotic mesenchymal tumors.
    Proceedings of the National Academy of Sciences 12/2013; 111(1). DOI:10.1073/pnas.1314341111 · 9.81 Impact Factor
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    ABSTRACT: More than 50% of patients with chondrosarcomas exhibit gain-of-function mutations in either isocitrate dehydrogenase 1 (IDH1) or IDH2. In this study, we performed genome-wide CpG methylation sequencing of chondrosarcoma biopsies and found that IDH mutations were associated with DNA hypermethylation at CpG islands but not other genomic regions. Regions of CpG island hypermethylation were enriched for genes implicated in stem cell maintenance/differentiation and lineage specification. In murine 10T1/2 mesenchymal progenitor cells, expression of mutant IDH2 led to DNA hypermethylation and an impairment in differentiation that could be reversed by treatment with DNA-hypomethylating agents. Introduction of mutant IDH2 also induced loss of contact inhibition and generated undifferentiated sarcomas in vivo. The oncogenic potential of mutant IDH2 correlated with the ability to produce 2-hydroxyglutarate. Together, these data demonstrate that neomorphic IDH2 mutations can be oncogenic in mesenchymal cells.
    Genes & development 09/2013; 27(18):1986-98. DOI:10.1101/gad.226753.113 · 12.64 Impact Factor
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    ABSTRACT: Abstract Glypican-3 (GPC3) is a proteoglycan thought to play an important role during development. Germline GPC3 mutations are seen in the rare Simpson-Golabi-Behmel syndrome (SGBS), which predisposes patients to Wilms tumor, hepatoblastoma, and neuroblastoma. While numerous adult tumors have been evaluated by immunohistochemistry (IHC) for GPC3, no comprehensive assessment has been done in pediatric tumors. We investigated GPC3 expression in 143 pediatric central nervous system (CNS) tumors and 271 non-CNS tumors. Among non-CNS tumors, GPC3 expression was seen in 9/9 (100%) hepatoblastomas, 4/6 (67%) malignant rhabdoid tumors, 5/13 (38%) Wilms tumors, 11/37 (30%) alveolar rhabdomyosarcomas, and 8/45 (18%) embryonal rhabdomyosarcomas. All 136 neuroblastomas, 14 Ewing sarcoma/primitive neuroectodermal tumors and 11 synovial sarcomas were immunonegative for GPC3. Among CNS tumors, GPC3 had restricted expression with positivity in 6/6 (100%) AT/RTs and 1/4 (25%) craniopharyngiomas. The remaining 136 CNS tumors, including 23 medulloblastomas, 21 pilocytic astrocytomas, 13 gangliogliomas, 12 ependymomas, 12 glioblastomas, 11 choroid plexus neoplasms, 10 diffuse astrocytomas (grade II/III), 10 meningiomas, 8 dysembryoplastic neuroepithelial tumors, 8 oligodendrogliomas, 3 craniopharyngiomas, 3 germinomas, and 2 neurocytomas, were entirely negative for GPC3. These results showed GPC3 positivity in a number of non-CNS tumors with no consistent discrimination between tumors that are or are not associated with SGBS. Within the CNS, GPC3 positivity was limited to a small subset of CNS neoplasms and may serve as a useful positive diagnostic biomarker (P value <0.0001) in addition to negative INI1/BAF47/SMARCB1 staining to differentiate AT/RT from other high-grade pediatric brain tumors.
    Pediatric and Developmental Pathology 03/2013; 16(4). DOI:10.2350/12-06-1216-OA.1 · 0.86 Impact Factor
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    ABSTRACT: Trimethylation of histone 3 lysine 9 (H3K9me3) is a marker of repressed transcription. Cells transfected with mutant isocitrate dehydrogenase (IDH) show increased methylation of histone lysine residues, including H3K9me3, because of inhibition of histone demethylases by 2-hydroxyglutarate. Here, we evaluated H3K9me3 and its association with IDH mutations in 284 gliomas. Trimethylation of H3K9 was significantly associated with IDH mutations in oligodendrogliomas. Moreover, 72% of World Health Organization grade II and 65% of grade III oligodendrogliomas showed combined H3K9me3 positivity and 1p19q codeletion. In astrocytic tumors, H3K9me3 positivity was found in all grades of tumors; it showed a significant relationship with IDH mutational status in grade II astrocytomas but not in grade III astrocytomas or glioblastomas. Finally, H3K9me3-positive grade II oligodendrogliomas, but not other tumor subtypes, showed improved overall survival compared with H3K9me3-negative cases. These results suggest that repressive trimethylation of H3K9 in gliomas may occur in a context-dependent manner and is associated with IDH mutations in oligodendrogliomas but may be differently regulated in high-grade astrocytic tumors. Furthermore, H3K9me3 may define a subset of grade II oligodendrogliomas with better overall survival. Our results suggest variable roles for IDH mutations in the pathogenesis of oligodendrogliomas versus astrocytic tumors.
    03/2013; DOI:10.1097/NEN.0b013e3182898113
  • Sriram Venneti, Craig B Thompson
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    ABSTRACT: Cancer metabolism and epigenetics are two relatively new areas of cancer research. Recent years have seen an explosion of studies implicating either altered tumor metabolism or epigenetic mechanisms in the pathogenesis or maintenance of brain tumors. A new paradigm is emerging in cancer biology that represents a convergence of these themes, the metabolic regulation of epigenetics. We discuss this interrelationship in the context of two metabolic enzymes that can influence the pathogenesis of gliomas by altering the epigenetic state. The first of these enzymes is isocitrate dehydrogenase 1 (IDH1), which is mutated in secondary glioblastomas and ∼70% of grade II/III astrocytomas and oligodendrogliomas. Mutant IDH1 results in the production of a metabolite 2-hydroxyglutarate (2-HG) that can inhibit DNA and histone demethylating enzymes resulting in the glioma-CpG island phenotype (G-CIMP) and increased histone methylation marks. Pyruvate kinase M2 (PKM2), an enzyme that plays a critical role in the glycolytic pathway, is a second example of a metabolic enzyme that can affect histone modifications. In epidermal growth factor receptor (EGFR)-driven glioblastoma, PKM2 translocates to the nucleus and phosphorylates histone 3 at threonine 11 (H3-T11). This causes dissociation of HDAC3 from the CCND1 (Cyclin D1) and c-MYC promoters and subsequent histone acetylation, leading to transcription of Cyclin-D1 and c-MYC, and subsequent cell proliferation. Modification of the epigenetic state by alterations in metabolic enzymes is a novel phenomenon that contributes to the pathogenesis of gliomas and may help in the identification of new therapeutic targets.
    Brain Pathology 03/2013; 23(2):217-21. DOI:10.1111/bpa.12022 · 4.35 Impact Factor
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    ABSTRACT: High-grade astrocytomas (HGAs), corresponding to WHO grades III (AA) and IV (GBM), are biologically aggressive and their molecular classification is increasingly relevant to clinical management. PDGFRA amplification is common in HGAs, although its prognostic significance remains unclear. Using fluorescence in situ hybridization (FISH), the most sensitive technique for detecting PDGFRA copy number gains, we determined PDGFRA amplification status in 123 pediatric and 263 adult HGAs. A range of PDGFRA FISH patterns were identified and cases were scored as non-amplified (normal and polysomy) or amplified (low-level and high-level). PDGFRA amplification was frequent in pediatric (29.3%) and adult (20.9%) tumors. Amplification was not prognostic in pediatric HGAs. In adult tumors diagnosed initially as GBM, the presence of combined PDGFRA amplification and IDH1(R132H) mutation was a significant independent prognostic factor (p=0.01). In HGAs, PDGFRA amplification is common and can manifest as high-level and focal or low-level amplifications. Our data indicate that the latter is more prevalent than previously reported with copy number averaging techniques. To our knowledge, this is the largest survey of PDGFRA status in adult and pediatric HGAs and suggests PDGFRA amplification increases with grade and is associated with a less favorable prognosis in IDH1 mutant de novo GBMs.
    Brain Pathology 02/2013; 23(5). DOI:10.1111/bpa.12043 · 4.35 Impact Factor

Publication Stats

768 Citations
274.33 Total Impact Points

Institutions

  • 2015
    • Institut Claudius Regaud
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 2013–2015
    • Memorial Sloan-Kettering Cancer Center
      • Division of Cancer Biology & Genetics
      New York, New York, United States
    • The Children's Hospital of Philadelphia
      Filadelfia, Pennsylvania, United States
  • 2014
    • Keck School of Medicine USC
      Los Angeles, California, United States
  • 2009–2014
    • University of Pennsylvania
      • • Department of Pathology and Laboratory Medicine
      • • Department of Radiation Oncology
      • • Department of Pathology
      • • Department of Medicine
      Philadelphia, Pennsylvania, United States
  • 2011–2012
    • William Penn University
      Filadelfia, Pennsylvania, United States
  • 2010–2011
    • Hospital of the University of Pennsylvania
      • Department of Pathology and Laboratory Medicine
      Philadelphia, PA, United States
  • 2007–2008
    • University of Pittsburgh
      • Department of Pathology
      Pittsburgh, Pennsylvania, United States
    • National Institute of Radiological Sciences
      • Molecular Imagining Center
      Chiba-shi, Chiba-ken, Japan