Philip J Tofilon

National Institutes of Health, 베서스다, Maryland, United States

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Publications (181)1113.21 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Glioblastoma multiforme (GBM) continues to be the most frequently diagnosed and lethal primary brain tumor. Adjuvant chemo-radiotherapy remains the standard of care following surgical resection. In this study, using reverse phase protein arrays (RPPAs), we assessed the biological effects of radiation on signaling pathways to identify potential radiosensitizing molecular targets. We examined levels of 172 phosphorylated and non-phosphorylated proteins under conditions of Ionizing radiation (IR) in patient derived GBM stem cells and established U251, U87 GBM cell lines in vitro and in an in vivo orthotropic mouse model. We identified subsets of proteins with clearly concordant/discordant behavior between GBM cells in vitro and in vivo. In general, molecules involved in anti-apoptotic, cell-cycle, survival pathways, tumor metastasis and DNA repair were affected. Comparing in vivo and in vitro samples after IR, 9 proteins were commonly elevated; phospho(p)-STAT3, CDC2, CyclinB1, BAX, pEIF4BP1, pAKT, pRB, pMEK1, and FOXM1. Conversely, 4 other proteins were commonly decreased; pPRKCA, pPRKCD, pNDRG1 and pRPS6. Recent evidence of FOXM1 as a master regulator of metastasis and its important role in maintaining neural, progenitor, and GBM stem cells intrigued us to validate it as a radiosensitizing target. We show high expression of FOXM1 across different patient derived stem cells. When GBM stem cells (NSC11, GBAM1) were differentiated in serum, we observed a decrease in FOXM1 levels, attaining more differentiation markers. In both differentiated and un-differentiated GBM stem cells, treatment with IR resulted in an increase of FOXM1 expression. However, inhibition of FOXM1 was only seen to have an effect on un-differentiated GBM stem cells, and resulted in reduced cell viability, a significant reduction in clonogenicity, and anchorage-independent growth, along with enhanced radiosenstivity with IR. Importantly, the combination of IR with FOXM1 inhibition showed these same effects irrespective of serum-differentiation. These results clearly suggest, inhibition of FOXM1 leads to radiosensitization. Since GBM stem cells, which comprise a subpopulation of tumor cells, maybe responsible for therapeutic resistance, we show that FOXM1 inhibition stands as a potential cancer stem-cell specific chemo-radio therapeutic target for GBM. Citation Format: Uday Bhanu Maachani, Anita T. Tandle, Uma Shankavaram, Tamalee Meushaw, Philip J. Tofilon, Kevin A. Camphausen. Profiling signaling networks using reverse phase protein arrays: validating FOXM1 as a potential target to radiosensitize glioblastoma (GBM) stem cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 849. doi:10.1158/1538-7445.AM2014-849
    Cancer Research 10/2014; doi: 10.1158/1538-7445.AM2014-849. DOI:10.1158/1538-7445.AM2014-849 · 9.28 Impact Factor
  • Anita T. Tandle · Philip Tofilon · Kevin Camphausen
    Cancer Research 10/2014; 74(19 Supplement):4906-4906. DOI:10.1158/1538-7445.AM2014-4906 · 9.28 Impact Factor
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    ABSTRACT: Background The mammalian target of rapamycin (mTOR) has been suggested as a target for radiosensitization. Given that radiotherapy is a primary treatment modality for glioblastoma (GBM) and that mTOR is often dysregulated in GBM, the goal of this study was to determine the effects of AZD2014, a dual mTORC1/2 inhibitor, on the radiosensitivity of GBM stem-like cells (GSCs).MethodsmTORC1 and mTORC2 activities were defined by immunoblot analysis. The effects of this mTOR inhibitor on the in vitro radiosensitivity of GSCs were determined using a clonogenic assay. DNA double strand breaks were evaluated according to γH2AX foci. Orthotopic xenografts initiated from GSCs were used to define the in vivo response to AZD2014 and radiation.ResultsExposure of GSCs to AZD2014 resulted in the inhibition of mTORC1 and 2 activities. Based on clonogenic survival analysis, addition of AZD2014 to culture media 1 hour before irradiation enhanced the radiosensitivity of CD133+ and CD15+ GSC cell lines. Whereas AZD2014 treatment had no effect on the initial level of γH2AX foci, the dispersal of radiation-induced γH2AX foci was significantly delayed. Finally, the combination of AZD2014 and radiation delivered to mice bearing GSC-initiated orthotopic xenografts significantly prolonged survival as compared with the individual treatments.Conclusions These data indicate that AZD2014 enhances the radiosensitivity of GSCs both in vitro and under orthotopic in vivo conditions and suggest that this effect involves an inhibition of DNA repair. Moreover, these results suggest that this dual mTORC1/2 inhibitor may be a radiosensitizer applicable to GBM therapy.
    Neuro-Oncology 12/2013; 16(1). DOI:10.1093/neuonc/not139 · 5.29 Impact Factor
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    ABSTRACT: Exosomes are nanometer-sized lipid vesicles released ubiquitously by cells, which have been shown to have a normal physiological role, as well as influence the tumor microenvironment and aid metastasis. Recent studies highlight the ability of exosomes to convey tumor-suppressive and oncogenic mRNAs, microRNAs, and proteins to a receiving cell, subsequently activating downstream signaling pathways and influencing cellular phenotype. Here, we show that radiation increases the abundance of exosomes released by glioblastoma cells and normal astrocytes. Exosomes derived from irradiated cells enhanced the migration of recipient cells, and their molecular profiling revealed an abundance of molecules related to signaling pathways important for cell migration. In particular, connective tissue growth factor (CTGF) mRNA and insulin-like growth factor binding protein 2 (IGFBP2) protein levels were elevated, and coculture of nonirradiated cells with exosomes isolated from irradiated cells increased CTGF protein expression in the recipient cells. Additionally, these exosomes enhanced the activation of neurotrophic tyrosine kinase receptor type 1 (TrkA), focal adhesion kinase, Paxillin, and proto-oncogene tyrosine-protein kinase Src (Src) in recipient cells, molecules involved in cell migration. Collectively, our data suggest that radiation influences exosome abundance, specifically alters their molecular composition, and on uptake, promotes a migratory phenotype.
    Translational oncology 12/2013; 6(6):638-48. DOI:10.1593/tlo.13640 · 3.40 Impact Factor
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    ABSTRACT: Radiotherapy remains a primary treatment modality for pancreatic carcinoma, a tumor characterized by aberrant mTOR activity. Given mTOR's regulatory role in gene translation, in this study we defined the effects of the clinically relevant, ATP-competitive mTOR inhibitor, INK128 on the radiosensitivity of pancreatic carcinoma cell lines. Clonogenic survival was used to determine the effects of INK128 on in vitro radiosensitivity on 3 pancreatic carcinoma cell lines and a normal fibroblast cell line with mTOR activity defined using immunoblots. DNA double strand breaks were evaluated according to γH2AX foci. The influence of INK128 on radiation-induced gene translation was determined by microarray analysis of polysome-bound mRNA. Leg tumor xenografts grown from pancreatic carcinoma cells were evaluated for mTOR activity, eIF4F cap complex formation and tumor growth delay. INK128, while inhibiting mTOR activity in each of the cell lines, enhanced the in vitro radiosensitivity of the pancreatic carcinoma cells, but had no effect on normal fibroblasts. The dispersal of radiation-induced γH2AX foci was inhibited in pancreatic carcinoma cells by INK128 as were radiation-induced changes in gene translation. Treatment of mice with INK128 resulted in an inhibition of mTOR activity as well as cap-complex formation in tumor xenografts. Whereas INK128 alone had no effect of tumor growth rate, it enhanced the tumor growth delay induced by single and fractionated doses of radiation. These results indicate that mTOR inhibition induced by INK128 enhances the radiosensitivity of pancreatic carcinoma cells and suggest that this effect involves the inhibition of DNA repair.
    Clinical Cancer Research 11/2013; 20(1). DOI:10.1158/1078-0432.CCR-13-2136 · 8.19 Impact Factor
  • International Journal of Radiation OncologyBiologyPhysics 10/2013; 87(2):S650. DOI:10.1016/j.ijrobp.2013.06.1722 · 4.18 Impact Factor
  • Cancer Research 08/2013; 73(8 Supplement):1584-1584. DOI:10.1158/1538-7445.AM2013-1584 · 9.28 Impact Factor
  • Barbara H. Rath · Kevin Camphausen · Philip J. Tofilon
    Cancer Research 08/2013; 73(8 Supplement):2609-2609. DOI:10.1158/1538-7445.AM2013-2609 · 9.28 Impact Factor
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    ABSTRACT: Glioblastoma multiforme (GBM) is the most common primary brain tumour in the United States of America (USA) with a median survival of approximately 14months. Low survival rates are attributable to the aggressiveness of GBM and a lack of understanding of the molecular mechanisms underlying GBM. The disruption of signalling pathways regulated either directly or indirectly by protein kinases is frequently observed in cancer cells and thus the development of inhibitors of specific kinases has become a major focus of drug discovery in oncology. To identify protein kinases required for the survival of GBM we performed a siRNA-based RNAi screen focused on the human kinome in GBM. Inhibition of the polo-like kinase 1 (PLK1) induced a reduction in the viability in two different GBM cell lines. To assess the potential of inhibiting PLK1 as a treatment strategy for GBM we examined the effects of a small molecule inhibitor of PLK1, GSK461364A, on the growth of GBM cells. PLK1 inhibition arrested cells in the mitotic phase of the cell cycle and induced cell kill by mitotic catastrophe. GBM engrafts treated with GSK461364A showed statistically significant inhibition of tumour growth. Further, exposure of different GBM cells to RNAi or GSK461364A prior to radiation resulted in an increase in their radiosensitivity with dose enhancement factor ranging from 1.40 to 1.53 with no effect on normal cells. As a measure of DNA double strand breaks, γH2AX levels were significantly higher in the combined modality as compared to the individual treatments. This study suggests that PLK1 is an important therapeutic target for GBM and can enhance radiosensitivity in GBM.
    European journal of cancer (Oxford, England: 1990) 06/2013; 49(14). DOI:10.1016/j.ejca.2013.05.013 · 4.82 Impact Factor
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    ABSTRACT: The mechanistic target of rapamycin (mTOR) is a critical kinase in the regulation of gene translation and has been suggested as a potential target for radiosensitization. The goal of this study was to compare the radiosensitizing activities of the allosteric mTOR inhibitor rapamycin with that of the competitive mTOR inhibitor PP242. On the basis of immunoblot analyses, whereas rapamycin only partially inhibited mTOR complex 1 (mTORC1) activity and had no effect on mTOR complex 2 (mTORC2), PP242 inhibited the activity of both mTOR-containing complexes. Irradiation alone had no effect on mTORC1 or mTORC2 activity. Clonogenic survival was used to define the effects of the mTOR inhibitors on in vitro radiosensitivity. In the two tumor cell lines evaluated, PP242 treatment 1 hour before irradiation increased radiosensitivity, whereas rapamycin had no effect. Addition of PP242 after irradiation also enhanced the radiosensitivity of both tumor lines. To investigate the mechanism of radiosensitization, the induction and repair of DNA double-strand breaks were evaluated according γH2AX foci. PP242 exposure did not influence the initial level of γH2AX foci after irradiation but did significantly delay the dispersal of radiation-induced γH2AX foci. In contrast to the tumor cell lines, the radiosensitivity of a normal human fibroblast cell line was not influenced by PP242. Finally, PP242 administration to mice bearing U251 xenografts enhanced radiation-induced tumor growth delay. These results indicate that in a preclinical tumor model PP242 enhances tumor cell radiosensitivity both in vitro and in vivo and suggest that this effect involves an inhibition of DNA repair.
    Translational oncology 06/2013; 6(3):355-62. DOI:10.1593/tlo.13163 · 3.40 Impact Factor
  • Thomas J. Hayman · Tamalee Kramp · Kevin Camphausen · Philip J. Tofilon
    Cancer Research 04/2013; 73(8 Supplement):69-69. DOI:10.1158/1538-7445.AM2013-69 · 9.28 Impact Factor
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    ABSTRACT: Glioblastomas (GBMs) are characterized as highly invasive; the contribution of GBM stem-like cells (GSCs) to the invasive phenotype, however, has not been completely defined. Towards this end, we have defined the invasion potential of CD133+ GSCs and their differentiated CD133- counterparts grown under standard in vitro conditions and in co-culture with astrocytes. Using a trans-well assay, astrocytes or astrocyte conditioned media in the bottom chamber significantly increased the invasion of GSCs yet had no effect on CD133- cells. In addition, a monolayer invasion assay showed that the GSCs invaded farther into an astrocyte monolayer than their differentiated progeny. Gene expression profiles were generated from two GSC lines grown in trans-well culture with astrocytes in the bottom chamber or directly in contact with astrocyte monolayers. In each co-culture model, genes whose expression was commonly increased in both GSC lines involved cell movement and included a number of genes that have been previously associated with tumor cell invasion. Similar gene expression modifications were not detected in CD133- cells co-cultured under the same conditions with astrocytes. Finally, evaluation of the secretome of astrocytes grown in monolayer identified a number of chemokines and cytokines associated with tumor cell invasion. These data suggest that astrocytes enhance the invasion of CD133+ GSCs and provide additional support for a critical role of brain microenvironment in the regulation of GBM biology.
    PLoS ONE 01/2013; 8(1):e54752. DOI:10.1371/journal.pone.0054752 · 3.23 Impact Factor
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    Jenna Kahn · Philip J Tofilon · Kevin Camphausen
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    ABSTRACT: As the incidence of cancer continues to rise, the use of radiotherapy has emerged as a leading treatment modality. Preclinical models in radiation oncology are essential tools for cancer research and therapeutics. Various model systems have been used to test radiation therapy, including in vitro cell culture assays as well as in vivo ectopic and orthotopic xenograft models. This review aims to describe such models, their advantages and disadvantages, particularly as they have been employed in the discovery of molecular targets for tumor radiosensitization. Ultimately, any model system must be judged by its utility in developing more effective cancer therapies, which is in turn dependent on its ability to simulate the biology of tumors as they exist in situ. Although every model has its limitations, each has played a significant role in preclinical testing. Continued advances in preclinical models will allow for the identification and application of targets for radiation in the clinic.
    Radiation Oncology 12/2012; 7(1):223. DOI:10.1186/1748-717X-7-223 · 2.36 Impact Factor
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    ABSTRACT: The increasing availability and maturity of DNA microarray technology has led to an explosion of cancer profiling studies for identifying cancer biomarkers, and predicting treatment response. Uncovering complex relationships, however, remains the most challenging task as it requires compiling and efficiently querying data from various sources. Here, we describe the Stress Response Array Profiler (StRAP), an open-source, web-based resource for storage, profiling, visualization, and sharing of cancer genomic data. StRAP houses multi-cancer microarray data with major emphasis on radiotherapy studies, and takes a systems biology approach towards the integration, comparison, and cross-validation of multiple cancer profiling studies. The database is a comprehensive platform for comparative analysis of gene expression data. For effective use of arrays, we provide user-friendly and interactive visualization tools that can display the data and query results. StRAP is web-based, platform-independent, and freely accessible at http://strap.nci.nih.gov/.
    PLoS ONE 12/2012; 7(12):e51693. DOI:10.1371/journal.pone.0051693 · 3.23 Impact Factor
  • J. Kahn · T.J. Hayman · K. Camphausen · P.J. Tofilon
    International Journal of Radiation OncologyBiologyPhysics 11/2012; 84(3):S697. DOI:10.1016/j.ijrobp.2012.07.1863 · 4.18 Impact Factor
  • Thomas J. Hayman · Heekyong Bae · Kevin Camphausen · Philip J. Tofilon
    Cancer Research 06/2012; 72(8 Supplement):5727-5727. DOI:10.1158/1538-7445.AM2012-5727 · 9.28 Impact Factor
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    ABSTRACT: A core component in the cellular response to radiation occurs at the level of translational control of gene expression. Because a critical element in translation control is the availability of the initiation factor eIF4E, which selectively enhances the cap-dependent translation of mRNAs, we investigated a regulatory role for eIF4E in cellular radiosensitivity. eIF4E silencing enhanced the radiosensitivity of tumor cell lines but not normal cells. Similarly, pharmacologic inhibition of eIF4E with ribavirin also enhanced tumor cell radiosensitivity. eIF4E attenuation did not affect cell-cycle phase distribution or radiation-induced apoptosis, but it delayed the dispersion of radiation-induced γH2AX foci and increased the frequency of radiation-induced mitotic catastrophe. Radiation did not affect 4E-BP1 phosphorylation or cap-complex formation but it increased eIF4E binding to more than 1,000 unique transcripts including many implicated in DNA replication, recombination, and repair. Taken together, our findings suggest that eIF4E represents a logical therapeutic target to increase tumor cell radiosensitivity.
    Cancer Research 03/2012; 72(9):2362-72. DOI:10.1158/0008-5472.CAN-12-0329 · 9.28 Impact Factor
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    ABSTRACT: Vosaroxin is a first in class naphthyridine analog structurally related to quinolone antibacterials, that intercalates DNA and inhibits topoisomerase II. Vosaroxin is not a P-glycoprotein receptor substrate and its activity is independent of p53, thus evading common drug resistance mechanisms. To evaluate vosaroxin as a clinically applicable radiation sensitizer, we investigated its effects on tumor cell radiosensitivity in vitro and in vivo. Vosaroxin's effect on post-irradiation sensitivity of U251, DU145, and MiaPaca-2 cells was assessed by clonogenic assay. Subsequent mechanistic and in vivo studies were performed with U251 cells. Cell cycle distribution and G2 checkpoint integrity was analyzed by flow cytometry. DNA damage and repair was evaluated by a high throughput gamma-H2AX assay. Apoptosis was assessed by flow cytometry. Mitotic catastrophe was assessed by microscopic evidence of fragmented nuclei by immunofluorescence. In vivo radiosensitization was measured by subcutaneous tumor growth delay. 50-100 nmol/L treatment with vosaroxin resulted in radiosensitization of all 3 cell lines tested with a dose enhancement factor of 1.20 to 1.51 measured at a surviving fraction of 0.1. The maximal dose enhancement was seen in U251 cells treated with 75 nmol/L vosaroxin (DEF 1.51). Vosaroxin exposure did not change cell cycle distribution prior to irradiation nor alter G2 checkpoint integrity after irradiation. No difference was seen in the apoptotic fraction regardless of drug or radiation treatment. The number of cells in mitotic catastrophe was significantly greater in irradiated cells treated with vosaroxin than cells receiving radiation only at 72 hr (p = 0.009). Vosaroxin alone did not significantly increase mitotic catastrophe over control (p = 0.53). Cells treated with vosaroxin and radiation maintained significantly higher gamma-H2AX levels than cells treated with vehicle control (p = 0.014), vosaroxin (p = 0.042), or radiation alone (p = 0.039) after 24 hr. In vivo tumor growth delay was 1.5 days for vosaroxin alone (IV 10 mg/kg), 1.0 days for radiation (3 Gy) alone, and 8.6 days for the group treated with vosaroxin 4 hours prior to radiation. Vosaroxin enhanced tumor cell radiosensitivity in vitro and in vivo. The mechanism appears to be related to inhibition of DNA repair and increased mitotic catastrophe.
    Radiation Oncology 02/2012; 7:26. DOI:10.1186/1748-717X-7-26 · 2.36 Impact Factor
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    Whoon Jong Kil · Philip J Tofilon · Kevin Camphausen
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    ABSTRACT: Glioblastoma multiforme (GBM) is among the most lethal of all human tumors, with frequent local recurrences after radiation therapy (RT). The mechanism accounting for such a recurrence pattern is unclear. It has classically been attributed to local recurrence of treatment-resistant cells. However, accumulating evidence suggests that additional mechanisms exist that involve the migration of tumor or tumor stem cells from other brain regions to tumor bed. VEGFs are well-known mitogens and can be up-regulated after RT. Here, we examine the effect of irradiation-induced VEGF on glioma cell motility. U251 and LN18 cell lines were used to generate irradiated-conditioned medium (IR-CM). At 72 h after irradiation, the supernatants were harvested. VEGF level in IR-CM was quantified by ELISA, and expression levels for VEGF mRNA were detected by RT-PCR. In vitro cancer cell motility was measured in chambers coated with/without Matrigel and IR-CM as a cell motility enhancer and a VEGF antibody as a neutralizer of VEGF bioactivity. Immunoblots were performed to evaluate the activity of cell motility-related kinases. Proliferation of GBM cells after treatment was measured by flow cytometry. Irradiation increased the level of VEGF mRNA that was mitigated by pre-RT exposure to Actinomycin D. U251 glioma cell motility (migration and invasion) was enhanced by adding IR-CM to un-irradiated cells (174.9 ± 11.4% and 334.2 ± 46% of control, respectively). When we added VEGF antibody to IR-CM, this enhanced cell motility was negated (110.3 ± 12.0% and 105.7 ± 14.0% of control, respectively). Immunoblot analysis revealed that IR-CM increased phosphorylation of VEGF receptor-2 (VEGFR2) secondary to an increase in VEGF, with a concomitant increase of phosphorylation of the downstream targets (Src and FAK). Increased phosphorylation was mitigated by adding VEGF antibody to IR-CM. There was no difference in the mitotic index of GBM cells treated with and without IR-CM and VEGF. These results indicate that cell motility can be enhanced by conditioned medium from irradiated cells in vitro through stimulation of VEGFR2 signaling pathways and suggest that this effect involves the secretion of radiation-induced VEGF, leading to an increase in glioma cell motility.
    Radiation Oncology 02/2012; 7(1):25. DOI:10.1186/1748-717X-7-25 · 2.36 Impact Factor
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    ABSTRACT: Brain tumor xenografts initiated from glioblastoma (GBM) CD133(+) tumor stem-like cells (TSCs) are composed of TSC and non-TSC subpopulations, simulating the phenotypic heterogeneity of GBMs in situ. Given that the discrepancies between the radiosensitivity of GBM cells in vitro and the treatment response of patients suggest a role for the microenvironment in GBM radioresistance, we compared the response of TSCs and non-TSCs irradiated under in vitro and orthotopic conditions. As a measure of radioresponse determined at the individual cell level, γH2AX and 53BP1 foci were quantified in CD133(+) cells and their differentiated (CD133(-)) progeny. Under in vitro conditions, no difference was detected between CD133(+) and CD133(-) cells in foci induction or dispersal after irradiation. However, irradiation of orthotopic xenografts initiated from TSCs resulted in the induction of fewer γH2AX and 53BP1 foci in CD133(+) cells compared to their CD133(-) counterparts within the same tumor. Xenograft irradiation resulted in a tumor growth delay of approximately 7 days with a corresponding increase in the percentage of CD133(+) cells at 7 days after radiation, which persisted to the onset of neurologic symptoms. These results suggest that, although the radioresponse of TSCs and non-TSCs does not differ under in vitro growth conditions, CD133(+) cells are relatively radioresistant under intracerebral growth conditions. Whereas these findings are consistent with the suspected role for TSCs as a determinant of GBM radioresistance, these data also illustrate the dependence of the cellular radioresistance on the brain microenvironment.
    Neoplasia (New York, N.Y.) 02/2012; 14(2):150-8. DOI:10.1593/neo.111794 · 5.40 Impact Factor

Publication Stats

5k Citations
1,113.21 Total Impact Points

Institutions

  • 2005–2013
    • National Institutes of Health
      • Branch of Radiation Oncology
      베서스다, Maryland, United States
    • NCI-Frederick
      Фредерик, Maryland, United States
  • 2003–2013
    • National Cancer Institute (USA)
      • Radiation Oncology Branch
      베서스다, Maryland, United States
  • 2012
    • National Cancer Institute
      Μπογκοτά, Bogota D.C., Colombia
  • 2008–2011
    • Moffitt Cancer Center
      • Department of Drug Discovery
      Tampa, Florida, United States
  • 2007–2009
    • University of South Florida
      Tampa, Florida, United States
  • 1985–2002
    • University of Texas MD Anderson Cancer Center
      • • Department of Experimental Radiation Oncology
      • • Department of NeuroSurgery
      Houston, TX, United States
  • 1997–2001
    • University of Houston
      Houston, Texas, United States
  • 1982–1992
    • University of California, San Francisco
      • • Department of Neurological Surgery
      • • Division of Hospital Medicine
      San Francisco, California, United States