Donald M O'Rourke

Publications of Donald M O'Rourke

• Use of magnetic perfusion-weighted imaging to determine epidermal growth factor receptor variant III expression in glioblastoma.

  Authors: Elana S Tykocinski, Ryan A Grant, Gurpreet S Kapoor, Jaroslaw Krejza, Leif-Erik Bohman, Timothy A Gocke, Sanjeev Chawla, Casey H Halpern, Joanna Lopinto, Elias R Melhem, Donald M O'Rourke

  Neuro-oncology. 04/2012;

  Identification of the epidermal growth factor receptor variant III (EGFRvIII) mutation in glioblastoma has become increasingly relevant in the optimization of therapy. Traditionally, determination ofIdentification of the epidermal growth factor receptor variant III (EGFRvIII) mutation in glioblastoma has become increasingly relevant in the optimization of therapy. Traditionally, determination of tumor EGFRvIII-expression has relied on tissue-based diagnostics. Here, we assess the accuracy of magnetic resonance perfusion-weighted imaging (MR-PWI) in discriminating the EGFRvIII-expressing glioblastoma subtype. We analyzed RNA from 132 primary human glioblastoma tissue samples by reverse-transcription polymerase chain reaction (RT-PCR) for the EGFRvIII and EGFR wild-type mutations and by quantitative RT-PCR for expression of vascular endothelial growth factor (VEGF). Concurrently, 3 independent observers reviewed preoperative 1.5-Tesla (T)/SE or 3.0-Tesla (T)/GE MR perfusion images to determine the maximum relative tumor blood volume (rTBV) of each of these tumors. EGFRvIII-expressing glioblastomas showed significantly higher rTBV, compared with those tumors lacking EGFRvIII expression. This association was observed in both the 1.5T/SE (P = .000) and 3.0T/GE (P = .001) cohorts. By logistic regression analysis, combining the 2 MR system cohorts, rTBV was a very strong predictor of EGFRvIII mutation (odds ratio [rTBV] = 2.70; P = .000; McFadden's ρ(2) = 0.23). Furthermore, by receiver-operating characteristic curve analysis, rTBV discriminated EGFRvIII with very high accuracy (A(z) = 0.81). In addition, we found that VEGF upregulation was associated, although without reaching statistical significance, with EGFRvIII expression (P = .16) and with increased rTBV (F-ratio = 2.71; P = .102). These trends suggest that VEGF-mediated angiogenesis may be a potential mediator of angiogenesis to increase perfusion in EGFRvIII-expressing glioblastomas, but there are likely several other contributing factors. This study demonstrates the potential to use rTBV, a MR-PWI-derived parameter, as a noninvasive surrogate of the EGFRvIII mutation.

• Clinically silent somatotroph adenomas are common.

  Authors: Alisha N Wade, Jennifer Baccon, M Sean Grady, Kevin D Judy, Donald M O'Rourke, Peter J Snyder

  European journal of endocrinology / European Federation of Endocrine Societies. 07/2011; 165(1):39-44.

  Somatotroph adenomas are typically recognized when they secrete GH excessively and cause acromegaly. Both 'silent' somatotroph adenomas (immunohistochemical evidence of GH excess without biochemicalSomatotroph adenomas are typically recognized when they secrete GH excessively and cause acromegaly. Both 'silent' somatotroph adenomas (immunohistochemical evidence of GH excess without biochemical or clinical evidence) and 'clinically silent' somatotroph adenomas (immunohistochemical and biochemical evidence but no clinical evidence) have occasionally been reported. The relative frequency of each presentation is unknown. The goal of this study was, therefore, to determine the frequency of clinically silent somatotroph adenomas, a group that is potentially recognizable in vivo. We retrospectively identified 100 consecutive patients who had surgically excised and histologically confirmed pituitary adenomas. Each pituitary adenoma was classified immunohistochemically by pituitary cell type. Somatotroph adenomas were further classified as 'classic' (obvious clinical features of acromegaly and elevated serum IGF1), 'subtle' (subtle clinical features of acromegaly and elevated IGF1), 'clinically silent' (no clinical features of acromegaly but elevated IGF1), and 'silent' (no clinical features of acromegaly and normal IGF1). Of the 100 consecutive pituitary adenomas, 29% were gonadotroph/glycoprotein, 24% somatotroph, 18% null cell, 15% corticotroph, 6% lactotroph, 2% thyrotroph, and 6% not classifiable. Of the 24 patients with somatotroph adenomas, classic accounted for 45.8%, subtle 16.7%, clinically silent 33.3%, and silent 4.2%. Clinically silent somatotroph adenomas are more common than previously appreciated, representing one-third of all somatotroph adenomas. IGF1 should be measured in all patients with a sellar mass, because identification of a mass as a somatotroph adenoma expands the therapeutic options and provides a tumor marker to monitor treatment.

• Magnetic resonance perfusion-weighted imaging defines angiogenic subtypes of oligodendroglioma according to 1p19q and EGFR status.

  Authors: Gurpreet S Kapoor, Timothy A Gocke, Sanjeev Chawla, Robert G Whitmore, Ali Nabavizadeh, Jaroslaw Krejza, Joanna Lopinto, Justin Plaum, Eileen Maloney-Wilensky, Harish Poptani, Elias R Melhem, Kevin D Judy, Donald M O'Rourke

  Journal of neuro-oncology. 06/2009; 92(3):373-86.

  1p19q LOH has been shown to predict radio- and chemosensitivity and prolonged survival in oligodendrogliomas (OLs). We have recently shown that magnetic resonance perfusion-weighted imaging (MR-PWI)1p19q LOH has been shown to predict radio- and chemosensitivity and prolonged survival in oligodendrogliomas (OLs). We have recently shown that magnetic resonance perfusion-weighted imaging (MR-PWI) may be useful in predicting the histopathological grade or cytogenetic type of oligodendroglial neoplasms. MR-PWI allows noninvasive determination of relative tumor blood volume (rTBV), which may reflect the degree of neoplastic angiogenesis and metabolism. The present study was aimed to correlate rTBV to the angiogenic markers and EGFR expression in oligodendroglial tumors with 1p/19q LOH or 1p LOH (Group 1) and 1p19q intact alleles or 19q LOH (Group 2), respectively. In WHO grade II neoplasms, Group 1 showed significantly greater rTBV than Group 2 (P = 0.013). However, the differences between Group 1 and Group 2 were not significant in grade III tumors. Probe-based real-time RT-PCR analyses showed that 12% of Group 2 high-grade tumors with intact 1p19q exhibited dramatic EGFR overexpression (designated EGFR-high). Grade III neoplasms showed a significantly higher rTBV than grade II neoplasms. Group 1 tumors showed significantly higher rTBV than Group 2 tumors, independent of the EGFR-high subtype. Real-time RT-PCR analyses showed increased expression of VEGF, CD31 and CD105 in Group 1 tumors as compared to Group 2 tumors, excluding the EGFR-high subtype. Multivariable linear regression analysis showed a significant association of rTBV with 1p19q LOH, and expression of EGFR and VEGF. Therefore, the combined use of extensive molecular profiling and advanced MR imaging modalities may improve the accuracy of tumor grading, provide prognostic information, and has the potential to influence treatment decisions.

• Posttreatment Recurrence of Malignant Brain Neoplasm: Accuracy of Relative Cerebral Blood Volume Fraction in Discriminating Low from High Malignant Histologic Volume Fraction.

  Authors: Emerson L Gasparetto, Mikolaj A Pawlak, Sohil H Patel, Jason Huse, John H Woo, Jaroslaw Krejza, Myrna R Rosenfeld, Donald M O'Rourke, Robert Lustig, Elias R Melhem, Ronald L Wolf

  Radiology. 03/2009; 250(3):887-896.

  Purpose: To determine the accuracy of relative cerebral blood volume (rCBV) fraction for distinguishing high-grade recurrent neoplasm from treatment-related necrosis (TRN) in enhancing massesPurpose: To determine the accuracy of relative cerebral blood volume (rCBV) fraction for distinguishing high-grade recurrent neoplasm from treatment-related necrosis (TRN) in enhancing masses identified on surveillance magnetic resonance (MR) images following treatment for primary or secondary brain neoplasm. Materials and Methods: This institutional review board approved and HIPAA-compliant retrospective study included 30 patients undergoing resection of recurrent enhancing mass appearing after treatment with surgery and radiation, with or without chemotherapy. The enhancing mass volume was manually segmented on three-dimensional T1-weighted images. The rCBV maps were created by using T2-weighted dynamic susceptibility contrast perfusion MR imaging and registered to T1-weighted images, and the fraction of enhancing mass with rCBV above a range of thresholds was calculated. A receiver operating characteristic (ROC) curve was created by calculating sensitivity-specificity pairs at each threshold for rCBV fraction (</=20% or >20%) by using percentage of malignant features at histologic evaluation as the reference criterion. Relationships between rCBV and probability of recurrence were estimated by using logistic regression analysis. Results: ROC analysis showed excellent discriminating accuracy of rCBV fraction (area under the ROC curve, 0.97 +/- 0.03 [standard error]) and high efficiency (93%) with an rCBV threshold of 1.8 times that of normal-appearing white matter. Logistic regression analysis showed that a unit increase of rCBV is associated with a 254-fold increase (95% confidence interval: 43, 1504, P < .001) of the odds that enhanced tissue is recurrence, adjusting for age, treatment, volume of enhancing tissue, and time to suspected recurrence. Conclusion: The fraction of malignant histologic features in enhancing masses recurring after treatment for brain neoplasms can be predicted by using the rCBV fraction, with improved differentiation between recurrent neoplasm and TRN. (c) RSNA, 2009.

  Download

• Role of monocyte chemoattractant protein-1 (MCP-1/CCL2) in migration of neural progenitor cells toward glial tumors.

  Authors: Suresh N Magge, Saafan Z Malik, Nicolas C Royo, H Isaac Chen, Liya Yu, Evan Y Snyder, Donald M O'Rourke, Deborah J Watson

  Journal of neuroscience research. 02/2009;

  Neural progenitor cells (NPCs) have been investigated as potential vehicles for brain tumor therapy because they have been shown to migrate toward central nervous system gliomas and can beNeural progenitor cells (NPCs) have been investigated as potential vehicles for brain tumor therapy because they have been shown to migrate toward central nervous system gliomas and can be genetically engineered to deliver cytotoxic agents to tumors. The mechanisms that regulate migration of NPCs to tumors are not fully understood. By means of microarray analysis, polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry, we found that monocyte chemoattractant protein-1 (MCP-1/CCL-2) was expressed in experimental brain tumor cells in vivo and in vitro. CCR2, the receptor for MCP-1, was expressed on C17.2 NPCs. We used a modified Boyden chamber assay and found increased migration of NPCs in vitro in response to MCP-1. By means of an in vivo model for NPC migration, we found evidence of NPC migration toward areas of MCP-1 infusion in rat brains. An understanding of NPC migration mechanisms may be used to enhance delivery of cytotoxic agents to brain tumor cells. (c) 2009 Wiley-Liss, Inc.

• Role of Proton Magnetic Resonance Spectroscopy in Differentiating Oligodendrogliomas from Astrocytomas.

  Authors: Sanjeev Chawla, Laura Oleaga, Sumei Wang, Jaroslaw Krejza, Ronald L Wolf, John H Woo, Donald M O'Rourke, Kevin D Judy, Michael S Grady, Elias R Melhem, Harish Poptani

  Journal of neuroimaging : official journal of the American Society of Neuroimaging. 11/2008;

  ABSTRACT BACKGROUND AND PURPOSE Preoperative differentiation of astrocytomas from oligodendrogliomas is clinically important, as oligodendrogliomas are more sensitive to chemotherapy. The purpose ofABSTRACT BACKGROUND AND PURPOSE Preoperative differentiation of astrocytomas from oligodendrogliomas is clinically important, as oligodendrogliomas are more sensitive to chemotherapy. The purpose of this study was to assess the role of proton magnetic resonance spectroscopy in distinguishing astrocytomas from oligodendrogliomas. METHODS Forty-six patients [astrocytomas (n= 17) and oligodendrogliomas (n= 29)] underwent magnetic resonance imaging and multi voxel proton magnetic resonance spectroscopic imaging before treatment. Peak areas for N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myo-inositol (mI), glutamate/glutamine (Glx), and lipids + lactate (Lip+Lac) were analyzed from voxels that exhibited hyperintensity on fluid-attenuated inversion recovery images and were normalized to Cr from each voxel. The average metabolite/Cr ratios from these voxels were then compared between astrocytomas and oligodendrogliomas. Receiver-operating curve analyses were used as measures of differentiation accuracy of metabolite ratios. A threshold value for a metabolite ratio was estimated by maximizing the sum of sensitivity and specificity. RESULTS A significant difference in mI/Cr was observed between astrocytomas and oligodendrogliomas (.50 +/- .18 vs. 0.66 +/- 0.20, P < .05). Using a threshold value of .56 for mI/Cr ratio, it was possible to differentiate oligodendrogliomas from astrocytomas with a sensitivity of 72.4% and specificity of 76.4%. CONCLUSION These results suggest that mI/Cr might aid in distinguishing oligodendrogliomas from astrocytomas. J Neuroimaging 2008;XX:1-6.

• Differentiation between glioblastomas and solitary brain metastases using diffusion tensor imaging.

  Authors: Sumei Wang, Sungheon Kim, Sanjeev Chawla, Ronald L Wolf, Wei-Guo Zhang, Donald M O'Rourke, Kevin D Judy, Elias R Melhem, Harish Poptani

  NeuroImage. 10/2008;

  The purpose of this study is to determine whether diffusion tensor imaging (DTI) metrics including tensor shape measures such as linear and planar anisotropy coefficients (CL and CP) can helpThe purpose of this study is to determine whether diffusion tensor imaging (DTI) metrics including tensor shape measures such as linear and planar anisotropy coefficients (CL and CP) can help differentiate glioblastomas from solitary brain metastases. Sixty-three patients with histopathologic diagnosis of glioblastomas (22 men, 16 women, mean age 58.4 years) and brain metastases (13 men, 12 women, mean age 56.3 years) were included in this study. Contrast-enhanced T1-weighted, fluid-attenuated inversion recovery (FLAIR) images, fractional anisotropy (FA), apparent diffusion coefficient (ADC), CL and CP maps were co-registered and each lesion was semi-automatically subdivided into four regions: central, enhancing, immediate peritumoral and distant peritumoral. DTI metrics as well as the normalized signal intensity from the contrast-enhanced T1-weighted images were measured from each region. Univariate and multivariate logistic regression analyses were employed to determine the best model for classification. The results demonstrated that FA, CL and CP from glioblastomas were significantly higher than those of brain metastases from all segmented regions (p<0.05), and the differences from the enhancing regions were most significant (p<0.001). FA and CL from the enhancing region had the highest prediction accuracy when used alone with an area under the curve of 0.90. The best logistic regression model included three parameters (ADC, FA and CP) from the enhancing part, resulting in 92% sensitivity, 100% specificity and area under the curve of 0.98. We conclude that DTI metrics, used individually or combined, have a potential as a non-invasive measure to differentiate glioblastomas from metastases.

• Prediction of oligodendroglial tumor subtype and grade using perfusion weighted magnetic resonance imaging.

  Authors: Robert G Whitmore, Jaroslaw Krejza, Gurpreet S Kapoor, Jason Huse, John H Woo, Stephanie Bloom, Joanna Lopinto, Ronald L Wolf, Kevin Judy, Myrna R Rosenfeld, Jaclyn A Biegel, Elias R Melhem, Donald M O'Rourke

  Journal of neurosurgery. 09/2007; 107(3):600-9.

  OBJECT: Treatment of patients with oligodendrogliomas relies on histopathological grade and characteristic cytogenetic deletions of 1p and 19q, shown to predict radio- and chemosensitivity andOBJECT: Treatment of patients with oligodendrogliomas relies on histopathological grade and characteristic cytogenetic deletions of 1p and 19q, shown to predict radio- and chemosensitivity and prolonged survival. Perfusion weighted magnetic resonance (MR) imaging allows for noninvasive determination of relative tumor blood volume (rTBV) and has been used to predict the grade of astrocytic neoplasms. The aim of this study was to use perfusion weighted MR imaging to predict tumor grade and cytogenetic profile in oligodendroglial neoplasms. METHODS: Thirty patients with oligodendroglial neoplasms who underwent preoperative perfusion MR imaging were retrospectively identified. Tumors were classified by histopathological grade and stratified into two cytogenetic groups: 1p or 1p and 19q loss of heterozygosity (LOH) (Group 1), and 19q LOH only on intact alleles (Group 2). Tumor blood volume was calculated in relation to contralateral white matter. Multivariate logistic regression analysis was used to develop predictive models of cytogenetic profile and tumor grade. RESULTS: In World Health Organization Grade II neoplasms, the rTBV was significantly greater (p < 0.05) in Group 1 (mean 2.44, range 0.96-3.28; seven patients) compared with Group 2 (mean 1.69, range 1.27-2.08; seven patients). In Grade III neoplasms, the differences between Group 1 (mean 3.38, range 1.59-6.26; four patients) and Group 2 (mean 2.83, range 1.81-3.76; 12 patients) were not significant. The rTBV was significantly greater (p < 0.05) in Grade III neoplasms (mean 2.97, range 1.59-6.26; 16 patients) compared with Grade II neoplasms (mean 2.07, range 0.96-3.28; 14 patients). The models integrating rTBV with cytogenetic profile and grade showed prediction accuracies of 68 and 73%, respectively. CONCLUSIONS: Oligodendroglial classification models derived from advanced imaging will improve the accuracy of tumor grading, provide prognostic information, and have potential to influence treatment decisions.

• Intraaxial brain masses: MR imaging-based diagnostic strategy--initial experience.

  Authors: Riyadh N Al-Okaili, Jaroslaw Krejza, John H Woo, Ronald L Wolf, Donald M O'Rourke, Kevin D Judy, Harish Poptani, Elias R Melhem

  Radiology. 06/2007; 243(2):539-50.

  PURPOSE: To develop and retrospectively determine the accuracy of a magnetic resonance (MR) imaging strategy to differentiate intraaxial brain masses, with histologic findings or clinical diagnosisPURPOSE: To develop and retrospectively determine the accuracy of a magnetic resonance (MR) imaging strategy to differentiate intraaxial brain masses, with histologic findings or clinical diagnosis as the reference standard. MATERIALS AND METHODS: The study was HIPAA compliant and was approved by the institutional review board. A waiver of informed consent was obtained. A strategy was developed on the basis of conventional MR imaging, diffusion-weighted MR imaging, perfusion MR imaging, and proton MR spectroscopy to classify intraaxial masses as low-grade primary neoplasms, high-grade primary neoplasms, metastatic neoplasms, abscesses, lymphomas, tumefactive demyelinating lesions (TDLs), or encephalitis. The strategy was evaluated by using data from 111 patients (46 women, 65 men; mean age, 48.9 years) with imaging results available on a departmental picture archiving and communication system from a 5-year search period. Bayesian statistics of the strategy elements and three clinical tasks were calculated. RESULTS: Search results identified 44 patients with high-grade and 14 with low-grade primary neoplasms, 24 with abscesses, 12 with lymphoma, 11 with TDLs, five with metastases, and one with encephalitis who had undergone conventional and advanced MR imaging. However, only 40 patients (25 women, 15 men; mean age, 45 years) had undergone all studies and had data to allow completion of the entire strategy. Accuracy, sensitivity, and specificity of the strategy, respectively, were 90%, 97%, and 67% for discrimination of neoplastic from nonneoplastic diseases, 90%, 88%, and 100% for discrimination of high-grade from low-grade neoplasms, and 85%, 84%, and 87% for discrimination of high-grade neoplasms and lymphoma from low-grade neoplasms and nonneoplastic diseases. CONCLUSION: An integrated MR imaging-based strategy, which is accurate in differentiation of several intraaxial brain masses, was proposed.

• EGFR inhibition in glioblastoma cells induces G2/M arrest and is independent of p53.

  Authors: Gurpreet S Kapoor, Antoire Christie, Donald M O'Rourke

  Cancer biology & therapy. 05/2007; 6(4):571-9.

  Mutations involving the TP53 gene are frequently identified in up to 50% of all human tumors, including glioblastomas. Analysis of expression patterns of TP53 in glioblastomas shows that it is mainlyMutations involving the TP53 gene are frequently identified in up to 50% of all human tumors, including glioblastomas. Analysis of expression patterns of TP53 in glioblastomas shows that it is mainly mutated in secondary glioblastomas and is less common in primary GBMs. However, the prognostic significance of TP53 loss of function in astrocytomas has always been controversial. In contrast, EGFR/erbB2 complexes have been implicated in the poor prognosis of several cancers, including glioblastomas. Our previous work showed that transforming phenotypes could be inhibited by interfering with active EGFR/erbB2 complex using mutant erbB2 proteins in wild-type p53 GBM cells. To assess the dependence of EGFR inhibited phenotype on p53, we used three mutant p53 glioblastoma cell lines in the present study and showed that mutant erbB2 can be exploited to inhibit EGFR-mediated oncogenic transformation irrespective of p53 status. Ectopic expression of a mutant erbB2 receptor (T691S) in mutant p53 GBM cells resulted in slower growth rate than empty vector controls. T691S-expressing clones exhibited a more flattened and nontransformed morphology. Consistently, T691S inhibited transformation in soft agar assays and tumor formation in nude mice independent of p53 status. Biochemical analysis showed reduced Akt and GSK-3 alpha/beta, but not p42/44MAPK phosphorylation, in T691S-expressing cells, when compared to parental controls, suggesting the P13-K pathway may be more relevant than MAPK for glial cell transformation. Cell cycle analysis showed reduced cyclin D1 and CDK6 and increased phospho-Cdc-2 (Tyr15) and p15INK4B in erbB2-inhibited cells, suggesting that nonfunctional EGFR/erbB2 complexes exert their inhibitory effects at various stages of the cell cycle to block the progression of cells through G2/M via Akt/GSK-3/Cdc2 pathway. Collectively, these observations provide a basis for receptor-based therapies that disable erbB receptors and inhibit proliferative signals in erbB-expressing human cancers including glioblastomas, regardless of their TP53 status.

• Actinomycotic brain infection: registered diffusion, perfusion MR imaging and MR spectroscopy.

  Authors: Sumei Wang, Ronald L Wolf, John H Woo, Jiongjiong Wang, Donald M O'Rourke, Subhojit Roy, Elias R Melhem, Harish Poptani

  Neuroradiology. 06/2006; 48(5):346-50.

  INTRODUCTION: Actinomycotic brain infection is caused by an organism of the Actinomyces genus. We report here one such case. METHODS: The methods used included coregistered diffusion, perfusion andINTRODUCTION: Actinomycotic brain infection is caused by an organism of the Actinomyces genus. We report here one such case. METHODS: The methods used included coregistered diffusion, perfusion and spectroscopic magnetic resonance (MR) imaging. RESULTS: Decreased apparent diffusion coefficient, markedly elevated fractional anisotropy (FA) and reduced cerebral blood flow were observed. MR spectroscopy demonstrated elevated amino acids, acetate and succinate. CONCLUSION: Elevated FA values may be due to the microstructure of this special brain infection.

• Grading of CNS neoplasms using continuous arterial spin labeled perfusion MR imaging at 3 Tesla.

  Authors: Ronald L Wolf, Jiongjiong Wang, Sumei Wang, Elias R Melhem, Donald M O'Rourke, Kevin D Judy, John A Detre

  Journal of magnetic resonance imaging : JMRI. 11/2005; 22(4):475-82.

  PURPOSE: To differentiate glioma grade based on blood flow measured using continuous arterial spin labeled (CASL) perfusion MRI, implemented at 3 Tesla for improved signal-to-noise ratio (SNR) andPURPOSE: To differentiate glioma grade based on blood flow measured using continuous arterial spin labeled (CASL) perfusion MRI, implemented at 3 Tesla for improved signal-to-noise ratio (SNR) and spin labeling effect. MATERIALS AND METHODS: CASL perfusion images were obtained preoperatively in 26 patients with brain neoplasms (19 high-grade gliomas (HGGs; WHO grades 3 and 4) and seven low-grade gliomas (LGGs; WHO grades 1 and 2)). The mean and maximum tumor blood flow (TBF and TBFmax) were calculated in the neoplasm, including surrounding infiltrating tumor vs. edema. Measures normalized to global CBF (nTBF and nTBFmax) were also obtained. RESULTS: Normalized measures of TBFmax provided the best distinction between HGG and LGG groups (Wilcoxon rank sum test, P = 0.01). Seventeen of 19 HGGs showed nTBFmax > 1.0, and 15 of 19 showed nTBFmax > 1.3. Four of seven LGGs showed nTBFmax < 1.0, and six of seven showed nTBFmax < 1.3. Absolute TBFmax also differed significantly between the HGG and LGG groups (P = 0.04). TBFmax in 11 of 17 HGGs was >50 mL/100 g/min (mean +/- SD = 94.9 +/- 71.7 mL/100 g/min). All but one LGGs showed TBFmax < or = 50 mL/100 g/min (mean +/- SD = 42.8 +/- 22.0 mL/100 g/min). CONCLUSION: CASL perfusion MRI provides a quantitative, noninvasive alternative to dynamic susceptibility contrast perfusion MR methods for evaluating gliomas.

• Sp1 is involved in Akt-mediated induction of VEGF expression through an HIF-1-independent mechanism.

  Authors: Nabendu Pore, Shuang Liu, Hui-Kuo Shu, Bin Li, Daphne Haas-Kogan, David Stokoe, Julie Milanini-Mongiat, Gilles Pages, Donald M O'Rourke, Eric Bernhard, Amit Maity

  Molecular biology of the cell. 12/2004; 15(11):4841-53.

  Increased expression of vascular endothelial growth factor (VEGF) contributes to the growth of many tumors by increasing angiogenesis. Although hypoxia is a potent inducer of VEGF, we previouslyIncreased expression of vascular endothelial growth factor (VEGF) contributes to the growth of many tumors by increasing angiogenesis. Although hypoxia is a potent inducer of VEGF, we previously showed that epidermal growth factor receptor amplification and loss of PTEN, both of which can increase phosphatidylinositol-3-kinase (PI3K) activity, increase VEGF expression. Using both adenoviral vectors and a cell line permanently expressing constitutively active myristoylated Akt (myrAkt), we show that activation of Akt, which is downstream of PI3K, increases VEGF expression in vitro and increases angiogenesis in a Matrigel plug assay. Transient transfection experiments using reporter constructs containing the VEGF promoter showed that up-regulation of VEGF by Akt is mediated through Sp1 binding sites located in the proximal promoter. Small interfering RNA directed against Sp1 prevented the induction of VEGF mRNA in response to myrAkt but not to hypoxia. Expression of myrAkt is associated with increased phosphorylation of Sp1 and its increased binding to a probe corresponding to the -88/-66 promoter region. In conclusion, our results indicate that Sp1 is required for transactivation of the VEGF by Akt. Others have proposed that the PI3K/Akt pathway can increase VEGF expression via the hypoxia-inducible factor 1 (HIF-1); however, our results suggest an alternative mechanism can also operate.

• SHP-2-dependent mitogen-activated protein kinase activation regulates EGFRvIII but not wild-type epidermal growth factor receptor phosphorylation and glioblastoma cell survival.

  Authors: Yi Zhan, Donald M O'Rourke

  Cancer research. 12/2004; 64(22):8292-8.

  In human glioblastomas, the most common mutation of epidermal growth factor receptor (EGFR) is an in-frame deletion of an 801-bp sequence in the extracellular domain of EGFR termed EGFRvIII. TheIn human glioblastomas, the most common mutation of epidermal growth factor receptor (EGFR) is an in-frame deletion of an 801-bp sequence in the extracellular domain of EGFR termed EGFRvIII. The EGFRvIII does not bind ligand EGF but has constitutive tyrosine phosphorylation (pTyr) content and kinase activity that result in enhanced transformation, reduced apoptosis, and resistance to therapy. Here we report that the protein tyrosine phosphatase SHP-2 modulates a mitogen-activated protein kinase (MAPK) kinase (MEK)-mediated signaling pathway that regulates EGFRvIII pTyr and cell survival in U87MG.EGFRvIII cells. Overexpression of the phosphatase-inactive form of SHP-2 inhibited EGFRvIII pTyr by decreasing MAPK phosphorylation. Consistent with this, we observed that the MEK inhibitor PD98059, but not the phosphatidylinositol 3'-kinase inhibitor LY294002, inhibited EGFRvIII pTyr. Furthermore, constitutive EGFRvIII pTyr content observed in U87MG, LN229, and U373MG glioblastoma cells, but not in NR6.EGFRvIII fibroblasts, correlated with elevated MAPK levels in these cells. Interestingly, LY294002, but not PD98059, inhibited wild-type EGFR pTyr in response to EGF treatment in U87MG parental cells and in wild-type EGFR-overexpressing U87MG cells. Inhibition of EGFRvIII pTyr by PD98059 was not observed to be phosphorylation site specific. However, LY294002 more specifically inhibited wild-type EGFR pTyr at residues Tyr(992) and Tyr(1068) in the COOH terminus. Treatment of U87MG.EGFRvIII cells with PD98059, but not LY294002, also resulted in increased cell death in response to cisplatin. Collectively, a distinct MEK-mediated pathway in human glioblastoma cells appears to differentially modulate EGFRvIII and wild-type EGFR pTyr, and inhibition of the MAPK pathway sensitizes EGFRvIII-containing human glioblastoma cells to cisplatin-induced cell death.

• Transcriptional regulation of signal regulatory protein alpha1 inhibitory receptors by epidermal growth factor receptor signaling.

  Authors: Gurpreet S Kapoor, Dmitri Kapitonov, Donald M O'Rourke

  Cancer research. 10/2004; 64(18):6444-52.

  Signal regulatory protein (SIRP) alpha1 is a membrane glycoprotein and a member of the SIRP receptor family. These transmembrane receptors have been shown to exert negative effects on signalSignal regulatory protein (SIRP) alpha1 is a membrane glycoprotein and a member of the SIRP receptor family. These transmembrane receptors have been shown to exert negative effects on signal transduction by receptor tyrosine kinases via immunoreceptor tyrosine-based inhibitory motifs in the carboxyl domain. Previous work has demonstrated that SIRPs negatively regulate many signaling pathways leading to reduction in tumor migration, survival, and cell transformation. Thus, modulation of SIRP expression levels or activity could be of great significance in the field of cancer therapy. The aim of the present study was to determine the factors that regulate levels of SIRPalpha1 in human glioblastoma cells that frequently overexpress the epidermal growth factor receptor (EGFR) because SIRPs have been shown to negatively regulate EGFR signaling. Northern blot analysis and immunoprecipitation assays showed variable expression levels of endogenous SIRPalpha transcripts in nine well-characterized glioblastoma cell lines. We examined SIRPalpha1 regulation in U87MG and U373MG cells in comparison with clonal derivatives that express a truncated form of erbB2, which negatively regulates EGFR signaling by inducing the formation of nonfunctional heterodimeric complexes. Mutant erbB2-expressing cells contained more SIRPalpha1 mRNA when compared with the parental cells in presence or absence of serum. Similarly, immunoprecipitation assays showed increased SIRPalpha1 protein levels in erbB-inhibited cells when compared with parental cells. Messenger RNA stability assays revealed that the increased mRNA levels in EGFR-inhibited cells were due to an induction of transcription. Consistent with this finding, expression of the erbB2 mutant receptor up-regulated SIRPalpha1 promoter activity in all cell lines tested. Interestingly, pharmacological inhibition of the kinase activities of EGFR, erbB2, and src and activation of mitogen-activated protein kinase, but not phosphatidylinositol 3'-kinase, significantly up-regulated SIRPalpha1 promoter activity. Based on these observations, we hypothesize that down-modulation of EGFR signaling leads to transcriptional up-regulation of the inhibitory SIRPalpha1 gene. These data may be important in the application of erbB-inhibitory strategies and for design of therapies for the treatment of glial tumors and other epithelial malignancies.

• Distinct domains in the SHP-2 phosphatase differentially regulate epidermal growth factor receptor/NF-kappaB activation through Gab1 in glioblastoma cells.

  Authors: Gurpreet S Kapoor, Yi Zhan, Gibbes R Johnson, Donald M O'Rourke

  Molecular and cellular biology. 02/2004; 24(2):823-36.

  The transcription factor nuclear factor kappaB (NF-kappaB) plays an important role in inflammation and cancer, is activated by a variety of stimuli including tumor necrosis factor alpha,The transcription factor nuclear factor kappaB (NF-kappaB) plays an important role in inflammation and cancer, is activated by a variety of stimuli including tumor necrosis factor alpha, interleukin-1, UV irradiation, and viruses, as well as receptor tyrosine kinases, such as epidermal growth factor receptor (EGFR). Although previous studies suggest that EGFR can induce NF-kappaB, the mechanism of this activation remains unknown. In this study, we identify the components of the EGFR-induced signalosome in human glioblastoma cells required to regulate NF-kappaB activation. Immunoprecipitation analyses with ErbB-modulated cells indicate that association between SHP-2 and Grb2-associated binder 1 (Gab1) is the critical step in the formation of the signalosome linking EGFR to NF-kappaB activation. We also show that EGFR-induced NF-kappaB activation is mediated by the PI3-kinase/Akt activation loop. Overexpression of SHP-2, Gab1, and myristoylated Akt significantly upregulated NF-kappaB transcriptional activity and DNA binding activity in glioblastoma cells. Interestingly, overexpression of either one of the two SH2 domain mutants of SHP-2, R32E or R138E, slightly reduced NF-kappaB activity relative to that of wild-type SHP-2, indicating that the SH2 domains of SHP-2 are required for EGFR-induced NF-kappaB activation. On the other hand, ectopic overexpression of either a Gab1 mutant incapable of binding to SHP-2 (Y627F) or a phosphatase-inactive SHP-2 mutant (C459S) caused a significant increase in NF-kappaB activity. Moreover, SHP-2 C459S-expressing cells displayed higher Gab1 phosphotyrosine content, suggesting that SHP-2 regulates Gab1 phosphorylation through its phosphatase domain, which confers a negative regulatory effect on NF-kappaB activity. These results indicate that SHP-2/Gab1 association is critical for linking EGFR to NF-kappaB transcriptional activity via the PI3-kinase/Akt signaling axis in glioblastoma cells and that SHP-2 acts as a dual regulator of NF-kappaB activation.

• Constitutive EGFR signaling confers a motile phenotype to neural stem cells.

  Authors: John A Boockvar, Dmitri Kapitonov, Gurpreet Kapoor, Joost Schouten, George J Counelis, Oliver Bogler, Evan Y Snyder, Tracy K McIntosh, Donald M O'Rourke

  Molecular and cellular neurosciences. 01/2004; 24(4):1116-30.

  The epidermal growth factor receptor (EGFR) has been shown to play an important role in brain development, including stem and precursor cell survival, proliferation, differentiation, and migration.The epidermal growth factor receptor (EGFR) has been shown to play an important role in brain development, including stem and precursor cell survival, proliferation, differentiation, and migration. To further examine the temporal and spatial requirements of erbB signals in uncommitted neural stem cells (NSCs), we expressed the ligand-independent EGF receptor, EGFRvIII, in C17.2 NSCs. These NSCs are known to migrate and to evince a tropic response to neurodegenerative environments in vivo but for which an underlying mechanism remains unclear. We show that enhanced erbB signaling via constitutive kinase activity of EGFRvIII in NSCs sustains an immature phenotype and enhances NSC migration.

• Mitogenic signaling cascades in glial tumors.

  Authors: Gurpreet S Kapoor, Donald M O'Rourke

  Neurosurgery. 07/2003; 52(6):1425-34; discussion 1434-5.

  Gliomas are primary central nervous system tumors that arise from astrocytes, oligodendrocytes, or their precursors. Gliomas can be classified into several groups according to histological features.Gliomas are primary central nervous system tumors that arise from astrocytes, oligodendrocytes, or their precursors. Gliomas can be classified into several groups according to histological features. A number of genetic alterations have been identified in human gliomas; these generally affect either signal transduction pathways activated by receptor tyrosine kinases or cell cycle growth arrest pathways. These observed genetic alterations are now being used to complement histopathological diagnosis. The aim of the present review is to give a broad overview of the receptor tyrosine kinase signaling machinery involved in gliomagenesis, with an emphasis on the cooperative interaction between receptor tyrosine kinase signaling and the cell cycle-regulatory machinery. Understanding molecular features of primary glial tumors will eventually allow for target-selective intervention in distinct glioma subsets and a more rational approach to adjuvant therapies for these refractory diseases.

• PTEN mutation and epidermal growth factor receptor activation regulate vascular endothelial growth factor (VEGF) mRNA expression in human glioblastoma cells by transactivating the proximal VEGF promoter.

  Authors: Nabendu Pore, Shuang Liu, Daphne A Haas-Kogan, Donald M O'Rourke, Amit Maity

  Cancer research. 02/2003; 63(1):236-41.

  Our previous work showed that, compared with parental U87MG human glioblastoma cells, vascular endothelial growth factor (VEGF) mRNA levels are decreased in U87/T691, a derivative line in whichOur previous work showed that, compared with parental U87MG human glioblastoma cells, vascular endothelial growth factor (VEGF) mRNA levels are decreased in U87/T691, a derivative line in which epidermal growth factor receptor (EGFR) signaling is inhibited by introduction of a truncated p185(Neu) protein (A. Maity et al., Cancer Res., 60: 5879-5886, 2000). The effect of EGFR activation on VEGF was mediated at the level of transcription via a phosphatidylinositol 3'-kinase (PI3K)-dependent pathway. In the current study we investigated the effect of PTEN, a negative regulator of PI3K signaling commonly mutated in glioblastoma cells, on VEGF expression. Several glioblastoma cell lines containing mutant PTEN, including U87MG, U87/T691, and U251MG, were infected with adenovirus expressing wild-type PTEN. This led to a decrease in the levels of both VEGF mRNA and phosphorylated Akt, a marker for PI3K activation. Treatment of U87MG cells with LY294002, a PI3K inhibitor, or cotransfection with a vector expressing wild-type PTEN decreased VEGF promoter activity using reporters containing either 1.5 kb of the promoter or a fragment extending from -88 to +54 bp. Activity of the -88/+54 VEGF promoter was down-regulated by dominant negative Akt and up-regulated by constitutively active myristoylated Akt. Introduction of wild-type PTEN and pharmacological inhibition of EGFR decreased VEGF mRNA expression and VEGF promoter activity in U87MG cells to a greater extent that did either manipulation by itself. Therefore, in human glioblastoma cells, PTEN mutation can cooperate with EGFR activation to increase VEGF mRNA levels by transcriptionally up-regulating the proximal VEGF promoter via the PI3K/Akt pathway.

• Neural stem cell biology may be well suited for improving brain tumor therapies.

  Authors: Stephen Yip, Karen S Aboody, Michael Burns, Jaime Imitola, John A Boockvar, Jennifer Allport, Kook In Park, Yang D Teng, Mahesh Lachyankar, Tracy McIntosh, Donald M O'Rourke, Samia Khoury, Ralph Weissleder, Peter M Black, William Weiss, Evan Y Snyder

  Cancer journal (Sudbury, Mass.). 9(3):189-204.

  Neural stem cells (NSCs) are capable of tremendous migratory potential to areas of pathology in the central nervous system. When implanted into a diseased or injured nervous system, NSCs can travelNeural stem cells (NSCs) are capable of tremendous migratory potential to areas of pathology in the central nervous system. When implanted into a diseased or injured nervous system, NSCs can travel through great distances to and engraft within areas of discrete as well as diffuse abnormalities. Engraftment is often followed by integration into the local neural milieu, accompanied by stable gene expression from the NSCs. In addition, the pluripotency of NSCs endows them with the capability to replace diseased tissues in an appropriate manner. Recent evidence has also suggested that engrafted exogenous NSCs may have effects on the surrounding microenvironment, such as promoting protection and/or regeneration of host neural pathways. These characteristics of NSCs would seem to make them ideal agents for the treatment of various central nervous system pathologies, especially brain tumors. Brain tumors are generally difficult to treat because of the unique location of the lesions. In primary gliomas, the extensive infiltrative nature of the tumor cells presents a challenge for their effective and total eradication, hence the high rate of treatment failure and disease recurrence. In addition, normal brain structures are distorted and are often destroyed by the growing neoplasm. Even with effective therapy to surgically resect and destroy the neoplastic tissues, the brain is still injured, which often leaves the patient in a debilitated state. The unique ability of NSCs to "home in" on tumor cells followed by the delivery of a desired gene product makes the NSC a very promising agent in brain tumor therapy. Cytolytic viruses and genes coding for anti-tumor cytokines, pro-drug converting enzymes, and various neurotrophic factors have all been engineered into engraftable NSCs for delivery to tumors. When they are specially tagged, such injected NSCs can be visualized with the use of novel imaging techniques and tracked in vivo within living animals over real time. If the NSCs were also capable of participating in the subsequent repair and regeneration of the tumor-afflicted brain-at present a potential but as-yet-unproven aspect of this intervention-then its role in abetting anti-tumor therapy would be complete. It is important to emphasize, however, that the use of NSCs is adjunctive and is not a replacement for other therapies that should be used in parallel.