Gerald A Grant

Duke University Medical Center, Durham, North Carolina, United States

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Publications (75)185.15 Total impact

  • Neurosurgery 08/2014; 61 Suppl 1:N1. · 2.53 Impact Factor
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    ABSTRACT: Chiari Type I Malformation (CMI) is characterized by herniation of the cerebellar tonsils through the foramen magnum at the base of the skull, resulting in significant neurologic morbidity. As CMI patients display a high degree of clinical variability and multiple mechanisms have been proposed for tonsillar herniation, it is hypothesized that this heterogeneous disorder is due to multiple genetic and environmental factors. The purpose of the present study was to gain a better understanding of what factors contribute to this heterogeneity by using an unsupervised statistical approach to define disease subtypes within a case-only pediatric population.
    BMC Medical Genomics 06/2014; 7(1):39. · 3.91 Impact Factor
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    ABSTRACT: Plasmonics-active gold nanostars exhibiting strong imaging contrast and efficient photothermal transduction were synthesized for a novel pulsed laser-modulated plasmonics-enhanced brain tumor microvascular permeabilization. We demonstrate a selective, optically modulated delivery of nanoprobes into the tumor parenchyma with minimal off-target distribution.
    Nanoscale 03/2014; · 6.73 Impact Factor
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    ABSTRACT: Nanotechnology provides tremendous biomedical opportunities for cancer diagnosis, imaging, and therapy. In contrast to conventional chemotherapeutic agents where their actual target delivery cannot be easily imaged, integrating imaging and therapeutic properties into one platform facilitates the understanding of pharmacokinetic profiles, and enables monitoring of the therapeutic process in each individual. Such a concept dubbed "theranostics" potentiates translational research and improves precision medicine. One particular challenging application of theranostics involves imaging and controlled delivery of nanoplatforms across blood-brain-barrier (BBB) into brain tissues. Typically, the BBB hinders paracellular flux of drug molecules into brain parenchyma. BBB disrupting agents (e.g. mannitol, focused ultrasound), however, suffer from poor spatial confinement. It has been a challenge to design a nanoplatform not only acts as a contrast agent but also improves the BBB permeation. In this study, we demonstrated the feasibility of plasmonic gold nanoparticles as both high-resolution optical contrast agent and focalized tumor BBB permeation-inducing agent. We specifically examined the microscopic distribution of nanoparticles in tumor brain animal models. We observed that most nanoparticles accumulated at the tumor periphery or perivascular spaces. Nanoparticles were present in both endothelial cells and interstitial matrices. This study also demonstrated a novel photothermal-induced BBB permeation. Fine-tuning the irradiating energy induced gentle disruption of the vascular integrity, causing short-term extravasation of nanomaterials but without hemorrhage. We conclude that our gold nanoparticles are a powerful biocompatible contrast agent capable of inducing focal BBB permeation, and therefore envision a strong potential of plasmonic gold nanoparticle in future brain tumor imaging and therapy.
    01/2014;
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    ABSTRACT: Chiari Type I Malformation (CMI) is characterized by herniation of the cerebellar tonsils through the base of the skull. Although cerebellar tonsillar herniation (CTH) is hypothesized to result from an underdeveloped posterior cranial fossa (PF), patients are frequently diagnosed by the extent of CTH without cranial morphometric assessment. We recently completed the largest CMI whole genome qualitative linkage screen to date. Despite an initial lack of statistical evidence, stratified analyses using clinical criteria to reduce heterogeneity resulted in a striking increase in evidence for linkage. The present study focused on the use of cranial base morphometrics to further dissect this heterogeneity and increase power to identify disease genes. We characterized the genetic contribution for a series of PF traits and evaluated the use of heritable, disease-relevant PF traits in ordered subset analysis (OSA). Consistent with a genetic hypothesis for CMI, much of the PF morphology was found to be heritable and multiple genomic regions were strongly implicated from OSA, including regions on Chromosomes 1 (LOD = 3.07, p = 3 × 10(-3) ) and 22 (LOD = 3.45, p = 6 × 10(-5) ) containing several candidates warranting further investigation. This study underscores the genetic heterogeneity of CMI and the utility of PF traits in CMI genetic studies.
    Annals of Human Genetics 01/2014; 78(1):1-12. · 2.22 Impact Factor
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    ABSTRACT: Inflammatory pseudotumor (IP) is a benign process that most commonly occurs in the lung and orbit. Extension into the central nervous system is extremely rare, and primary intraventricular lesions of the lateral ventricles are even more infrequent with only 2 cases reported in pediatric patients to date. Here, the authors present an unusual case of IP occurring in a 16-year-old female presenting with a 2-week history of progressive headaches and vomiting, without focal neurological deficits or radiographic evidence of hydrocephalus. The patient underwent left parietal craniotomy and complete resection of the tumor, with no signs of recurrence at 3-month follow-up. Although the rarity of intraventricular IP in pediatric patients can make its initial identification difficult, IP should be considered as a potential diagnosis in this population wherein good outcomes may be achieved following surgical resection.
    Pediatric Neurosurgery 08/2013; · 0.42 Impact Factor
  • Neuropathology and Applied Neurobiology 05/2013; · 4.84 Impact Factor
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  • Gerald A Grant
    World Neurosurgery 03/2013; · 1.77 Impact Factor
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    ABSTRACT: Chiari Type I Malformation (CMI) is characterized by displacement of the cerebellar tonsils below the base of the skull, resulting in significant neurologic morbidity. Although multiple lines of evidence support a genetic contribution to disease, no genes have been identified. We therefore conducted the largest whole genome linkage screen to date using 367 individuals from 66 families with at least two individuals presenting with nonsyndromic CMI with or without syringomyelia. Initial findings across all 66 families showed minimal evidence for linkage due to suspected genetic heterogeneity. In order to improve power to localize susceptibility genes, stratified linkage analyses were performed using clinical criteria to differentiate families based on etiologic factors. Families were stratified on the presence or absence of clinical features associated with connective tissue disorders (CTDs) since CMI and CTDs frequently co-occur and it has been proposed that CMI patients with CTDs represent a distinct class of patients with a different underlying disease mechanism. Stratified linkage analyses resulted in a marked increase in evidence of linkage to multiple genomic regions consistent with reduced genetic heterogeneity. Of particular interest were two regions (Chr8, Max LOD = 3.04; Chr12, Max LOD = 2.09) identified within the subset of "CTD-negative" families, both of which harbor growth differentiation factors (GDF6, GDF3) implicated in the development of Klippel-Feil syndrome (KFS). Interestingly, roughly 3-5% of CMI patients are diagnosed with KFS. In order to investigate the possibility that CMI and KFS are allelic, GDF3 and GDF6 were sequenced leading to the identification of a previously known KFS missense mutation and potential regulatory variants in GDF6. This study has demonstrated the value of reducing genetic heterogeneity by clinical stratification implicating several convincing biological candidates and further supporting the hypothesis that multiple, distinct mechanisms are responsible for CMI.
    PLoS ONE 01/2013; 8(4):e61521. · 3.53 Impact Factor
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    ABSTRACT: Effective treatment of patients with malignant brain tumors requires surgical resection of a high percentage of the bulk tumor. Surgeons require a method that enables delineation of tumor margins, which are not visually distinct by eye. In this study, the feasibility of using gold nanorods (GNRs) for this purpose is evaluated. Anti-Epidermal Growth Factor Receptor (anti-EGFR) conjugated GNRs are used to label human xenograft glioblastoma multiforme (GBM) tumors embedded within slices of brain tissues from healthy nude mice. The anti-EGFR GNRs exhibit enhanced absorption at red to near-infrared wavelengths, often referred to as the tissue optical window, where absorption from blood is minimal. To enable definition of molecular specificity and spatial accuracy of the label, the GNR absorption is compared with GFP fluorescence which is expressed by the GBM cells used here. This work demonstrates a simple but highly translational technique to classify normal and malignant brain tissue regions in open surgery applications using immunolabeled GNR contrast agents.
    Biomedical Optics Express 01/2013; 4(11):2284-2295. · 3.18 Impact Factor
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    ABSTRACT: Resistance of hypoxic solid tumor niches to chemotherapy and radiotherapy remains a major scientific challenge that calls for conceptually new approaches. Here we exploit a hitherto unrecognized ability of sickled erythrocytes (SSRBCs) but not normal RBCs (NLRBCs) to selectively target hypoxic tumor vascular microenviroment and induce diffuse vaso-occlusion. Within minutes after injection SSRBCs, but not NLRBCs, home and adhere to hypoxic 4T1 tumor vasculature with hemoglobin saturation levels at or below 10% that are distributed over 70% of the tumor space. The bound SSRBCs thereupon form microaggregates that obstruct/occlude up to 88% of tumor microvessels. Importantly, SSRBCs, but not normal RBCs, combined with exogenous prooxidant zinc protoporphyrin (ZnPP) induce a potent tumoricidal response via a mutual potentiating mechanism. In a clonogenic tumor cell survival assay, SSRBC surrogate hemin, along with H(2)O(2) and ZnPP demonstrate a similar mutual potentiation and tumoricidal effect. In contrast to existing treatments directed only to the hypoxic tumor cell, the present approach targets the hypoxic tumor vascular environment and induces injury to both tumor microvessels and tumor cells using intrinsic SSRBC-derived oxidants and locally generated ROS. Thus, the SSRBC appears to be a potent new tool for treatment of hypoxic solid tumors, which are notable for their resistance to existing cancer treatments.
    PLoS ONE 01/2013; 8(1):e52543. · 3.53 Impact Factor
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    ABSTRACT: In this study, we investigated the feasibility of using 3.5-Fr (3 Fr = 1 mm) circular phased-array intravascular ultrasound (IVUS) catheters for minimally invasive, image-guided hyperthermia treatment of tumors in the brain. Feasibility was demonstrated in two ways: (1) by inserting a 3.5-Fr IVUS catheter through skull burr holes, for 20 MHz brain imaging in the pig model, and (2) by testing a modified circular array for therapy potential with 18.5-MHz and 9-MHz continuous wave (CW) excitation. The imaging transducer's performance was superior to our previous 9-MHz mechanical IVUS prototype. The therapy catheter transducer was driven by CW electrical power at 18.5 MHz, achieving temperature changes reaching +8°C at a depth of 2 mm in a human glioblastoma grown on the flank of a mouse with minimal transducer resistive heating of +2°C. Further hyperthermia trials showed that 9-MHz CW excitation produced temperature changes of +4.5°C at a depth of 12 mm-a sufficient temperature rise for our long-term goal of targeted, controlled drug release via thermosensitive liposomes for therapeutic treatment of 1-cm-diameter glioblastomas.
    Ultrasonic Imaging 01/2013; 35(1):17-29. · 1.58 Impact Factor
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    ABSTRACT: Myeloid/lymphoid or mixed-lineage leukemia (MLL)-family genes encode histone lysine methyltransferases that play important roles in epigenetic regulation of gene transcription. MLL genes are frequently mutated in human cancers. Unlike MLL1, MLL2 (also known as ALR/MLL4) and its homolog MLL3 are not well-understood. Specifically, little is known regarding the extent of global MLL2 involvement in the regulation of gene expression and the mechanism underlying its alterations in driving tumorigenesis. Here we profile the global loci targeted by MLL2. A combinatorial analysis of the MLL2 binding profile and gene expression in MLL2 wild-type versus MLL2-null isogenic cell lines identified direct transcriptional target genes and revealed the connection of MLL2 to multiple cellular signaling pathways, including the p53 pathway, cAMP-mediated signaling, and cholestasis signaling. In particular, we demonstrate that MLL2 participates in retinoic acid receptor signaling by promoting retinoic acid-responsive gene transcription. Our results present a genome-wide integrative analysis of the MLL2 target loci and suggest potential mechanisms underlying tumorigenesis driven by MLL2 alterations.
    Proceedings of the National Academy of Sciences 10/2012; 109(43):17603-8. · 9.81 Impact Factor
  • Grant GA, Hankinson T, Muh C, Dumont A
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    ABSTRACT: PMID 23839472
    The 62nd Annual Meeting of the Congress of Neurological Surgeons, Chicago, IL; 10/2012
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    ABSTRACT: : At present, there are no established histological or molecular markers of a more aggressive tumor phenotype in patients with a juvenile pilocytic astrocytoma (JPA). Recent work has identified the diagnostic translational potential of genes demonstrating bimodal expression patterns given the easily detectable differences between their low and high expression states. (1) Based on initial analysis of publically available datasets (2-4), we identified L1-cell adhesion molecule (L1CAM) as a bimodally expressed gene in JPA. Given its role as a prognostic marker in other types of cancer, we assessed the expression of L1CAM and its potential as a marker of a more aggressive phenotype in children with JPA. : Evaluation of L1CAM expression was conducted by IHC of FFPE JPA tumor tissue (n = 24; 10 primary, 10 recurrent, 4 pilomyxoid; age range, 1-20 years; median age, 11 years), graded as negative (no or =10% positive cells with weak staining), intermediate (10%< weak to moderate staining <20%), or high (=20% moderate to strong staining). L1CAM expression was analyzed for association with tumor location, age at diagnosis, gender, tumor status (primary or recurrent), Ki-67 index by multivariate analysis, and progression-free survival (PFS) by Kaplan-Meier analysis. : L1CAM staining was negative in 10 and positive in 10 JPA samples (5 intermediate, 5 high); negative in 2 and positive (high) in 2 pilomyxoid. Multivariate analysis demonstrated no correlation between L1CAM expression and location, age, gender, or tumor status, but a significant correlation between L1CAM and Ki-67 index (P = 0.01593). Based on a minimum of one year follow-up, Kaplan-Meier analysis revealed a significant association between positive L1CAM expression and worsened PFS (P = 0.0422, n = 13), but no association between Ki-67 index and PFS. : Increased L1CAM expression correlated with Ki-67 index in JPA and a worsened PFS. Furthermore, L1CAM expression appeared to be a more reliable independent prognostic factor for recurrence in children with JPAs compared with Ki67 index alone.
    Neurosurgery 08/2012; 71(2):E565. · 2.53 Impact Factor
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    ABSTRACT: This study will demonstrate an individualized approach to hearing preservation and tumor management in pediatric patients with neurofibromatosis type 2 (NF2). The unique nature of each case discussed will provide valuable guiding principles for the treating surgeon. Pediatric patients under the care of the senior authors presenting with bilateral vestibular schwannoma and NF2. Interventions used for hearing optimization, in conjunction with surgical interventions, include use of hearing aids, cochlear implants, auditory brainstem implants, radiation therapy, and chemotherapeutic agents such as bevacizumab. Pediatric patients with NF2 present a unique and difficult challenge to the neurotologist. These children are still developing physically, mentally, and socially. They generally have a poorer prognosis and diminished life expectancy. Considerations of utmost importance include management of the tumor with the goal of minimizing outcomes such as significant bilateral hearing loss, facial paralysis, and injury to other cranial nerves, which would be detrimental to the quality of life. These patients are best served by a team of physicians who can provide individualized patient care. The team can proactively develop the treatment strategy before initial tumor resection. Hearing results, tumor control. Each patient with NF2 is unique; methods to preserve hearing must be individually tailored to preserve optimal hearing and avoid disruption of the development of the pediatric patient.
    Otology & neurotology: official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology 06/2012; 33(6):1066-70. · 1.44 Impact Factor
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    ABSTRACT: Gold nanostars, with tunable plasmon in the near infrared tissue optic window, generate intense two-photon photoluminescence capable of in vitro cell labeling and in vivo particle tracking. Efficient photothermal ablation therapy is demonstrated.
    Cancer Res; 06/2012
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    ABSTRACT: Gold nanostars offer unique plasmon properties that efficiently transduce photon energy into heat for photothermal therapy. Nanostars, with their small core size and multiple long thin branches, exhibit high absorption cross-sections that are tunable in the near-infrared region with relatively low scattering effect, making them efficient photothermal transducers. Here, we demonstrate particle tracking and photothermal ablation both in vitro and in vivo. Using SKBR3 breast cancer cells incubated with bare nanostars, we observed photothermal ablation within 5 minutes of irradiation (980-nm continuous-wave laser, 15 W/cm(2)). On a mouse injected systemically with PEGylated nanostars for 2 days, extravasation of nanostars was observed and localized photothermal ablation was demonstrated on a dorsal window chamber within 10 minutes of irradiation (785-nm continuous-wave laser, 1.1 W/cm(2)). These preliminary results of plasmon-enhanced localized hyperthermia are encouraging and have illustrated the potential of gold nanostars as efficient photothermal agents in cancer therapy. FROM THE CLINICAL EDITOR: Gold nanostars are tunable in the near-infrared region with low scattering, thus enable photothermal therapy. Encouraging preliminary results of plasmon-enhanced localized hyperthermia both in vitro and in vivo demonstrate that Au nanostars may be efficient photothermal agents for cancer therapy.
    Nanomedicine: nanotechnology, biology, and medicine 02/2012; 8(8):1355-63. · 6.93 Impact Factor
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    ABSTRACT: Understanding the control of the optical and plasmonic properties of unique nanosystems--gold nanostars--both experimentally and theoretically permits superior design and fabrication for biomedical applications. Here, we present a new, surfactant-free synthesis method of biocompatible gold nanostars with adjustable geometry such that the plasmon band can be tuned into the near-infrared region 'tissue diagnostic window', which is most suitable for in vivo imaging. Theoretical modelling was performed for multiple-branched 3D nanostars and yielded absorption spectra in good agreement with experimental results. The plasmon band shift was attributed to variations in branch aspect ratio, and the plasmon band intensifies with increasing branch number, branch length, and overall star size. Nanostars showed an extremely strong two-photon photoluminescence (TPL) process. The TPL imaging of wheat-germ agglutinin (WGA) functionalized nanostars on BT549 breast cancer cells and of PEGylated nanostars circulating in the vasculature, examined through a dorsal window chamber in vivo in laboratory mouse studies, demonstrated that gold nanostars can serve as an efficient contrast agent for biological imaging applications.
    Nanotechnology 02/2012; 23(7):075102. · 3.84 Impact Factor

Publication Stats

886 Citations
185.15 Total Impact Points

Institutions

  • 2007–2014
    • Duke University Medical Center
      • • Division of Neurosurgery
      • • Department of Radiology
      Durham, North Carolina, United States
  • 2009–2012
    • Duke University
      • Department of Biomedical Engineering (BME)
      Durham, NC, United States
  • 2011
    • Nanyang Technological University
      • School of Chemical and Biomedical Engineering
      Singapore, Singapore
  • 1999–2004
    • University of Washington Seattle
      • Department of Neurological Surgery
      Seattle, WA, United States
  • 2001
    • Cleveland Clinic
      Cleveland, Ohio, United States