High Frequency AlGaN/GaN MODFET's

Short-gate MODFET's of AlGaN/GaN on Sapphire have been fabricated and characterized with gate lengths in the .12 - .25 μm range. Values of ft = 50 GHz and fmax = 100 GHz have been obtained. Analyzing the performance, the average electron transit velocity is shown to be 1.25 × 107 cm/s and in some cases well under that value. This compares with theoretical predictions of ~ 2.0 × 107 cm/s. The electron scattering effects of dislocations, which are charged, are modeled to explain the lower mobility. Ion bombardment or dry etching is used for mesa isolation. Ti/Al/Ti/Au sintered for 100 seconds at 800 °C is used to yield ohmic contacts of .5 - 1.0 Ω-mm. Pt/Au Schottky gates are used. A high breakdown voltage, exceeding 100 V even for short gate MODFET's, shows that ten times higher load resistance values are possible, compared with GaAs MODFET's. Normalized output power levels well over 10 W/ mm are thus projected for GaN MODFET's on SiC substrates, where the thermal conductivity is about 5W/cm-°C. with future integrated traveling-wave, power-combining circuits, output power > 100 W at 10 GHz is predicted.

Aspirin decreases systemic exposure to clopidogrel through modulation of P-glycoprotein but does not alter its antithrombotic activity

Decreased oral clopidogrel absorption caused by induction of intestinal permeability glycoprotein (P-gp) expression after aspirin administration was observed in rats. This study evaluated the effect of aspirin coadministration on the pharmacokinetics/pharmacodynamics of clopidogrel in humans. A single 75-mg dose of clopidogrel was orally administered before and after 2 and 4 weeks of once-daily 100-mg aspirin administration in 18 healthy volunteers who were recruited based on CYP2C19 and PON1 genotypes. Plasma concentrations of clopidogrel and its active metabolite, H4, and relative platelet inhibition (RPI) were determined. The P-gp microRNA miR-27a increased by up to 7.67-fold (P = 0.004) and the clopidogrel area under the concentration-time curve (AUC) decreased by 14% (P > 0.05), but the AUC of H4 remained unchanged and RPI increased by up to 15% (P = 0.002) after aspirin administration. These findings indicate low-dose aspirin coadministration may decrease clopidogrel bioavailability but does not decrease its efficacy.

Selection and evaluation of clinically relevant AAV variants in a xenograft liver model

Recombinant adeno-associated viral (rAAV) vectors have shown early promise in clinical trials. The therapeutic transgene cassette can be packaged in different AAV capsid pseudotypes, each having a unique transduction profile. At present, rAAV capsid serotype selection for a specific clinical trial is based on effectiveness in animal models. However, preclinical animal studies are not always predictive of human outcome. Here, in an attempt to further our understanding of these discrepancies, we used a chimaeric human-murine liver model to compare directly the relative efficiency of rAAV transduction in human versus mouse hepatocytes in vivo. As predicted from preclinical and clinical studies, rAAV2 vectors functionally transduced mouse and human hepatocytes at equivalent but relatively low levels. However, rAAV8 vectors, which are very effective in many animal models, transduced human hepatocytes rather poorly-approximately 20 times less efficiently than mouse hepatocytes. In light of the limitations of the rAAV vectors currently used in clinical studies, we used the same murine chimaeric liver model to perform serial selection using a human-specific replication-competent viral library composed of DNA-shuffled AAV capsids. One chimaeric capsid composed of five different parental AAV capsids was found to transduce human primary hepatocytes at high efficiency in vitro and in vivo, and provided species-selected transduction in primary liver, cultured cells and a hepatocellular carcinoma xenograft model. This vector is an ideal clinical candidate and a reagent for gene modification of human xenotransplants in mouse models of human diseases. More importantly, our results suggest that humanized murine models may represent a more precise approach for both selecting and evaluating clinically relevant rAAV serotypes for gene therapeutic applications.

Abstract P6-12-14: Histone deacetylase inhibitor suberoylanilide hydroxamic acid targets breast cancer stem cells and inhibits metastasis

Introduction: Inflammatory breast cancer (IBC) is a distinct and aggressive subtype of locally advance breast cancer associated with increased aldehyde dehydrogenase 1 (ALDH1) positive cancer stem cells (CSCs). IBC is associated with a poor survival rate (40% 5-year survival), with few therapeutic strategies identified that effectively blocked the growth and metastasis of IBC. Our previous in vitro studies revealed that the pan-histone deacetylase inhibitor Suberoylanilide Hydroxamic Acid (SAHA) effectively targets self-renewal of IBC tumor cells.

Materials and Methods: The IBC cell line, SUM149 was tagged with the Luciferase gene (SUM149-LUC) and their in vivo growth in immune compromised mice tested in both orthotopic and metastatic settings.

Results: SUM149-LUC rapidly develop primary tumors and metastatic lesions at a variety of locations including lung, brain, bone, liver, reproductive organs and adrenal glands. SAHA effectively blocked growth of SUM149 primary tumors and inhibited metastasis, which was synergistic with the microtubule stabilizer, Paclitaxel. The therapeutic efficacy of SAHA was associated with a significant decrease in ALDH1+ CSCs populations.

Conclusions: Collectively, these results suggest that strategies of combining agents such as SAHA that target CSCs with Paclitaxel that targets the bulk of proliferating tumor cells warrant further investigation for their potential effectiveness in IBC patients, who have the lowest survival of breast cancer patients and have few therapeutic options.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-12-14.

A semi-automated vascular access system for preclinical models

Murine models are used extensively in biological and translational research. For many of these studies it is necessary to access the vasculature for the injection of biologically active agents. Among the possible methods for accessing the mouse vasculature, tail vein injections are a routine but critical step for many experimental protocols. To perform successful tail vein injections, a high skill set and experience is required, leaving most scientists ill-suited to perform this task. This can lead to a high variability between injections, which can impact experimental results. To allow more scientists to perform tail vein injections and to decrease the variability between injections, a vascular access system (VAS) that semi-automatically inserts a needle into the tail vein of a mouse was developed. The VAS uses near infrared light, image processing techniques, computer controlled motors, and a pressure feedback system to insert the needle and to validate its proper placement within the vein. The VAS was tested by injecting a commonly used radiolabeled probe (FDG) into the tail veins of five mice. These mice were then imaged using micro-positron emission tomography to measure the percentage of the injected probe remaining in the tail. These studies showed that, on average, the VAS leaves 3.4% of the injected probe in the tail. With these preliminary results, the VAS system demonstrates the potential for improving the accuracy of tail vein injections in mice.

Cellular localization and characterization of cytosolic binding partners for Gla domain-containing proteins PRRG4 and PRRG2

The genes encoding a family of proteins termed proline-rich γ-carboxyglutamic acid (PRRG) proteins were identified and characterized more than a decade ago, but their functions remain unknown. These novel membrane proteins have an extracellular γ-carboxyglutamic acid (Gla) protein domain and cytosolic WW binding motifs. We screened WW domain arrays for cytosolic binding partners for PRRG4 and identified novel protein-protein interactions for the protein. We also uncovered a new WW binding motif in PRRG4 that is essential for these newly found protein-protein interactions. Several of the PRRG-interacting proteins we identified are essential for a variety of physiologic processes. Our findings indicate possible novel and previously unidentified functions for PRRG proteins.

A concept of eliminating nonhomologous recombination for scalable and safe AAV vector generation for human gene therapy

Scalable and efficient production of high-quality recombinant adeno-associated virus (rAAV) for gene therapy remains a challenge despite recent clinical successes. We developed a new strategy for scalable and efficient rAAV production by sequestering the AAV helper genes and the rAAV vector DNA in two different subcellular compartments, made possible by using cytoplasmic vaccinia virus as a carrier for the AAV helper genes. For the first time, the contamination of replication-competent AAV particles (rcAAV) can be completely eliminated in theory by avoiding ubiquitous nonhomologous recombination. Vector DNA can be integrated into the host genomes or delivered by a nuclear targeting vector such as adenovirus. In suspension HeLa cells, the achieved vector yield per cell is similar to that from traditional triple-plasmid transfection method. The rcAAV contamination was undetectable at the limit of our assay. Furthermore, this new concept can be used not only for production of rAAV, but also for other DNA vectors.

The anti-genomic (negative) strand of Hepatitis C Virus is not targetable by shRNA

Hepatitis C Virus (HCV) and other plus-strand RNA viruses typically require the generation of a small number of negative genomes (20–100× lower than the positive genomes) for replication, making the less-abundant antigenome an attractive target for RNA interference(RNAi)-based therapy. Because of the complementarity of duplex short hairpin RNA/small interfering RNA (shRNA/siRNAs) with both genomic and anti-genomic viral RNA strands, and the potential of both shRNA strands to become part of the targeting complexes, preclinical RNAi studies cannot distinguish which viral strand is actually targeted in infected cells. Here, we addressed the question whether the negative HCV genome was bioaccessible to RNAi. We first screened for the most active shRNA molecules against the most conserved regions in the HCV genome, which were then used to generate asymmetric anti-HCV shRNAs that produce biologically active RNAi specifically directed against the genomic or antigenomic HCV sequences. Using this simple but powerful and effective method to screen for shRNA strand selectivity, we demonstrate that the antigenomic strand of HCV is not a viable RNAi target during HCV replication. These findings provide new insights into HCV biology and have important implications for the design of more effective and safer antiviral RNAi strategies seeking to target HCV and other viruses with similar replicative strategies.

Abstract P6-10-04: The Presence of Anaplastic Lymphoma Kinase Recapitulates Formation of Breast Tumor Emboli with Encircling Lymphovasculogenesis

Background: Genetic abnormalities in the anaplastic lymphoma kinase (ALK) gene result in activation of signaling pathways including Akt, mTor, and JAK/Stat3. ALK has been shown to be a primary oncogenic driver in a variety of human tumors, including both hematologic malignancies such as anaplastic large cell lymphoma, as well as solid tumors including neuroblastoma, non-small cell lung cancer, myofibroblastic tumors and most recently, high grade serous ovarian carcinoma. While only ∼3% of all breast cancers have been reported to have ALK genetic abnormalities, our studies revealed that inflammatory breast cancer (IBC), the most lethal variant of breast cancer, is characterized by prevalent ALK gene amplification with activated ALK signaling. The present studies investigated the role of ALK in breast cancer by expressing full-length wild type ALK in MCF-7 cells.

Materials and Methods: Clones of MCF-7 breast cancer cells expressing wild type ALK or non-target vector were produced by lentivirus infection and selection of single cell clones. MCF-7 ALK clones were evaluated using live cell and phase contrast imaging, immunofluorescent staining with confocal imaging, gene profiling, phospho-protein array analysis, western blot and ELISA validation. In vivo studies were performed by injection of MCF-7 ALK clones into using NOD. Cg-Prkdcscid Il2rgtm1Wjl/SzJ mice using IACUC approved animal protocols.

Results: When cultured on plastic substrates, MCF-7 ALK clones formed tumor cell aggregates instead of monolayer cultures, and when cultured as tumor spheroids under non-adherent 3D conditions had a distinct cellular phenotype with significantly greater clonogenicity than either non-target vector MCF-7 clones or the parental cell line. Whole transcriptome analysis, with validation using protein arrays, western blots and ELISA analysis revealed that the presence of ALK up-regulated phospho-src. In vivo studies revealed that ALK expressing MCF-7 clones formed tumor emboli that were enwrapped by dermal lymphatic vessels, essentially recapitulating the phenotype of IBC tumor emboli that exhibit encircling lymphovasculogenesis. Enforced expression of wild type ALK in another breast cancer cell line resulted in similar formation of tumor emboli.

Discussion: These studies provide first time evidence for the association between full length ALK and formation of highly invasive tumor emboli enwrapped by lymphatic vessels, which is a primary characteristic of IBC. These studies, taken together with discovery of the prevalence of ALK gene amplification in IBC patients, indicate that ALK represents an important therapeutic target for IBC, with the availability of new ALK targeted therapies to evaluate as single agents and in combinations with other agents that may effectively target IBC tumor emboli that we have now linked to ALK and which represent the metastatic lesion of this lethal variant of breast cancer.

Funding by Susan G. Komen Organization Promise Grant KG081287 (FMR and MC).

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-10-04.

Abstract P5-04-05: E-Cadherin is Required for In Vivo Growth of Inflammatory Breast Cancer: Importance of Mesenchymal-Epithelial Transition (MET) and Role of HIF1α

Background: Inflammatory breast cancer (IBC) is the most aggressive and deadly form of breast cancer and is phenotypically distinct from other forms of locally advanced breast cancer. The 5-year survival for IBC patients (40%) has not improved even with the implementation of multi-disciplinary care and targeted therapies (e.g. anti-HER2 or anti-estrogen therapies). Lymph node involvement is common at first diagnosis and the accelerated metastasis program that characterizes IBC account for a disproportionate number of the 40,000 women who will die from breast cancer. The most common molecular marker for IBC is the cell adhesion surface glycoprotein, E-Cadherin. Classically, E-Cadherin is thought to be a tumor suppressor and its loss is associated with the epithelial-mesenchymal transition (EMT) and acquisition of an invasive phenotype. The importance of EMT in metastasis is well accepted in numerous tumor models although the presence of EMT in patient samples is rarely demonstrated. Given the propensity of IBC to metastasize, one would expect a strong EMT signature in IBC cell lines, however the persistent robust expression of E-Cadherin in IBC patient tumors and in IBC cell lines, with a lack of expression of ZEB1, a transcriptional repressor of E-cadherin and diminished expression of genes within the transforming growth factor beta signaling pathway, suggests otherwise.

Methods: To further define the role of E-Cadherin in IBC, we used the SUM149 IBC cell line to manipulate E-Cadherin via shRNA knockdown and by overexpression of ZEB1 a known transcriptional repressor of E-cadherin.

Results: While the lack of E-Cadherin or ZEB1 overexpression in SUM149 cells led to an EMT phenotype in vitro, E-Cadherin was required for in vivo growth of SUM149 tumor cells. Gene profiling identified novel E-Cadherin signaling pathways including an hypoxia gene signature through HIF1a as well as cytokine responsive pathways. The requirement of HIF-1a for in vivo growth of SUM149 cells was confirmed by shRNA knockdown of HIF-1a.

Conclusions: The absolute requirement for E-Cadherin and maintenance of the mesenchymal-epithelial transition in IBC tumor growth is demonstrated. Furthermore, a novel functional link between E-Cadherin and HIF-1a and in their critical role in survival of IBC tumors is identified for the first time and warrants further investigation.

Supported in part by The Susan G Komen Organization Promise Grant KG081287 (FMR and MC)

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-04-05.

Abstract P4-06-03: Zinc Finger Nuclease Genome Engineering Reveal Multiple Functions of Secretory Leukocyte Peptidase Inhibitor in Regulating Pleuripotency of Cancer Stem Cells in Inflammatory Breast Cancer

Background: Inflammatory breast cancer (IBC) is the most aggressive and lethal variant of this disease and is known to be enriched for cells with a cancer stem cell phenotype. IBC is characterized by the presence of cell aggregates, defined as tumor emboli, that metastasize into skin and chest wall. The only documented biomarker of tumor emboli is the surface glycoprotein, E-cadherin. We previously demonstrated that IBC tumor emboli express the alarm anti-protease, secretory leukocyte peptidase inhibitor (SLPI), a metastasis related gene highly expressed in IBC patient tumors. Since the function of SLPI in IBC is unknown, the present studies used zinc finger technology to knockout (KO) copies of SLPI in the SUM149 IBC cell line to define the role of SLPI in IBC.

Materials and Methods: Using CompoZr zinc finger nuclease (ZFN) technology (Sigma-Aldrich), SLPI KO cell lines were generated by disrupting all alleles (3) in exon 1 of SUM149 cells derived from an IBC primary tumor with a high CD44+cell population. The target-specific ZFNs bound DNA at a sequence-specific location and created double strand breaks repaired by non-homologous end joining, resulting in deletions at the SLPI locus. Single cell SLPI KO clones were isolated and serially passaged to establish stable cell lines. Functional assays were used to assess proliferation, invasion, tube formation and clonogenicity. Global transcriptional profiling was performed to identify genes and signaling pathways directly regulated by SLPI.

Results: SUM149 SLPI KO clones did not produce SLPI protein and had a significantly slower turn-over time of 75 hrs compared with 24 hrs in SUM149 wild type clones. Loss of SLPI blocked invasion by 50%, and completely inhibited formation of tube-like structures, an activity defined as vasculogenic mimicry, characteristic of IBC. The loss of only 1 SLPI allele resulted in the inability of SUM149 cells to grow as anchorage independent clones in soft agar, commonly used as a predictor of in vivo tumorigenicity. SLPI directly regulated expression of multiple genes within the embryonic stem cell pleuripotency canonical pathway, including WNT, Frizzled, PDK-1, platelet derived growth factor receptor and sphingosine-1-phosphate receptor. Studies are underway to determine the specific role of SLPI in IBC tumor growth and metastasis.

Conclusions: Our previous studies demonstrated that SLPI is expressed by IBC tumor emboli and can be used as a biomarker of tumor emboli in IBC core and skin punch biopsies. SLPI was found to not only regulate critical functional activities of IBC tumor cells but also to directly regulate genes within pathways critically important to maintenance of pleuripotency of tumors with a cancer stem cell phenotype. Collectively, these studies demonstrate the power and utility of the zinc finger technology, which enables the interrogation of tumor cells to discern the direct function and role of specific genes of interest.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-06-03.

Bicycle accidents - do we only see the tip of the iceberg? A prospective multi-centre study in a large German city combining medical and police data

INTRODUCTION

Bicycles are becoming increasingly popular. In Münster, a German town with a population of 273,000, bicycles were the main method of transportation in 2009, used more often (37.8%) than cars (36.4%). Each day in Münster, bicycles are used around 450,000 times. In 1982, they were only used around 270,000 times a day. However, the increased use of bicycles has also led to an increased number of bicycle accidents.

METHODS

Between February 2009 and January 2010, data on bicycle-accidents leading to injuries were collected by the Police of Münster and in all emergency units of the six hospitals in Münster. A systematic acquisition of technical data from the police and the medical data from the hospitals were combined anonymously. None of the forms contained personal data of patients involved, except for patient age and sex as well as time and place of bicycle accidents to match the questionnaires. The data were entered into a central database (MS Access for input/MySQL for data retrieval).

RESULTS

2250 patients were included in this study. For each of these patients either a patient record or a hospital record or a police record or a combination of any of these different records existed in our database. In total, 1767 patients received medical treatment at a hospital and 484 people included in the study did not go to a hospital. Three fatalities occurred as a result of bicycle accidents. Considering reasons for hospital admission, traumatic brain injuries were the leading cause (25.7%). However, the largest resource consumption was attributed to fractures of the upper extremities (36.8%) and lower extremities (29.9%) with major surgery.

DISCUSSION

Bicycle accidents occur more frequently than indicated by police records. The results of the Münster Bicycle Study have shown that the actual number of bicycle accidents exceeds the officially reported number by nearly two times. Since bicycle helmets cannot prevent accidents it is recommended not only to focus on helmet use as the only injury prevention method. Other factors, such as weather, pavement and default of traffic, roadworthiness of the bicycles or alcohol/drug abuse also affect the accident rates.