Radiation arteriopathy in the transgenic arteriovenous fistula model.

Objective: The transgenic arteriovenous fistula model, surgically constructed with transgenic mouse aorta interposed in common carotid artery-to-external jugular vein fistulae in nude rats, has a 4-month experimental window because patency and transgenic phenotype are lost over time. We adapted this model to investigate occlusive arteriopathy in brain arteriovenous malformations after radiosurgery by radiating grafted aorta before insertion in the fistula. We hypothesized that high-dose radiation would reproduce the arteriopathy observed clinically within the experimental time window and that deletions of endoglin (ENG) and endothelial nitric oxide synthase (eNOS) genes would modify the radiation response.

HIV TAT peptide modifies the distribution of DNA nanolipoparticles following convection-enhanced delivery.

We evaluated gene transfer using PEGylated bioresponsive nanolipid particles (NLPs) containing plasmid DNA administered by convection-enhanced delivery (CED) into orthotopically implanted U87-MG tumors in rat brain. We hypothesized that attachment of the human immunodeficiency virus trans-acting transcriptional activator peptide (TATp) to pH-sensitive, reduction-sensitive NLPs would increase gene transfer. TATp was attached either directly to a phospholipid (TATp-lipid) or via a 2-kd polyethylene glycol (PEG) to a lipid (TATp-PEG-lipid).

New therapeutic approach for brain tumors: Intranasal delivery of telomerase inhibitor GRN163.

The blood-brain barrier is a substantial obstacle for delivering anticancer agents to brain tumors, and new strategies for bypassing it are greatly needed for brain-tumor therapy. Intranasal delivery provides a practical, noninvasive method for delivering therapeutic agents to the brain and could provide an alternative to intravenous injection and convection-enhanced delivery. We treated rats bearing intracerebral human tumor xenografts intranasally with GRN163, an oligonucleotide N3'-->P5'thio-phosphoramidate telomerase inhibitor.

Cytosine deaminase/5-fluorocytosine exposure induces bystander and radiosensitization effects in hypoxic glioblastoma cells in vitro.

Purpose: Treatment of glioblastoma (GBM) is limited by therapeutic ratio; therefore, successful therapy must be specifically cytotoxic to cancer cells. Hypoxic cells are ubiquitous in GBM, and resistant to radiation and chemotherapy, and, thus, are logical targets for gene therapy. In this study, we investigated whether cytosine deaminase (CD)/5-fluorocytosine (5-FC) enzyme/prodrug treatment induced a bystander effect (BE) and/or radiosensitization in hypoxic GBM cells.

Synthesis and comparative toxicology of a series of polyhedral borane anion-substituted tetraphenyl porphyrins.

Three structurally similar tetraphenylporphyrins bearing polyhedral borane anions have been synthesized and their toxicological profiles obtained in rats. These conjugates were found to have quite different acute toxicities as manifested at the maximum tolerated dose (MTD). When given at the MTD and observed over 28 days, the most acutely toxic porphyrin was found to be devoid of toxicity, as measured by blood chemistry panels.

Retro-convection enhanced delivery to increase blood to brain transfer of macromolecules.

A retro-convection enhanced delivery (R-CED) method has been developed to improve the entry of intravenously administered therapeutics within solid brain tumors. R-CED uses an osmotic gradient to withdraw brain interstitial fluid (ISF) in a controlled manner via an implanted microdialysis catheter. Withdrawal of ISF increases the local tissue specific gravity in normal brain and increases twofold the extravasation of intravenous Evans blue (EB) albumin in normal brain and in an orthotopic 9L tumor.

Response of intracerebral human glioblastoma xenografts to multifraction radiation exposures.

Purpose: We investigated the effects of fractionated radiation treatments on the life spans of athymic rats bearing intracerebral brain tumors.

Methods And Materials: U-251 MG or U-87 MG human glioblastoma cells were implanted into the brains of athymic rats, and the resulting tumors were irradiated once daily with various doses of ionizing radiation for 5 consecutive days or for 10 days with a 2-day break after Day 5.

Results: Five daily doses of 1 and 1.

AAV serotype 8-mediated gene delivery of a soluble VEGF receptor to the CNS for the treatment of glioblastoma.

The presence of the blood-brain barrier complicates drug delivery in the development of therapeutic agents for the treatment of glioblastoma multiforme (GBM). The use of local gene transfer in the brain has the potential to overcome this delivery barrier by allowing the expression of therapeutic agents directly at the tumor site. In this study, we describe the development of a recombinant adeno-associated (rAAV) serotype 8 vector that encodes an optimized soluble inhibitor, termed sVEGFR1/R2, of vascular endothelial growth factor (VEGF).

A genetic strategy to overcome the senescence of primary meningioma cell cultures.

Even though meningiomas are the second most common brain tumor in adults, little is known about the molecular basis of their growth and development. The lack of suitable cell culture model systems is an impediment to this understanding. Most studies on meningiomas rely on primary, early passage cell lines that eventually senesce or a few established cell lines that have been derived from aggressive variants of meningiomas.

Barriers to carrier mediated drug and gene delivery to brain tumors.

Brain tumor patients face a poor prognosis despite significant advances in tumor imaging, neurosurgery and radiation therapy. Potent chemotherapeutic drugs fail when used to treat brain tumors because biochemical and physiological barriers limit drug delivery into the brain. In the past decade a number of strategies have been introduced to increase drug delivery into the brain parenchyma.

Orthotopic growth of human glioma cells quantitatively and qualitatively influences radiation-induced changes in gene expression.

The effect of radiation on gene expression has been most frequently studied using tissue culture models. To determine the influence of experimental growth condition on radiation-induced changes in gene expression, microarray analysis was done on two human glioma cell lines (U87 and U251) grown in tissue culture and as s.c.

Bromophenol blue staining of tumors in a rat glioma model.

Objective: For patients with gliomas, decreasing the tumor burden with macroscopic surgical resection may affect quality of life, time to tumor progression, and survival. Injection of bromophenol blue (BPB) may enhance intraoperative visualization of an infiltrating tumor and its margins and improve the extent of resection. In this study, we investigated the uptake of BPB in experimental rat brain tumors.

Chromosome transfer experiments link regions on chromosome 7 to radiation resistance in human glioblastoma multiforme.

Glioblastoma multiforme (GM) is the most lethal form of brain tumor, with a median survival of approximately 1 year. Treatment options are limited. Radiation therapy is a common form of treatment, but many tumors are resistant.

Toxicity, biodistribution, and convection-enhanced delivery of the boronated porphyrin BOPP in the 9L intracerebral rat glioma model.

Purpose: To investigate the toxicity, biodistribution, and convection-enhanced delivery (CED) of a boronated porphyrin (BOPP) that was designed for boron neutron capture therapy and photodynamic therapy.

Methods And Materials: For the toxicity study, Fischer 344 rats were injected with graded concentrations of BOPP (35-100 mg/kg) into the tail vein. For boron biodistribution studies, 9L tumor-bearing rats received BOPP either systematically (intravenously) or locally.

In vivo evaluation of the boronated porphyrin TABP-1 in U-87 MG intracerebral human glioblastoma xenografts.

Boron neutron capture therapy (BNCT) is an adjuvant therapy that has the potential to control local tumor growth. A selective delivery of sufficient amounts of boron to individual tumor cells, compared to surrounding normal tissues, is the key for successful BNCT. We have designed and synthesized a new highly water-soluble boronated porphyrin, TABP-1, as a possible BNCT agent.

Influence of in vivo growth on human glioma cell line gene expression: convergent profiles under orthotopic conditions.

Defining the molecules that regulate tumor cell survival is an essential prerequisite for the development of targeted approaches to cancer treatment. Whereas many studies aimed at identifying such targets use human tumor cells grown in vitro or as s.c.

Hypoxia-induced BAX overexpression and radiation killing of hypoxic glioblastoma cells.

One major challenge in treating glioblastoma multiforme (GBM) has been the presence of radiation-resistant hypoxic cells. The pro-apoptosis protein BAX has been reported to be a possible radiation sensitizer of cancer cells; however, to our knowledge, no studies have reported on the effects of BAX on radiation sensitivity under hypoxic conditions. Therefore, in this study, we specifically overexpressed murine Bax in hypoxic cells in an attempt to enhance radiation-induced cell killing.

Hypoxia-induced radioresistance is independent of hypoxia-inducible factor-1A in vitro.

Purpose: We sought to determine whether hypoxia-induced radioresistance is mediated by the transcription factor hypoxia-inducible factor-1alpha (HIF-1alpha).

Methods And Materials: We used 2 mouse embryonic fibroblast cell lines transformed with H-ras and TAg, 1 HIF-1alpha+/+ and the other HIF-1alpha-/-. Cell were exposed to either 95% air and 5% CO2 (normoxic conditions) or 0.

Distribution in brain of liposomes after convection enhanced delivery; modulation by particle charge, particle diameter, and presence of steric coating.

We have investigated the role of diameter, charge, and steric shielding on the brain distribution of liposomes infused by convection enhanced delivery (CED) using both radiolabeled and fluorescent-labeled particles. Liposomes of 40 and 80-nm diameter traveled the same distance but penetrated significantly less than a 10-kDa dextran; whereas 200-nm-diameter liposomes penetrated less than 80 nm liposomes. A neutral liposome shielded by polyethylene glycol (PEG; 2 kDa; 10% by mole) penetrated significantly farther than an unshielded liposome.

Development of a hypoxia-inducible cytosine deaminase expression vector for gene-directed prodrug cancer therapy.

One important feature of human solid tumors is the presence of a hypoxic microenvironment. Under hypoxia, genes that contain a hypoxia-response element (HRE) can be activated by the binding of hypoxia-inducible factor-1. To reach the goal of selectively killing tumor cells in a hypoxic microenvironment using a gene therapy approach, we developed a cytosine deaminase (CD) gene construct (pH9YCD2) that contains an HRE gene enhancer.

Antitumor effects of specific telomerase inhibitor GRN163 in human glioblastoma xenografts.

Telomerase is a ribonucleoprotein complex that elongates telomeric DNA and appears to play an important role in cellular immortalization of cancers. Because telomerase is expressed in the vast majority of malignant gliomas but not in normal brain tissues, it is a logical target for gliomaspecific therapy. The telomerase inhibitor GRN163, a 13-mer oligonucleotide N3'-->P5' thio-phosphoramidate (Geron Corporation, Menlo Park, Calif.

Detection of hypoxia in human brain tumor xenografts using a modified comet assay.

We used the standard comet assay successfully to generate in vitro dose-response curves under oxic and hypoxic conditions. We then made mixtures of cells that had been irradiated with 3 and 9 Gy of X-rays to simulate two subpopulations in a tumor, but efforts to accurately detect and quantify the subpopulations using the standard comet assay were unsuccessful. Therefore, we investigated a modified comet assay to determine whether it could be used for measuring hypoxia in our model systems.

Overexpression of vascular endothelial growth factor isoforms drives oxygenation and growth but not progression to glioblastoma multiforme in a human model of gliomagenesis.

Vascular endothelial growth factor (VEGF) is thought to promote tumor growth and angiogenesis. Whereas VEGF is up-regulated in only a portion of anaplastic astrocytoma (AA), it is overexpressed in most glioblastoma multiforme (GBM), and the level of expression is correlated with grade of glioma. To explore the possibility that VEGF may act as a driving force in the progression of AA to GBM, the VEGF isoforms VEGF(121) and VEGF(165) were overexpressed in genetically modified, mutant H-Ras-transformed human astrocytes that on intracranial implantation form AA-like tumors.

Growth of human glioblastomas as xenografts in the brains of athymic rats.

Background: We have developed xenografts of human glioblastoma (GBM) and established the baseline growth parameters and histopathological features of these tumors.

Materials-methods: Cells from 4 different human GBM cell lines were injected into the right caudate-putamen of brain in athymic rats. We measured tumor weights and the estimated survival time of each rat.