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Biomedical subjects

Xandra Breakefield

Publications and source records attributed to Xandra Breakefield.

4 recordsLinked to original sources
PubMed2005

Magnetic resonance imaging and characterization of spontaneous lesions in a transgenic mouse model of tuberous sclerosis as a model for endothelial cell-based transgene delivery.

Tuberous sclerosis (TSC) is an autosomal dominant genetic disorder characterized by abnormalities in cellular migration, proliferation, and differentiation in many tissues. Benign hamartomas develop in multiple organs, believed to be caused by somatic mutation in addition to germ line mutation to cause loss of both alleles of either the TSC1 or TSC2 tumor suppressor gene, with resultant dysregulated growth due to loss of hamartin or tuberin function, respectively. This study focuses on detecting spontaneous lesions in a knockout mouse model of TSC2 by magnetic resonance imaging (MRI) and exploring the efficiency of introducing gene products into lesions, using transduced endothelial cells as gene vehicles. MRI was shown to be effective in detecting spontaneous lesions in multiple tissues as a means of assessing the prevalence of tumors. Tsc(2+/) heterozygous mice were screened at 12-24 months of age. MRI detected 100% of the renal lesions (cystadenomas, renal cell carcinomas) and 75% of the hepatic lesions (hemangiosarcomas), later identified by histology. Cell-mediated gene delivery was evaluated by immunohistochemical analysis of renal, hepatic, and lung lesions after intravenous delivery of MS1 mouse endothelial cells, transduced to express an enhanced form of green fluorescent protein (EGFP). Preliminary immunohistochemical analysis, using a polyclonal antibody to EGFP and a horseradish peroxidase-diaminobenzidine detection system, revealed these cells throughout liver, kidney, and lung sections from injected animals, organs that are frequently affected in TSC2 patients, as well as within the lesions themselves.

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PubMed2003

Real-time imaging of TRAIL-induced apoptosis of glioma tumors in vivo.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to induce apoptosis in neoplastic cells. While many previous studies have been performed in cell culture, the delivery and efficiency of TRAIL variants in vivo is less well established. Using dual substrate/reporter bioluminescence imaging (Fluc: firefly luciferase-luciferin and Rluc: Renilla luciferase-coelenterazine), we tested the efficacy of TRAIL using replication-deficient herpes simplex virus (HSV) type 1 amplicon vectors in gliomas. The cDNA for complete TRAIL and the extracellular domain of TRAIL (aa 114-281) were cloned into HSV amplicons and packaged into helper virus-free vectors. Both forms of TRAIL induced similar degrees of apoptosis in human glioma cells (Gli36) in culture within 24 h of infection with TRAIL amplicon vectors. Growth of tumors stably transfected with Fluc (Gli36fluc+) was readily monitored in vivo by bioluminescence imaging following luciferin administration. HSV amplicon vectors bearing the genes for TRAIL and Rluc injected directly into Gli36fluc(+)-expressing subcutaneous gliomas revealed peak Rluc activity 36 h after intratumoral injection as determined by coelenterazine injection followed by imaging. TRAIL-treated gliomas regressed in size over a period of 4 weeks as compared to the mock-injected gliomas. These results show the efficacy of vector delivered TRAIL in treating tumors in vivo and offer a unique way to monitor both gene delivery and efficacy of TRAIL-induced apoptosis in tumors in vivo in real time by dual enzyme substrate (Rluc/Fluc) imaging.

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PubMed2003

In vivo tracking of neural progenitor cell migration to glioblastomas.

The ability to noninvasively track the migration, engraftment, and proliferation of neural progenitor cells (NPCs) has significant clinical and research implications. The purpose of our study was to explore the macroscopic migratory capabilities of NPCs toward brain tumors after implantation into nude mice. We stably transfected C17.2 NPCs with the firefly luciferase gene (F-luc) and implanted cells into (1) the contralateral brain parenchyma (2 x 10(6) cells), (2) the ventricles (2 x 10(6) cells), (3) the vasculature (1 x 10(5) cells), or (4) the intraperitoneal cavity (5 x 10(6) cells) of mice bearing intracranial gliomas (Gli36). Using serial bioluminescence imaging, migration of parenchymally injected cells was observed across the corpus callosum, first detected at 1 week, with maximal density at the tumor site 2-3 weeks after implantation. Similar patterns were also observed with intraventricular injections; however, tumors were populated earlier, presumably because of the shorter distance to travel. Intravenous injections resulted in more modest tumoral NPC populations, whereas virtually no cells could be identified in tumors after intraperitoneal injection. These results confirm the migratory capability of NPCs over considerable distances and their preferential accumulation in brain tumors on CNS rather than peripheral injection.

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