Effects of irradiation on brain vasculature using an in situ tumor model.

PURPOSE: Damage to normal tissue is a limiting factor in clinical radiotherapy (RT). We tested the hypothesis that the presence of tumor alters the response of normal tissues to irradiation using a rat in situ brain tumor model. METHODS AND MATERIALS: Intravital microscopy was used with a rat cranial window to assess the in situ effect of rat C6 glioma on peritumoral tissue with and without RT. The RT regimen included 40 Gy at 8 Gy/day starting Day 5 after tumor implant. Endpoints included blood-brain barrier permeability, clearance index, leukocyte-endothelial interactions and staining for vascular endothelial growth factor (VEGF) glial fibrillary acidic protein, and apoptosis. To characterize the system response to RT, animal survival and tumor surface area and volume were measured. Sham experiments were performed on similar animals implanted with basement membrane matrix absent of tumor cells. RESULTS: The presence of tumor alone increases permeability but has little effect on leukocyte-endothelial interactions and astrogliosis. Radiation alone increases tissue permeability, leukocyte-endothelial interactions, and astrogliosis. The highest levels of permeability and cell adhesion were seen in the model that combined tumor and irradiation; however, the presence of tumor appeared to reduce the volume of rolling leukocytes. Unirradiated tumor and peritumoral tissue had poor clearance. Irradiated tumor and peritumoral tissue had a similar clearance index to irradiated and unirradiated sham-implanted animals. Radiation reduces the presence of VEGF in peritumoral normal tissues but did not affect the amount of apoptosis in the normal tissue. Apoptosis was identified in the tumor tissue with and without radiation. CONCLUSIONS: We developed a novel approach to demonstrate that the presence of the tumor in a rat intracranial model alters the response of normal tissues to irradiation.

Postoperative swallowing function after posterior fossa tumor resection in pediatric patients.

OBJECTIVE: After tumor resection involving the posterior fossa, postoperative swallowing dysfunction may be anticipated. This retrospective study was designed to document swallowing abnormalities in children after posterior fossa brain tumor surgery and to recommend management approaches for children at risk for aspiration. METHODS: Twenty-four children referred postoperatively for a video fluoroscopic swallow study (VFSS) out of 127 children undergoing posterior fossa surgery for brain tumor resection from 1998 to 2001 were evaluated for oral, pharyngeal, and cervical esophageal transits. CONCLUSION: Less than half of the 24 children swallowed functionally within the first week after surgery. VFSS was an appropriate tool for diagnosing swallowing dysfunction, which is impossible to determine at bedside. Children with brain stem involvement and more difficult recovery had significantly worse swallowing function and greater aspiration. We recommend that children with compromised swallowing function should not feed orally until a radiographic swallowing assessment demonstrates functional and safe swallowing with or without therapeutic intervention.

Correlation of N-cadherin expression in high grade gliomas with tissue invasion.

Cadherins are Ca2+-dependent cell adhesion molecules that play an important role in tissue construction and morphogenesis in multicellular organisms. Over the last few years, reports have emerged in the literature describing the involvement of cadherins in tumor invasion and metastasis. Cadherins typically demonstrate up and down-regulation according to the biological needs of the tissue. Additionally, up-regulation of N-cadherin is thought to be important for tumor formation in early stages of tumor development. We studied N-cadherin in surgical specimens of patients with primary glioblastoma by microarray analysis and found that N-cadherin mRNA expression is up-regulated compared to normal brain. To study the effects of N-cadherin expression on invasion and metastasis in vitro and in vivo, we overexpressed N-cadherin in the rat C6 glioma cell line which normally has low levels of N-cadherin. We found that up-regulation of N-cadherin resulted in a slight decreased adhesion to type IV collagen, fibronectin, and laminin, but statistically significant decreased adhesion to type I collagen. Furthermore, increased expression of N-cadherin correlated with a dramatic decrease in invasive behavior in extracellular matrix invasion assays. We then proceeded to study these cell lines in vivo in a rat intracranial glioma model, and found that N-cadherin expression inversely correlated with invasion into surrounding tissues, irregular margins, and extracranial invasion. In summary, these data collectively demonstrate that N-cadherin levels are important in the malignant behavior of gliomas, and may serve as a prognostic indicator for patients with high-grade gliomas.

Recombinant vesicular stomatitis virus vectors as oncolytic agents in the treatment of high-grade gliomas in an organotypic brain tissue slice-glioma coculture model.

OBJECT: The purpose of this study was to evaluate both replication-competent and replication-restricted recombinant vesicular stomatitis virus (VSV) vectors as therapeutic agents for high-grade gliomas by using an organotypic brain tissue slice-glioma coculture system. METHODS: The coculture system involved growing different brain structures together to allow neurons from these tissues to develop synaptic connections similar to those found in vivo. Rat C6 or human U87 glioma cells were then introduced into the culture to evaluate VSV as an oncolytic therapy. The authors found that recombinant wild-type VSV (rVSV-wt) rapidly eliminated C6 glioma cells from the coculture, but also caused significant damage to neurons, as measured by a loss of microtubule-associated protein 2 immunoreactivity and a failure in electrophysiological responses from neurons in the tissue slice. Nonetheless, pretreatment with interferon beta (IFNbeta) virtually eliminated VSV infection in healthy tissues without impeding any oncolytic effects on tumor cells. Despite the protective effects of the IFNbeta pretreatment, the tissue slices still showed signs of cytopathology when exposed to rVSV-wt. In contrast, pretreatment with IFNbeta and inoculation with a replication-restricted vector with its glycoprotein gene deleted (rVSV-deltaG) effectively destroyed rat C6 and human U87 glioma cells in the coculture, without causing detectable damage to the neuronal integrity and electrophysiological properties of the healthy tissue in the culture. CONCLUSIONS: Data in this study provide in vitro proof-of-principle that rVSV-deltaG is an effective oncolytic agent that has minimal toxic side effects to neurons compared with rVSV-wt and therefore should be considered for development as an adjuvant to surgery in the treatment of glioma.

The centrosomal protein TACC3 is essential for hematopoietic stem cell function and genetically interfaces with p53-regulated apoptosis.

TACC3 is a centrosomal/mitotic spindle-associated protein that is highly expressed in a cell cycle-dependent manner in hematopoietic lineage cells. During embryonic development, TACC3 is expressed in a variety of tissues in addition to the hematopoietic lineages. TACC3 deficiency causes an embryonic lethality at mid- to late gestation involving several lineages of cells. Hematopoietic stem cells, while capable of terminal differentiation, are unable to be expanded in vitro or in vivo in reconstitution approaches. Although gross alterations in centrosome numbers and chromosomal segregation are not observed, TACC3 deficiency is associated with a high rate of apoptosis and expression of the p53 target gene, p21(Waf1/Cip1). Hematopoietic stem cell functions, as well as deficiencies in other cell lineages, can be rescued by combining the TACC3 deficiency with p53 deficiency. The results support the concept that TACC3 is a critical component of the centrosome/mitotic spindle apparatus and its absence triggers p53-mediated apoptosis.