Expression of the naturally occurring truncated trkB neurotrophin receptor induces outgrowth of filopodia and processes in neuroblastoma cells.
(1/10928)
We have investigated the effects of the truncated trkB receptor isoform T1 (trkB.T1) by transient transfection into mouse N2a neuroblastoma cells. We observed that expression of trkB.T1 leads to a striking change in cell morphology characterized by outgrowth of filopodia and processes. A similar morphological response was also observed in SH-SY5Y human neuroblastoma cells and NIH3T3 fibroblasts transfected with trkB.T1. N2a cells lack endogenous expression of trkB isoforms, but express barely detectable amounts of its ligands, brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4). The morphological change was ligand-independent, since addition of exogenous BDNF or NT-4 or blockade of endogenous trkB ligands did not influence this response. Filopodia and process outgrowth was significantly suppressed when full-length trkB.TK+ was cotransfected together with trkB.T1 and this inhibitory effect was blocked by tyrosine kinase inhibitor K252a. Transfection of trkB.T1 deletion mutants showed that the morphological response is dependent on the extracellular, but not the intracellular domain of the receptor. Our results suggest a novel ligand-independent role for truncated trkB in the regulation of cellular morphology. (+info)
Transduction of glioma cells using a high-titer retroviral vector system and their subsequent migration in brain tumors.
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The intracranial migration of transduced glioma cells was investigated in order to improve the treatment of malignant glioma by gene therapy using retroviral vectors. In this study, about half the volume of the tumor mass could be transduced in 14 days after only a single implantation of 3 x 10(5) retrovirus-producing cells into a tumor mass with a diameter of 5 mm. Moreover, we were able to follow the migration of glioma cells transduced by the lacZ-harboring retroviruses originating from the high-titer retrovirus-producing cells. Besides the importance of using a high-titer retroviral vector system, our results also indicate that the implantation site of the virus-producing cells and the interval between the implantation of the virus-producing cells and the subsequent administration of ganciclovir are important factors for the efficient killing of glioma cells. (+info)
An improved method for the structural profiling of keratan sulfates: analysis of keratan sulfates from brain and ovarian tumors.
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A previously developed method for the structural fingerprinting of keratan sulfates (Brown et al., Glycobiology, 5, 311-317, 1995) has been adapted for use with oligosaccharides fluorescently labeled with 2-aminobenzoic acid following keratanase II digestion. The oligosaccharides are separated by high-pH anion-exchange chromatography on a Dionex AS4A-SC column. This methodology permits quantitative analysis of labeled oligosaccharides which can be detected at the sub-nanogram ( approximately 100 fmol) level. Satisfactory calibration of this method can be achieved using commercial keratan sulfate standards. Keratan sulfates from porcine brain phosphocan and human ovarian tumors have been examined using this methodology, and their structural features are discussed. (+info)
Synthesis and evaluation of [18F]1-amino-3-fluorocyclobutane-1-carboxylic acid to image brain tumors.
(4/10928)
We have developed a new tumor-avid amino acid, 1-amino-3-fluorocyclobutane-1-carboxylic acid (FACBC), labeled with 18F for nuclear medicine imaging. METHODS: [18F]FACBC was prepared with high specific activity (no carrier added [NCA]) and was evaluated for its potential in tumor localization. A comparative study was performed for [18F]FACBC and [18F]2-fluorodeoxyglucose (FDG) in which the uptake of each agent in 9L gliosarcoma (implanted intracerebrally in Fisher 344 rats) was measured. In addition, the first human PET study of [18F]FACBC was performed on a patient with residual glioblastoma multiforme. Quantitative brain images of the patient were obtained by using a Siemens 921 47-slice PET imaging system. RESULTS: In the rat brain, the initial level of radioactivity accumulation after injection of [18F]FACBC was low (0.11 percentage injected dose per gram [%ID/g]) at 5 min and increased slightly to 0.26 %ID/g at 60 min. The tumor uptake exhibited a maximum at 60 min (1.72 %ID/g), resulting in a tumor-to-brain ratio increase of 5.58 at 5 min to 6.61 at 60 min. In the patient, the uptake of [18F]FACBC in the tumor exhibited a maximum concentration of 146 nCi/mL at 35 min after injection. The uptake of radioactivity in the normal brain tissue was low, 21 nCi/mL at 15 min after injection, and gradually increased to 29 nCi/mL at 60 min after injection. The ratio of tumor to normal tissue was 6 at 20 min after injection. The [18F]FACBC PET scan showed intense uptake in the left frontal region of the brain. CONCLUSION: The amino acid FACBC can be radiofluorinated for clinical use. [18F]FACBC is a potential PET tracer for tumor imaging. (+info)
Spontaneous pinealoma in a male Crj:CD (SD) IGS rat.
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A pinealoma (benign) was found in a 61-week-old male Crj:CD (SD) IGS rat. The neoplasm was located between the cerebral hemispheres and the cerebellum. Histologically, the tumor cells consisted of two cell types: large, pale-staining cells and small dark-staining cells. A fibrovascular stroma divided the tumor cells into incomplete lobules or nest structures. Relatively numerous mitoses were noted in the tumor cells. Ultrastructurally, the tumor cells contained dense-cored vesicles, approximately 120 nm in diameter. (+info)
Inhibition of angiogenesis induces chromaffin differentiation and apoptosis in neuroblastoma.
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Inhibition of angiogenesis has been shown to reduce tumor growth, metastasis, and tumor microvascular density in experimental models. To these effects we would now like to add induction of differentiation, based on biological analysis of xenografted human neuroblastoma (SH-SY5Y, WAG rnu/rnu) treated with the angiogenesis inhibitor TNP-470. Treatment with TNP-470 (10 mg/kg s.c., n = 15) reduced the tumor growth by 66% and stereological vascular parameters (Lv, Vv, Sv) by 36-45%. The tumor cell apoptotic fraction increased more than threefold, resulting in a decrease in viable tumor cells by 33%. In contrast, the mean vascular diameter (29 microm) and the mean tumor cell proliferative index (49%) were unaffected. TNP-470-treated tumors exhibited striking chromaffin differentiation of neuroblastoma cells, observed as increased expression of insulin-like growth factor II gene (+88%), tyrosine hydroxylase (+96%), chromogranin A, and cellular processes. Statistical analysis revealed an inverse correlation between differentiation and angiogenesis. It is suggested that by inhibiting angiogenesis, TNP-470 induces metabolic stress, resulting in chromaffin differentiation and apoptosis in neuroblastoma. Such agonal differentiation may be the link between angiostatic therapy and tumor cell apoptosis. (+info)
Expression and tissue localization of membrane-type 1, 2, and 3 matrix metalloproteinases in human astrocytic tumors.
(7/10928)
Three different membrane-type matrix metalloproteinases (MT1-, MT2-, and MT3-MMPs) are known to activate in vitro the zymogen of MMP-2 (pro-MMP-2, progelatinase A), which is one of the key MMPs in invasion and metastasis of various cancers. In the present study, we have examined production and activation of pro-MMP-2, expression of MT1-, MT2-, and MT3-MMPs and their correlation with pro-MMP-2 activation, and localization of MMP-2, MT1-MMP, and MT2-MMP in human astrocytic tumors. The sandwich enzyme immunoassay demonstrates that the production levels of pro-MMP-2 in the anaplastic astrocytomas and glioblastomas are significantly higher than that in the low-grade astrocytomas (P<0.05 and P<0.01, respectively), metastatic brain tumors (P<0.05), or normal brains (P<0.01). Gelatin zymography indicates that the pro-MMP-2 activation ratio is significantly higher in the glioblastomas than in other astrocytic tumors (P<0.01), metastatic brain tumors (P<0.01), and normal brains (P<0.01). The quantitative reverse transcription polymerase chain reaction analyses demonstrate that MT1-MMP and MT2-MMP are expressed predominantly in glioblastoma tissues (17/17 and 12/17 cases, respectively), and their expression levels increase significantly as tumor grade increases. MT3-MMP is detectable in both astrocytic tumor and normal brain tissues, but the mean expression level is approximately 50-fold lower compared with that of MT1-MMP and MT2-MMP in the glioblastomas. The activation ratio of pro-MMP-2 correlates directly with the expression levels of MT1-MMP and MT2-MMP but not MT3-MMP. In situ hybridization indicates that neoplastic astrocytes express MT1-MMP and MT2-MMP in the glioblastoma tissues (5/5 cases and 5/5 cases, respectively). Immunohistochemically, MT1-MMP and MT2-MMP are localized to the neoplastic astrocytes in glioblastoma samples (17/17 cases and 12/17 cases, respectively), which are also positive for MMP-2. In situ zymography shows gelatinolytic activity in the glioblastoma tissues but not in the normal brain tissues. These results suggest that both MT1-MMP and MT2-MMP play a key role in the activation of pro-MMP-2 in the human malignant astrocytic tumors and that the gelatinolytic activity is involved in the astrocytic tumor invasion. (+info)
Early induction of angiogenetic signals in gliomas of GFAP-v-src transgenic mice.
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Angiogenesis is a prerequisite for solid tumor growth. Glioblastoma multiforme, the most common malignant brain tumor, is characterized by extensive vascular proliferation. We previously showed that transgenic mice expressing a GFAP-v-src fusion gene in astrocytes develop low-grade astrocytomas that progressively evolve into hypervascularized glioblastomas. Here, we examined whether tumor progression triggers angiogenetic signals. We found abundant transcription of vascular endothelial growth factor (VEGF) in neoplastic astrocytes at surprisingly early stages of tumorigenesis. VEGF and v-src expression patterns were not identical, suggesting that VEGF activation was not only dependent on v-src. Late-stage gliomas showed perinecrotic VEGF up-regulation similarly to human glioblastoma. Expression patterns of the endothelial angiogenic receptors flt-1, flk-1, tie-1, and tie-2 were similar to those described in human gliomas, but flt-1 was expressed also in neoplastic astrocytes, suggesting an autocrine role in tumor growth. In crossbreeding experiments, hemizygous ablation of the tumor suppressor genes Rb and p53 had no significant effect on the expression of VEGF, flt-1, flk-1, tie-1, and tie-2. Therefore, expression of angiogenic signals is an early event during progression of GFAP-v-src tumors and precedes hypervascularization. Given the close similarities in the progression pattern between GFAP-v-src and human gliomas, the present results suggest that these mice may provide a useful tool for antiangiogenic therapy research. (+info)