| 1. |
- Hede, Sanna-Maria, et al.
(författare)
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GFAP promoter driven transgenic expression of PDGFB in the mouse brain leads to glioblastoma in a Trp53 null background
- 2009
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Ingår i: Glia. - : Wiley. - 0894-1491 .- 1098-1136. ; 57:11, s. 1143-1153
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Tidskriftsartikel (refereegranskat)abstract
- Glioblastomas are the most common and malignant astrocytic brain tumors in human adults. The tumor suppressor gene TP53 is commonly mutated and/or lost in astrocytic brain tumors and the TP53 alterations are often found in combination with excessive growth factor signaling via PDGF/PDGFRalpha. Here, we have generated transgenic mice over-expressing human PDGFB in brain, under control of the human GFAP promoter. These mice showed no phenotype, but on a Trp53 null background a majority of them developed brain tumors. This occurred at 2-6 months of age and tumors displayed human glioblastoma-like features with integrated development of Pdgfralpha+ tumor cells and Pdgfrbeta+/Nestin+ vasculature. The transgene was expressed in subependymal astrocytic cells, in glia limitans, and in astrocytes throughout the brain substance, and subsequently, microscopic tumor lesions were initiated equally in all these areas. With tumor size, there was an increase in Nestin positivity and variability in lineage markers. These results indicate an unexpected plasticity of all astrocytic cells in the adult brain, not only of SVZ cells. The results also indicate a contribution of widely distributed Pdgfralpha+ precursor cells in the tumorigenic process.
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| 2. |
- Hägerstrand, Daniel, et al.
(författare)
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Characterization of an imatinib-sensitive subset of high-grade human glioma cultures
- 2006
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Ingår i: Oncogene. - : Springer Science and Business Media LLC. - 0950-9232 .- 1476-5594. ; 25:35, s. 4913-4922
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Tidskriftsartikel (refereegranskat)abstract
- High-grade gliomas, including glioblastomas, are malignant brain tumors for which improved treatment is urgently needed. Genetic studies have demonstrated the existence of biologically distinct subsets. Preliminary studies have indicated that platelet-derived growth factor (PDGF) receptor signaling contributes to the growth of some of these tumors. In this study, human high-grade glioma primary cultures were analysed for sensitivity to treatment with the PDGF receptor inhibitor imatinib/Glivec/Gleevec/STI571. Six out of 15 cultures displayed more than 40% growth inhibition after imatinib treatment, whereas seven cultures showed less than 20% growth inhibition. In the sensitive cultures, apoptosis contributed to growth inhibition. Platelet-derived growth factor receptor status correlated with imatinib sensitivity. Supervised analyses of gene expression profiles and real-time PCR analyses identified expression of the chemokine CXCL12/SDF-1 (stromal cell-derived factor 1) as a predictor of imatinib sensitivity. Exogenous addition of CXCL12 to imatinib-insensitive cultures conferred some imatinib sensitivity. Finally, coregulation of CXCL12 and PDGF alpha-receptor was observed in glioblastoma biopsies. We have thus defined the characteristics of a novel imatinib-sensitive subset of glioma cultures, and provided evidence for a functional relationship between imatinib sensitivity and chemokine signaling. These findings will assist in the design and evaluation of clinical trials exploring therapeutic effects of imatinib on malignant brain tumors.
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| 3. |
- Hägerstrand, Daniel, et al.
(författare)
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Gene expression analyses of grade II gliomas and identification of rPTPbeta/ as a candidate oligodendroglioma marker
- 2008
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Ingår i: Neuro-Oncology. - : Oxford University Press (OUP). - 1522-8517 .- 1523-5866. ; 10:1, s. 2-9
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Tidskriftsartikel (refereegranskat)abstract
- Grade 11 gliomas are morphologically and clinically heterogeneous tumors for which histopathological typing remains the major tool for clinical classification. To what extent the major histological subtypes-astrocytomas, oligodendrogliomas, and oligoastrocytomas-constitute true biological entities is largely unresolved. Furthermore, morphological classification is often ambiguous and would be facilitated by specific subtype markers. In this study, 23 grade II gliomas were expression-profiled and subjected to hierarchical clustering. All six oligodendrogliomas were grouped together in one of two major clusters; a significant correlation was thus observed between gene expression and histopathological subtype. Supervised analyses were performed to identify genes differentiating oligodendrogliomas from other grade II tumors. In a leave-one-out test using 10 features for classification, 20 out of 23 tumors were correctly classified. Among the most differentially expressed genes was rPT beta/zeta. The expression of the rPTP beta/zeta protein in oligodendrogliomas and astrocytomas was further validated by immunohistochemistry in an independent set of tumors. All 11 oligodendrogliomas of this set displayed strong staining. In contrast, neoplastic astrocytes were mostly negative for rPTP beta/zeta staining. In summary, this study demonstrates a correlation between gene expression pattern and histological subtype in grade 11 gliomas. Furthermore, the results from the immunohistochemical analyses of rPTP beta/zeta expression should prompt further evaluation of this protein as a novel oligodendroglioma marker.
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| 4. |
- Meletis, Konstantinos, et al.
(författare)
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p53 suppresses the self-renewal of adult neural stem cells
- 2006
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Ingår i: Development. - : The Company of Biologists. - 0950-1991 .- 1477-9129. ; 133:2, s. 363-369
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Tidskriftsartikel (refereegranskat)abstract
- There is increasing evidence that tumors are heterogeneous and that a subset of cells act as cancer stem cells. Several proto-oncogenes and tumor suppressors control key aspects of stem cell function, suggesting that similar mechanisms control normal and cancer stem cell properties. We show here that the prototypical tumor suppressor p53, which plays an important role in brain tumor initiation and growth, is expressed in the neural stem cell lineage in the adult brain. p53 negatively regulates proliferation and survival, and thereby self-renewal, of neural stem cells. Analysis of the neural stem cell transcriptome identified the dysregulation of several cell cycle regulators in the absence of p53, most notably a pronounced downregulation of p21 expression. These data implicate p53 as a suppressor of tissue and cancer stem cell self-renewal.
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| 5. |
- Qu, Mingqi, et al.
(författare)
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DLG3/SAP102 protein expression in malformations of cortical development : A study of human epileptic cortex by tissue microarray
- 2009
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Ingår i: Epilepsy Research. - : Elsevier BV. - 0920-1211 .- 1872-6844. ; 84:1, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- The human DLG3 gene encodes the synapse-associated protein 102 (SAP102), which is concentrated in the postsynaptic densities of excitatory synapses and involved in receptor-mediated synaptic transmission via binding to the NR2B subunit of the NMDA receptor. In this study, we investigated the expression and cellular distribution of the DLG3/SAP102 protein in human epileptic cortex. Tissue microarrays of a large number of specimens from patients operated for medically intractable epilepsy were used for immunohistochemical screening with anti-DLG3 antibody. The cellular distribution of the protein was further investigated in samples of malformations of cortical development, and the amount of DLG3 protein in the total homogenate and in the postsynaptic membrane fraction of these samples was quantified by Western blot. We found a strictly neuronal expression of DLG3/SAP102 in epileptogenic cortex as well as in non-epileptic human cortex used for control. In focal cortical dysplasia and tuberous sclerosis complex, the protein was expressed in most neurons including dysplastic neurons, but not in giant cells. Increased expression of DLG3 protein was observed in the postsynaptic membrane fraction of patients with focal cortical dysplasia. Double-labeling experiments confirmed the exclusive neuronal character of the DLG3 expressing cells and the co-localization of the DLG3 protein with the NR2B subunit. Our results suggest a putative role for DLG3/SAP102 in cortical hyperexcitability and epileptogenicity of malformations of cortical development.
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| 6. |
- Qu, Mingqi, et al.
(författare)
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Genetically distinct astrocytic and oligodendroglial components in oligoastrocytomas
- 2007
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Ingår i: Acta Neuropathologica. - : Springer Science and Business Media LLC. - 0001-6322 .- 1432-0533. ; 113:2, s. 129-136
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Tidskriftsartikel (refereegranskat)abstract
- Oligoastrocytomas are glial tumours consisting of a mixture of neoplastic astrocytic and oligodendroglial cells. Genetic alterations of oligoastrocytomas include loss of heterozygosity of chromosomes 1p and/or 19q (LOH 1p/19q), typically occurring in oligodendrogliomas, and mutations of TP53, frequently occurring in astrocytomas. To investigate whether these neoplastic cell types in oligoastrocytomas have different genetic profiles, we examined the two different components of oligoastrocytomas in comparison with the histological diagnosis of the specific tumour area for LOH 1p/19q and TP53 mutations by using microdissection technique. We found a variety of lost markers for 1p and 19q, and the presence of two different TP53 mutations in the tumour samples. In the majority of cases (9/11), the oligodendroglial and astrocytic components of an individual oligoastrocytoma displayed the same genotype. We present two cases of biphasic oligoastrocytomas with aberrant findings, suggesting the coexistence of genetically and morphologically distinct tumour cell clones in these tumours. In one case, the oligodendroglial part of the tumour showed LOH19q, whereas the astrocytic part showed TP53 mutation (codon 273). In another case, we found LOH 1p/19q in the oligodendroglial component, but two retained areas on chromosome 1p in the astrocytic component of the tumour. No evidence was found for the coexistence of tumour cells with the two genotypical changes within the same morphological region of one individual tumour. The two cases of biphasic oligoastrocytomas in our sample that display a different genotype in the astrocytic and oligodendroglial part of the tumour show that different components of an oligoastrocytoma may be derived from different cell clones during neoplastic transformation.
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| 7. |
- Ren, Zhi-Ping, et al.
(författare)
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Molecular genetic analysis of p53 intratumoral heterogeneity in human astrocytic brain tumors
- 2007
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Ingår i: Journal of Neuropathology and Experimental Neurology. - : Oxford University Press (OUP). - 0022-3069 .- 1554-6578. ; 66:10, s. 944-954
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Tidskriftsartikel (refereegranskat)abstract
- We investigated genetic heterogeneity of astrocytic gliomas using p53 gene mutations as a marker. Different parts of morphologically heterogeneous astrocytic gliomas were micro-dissected, and direct DNA sequencing of p53 gene exons 5 through 8 was performed. Thirty-five glioma samples and tumor-adjacent normal-appearing brain tissue from I I patients were analyzed. Sixteen different p53 gene mutations were found in 7 patients. We found that some tumors were devoid of p53 gene mutations, whereas other tumors carried I or often several (up to 3) different mutations. The mutations were present in grade II, III, and IV astrocytic glioma areas. Both severe functionally dead mutants and mutants with remaining transcriptional activity could be observed in the same tumor. We observed that morphologically different parts of a glioma could carry different or similar mutations in the p53 gene and could be either associated or not associated with the locus of heterozygosity at the mutant site. Coexistence of p53 gene mutations and the locus of heterozygosity was common, at least in astrocytomas grade III and in glioblastomas, and also occurred in astrocytoma grade 11 areas. These results support the notion that intratumoral heterogeneity in brain tumors originates from different molecular defects. Our results are of importance for a further understanding of the molecular mechanisms behind failure to treat glioma patients.
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| 8. |
- Zhang, Xiao-Qun, et al.
(författare)
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Gli1 is not required for Pdgfralpha expression during mouse embryonic development
- 2005
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Ingår i: Differentiation. - : Elsevier BV. - 0301-4681 .- 1432-0436. ; 73:2-3, s. 109-19
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Tidskriftsartikel (refereegranskat)abstract
- Pdgfra is expressed in the mesenchyme of multiple organs during embryonic development and Pdgfrα is involved in cell proliferation, differentiation, migration, and apoptosis in many tissues. A fine-tuned regulation of gene transcription is required to achieve these effects. To investigate if the Shh signaling pathway is involved in the tightly regulated Pdgfra expression during embryogenesis, we systematically compared Gli1 and Pdgfrα mRNA expression patterns in vivo from mouse embryonic day 9.5 to 14.5. We found that an initial partly overlapping expression of Gli1 and Pdgfrα in the mesenchyme of foregut and somites was changed to different expression patterns when the mesenchyme differentiated into specialized structures such as intestinal villi and chondrocytes. Gli1 and Pdgfra were also expressed differently in the developing lung, heart, central nervous system, skin, tooth, and eye. Importantly, neither Pdgfrα mRNA patterns nor levels were altered in Ihh mutant embryos although Gli1 and Ptc mRNA levels were dramatically reduced. Our results demonstrate that Gli1 is not required to induce Pdgfra expression during embryonic bone development, and are consistent with previous findings that Pdgfrα and Hh pathways serve different functions in, e.g., bone, gut, and lung development. However, we cannot exclude the possibility that Glis can have more complex regulatory effects on Pdgfra gene activity, nor can we exclude such effects in pathological conditions.
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