Biomedical subjects

A von Deimling

Publications and source records attributed to A von Deimling.

At least 19 recordsLinked to original sources

PubMed2001

Early expression of glutamate transporter proteins in ramified microglia after controlled cortical impact injury in the rat.

Traumatic brain injury is followed by increased extracellular glutamate concentration. Uptake of glutamate is mainly mediated by the glial glutamate transporters GLAST and GLT-1. Extent and distribution of GLAST and GLT-1 were studied in a rat model of controlled cortical impact injury (CCII). Western Blot analysis revealed lowest levels of GLAST and GLT-1 with a decrease by 40%-54% and 42%-49% between 24 and 72 h posttrauma. By 8 h after CCII, CSF glutamate levels were increased (10.5 microM vs. 2.56 microM in controls; P < 0.001), reaching maximum values by 48 h. A significant increase in de novo GLAST and GLT-1 expressing ramified microglia was observed within 4 h, reached a stable level by 48 h, and remained high up to 72 h after CCII. Furthermore, ramified microglia de novo expressed the neuronal glutamate transporter EAAC1 after CCII. Following CCII, GLAST/GLT-1 and GFAP coexpressing astrocytes were immediately reduced, reaching minimum levels within 8 h. This reduction of expression could be either due to protein downregulation or loss of astrocytes. At 72 h, a marked population of GLAST- and GLT-1-positive reactive astrocytes appeared. These results support the hypothesis that reduced astrocytic GLAST and GLT-1 protein levels following CCII contribute to evolving secondary injury. Microglia are capable of de novo expressing glutamate transporter proteins, indicating that the expression of glial and neuronal glutamate transporters is not restricted to a specific glial or neuronal lineage. Ramified microglia may play an important compensatory role in the early regulation of extracellular glutamate after CCII.

ATP-Binding Cassette Transporters↗

PubMed2001

Subtyping of oligo-astrocytic tumours by comparative genomic hybridization.

Oligo-astrocytic tumours (OAs) histologically show both oligodendroglial and astrocytic differentiation. Unequivocal criteria for delineation of OAs from pure oligodendroglial (Os) and astrocytic (As) tumours and for grading of OAs are lacking. Molecular genetic analysis may allow for a better characterization of OAs and thereby guide prognostic and therapeutic decisions. Comparative genomic hybridization (CGH) was performed on 39 gliomas with variable phenotypic expression of histological features characteristic of both astrocytic and oligodendroglial differentiation. The results show that OAs are genetically more heterogeneous than Os. In addition to the "-1p/-19q" and "+7/-10" subtypes that have been previously recognized, two additional genetic subtypes, "intermediate" and "other", were identified in the present study. "Intermediate" OAs likely represent progression from "-1p/-19q" tumours. The "other" subtype appears to represent an additional, heretofore unrecognized, genetic pathway(s). Application of rigorously "strict" histopathological criteria, as opposed to "relaxed" criteria, for the selection of oligo-astrocytic tumours resulted in a higher percentage of "-1p/-19q" tumours, but some "-1p/-19q" tumours might be missed. The results suggest that molecular genetic analysis is a useful and valid additional tool for the classification of gliomas, particularly for the significant subset of tumours in which subjective histopathological criteria are insufficient for an unequivocal distinction between Os, As, and mixed OAs.

Adult↗

PubMed2001

Mutational analysis of INI1 in sporadic human brain tumors.

The INI1/SMARCB1/hSNF5 gene on chromosome 22 is frequently mutated in rhabdoid tumors. An association of INI1 mutations with allelic losses on chromosome 22 supports a classical tumor suppressor mechanism. Several brain tumor entities including astrocytomas, glioblastomas and ependymomas are characterized by allelic losses on chromosome 22. In the present study we examined a series of 200 brain tumors by Single-strand conformation polymorphism analysis and direct sequencing for point mutations in INI1. In addition, all tumors were analyzed for homozygous deletions spanning both exons 3 and 8 of INI1. No mutations or homozygous deletions were detected in astrocytomas, glioblastomas, oligodendroglial tumors, neurinomas or medulloblastomas. However, a point mutation could be identified in the single case of plexus carcinoma. Our data suggest that INI1 mutations are involved in the pathogenesis of plexus carcinoma; however, INI1 alterations are not a frequent event in the majority of brain tumor entities.

Base Sequence↗

PubMed2001

Indications for a tumor suppressor gene at 22q11 involved in the pathogenesis of ependymal tumors and distinct from hSNF5/INI1.

Ependymomas account for approximately 9% of all neuroepithelial tumors and represent the most frequent neuroepithelial tumors of the spinal cord. In adults, allelic loss of chromosome arm 22q occurs in up to 60% of the cases studied. Some of these tumors show an altered neurofibromatosis type 2 (NF2) gene; in others, NF2 appears to be unaffected, indicating the involvement of another tumor suppressor gene. Recently, the tumor suppressor gene hSNF5/INI1, located on 22q11.23, has been shown to contribute to the pathogenesis of renal and extrarenal rhabdoid tumors. In addition, this gene may be responsible for a new hereditary syndrome predisposing to a variety of tumors designated "rhabdoid predisposition syndrome." In the present study, we analyzed a series of 53 ependymal tumors of 48 patients [4 myxopapillary ependymomas (WHO grade I), 3 subependymomas (WHO grade I), 18 ependymomas (WHO grade II), 21 anaplastic ependymomas (WHO grade III) and 2 ependymoblastomas (WHO grade IV)] for mutations and homozygous deletions in the coding region of the hSNF5/INI1 gene and for allelic loss of its flanking chromosomal regions in 39 ependymal tumors of 35 patients. Allelic loss was detected in 11 of 35 informative primary ependymal tumors (31%) with a common region of overlap covered by the markers D22S257 and D22S310 on 22q11 including the marker D22S301. However, a detailed molecular analysis of 53 ependymal tumors for mutations and homozygous deletion of the hSNF5/INI1 gene revealed no alterations. We conclude that the hSNF5/INI1 gene is not involved in the pathogenesis of human ependymal tumors with allelic loss on chromosome arm 22q and an intact NF2 locus. In addition, our study localizes a putative ependymoma tumor suppressor gene(s) to a domain of chromosome arm 22q flanked by the microsatellite markers D22S257 and D22S310.

Adolescent↗

PubMed2001

Cloning and characterization of the human GFRA2 locus and investigation of the gene in Hirschsprung disease.

The glial-cell-line-derived neurotrophic factor (GDNF) family receptors alpha (GFRalpha) are cell surface bound glycoproteins that mediate interactions of the GDNF ligand family with the RET receptor. These interactions are crucial to the development of the kidney and some peripheral nerve lineages. In humans, mutations of RET or RET ligands are associated with the congenital abnormality Hirschsprung disease (HSCR) in which nerves and ganglia of the hind gut are absent. As the GFRalpha family are required for normal activation of the RET receptor, they are also candidates for a role in HSCR. The GFRA2 gene, which is required for the development of the myenteric nerve plexus, is an excellent candidate gene for HSCR. In this study, we cloned the human GFRA2 locus, characterized the gene structure, and compared it with other GFRA family members. We further investigated the GFRA2 gene for mutations in a panel of HSCR patients. GFRA2 has nine coding exons that are similar in size and organization to those of other GFRA family genes. We identified six sequence variants of GFRA2, four of which did not affect the amino acid sequence of the GFRalpha-2 protein. Two further changes that resulted in amino acid substitutions were found in exon 9 and were predicted to lie in the amino acid sequence encoding the glycosylphosphatidylinositol-linkage signal of GFRalpha-2. There was no difference in frequency of any of the sequence variants between control and HSCR populations. Our data indicate that members of the GFRA gene family are closely related in intron/exon structure and in sequence. We have not detected any correlation between sequence variants of GFRA2 and the HSCR phenotype.

Base Sequence↗

PubMed2001

TP53 gene mutations, nuclear p53 accumulation, expression of Waf/p21, Bcl-2, and CD95 (APO-1/Fas) proteins are not prognostic factors in de novo glioblastoma multiforme.

Glioblastoma multiforme (WHO grade IV; GBM) is the most common primary brain tumor with a median survival of less than one year despite multimodal treatment regimens. However, a small subgroup of GBM patients has a better clinical outcome, with a small number of patients surviving several years. Apoptosis, a genetically determined program of cell suicide, may be induced as a consequence of critical DNA damage. However, due to defects in the signaling pathways, cancer cells may escape apoptosis, despite carrying irreversible DNA damage. In the present study, we have analyzed tumors of two age-matched, equally treated groups of GBM patients with different postoperative time to tumor progression (TTP), defined as 'short-term' for TTP of less than 6 months (n = 54), and 'long-term' for TTP of more than 12 months (n = 39) for alterations in apoptosis regulatory pathways: Mutations of the TP53 tumor suppressor gene and/or nuclear accumulation of its gene product p53, expression of Waf/p21, CD95 (Apo1/Fas), and Bcl-2. TP53 mutations were found in 12 out of 54 (22%) GBMs of short-term survivors and 8 out of 35 (23%) tumors of long-term survivors; the respective numbers for nuclear p53 protein accumulation were 12/53 (23%) and 10/37 (27%). Waf1/p21 expression was found in 13/53 (25%) tumors of short-term survivors and 9/35 (26%) GBMs of long-term survivors. The respective numbers for Bcl-2 expression were 25/42 (60%) and 22/36 (61%) and for CD95 (Apo1/Fas) expression 20/49 (41%) and 14/36 (39%) GBMs. The percentage of alterations in genes/proteins involved in the apoptotic pathway investigated here was virtually identical in the two groups of clinically different GBM patients. Thus, our data imply that none of these alterations investigated per se has a strong impact on the overall survival of GBM patients.

Adult↗

PubMed2001

Mutational analysis of TSC1 and TSC2 genes in gangliogliomas.

Gangliogliomas constitute the most frequent tumour entity in patients with temporal lobe epilepsy. The characteristic histopathological admixture of glial and neuronal elements, the focal nature and their differentiated phenotype and benign biological behaviour suggest an origin from a developmentally compromised or dysplastic precursor lesion. The present study analysed TSC1 and TSC2 genes as potential candidates involved in the pathogenesis of this intriguing neoplasm. Recent data suggest that both genes play a role in cortical differentiation and growth control. DNA sequence analysis of TSC1 and TSC2 was studied in 20 patients with gangliogliomas. Fifteen of these tumours (75%) carried polymorphisms in the TSC2 gene. The frequency of these polymorphisms was significantly increased in intron 4 (12.5%) and exon 41 (15%) compared to control individuals (8.1 and 6.5%, respectively, n = 100). A somatic mutation in intron 32 of the TSC2 gene was encountered in one patient. In the TSC1 gene, seven polymorphisms occurred as a combination of base exchanges in exon 14 and intron 13. No mutations were observed in this gene. Laser microdissection and harvesting of individual neuronal and glial elements identified the intron 32 mutation within the glial portion but not in dysplastic neurones of the tumour. The data demonstrate numerous polymorphisms as well as a novel TSC2 mutation in gangliogliomas from patients with chronic epilepsies. The selective detection of the TSC2 mutation within the glial component of a ganglioglioma suggests that the glioma portion has undergone clonal evolution in this case.

Brain Neoplasms↗

PubMed2001

INI1 mutations in meningiomas at a potential hotspot in exon 9.

Rhabdoid tumours have been shown to carry somatic mutations in the INI1 (SMARCB1/hSNF5) gene. A considerable fraction of these tumours exhibit allelic losses on chromosome 22. Allelic loss on 22q also is characteristic for meningiomas, however most of these alterations are considered to be associated with mutations of the NF2 gene. We examined a series of 126 meningiomas for alterations in the INI1 gene. Four identical somatic mutations in exon 9 were detected resulting in an exchange of Arg to His in position 377 of INI1. Our observations were reproduced both by using DNA from a new round of extraction and by employing overlapping primers. This mutational hotspot therefore appears to be an important target in the formation of a fraction of meningiomas. In addition, 4 novel polymorphisms of INI1 were characterized. Our data indicate that the INI1 is a second tumour suppressor gene on chromosome 22 that may be important for the genesis of meningiomas.

Alleles↗

PubMed2001

Loss of NF1 alleles distinguish sporadic from NF1-associated pilocytic astrocytomas.

Pilocytic astrocytomas classified as WHO grade I typically arise in childhood and upon complete surgical removal carry a favorable prognosis. Children with neurofibromatosis 1 (NF1) have a vastly increased risk for pilocytic astrocytomas, especially for those of the optic nerve. Using 4 intragenic NF1 microsatellite markers, we examined losses of NF1 alleles on the long arm of chromosome 17 in 12 NF1-associated and 25 sporadic pilocytic astrocytomas. The TP53 gene region on the short arm of chromosome 17 was also examined in these tumors using 3 markers. Loss of 1 NF1 allele was detected in 11 of 12 (92%) informative NF1-associated pilocytic astrocytomas. In contrast, only 1 of 24 informative (4%) sporadic pilocytic astrocytomas exhibited allelic loss in the NF1 region. Among the 11 NF1-associated tumors with NF1 loss, 5 had also lost alleles on 17p. The high rate of NF1 allele loss in NF1-associated pilocytic astrocytomas suggests a tumor initiating or promoting action of the NF1 gene in these patients. On the other hand, the much lower rate of NF1-allele loss in sporadic pilocytic astrocytomas argues for only minor importance of NF1 in that patient group. The present data support different mechanisms in the formation of NF1-associated and sporadic pilocytic astrocytomas.

Adolescent↗

PubMed2001

Clonal analysis in glioblastoma with epithelial differentiation.

Epithelial differentiation in glioblastomas (GBM) may be associated with circumscribed growth and focal keratin expression resembling carcinoma metastasis. Therefore these rare lesions can pose a diagnostic problem suggesting coincidental occurrence of two separate neoplasms. However molecular analysis should succeed in establishing a common origin of seemingly unrelated tumor samples. Five GBMs exhibiting epithelial differentiation were microdissected and analyzed for mutations in the TP53 gene. SSCP analysis of exons 5-8 was followed by direct sequencing of aberrantly migrating fragments. TP53 mutations were identified in tumors from two of five patients. A G-->T transversion in codon 176 was detected in a tumor, initially diagnosed as metastases of unknown origin, however, a later autopsy revealed GBM. In this lesion, the mutation was observed in both, areas of astrocytic differentiation and areas of epithelial differentiation. One tumor diagnosed as GBM with epithelial differentiation carried C-->T transition in codon 211 in both, areas of astrocytic and epithelial differentiation. Thus, molecular analysis proved clonality in two GBMs with epithelial differentiation, thereby excluding a collision tumor. The present data support the concept of clonal origin of these morphologically heterogeneous lesions.

Astrocytes↗

PubMed2001

Analysis of the RET, GDNF, EDN3, and EDNRB genes in patients with intestinal neuronal dysplasia and Hirschsprung disease.

BACKGROUND: Hirschsprung disease (HSCR) is a frequent congenital disorder with an incidence of 1 in 5000 live births, characterised by the absence of parasympathetic intramural ganglion cells in the hindgut resulting in intestinal obstruction in neonates and severe constipation in infants and adults. Intestinal neuronal dysplasia (IND) shares clinical features with HSCR but the submucosal parasympathetic plexus is affected. IND has been proposed as one of the most frequent causes of chronic constipation and is often associated with HSCR. METHODS: We examined 29 patients diagnosed with sporadic HSCR, 20 patients with IND, and 12 patients with mixed HSCR/IND for mutations in the coding regions of the RET, GDNF, EDNRB, and EDN3 genes. The entire coding regions were analysed by single strand conformational polymorphism and DNA sequencing. RESULTS: Only three RET mutations were detected in patients with HSCR. In patients with IND or a mixed HSCR/IND phenotype, no mutations in these genes were observed. While HSCR and HSCR/IND showed over representation of a specific RET polymorphism in exon 2, IND exhibited a significantly lower frequency comparable with that of controls. CONCLUSIONS: The mutation frequency found in our sporadic HSCR patients (10%) and the allelic distribution of RET polymorphisms are comparable with earlier published data. A significantly different allelic distribution in an established HSCR associated polymorphism argues against common genetic pathways for HSCR and IND.

Alleles↗

PubMed2001

Malignant transformation of a gangliocytoma/ganglioglioma into a glioblastoma multiforme: a molecular genetic analysis. Case report.

A gangliocytoma/ganglioglioma with no atypical or malignant features was subtotally resected from the right temporal lobe of a 16-year-old woman. A second resection was performed 8 years later to treat a locally recurrent lesion with increased cellularity that was diagnosed as a World Health Organization Grade II ganglioglioma on the basis of neuropathological examination. Molecular analysis of the recurrent tumor revealed a TP53 gene mutation, but no amplification of the epidermal growth factor receptor (EGFR) gene. Radiotherapy (60 Gy) was administered after the second resection. The patient returned 1 year later with a second focal recurrence. The specimen obtained during the third resection of tumor exhibited exclusively astrocytic differentiation, cellular pleomorphism with multinucleated cells, high mitotic activity, and endothelial proliferation. Therefore, the tumor was diagnosed to be a glioblastoma multiforme (GBM). Molecular analysis of tumor DNA from the second recurrent tumor demonstrated the presence of the TP53 mutation, which previously had been observed in the first recurrent tumor, but again no evidence of EGFR amplification. Findings demonstrate that the presence of TP53 mutation in progressed gangliogliomas should be interpreted as a progression-associated mutation rather than a consequence of treatment. This is the first report to indicate that the molecular pathways of gangliocytomas/gangliogliomas progressing to become GBMs may parallel those of diffuse astrocytomas progressing to become GBMs.

Adolescent↗

PubMed2000

Mapping of the chromosome 19 q-arm glioma tumor suppressor gene using fluorescence in situ hybridization and novel microsatellite markers.

Allelic loss of chromosome arm 19q is a frequent event in human diffuse glioma, suggesting the presence of a tumor suppressor gene. Previous loss of heterozygosity (LOH) analyses have mapped this gene to a 1.4-megabase interval, between the genetic markers D19S412 and STD. Further narrowing of this interval has been limited by the resolution of mapped polymorphic markers. In the present study, we have used genomic clones mapped to 19q as fluorescence in situ hybridization (FISH) probes to map the breakpoints of 13 gliomas with 19q13.3 deletion boundaries. In addition, we have developed three new polymorphic microsatellite markers (D19S1180, D19S1181, and D19S1182) that map between D19S412 and STD and have used these new markers to identify two gliomas with small deletions between the D19S412 and STD markers. Collectively, these data suggest that the region of common deletion may be as narrow as 150 kb and should facilitate future efforts to identify the glioma 19q tumor suppressor gene.

Chromosome Deletion↗

PubMed2000

Long-term survival of glioblastoma multiforme: importance of histopathological reevaluation.

The overall prognosis for patients with glioblastoma multiforme is extremely poor. However, a small proportion of patients enjoy prolonged survival. This study investigated retrospectively the extent to which erroneous histopathological classification may contribute to long-term survival of patients initially diagnosed with "glioblastoma multiforme." We compared two age- and gender-matched patient groups with different postoperative time to tumor progression (TTP), defined as "short-term" for TTP of less than 6 months (n = 54), and "long-term" for TTP of more than 12 months (n = 52). Histological specimens of the corresponding tumors, all primarily diagnosed as glioblastoma multiforme, were reevaluated according to the current World Health Organization (WHO) classification of central nervous system tumors, with the investigators being blinded to clinical outcome. Among the tumors from short-term TTP patients, one tumor (2%) was reclassified as anaplastic oligoastrocytoma (WHO grade III) while the remaining 53 were confirmed as glioblastoma multiforme. In contrast, 13 tumors (25%) from the long-term TTP patients were reclassified, mostly as anaplastic oligodendroglioma (WHO grade III; n = 7) or anaplastic oligoastrocytoma (WHO grade III, n = 2), respectively. In addition, three were reclassified as anaplastic astrocytoma (WHO grade III), and one was identified as anaplastic pilocytic astrocytoma (WHO grade III). Our data indicate that a sizable proportion of glioblastoma patients with long-term survival actually carry malignant gliomas with oligodendroglial features. The correct histopathological recognition of these tumors has not only prognostic but also therapeutic implications, since oligodendroglial tumors are more likely to respond favorably to chemotherapy.

Adult↗

PubMed2000

Molecular analysis of the TSC1 and TSC2 tumour suppressor genes in sporadic glial and glioneuronal tumours.

Reduced expression of the TSC2 tumour suppressor gene product, tuberin, has been reported in sporadic astrocytomas, suggesting that the TSC genes may play a role in formation of sporadic glial or glioneuronal tumours. We studied paired constitutional and tumour DNA samples from 100 patients with sporadic glial and glioneuronal tumours for loss of heterozygosity (LOH) at the TSC1 and TSC2 loci using a combination of seven previously reported and seven novel polymorphic markers. LOH was seen in 1/16 astrocytomas, 3/15 ependymomas, 5/16 gangliogliomas, 2/14 glioblastoma multiforme, 0/7 oligodendrogliomas, 0/7 tumours of mixed oligodendrocytic/astrocytic histology, 2/11 pilocytic astrocytomas and 0/1 subependymal giant cell astrocytomas informative at both loci. However, SSCP screening of all coding exons of the TSC1 or TSC2 genes in the tumours displaying LOH, and of both genes in 21 gangliogliomas, revealed no intragenic mutations. The lack of demonstrable inactivation of both alleles of either TSC gene in any of the tumours investigated suggests that they do not play a frequent role in the aetiology of sporadic glial or glioneuronal tumours.

Alleles↗

PubMed2000

Effects of barium on stimulus-induced rises of [K+]o in human epileptic non-sclerotic and sclerotic hippocampal area CA1.

In the hippocampus of patients with therapy-refractory temporal lobe epilepsy, glial cells of area CA1 might be less able to take up potassium ions via barium-sensitive inwardly rectifying and voltage-independent potassium channels. Using ion-selective microelectrodes we investigated the effects of barium on rises in [K+]o induced by repetitive alvear stimulation in slices from surgically removed hippocampi with and without Ammon's horn sclerosis (AHS and non-AHS). In non-AHS tissue, barium augmented rises in [K+]o by 147% and prolonged the half time of recovery by 90%. The barium effect was reversible, concentration dependent, and persisted in the presence of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), N-methyl-D-aspartate (NMDA) and gamma-aminobutyric acid [GABA(A)] receptor antagonists. In AHS tissue, barium caused a decrease in the baseline level of [K+]o. In contrast to non-AHS slices, in AHS slices with intact synaptic transmission, barium had no effect on the stimulus-induced rises of [K+]o, and the half time of recovery from the rise was less prolonged (by 57%). Under conditions of blocked synaptic transmission, barium augmented stimulus-induced rises in [K+]o, but only by 40%. In both tissues, barium significantly reduced negative slow-field potentials following repetitive stimulation but did not alter the mean population spike amplitude. The findings suggest a significant contribution of glial barium-sensitive K+-channels to K+-buffering in non-AHS tissue and an impairment of glial barium-sensitive K+-uptake in AHS tissue.

2-Amino-5-phosphonovalerate↗

PubMed2000

Comprehensive allelotype and genetic anaysis of 466 human nervous system tumors.

Brain tumors pose a particular challenge to molecular oncology. Many different tumor entities develop in the nervous system and some of them appear to follow distinct pathogenic routes. Molecular genetic alterations have increasingly been reported in nervous system neoplasms. However, a considerable number of affected genes remain to be identified. We present here a comprehensive allelotype analysis of 466 nervous system tumors based on loss of heterozygosity (LOH) studies with 129 microsatellite markers that span the genome. Specific alterations of the EGFR, CDK4, CDKN2A, TP53, DMBT1, NF2, and PTEN genes were analyzed in addition. Our data point to several novel genetic loci associated with brain tumor development, demonstrate relationships between molecular changes and histopathological features, and further expand the concept of molecular tumor variants in neuro-oncology. This catalogue may provide a valuable framework for future studies to delineate molecular pathways in many types of human central nervous system tumors.

Alleles↗

PubMed2000

Low frequency of SV40, JC and BK polyomavirus sequences in human medulloblastomas, meningiomas and ependymomas.

Several reports have suggested a role for polyomaviruses in the pathogenesis of human brain tumors. This potential involvement is not conclusively resolved. For the present study, a highly sensitive PCR-assay with fluorescence-labelled primers was developed to search for polyomavirus sequences in human brain tumor and control DNA samples. The assay was shown to detect approximately one viral large T-antigen (TAg) gene per 250 cells. We identified simian virus 40 (SV40)-like sequences in 2/116 medulloblastomas, in 1/131 meningiomas, in 1/25 ependymomas and in 1/2 subependymomas. A single case of ependymoma contained SV40 VP-1 late gene sequences. Moreover, one of the meningioma samples showed JC virus sequences. In contrast, 60 hepatoblastoma samples and 31 brain samples from schizophrenic patients were consistently negative. BK virus sequences were not detectable in any of our samples. Immunohistochemical analysis of two SV40 positive tumor biopsies failed to detect large TAg in the tumor cells. In the JC positive meningioma, immunoreactivity for the viral late gene product (VP-1) was not observed. Our data do not entirely rule out SV40 and JC virus as an initiative agent with a hit-and-run mechanism. However the low frequency of virus sequences and the absence of TAg protein expression argue against a major role of these viruses in the pathogenesis of human medulloblastomas, meningiomas and ependymomas.

BK Virus↗