53 research outputs found
Expression of JC virus T-antigen in a patient with MS and glioblastoma multiforme
No full textObjective: To investigate the presence of human polyomavirus JC virus genome and the expression of the viral oncoprotein T-antigen in neoplastic cells of a patient with MS and a glioblastoma multiforme. Background: The postmortem examination of an immunocompetent patient with a neurologic disorder revealed the concurrence of MS plaques in the white matter of the brain and a glioblastoma multiforme in the region of the thalamus. Methods and Results: PCR analysis of DNA from demyelinated plaques and the tumor area using primers derived from specific regions of the JC virus genome revealed the presence of viral DNA corresponding to the viral early and late genes. Further examination of the samples for the JC virus regulatory region identified the presence of sequences identical to JC virus Mad-4 and JC virus W1 viral isolates in the tumor and the demyelinated regions. Results from immunohistochemistry showed the detection of the viral early protein, T-antigen, and the cellular tumor suppressor protein, p53, in the nuclei of neoplastic cells. Interestingly, expression of T-antigen, but not p53, was observed in neurofilament-positive cells with neuronal morphology and in glial fibrillary acidic protein-positive astrocytes in the cortex juxtaposed to the MS plaques. Examination of viral late gene expression by immunohistochemistry showed no evidence for viral capsid proteins, thus ruling out productive replication of JC virus in the tumor and MS demyelinated plaques. Conclusions: These observations provide molecular and clinical evidence of the association of JC virus in the brain of a patient with concurrent glioblastoma multiforme and MS
Expression of a human polyomavirus oncoprotein tumour suppressor proteins in medulloblastomas
No full textAims - Although the aetiology of medulloblastoma remains elusive several lines of evidence suggest an association with the human neurotropic polyomavirus JC its oncoprotein T antigen. The tumour forming properties of JC virus T antigen are the result at least in part of its ability to bind inactivate tumour suppressor/ cell cycle regulatory proteins such as p53 the retinoblastoma family of proteins. Methods - To examine potential relations between these factors immunohisto-chemistry was used to determine associations between the T antigen the expression of p53 the retinoblastoma proteins pRb p107 Rb2/p130 in eight medulloblastomas. Results - Only the three medulloblastomas with T antigen expression also showed nuclear positivity with antibodies to p53. Although immunohistochemistry detected nuclear labelling for pRb in five of the cases, the three that were positive for T antigen showed the highest pRb labelling. The retinoblastoma related proteins p107 and Rb2/p130 were also immunopositive in most T antigen positive medulloblastomas. Double label immunohistochemistry also demonstrated p53 and pRb positivity in the same cells that were T antigen positive. Conclusions - These correlations suggest that associations between T antigen and p53 and/or T antigen and pRb occur in some of these tumours. These data provide indirect evidence that JC virus, acting through T antigen, might be involved in the formation and progression of medulloblastoma
Expression of human neurotropic polyomavirus JCV late gene product agnoprotein in human medulloblastoma
No full textBACKGROUND: The human neurotropic polyomavirus, JCV, contains an open reading frame within the late region of the viral genome that encodes a 71-amino-acid protein, agnoprotein. Because accumulating evidence supports an association between JCV infection and human brain tumors, including medulloblastomas, we assessed the presence of JCV Agno gene sequences and the expression of agnoprotein in a series of 20 well-characterized medulloblastomas. METHODS: Formalin-fixed, paraffin-embedded tumor tissue samples were used for Agno gene amplification and for immunohistochemical analysis. Adjacent sections were stained with an antibody to agnoprotein and with antibodies to cellular structural and regulatory proteins, including the JCV early gene product, T antigen. RESULTS: Analysis of amplified DNA from paraffin-embedded samples revealed the presence of the Agno gene in 11 (69%) of 16 samples. Immunohistochemical analysis showed cytoplasmic localization and widespread distribution of agnoprotein in the neoplastic cells in 11 (55%) of 20 samples. The JCV early gene product, T antigen, was present in the nucleus of some, but not all, of the neoplastic cells. Some medulloblastoma samples that expressed agnoprotein had no sign of T-antigen expression. p53 was detected in only six of the 11 tumors in which agnoprotein was expressed. None of the 20 samples showed expression of the viral late capsid proteins, ruling out productive infection of the tumor cells with JCV. CONCLUSIONS: Our data provide evidence that the JCV late gene encoding the auxiliary agnoprotein is expressed in tumor cells. The finding of agnoprotein expression in the absence of T-antigen expression suggests a potential role for agnoprotein in pathways involved in the development of JCV-associated medulloblastomas
The cellular response of JC Virus T-Antigen induced brain tumor implants to a murine intra-ocular model
No full textIn order to define the immunologic response to central nervous system tumors in a controlled fashion, we compared xenogeneic, allogeneic and syngeneic transplants of JC virus-induced neural tumor cell aggregates implanted into anterior ocular chambers of mice. Semiquantitative assessment of the level of leukocyte common antigen (CD45) of the transplants by immunohistochemistry was used to gauge rejection. Reticulin staining was used to monitor vascularization. Immunoreactivity to the viral oncoprotein, T- antigen, was confirmed by immunohistochemistry and immunoprecipitation/Western blot analysis. The results demonstrated that transplants were viable at all time-points and developed vascularization as early as three days after transplantation. Xenotransplants, 13-days post- transplantation, and allogeneic transplants, 25 days post-transplantation were infiltrated with polymorphonuclear leukocytes. Fewer CD45 positive cells were demonstrated in syngeneic transplants. High levels of JCV T-antigen stimulated rejection in syngeneic transplants. These results establish a model for further investigation of the natural and induced immunologic response to central nervous system tumors. (C) 2000 Published by Elsevier Science B.V
Detection of human neurotropic JC virus DNA sequence and expression of the viral oncogenic protein in pediatric medulloblastomas
No full textMedulloblastoma represents greater than 25% of childhood intracranial neoplasms and is considered a highly malignant tumor. This tumor, which arises predominantly in the cerebellar vermis, preferentially affects children between the ages of 5 and 15. Although the etiology of medulloblastomas in humans remains unknown, results from several experiments have indicated that the human neurotropic JC virus (JCV) is able to induce cerebellar neoplasms in rodents that exhibit a phenotype similar to that of human medulloblastomas. JCV is a polyomavirus that is widespread in the human population, with infection occurring most frequently in early childhood. In this study, we have examined the possible association of JCV with human medulloblastomas. By using PCR techniques we demonstrate that 11 of 23 samples of tumor tissue contain DNA sequences corresponding to three different regions of the JCV genome. More importantly, we demonstrate the presence of DNA sequences encoding the N- and C-terminal regions of the JCV oncogenic protein, T antigen, in 11 of 23 samples and the production oft antigen in the nuclei of 4 samples of tumor tissue. These observations provide evidence for a possible association of JCV with human medulloblastomas
Involvement of Wnt signaling Pathway in Murine medulloblastoma induced by human neurotropic JC Virus
No full textBy using the early genome of the human neurotropic polyomavirus, JCV, we have created transgenic animals that develop cerebellar primitive neuroectodermal tumors which model human medulloblastoma. Expression of T-antigen was found in some, but not all, tumor cells, and examination of the clonal cell lines derived from the tumor population showed enhanced tumorigenicity of cells expressing T-antigen in comparison to T-antigen negative cells. Considering the earlier notion on the potential involvement of β-catenin with human medulloblastoma, we investigated various components of the Wnt signaling pathway including β-catenin, its partner transcription factor, LEF-1, and their downstream target gene c-myc in these two cell populations. Immunohistochemical staining of the cells revealed enhanced nuclear appearance of β-catenin in T-antigen positive cells. Results from Western blot showed higher levels of β-catenin and LEF-1 in T-antigen positive cells in comparison to those in T-antigen negative cells. The enhanced level of LEF-1 expression correlated with the increase in DNA binding activity of this protein in nuclear extracts of T-antigen positive cells. Results from Northern and Western blot analyses revealed that the level of c-myc expression is augmented both at the RNA and protein levels in T-antigen positive cells. These observations corroborated results from transfection studies indicating the ability of JCV T-antigen to stimulate c-myc promoter activity. Further, co-transfection experiments revealed that the amount of c-myc and T-antigen protein in tumor cells may dictate the activity of JCV early promoter in these cells. These observations are interesting in light of recent discoveries on the association of JCV with human medulloblastoma and suggest that communication between JCV and the Wnt pathway may be an important event in the genesis of these tumors
IRS-1-Rad51 nuclear interaction sensitizes JCV T-antigen positive medulloblastoma cells to genotoxic treatment
No full textThe large T-antigen from human polyomavirus JC (JCV T-antigen) is suspected to play a role in malignant transformation. Previously, we reported that JCV T-antigen requires the presence of a functional insulin-like growth factor I receptor (IGF-IR) for transformation of fibroblasts and for survival of medulloblastoma cell lines; that IGF-IR is phosphorylated in medulloblastoma biopsies and that JCV T-antigen inhibits homologous recombination-directed DNA repair, causing accumulation of mutations. Here we are evaluating whether JCV T-antigen positive and negative mouse medulloblastoma cell lines, which significantly differ in their tumorigenic properties, are also different in their abilities to repair double strand breaks of DNA (DSBs). Our results show that despite much stronger tumorigenic potential, JCV T-antigen positive medulloblastoma cells are more sensitive to genotoxic agents (cisplatin and gamma-irradiation). Subsequent analysis of DNA repair of DSBs indicated that homologous recombination-directed DNA repair (HRR) was selectively attenuated in JCV T-antigen positive medulloblastoma cells. JCV T-antigen did not affect HRR directly. In the presence of JCV T-antigen, insulin receptor substrate 1 (IRS-1) translocated to the nucleus where it co-localized with Rad51, possibly attenuating HRR
Activation of the IGF-IR system contributes to malignant growth of human and mouse primitive neuroectodermal tumors/Medulloblastomas
No full textInsulin-like growth factor I receptor (IGF-IR) has been implicated in the normal and malignant growth of many cell types including cells from the central nervous system. In the cerebellar cortex IGF-IR mRNA is found in granular cells and IGF-I stimulation is mitogenic and protects cells from low-potassium-induced apoptosis. Since primitive neuroectodermal tumors/medulloblastomas (PNETs/medulloblastomas) are suspected to originate from the external cerebellar granular layer, it is reasonable to postulate that IGF-IR and/or its signaling molecules may contribute to the transformation of these poorly differentiated cells. To study activation of the IGF-IR system in medulloblastomas, we have utilized an antibody (anti-pY1316) that specifically recognizes the phosphorylated (active) form of the IGF-IR. Medulloblastoma biopsy specimens were positive when examined immunohistochemically with anti-Y1316 antibody. Further analysis of the IGF-IR system was performed in three human (Daoy, TE-671, D283 Med) and four mouse (BsB8, BsB13, Bs-1b, Bs-1c) medulloblastoma cell lines. All the murine cell lines examined express IGF-IR and PI3-kinase at relatively normal levels, and grossly overexpress IRS-1, when compared with normal mouse cerebellum. Within 15 min following IGF-I stimulation both mouse and human cell lines phosphorylate the beta subunit of the IGF-IR, IRS-1, Akt, and MAP kinases. They respond with cell proliferation when stimulated solely with IGF-I and are strongly inhibited when challenged with a dominant negative mutant of the IGF-IR (486/STOP), or with antisense oligonucleotides against the IGF-IR mRNA
Foretinib is effective therapy for metastatic sonic hedgehog medulloblastoma
No full textMedulloblastoma is the most common malignant pediatric brain tumor, with metastases present at diagnosis conferring a poor prognosis. Mechanisms of dissemination are poorly understood and metastatic lesions are genetically divergent from the matched primary tumor. Effective and less toxic therapies that target both compartments have yet to be identified. Here, we report that the analysis of several large non-overlapping cohorts of patients with medulloblastoma reveals MET kinase as a marker of sonic hedgehog (SHH)-driven medulloblastoma. Immunohistochemical analysis of phosphorylated, active MET kinase in an independent patient cohort confirmed its correlation with increased tumor relapse and poor survival, suggesting that patients with SHH medulloblastoma may benefi t fromMET-targeted therapy. In support of this hypothesis, we found that the approved MET inhibitor foretinib could suppress MET activation, decrease tumor cell proliferation, and induce apoptosis in SHH medulloblastomas in vitro and in vivo. Foretinib penetrated the blood-brain barrier and was effective in both the primary and metastatic tumor compartments. In established mouse xenograft or transgenic models of metastatic SHH medulloblastoma, foretinib administration reduced the growth of the primary tumor, decreased the incidence of metastases, and increased host survival. Taken together, our results provide a strong rationale to clinically evaluate foretinib as an effective therapy for patients with SHH-driven medulloblastoma
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