Cellular prion protein (PrPC) in the development of Merlin-deficient tumours.

Loss of function mutations in the neurofibromatosis Type 2 (NF2) gene, coding for a tumour suppressor, Merlin, cause multiple tumours of the nervous system such as schwannomas, meningiomas and ependymomas. These tumours may occur sporadically or as part of the hereditary condition neurofibromatosis Type 2 (NF2). Current treatment is confined to (radio) surgery and no targeted drug therapies exist. NF2 mutations and/or Merlin inactivation are also seen in other cancers including some mesothelioma, breast cancer, colorectal carcinoma, melanoma and glioblastoma. To study the relationship between Merlin deficiency and tumourigenesis, we have developed an in vitro model comprising human primary schwannoma cells, the most common Merlin-deficient tumour and the hallmark for NF2. Using this model, we show increased expression of cellular prion protein (PrPC) in schwannoma cells and tissues. In addition, a strong overexpression of PrPC is observed in human Merlin-deficient mesothelioma cell line TRA and in human Merlin-deficient meningiomas. PrPC contributes to increased proliferation, cell-matrix adhesion and survival in schwannoma cells acting via 37/67 kDa non-integrin laminin receptor (LR/37/67 kDa) and downstream ERK1/2, PI3K/AKT and FAK signalling pathways. PrPC protein is also strongly released from schwannoma cells via exosomes and as a free peptide suggesting that it may act in an autocrine and/or paracrine manner. We suggest that PrPC and its interactor, LR/37/67 kDa, could be potential therapeutic targets for schwannomas and other Merlin-deficient tumours.

Changing molecular profile of brain metastases compared with matched breast primary cancers and impact on clinical outcomes.

BACKGROUND: Breast cancer commonly metastasises to the brain, but little is known about changes in the molecular profile of the brain secondaries and impact on clinical outcomes. METHODS: Patients with samples from brain metastases and matched breast cancers were included. Immunohistochemical analysis for oestrogen receptor, progesterone receptor, p27kip1, cyclin D1, epidermal growth factor receptor, insulin like growth factor 1, insulin like growth factor 1 receptor, vascular endothelial growth factor A, transforming growth factor-ß and HER2 receptor was performed. Borderline HER2 results were analysed by fluorescent in situ hybridisation. Levels of expression were compared, with review of effect on clinical outcomes. RESULTS: A total of 41 patients were included. Of the patients, 20% had a change in oestrogen receptor or HER2 in their brain metastasis that could affect therapeutic decisions. There were statistically significant rises in brain metastases for p27kip1 (P=0.023) and cyclin D1 (P=0.030) and a fall in vascular endothelial growth factor A (P=0.012). Overall survival from the time of metastasis increased significantly with oestrogen receptor-positive (P=0.005) and progesterone receptor-positive (P=0.013) brain lesions and with a longer duration from diagnosis of the breast primary (P<0.001). CONCLUSIONS: In this cohort there were phenotypic differences in metastatic brain tumours compared with matched primary breast tumours. These could be relevant for aetiology, and have an impact on prognostication, current and future therapies.

A tale of the unexpected: Amyloidoma associated with intracerebral lymphoplasmacytic lymphoma.

Amyloidoma is a rare cause for intracranial space-occupying lesions diagnosed on brain imaging. Histology of excised tissue usually reveals the presence of a discrete, λ-light chain secreting plasmacytoma adjacent to an amyloid mass comprising aggregated monoclonal immunoglobulin light chains. We described a patient with intracerebral amyloidoma associated with a localised lymphoplasmacytic lymphoma and no systemic paraproteinaemia, tumour or amyloid deposits.

Axl/Gas6/NFκB signalling in schwannoma pathological proliferation, adhesion and survival.

TAM family receptor tyrosine kinases comprising Tyro3 (Sky), Axl, and Mer are overexpressed in some cancers, correlate with multidrug resistance and contribute to tumourigenesis by regulating invasion, angiogenesis, cell survival and tumour growth. Mutations in the gene coding for a tumour suppressor merlin cause development of multiple tumours of the nervous system such as schwannomas, meningiomas and ependymomas occurring spontaneously or as part of a hereditary disease neurofibromatosis type 2. The benign character of merlin-deficient tumours makes them less responsive to chemotherapy. We previously showed that, amongst other growth factor receptors, TAM family receptors (Tyro3, Axl and Mer) are significantly overexpressed in schwannoma tissues. As Axl is negatively regulated by merlin and positively regulated by E3 ubiquitin ligase CRL4DCAF1, previously shown to be a key regulator in schwannoma growth we hypothesized that Axl is a good target to study in merlin-deficient tumours. Moreover, Axl positively regulates the oncogene Yes-associated protein, which is known to be under merlin regulation in schwannoma and is involved in increased proliferation of merlin-deficient meningioma and mesothelioma. Here, we demonstrated strong overexpression and activation of Axl receptor as well as its ligand Gas6 in human schwannoma primary cells compared to normal Schwann cells. We show that Gas6 is mitogenic and increases schwannoma cell-matrix adhesion and survival acting via Axl in schwannoma cells. Stimulation of the Gas6/Axl signalling pathway recruits Src, focal adhesion kinase (FAK) and NFκB. We showed that NFκB mediates Gas6/Axl-mediated overexpression of survivin, cyclin D1 and FAK, leading to enhanced survival, cell-matrix adhesion and proliferation of schwannoma. We conclude that Axl/FAK/Src/NFκB pathway is relevant in merlin-deficient tumours and is a potential therapeutic target for schwannoma and other merlin-deficient tumours.

Insulin-like growth factor-binding protein-1 (IGFBP-1) regulates human schwannoma proliferation, adhesion and survival.

Merlin is a tumour suppressor involved in the development of a variety of tumours including mesotheliomas. Neurofibromatosis type 2 (NF2), a dominantly inherited tumour disease, is also caused by loss of merlin. NF2 patients suffer from multiple genetically well-defined tumours, schwannomas are most frequent among those. Using our in vitro model for human schwannoma, we found that schwannoma cells display enhanced proliferation because of the overexpression/activation of platelet-derived growth factor receptor and ErbB2/3, increased cell-matrix adhesion because of the overexpression of integrins, and decreased apoptosis. Mechanisms underlying schwannomas basal proliferation and cell-matrix adhesion are not understood. Here, we investigated insulin-like growth factor-binding protein-1 (IGFBP-1), which is expressed and released from central nervous system tumours and strongly overexpressed in schwannoma at the mRNA level. IGFBP-1 acts via ß1-integrin and focal-adhesion-kinase (FAK), which are strongly overexpressed and basally activated in schwannoma. Using short hairpin RNA knockdown, small inhibitors and recombinant IGFBP-1, we demonstrate that schwannoma cells, in contrast to Schwann cells, release IGFBP-1 that activates the Src/FAK pathway, via integrin ß1, potentiating schwannoma's proliferation and cell-matrix adhesion. We show that FAK localizes to the nucleus and Src triggers IGFBP-1 production. Further, we observed downregulation of the tumour-suppressor phosphatase and tensin homolog in schwannoma cells leading to increased activity of anti-apoptotic AKT. Thus, IGFBP-1/integrin ß1/Src/FAK pathway has a crucial role in merlin-related tumourigenesis and therefore represents an important therapeutic target in the treatment of merlin-deficient tumours.

Causality in acute encephalitis: defining aetiologies.

Defining the causal relationship between a microbe and encephalitis is complex. Over 100 different infectious agents may cause encephalitis, often as one of the rarer manifestations of infection. The gold-standard techniques to detect causative infectious agents in encephalitis in life depend on the study of brain biopsy material; however, in most cases this is not possible. We present the UK perspective on aetiological case definitions for acute encephalitis and extend them to include immune-mediated causes. Expert opinion was primarily used and was supplemented by literature-based methods. Wide usage of these definitions will facilitate comparison between studies and result in a better understanding of the causes of this devastating condition. They provide a framework for regular review and updating as the knowledge base increases both clinically and through improvements in diagnostic methods. The importance of new and emerging pathogens as causes of encephalitis can be assessed against the principles laid out here.

A meningeal myofibroblastic neoplasm related to solitary fibrous tumour and associated with a malignant neuroblastic element.

BACKGROUND: Solitary fibrous tumour (SFT) is a rare mesenchymal tumour now described at many locations, including the meninges. Intracranial SFT closely resembles meningioma clinically and radiologically, and, like meningioma, reports of meningeal SFT suggest a relatively benign behaviour after complete resection. Histopathological features distinguishing SFT from meningioma include variable cellularity, spindle cells arranged in fascicles, staghorn blood vessels and immunopositivity for CD34. CLINICAL PRESENTATION: The case is reported of a 60-year-old man with an anterior cranial fossa meningeal-based mass, which was resected. Histology showed some features in common with SFT (variable cellularity, spindled morphology, CD34 expression), but included an epithelioid element with cytokeratin and desmin immunopositivity, and lacked the characteristic vascular pattern of SFT. Histological features of meningioma were lacking. Recurrence of the tumour with extracranial extension 9 years later resulted in death of the patient. Histological examination revealed similar biphasic epithelioid and spindled CD34-immunopositive appearance to the earlier tumour, but in addition showed a high-grade element resembling olfactory neuroblastoma. CONCLUSION: This case report is of a meningeal-based mesenchymal neoplasm with histological similarities to SFT. Its morphology and immunophenotype, however, are distinct from SFT and hence it is proposed that it is a newly described entity. In addition, recurrence of the tumour with a high-grade neuroblastic element has, to our knowledge, not previously been described in SFT.

Histological indicators of prognosis in glioblastomas: retinoblastoma protein expression and oligodendroglial differentiation indicate improved survival.

AIM: To assess the potential prognostic significance of a range of molecular and morphological parameters in glioblastomas that can be applied in the setting of a routine diagnostic neuropathology laboratory. METHODS AND RESULTS: A consecutive series of 107 adult glioblastomas were studied. Retinoblastoma and deleted-in-colon cancer (DCC) protein expression were assessed using immunocytochemistry and chromosome 10 loss by in-situ hybridization. Loss of retinoblastoma expression was associated with a worse outcome, which appeared to be independent of age. There was no significant association between chromosome 10 loss or DCC protein expression and survival. Survival was significantly increased in the 5% of patients whose tumours had focal morphological features suggesting oligodendroglial differentiation. CONCLUSIONS: Glioblastomas containing areas of oligodendroglial differentiation or showing widespread immunocytochemical expression of retinoblastoma protein have a better prognosis than those without these features.

Specificity of lymphoreticular accumulation of prion protein for variant Creutzfeldt-Jakob disease.

BACKGROUND: Immunocytochemical accumulation of prion protein (PrP) in lymphoid tissues is a feature of variant Creutzfeldt-Jakob disease (vCJD) that has been used both to aid in the diagnosis of patients and as a basis of large scale screening studies to assess the prevalence of preclinical disease in the UK. However, the specificity of this approach is unknown. AIM: To assess the specificity of lymphoreticular accumulation of PrP for vCJD by examining a range of human diseases. METHODS: Paraffin wax embedded lymphoreticular tissues from patients with several reactive conditions (58 cases), tumours (27 cases), vCJD (54 cases), and other human prion diseases (56 cases) were assessed. PrP accumulation was assessed by immunocytochemistry using two different monoclonal anti-PrP antibodies and a sensitive detection system. RESULTS: All cases of vCJD showed widespread lymphoreticular accumulation of PrP; however, this was not seen in the other conditions examined. CONCLUSION: Lymphoreticular accumulation of PrP, as assessed by immunocytochemistry, appears to be a highly specific feature of vCJD.

Metastatic adenocarcinoma masquerading as a solitary nerve sheath tumour.

We present a case of a solitary metastasis of an adenocarcinoma to a dorsal root ganglion (DRG) following a disease free interval of 12 years after resection of a Duke's C carcinoma. The presentation of this unusually placed metastasis was associated with a 3-year complex pain syndrome and radiological appearances consistent with benign disease. The case highlights the importance of not dismissing unusual lesions as innocent in the presence of a history of malignant disease.

An analysis of clinical characteristics in genetically linked migraine-affected pedigrees.

Migraine is a common complex disorder characterized by severe recurrent headache and usually accompanied by nausea and vomiting. Previous studies in our laboratory have utilized three large multigenerational Australian pedigrees affected with migraine to indicate that the disease is genetically heterogeneous, with linkage results implicating genomic susceptibility regions on both chromosomes 19p and Xq. The present study explores the possibility of a correlation between genetic and clinical heterogeneity in these affected pedigrees. Specifically, the clinical characteristics of migraine including subtype, age of onset, frequency, duration, and disease symptoms were compared between the migraine pedigrees, and gender differences were also assessed. Our exploratory analyses revealed no significant differences in any of the clinical characteristics tested between the chromosome 19-linked family and the two X-linked families. Also, we did not detect any differences in male vs. female clinical features for these pedigrees. In conclusion, migraine is considered to be a clinically and genetically heterogeneous disorder; however, our study provided no conclusive evidence that variation in genomic susceptibility region is related to heterogeneity at the clinical level in these migraine-affected pedigrees.

The clinicopathological spectrum of Rosenthal fibre encephalopathy and Alexander's disease: a case report and review of the literature.

Alexander's disease is a leucodystrophy that usually presents in early childhood, but can infrequently arise in adults. It is characterised pathologically by megalencephaly, demyelination, and the presence of numerous Rosenthal fibres. Most cases have been shown to be due to mutations in the gene encoding glial fibrillary acidic protein. In rare instances, numerous Rosenthal fibres have been found at autopsy in patients who have suffered protracted debilitating systemic illnesses, some with associated brain stem signs, and in very rare instances in patients with no apparent neurological abnormality. The term "Rosenthal fibre encephalopathy" is used to distinguish these cases from those of Alexander's disease. We report the first case of Rosenthal fibre encephalopathy in a young man with AIDS, and review the literature.

Expression of hypoxia-inducible factor 1alpha in tumours of patients with glioblastoma.

Angiogenesis is a prominent feature of glioblastomas but the mechanisms involved in the control of this process are poorly understood. We have investigated the potential role of a recently described transcription factor, hypoxia-inducible factor 1 (HIF-1), which initiates the transcription of a number of hypoxia-inducible genes, including those encoding vascular endothelial growth factor and its receptors. HIF-1 protein expression was assessed by immunocytochemistry, using a monoclonal antibody to the alpha subunit (HIF-1alpha). HIF-1 mRNA expression was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR) and the ribonuclease protection assay (RPA). Strong nuclear expression of HIF-1alpha protein was seen in the majority of glioblastomas and anaplastic astrocytomas, particularly surrounding areas of necrosis in glioblastomas. In the majority of these tumours upregulation of HIF-1alpha mRNA was also demonstrated, with a significant increase in glioblastomas compared to lower grade tumours. No correlation was found between the presence of HIF-1alpha protein and immunohistochemical expression of p53 protein. These findings are in keeping with an important role of HIF-1alpha in the vascularization of glioblastomas and suggest that upregulation is at least partly at a transcriptional level.