The role of the WNT/ß-catenin pathway in central nervous system primitive neuroectodermal tumours (CNS PNETs).

BACKGROUND: Central nervous system primitive neuroectodermal tumours (CNS PNETs) are embryonal tumours occurring predominantly in children. Current lack of knowledge regarding their underlying biology hinders development of more effective treatments. We previously identified WNT/ß-catenin pathway activation in one-third of CNS PNETs, which was potentially linked to a better prognosis. In this study, we have extended our cohort, achieving a statistically significant correlation with prognosis. We additionally investigated the biological effects of WNT/ß-catenin pathway activation in tumour pathogenesis. METHODS: A total of 42 primary and 8 recurrent CNS PNETs were analysed for WNT/ß-catenin pathway status using ß-catenin immunohistochemistry. Genomic copy number and mRNA expression data were analysed to identify a molecular profile linked to WNT/ß-catenin pathway activation. RESULTS: Pathway activation was seen in 26% of CNS PNETs and was significantly associated with longer overall survival. Genes displaying a significant difference in expression levels, between tumours with and without WNT/ß-catenin pathway activation, included several involved in normal CNS development suggesting aberrant pathway activation may be disrupting this process. CONCLUSION: We have identified WNT/ß-catenin pathway status as a marker, which could potentially be used to stratify disease risk for patients with CNS PNET. Gene expression data suggest pathway activation is disrupting normal differentiation in the CNS.

WNT/ß-catenin pathway activation in Myc immortalised cerebellar progenitor cells inhibits neuronal differentiation and generates tumours resembling medulloblastoma.

BACKGROUND: Medulloblastoma is the most common malignant childhood brain tumour. Aberrant activation of the WNT/ß-catenin pathway occurs in approximately 25% of medulloblastomas. However, its role in medulloblastoma pathogenesis is not understood. METHODS: We have developed a model of WNT/ß-catenin pathway-activated medulloblastoma. Pathway activation was induced in a Myc immortalised cerebellar progenitor cell line through stable expression of Wnt1. In vitro and in vivo analysis was undertaken to understand the effect of pathway activation and identify the potential cell of origin. RESULTS: Tumours that histologically resembled classical medulloblastoma formed in vivo using cells overexpressing Wnt1, but not with the control cell line. Wnt1 overexpression inhibited neuronal differentiation in vitro, suggesting WNT/ß-catenin pathway activation prevents cells terminally differentiating, maintaining them in a more 'stem-like' state. Analysis of cerebellar progenitor cell markers demonstrated the cell line resembled cells from the cerebellar ventricular zone. CONCLUSION: We have developed a cell line with the means of orthotopically modelling WNT/ß-catenin pathway-activated medulloblastoma. We provide evidence of the role pathway activation is playing in tumour pathogenesis and suggest medulloblastomas can arise from cells other than granule cell progenitors. This cell line is a valuable resource to further understand the role of pathway activation in tumorigenesis and for investigation of targeted therapies.

Patient experience of hypoglycaemia unawareness in Type 1 diabetes: are patients appropriately concerned?

OBJECTIVE: Risk of severe hypoglycaemia is increased by absence of subjective awareness of hypoglycaemia and reduced by avoidance of minor hypoglycaemia. For many, problems persist despite educational strategies that work for others. We explored psychological factors that might inhibit the efforts of an individual in hypoglycaemia avoidance. METHODS: People with Type 1 diabetes and hypoglycaemia unawareness gave semi-structured interviews exploring their perceptions and experiences of their condition. Identified factors were grouped into categories and analysed to establish links and form a grounded theory in a constant comparative analysis. A questionnaire was devised from the qualitative analysis to identify patients with problematic beliefs about their hypoglycaemia. RESULTS: Saturation (no new themes emerging) was reached with 17 patients. Responses fell into two groups: high concern and low concern regarding hypoglycaemia unawareness. Those in the first group described severe hypoglycaemia as aversive and wanted to regain awareness. The second group included three patients in whom unawareness was not associated with severe hypoglycaemia, nevertheless unhelpful attitudes which inhibited hypoglycaemia avoidance were expressed. Responses from this group fell into categories: (1) normalizing the presence of unawareness; (2) underestimating its consequences; (3) wanting to avoiding the 'sick role'; and (4) overestimating the consequences of hyperglycaemia. CONCLUSIONS: A qualitative analysis of patient interviews identified deficits in education, technology and motivation in hypoglycaemia unawareness. Interventions can therefore be tailored to target underlying problems that prevent individual patients from regaining awareness. A brief assessment tool was devised to categorize patients' hypoglycaemia unawareness accordingly. Psychological interventions should be developed to address the problems of 'low concern' regarding hypoglycaemia unawareness.

An investigation of WNT pathway activation and association with survival in central nervous system primitive neuroectodermal tumours (CNS PNET).

Central nervous system primitive neuroectodermal tumours (CNS PNET) are high-grade, predominantly paediatric, brain tumours. Previously they have been grouped with medulloblastomas owing to their histological similarities. The WNT/beta-catenin pathway has been implicated in many tumour types, including medulloblastoma. On pathway activation beta-catenin (CTNNB1) translocates to the nucleus, where it induces transcription of target genes. It is commonly upregulated in tumours by mutations in the key pathway components APC and CTNNB1. WNT/beta-catenin pathway status was investigated by immunohistochemical analysis of CTNNB1 and the pathway target cyclin D1 (CCND1) in 49 CNS PNETs and 46 medulloblastomas. The mutational status of APC and CTNNB1 (beta-catenin) was investigated in 33 CNS PNETs and 22 medulloblastomas. CTNNB1 nuclear localisation was seen in 36% of CNS PNETs and 27% of medulloblastomas. A significant correlation was found between CTNNB1 nuclear localisation and CCND1 levels. Mutations in CTNNB1 were identified in 4% of CNS PNETs and 20% of medulloblastomas. No mutations were identified in APC. A potential link between the level of nuclear staining and a better prognosis was identified in the CNS PNETs, suggesting that the extent of pathway activation is linked to outcome. The results suggest that the WNT/beta-catenin pathway plays an important role in the pathogenesis of CNS PNETs. However, activation is not caused by mutations in CTNNB1 or APC in the majority of CNS PNET cases.