Loss of neurofibromatosis 1 (NF1) gene expression in NF1-associated pilocytic astrocytomas

The critical role of the neurofibromatosis 1 (NF1) gene as a tumour suppres sor has been clearly demonstrated for malignancies arising in NF1 patients. However, little is known about the more common benign tumours, such as the pilocytic astrocytoma. Most NF1-associated astrocytomas are benign and cli nically non-progressive, though aggressive tumours are occasionally encount ered. In this study, eight pilocytic astrocytomas from six individuals affe cted with NF1 were analysed for NF1 expression. All eight tumours demonstra ted loss of neurofibromin expression by immunohistochemistry, which was con firmed in one case using Western blot analysis. Microsatellite analysis sho wed loss of a single NF1 allele (LOH) in two of four NF1-associated tumours . These results demonstrate that, in contrast to sporadic astrocytomas, los s of NF1 expression is an important primary genetic event in the pathogenes is of NF1-associated pilocytic astrocytomas.