NO ABERRANT METHYLATION OF NEUROFIBROMATOSIS 1 GENE (NF1) PROMOTER IN PILOCYTIC ASTROCYTOMA IN CHILDHOOD

Tumours of the central nervous system are the most frequent solid tumours in childhood. With 30 % - 40 % of this heterogenous group, low-grade astrocytomas represent the most common subtype. Neurofibromatosis type 1 (NF1) is strongly associated with the development of pilocytic astrocytoma (PA), frequently appearing as optic glioma. Neurofibromatosis 1 gene (NF1) fulfills the criteria of a tumour suppressor gene and is deleted or mutated heterozygously in patients with NF1. This suggests an involvement in the development of PA. To clarify whether silencing of NF1 by promoter methylation plays a role in PA and especially in optic glioma, we investigated the methylation status in 30 PA, 6 of which had optic glioma. However, we found no methylation at the NF1 promoter region in PA. To rule out that silencing of NF1 by promoter methylation is restricted to higher-grade astrocytomas, we analyzed 15 pediatric WHO II° and IV° astrocytomas. 12 astrocytomas II° and 3 glioblastomas displayed no NF1 promoter methylation. We conclude that NF1 silencing by methylation plays no role in low-grade astrocytoma.