MOLECULAR CYTOGENETIC STUDIES OF PEDIATRIC EPENDYMOMAS

Cytogenetic and molecular studies of ependymomas have previously demon strated deletions of chromosomes 17 and 22 as frequent abnormalities, implicating inactivation of tumor suppressor genes in the pathogenesis of these tumors. In the present study, we analyzed 22 childhood epend ymomas by standard cytogenetic analysis, fluorescence in situ hybridiz ation (FISH) and polymerase chain reaction (PCR)-based microsatellite analysis of chromosomes 17 and 22. Microsatellite analysis of chromoso me 6 was performed to identify submicroscopic deletions implicated by the cytogenetic studies. Among the 22 cases, we demonstrated loss of c hromosome 22 in 2 patients, deletion of chromosome 17 in 2 patients, a nd rearrangements or deletions of chromosome 6 in 5 patients. These da ta do not suggest that loss of a gene on chromosome 17p plays a primar y role in the initiation of pediatric ependymomas. This is in contrast to what has been reported for pediatric CNS primitive neuroectodermal tumors and malignant astrocytomas, in which deletion of 17p is regard ed as a primary event. Furthermore, loss of chromosome 22 may define a subset of ependymomas more commonly seen in adults. Cytogenetic studi es in this series, however, suggest that a region on the long arm of c hromosome may be involved in the development and/or progression of epe ndymomas in children.