Molecular genetic studies of chromosome 11 and chromosome 22q DNA sequences in pediatric medulloblastomas

Medulloblastomas are primitive neuroectodermal tumors (PNETs) of the cerebe llum with poorly understood pathogenesis. Previous molecular studies sugges ted a role for loci on chromosome 11 in the development of medulloblastomas -PNETs. In order to identify the frequency of loss and eventually the exten t of allelic loss on chromosome 11, we have examined 23 pediatric medullobl astomas for loss of heterozygosity (LOH) with 16 polymorphic microsatellite s. Our data reveal that LOH on 11p or 11q occurs rarely (13%) suggesting th e unlikely involvement of chromosome 11 in most cases of medulloblastomas. The same frequency of LOH in medulloblastomas was detected using 8 microsat ellites on 22q. Alterations of microsatellite length were found in only 4/5 94 PCR analyses using 28 markers located on chromosomes 2, 9, 11, 18, and 2 2, demonstrating that genomic instability is uncommon in medulloblastomas.