Molecular genetic aspects of oligodendrogliomas including analysis by comparative genomic hybridization

Oligodendroglial neoplasms are a subgroup of gliomas with distinctive morph ological characteristics. In the present study we have evaluated a series o f these tumors to define their molecular profiles and to determine whether there is a relationship between molecular genetic parameters and histologic al pattern in this tumor type. Loss of heterozygosity (LOH) for 1p and 19q was seen in 17/23 (74%) well-differentiated oligodendrogliomas, in. 18/23 ( 83%) anaplastic oligodendrogliomas, and in 3/8 (38%) oligoastrocytomas grad es II and III. LOH for 17p and/or mutations of the TP53 gene occurred in 14 of these 55 tumors. Only one of the 14 cases with 17p LOH/TP53 gene mutati on also had LOH for Ip and 19q, and significant astrocytic elements mere se en histologically in the majority of these 14 tumors. LOH for 9p and/or del etion of the CDKN2A gene occurred in 15 of these 55 tumors, and 11 of these cases were among the 24 (42%) anaplastic oligodendrogliomas. Comparative g enomic hybridization (CGH) identified the majority of cases with Ip and 19q loss and, in addition, showed frequent loss of chromosomes ri, 14, 15, and 18. These findings demonstrate that oligodendroglial neoplasms usually hav e loss of Ip and 19q whereas astrocytomas of the progressive type frequentl y contain mutations of the TP53 gene, and that 9p loss and CDKN2A deletions are associated with progression from well-differentiated to anaplastic oli godendrogliomas.