Comparative genomic hybridization pattern of non-anaplastic and anaplastic oligodendrogliomas--a meta-analysis

Many oligodendrogliomas (ODG) have been investigated by comparative genomic hybridization (CGH). To visualize characteristic aberration profiles of non-anaplastic in a comparison with anaplastic ODGs, we performed a meta-analysis of the CGH results of all 89 cases published so far. Therefore, we expanded all given aberrations to the maximum of 850 GTG band resolution. The frequencies of each chromosomal band affected by a genetic imbalance were calculated for WHO grades II and III separately. In non-anaplastic ODGs, -1p and -19q were the most prominent aberrations. In anaplastic ODGs, +7, -4q, -9p, -10, and -15q emerged additionally. We could confirm the existence of three disjunct genetically defined subgroups of ODGs, characterized by -1p/-19q (n=58, 65%, subgroup A), +7/-10 (n=6, 7%, subgroup B) or the absence of either of the two patterns (n=25, 28%, subgroup C). Interestingly, we found a unique aberration pattern in subgroup C (-1p31, -4q, -11p15, -18q, -22q, +17p, +17q) that was different from subgroups A and B, which could indicate a unique molecular carcinogenetic pathway of this ODG subset. Scrutinizing published putative progression markers of ODG, we found that only +7, -10, and -15q significantly correlated with a higher grade of malignancy. Summing up, the expansion of the CGH results to the 850 GTG band resolution enabled a meta-analysis to visualize WHO grade-specific aberration profiles in ODG for the first time.