Evidence of focal genetic microheterogeneity in glioblastoma multiforme byarea-specific CGH on microdissected tumor cells

The term "multiforme" in glioblastoma multiforme (GBM) indicates the highly variable histomorphology that cannot be addressed by studies on homogenize d tissue probes. In order to relate genetic findings with histomorphologica lly distinct areas we used microdissection to procure defined cell populati ons from microscopic tissue sections under direct visualization. Formalin-f ixed and paraffin-embedded tissue sections of 10 GBM were evaluated for int ratumoral genetic heterogeneity by microdissection of multiple areas of 20- 50 tumor cells and DOP-PCR of DNA isolated from the dissected cell groups, followed by comparative genomic hybridization (CGH). Microdissected cells f rom histomorphologically normal extratumoral blood vessels from the same sl ides served as controls. The individual tumors showed variable combinations of primary chromosomal gains and losses common to all studied areas of a g iven case along with secondary, area-specific additional aberrations. CGH d isplayed a wider variety of chromosomal aberrations than metaphase cytogene tics of cell cultures from the same tumors. The most frequent aberrations o bserved were previously unperceived gains on chromosomes 4q (8/10) and 5q ( 5/10). Other nonrandom aberrations were gains on 12q (6/10), 13q (6/10), an d 7 (5/10), and losses of 22 (5/10). Amplifications on 7p were intratumoral ly heterogeneous and only found in single areas of 2 tumors. In contrast to normal extratumoral vessels, vascular proliferates in most cases demonstra ted chromosomal aberrations (CGH) which were partially different from the a berrations observed in the tumor itself. The described method gives evidenc e of considerable intratumoral genetic heterogeneity in GBM and provides a sensitive tool for the detection of quantitative chromosomal changes that a re present only regionally within a given tumor.