GENETIC ABERRATIONS IN PEDIATRIC ACUTE LYMPHOBLASTIC-LEUKEMIA BY COMPARATIVE GENOMIC HYBRIDIZATION

Classical cytogenetic analysis plays an important role in the diagnosi s and classification of childhood acute lymphoblastic leukemia (ALL). However, poor in vitro growth of the malignant cells and suboptimal qu ality of metaphase spreads may sometimes cause false-negative findings (normal karyotype). We used comparative genomic hybridization (CGH) t o study whether this new method is able to detect and characterize gen etic aberrations not detected by karyotyping. CGH showed clonal geneti c aberrations in 8 of 13 cases, most of which showed gains of several chromosomes, indicating hyperdiploidy. The sensitivity of CGH was suff icient to detect a small interstitial deletion of 6q. One karyotypical ly complex case was resolved by CGH showing a high-level amplification of DNA sequences originating from the 12p12-13. Interphase fluorescen ce in situ hybridization (FISH) analyses confirmed the CGH findings in 2 cases, validating the accuracy of CCH. In conclusion, CGH experimen ts established the known fact that hyperdiploidy is the most common fi nding in pediatric ALLs and that CGH may detect aberrations that are n ot seen in the G-banded karyotype. CGH was also able to further charac terize genetic aberrations, such as gene amplification, which is occas ionally involved in pediatric ALL as well as in other leukemias. (C) E lsevier Science Inc., 1997.