COMPARATIVE GENOMIC HYBRIDIZATION IN CHILDHOOD ACUTE LYMPHOBLASTIC-LEUKEMIA

DNA copy number changes were studied by comparative genomic hybridizat ion (CGH) on bone marrow samples obtained from 72 patients with childh ood acute lymphoblastic leukemia (ALL) at diagnosis. The patients had been admitted to the Helsinki University Central Hospital (Finland) be tween 1982 and 1997. CGH showed DNA copy number changes in 45 patients (62.5%) with a mean of 4.6 aberrations per patient (range, 1 to 22). The results of CGH and chromosome banding analysis were generally conc ordant, but CGH facilitated specific karyotyping in 34 cases. DNA copy number gains were more frequent than losses (gains:losses, 6:1). Gain s of DNA sequences affected almost exclusively whole chromosomes and w ere most commonly observed in chromosomes 21 (25%), 18 (22.2%), X (19. 4%), 10 (19.4%) and 17 (19.4%). The most common partial gain was 1q31- q32 (8.3%). The most common gains of chromosomes 21, 18, X, 10, 17, 14 , 4, 6 and 8 appeared concurrently. High-level amplifications of small chromosome regions were sporadic, detected only in two patients (2.8% ). Chromosome 21 was involved in both cases. The most common losses we re 9p22-pter (12.5%) and 12p13-pter (11.1%). No statistically signific ant association between the CGH findings and the diagnostic white bloo d cell count was observed.