DETECTION OF CHROMOSOME OVERREPRESENTATION AND UNDERREPRESENTATION INHYPERDIPLOID ACUTE LYMPHOBLASTIC-LEUKEMIA BY COMPARATIVE GENOMIC HYBRIDIZATION

Chromosomal analysis of acute lymphoblastic leukemia (ALL) is often di fficult because of the suboptimal in vitro growth of the immature lymp h old cell and the poor morphology obtained. In this study, we describ e the application of comparative genomic hybridization (CGH) to invest igate the genomic abnormalities in 14 patients with ALL, all of whom h ad cytogenetically identified numerical aberrations or gross chromosom al structural alteration. With the use of CGH, regional or whole chrom osome overrepresentation or both were found to be more frequent than u nderrepresentation (52 gains vs. 6 losses), the most common gains bein g chromosomes 21 and X. The results of the comparison between CGH and conventional R-banding analysis could be classified into three categor ies: (1) in three cases, including two with trisomy, CGH and banding a nalysis gave identical results; (2) in six cases with hyperdiploidy an d two cases presenting chromosome structural abnormalities, the result s were consistent but with minor discrepencies; (3) in three cases, in cluding two with triploidy and tetraploidy and one with chimeric karyo type together with +22, the data from CGH and cytogenetical analysis w ere discrepant. CGH could not find the triploidy and tetraploidy. Our results suggest that CGH has certain value in the detection of gains o r losses of chromosome materials in hyperdiploid ALL. Nevertheless, th e combination of CGH and conventional karyotyping provides more precis e information on the genomic imbalance in ALL. (C) Elsevier Science In c., 1998.