Chromosome 21 abnormalities with AMLI amplification in acute lymphoblasticleukemia

Fluorescence in situ. hybridization (FISH) studies were performed in three cases of acute lymphoblastic leukemia (ALL), with marker chromosomes to ana lyze the contribution of chromosome 21 in these markers. FISH with a chromo some 21 painting probe confirmed that chromosome 21 was involved in all thr ee cases. FISH with YAC probes showed that the number of extra copies varie d according to their location on chromosome 21. Attention was focused on th e AML 1 gene, which was present as five copies in most of the cells exhibit ing the marker chromosomes. As controls, 11 cases of childhood ALL were stu died with PAC probes covering AML1. The results agreed with the banded kary otypes in 10 patients. FISH uncovered a clone with four copies of AML1 whic h were only observed by FISH analysis of interphase nuclei in one patient. No point mutation was detected in exons 3-5, encoding the runt domain of AM L1 in the three cases, suggesting an oncogenic role of wild-type AML1 ampli fication. (C) 2001 Wiley-Liss, Inc.