DOUBLE TARGET IN-SITU HYBRIDIZATION APPLIED TO THE STUDY OF NUMERICALABERRATIONS IN CHILDHOOD ACUTE LYMPHOBLASTIC-LEUKEMIA

To test the feasibility of using fluorescent in situ hybridization (FI SH) on interphase and metaphase cells to detect numerical aberrations in childhood acute lymphoblastic leukemia (ALL), we analyzed bone marr ow of 15 patients with cytogenetically documented hyperdiploidy with m ore than 50 chromosomes at diagnosis. Patients were selected on the ba sis of being trisomic or tetrasomic for chromosomes 17 and/or 18 as de termined by G-banded chromosome analysis. We performed a double target FISH using DNA probes specific for the centromeric region of chromoso mes 17 and 18, respectively The numerical changes regarding chromosome 17 and/or 18 identified by FISH on metaphases were found in all cases analyzed by FISH on interphase nuclei. In 8 of 15 patients, FISH on i nterphase nuclei demonstrated the presence of one or more groups of ce lls with different combinations of trisomy and tetrasomy of the two ch romosomes investigated, beside the ones detected on metaphases. Overal l our findings indicate that interphase FISH analysis could be a usefu l method to detect the presence of numerical aberrations of two chromo somes simultaneously in bone marrow and peripheral blood specimens of ALL as an adjunct to conventional cytogenetic investigation or metapha se FISH.