AMPLIFIED C-MYC SEQUENCES LOCALIZED BY FLUORESCENCE IN-SITU HYBRIDIZATION ON DOUBLE MINUTE CHROMOSOMES IN ACUTE MYELOID LEUKEMIAS

Double minute chromosomes (dmin) are small acentric fragments frequent ly observed when karyotyping human tumor cells. They are considered th e cytogenetic manifestation of gene amplification. The finding of dmin in leukemia is a rare event usually associated with progression of th e disease and unfavorable prognosis. We present four patients affected by myeloid disorders with an abnormal karyotype and a variable number of dmin. In an attempt to clarify the origin of the dmin and the ampl ified gene, we utilized a fluorescent in-situ hybridization (FISH) tec hnique and a panel of specific probes. The results of the analysis ind icate that, although chromosomes 8 are apparently uninvolved, dmin ret ained c-MYC sequencs in three cases. By observing previously reported cases, we found that the majority of patients with myeloid disorders a nd dmin showed an amplified c-MYC gene, regardless of the chromosomal abnormalities. The FISH technique proved to be informative in demonstr ating gene amplification in both metaphase and interphase cells. Final ly, in the one patient carrying a 20q deletion, FISH allowed the detec tion of a previously unreported translocation between a 16p and the 20 q-, confirming the ability of the technique to understand complex kary otypes. (C) 1997 Elsevier Science Ltd.