CHROMOSOMAL BREAKPOINTS AND CHANGES IN DNA COPY NUMBER IN REFRACTORY ACUTE MYELOID-LEUKEMIA

Comparative genomic hybridization (CGH) was used to detect changes in DNA copy number in 25 cases of refractory acute myeloid leukemia (AML) . CGH detected changes in DNA copy number in nine AML (36%). Losses (8 2%) were more frequent than gains (18%). No high-level amplifications were detected in any of the cases. Losses involved minimal overlapping regions at 5q14q32, 7q31.2q32 and 12p12. The most frequent gain was d etected at 8q. CGH gave normal results in all cases with a normal kary otype or a translocation as the sole aberration. The absence of high-l evel DNA copy gains suggests that, in contrast to other malignancies, gene amplification is not an important mechanism for drug resistance i n AML. In addition to 5q and 7q, known to be associated with disease r efractoriness, 12p may be another region related to poor prognosis.