Transposition of duplicated chromosomal segment involving fused BCR-ABL gene or ABL oncogene alone in chronic myelocytic leukemia and Ph chromosome-positive acute leukemia with complex karyotypes

Thirty-six patients with chronic myelocytic leukemia (CML) in the blastic p hase were examined by fluorescence in situ hybridization to clarify the mec hanisms of progression of the disease. Two of 19 CML patients in the blasti c phase (10.5%) had an extra fused BCR-ABL gene on structurally complex chr omosome aberrations in addition to the Ph chromosome. Another patient had a n extra ABL oncogene on the end of a deleted chromosome, resulting in three copies of the ABL oncogene. These three patients show ed additional chromo some aberrations, such as der(12), der(15), and der(18), which differ from the standard karyotypic evolution in the blastic phase. Amplification of th e fused BCR-ABL gene or the ABL oncogene seemed to be induced by transposit ion. These segmental transpositions suggest that these regions have high ge netic instability possibly leading to blastic transformation. (C) 2000 Else vier Science Inc. All rights reserved.