Amplified, lost, and fused genes in 11q23–25 amplicon in acute myeloid leukemia, an array‐CGH study

Abstract

Gene amplifications occur rarely in hematologic neoplasms. We characterized two cases of acute myeloid leukemia (AML) with marker chromosomes and 11q23-25 amplicons. Case 1 was a 14-year-old male with an additional ring of chromosome 11 material as the sole karyotypic abnormality, as determined by G-banding and multicolor fluorescence in situ hybridization. Standard comparative genomic hybridization (CGH) showed amplification in 11q23-qter. However, the MLL gene, in 11q23, was not amplified by FISH. Case 2 was a 38-year-old male with the G-banding karyotype 51,XY,+8,+19,+3mar and with 11q22-qter amplification by standard CGH. This patient also had the MLL-LARG fusion gene. We used microarray-based CGH (array-CGH) to characterize the amplicons. In case 1, the amplified region in 11q24.3-25 (5.5 Mb) was continuous, and MLL was not amplified, as expected. In case 2, the amplicon was divided into two distinct parts, in 11q23.3 (1.2 Mb) and in 11q23.3-25 (13.3 Mb). It contained a loss ( approximately 1 Mb) in 11q23.3, and the amplicon breakpoint was in the middle of MLL. Although the amplicon size varied, the patients had a common amplified region in 11q24-25 that comprised 14 genes. Expression microarray of case 1 revealed that three of these genes, FLI1, NFRKB, and SNX19, were also overexpressed. The results indicate that the 11q24-q25 region may harbor new candidate oncogenes. In addition, the complex amplicon of case 2 suggests some intriguing chromosomal mechanisms.