GAB2 is a novel target of 11q amplification in AML/MDS

Chromosome arm 11q amplifications involving the mixed lineage leukemia gene (MLL) locus are rare but recurrent aberrations in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). We have recently shown that in addition to the MLL core amplicon, independent sequences in 11q23-24 and/or 11q13.5 are coamplified within the same cytogenetic markers in 90% and 60% of patients, respectively. Here we further narrow down the minimal amplicon in 11q13.5 to 1.17 Mb by means of semi-quantitative PCR and FISH analyses. The newly defined amplicon contains seven genes, including the GRB2-associated binding protein 2 (GAB2). Using real-time RT-PCR we show a significant transcriptional upregulation of GAB2 in the patients who have GAB2 coamplified with MLL. Thus, the adaptor molecule GAB2 that has already been shown to enhance oncogenic signaling in other neoplasias appears as a novel target of 11q amplification in AML/MDS.