Identification of a potential "Hotspot" DNA region in the RUNXI gene targeted by mitoxantrone in therapy-related acute myeloid leukemia with t(16;21) translocation

The translocation t(16;21) involving RUNXI (AMLI) and resulting in the RUNXI-CBFA2T3 fusion is a rare but recurrent abnormality mostly found in therapy-related acute myeloid leukemia (t-AML) associated with agents targeting topoisomerase II (topo II). We characterized, at the genomic level, the t(16;21) translocation in a patient who developed t-AML after treatment of multiple sclerosis with mitoxantrone (MTZ). Long template nested PCR of genomic DNA followed by direct sequencing enabled the localization of RUNXI and CBFA2T3 (ETO2) breakpoints in introns 5 and 3, respectively. Sequencing of the cDNA with specific primers showed the presence of the expected RUNXI-CBFA2T3 fusion transcript in leukemic cells. The RUNXI intron 5 breakpoint was located at nucleotide position 24,785. This region contained an ATGCCCCAG nucleotide sequence showing similar to 90% homology to a "hotspot" DNA region ATGCCCTAG present in intron 6 of PML previously identified in therapy-related acute promyelocytic leukemia cases arising following treatment with MTZ. This study suggests a wider distribution in the human genome, and particularly at genes involved in chromosome translocations observed in t-AML, of DNA regions (hotspot) targeted by specific topo II drugs. (c) 2008 Wiley-Liss, Inc.