Simple variant t(8;21) acute myeloid leukemias harbor insertions of the AMLI or ETO genes

We report on the molecular characterization of two acute myeloid leukemias (AML), one AML-M I (patient I) and one AML-M2 (patient 2) with t(8;21)(p21; q22) and t(8;20)(q22;p13), respectively, at diagnosis. The locations of the breakpoints, 21q22 in patient I and 8q22 in patient 2, prompted us to sear ch for a cryptic t(8;2 I)(q22;q22) and involvement of the AML I and ETO gen es. Dual-color fluorescence in situ hybridization (FISH) using whole chromo some painting probes for chromosomes 8, 20, and 21 confirmed the convention al cytogenetic karyotypes. However, dual-color FISH using appropriate ETO a nd AML I probes disclosed an insertion of AMLI into 8q22 on the derivative chromosome 8 in patient 1 and of ETO into 21q22 on one chromosome 21 in pat ient 2, leading to AMLI-ETO fusion signals. Both cases expressed an AMLI-ET O transcript, shown by reverse transcriptase polymerase chain reaction and cDNA sequencing. Creation of functional AMLI-ETO fusion genes in these two simple variant t(8;21) probably occurred through complex mechanisms, combin ing translocation and insertion of chromosomal segments. (C) 1999 Wiley-Lis s, Inc.