As acute nonlymphocytic leukemia (ANLL) with inv(16) (p13q22) or t(16;16)(p13;q22) has been shown to result from the fusion of transcription factor subunit core binding factor (CBFB) to a myosin heavy chain (MYH11), we sought to design methods to detect this rearrangement using reverse transcriptase-polymerase chain reaction (RT- PCR). In all of 27 inv(16)(p13q22) and four t(16;16)(p13;q22) cases tested, a chimeric CBFB-MYH11 transcript coding for an in-frame fusion protein was detected. In a more extensive RT-PCR analysis with different primer pairs, we detected a second new chimeric CBFB-MYH11 transcript in 10 of 11 patients tested. The CBFB-MYH11 reading frame of the second transcript was maintained in one patient but not in the others. We show that the different CBFB-MYH11 transcripts in one patient arise from alternative splicing. Translation of the transcript in which the CBFB-MYH11 reading frame is not maintained leads to a slightly truncated CBFB protein.

Chromosome 16 aberrations are well known in acute nonlymphocytic leukemia (ANLL). The most frequent chromosome 16 aberration in ANLL subtype M4Eo is the inv(16)(p13q22). Recently, we showed that in 5 inv(16) patients with ANLL M4Eo the short arm breakpoints are clustered within a 14-kb genomic EcoRI fragment. We report here the identification of a gene situated in the 14-kb fragment. The gene, which codes for a myosin peptide, is disrupted by the inversion of chromosome 16 in the 5 patients. To the best of our knowledge, this is the first report of a myosin gene disrupted in leukemia.

LeukemiaDeletion of the multidrug resistance-associated protein (MRP1) gene in acute myeloid leukemia with inversion of chromosome 16 has no prognostic impact TO THE EDITORAcute myelomonocytic leukemia with bone marrow eosinophilia (AML FAB M4Eo) is a distinct subtype of acute myeloid leukemia (AML) which is associated with the chromosomal inversion inv(16)(p13q22) resulting in fusion of the MYH11 gene on 16p13 with the CBF␤ gene on 16q22. 1 In prospective studies it has been shown that AMLs with inv(16) are associated with a high complete remission (CR) rate and long remission durations when treated with high-dose cytarabine in postremission therapy. 2 Recently, deletions of sequences 150 to 350 kb in size centromeric to the p-arm breakpoint were described in subsets of 14% to 38% of AMLs with inv(16). [3][4][5][6] The affected genomic region contains two members of the superfamily of transmembrane transporters, the multidrug resistance-associated protein gene (MRP1) and the anthracycline resistance-associated gene (ARA), located within 9 kb of each other. Both genes are expressed in normal hematopoietic precursor cells and mediate resistance to a variety of chemotherapeutic agents. In a study of Kuss et al 3 MRP1 deletions were found in five out of 13 (38%) AML patients with inv(16). 3 Deletions were identified by fluorescence in situ hybridization (FISH) using a 3.8 kb sized cDNA probe representing parts of the MRP1 gene. Notably, the patients with the deletion had a significantly higher disease-free survival than those without the deletion. Based on these clinical data it was speculated that MRP1 deletion may be involved in the pathogenesis of AML with inv(16). The findings by Kuss et al 3 could not be confirmed in two subsequent studies. In the FISH study by Marlton et al 4 only six out of 42 (14%) AML cases with inv(16) were associated with 16p deletions using a cosmid contig as a probe. Furthermore, time to treatment failure was compared for the two patient groups and no difference was observed. Similar results were also reported in a study from Martinet et al. 5 One drawback of all these studies is that the analyses were performed retrospectively in small series of patients treated heterogenously.To prospectively evaluate the prognostic impact of MRP1 deletions in AML with inv(16) we analyzed 246 eligible AML patients treated within the German multicenter treatment trial AML HD93 conducted between 1993 and 1998. All patients received induction therapy consisting of two cycles of idarubicin, cytarabine (100 mg/m 2 ), and etoposide (ICE), followed by first consolidation treatment with high-dose cytarabine (3 g/m 2 × 6) and mitoxantrone (HAM). Patients with inv(16) were assigned to the low-risk arm of the study and obtained a second cycle HAM. Of the 246 patients, 25 had inv(16) as assessed by chromosome banding analysis and by FISH using the yeast artificial chromosome clone y854E2 spanning the p-arm breakpoint. Cases exhibiting inv(16) were subsequently analyzed for deletions at the p-arm breakpoint by ...

No abstract