Consistent detection of CALM-AF10 chimaeric transcripts in haematological malignancies with t(10;11)(p13;q14) and identification of novel transcripts

The t(10;11)(p13-14;q14-21) is a rare but recurring translocation associate d with acute lymphoblastic leukaemia (ALL) and acute myeloid leukaemia (AML ). Recently the CALM gene was cloned from the t(10:11) breakpoint of U937 a nd fused to AF10, a putative transcription factor, which had been identifie d as one of the fusion partners of the MLL gene. In order to define the inv olvement of these genes in primary leukaemias and cell lines with t(10;11), we analysed the expression of fusion transcripts by reverse transcriptase- polymerase chain reaction (RT-PCR) in five patient samples including ALL, A ML and lymphoblastic lymphoma, and three monocytic cell lines (P31/Fujioka, KP-Mo-TS and U937. The CALM-AF10 fusion transcript was detected in all sam ples: however, the AF10-CALM fusion was not detected in two patient samples and one cell line. In RT-PCR analysis there were six Isoforms of the CALM- AF10 fusion. transcripts and five of AF10-CALM fusion transcripts, We also detected novel transcripts in U937, Sequence analysis revealed that all the se isoforms had in-frame junctions and that some of them resulted from alte rnative splicing at different exons of CALM and others from different break points at CALM and/or AF10, There were at least two different breakpoints o f CALM and three of AF10 gene. Our results suggest that the CALM-AF10 fusio n gene is a constant feature and is involved in the pathogenesis of haemato logical malignancies with t(10;11)/p13-14;q14-21), shelving various and oft en multilineage phenotypes. Thus, t(10;11) needs to be investigated by RT-P CR for identification of the genes involved.