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More than 70 different mixed lineage leukemia (MLL) rearrangements involving 11q23 have been molecularly characterized in acute leukemia. Among these, the MLLT11 gene is highly unique as MLL fusion partner because the entire open reading frame is usually fused in-frame to the N-terminal portion of the MLL gene. By using molecular genetic methods, we identified the chromosomal fusion site within MLL exon 10 sequences which were fused to the MLLT11 intron 1 sequences. This unusual break site results in the creation of two in-frame MLL-MLLT11 fusion transcripts in this acute myeloid leukemia patient with t(1;11)(q21;q23). One fusion transcript represents a normal splice product, while the other contains intronic sequences and a cryptic splice event in order to generate an intact fusion transcript. We also reviewed all published articles which have reported t(1;11)(q21;q23) in myeloid or lymphoid neoplasm and attempted to summarize these published data. Of interest, pediatric patients displayed a significant larger portion of unique balanced translocations (n = 40), while complex karyotypes were less often identified (n = 12). Vice versa, in adult leukemia patients, complex karyotypes (n = 5) were more frequent than unique balanced translocations (n = 2)., (Copyright © 2012 S. Karger AG, Basel.)

Although a normal karyotype according to conventional cytogenetic analysis in association with cryptic t(15;17) has been infrequently reported in cases of acute promyelocytic leukemia (APL), a fluorescence in situ hybridization (FISH)-negative cryptic PML-RARA rearrangement is even more rare, with only 12 such APL cases of FISH-negative cryptic PML-RARA rearrangements in the literature. Reported here is an additional clinical APL case with a FISH-negative cryptic PML-RARA rearrangement, confirmed by long-distance DNA polymerase chain reaction method. Discussion includes a relevant literature review of similar cases. DNA-PCR can be a useful tool for the analysis of complex and cryptic rearrangements., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The translocation t(10;11)(p13;q14q21) has been found to be recurrent in acute lymphoblastic and myeloid leukemias, and results in the fusion of the clathrin assembly lymphoid myeloid leukemia (CALM) gene with the AF10 gene; these genes are present on chromosomes 11 and 10, respectively. Because the CALM-AF10 rearrangement is a rare chromosomal abnormality, it is not included in routine molecular tests for acute leukemia. Here, we describe the cases of 2 patients with the CALM-AF10 fusion gene. The first patient (case 1) was diagnosed with T-cell ALL, and the second patient (case 2) was diagnosed with AML. Both patient samples showed expression of the homeobox A gene cluster and the histone methyltransferase hDOT1L, which suggests that they mediate leukemic transformation in CALM-AF10-positive and mixed-lineage leukemia-AF10-positive leukemias. Both patients achieved complete remission after induction chemotherapy. The first patient (case 1) relapsed after double-unit cord blood transplantation; there was no evidence of relapse in the second patient (case 2) after allogenic peripheral blood stem cell transplantation. Since CALM-AF10- positive leukemias have been shown to have poor prognosis with conventional therapy, molecular tests for CALM-AF10 rearrangement would be necessary to detect minimal residual disease during follow-up.