Translocation t(1;11)(q21;q23), a new subgroup within M4 acute nonlymphocytic leukemia

Molecular identification of a new splicing variant of the MLL - MLLT11 fusion transcript in an adult with acute myeloid leukemia and t(1;11)(q21;q23)

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).

C/EBPbeta suppression by interruption of CUGBP1 resulting from a complex rearrangement of MLL

Translocations involving the mixed-lineage leukemia gene (MLL) confer a poor prognosis in acute leukemias. In t(1;11)(q21;q23), MLL is fused reciprocally with AF1q. Here we describe a t(1;11)(q21;q23) with a secondary event involving insertion of the telomeric portion of MLL into the p arm of chromosome 11 (11p11). We show that this latter event interrupts the CUG triplet repeat binding protein-1 (CUGBP1) gene, a translational enhancer of C/EBPbeta. We then showed that these cells have reduced expression of CUGBP1 and C/EBPbeta when compared to other AML blasts. This is the first report to describe insertional disruption of the CUGBP1 gene and to suggest a role for the CUGBP1-C/EBPbeta pathway in leukemogenesis.

Constitutional balanced translocations in alveolar rhabdomyosarcoma

Chromosomal analysis of tumor tissue from two children with alveolar rhabdomyosarcoma revealed t(1;5)(q32;q31) and t(1;22)(q21;q11.2) in all metaphases examined, respectively. Peripheral blood lymphocytes carried the same cytogenetic abnormality as that of the tumor cells in both patients. Parental lymphocytes were karyotypically normal in the patient with t(1;22), indicating a de novo constitutional translocation, but t(1;5) was paternally inherited in the other patient. The presence of constitutional translocations in these two children might have contributed to the development of alveolar rhabdomyosarcoma.

Cytogenetic analysis in children with acute nonlymphocytic leukemia

In this work we present the results of cytogenetic analysis of the malignant cells in 27 children with acute nonlymphocytic leukemia (ANLL). The aim of our investigations was to determine the frequency and types of chromosome aberrations in our population of children with ANLL. Successful cytogenetic analysis was carried out in 24 (89%) patients. Aberrant karyotypes of malignant cells were established in 58% of the cases. The most frequent chromosomal abnormality was t(8;21), identified in 5 (20.8%) patients, i.e., 4 of 10 M2-ANLL. Aberration frequency of chromosome 11 was 16.6% and was identified in 3 of 8 M5-ANLL. Trisomy 8 and monosomy 7 were identified in one patient each with M3 and M2-ANLL, respectively. del(13), a rare chromosome aberration in hemoblastoses, was found in a child with M1,t(8;21) and the loss of chromosome Y. Translocation t(1;11;21) with a break in regions 1q23, 11q23, and 21q22, is unusual and was identified in a boy with M2-ANLL; it can be considered as a variant form of the t(8;21).

Ewing's sarcoma t(11;22) in a case of acute nonlymphocytic leukemia

Chromosome analysis of bone marrow cells from a patient with acute nonlymphocytic leukemia M2 revealed the translocation t(11;22)(q24;q12) usually associated with Ewing's sarcoma. Molecular investigations ruled out the possibility that this was a variant Philadelphia translocation with breakpoints in the major breakpoint cluster region. Although cytogenetic analysis was not available at diagnosis, this abnormality was found both pre- and postallogeneic bone marrow transplant.