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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We previously isolated cDNA clones, MLL-a and MLL-b, derived from the 11q23 breakpoint region and detected gene rearrangements with MLL-b cDNA in infantile leukemia cell lines with 11q23 abnormalities. We also showed chimeric mRNAs between MLL and genes on partner chromosomes such as 4q21 and 19p13. In the present study, we isolated overlapping MLL cDNA clones of 11 kb and demonstrated that MLL-a and MLL-b were derived from the same gene, MLL/ALL-1/HRX. Northern analysis with an MLL cDNA probe detected different signals in t(11;19) cell lines, one being sized 10 kb in two cell lines, KOCL-33 and KOCL-44, and the other being 9.2 kb in the cell line, KOPN-1. To elucidate the molecular basis for the heterogeneity, we isolated cDNA clones of a translocation-associated gene on chromosome 19, LTG19, as well as chimeric cDNAs from KOPN-1. Northern analysis with LTG19 cDNA demonstrated the identical gene, encoding serine/proline rich 559 amino acid polypeptide, to be involved in all three cell lines. Sequence comparison revealed that the LTG19 portion of the predicted chimeric protein of KOPN-1 was fused in frame and contained the C-terminal 189 amino acids. This was shorter by 366 amino acids than those of KOCL-33 and KOCL-44, also fused in frame. Reverse transcriptase-PCR analysis demonstrated complex chimeric mRNAs in cell lines and leukemia samples. Although a chimeric mRNA of KOPN-1 type was rare, its presence suggested that the shared C-terminal portion of 189 amino acids of LTG19 contains important signal(s) for malignant transformation.
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PMID:Two distinct portions of LTG19/ENL at 19p13 are involved in t(11;19) leukemia. 837 76

Recently, the MLL gene at 11q23 was found to be involved in a subset of leukemias with an 11q23 abnormality. In the present study, we isolated chimeric cDNAs between the MLL and a gene designated MLLT3 at 9p22 from a cDNA library of an IMS-M1 cell line with a t(9;11)(p22;q23) translocation, a representative karyotypic abnormality seen in acute monocytic leukemia. We also isolated a normal MLLT3 cDNA and found an open reading frame encoding at least 318 amino acids with high serine/proline content (24.8%). The chimeric mRNAs were demonstrated to be fused to MLL in frame, as found in t(11;19) and t(4;11) leukemias. The predicted MLLT3 protein demonstrated a significant homology to that of the MLLT1 gene at 19p13 involved in t(11;19) leukemia. The highest homology, up to 74.1%, was found in 86 amino acids of the C-terminus, suggesting that this region is of particular importance for leukemogenesis in t(9;11) leukemia. Northern blot analysis with the MLLT3 cDNA probe against normal tissues revealed multiple transcripts in lymphoid organs. A survey of hematopoietic cell lines demonstrated relatively stronger signals in cells belonging to megakaryocytic and erythroid lineages. As previously found in t(11;19) leukemia, heterogeneous MLL-MLLT3 chimeric mRNAs could be detected by the reverse transcriptase-polymerase chain reaction (RT-PCR) in t(9;11) leukemia samples.
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PMID:MLLT3 gene on 9p22 involved in t(9;11) leukemia encodes a serine/proline rich protein homologous to MLLT1 on 19p13. 841 10

The majority (approximately 75%) of infant acute leukaemias have a reciprocal translocation between chromosome 11q23 and one of several partner chromosomes. The gene at 11q23 (named MLL, ALL-1, HRX or HTRX-1; refs 2-6) has been cloned and shares homology with the Drosophila developmental gene trithorax. Rearrangements of this gene (called HRX here) occur in introns and cluster in a region of approximately 10 kb; individual patients have different breakpoints. Here we describe three pairs of infant twins with concordant leukaemia who each share unique (clonal) but non-constitutive HRX rearrangements in their leukaemic cells, providing evidence that the leukaemogenic event originates in utero and unequivocal support for the intra-placental 'metastasis' hypothesis for leukaemia concordance in twins.
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PMID:In utero rearrangements in the trithorax-related oncogene in infant leukaemias. 849 19

Translocations involving chromosome band 11q23, found in acute lymphoid and myeloid leukemias, disrupt the MLL gene. This gene encodes a putative transcription factor with regions of homology to several other proteins including the zinc fingers and other domains of the Drosophila trithorax gene product, and the "AT-hook" DNA-binding motif of high mobility group proteins. We have previously demonstrated that MLL contains transcriptional activation and repression domains using a GAL4 fusion protein system (21). The repression domain, which is capable of repressing transcription 3-5-fold, is located centromeric to the breakpoint region of MLL. The activation domain, located telomeric to the breakpoint region, activated transcription from a variety of promoters including ones containing only basal promoter elements. The level of activation was very high, ranging from 10-fold to more than 300-fold, depending on the promoter and cell line used for transient transfection. In translocations involving MLL, the protein produced from the der(11) chromosome which contains the critical junction for leukemogenesis includes the AT-hook domain and the repression domain. We assessed the DNA binding capability of the MLL AT-hook domain using bacterially expressed and purified AT-hook protein. In a gel mobility shift assay, the MLL AT-hook domain could bind cruciform DNA, recognizing structure rather than sequence of the target DNA. This binding could be specifically competed with Hoechst 33258 dye and with distamycin. In a nitrocellulose protein-DNA binding assay, the MLL AT-hook domain could bind to AT-rich SARs, but not to non-SAR DNA fragments. The role that the AT-hook binding to DNA may play in vivo is unclear, but it is likely that DNA binding could affect downstream gene regulation. The AT-hook domain retained on the der(11) would potentially recognize a different DNA target than the one normally recognized by the intact MLL protein. Furthermore, loss of an activation domain while retaining a repression domain on the der(11) chromosome could alter the expression of various downstream target genes, suggesting potential mechanisms of action for MLL in leukemia.
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PMID:The mixed lineage leukemia (MLL) protein involved in 11q23 translocations contains a domain that binds cruciform DNA and scaffold attachment region (SAR) DNA. 858 57

A 58-year-old woman complicated with rheumatoid arthritis (RA) was admitted to our hospital with right axillar lymphadenopathy and splenomegaly in November 1992. She was diagnosed as an anaplastic large-cell lymphoma (Ki-1 +) (stage IIIB) on the histological findings of the right axillar lymph nodes. She was treated with 11 courses of CHOP regimen between February 1992 and May 1993, and with mitoxantrone, etoposide (VP-16) and predonisolone in April 1992 and May 1993. The right axillar lymph nodes and spleen were irradiated at a dose of 36Gy in October 1992 and May 1993 respectively. In May 1993, peripheral blood showed WBC 89,000/microliter with 96% myeloblasts, Hb 8.3 g/dl, and Plt 124,000/microliter. Bone marrow aspirate revealed hypercellularity with 90% myeloblasts, which were positive for CD13 and HLA-DR. She was diagnosed as AML (M1). The karyotype showed normal. Southern blot analysis did not reveal the rearrangement of the MLL gene. She received the BHAC-DMP regimen and obtained complete remission. However, she relapsed during consolidation therapy, and died of cerebral bleeding. An autopsy revealed absence of a residual tumor. The mean interval from exposure to alkylating agent to the onset of secondary leukemia has been reported to be about 5 years, in contrast to a shortened interval of about 2 years for VP-16-induced leukemia. In our patient, it took only 1 year to have AML following chemotherapy for Ki-1 lymphoma. This suggests that her AML might be induced not only by treatments for RA and Ki-1 lymphoma, but also by immunological background such as RA.
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PMID:[Acute myeloid leukemia (M1) following chemotherapy for Ki-1 lymphoma complicated with rheumatoid arthritis]. 858 73

We describe a case of neonatal mixed lineage leukaemia which presented with a dominant B progenitor lymphoblast population plus a minor monocytic component. Treatment of the patient with corticosteroid and Ara-C resulted in loss of lymphoblasts and a rapid (within 7 days) increase and dominance of the monocytic component. The common clonal origin of the two cell types was evident from the identical rearrangement in the MLL gene and a shared rearrangement of one IGH allele. In common with other neonatal or infant ALL with MLL gene rearrangements, this leukaemia may have originated in a common B-monocytic lineage stem cell during foetal haemopoiesis. The observations further suggest that the therapeutic impact of the MLL gene rearrangement is to some extent dependent on the cellular context in which it is expressed.
Leukemia 1995 Dec
PMID:Rapid intraclonal switch of lineage dominance in congenital leukaemia with a MLL gene rearrangement. 860 12

We report the different presentation features and clinical outcome between two identical infant twins with acute lymphoblastic leukaemia with a shared clonal disease and MLL gene rearrangement. One twin relapsed and died, but the other is in complete remission > 4 years after diagnosis. These data, and similar observations on other twin infants with leukaemia, suggest that despite a common clonal in utero, post-natally these leukaemias can evolve independently, at different rates, in the twinned individuals, and that the usually fatal leukaemia associated with t(4;11) MLL gene rearrangement can be effectively treated when the leukaemic burden is small.
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PMID:Discordant clinical presentation and outcome in infant twins sharing a common clonal leukaemia. 861 55

Southern blot analysis with a cDNA probe of MLL indicated that the breakpoint is in a BamHI 8.3 kb fragment which carries the exon 5-11 of MLL gene in DNA from an adult acute myelomonocytic leukaemia with a t(11;22) (q23;q11) translocation. The structural analysis of the rearranged MLL locus demonstrated that the breakpoint is localized between exon 8 and 9 of MLL locus. The normal counterpart fused to the MLL locus was proved to be derived from chromosome 22q11(AF-22) by somatic cell hybrids analysis and FISH. By FISH, AF-22 was localized to the region more centromeric to the BCR gene.
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PMID:Molecular cloning of the breakpoint of t(11;22) (q23;q11) chromosome translocation in an adult acute myelomonocytic leukaemia. 861 37

Translocations involving chromosome band 11q23 are frequently found in infant acute leukemia and involve rearrangement of the MLL gene. In this study, 29 cases of adult acute myeloid leukemia (AML) were analyzed to determine the frequency of MLL gene rearrangement. Of these, 19 cases were karyotyped and none showed cytogenetic evidence of 11q23 aberration. MLL rearrangements were demonstrable in four cases, giving a frequency of 14% (4/29). Only one of the four cases with MLL rearrangement showed features typical of leukemia with 11q23 aberration; other cases were indistinguishable from those without MLL rearrangement. There was no apparent difference in presentation blast count, remission, and survival duration when cases with or without MLL rearrangement were compared. Clinicopathologic features of adult AML with MLL rearrangements may be heterogeneous.
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PMID:Molecular rearrangement of the MLL gene in adult acute myeloid leukemia without cytogenetic evidence of 11q23 aberration. 861 78

We describe a patient with acute monocytic leukemia (M5a, FAB classification) associated with a new type of variant translocation (9;11). Southern blot analysis showed the rearrangement of the MLL (ALL-1/HRX) gene at 11q23. Fluorescence in situ hybridization (FISH) with painting probes of chromosomes 9, 11, and 22 revealed the translocation as t(9;11;22) (p22;q23;q11). This is more evidence that the production of chimeric mRNA following the translocation of the LTG9 (MLLT3/AF9) gene at 9p22 to 11q is a critical event in this leukemia subtype.
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PMID:Translocation (9;11;22)(p22;q23;q11). A new type of complex variant translocation of t(9;11)(p22;q23) with MLL rearrangement. 863 Sep 74


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