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Biomedical subjects

M M Le Beau

Publications and source records attributed to M M Le Beau.

At least 19 recordsLinked to original sources
PubMed2005

Impact of disease burden at time of allogeneic stem cell transplantation in adults with acute myeloid leukemia and myelodysplastic syndromes.

The impact of disease burden on the outcome of patients with acute myeloid leukemia (AML) undergoing allogeneic stem cell transplantation (SCT) has not been well defined. Data from several retrospective series suggest that overt leukemia at the time of transplant increases the risk of relapse. We reviewed the outcomes of 68 consecutive adults with AML (n=60) or myelodysplastic syndromes (MDS) (n=8) who received an allogeneic SCT at the University of Chicago between May 1986 and October 2002 to confirm the importance of currently recognized risk factors for overall survival (OS) and progression-free survival (PFS). In addition, we wanted to determine whether quantification of residual disease by blast percentage or cytogenetic abnormalities at the time of SCT was correlated with outcome. AML subtypes based on the FAB classification were as follows: M0=9, M1=9, M2=16, M3=2, M4=16, M5=3, M6=5. Cytogenetic analysis was available from 52 patients. Using standard morphologic criteria, 34 patients were in complete remission (CR) and 34 had visible leukemia present. The majority of donors were HLA-identical siblings (n=55). In all, 56 patients received myeloablative conditioning regimens and 12 received a reduced-intensity, fludarabine-based conditioning regimen. OS and PFS times were 7.1 months (95% CI, 4.8-10.4) and 5.1 months (95% CI, 3.2-7.8), respectively. Median follow-up from SCT was 4.6 years (range, 0.6-17.0) for survivors. In multivariate analysis, the following factors were found to be associated with worse survival: (1) increased percentage of blasts in the bone marrow at the time of SCT, (2) presence of acute graft-versus-host disease, (3) mismatched donor, (4) Zubrod performance score of >/=2, and (5) age >/=45 years. We also found a trend towards improved outcome among patients in cytogenetic remission as compared to those who had residual cytogenetic abnormalities and those in overt relapse. These data support an association between pre-transplant disease burden and poor outcome after SCT.

Adult↗
PubMed2001

Point mutation in essential genes with loss or mutation of the second allele: relevance to the retention of tumor-specific antigens.

Antigens that are tumor specific yet retained by tumor cells despite tumor progression offer stable and specific targets for immunologic and possibly other therapeutic interventions. Therefore, we have studied two CD4(+) T cell-recognized tumor-specific antigens that were retained during evolution of two ultraviolet-light-induced murine cancers to more aggressive growth. The antigens are ribosomal proteins altered by somatic tumor-specific point mutations, and the progressor (PRO) variants lack the corresponding normal alleles. In the first tumor, 6132A-PRO, the antigen is encoded by a point-mutated L9 ribosomal protein gene. The tumor lacks the normal L9 allele because of an interstitial deletion from chromosome 5. In the second tumor, 6139B-PRO, both alleles of the L26 gene have point mutations, and each encodes a different tumor-specific CD4(+) T cell-recognized antigen. Thus, for both L9 and L26 genes, we observe "two hit" kinetics commonly observed in genes suppressing tumor growth. Indeed, reintroduction of the lost wild-type L9 allele into the 6132A-PRO variant suppressed the growth of the tumor cells in vivo. Since both L9 and L26 encode proteins essential for ribosomal biogenesis, complete loss of the tumor-specific target antigens in the absence of a normal allele would abrogate tumor growth.

Alleles↗
PubMed2001

Transcript map and comparative analysis of the 1.5-Mb commonly deleted segment of human 5q31 in malignant myeloid diseases with a del(5q).

Loss of a whole chromosome 5, or a del(5q), are recurring abnormalities in malignant myeloid diseases. In previous studies, we defined a commonly deleted segment (CDS) of 1.5 Mb between D5S479 and D5S500 in patients with a del(5q), and we established a P1 artificial chromosome-based contig encompassing this interval. To identify candidate tumor suppressor genes (TSGs), we developed a transcript map of the CDS. The map contains 18 genes and 12 expressed sequence tags/UniGenes. Among the 18 genes are 10 genes that were previously cloned and 8 novel genes. The newly identified genes include CDC23, which encodes a component of the anaphase-promoting complex; RAB6KIFL, which encodes a kinesin-like protein involved in organelle transport; and KLHL3, which encodes a human homologue of the Drosophila ring canal protein, kelch. We determined the intron/exon organization of 14 genes and eliminated each gene as a classical TSG by mutation analysis. In addition, we established a single-nucleotide polymorphism map as well as a map of the mouse genome that is syntenic to the CDS of human 5q31. The development of a transcription map will facilitate the molecular cloning of a myeloid leukemia suppressor gene on 5q.

Acute Disease↗
PubMed2001

Candidate gene isolation and comparative analysis of a commonly deleted segment of 7q22 implicated in myeloid malignancies.

Monosomy 7 and deletion of 7q are recurring abnormalities in malignant myeloid diseases. Here we extensively characterize an approximately 2-Mb commonly deleted segment (CDS) of 7q22 bounded by D7S1503 and D7S1841. Approximately 1.8 Mb of sequence have been generated from this interval, facilitating the construction of a transcript map that includes large numbers of genes and ESTs. The intron/exon organization of seven genes and expression patterns of three genes were determined, and leukemia samples were screened for mutations in five genes. We have used polymorphic markers from this region to examine leukemia cells for allelic loss within 7q22. Finally, we isolated mouse genomic clones orthologous to several of the characterized human genes. Fluorescence in situ hybridization studies using these clones indicate that a region of orthologous synteny lies on proximal mouse chromosome 5. These resources should greatly accelerate the pace of candidate gene discovery in this region.

Acute Disease↗
PubMed2001

Modeling myeloid leukemia tumor suppressor gene inactivation in the mouse.

Introducing dominant oncogenic alterations uncovered in human myeloid malignancies into the mouse germline provides a powerful approach for studying leukemogenesis. However, little is known about how gene inactivation contributes to the development of myeloid malignancies. We describe how Nf1 mutant mice provide one example in which disrupting a tumor suppressor gene has been used to generate an informative murine leukemia model. We also discuss how chromosome engineering technologies are being harnessed to model the segmental deletions found in myeloid malignancies, and how these approaches can be combined with retrovirally medicated insertional mutagenesis to generate new models and for gene discovery.

Animals↗
PubMed2001

Chromosomal instability in chromosome band 12p13: multiple breaks leading to complex rearrangements including cytogenetically undetectable sub-clones.

During fluorescence in situ hybridization (FISH) analysis of metaphase cells from 70 patients with lymphoid and myeloid hematologic malignancies and chromosomal rearrangements involving band 12p13, we identified nine patients (four with lymphoid malignancies, four with myeloid malignancies and one with biphenotypic leukemia) who showed more complicated rearrangements than we had expected from conventional cytogenetic study. In six patients, multiple breaks occurred in small segments of 12p with subsequent translocations and insertions of these segments into other chromosomes, sometimes to unexpected regions. In three patients additional chromosome breaks resulted in a sub-clone which was cytogenetically indistinguishable from the main clone in each patient based on the cytogenetic analysis. These subtle molecular events were detected exclusively in a region covering TEL/ETV6 and KIP1/CDKN1B. Seven of nine had a previous history of chemo/radiotherapy; all the patients showed complex karyotypes, even though they were newly diagnosed with leukemia. Survival data were available in five patients, and all survived less than 6 months. These findings suggest that the 12p13 region, especially the above-mentioned region, is genetically unstable and fragile. It is likely that multiple chromosome breaks were induced through mutagens used in chemo/ radiotherapy, and are associated with a sub-group of patients with an extremely bad prognosis.

Chromosome Fragility↗
PubMed2001

Detection of translocations affecting the BCL6 locus in B cell non-Hodgkin's lymphoma by interphase fluorescence in situ hybridization.

Structural alterations in 3q27 affecting the BCL6 locus are among the most frequent changes in B-NHL. The aim of the present study was to establish an interphase-FISH assay for the detection of all diverse BCL6 translocations in B-NHL. Two different approaches were tested, one using a PAC-clone spanning the major breakpoint region (MBR) of BCL6 (span-assay), and another using two BAC clones flanking the MBR (flank-assay). Interphase FISH with the span-assay detected the various BCL6 translocations in seven B-NHL cell lines. The dual-color flank-assay was evaluated in two laboratories independently: in normal controls, the cutoff level for false-positive signals was 2.6%, whereas the cutoff level for false-negatives in the seven cell lines was 7.5%. To test the feasibility of the FISH strategies, 30 samples from patients with B-NHL with cytogenetic abnormalities of 3q27 were evaluated with both assays. In 21 cases, the span-assay indicated a BCL6 rearrangement. In 18 of the 21 cases, the dual-color flank-assay confirmed the translocation including 12 different partner chromosomal loci. The three false-positive cases detected with the span-assay showed trisomy of chromosome 3 by cytogenetic analyses, and they were correctly classified as non-rearranged with the flank-assay. In summary, our FISH strategy using two differently labeled flanking BCL6 BAC probes provides a robust, sensitive, and reproducible method for the detection of common and uncommon abnormalities of BCL6 gene in interphase nuclei. The routine application of this assay to patients with B-NHL will allow the assessment of the diagnostic and prognostic significance of BCL6 rearrangements.

Base Sequence↗
PubMed2001

The cytogenetics of myelodysplastic syndromes.

The myelodysplastic syndromes are a collection of five clinico-pathological entities with a wide spectrum of clinical behaviours and survival outcomes. Cytogenetic analysis has been instrumental in refining the prognosis, predicting the likelihood of progression to acute myeloid leukaemia and median survival, and in establishing clonality of these diseases. This review highlights the most frequent abnormalities and summarizes their clinical and genetic features.

Chromosome Aberrations↗
PubMed2001

The API2/MALT1 fusion product may lead to germinal center B cell lymphomas by suppression of apoptosis.

Low-grade B cell lymphomas of mucosa-associated lymphoid tissue (MALT) represent a distinct clinicopathological entity that arises in a wide variety of extranodal sites. Genetically, MALT lymphomas are characterized by the t(11;18)(q21;q21). The genes involved in this translocation have been identified to be API2 on chromosome 11, which encodes an apoptotic inhibitor, and MALT1, a novel gene on chromosome 18. We identified the t(11;18)(q21;q21) by Southern blot analysis and reverse transcriptase PCR in 42% of a panel of extranodal MALT lymphomas. We also identified the breakpoints within the API2 and MALT1 genes in 7 patients, which revealed a consistent breakpoint after the third baculoviral inhibitor of apoptosis repeat domain within API2, and variable breakpoints in MALT1. We determined the API2/MALT1 fusion transcript in 2 cases by Northern blot analysis and also showed that MALT1 mRNA is constitutively expressed in a variety of human tissues. To understand the functional consequence of the translocation, we determined the pattern of expression of API2 and MALT1 through B lineage differentiation. API2 was expressed only in cell lines which correspond to mature B cells, whereas MALT1 mRNA was detectable in pre-B cells, mature B cells and plasma cells. These results suggest that fusion of MALT1 to API2 mediated by the t(11;18)(q21;q21) may result in an increased inhibition of germinal center B cell apoptosis and subsequent development of MALT lymphomas.

Apoptosis↗
PubMed2000

Pesticide exposures in children with non-Hodgkin lymphoma.

BACKGROUND: The association between pesticide exposure and non-Hodgkin lymphoma (NHL) in adults has been the subject of numerous case-control and cohort studies. However, to the authors' knowledge, data regarding pesticide exposures in children diagnosed with NHL have been lacking. METHODS: The Children's Cancer Group conducted a study comparing 268 children who developed NHL or leukemia with bulk disease with a group of matched, randomly selected regional population controls. The telephone interviews of both the case and control mothers included selected questions regarding occupational and home exposures to pesticides around the time of the index pregnancy and exposure of the child. RESULTS: A significant association was found between risk of NHL and increased frequency of reported pesticide use in the home (odds ratio [OR] = 7.3 for use most days; trend P = 0.05), professional exterminations within the home (OR = 3.0; P = 0.002), and postnatal exposure (OR = 2.4; P = 0.001). Elevated risks were found for T-cell and B-cell lymphomas; for lymphoblastic, large cell, and Burkitt morphologies; and in both young (age < 6 years) and older children. There was an increased risk of NHL with occupational exposure to pesticides (OR = 1.7) that was not significant overall, but that was significant for Burkitt lymphoma (OR = 9.6; P < 0.05). CONCLUSIONS: The results of the current study provide further evidence linking pesticide exposure to the risk of NHL, but the authors were unable to implicate any specific agent.

Adolescent↗
PubMed2000

cDNA cloning and genomic structure of three genes localized to human chromosome band 5q31 encoding potential nuclear proteins.

Loss of a whole chromosome 5, or a del(5q), is a recurring abnormality in malignant myeloid diseases. By cytogenetic and molecular analyses, we delineated previously a 1- to 1.5-Mb region that is deleted in all patients with a del(5q). In our efforts to identify a myeloid tumor suppressor gene within the commonly deleted segment (CDS), we have cloned and characterized the genes encoding three putative nuclear proteins, each of which contains a bipartite nuclear localization signal (NLS). In addition, C5ORF5 contains a putative rhoGAP domain at the N-terminus, C5ORF6 has a proline-rich sequence near the N-terminus, and C5ORF7 has a zinc-finger domain that partially overlaps the NLS. All three genes are ubiquitously expressed and encode novel proteins. The C5ORF5 cDNA is 5.47 kb encoding a protein of 915 amino acids (aa) with a predicted molecular mass of approximately 105 kDa. C5ORF5 has 23 exons spanning over 27 kb. The C5ORF6 transcript is 4.1 kb encoding a protein of 392 aa with a predicted molecular mass of approximately 43 kDa. C5ORF6 has 5 exons and spans approximately 11 kb. The C5ORF7 cDNA is 6.3 kb and encodes a protein of 1417 aa with a predicted molecular mass of approximately 155 kDa. C5ORF7 has 24 exons spanning approximately 64 kb. All three genes were localized to the distal half of the CDS between D5S1983 and D5S500. We evaluated each as a candidate tumor suppressor gene by the analysis of myeloid leukemia cells from patients with -5/del(5q), but no inactivating mutations were identified.

Amino Acid Sequence↗
PubMed2000

Refinement of the smallest commonly deleted segment of chromosome 20 in malignant myeloid diseases and development of a PAC-based physical and transcription map.

A deletion of the long arm of chromosome 20, del(20q), is a recurring abnormality in malignant myeloid diseases. In previous studies, we delineated a commonly deleted segment (CDS) of 5 Mb within band 20q12 flanked by D20S206 (proximal) and D20S481 (distal). We have generated a detailed physical map of P1 artificial chromosome (PAC) clones of this interval as well as a transcriptional map. The contig consists of 81 clones to which 152 markers (27 genes, 45 unique expressed sequence tags (ESTs) or UniGenes, 24 polymorphisms, and 56 sequence-tagged sites) have been mapped. Using PAC clones for fluorescence in situ hybridization analysis of myeloid leukemia cells with reciprocal translocations of 20q, or unbalanced rearrangements leading to loss of 20q, we have narrowed the CDS to an approximately 250-kb interval encompassing two overlapping PACs, P201E16 and P29M7 (between EST AA368224 and D20S481). This interval is gene-rich and contains 5 characterized genes, 4 UniGenes, and 9 single ESTs. The development of a transcriptional map and the identification of the smallest CDS will facilitate the molecular cloning of a myeloid leukemia suppressor gene on 20q.

Alleles↗
PubMed2000

Molecular characterization of KLHL3, a human homologue of the Drosophila kelch gene.

The Drosophila kelch protein is a structural component of ring canals and is required for oocyte maturation. Here, we report the cloning and genomic structure of a new human homologue of kelch, KLHL3. At the amino acid level, KLHL3 shares 77% similarity with Drosophila kelch and 89% similarity with Mayven (KLHL2), another human kelch homolog. The approximately 6.5-kb mRNA has a single open reading frame encoding a protein of 587 amino acids with a predicted molecular mass of 650 kDa. Like kelch and KLHL2, the KLHL3 protein contains a poxvirus and zinc finger domain at the N-terminus and six tandem repeats (kelch repeats) at the C-terminus. At least three isoforms, which differ in the length of the N-terminus, are produced and may be the result of alternative promoter usage. We also identified alternative polyadenylation sites and alternative splicing; thus, as many as 12 mRNA variants and six putative protein isoforms could be produced. The KLHL3 gene is mapped to human chromosome 5, band q31, contains 17 exons, and spans approximately 120 kb of genomic DNA. KLHL3 maps within the smallest commonly deleted segment in myeloid leukemias characterized by a deletion of 5q; however, we detected no inactivating mutations of KLHL3 in malignant myeloid disorders with loss of 5q.

Acute Disease↗
PubMed2000

cDNA cloning, expression pattern, genomic structure and chromosomal location of RAB6KIFL, a human kinesin-like gene.

Kinesin-like proteins are microtubule-associated motors that play important roles in intracellular transport and cell division. We report here the characterization of a new human kinesin-like protein, Rabkinesin6 (RAB6KIFL). The composite cDNA sequence is 2957bp, and encodes a protein of 890 amino acids with a predicted molecular weight of 100kDa. It has high homology (93% similarity) with the mouse kinesin-like protein, Rab6kifl, indicating that it is the human homologue of the mouse gene. RAB6KIFL has all of the structural characteristics required to function as a microtubule-associated motor. Unlike the mouse gene which is ubiquitously expressed, RAB6KIFL expression appears to be tissue specific. It is widely expressed in fetal tissues, abundantly expressed in adult thymus, bone marrow and testis, and is expressed at low levels in heart, placenta and spleen. The RAB6KIFL gene is mapped to human chromosome 5, band q31, spans approximately 8.5kb of genomic DNA, and contains 19 exons. RAB6KIFL maps within the smallest commonly deleted segment in myeloid leukemias characterized by a deletion of 5q; however, we detected no mutations of RAB6KIFL in malignant myeloid disorders with loss of 5q. The description of this human kinesin-like protein may provide a better understanding of the diversity of this large family of proteins.

Acute Disease↗
PubMed2000

Anergic T lymphocytes selectively express an integrin regulatory protein of the cytohesin family.

It has been proposed that the maintenance of T cell anergy depends on the induction of negative regulatory factors. Differential display of reverse transcribed RNA was used to identify novel genes that might mediate this function in anergic Th1 clones. We report that anergic Th1 clones do indeed express a genetic program different from that of responsive T cells. Moreover, one gene, the general receptor of phosphoinositides 1 (GRP1), was selectively induced in anergic T cells. The GRP1, located in the plasma membrane, regulated integrin-mediated adhesion and was invariably associated with unresponsiveness in multiple models of anergy. T cells expressing retrovirally transduced GRP1 exhibited normal proliferation and cytokine production. However, GRP1-transduced T cells were not stable and rapidly lost GRP1 expression. Thus, although GRP1 may not directly mediate T cell anergy, it regulates cell expansion and survival, perhaps through its integrin-associated activities.

Amino Acid Sequence↗
PubMed2000

Fluorescence in situ hybridization: uses and limitations.

The development of molecular hybridization techniques such as fluorescence in situ hybridization (FISH) has had a major Impact on efforts to detect and characterize the genetic changes that give rise to human tumors. With probes designed to Identify specific chromosomes and chromosomal regions, FISH is used routinely by cytogenetics and pathology laboratories to identify recurring chromosomal abnormalities associated with hematologic malignant diseases. In many cases FISH analysis provides increased sensitivity, in that cytogenetic abnormalities have been found In samples that appeared to be normal by morphologic and conventional cytogenetic examination. The combination of cytogenetic, FISH, and molecular analyses provides a powerful approach for diagnosing and subclassifying malignant diseases into clinically and biologically relevant subgroups, In selecting appropriate therapy, and in monitoring the efficacy of therapeutic regimens.

Cytogenetic Analysis↗
PubMed2000

Identification and molecular characterization of CALM/AF10fusion products in T cell acute lymphoblastic leukemia and acute myeloid leukemia.

The t(10;11)(p12-p13;q14-q21) observed in a subset of patients with either acute lymphoblastic leukemia or acute myeloid leukemia has been shown to result in the fusion of AF10 on chromosome 10 with CALM (also named CLTH) on chromosome 11. AF10 was originally identified as a fusion partner of MLL in the t(10;11)(p12-p13;q23) observed in myeloid leukemia. CALM is a newly isolated gene, cloned as the fusion partner of AF10 in the monocytoid cell line, U937. In order to understand the relationship between MLL, AF10, CALM and the leukemic process, fluorescence in situ hybridization and reverse transcriptase polymerase chain reaction were used to study a series of nine leukemia patients with a t(10;11). Six had myeloid leukemia (AML-M0, AML-M1, AML-M4 and AML-M5) and three had T cell lymphoblastic leukemia. We identified four different CALM/AF10 fusion products in five patients and AF10/CALM reciprocal message in one. We conclude that fusion of CALM and AF10 is a recurring abnormality in both lymphoid and myeloid leukemias of various types including AML-M5, and that the breakpoints in the two types of leukemia do not differ. Our data indicate that the CALM/AF10 fusion product on the der(10) chromosome is critical to leukemogenesis. Leukemia (2000) 14, 100-104.

Acute Disease↗