T-cell receptor alpha-chain gene is split in a human T-cell leukemia cell line with a t(11;14)(p15;q11)

LIM domain only 1: an oncogenic transcription cofactor contributing to the tumorigenesis of multiple cancer types

ABSTRACT

The LIM domain only 1 (LMO1) gene belongs to the LMO family of genes that encodes a group of transcriptional cofactors. This group of transcriptional cofactors regulates gene transcription by acting as a key "connector" or "scaffold" in transcription complexes. All LMOs, including LMO1, are important players in the process of tumorigenesis. Unique biological features of LMO1 distinct from other LMO members, such as its tissue-specific expression patterns, interacting proteins, and transcriptional targets, have been increasingly recognized. Studies indicated that LMO1 plays a critical oncogenic role in various types of cancers, including T-cell acute lymphoblastic leukemia, neuroblastoma, gastric cancer, lung cancer, and prostate cancer. The molecular mechanisms underlying such functions of LMO1 have also been investigated, but they are currently far from being fully elucidated. Here, we focus on reviewing the current findings on the role of LMO1 in tumorigenesis, the mechanisms of its oncogenic action, and the mechanisms that drive its aberrant activation in cancers. We also briefly review its roles in the development process and non-cancer diseases. Finally, we discuss the remaining questions and future investigations required for promoting the translation of laboratory findings to clinical applications, including cancer diagnosis and treatment.

Characterization of Camptothecin-induced Genomic Changes in the Camptothecin-resistant T-ALL-derived Cell Line CPT-K5

Acquisition of resistance to topoisomerase I (TOP1)-targeting camptothecin (CPT) derivatives is a major clinical problem. Little is known about the underlying chromosomal and genomic mechanisms. We characterized the CPT-K5 cell line expressing mutant CPT-resistant TOP1 and its parental T-cell derived acute lymphoblastic leukemia CPT-sensitive RPMI-8402 cell line by karyotyping and molecular genetic methods, including subtractive oligo-based array comparative genomic hybridization (soaCGH) analysis. Karyotyping revealed that CPT-K5 cells had acquired additional structural aberrations and a reduced modal chromosomal number compared to RPMI-8402. soaCGH analysis identified vast copy number alterations and >200 unbalanced DNA breakpoints distributed unevenly across the chromosomal complement in CPT-K5. In addition, the short tandem repeat alleles were found to be highly different between CPT-K5 and its parental cell line. We identified copy number alterations affecting genes important for maintaining genome integrity and reducing CPT-induced DNA damage. We show for the first time that short tandem repeats are targets for TOP1 cleavage, that can be differentially stimulated by CPT.

DUB-2 is a member of a novel family of cytokine-inducible deubiquitinating enzymes

Cytokines regulate cell growth by inducing the expression of specific target genes. We have recently identified a cytokine-inducible, immediate-early gene, DUB-1, that encodes a deubiquitinating enzyme with growth regulatory activity. In the current study, we have isolated a highly related gene, DUB-2, that is induced by interleukin-2. The DUB-2 mRNA was induced in T cells as an immediate-early gene and was rapidly down-regulated. Like DUB-1, the DUB-2 protein had deubiquitinating activity in vitro. When a conserved cysteine residue of DUB-2, required for ubiquitin-specific thiol protease activity, was mutated to serine (C60S), deubiquitinating activity was abolished. DUB-1 and DUB-2 proteins are highly related throughout their primary amino acid sequence except for a hypervariable region at their COOH terminus. Moreover, the DUB genes co-localize to a region of mouse chromosome 7, suggesting that they arose by a tandem duplication of an ancestral DUB gene. Additional DUB genes co-localize to this region, suggesting a larger family of cytokine-inducible DUB enzymes. We propose that different cytokines induce specific DUB genes. Each induced DUB enzyme thereby regulates the degradation or the ubiquitination state of an unknown growth regulatory factor, resulting in a cytokine-specific growth response.

Chromosomal localization of HTLV-1 viral integration sites using in situ hybridization: detection of a novel IL2R fragment

The presence of human T-cell leukemia virus (HTLV-1) in patients with adult T-cell leukemia (ATL) was investigated by Southern blotting and in situ hybridization. In all seven patients, HTLV-1 provirus was detected. A large and variable number of labeled restriction fragments were observed, indicating multiple integrations. Two of the patients analyzed by in situ hybridization had two, while the third patient had three, sites of viral integration on six different chromosomes, suggesting random integration. A single site of integration was shared by two patients, which was on chromosome 10 at bands p11-->p15. One of these sites was on an apparently normal chromosome 10 and the other was on a derivative chromosome 10,t(10;14)(p12;q32). The interleukin 2 receptor (IL2R) has previously been localized to this region (10p14-->p15). The alpha-chain of the IL2R is continuously expressed on affected T-cells in this disease. Southern blotting with pIL2R showed the presence of a novel 3.5 kb fragment in five out of the seven patients. This novel fragment has not been previously reported. No direct correlation was found between the novel 3.5 kb fragment, present in patients both cytogenetically normal and abnormal, and viral integration in the 10p11-->p15 region in two patients. Therefore, it is suggested that the presence of the 3.5 kb fragment and the numerous chromosomal breaks associated with this disease may not be direct results of viral integration.

Molecular involvement of the pvt-1 locus in a gamma/delta T-cell leukemia bearing a variant t(8;14)(q24;q11) translocation

A highly malignant human T-cell receptor (TCR) gamma/delta+ T-cell leukemia was shown to have a productive rearrangement of the TCR delta locus on one chromosome 14 and a novel t(8;14)(q24;q11) rearrangement involving the J delta 1 gene segment on the other chromosome 14. Chromosome walking coupled with pulsed-field gel electrophoretic (PFGE) analysis determined that the TCR J delta 1 gene fragment of the involved chromosome was relocated approximately 280 kb downstream of the c-myc proto-oncogene locus found on chromosome band 8q24. This rearrangement was reminiscent of the Burkitt's lymphoma variants that translocate to a region identified as the pvt-1 locus. Sequence comparison of the breakpoint junctions of interchromosomal rearrangements in T-cell leukemias involving the TCR delta-chain locus revealed novel signal-like sequence motifs, GCAGA(A/T)C and CCCA(C/G)GAC. These sequences were found on chromosome 8 at the 5' flanking site of the breakpoint junction of chromosome 8 in the TCR gamma/delta leukemic cells reported here and also on chromosome 1 in T-cell acute lymphocytic leukemia patients carrying the t(1;14)(p32;q11) rearrangement. These results suggest that (i) during early stages of gamma delta T-cell ontogeny, the region 280 kb 3' of the c-myc proto-oncogene on chromosome 8 is fragile and accessible to the lymphoid recombination machinery and (ii) rearrangements to both 8q24 and 1p32 may be governed by novel sequence motifs and be subject to common enzymatic mechanisms.

Molecular involvement of the pvt-1 locus in a gamma/delta T-cell leukemia bearing a variant t(8;14)(q24;q11) translocation

A highly malignant human T-cell receptor (TCR) gamma/delta+ T-cell leukemia was shown to have a productive rearrangement of the TCR delta locus on one chromosome 14 and a novel t(8;14)(q24;q11) rearrangement involving the J delta 1 gene segment on the other chromosome 14. Chromosome walking coupled with pulsed-field gel electrophoretic (PFGE) analysis determined that the TCR J delta 1 gene fragment of the involved chromosome was relocated approximately 280 kb downstream of the c-myc proto-oncogene locus found on chromosome band 8q24. This rearrangement was reminiscent of the Burkitt's lymphoma variants that translocate to a region identified as the pvt-1 locus. Sequence comparison of the breakpoint junctions of interchromosomal rearrangements in T-cell leukemias involving the TCR delta-chain locus revealed novel signal-like sequence motifs, GCAGA(A/T)C and CCCA(C/G)GAC. These sequences were found on chromosome 8 at the 5' flanking site of the breakpoint junction of chromosome 8 in the TCR gamma/delta leukemic cells reported here and also on chromosome 1 in T-cell acute lymphocytic leukemia patients carrying the t(1;14)(p32;q11) rearrangement. These results suggest that (i) during early stages of gamma delta T-cell ontogeny, the region 280 kb 3' of the c-myc proto-oncogene on chromosome 8 is fragile and accessible to the lymphoid recombination machinery and (ii) rearrangements to both 8q24 and 1p32 may be governed by novel sequence motifs and be subject to common enzymatic mechanisms.

T-cell acute lymphoblastic leukemia with t(11;14) in children

We review and update our examination of the clinical and biologic findings in 19 cases of acute lymphoblastic leukemia (ALL) with the t(11;14) and discuss the literature relevant to the clinical, biologic, and molecular aspects of these translocations. In nine consecutively diagnosed cases at St. Jude Children's Research Hospital and 10 cases reported by other institutions, clinical features did not differ among T-cell ALL patients with and without the t(11;14), although leukemic cells with this translocation were more likely to coexpress CD4 and CD8 antigens. The t(11;14)(p13;q11) appears to occur exclusively in T-cell malignancies of intermediate- or late-stage thymocyte differentiation; further studies will be needed to determine whether it has prognostic significance.

Localization of the human angiogenin gene to chromosome band 14q11, proximal to the T cell receptor alpha/delta locus

The gene encoding angiogenin, a potent inducer of blood vessel formation, has been localized within the human genome. It is present as a single copy per haploid genome and is located on chromosome 14, on the basis of discordancy analysis of human-rodent hybrid cell lines. This localization was refined to 14q11 by in situ hybridization of an angiogenin probe to metaphase chromosomes prepared from both normal human lymphocytes and RPMI 8402 cells. The results from the RPMI 8402 cells also establish that the angiogenin gene resides proximal to a translocation breakpoint within the T cell receptor alpha/delta locus and therefore upstream from that locus. An AvaII RFLP, present at a frequency of 29% in an unselected collection of human placental DNAs, was identified in the coding region of the gene and results from a single silent transversion.

A newly established human acute lymphoblastic leukemia cell line with characteristics of the earliest B-cell maturation

A new human acute lymphoblastic leukemia (ALL) cell line, designated HBL-3, was established from the bone marrow of a patient with non-T-ALL. The HBL-3 cell line expressed B4 (CD 19), BA-1 (CD 24) and HLA-DR antigens, but not surface immunoglobulin (SIg) or cytoplasmic immunoglobulin (CIg). The cell line lacked the common acute lymphoblastic leukemia antigen (CALLA) and antigenic markers characteristic of T-cell and myeloid cell lineages. The HBL-3 cells had structural rearrangements of both the homologous chromosome 9s, including a translocation with chromosome 1 which has been reported in a patient with common ALL. The cell line had rearranged immunoglobulin heavy chain genes but retained germ-line kappa light chain genes and germ-line T-cell receptor beta- and gamma-chain genes. The HBL-3 cell line was strongly positive for terminal deoxynucleotidyl transferase (TdT). These findings indicate that the HBL-3 cell line is derived from the earliest B-cell committed to B-cell lineage.

An (8;14)(q24;q11) translocation involving the T-cell receptor alpha-chain gene and the MYC oncogene 3' region in a B-cell lymphoma

We describe a t(8;14)(q24;q11) involving the T-cell receptor alpha-chain gene (TCRA) and the 3' region of the MYC protooncogene in a B-cell lymphoma. The B-cell origin of this tumor was determined by its histological architecture, by immunophenotypic analysis, and by Southern analysis of immunoglobulin gene rearrangements. An identical fragment encompassing the translocation breakpoint junction was detected through Southern analysis using both a TCRAJ and a MYC probe. The other alleles at the TCRAJ and MYC loci were in the germline configuration. Restriction enzyme and nucleotide sequencing analyses revealed that the breakpoint junction on chromosome 8 lies approximately 700 base pairs (bp) downstream of the 3' end of the third MYC exon; on chromosome 14, the break is located 12.6 kilobases (kb) downstream of the 3' end of the C delta fourth exon. A heptamer-like consensus sequence on chromosome 14 adjacent to the translocation breakpoint implies the involvement of recombinase activity. However, no consensus sequences were found on chromosome 8 within 140 bp in either direction from the breakpoint. It is possible that this translocation involving MYC occurred during an attempt at an inappropriate rearrangement of the TCRA locus in a cell of B-cell lineage.

Molecular cloning of the translocation breakpoint in T-ALL 11;14 (p13;q11): genomic map of TCR alpha and delta region on chromosome 14q11 and long-range map of region 11p13

Using chromosome walking techniques, overlapping lambda and cosmid clones from the T cell receptor alpha (TCR alpha) region have been isolated; these span the entire J alpha region and parts of the TCR delta gene. Molecular analysis of the acute childhood leukemia cells (T-ALL) 8511 revealed a rearrangement on one chromosome 14 in J alpha 58 kb 5' of C alpha; this does not result in production of alpha message. The translocation was identified 90 kb 5' of C alpha at the previously identified J delta 2 element. A probe derived from the 5' region of the translocation breakpoint hybridized to DNA from a mouse-human cell hybrid containing chromosome 11 as the only human chromosome. This probe was used to isolate cosmid clones from chromosome 11. Several rare cutting restriction enzyme sites were found in close vicinity to the translocation breakpoint, and a long-range map spanning 1000 kb of chromosome region 11p13 was established. Analysis of the DNA from 15 cases of sporadic and familial Wilms' tumor did not reveal any changes, indicating that the translocation breakpoint does not reside in this gene.

Genetic and cytogenetic changes in acute lymphoblastic leukemia

In recent years, a number of non-random chromosomal alterations have been identified in specific populations of acute lymphoblastic leukemic cells of either B-cell or T-cell lineage. The most frequently involved chromosomal sites are 1q, 4q, 6q, 7q, 8q, 9p, 9q, 10q, 11p, 12p, 14q, 19p and 22q. Genes located near frequent breakpoints include c-myc, c-abl and the genes for the T-cell alpha and beta receptors. In addition, approximately 20 other genes potentially involved in the leukemic process are located near less frequently encountered, but consistent, chromosomal breakpoints.

Breakage of the T cell receptor alpha chain locus in non malignant clones from patients with ataxia telangiectasia

Patients with ataxia telangiectasia (A-T) develop specific chromosome translocations, which may confer a proliferative advantage, resulting in the appearance of large clones in the peripheral blood lymphocytes. These lymphocytes are not malignant. Using in situ hybridisation techniques we have investigated a consistent 14q11 translocation breakpoint observed in a t(X;14)(q28;q11) translocation clone from each of two different patients and a t(14;14)(q11;q32) clone from a third patient. In all cases the chromosome translocation involved breakage within the alpha chain locus of the T cell receptor (TCR alpha), between the variable and constant regions, at 14q11. Chromosome rearrangement involving breakage within TCR alpha can therefore precede the development of malignancy. Further chromosomal rearrangement may be required in these patients, for progression to the leukaemic state.

Structure and rearrangement of the T cell receptor J alpha locus in T cells and leukemic T cell lines

The vast majority of T cells express an antigen receptor (TcR) composed of an alpha/beta heterodimer. The alpha and beta chains are encoded for by a set of variable (V), joining (J) and constant (C) region genes. Unlike the J genes of the beta chain which are limited in number and are clustered close to the constant region, the J alpha genes are spread over an 85-kilobase DNA region, upstream of the C alpha gene. We have isolated the complete J alpha locus, bounded on the 5' side by the C sequence of the delta gene and on the 3' side by the C sequence of the alpha gene. The experiments described here demonstrate that the J gene segments extend 75 kb 5' of C alpha and participate equally in generating the diversity of the alpha chain in peripheral T cells. Similarly, in leukemic T cell lines, rearrangements occurred over the entire locus and involved both alleles. Densitometry data suggest that in most peripheral T cells both alleles also are rearranged; thus, allelic exclusion in the alpha locus does not occur at the level of rearrangement. In three cell lines, an identical rearrangement has occurred on one allele in a region located 10 kb from the 5' end of the locus.

Complex rearrangements within the human J delta-C delta/J alpha-C alpha locus and aberrant recombination between J alpha segments

We have examined DNA rearrangements within a 120 kb cloned region of the human T cell receptor J delta-C delta/J alpha-C alpha locus. Three types of pattern emerge from an analysis of T cell lines and clones. Firstly, cells with two rearrangements within J delta-C delta; secondly, cells with one rearrangement within J delta-C delta and one or more J alpha rearrangements, and finally, cells with rearrangements within J alpha and consequential deletion of the delta locus. Further analysis by cloning of rearrangements within the J alpha locus show that, in addition to V alpha-J alpha joins, J alpha-J alpha aberrant recombinations occur and rearrangement data indicate that such events are frequent. A model is presented to account for such recombinations.

T-cell acute childhood lymphoblastic leukemia with chromosome 14 q 11 anomaly: a morphologic, immunologic, and cytogenetic analysis of 10 patients

Ten patients with T-cell acute lymphoblastic leukemia (ALL) and a chromosome anomaly involving band 14 q 11 are described. Mitotic index of bone marrow blasts was high in all patients (average 3.0%). Lymphoid morphology of the leukemic blasts, however, varied somewhat among the patients. The leukemic cells of 5 patients showed an immunophenotypic profile corresponding to early or common thymic differentiation stages whereas 5 children showed strong expression of CD 3 suggesting a more mature thymic phenotype. Leukemic karyotypes revealed a modal chromosome number of 46 in 9 cases, 92 in one case. A chromosome translocation t(11; 14) (p 13; q 11) was found in 5 cases, a t(1; 14) (p 32; q 11) in 2 cases, a t(10; 14) (q 24; q 11) in one case, a (hitherto undescribed) t(12; 14) (q 22; q 11) in one case, and an inv (14) (q 11 q 32) in one patient. Additional abnormalities were t(3; 10), t(7; 9), dup(7 q), del(6 q), del(10 q), and del(1 q). Of 32 cases with T-cell ALL successfully karyotyped in our laboratory 15 (= 47%) had structural aberrations involving chromosomes 1, 3, 6, 7, 9, 10, 12, 14. Ten of these 15 patients (= 67%) had a chromosome 14 q 11 anomaly. It is concluded that chromosome band 14 q 11, the gene locus of the T-cell receptor alpha-chain, is the most common site for structural chromosome aberrations in T-cell ALL.