Immunoglobulin and T-cell receptor gene rearrangement and expression in human lymphoid leukemia cells at different stages of maturation.

The use of probes to genes (IG and TCRB) encoding immunoglobulins (IG) and the beta chain of the T-cell antigen receptor (TCRB), respectively, have become a sensitive means to assess clonality and lineage in lymphoid malignancies. It has become apparent that some individual cases show rearrangements of both IG and TCRB genes. In an attempt to more accurately define cell lineage we have analyzed cells from patients with B- or T-cell leukemia (n = 26) at various stages of maturation with probes to two additional TCR genes, TCRG and TCRA (encoding the TCR gamma and alpha chains, respectively), as well as the IG heavy chain joining region (IGHJ) and TCRB genes. On Southern blot analysis, the mature T-cell leukemia cells studied had rearranged TCRG and TCRB while IGHJ remained as in the germ line. The mature B-cell leukemia cells studied had rearranged IGHJ with germ-line TCRG and TCRB. These data suggest that, in the majority of more mature leukemias, cells have rearranged IG or TCR genes but not both. In contrast, cells from five of nine precursor B-cell leukemia patients and cell lines from one of four precursor T-cell leukemia patients had rearranged both IGHJ and TCR genes. TCRG and TCRB mRNAs were expressed in the cells of precursor T- but not B-cell leukemia patients studied. The spectrum of leukemia cells studied within the T-cell series permitted an assessment of the order of TCR gene rearrangements. Two of 13 patients had cells with germ-line TCRG and TCRB, 2 patients had cells with rearranged TCRG alone, and the remainder had cells with rearranged TCRG and TCRB. TCRG and TCRB mRNAs were expressed in precursor T-cell leukemia cells, whereas TCRB and TCRA were expressed in mature T-cell leukemia cells. These results parallel observations from mouse studies on gene expression and support the view of a hierarchy of TCR gene rearrangements in T-lymphocyte ontogeny. TCRG genes are rearranged first, subsequently TCRB genes are rearranged, followed by TCRA gene activation.     

T-cell prolymphocytic leukaemia: antigen receptor gene rearrangement and a novel mode of MTCP1 B1 activation

T-cell prolymphocytic leukaemia (T-PLL) is a sporadic, mature T-cell disorder in which there is usually an aberrant T-cell receptor alpha (TCRA) rearrangement that activates the TCL1 or MTCP1-B1 oncogenes. As mutations of the Ataxia Telangiectasia (A-T) gene, ATM, are frequent in T-PLL and as ATM seems to act as a tumour suppressor through a mechanism involving V(D)J recombination, we examined V(D)J recombination in T-PLL. Using Southern blotting and the polymerase chain reaction, two of 60 TCRG coding joints were abnormal. In all cases, both TCRD alleles were deleted, IGH was germline, and patterns of TCRB and TCRA rearrangement were normal. However, in a case harbouring t(X;7)(q28;q35), we identified TCRB segment J beta 2.7 juxtaposed to MTCP1 exon 1. This is the first time that TCRB has been implicated in MTCP1 B1 activation. The structure of the breakpoint supports a model in which translocation activates a cryptic MTCP1 promoter. This analysis of V(D)J recombination is consistent with it being a variable that is independent of ATM in T-PLL.     

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

Chromosomal rearrangements in malignant T-cell disease frequently involve the chromosome bands containing the T-cell receptor genes. The RPMI 8402 cell line, which was established from the leukemia cells of a patient with T-cell acute lymphoblastic leukemia, is characterized by a translocation involving chromosome 14 (band q11) and chromosome 11 (band p15) [t(11;14)(p15;q11)]. By using in situ chromosomal hybridization and Southern blot analysis to examine RPMI 8402 cells, we determined that the break at 14q11 occurs within the variable region sequences of the T-cell receptor alpha-chain gene (TCRA); the break at 11p15 occurs between the HRAS1 gene and the genes for insulin and the insulin-like growth factor 2. These results suggest that the TCRA sequences activate a cellular gene located at 11p15 in malignant T-cell disorders.     

Molecular analysis of TCRB and ABL in a t(7;9)-containing cell line (SUP-T3) from a human T-cell leukemia.

A translocation between chromosomes 7 and 9, t(7;9), has been described in cell lines derived from the malignant cells of children with acute T-cell lymphoblastic leukemia or lymphoma. Our cytogenetic analysis of one such cell line, SUP-T3, demonstrates that the breakpoints on chromosomes 7 and 9 lie within bands q36 and q34, respectively, corresponding to the location of the gene encoding the beta chain of the T-cell receptor, TCRB, and the gene homologous to the transforming gene of the Abelson murine leukemia virus, ABL. We investigated the role of these genes in the t(7;9). In situ chromosomal hybridization of TCRB and ABL probes to metaphase cells from SUP-T3 demonstrated that ABL is translocated from chromosome 9 to 7 and that all or part of TCRB is translocated from chromosome 7 to 9. Southern blot analysis revealed that both TCRB alleles were rearranged; however, it could not be determined whether the translocation breakpoint lies within this gene. Pulsed-field gel electrophoresis and Southern blot analysis were used to examine more than 500 kilobases of the ABL locus; we concluded that there are no rearrangements within 250 kb in either direction of the sequences homologous to v-abl. Additionally, no abnormal ABL protein was detected in an in vitro phosphorylation assay. These results indicate that, in SUP-T3, the breakpoint on chromosome 9 lies proximal to ABL and that the break results in no apparent alteration of the ABL protein. We therefore hypothesize that another gene on chromosome 9, at band q34, plays a role in this translocation. This study also demonstrates that pulsed-field gel electrophoresis is a powerful new tool for the analysis of human chromosomal translocations.     

Alpha-chain locus of the T-cell antigen receptor is involved in the t(10;14) chromosome translocation of T-cell acute lymphocytic leukemia.

Human leukemic T cells carrying a t(10;14)(q24;q11) chromosome translocation were fused with mouse leukemic T cells, and the hybrids were examined for genetic markers of human chromosomes 10 and 14. Hybrids containing the human 10q+ chromosome had the human genes for terminal deoxynucleotidyltransferase that has been mapped at 10q23-q25 and for C alpha [the constant region of TCRA (the alpha-chain locus of the T-cell antigen receptor gene)], but not for V alpha (the variable region of TCRA). Hybrids containing the human 14q- chromosome retained the V alpha genes. Thus the 14q11 breakpoint in the t(10;14) chromosome translocation directly involves TCRA, splitting the locus in a region between the V alpha and the C alpha genes. These results suggest that the translocation of the C alpha locus to a putative cellular protooncogene located proximal to the breakpoint at 10q24, for which we propose the name TCL3, results in its deregulation, leading to T-cell leukemia. Since hybrids with the 10q+ chromosome also retained the human terminal deoxynucleotidyltransferase gene, it is further concluded that the terminal deoxynucleotidyltransferase locus is proximal to the TCL3 gene, at band 10q23-q24.     

Juxtaposition of the T-cell receptor alpha-chain locus (14q11) and a region (14q32) of potential importance in leukemogenesis by a 14;14 translocation in a patient with T-cell chronic lymphocytic leukemia and ataxia-telangiectasia.

We describe a t(14;14)(q11;q32) translocation in a patient with T-cell chronic lymphocytic leukemia and ataxia-telangiectasia (AT). By using a battery of joining (J)-segment probes from the T-cell receptor (TCR) alpha-chain locus TCRA, three distinct J alpha rearrangements were observed. One rearrangement reflected a normal TCRA variable (V) region V alpha-to-J alpha recombination. The second rearrangement was caused by the translocation even itself, which joined a DNA segment from 14q32 centromeric to the immunoglobulin heavy chain locus (IGH) and a J alpha gene located approximately 75 kilobases (kb) 5' of the TCRA constant region gene (C alpha). A third rearrangement involved a 17-kb internal deletion 3' to the translocation, a rearrangement within the J alpha locus that has been observed once before in a patient with AT. Analysis of these three rearrangements underscores the increase in aberrant locus-specific recombination in lymphocytes from patients with AT. Furthermore, these studies support the view that a growth-effecting gene is present in the 14q32 region that participates in the leukemogenic process.     

c-tal, a helix-loop-helix protein, is juxtaposed to the T-cell receptor- beta chain gene by a reciprocal chromosomal translocation: t(1;7)(p32;q35)

Studies on nonrandom chromosomal translocations have been important for the identification of genes potentially involved in the malignant transformation of cells. The most widely studied translocations, involving members of the Ig supergene family, have shown juxtapositions of proto-oncogenes with the rearranging loci. Such translocations can inappropriately activate expression of the proto-oncogenes and thereby play a role in tumorigenesis. Because the cytogenetic analysis of a bone marrow sample from a child with T-cell acute lymphoblastic leukemia showed a (1;7)(p32;q35) translocation, we sought to determine if the translocation breakpoint was in the T-cell receptor (TCR)-beta gene locus on chromosome 7. Analysis of the TCR-beta gene by Southern blotting showed three rearranged bands. Nucleotide sequencing and Southern blot analysis of TCR-beta genomic clones, isolated from patient DNA, showed that one contained a normal rearrangement of the TCR-beta gene using V beta 12.2, D beta 2.1, and J beta 2.5, whereas two other clones contained DNA from derivative chromosomes 1 and 7. Chromosomal mapping showed that the (1;7) translocation breakpoint was 35 kb 3' to the c-tal gene locus. The juxtaposition of c-tal to the TCR- beta locus may enhance c-tal expression and contribute to T-cell leukemogenesis.     

Translocations of 14q32 and deletions of 13q14 are common chromosomal abnormalities in systemic amyloidosis

Systemic monoclonal immunoglobulin light chain amyloidosis (AL) is associated with clonal plasma cell dyscrasias that are often subtle and non-proliferating. AL shares numerical chromosomal changes with multiple myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS). Illegitimate translocations involving the immunoglobulin heavy chain gene (IGH) at 14q32 and deletions of the long arm of chromosome 13, [del(13q)], commonly occur in MM, MGUS and plasma cell leukaemia. In AL IGH rearrangements have been identified but, to date, there are no reports of del(13q). In this study of 32 patients with AL, 24 with systemic and eight with localized disease, translocations involving IGH and del(13q) were found using dual-colour interphase fluorescence in situ hybridization (FISH). IGH translocations were observed in 11 patients (37% overall and in 46% with systemic disease), of which nine had the IGH/CCND1 fusion from t(11;14)(q13;q32). Two showed IGH translocations other than the t(11;14) or t(4;14)(p16;q32). In one of these patients a breakpoint within the constant region of IGH between Calpha1 and Calpha2 was indicated. In the second a deletion covering Calpha1 and Calpha2 accompanied the translocation. Ten patients (27% overall and 33% of those with systemic disease) showed del(13q). The gain or loss of IGH and CCND1 signals provided evidence of numerical chromosomal changes in three patients.     

The BCL11 gene family: involvement of BCL11A in lymphoid malignancies.

Many malignancies of mature B cells are characterized by chromosomal translocations involving the immunoglobulin heavy chain (IGH) locus on chromosome 14q32.3 and result in deregulated expression of the translocated oncogene. t(2;14)(p13;q32.3) is a rare event in B-cell malignancies. In contrast, gains and amplifications of the same region of chromosome 2p13 have been reported in 20% of extranodal B-cell non-Hodgkin lymphomas (B-NHL), in follicular and mediastinal B-NHL, and in Hodgkin disease (HD). It has been suggested that REL, an NF-kappaB gene family member, mapping within the amplified region, is the pathologic target. However, by molecular cloning of t(2;14)(p13;q32.3) from 3 cases of aggressive B-cell chronic lymphocytic leukemia (CLL)/immunocytoma, this study has shown clustered breakpoints on chromosome 2p13 immediately upstream of a CpG island located about 300 kb telomeric of REL. This CpG island was associated with a Krüppel zinc finger gene (BCL11A), which is normally expressed at high levels only in fetal brain and in germinal center B-cells. There were 3 major RNA isoforms of BCL11A, differing in the number of carboxy-terminal zinc fingers. All 3 RNA isoforms were deregulated as a consequence of t(2;14)(p13;q32.3). BCL11A was highly conserved, being 95% identical to mouse, chicken, and Xenopus homologues. BCL11A was also highly homologous to another gene (BCL11B) on chromosome 14q32.1. BCL11A coamplified with REL in B-NHL cases and HD lymphoma cell lines with gains and amplifications of 2p13, suggesting that BCL11A may be involved in lymphoid malignancies through either chromosomal translocation or amplification.     

Clinical and biologic features of childhood T-cell leukemia with the t(11;14)

Cytogenetic analysis of cells from 622 consecutive patients with newly diagnosed acute lymphoblastic leukemia (ALL) and successful G-banding chromosome studies disclosed seven cases with the t(11;14)(p13;q11) and one with the t(11;14)(p15;q11). Leukemia cells in all eight cases had a T-cell immunophenotype. The t(11;14)(p13;q11) occurred in 6.8% and the t(11;14)(p15;q11) in 1% of T-cell ALL cases (n = 103). The t(11;14) was associated with presenting clinical features typical of T-cell ALL: male predominance (n = 6), age greater than 10 years (n = 3), hyperleukocytosis (white blood cells greater than 100 x 10(9)/L, n = 5), relatively high hemoglobin level (median, 10.8 g/dL), high serum lactic dehydrogenase level (median, 3248 U/L), presence of mediastinal mass (n = 6), and central nervous system leukemia (n = 2). While there were no significant differences in presenting features between T-cell ALL cases with or without the t(11;14), leukemic cells from patients with the translocations were more likely to coexpress CD4 and CD8 antigens (6 of 6 v 35 of 86 cases tested, P less than .05). Adverse events have occurred in six patients: three central nervous system relapses [including the one with t(11;14)(p15;q11)], two secondary acute myeloid leukemia, and one hematologic relapse. Our results indicate that the t(11;14)(p13;q11) occurs exclusively in T-cell malignancies of intermediate- or late-stage thymocyte differentiation. Additional studies are needed to determine the prognostic implications of these translocations.     

Different chromosomal breakpoints impact the level of LMO2 expression in T-ALL

The t(11;14)(p13;q11) is presumed to arise from an erroneous T-cell receptor delta TCRD V(D)J recombination and to result in LMO2 activation. However, the mechanisms underlying this translocation and the resulting LMO2 activation are poorly defined. We performed combined in vivo, ex vivo, and in silico analyses on 9 new t(11;14)(p13;q11)-positive T-cell acute lymphoblastic leukemia (T-ALL) as well as normal thymocytes. Our data support the involvement of 2 distinct t(11;14)(p13;q11) V(D)J-related translocation mechanisms. We provide compelling evidence that removal of a negative regulatory element from the LMO2 locus, rather than juxtaposition to the TCRD enhancer, is the main determinant for LMO2 activation in the majority of t(11;14)(p13;q11) translocations. Furthermore, the position of the LMO2 breakpoints in T-ALL in the light of the occurrence of TCRD-LMO2 translocations in normal thymocytes points to a critical role for the exact breakpoint location in determining LMO2 activation levels and the consequent pressure for T-ALL development.     

Cytogenetic studies on prolymphocytic leukemia. II. T cell prolymphocytic leukemia

We report chromosome abnormalities in 15 cases of T cell prolymphocytic leukemia (T-PLL). All cases were characterized by clinical, morphological, and membrane marker analysis. The most frequent abnormality was an inv(14)(q11q32) observed in nine cases. The T cell receptor (TCR) alpha chain gene is localized to 14q11 and the immunoglobulin heavy-chain gene to region 14q32. Four cases also had translocations involving 14q11. Trisomy or multisomy for 8q resulting from an i(8q) or from rearrangements with 8p12 as the breakpoint was observed in nine cases, and a deletion of 6q was found in four cases. Trisomy or partial trisomy for 7q was observed in four cases, of which two had abnormalities of band 7q35 to which the TCR beta chain gene is mapped. The expression of Tac antigen, investigated in 27 cases of human T cell leukemia virus I-negative chronic T cell leukemia, which included the 15 cases of T-PLL, showed a good correlation with abnormalities of 7q35. Our studies on chronic T leukemias suggest that inv(14)(q11q32) and trisomy for 8q are abnormalities characteristic of T-PLL.     

TCL1 oncogene activation in preleukemic T cells from a case of ataxia- telangiectasia

The TCL1 oncogene on human chromosome 14q32.1 is involved in chromosome translocations [t(14;14)(q11;q32.1) and t(7;14)(q35;q32.1)] and inversions [inv14(q11;q32.1)] with TCR alpha/beta loci in T-cell leukemias, such as T-prolymphocytic (T-PLL). It is also involved in T- acute and -chronic leukemias arising in cases of ataxia-telangiectasia (AT), an immunodeficiency syndrome. Similar chromosomal rearrangements occur also in the clonally expanded T cells in AT patients before the appearance of the overt leukemia. We have analyzed the expression of TCL1 mRNA and protein in peripheral blood lymphocytes (PBLs) from four AT cases and from healthy controls. We found that the TCL1 gene was overexpressed in the PBLs of an AT patient with a large clonal T-cell population exhibiting the t(14;14) translocation but not in the lymphocytes of the other cases. Fluorescence in situ hybridization of the TCL1 genomic locus to lymphocyte metaphases from the AT patient with the T-cell clonal expansion showed that the breakpoint of the t(14;14) translocation lies within the TCL1 locus and is accompanied by an inverted duplication of the distal part of chromosome 14. These data indicate that TCL1 is activated in preleukemic clonal cells as a consequence of chromosome translocation involving sequences from the TCR locus at 14q11. Deregulation of TCL1 is the first event in the initiation of malignancy in these types of leukemias and represents a potential tool for clinical evaluation.     

A new case of acute lymphoblastic leukemia B-cell type with chromosomal rearrangements involving the T-cell receptor breakpoint at band 14q11.

A patient with B-cell acute lymphoblastic leukemia (ALL) and a translocation t(8;14) (q24;q11) is described. Translocation t(8;14)(q24;q32) is commonly associated with B-cell leukemia; nevertheless, translocations affecting chromosome 14 at band q11 are associated with T-cell malignancies, since the locus 14q11 contains genes that encode for the alpha and delta chains of the T-cell receptor (TCR). This finding points to the idea that the association between 14q11 rearrangements and T-cell neoplasia is less than complete.     

Molecular analysis of a t(14;14) translocation in leukemic T-cells of an ataxia telangiectasia patient.

We have detected and cloned two rearrangements in the T-cell receptor alpha locus from a clone of somatic cell hybrids carrying a t(14;14)(q11;q32) chromosomal translocation derived from an ataxia telangiectasia patient with T-cell chronic lymphocytic leukemia. The T-cell clone carrying the t(14;14) chromosomal translocation was known to be present for greater than 10 years before the onset of overt leukemia. One molecular rearrangement of the T-cell receptor alpha locus corresponded to a functional variable-joining region (V-J) joining, whereas the other derived from the breakpoint of the t(14;14)(q11;q32) translocation. Chromosomal in situ hybridization of the probe derived from the t(14;14) breakpoint localized the breakpoint region to 14q32.1, apparently the same region that is involved in another ataxia telangiectasia characteristic chromosome translocation, t(7;14)(q35;q32). The 14q32.1 breakpoint is at least 10,000 kilobase pairs (kbp) centromeric to the immunoglobulin heavy chain locus. Sequence analysis of the breakpoint indicates the involvement of a J alpha sequence during the translocation. Comigration of high-molecular weight DNA fragments involved with t(7;14) and t(14;14) translocations suggests the presence of a cluster of breakpoints in the 14q32.1 region, the site of a putative oncogene, TCL1.     

The breakpoint of an inversion of chromosome 14 in a T-cell leukemia: sequences downstream of the immunoglobulin heavy chain locus are implicated in tumorigenesis.

T-cell tumors are characterized by inversions or translocations of chromosome 14. The breakpoints of these karyotypic abnormalities occur in chromosome bands 14q11 and 14q32--the same bands in which the T-cell receptor (TCR) alpha-chain and immunoglobulin heavy chain genes have been mapped, respectively. Patients with ataxia-telangiectasia are particularly prone to development of T-cell chronic lymphocytic leukemia with such chromosomal abnormalities. We now describe DNA rearrangements of the TCR alpha-chain gene in an ataxia-telangiectasia-associated leukemia containing both a normal and an inverted chromosome 14. The normal chromosome 14 has undergone a productive join of TCR alpha-chain variable (V alpha) and joining (J alpha) gene segments. The other allele of the TCR alpha-chain gene features a DNA rearrangement, about 50 kilobases from the TCR alpha-chain constant (C alpha) gene, that represents the breakpoint of the chromosome 14 inversion; this breakpoint is comprised of a TCR J alpha segment (from 14q11) fused to sequences derived from 14q32 but on the centromeric side of C mu. These results imply that 14q32 sequences located at an undetermined distance downstream of the immunoglobulin C mu locus can contribute to the development of T-cell tumors.