Molecular characterization of ataxia telangiectasia T cell clones. II. The clonal inv(14) in ataxia telangiectasia differs from the inv(14) in T cell lymphoma

Inversion (14)(q11q32) in childhood T-cell acute lymphoblastic leukemia

Inversion (14)(q11q32) is a common cytogenetic aberration in T-cell chronic lymphoid malignancies but is rare in T-cell acute lymphoblastic leukemia (T-ALL). We describe two cases of childhood T-ALL in which inv(14)(q11q32) was present concomitantly with other karyotypic aberrations typical of T-ALL. The possible significance of inv(14) in these cases is also discussed.

Cytogenetic analysis in ataxia telangiectasia with malignant lymphoma

We present the results of cytogenetic analysis in a brother and sister with ataxia telangiectasia (AT), one of whom had malignant T-cell lymphoma. In both children, cytogenetic analysis of phytohemagglutinin (PHA)-stimulated lymphocytes showed chromosomal instability and inv(7) in 10% of the cells examined. The malignant lymphoma was analyzed cytogenetically on slides obtained from short-term culture of the lymph node cells; 64 cells were analyzed. A heterogeneous cell population was noted. Fourteen cells (21.9%) had a normal male karyotype; t(7;14)(p14;q12) and inv(7)(p14q35) were observed in 6.3% and 3.1% of metaphases. Owing to low frequency, these cells are probably a characteristic of the basic disease and have no features of malignant cells. Forty cells (62.5%) had a pseudodiploid karyotype 46,XY,dup(1)(p22p36),del(5)(q33),del(12)(p11), without cytogenetically evident aberrations of chromosomes 7 and 14. The results of these investigations suggest that the cells with rearrangements of chromosomes 1, 5, and 12 are malignant cells and did not originate by transformation of cells with inv(7) and t(7;14).

Inv(14) with distal breakpoint in 14q32.1 in three cases of T cell lymphoma

The distal breakpoint of inv(14) in T cell clones, established from patients with ataxia telangiectasia, lies outside the immunoglobulin heavy chain gene locus on 14q32.3, and more proximal to the centromere than the distal breakpoint of inv(14) in the T cell lymphoma cell line SUP-T1. We report 3 cases of T cell lymphoma cytogenetically showing the same type of inv(14) as the AT T cell clones. All 3 cases express a similar immunophenotype, which is that of peripheral T lymphocytes with phenotypic remnants of thymic or postthymic lymphoblasts. This finding provides evidence that this type of inv(14) is involved in the malignant transformation of mature T lymphocytes.

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.

Molecular characterization of ataxia telangiectasia T cell clones. III. Mapping the 14q32.1 distal breakpoint

To delimit the 14q32.1 recurrent breakpoint of ataxia telangiectasia clones, we performed an in situ hybridization study with various probes located on the 14q32 band. We thus mapped this breakpoint between the D14S1 and Pi loci. Furthermore, an interstitial duplication including D14S1 and a part of the IgH locus was demonstrated on a t(14;14) clone.