Inversion of chromosome 14 marks human T-cell chronic lymphocytic leukaemia

From identification of the BTK kinase to effective management of leukemia

BTK is a cytoplasmic protein-tyrosine kinase, whose corresponding gene was isolated in the early 1990s. BTK was initially identified by positional cloning of the gene causing X-linked agammaglobulinemia and independently in a search for new kinases. Given the phenotype of affected patients, namely lack of B-lymphocytes and plasma cells with the ensuing inability to mount humoral immune responses, BTK inhibitors were anticipated to have beneficial effects on antibody-mediated pathologies, such as autoimmunity. In contrast to, for example, the SRC-family of cytoplasmic kinases, there was no obvious way in which structural alterations would yield constitutively active forms of BTK, and such mutations were also not found in leukemias or lymphomas. In 2007, the first efficient inhibitor, ibrutinib, was reported and soon became approved both in the United States and in Europe for the treatment of three B-cell malignancies, mantle cell lymphoma, chronic lymphocytic leukemia and Waldenström's macroglobulinemia. Over the past few years, additional inhibitors have been developed, with acalabrutinib being more selective, and recently demonstrating fewer clinical adverse effects. The antitumor mechanism is also not related to mutations in BTK. Instead tumor residency in lymphoid organs is inhibited, making these drugs highly versatile. BTK is one of the only 10 human kinases that carry a cysteine in the adenosine triphosphate-binding cleft. As this allows for covalent, irreversible inhibitor binding, it provides these compounds with a highly advantageous character. This quality may be crucial and bodes well for the future of BTK-modifying medicines, which have been estimated to reach annual multi-billion dollar sales in the future.

Relevance of Fusion Genes in Pediatric Cancers: Toward Precision Medicine

Pediatric cancers differ from adult tumors, especially by their very low mutational rate. Therefore, their etiology could be explained in part by other oncogenic mechanisms such as chromosomal rearrangements, supporting the possible implication of fusion genes in the development of pediatric cancers. Fusion genes result from chromosomal rearrangements leading to the juxtaposition of two genes. Consequently, an abnormal activation of one or both genes is observed. The detection of fusion genes has generated great interest in basic cancer research and in the clinical setting, since these genes can lead to better comprehension of the biological mechanisms of tumorigenesis and they can also be used as therapeutic targets and diagnostic or prognostic biomarkers. In this review, we discuss the molecular mechanisms of fusion genes and their particularities in pediatric cancers, as well as their relevance in murine models and in the clinical setting. We also point out the difficulties encountered in the discovery of fusion genes. Finally, we discuss future perspectives and priorities for finding new innovative therapies in childhood cancer.

Small cell variant of T-cell prolymphocytic leukemia with a gammadelta immunophenotype

T-cell prolymphocytic leukemia (T-PLL) is a rare postthymic T-cell disorder. The disease is characterized by lymphadenopathy, splenomegaly, skin lesions, a high white blood cell count, and an aggressive clinical course. The small cell variant of T-PLL occurs in approximately 20% of patients. Most T-PLL patients express membrane T-cell receptors (TCR) of the alphabeta phenotype. The diagnosis of small cell variant T-PLL in a 56-year-old woman was based on the findings of abnormal lymphocytosis, immunophenotype, lymphadenopathy, and aggressive clinical behavior. Immunophenotype analysis showed that lymphocytes were positive for CD2, CD3, CD5, CD7, CD8, and TCR gammadelta antigens and negative for CD1a, CD4, and TCR alphabeta antigens. Southern blot analysis revealed rearrangement of the TCR Jgamma and Jdelta-1 genes. A cytogenetic study of peripheral blood showed a normal karyotype. T-PLL with a TCR gammadelta phenotype is very rare. This case was typical T-PLL except for the morphologically small cell type and the lack of the typical chromosome aberration. If cases accumulate in the future, the specific features of the gamma8 type of T-PLL will become clearer.

T-cell prolymphocytic leukemia with hemorrhagic gastrointestinal involvement and a new chromosomal abnormality

We report a case of T-cell prolymphocytic leukemia in a 56-year-old woman who exhibited hemorrhaging with gastric involvement as the first manifestation. This patient's condition was diagnosed as T-cell prolymphocytic leukemia based on the findings of lymphocytosis, abnormal immunophenotype, hepatosplenomegaly, lymphadenopathy, and cutaneous involvement. Endoscopic examination of the upper gastrointestinal tract revealed hemorrhage from a gastric lesion with histological involvement. Cytogenetic analysis revealed chromosomal abnormalities, 46,XX,der(1), add(1)(p36), that have not previously been described in T-cell prolymphocytic leukemia. In spite of a transient response to chemotherapy, the patient died 15 months after onset of the disease.

Chromosomal abnormalities in T-cell large granular lymphocyte leukaemia: report of two cases and review of the literature

Cytogenetic information on T-cell large granular lymphocyte leukaemia (T-LGL; large granular lymphocytosis) is limited. We report two cases of T-LGL with unusual karyotypic aberrations. The first case showed a novel inv(7)(p15q22) as the sole chromosomal abnormality, while the second case showed an inv(14)(q11q32) with evidence of clonal evolution. The breakpoints 7p14-p15 and 14q11 coincide with the T-cell receptor (TCR)-gamma and TCR-alpha/TCR-delta gene loci respectively. This is the first report describing the possible involvement of T-cell receptor genes in karyotypic aberrations in T-LGL.

Mantle cell lymphoma is characterized by inactivation of the ATM gene

In mantle cell lymphoma (MCL), the translocation t(11;14) is considered the cytogenetic hallmark of the disease. Recently, however, deletion of the chromosomal region 11q22-q23 has been identified as a frequent event in this type of cancer, indicating the existence of a pathogenically relevant tumor suppressor gene in this region. The deleted segment contains the ATM (ataxia telangiectasia mutated) gene. ATM is an interesting candidate as a tumor suppressor gene because constitutive inactivation of the gene predisposes ataxia telangiectasia patients to lymphoid malignancies. To assess the potential involvement of the gene in MCL lymphomagenesis, we performed mutation analysis of ATM in 12 sporadic cases of MCL, 7 of them with a deletion of one ATM gene copy, by using single-strand conformation polymorphism analysis of reverse transcription-PCR-amplified mRNA and subsequent DNA sequencing. In all seven cases containing a deletion of one ATM allele, a point mutation in the remaining allele was detected, which resulted in aberrant transcript splicing, truncation, or alteration of the protein. In addition, biallelic ATM mutations were identified in two MCLs that did not contain 11q deletions. Interestingly, in three cases analyzed, the ATM mutations detected in the tumor cells were not present in nonmalignant cells, demonstrating their somatic rather than germ-line origin. The inactivation of both alleles of the ATM gene by deletion and deleterious point mutation in the majority of cases analyzed indicates that ATM plays a role in the initiation and/or progression of MCL.

Crystal structure of p14TCL1, an oncogene product involved in T-cell prolymphocytic leukemia, reveals a novel beta-barrel topology

BACKGROUND

Chromosome rearrangements are frequently involved in the generation of hematopoietic tumors. One type of T-cell leukemia, T-cell prolymphocytic leukemia, is consistently associated with chromosome rearrangements characterized by the juxtaposition of the TCRA locus on chromosome 14q11 and either the TCL1 gene on 14q32.1 or the MTCP1 gene on Xq28. The TCL1 gene is preferentially expressed in cells of early lymphoid lineage; its product is a 14 kDa protein (p14TCL1), expressed in the cytoplasm. p14TCL1 has strong sequence similarity with one product of the MTCP1 gene, p13MTCP1 (41% identical and 61% similar). The functions of the TCL1 and MTCP1 genes are not known yet. They have no sequence similarity to any other published sequence, including those of well-documented oncogene families responsible for leukemia. In order to gain a more fundamental insight into the role of this particular class of oncogenes, we have determined the three-dimensional structure of p14TCL1.

RESULTS

The crystal structure of p14TCL1 has been determined at 2.5 A resolution. The structure was solved by molecular replacement using the solution structure of p13MTCP1, revealing p14TCL1 to be an all-beta protein consisting of an eight-stranded antiparallel beta barrel with a novel topology. The barrel consists of two four-stranded beta-meander motifs, related by a twofold axis and connected by a long loop. This internal pseudo-twofold symmetry was not expected on basis of the sequence alone, but structure-based sequence analysis of the two motifs shows that they are related. The structures of p13MTCP1 and p14TCL1 are very similar, diverging only in regions that are either flexible and/or involved in crystal packing. p14TCL1 forms a tight crystallographic dimer, probably corresponding to the 28 kDa species identified in solution by gel filtration experiments.

CONCLUSIONS

Structural similarities between p14TCL1 and p13MTCP1 suggest that their (unknown) function may be analogous. This is confirmed by the fact that these proteins are implicated in analogous diseases. Their structure does not show similarity to other oncoproteins of known structure, confirming their classification as a novel class of oncoproteins.

Biallelic mutations in the ATM gene in T-prolymphocytic leukemia

Ataxia-telangiectasia (AT) is an autosomal recessive disorder characterized by cerebellar ataxia, oculocutaneous telangiectasia, immune deficiency, genome instability and predisposition to malignancies, particularly T-cell neoplasms. The responsible gene, designated ataxia-telangiectasia mutated (ATM), was recently identified by positional cloning in the chromosomal region 11q22.3-23.1 (ref. 4, 5) ATM is 150 kb in length, consists of 66 exons and encodes a nuclear phosphoprotein of approximately 350 kDa (ref. 4-9). Although ATM is considered to be a tumorigenic factor in several human cancers, it has not yet been found mutated in tumors of non-AT patients. Given the marked predisposition of AT patients to develop neoplasms of the T-cell lineage, we analyzed a series of T-cell leukemias (T-prolymphocytic leukemia, or T-PLL) in non-AT patients in search of genomic changes associated with the development of this disease. Among the recurrent aberrations identified, deletion of the chromosome arm 11q was very frequent. Subsequent molecular cytogenetic analyses allowed us to define a small commonly deleted segment at 11q22.3-23.1 in 15 of 24 T-PLLs studied. Since this critical region contained ATM, we further analyzed the remaining copy of the gene in six cases showing deletions affecting one ATM allele. In all six cases, mutations of the second ATM allele were identified, leading to the absence, premature truncation or alteration of the ATM gene product. Thus, our study demonstrates disruption of both ATM alleles by deletion or point mutation in T-PLL, suggesting that ATM functions as a tumor-suppressor gene in tumors of non-AT individuals.

Biclonal B-cell chronic lymphocytic leukemia with inv(14)(q11q32)

Cytogenetic biclonality is a rare occurrence in chronic lymphocytic leukemia. A 59-year-old man was diagnosed to have B-cell chronic lymphocytic leukemia with typical morphology and immunophenotype (CD5+, CD19+, and CD23+). However, karyotypic analysis of the small lymphocytes showed the presence of two distinct unrelated clones, including one with inv(14).

Classification of peripheral T-cell lymphomas: cytogenetic findings support the updated Kiel classification

The cytogenetic findings in peripheral T-cell lymphomas enabled us to distinguish not only between low and high grade peripheral T-cell lymphomas (PTL) but also between different morphologically defined subtypes. High grade lymphomas exhibited a higher frequency of aberrant clones, polyploid chromosome numbers, a higher complexity of aberrant clones and a lower proportion of normal metaphases than low grade PTL. Moreover, deletions in 6q, trisomies of 7q and monosomy 13 or changes of 13q14 were significantly more frequent in high grade than in low grade PTL. Translocation t(2;5)(p23;q35) was only seen in large cell anaplastic lymphoma. T-CLL/T-PLL was associated with the simultaneous presence of inversion inv(14)(q11q32.l) and trisomy 8q, mostly due to i(8q)(q10). Trisomy 3 was a characteristic chromosome aberration of lymphoepithelioid lymphoma, AILD-type T-cell lymphoma and T-zone lymphoma. In contrast to the other low grade PTL, AILD-type T-ceIl lymphoma and cutaneous T-cell lymphoma showed a high frequency of unrelated clones. In summary, the cytogenetic findings paralleled the histopathologic classification according to the updated Kiel classification and support the value of the distinction of the different morphologically defined entities.

Inversion 14q in acute lymphoblastic leukemia of B-lineage

Many types of leukemia are associated with specific chromosomal rearrangements. Inversion 14(q11q32) has been reported to be specifically associated with post-thymic T-cell malignancies, including T-chronic lymphocytic leukemia. T-prolymphocytic leukemia, and adult T-cell leukemia/lymphoma. We have previously reported its occurrence in T-cell acute lymphoblastic leukemia. Recently, we encountered a case of acute lymphoblastic leukemia with inv(14)(q11q32), which surprisingly showed a B-cell immunophenotype (CD10+CD19+HLA-DR+Ig mu-).

Recurrent chromosome abnormalities in peripheral T-cell lymphomas

Cytogenetic findings in 45 cases of peripheral T-cell lymphomas (PTL) diagnosed according to the updated Kiel classification are reported. Recurrent numerical chromosome aberrations comprised -X, -Y, -13, +X, +3, +5 and +7. Recurrent structural aberrations included t/del(1)(p31-32), t(2;5)(p23;q35), dup(5)(q23q31-32), t/dup(6q), t/del(6q), trisomy 7q, and trisomy 8q, mostly due to i(8)(q10), and changes in 14q11 and 14q32.1, mostly due to inv(14)(q11q32.1), t/del(13)(q14), t(6;7)(q13;q13), and t(13;17)(q11-13;p11). All deletions in 6q involved band 6q21 and all partial trisomies of 7q led to an amplification of band 7q21. Further studies are needed to ascertain whether these cytogenetic findings in PTL are of clinical and prognostic significance.

Multiple karyotypic abnormalities in three cases of small cell variant of T-cell prolymphocytic leukemia

Cytogenetic, clinical, and laboratory findings of three patients with a small cell variant of T-cell prolymphocytic leukemia (T-PLL) are presented. Immunophenotypic studies of the morphologically typical small cell variant prolymphocytes showed a mature helper T-cell phenotype (CD4+CD8-) in one patient and a common thymocyte phenotype (CD4+ CD8+) in two other patients. The cytogenetic analysis revealed complex karyotypes with several structural aberrations in the peripheral blood lymphocytes of all three patients. In all cases chromosome 14 was affected with the breakpoint at 14q11. Inversion (14) and isochromosome 8q, often reported as an additional aberration in T-PLL, were detected in two of the patients. In two patients a translocation of the short arm of chromosome 12 was also seen. The T-cell receptor beta-chain gene showed a clonal rearrangement in all three patients, whereas no rearrangements were detected in the immunoglobulin genes. The survival of the patients ranged from 10 weeks to 48 months. The association between cytogenetic, clinical, and laboratory data is discussed.

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.

Cytogenetics in CLL and related disorders

Chromosome analysis of more than 1200 patients with chronic lymphocytic leukaemia reported to the International Working Party on Chromosomes in CLL and in the literature is analysed. Clonal chromosomal abnormalities are found in about half of the patients, and one third of those with clonal aberrations have trisomy 12, with or without additional changes. The most common structural abnormalities involve the long arm of chromosome 13, usually as deletions involving 13q14, the site of the retinoblastoma gene. Other recurrent abnormalities are deletions of the long arms of chromosome 11 and 6. 14q+ markers are frequent in patients at advanced stage, but are almost always within complex abnormalities. The number of clonal abnormalities in the CLL cells has a strong prognostic impact. Trisomy 12 as a single abnormality is an adverse prognostic sign, whereas patients with 13q abnormalities generally do comparatively well. Lymphoid leukaemia with monoclonal immunoglobulin secretion frequently involves clonal chromosomal abnormalities, and the type of change is similar to that seen in true CLL. In B cell prolymphocytic leukaemia, t(11;14) is a common finding, together with trisomy 12. T cell prolymphocytic leukaemia is characterized by an inversion of the long arm of chromosome 14, with breaks at q11 and q32, and trisomy of 8q, whereas large granular lymphocytic leukaemia has shown no consistent abnormality. Hairy cell leukaemia seems to involve a specific set of non-random chromosome abnormalities, such as inv(5)9.

Establishment and characterization of a human T-cell lymphoblastic lymphoma cell line (HT-1) carrying an inversion of chromosome 14

A new human lymphoblastic lymphoma cell line was established (designated HT-1) from the pleural fluid lymphoma cells of a patient with lymphoblastic lymphoma of T-cell type. The HT-1 cells expressed CD1, CD2, CD3, CD4, CD5, CD7, CD8, CD57, and terminal deoxynucleotidyl transferase (TdT) but lacked B-cell-associated antigens and myeloid-associated antigens. In addition, HT-1 cells had rearranged T-cell receptor (TCR) beta-chain gene and gamma-chain gene but retained germlines of immunoglobulin (Ig) heavy chain gene. These findings indicate that HT-1 cell line represents a common thymocyte in the T-cell lineage. Cytogenetic studies revealed that HT-1 cells carry an inversion (inv) of the long arm of chromosome 14. This cell line is the second T-cell line carrying inv(14) chromosome and may be useful for the molecular investigation of the cytogenetic break points of inv(14).

Cytogenetic implication in adult T-cell leukemia. A hypothesis of leukemogenesis

The close association between adult T-cell leukemia (ATL) and human T-cell leukemia virus type I (HTLV-I) has been established. Nevertheless, the mechanism of progression of ATL by HTLV-I infection is still uncertain, because the virus contains no typical oncogene and no significant expression of the viral RNA has been generally found. I propose a model of leukemogenic process in ATL based on our cytogenetic data and molecular results in the literature. It seems that the rearrangement of some proto-oncogene and alpha-chain gene of the T-cell antigen receptor (TCR-alpha) is necessary for the development to overt ATL. A deficiency in the rearrangement of proto-oncogene to TCR-alpha may result in only a minor proliferation of abnormal lymphocytes and remain in the preleukemic state of ATL or in the HTLV-I carrier state.

Stepwise development of chromosomal abnormalities in angioimmunoblastic lymphadenopathy

Cytogenetic studies of lymphoproliferative diseases, such as angioimmunoblastic lymphadenopathy (AILD), may provide a clue to the understanding of tumor development. Angioimmunoblastic lymphadenopathy may evolve from a nonmalignant lymphoproliferation into a peripheral T-cell lymphoma or even into a high-grade B-cell lymphoma and thus offers the chance to observe cytogenetic changes during lymphoma development. We report the cytogenetic findings in 24 cases of AILD. They are discussed together with 18 previously published cases from the same series. A striking feature was that unrelated chromosome abnormalities, both clonal and nonclonal, were frequently observed. Eighteen of 25 cases with aberrant clones show trisomy 3 (a characteristic chromosome abnormality in peripheral T-cell lymphoma), trisomy 5, or both. This finding provides cytogenetic evidence that these cases are definitely peripheral T-cell lymphomas. From the results of the 42 cases, hypotheses of stepwise evolution of the chromosome abnormalities in AILD are deduced: the first step is the appearance of chromosome abnormalities in different cells because of a genetic instability. At this time, clonal proliferation of T cells was already demonstrated by the rearrangement of T-cell receptor genes. As a second step, chromosomally aberrant clones become established. A cytogenetically detectable monoclonal proliferation represents the third step.

Chromosomal abnormality limited to T4 lymphocytes in a patient with T-cell chronic lymphocytic leukaemia

Cytogenetic, immunologic and DNA studies were performed on a patient with the T-cell type of chronic lymphocytic leukaemia. Standard G-banding karyotype analysis revealed clonal chromosome abnormalities with the karyotype 42-44,XY,-11,-12,-13,-16,-21,-22,i(8q),inv(14) (q11q32), t(15;?)(p11;?), +4-6mar/43-44,X,t(Y;14)(p11;q11),-11,-12, -13,-21,-22,i(6p),i(8q),inv(14)(q11q32),t(15;?)(q11;?), +1-3mar. MAC (morphology, antibody, chromosomes) methodology, which allows the immunophenotyping of mitotic cells, showed that the chromosome abnormalities were restricted to CD4-positive helper/inducer T lymphocytes and that CD8 suppressor/cytotoxic T cells and B lymphocytes possessed a normal karyotype. The results also indicate that the proportion of abnormal metaphases and the overall mitotic activity after 3.5 days of stimulation in vitro were highest when PHA and TPA were used as mitogens. When the culture period in the presence of PHA + IL-2 was extended, the proportion of the abnormal cell population decreased in direct relation to the length of the culture period, ranging from 100% at 3.5 d to 0% at 31 d after stimulation. Southern blotting analysis revealed rearrangements of both the immunoglobulin heavy chain gene and the beta T-cell receptor gene.

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.

Clonal chromosomal changes in chronic lymphocytic leukemia

Cytogenetic analysis was carried out in 28 B-CLL patients (21 males and 7 females, 38-85 years old, with median age 64 years, disease stage O-IV). Peripheral nominator cells (1 x 10(7)) or isolated B-lymphocytes were incubated in vitro for 5-7 days. The cells were stimulated by pokeweed mitogen (PWM), or phorbol myristate-acetate (PMA), with or without 10% conditioned medium (CM) derived from a T cell leukemia line or 10% B-cell growth factor (BCGF). Twenty-two patients (79%) responded to PWM + CM; 5 out of 5 patients responded to PWM + BCGF. The average mitotic index (+/- S.E.M.) for PWM, PMA, PWM + CM, PMA + CM, PWM + BCGF were 0.13 +/- 0.01, 0.24 +/- 0.13, 0.51 +/- 0.11, 0.14 +/- 0.06 and 0.63 +/- 0.15, respectively. Cytogenetic analysis revealed the presence of abnormal karyotypes in 22 patients. Fourteen patients (50%) had clonal chromosome aberrations which included: monosomy 1, 9, 17, 18, 21, and X chromosome, and trisomy of chromosomes 7, 9, 20, 21 and 22. The clonal structural aberrations were i(6q), inv(12) (q15q24), del(5) (p13p15), del(10) (q24). No homogeneously staining regions (HSR) were observed. Four patients with resistance to anti-neoplastic drugs showed the presence of double minute chromosomes (dmin) ranging in frequency from 5 to 50%.

Inv(14)(q11q32) in one of four different clones in a case of angioimmunoblastic lymphadenopathy

A case of angioimmunoblastic lymphadenopathy with dysproteinemia (AILD) with four cytogenetically different cell clones (49,XX,+5,+19,+21/47,XX,+X/46,XX,inv (14)(q11q32)/45,X,-X) is reported. To our knowledge, this is the first case of AILD with an inv(14)(q11q32), thus probably involving the T-cell receptor alpha-chain gene. The cytogenetic findings are discussed with respect to the possible progression of AILD to malignant lymphoma.

T-cell receptor gene rearrangements and the diagnosis of human T-cell neoplasms

The rearranging antigen receptor genes of lymphoid cells serve as unique clonal markers of lymphoid neoplasms. Gene rearrangement analysis is a highly sensitive and reproducible tool which is useful in the diagnosis and classification of malignant lymphoma/leukemia. Although clonality can often be determined among B cell neoplasms by virtue of immunoglobulin isotype analysis, no such phenotypic marker of clonality exists for T cells. Therefore, clonality of T lymphoproliferative processes is most readily determined by rearrangement analysis of the T cell antigen receptor genes. The alpha, beta, gamma, and delta genes of the T cell receptor gene family encode heterodimeric surface antigen receptors and undergo rearrangement early in T cell differentiation. Identification of rearrangement of T cell antigen receptor genes provides valuable diagnostic information concerning cellular lineage, clonality and classification of T cell neoplasms. This molecular approach is applicable to the diagnosis of occult disease, relapse, and resolution of diagnostic dilemmas in any type of tissue sample including fluids and needle aspirations.

Characterization of the breakpoint of a t(14;14)(q11.2;q32) from the leukemic cells of a patient with T-cell acute lymphoblastic leukemia

The leukemic cells and derivative cell line from a 74-year-old male with T-cell acute lymphoblastic leukemia showed chromosomal abnormalities including a t(14;14)(q11.2;q32). This translocation is characteristic of a variety of T-cell malignancies, particularly T-cell prolymphocytic leukemia and the clonal proliferations of peripheral T cells in patients with ataxia-telangiectasia. Using DNA probes that spanned the T-cell receptor alpha chain (TCRA) joining (J) locus, the DNA rearrangement caused by the translocation was identified, cloned, and sequenced. The breakpoint shows site-specific juxtaposition of a TCRA joining segment and DNA from a region of 14q32 centromeric to the immunoglobulin heavy chain locus. Comparison of restriction map and nucleotide sequence from this translocation with other related chromosomal breakpoints suggests a dispersion of breakpoints throughout the 14q32 region.

Tissue specificity of chromosomal rearrangements in ataxia-telangiectasia

Cytogenetic studies of lymphocytes and fibroblasts from individuals with ataxia-telangiectasia (AT) demonstrate spontaneous chromosomal breakage. In the AT lymphocytes, this damage results in a high frequency of balanced rearrangements involving chromosome bands 7p14, 7q35, 14q12, and 14q32. The T-cell receptor alpha, beta, and gamma chain gene complexes and the immunoglobulin heavy chain gene complex, all of which may be functional in lymphocytes, have been localized to these bands. To assess the relationship between genes at these breakpoints and the entirety of the AT phenotype, we undertook a detailed cytogenetic analysis of fibroblasts and lymphocytes from seven AT homozygotes. Our findings indicate that the rearrangements present in the lymphocytes are not commonly observed in the fibroblasts, despite the increased instability of chromosomes from the cells relative to lymphocytes. Furthermore, the changes in the fibroblasts are neither consistent within nor between patients, suggesting that chromosome rearrangement occurs more randomly in this tissue. Therefore, differential site-specific damage in separate tissue may generate the distinct features of the disease in those tissues and may account for the pleiotrophic effects of the AT gene.

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.

Clonotypic chromosomal aberrations in long-term lines of myelin-specific rat T lymphocytes

A panel of 16 long-term rat T lymphocyte lines and clones were screened for cytogenetical abnormalities using chromosomal banding techniques. All T lines were CD4+, recognizing the relevant antigen in the molecular context of major histocompatibility complex (MHC) class II determinants. With one exception (an ovalbumin-specific line), all lines were specific for myelin proteins, and apart of one BS rat-derived T line and its clones, all lines were selected from the Lewis strain of rat. After in vitro culture of more than 1 year, all lines and clones exhibited subtle but definite chromosomal aberrations, which included deletions, enlargement, translocations and formation of isochromosomes. All lines were near diploid, structural chromosomal changes being more frequent than numerical abnormalities. Each T line investigated had an individual pattern of chromosomal changes. In our analysis, 16 of the 22 different chromosomes had changes in at least one line. Chromosome 9 and the X chromosome appeared to have an enhanced susceptibility of alterations. In two cases, chromosomal markers could be traced through different stages of in vitro culture of the T lines.

Appearance of a transient inv(14)(q11q32) in a case of B cell chronic lymphocytic leukemia

The inv(14)(q11q32) has been reported to be a specific chromosome aberration in T-cell chronic lymphocytic leukemia (T-CLL) and different types of T-cell lymphomas. Here, the first case of B-CLL with a clonal inv(14)(q11q32) in a phytohemagglutinin-stimulated bone marrow culture is presented. In a subsequent study 9 months later, tetradecanoyl-o-phorbol-13-acetate stimulated blood and bone marrow cultures revealed a clone with a t(1;11)(p13.2;q23.1) and an aberrant chromosome 17.

Clustering of breakpoints on chromosome 10 in acute T-cell leukemias with the t(10;14) chromosome translocation

The T-cell receptor (TCR) alpha/delta chain locus on chromosome 14q11 is nonrandomly involved in translocations and inversions in human T-cell neoplasms. We have analyzed three acute T-lymphoblastic leukemia samples carrying a t(10;14)(q24;q11) chromosome translocation by means of somatic cell hybrids and molecular cloning. In all cases studied the translocation splits the TCR delta chain locus. Somatic cell hybrids containing the human 10q+ chromosome resulting from the translocation retain the human terminal deoxynucleotidyltransferase gene mapped at 10q23-q24 and the diversity and joining, D delta 2-J delta 1, regions of the TCR delta chain, but not the V alpha region (variable region of the TCR alpha chain), demonstrating that the split occurred within the V alpha-D delta 2 region. Molecular cloning of the breakpoint junctions revealed that the TCR delta chain sequences involved are made from the D delta 2 segment. The chromosome breakpoints are clustered within a region of approximately 263 base pairs of chromosome 10. The results suggest that the translocation of the TCR delta chain locus to a locus on 10q, which we have designated TCL3, results in deregulation of this putative oncogene, leading to acute T-cell leukemia.

Acute nonlymphocytic leukemia in a patient with a constitutional inv(4)

We describe a case of acute nonlymphocytic leukemia (ANLL) in a patient with a constitutional chromosome anomaly, inv(4)(p16q26). The patient had extensive occupational exposure to toxic chemicals. Reports of constitutional or acquired chromosome inversions in human malignancies are quite uncommon. The constitutional changes associated with hematologic malignancies include trisomy 21, balanced translocations, deletions, and sex chromosome anomalies. The breakpoints on chromosome 4 in our case are 4p16, to which the murine leukemia viral (v-raf) oncogene, pseudogene 1, has been mapped, and 4q26, which is the locus of the IL-2 gene. Activation of these genes could have played a role in the pathogenesis of the patient's leukemia.

Nucleotide sequence of both reciprocal translocation junction regions in a patient with Ph positive acute lymphoblastic leukaemia, with a breakpoint within the first intron of the BCR gene

Breakpoints on chromosome 22 in the translocation t(9;22) found in Philadelphia positive acute lymphoblastic leukaemia patients fall within two categories. In the first the breakpoint is localized within the breakpoint cluster region of the BCR gene, analogous to the chromosome 22 breakpoint in chronic myeloid leukaemia. The second category has a breakpoint 5' of this area, but still within the BCR gene. We have previously shown that these breakpoints occur within the first intron of the BCR gene and cloned the 9q+ junction from such a patient. We have now determined the sequences around the breakpoints on both translocation partners from this patient as well as the germline regions. The chromosome 9 ABL sequence around the breakpoint shows homology to the consensus Alu sequence whereas the chromosome 22 BCR sequence does not. At the junction there is a 6 bp duplication of the chromosome 22 sequence which is present both in the 9q+ and in the 22q- translocation products. Possible mechanisms for the generation of the translocation are discussed.

Cytogenetic studies on the adult T-cell leukemia in Japan

Cytogenetic studies were performed on 16 patients with ATL seen in Northern Kyushu island; nine were patients with acute type leukemia, one with crisis type and five with lymphoma type. The serum antibody for HTLV-1 (ATLA) was positive in all patients and the phenotype of ATL cells were ERFC+, OKT3+, OKT4+, OKT6-, OKT8-, OKT10+, OKla1+/- and Tac+. Abnormal findings of chromosomes were observed in 15 patients. Thirteen patients were in near diploid range. One patient was in triploid range and one patient was in tetraploid range. The polyploid karyotypes were found only in lymphoma type patients. Trisomy 3 and trisomy 7 were observed each in three patients with acute type of ATL. The most frequent abnormal rearrangement was observed in the long arm of chromosome 6 and the break occurred at band 6q15 and 6q21 each in four patients in this series.

Inversion (4)(p13q28) in two cases of acute nonlymphocytic leukemia

An identical inversion, inv(4)(p13q28), was found to occur as the sole karyotypic anomaly in two patients with acute nonlymphocytic leukemia. The breakpoints are different from any previously described structural rearrangements of chromosome 4.

Cytogenetic study of chronic lymphocytic leukemia in ten Japanese patients with a case of the same chromosome abnormality both in T and B cells

Peripheral blood lymphocytes from ten patients with chronic lymphocytic leukemia (CLL) stimulated with phytohemagglutinin (PHA), pokeweed mitogen (PWM), Epstein-Barr virus (EBV), and T-cell growth factor were studied cytogenetically. Eight of ten cases were clinically and immunologically B-cell CLL, and two cases were T-cell CLL. Chromosome analysis revealed that one patient, diagnosed as B-cell CLL, had a clonal abnormality in the leukemic cells. The abnormal karyotype was 46,XY,+3,-15,t(10;19)(q22;p13),t(11;14) (q13;q32),13q+,17q-. The frequencies of the abnormal cell stimulated with PHA, PWM, and EBV were 50%, 13%, and 100%, respectively. Finding the same clonal abnormality after stimulation with three different mitogens suggests that the factor responsible for the development of CLL might affect the stem cell common to T-cell and B-cell lymphocytes. In cells with this abnormal karyotype, chromosome 13q+ seems to have a homogeneous staining region. In the present series of B-cell CLL, no trisomy 12 known to be the specific chromosome abnormality was observed.

Cytogenetic characterization of a T-cell line, ATN-1, derived from adult T-cell leukemia cells

A T-cell line, ATN-1, was established by culturing peripheral blood mononuclear cells derived from a patient with adult T-cell leukemia/lymphoma (ATL/L). Identities of the patterns of chromosomal abnormalities, cell surface phenotypes, morphologic findings, rearrangement patterns of T-cell receptor beta chain gene, and an integration site of human T-cell leukemia virus I proviral genome indicated that ATN-1 was derived from original leukemic cells. Both ATN-1 and the original leukemic cells showed a variety of patterns of chromosomal abnormalities that include 3q-, 6q-, rearrangements involving 2q31, 7q11.2, 8q11, 8q24, 19p13.3, and also 14q11 and 14q32, where genes for the T-cell receptor alpha chain and the immunoglobulin heavy chain are located. Availability of a genuine ATL/L cell line with these chromosomal abnormalities may greatly facilitate the biologic analysis of ATL/L.

The cytogenetics of childhood leukemia: clinical and biologic implications

Cytogenetic studies have revealed a broad spectrum of abnormalities in the chromosomal make-up of human leukemic cells. These abnormalities are acquired during the process of malignant transformation within the neoplastic clone and reflect the genetic lesions and ablations that have occurred. Because cytogenetic abnormalities are tightly linked to the molecular events that lead to leukemogenesis, it is not surprising that these features correlate with immunophenotypic and morphologic features of the leukemic cells, as well as with the clinical characteristics of children at diagnosis and their responsiveness to therapy. Molecular analysis of the disordered structure or disrupted regulation of genes located at critical chromosomal breakpoints in leukemic cells should continue to provide important insight into normal and aberrant hematopoietic cell function.