Comparison of T cell receptor alpha, beta, and gamma gene rearrangement and expression in T cell acute lymphoblastic leukemia

Therapeutic targeting of LCK tyrosine kinase and mTOR signaling in T-cell acute lymphoblastic leukemia

Relapse and refractory T-cell acute lymphoblastic leukemia (T-ALL) has a poor prognosis, and new combination therapies are sorely needed. Here, we used an ex vivo high-throughput screening platform to identify drug combinations that kill zebrafish T-ALL and then validated top drug combinations for preclinical efficacy in human disease. This work uncovered potent drug synergies between AKT/mTORC1 (mammalian target of rapamycin complex 1) inhibitors and the general tyrosine kinase inhibitor dasatinib. Importantly, these same drug combinations effectively killed a subset of relapse and dexamethasone-resistant zebrafish T-ALL. Clinical trials are currently underway using the combination of mTORC1 inhibitor temsirolimus and dasatinib in other pediatric cancer indications, leading us to prioritize this therapy for preclinical testing. This combination effectively curbed T-ALL growth in human cell lines and primary human T-ALL and was well tolerated and effective in suppressing leukemia growth in patient-derived xenografts (PDX) grown in mice. Mechanistically, dasatinib inhibited phosphorylation and activation of the lymphocyte-specific protein tyrosine kinase (LCK) to blunt the T-cell receptor (TCR) signaling pathway, and when complexed with mTORC1 inhibition, induced potent T-ALL cell killing through reducing MCL-1 protein expression. In total, our work uncovered unexpected roles for the LCK kinase and its regulation of downstream TCR signaling in suppressing apoptosis and driving continued leukemia growth. Analysis of a wide array of primary human T-ALLs and PDXs grown in mice suggest that combination of temsirolimus and dasatinib treatment will be efficacious for a large fraction of human T-ALLs.

PRL3 enhances T-cell acute lymphoblastic leukemia growth through suppressing T-cell signaling pathways and apoptosis

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy of thymocytes and is largely driven by the NOTCH/MYC pathway. Yet, additional oncogenic drivers are required for transformation. Here, we identify protein tyrosine phosphatase type 4 A3 (PRL3) as a collaborating oncogenic driver in T-ALL. PRL3 is expressed in a large fraction of primary human T-ALLs and is commonly co-amplified with MYC. PRL3 also synergized with MYC to initiate early-onset ALL in transgenic zebrafish and was required for human T-ALL growth and maintenance. Mass spectrometry phosphoproteomic analysis and mechanistic studies uncovered that PRL3 suppresses downstream T cell phosphorylation signaling pathways, including those modulated by VAV1, and subsequently suppresses apoptosis in leukemia cells. Taken together, our studies have identified new roles for PRL3 as a collaborating oncogenic driver in human T-ALL and suggest that therapeutic targeting of the PRL3 phosphatase will likely be a useful treatment strategy for T-ALL.

The integrin LFA-1 signals through ZAP-70 to regulate expression of high-affinity LFA-1 on T lymphocytes

The integrin lymphocyte function-associated antigen 1 (LFA-1) controls many functions of T lymphocytes and is particularly essential during lymphocyte migration from blood into tissues. LFA-1 is considered to initiate "outside-in" signaling when bound to ligand intercellular adhesion molecule 1 (ICAM-1), but little is known about the proteins involved or where in the cell such LFA-1-mediated signaling might be operating. Here we show that LFA-1 is constitutively associated with the protein tyrosine kinases Lck and zeta chain-associated protein of 70 kDa (ZAP-70). When LFA-1 binds ICAM-1, both kinases become phosphorylated and the consequence of kinase activation is the conversion of intermediate- to high-affinity LFA-1 and an increase in close contact with ICAM-1. In the polarized T lymphocyte, phospho-ZAP-70 is concentrated within a region of high-affinity LFA-1 that includes talin and encompasses the lamella/lamellipodial interface as well as further back in the cell. Deficiency of ZAP-70 through inhibition or knockdown in T lymphocytes decreases the speed of migration on ICAM-1, as well as reducing firm adhesion under shear-flow conditions. Through its control of high-affinity LFA-1, the LFA-1/Lck/ZAP-70 complex is in position to initiate the rapid adhesion strengthening and migration necessary for T-lymphocyte responses when stimulated vasculature is encountered at sites of infection or injury.

Calpain 2 controls turnover of LFA-1 adhesions on migrating T lymphocytes

The immune cells named T lymphocytes circulate around the body fulfilling their role in immunosurveillance by monitoring the tissues for injury or infection. To migrate from the blood into the tissues, they make use of the integrin LFA-1 which is exclusively expressed by immune cells. These highly motile cells attach and migrate on substrates expressing the LFA-1 ligand ICAM-1. The molecular events signaling LFA-1 activation and adhesion are now reasonably well identified, but the process of detaching LFA-1 adhesions is less understood. The cysteine protease calpain is involved in turnover of integrin-mediated adhesions in less motile cell types. In this study we have explored the involvement of calpain in turnover of LFA-1-mediated adhesions of T lymphocytes. Using live cell imaging and immunohistochemistry, we demonstrate that turnover of adhesions depends on the Ca2+-dependent enzyme, calpain 2. Inhibition of calpain activity by means of siRNA silencing or pharmacological inhibition results in inefficient disassembly of LFA-1 adhesions causing T lymphocyte elongation and shedding of LFA-1 clusters behind the migrating T lymphocytes. We show that calpain 2 is distributed throughout the T lymphocyte, but is most active at the trailing edge as detected by expression of its fluorescent substrate CMAC,t-BOC-Leu-Met. Extracellular Ca2+ entry is essential for the activity of calpain 2 that is constantly maintained as the T lymphocytes migrate. Use of T cells from a patient with mutation in ORAI1 revealed that the major calcium-release-activated-calcium channel is not the ion channel delivering the Ca2+. We propose a model whereby Ca2+ influx, potentially through stretch activated channels, is sufficient to activate calpain 2 at the trailing edge of a migrating T cell and this activity is essential for the turnover of LFA-1 adhesions.

Induction of galectin-1 expression by HTLV-I Tax and its impact on HTLV-I infectivity

Background

Cell-free Human T-cell Leukemia Virus type I (HTLV-I) virions are poorly infectious and cell-to-cell contact is often required to achieve infection. Other factors might thus importantly contribute in increasing infection by HTLV-I. Galectin-1 is a galactoside-binding lectin which is secreted by activated T lymphocytes. Several functions have been attributed to this protein including its capacity to increase cell-to-cell adhesion. Based on previous studies, we postulated that this protein could also accentuate HTLV-I infection.

Results

Herein, we demonstrate that galectin-1 expression and release are higher in HTLV-I-infected T cells in comparison to uninfected T cells. Furthermore, galectin-1 expression was activated in various cell lines expressing the wild type viral Tax protein while this induction was minimal upon expression of NF-κB activation-defective TaxM22. Cotransfection of these Tax expression vectors with galectin-1 promoter-driven luciferase constructs confirmed that Tax upregulated galectin-1 promoter activity. However, a NF-κB-independent mechanism was strongly favoured in this induction of galectin-1 expression as no activation of the promoter was apparent in Jurkat cells treated with known NF-κB activators. Using HTLV-I envelope pseudotyped HIV-1 virions, galectin-1 was shown to increase infectivity. In addition, a co-culture assay with HTLV-I-infected cells also indicated an increase in cell fusion upon addition of galectin-1. This effect was not mediated by factors present in the supernatant of the HTLV-I-infected cells.

Conclusion

These data suggest that HTLV-I Tax increases galectin-1 expression and that this modulation could play an important role in HTLV-I infection by stabilizing both cell-to-cell and virus-cell interactions.

Regulation of expression of matrix metalloproteinase-9 in early human T cells of the HSB.2 cultured line by the EP3 subtype of prostaglandin E2 receptor

The expression by T lymphocytes (T cells) of more than one of the functionally distinct subtypes of prostaglandin E2 (PGE2) receptors (Rs), designated EP1, EP2, EP3, and EP4 Rs, is a principal determinant of specificity and diversity of the immune effects of PGE2. The cultured line of human leukemic T cells, termed HSB.2, co-expresses a total of 7282 +/- 1805 EP3, EP4, and EP2 Rs per cell with a Kd of 3.7 +/- 1.4 nM (mean +/- S.E., n = 9). The EP3/EP1 R-selective agonist sulprostone, EP3/EP2/EP4 R-selective agonists M&B 28767 and misoprostol, and EP2 R-selective agonist butaprost but not the EP1 R-selective antagonist SC-19220 competitively inhibited the binding of [3H]PGE2 to HSB.2 cells. Stimulation of increases in the intracellular concentration of cyclic AMP ([cAMP]i) by PGE2, misoprostol, and butaprost and of increases in the intracellular concentration of calcium ([Ca2+]i) by PGE2 and sulprostone demonstrated the respective involvement of EP2/EP4 Rs and EP3 Rs in transduction of biochemical signals. Matrix metalloproteinase (MMP)-9 was identified by zymography and Western blots as the principal MMP secreted by HSB.2 cells. The cytosolic level and secretion of MMP-9 were increased maximally after 24 h of incubation of HSB.2 cells with 10(-8)-10(-6) M PGE2, sulprostone, M&B 28767, and misoprostol but not with 10(-6) M PGF2alpha, PGD2, PGI2, or butaprost, suggesting a principal dependence on EP3 Rs. That stimulation of MMP-9 secretion by PGE2 was not diminished in Ca2+-free medium but was suppressed significantly and dose-dependently by thapsigargin, an inhibitor of endomembrane Ca2+-ATPase, suggested that MMP-9 expression by HSB.2 cells is mediated by increases in [Ca2+]i attributable to release of Ca2+ from intracellular stores. The lack of effect of dibutyryl cAMP, forskolin, and SQ 22536, an adenylyl cyclase inhibitor, on MMP-9 secretion by HSB.2 cells argued against any role for cAMP-dependent mechanisms linked to EP2/EP4 Rs. Cycloheximide and actinomycin D, which respectively inhibited protein and RNA synthesis, suppressed basal and PGE2 induction of MMP-9 production by HSB.2 cells. Northern analysis indicated that PGE2 and sulprostone time-dependently increased expression of MMP-9 mRNA. Thus, stimulation of MMP-9 in HSB.2 T cells by PGE2 is attributable to [Ca2+]i-dependent EP3 R-mediation of increases in message transcription.

Glycosylphosphatidylinositol-anchored CD4 supports human immunodeficiency virus type 1 replication, but not cytopathic effect, in T-cell transfectants

Despite equivalent p24 antigen production, HSB-2 T cells expressing glycosylphosphatidylinositol (GPi)-linked CD4 were productively infected without cell death or syncytium formation, unlike HSB-2 transfectants expressing wild-type CD4 (wtCD4). HSB-2 transfectants dually expressing wtCD4 and GPi-linked CD4 formed syncytia and died. Thus, wtCD4 expression is critical for human immunodeficiency virus cytopathic effect in HSB-2 transfectants.

Molecular analysis of a t(11;14)(q23;q11) from a patient with null-cell acute lymphoblastic leukemia

/lp;&-3qChromosome 11, band q23, is the frequent site of recurring cytogenetic rearrangements in human leukemia. We have cloned and sequenced the breakpoint junctions from a patient who had null-cell acute lymphoblastic leukemia (ALL) with a t(11;14)(q23;q11). The chromosome 14 breakpoints occurred within the TCRD locus, close to two diversity segments. The chromosome 11 breakpoint occurred between two head-to-head heptamer sequences, and junctional diversity was evident at both derivative junctions, suggesting involvement of the V(D)J recombinase. The TCRA/D locus on the normal chromosome 14 had undergone a V delta 2-D delta 3-psi J alpha joining. Two phage clones with this VDJ rearrangement were isolated; one of these contained an intra-J alpha region deletion. Two clones with the derivative 11 junction were isolated; one of these had a similar, but not identical, deletion. A heptamer-nonamer recognition sequence (located approximately 70 kb 5' to C alpha), not associated with a TCR gene coding segment, was found in the immediate vicinity of both 5' breakpoints. We have designated this sequence 5'del for 5' deleting element. An intra-J alpha region deletion involving this heptamer-nonamer was previously identified in the leukemia cells recovered from a patient who had T-cell ALL. Fifty kilobases of DNA on 11q23 surrounding the breakpoint were cloned and analyzed. No CpG islands or conserved sequences were identified within this region.(ABSTRACT TRUNCATED AT 250 WORDS)

High level of surface CD4 prevents stable human immunodeficiency virus infection of T-cell transfectants

CD4 is the principal receptor for the human immunodeficiency virus (HIV). We have isolated and studied CD4-expressing tumor cell clones made by expressing CD4 in the T-cell tumor line HSB. Two clones, one designated HSBCD4, a clone expressing low levels of CD4, and the other, HSB10xCD4, a high-expresser CD4+ clone, were studied for their ability to bind and replicate HIV. In contrast to many other CD4+ cells that down-modulate CD4 following HIV infection, the HSB10xCD4 clones continued to express high levels of surface CD4 following infection with HIV. Unlike infection of HSBCD4 or many other human CD4+ cells, HIV infection of HSB10xCD4 clone was short lived: p24 antigen, provirus, or coculturable virus was present for less than 14 days following infection with several strains of HIV-1 or with HIV-2. When infection was initiated by transfection of proviral DNA, high and low CD4 expressers initially produced p24 antigen at approximately the same level. However, high CD4 expressers produced coculturable virus only during the first few days following transfection, whereas low CD4 expressers transfected with HIV continued to produce virus beyond 6 weeks. Monoclonal antibody-mediated down-modulation of CD4 surface expression on HSB10xCD4 clones permitted these formerly HIV-resistant cells to become persistently infected with HIV. Thus, high concentrations of CD4 on the surface of an HIV-infected cell prevent persistent HIV infection of CD4+ cells.

T-cell receptor alpha and delta gene assembly in B-cell precursor acute lymphoblastic leukemia

The status of the TCR-alpha/delta genes in B-precursor ALL and the rearrangement patterns of these gene loci are discussed in this review. Although most of these rearrangements have been characterized, some still remain to be clarified. Almost all rearrangements of the TCRs in B-precursor ALL are incomplete and may reflect early recombinational steps during the TCR differentiation processes in normal T-lineage cells. In addition, even in T-cell malignancies, it is rarely possible to obtain clonal cell populations with TCR rearrangements arrested in very early recombinational steps. Therefore, studies of these as yet uncharacterized rearrangements may lead to the discovery of additional gene segments playing important roles in the TCR recombinational processes and may provide useful information for understanding the processes of T-cell differentiation.

Acute undifferentiated leukemia with CD7+ and CD13+ immunophenotype. Lack of molecular lineage commitment and association with poor prognostic features

The authors studied six adult patients with acute leukemia with these unusual characteristics: unclassifiable morphology and undifferentiated cytochemistry by French-American-British (FAB) criteria; concurrent expression of CD13 (and CD33) myeloid and early T-cell CD7 immune markers; no evidence of T-cell lineage commitment as determined by T-cell receptor beta (beta), gamma (gamma), and delta (delta) chain gene rearrangement study and cytoplasmic CD3 epsilon expression; and no evidence of myeloid cell lineage commitment, as shown by absent myeloid-specific c-fms proto-oncogene expression and negative myeloperoxidase ultrastructural staining (one case). Clinically, these diagnostic features matched with a poor prognosis, being associated with refractoriness to treatment, relapse and progression of disease, antecedent hematologic abnormality, and other malignancy. These cases may represent a distinct stem cell leukemia syndrome deserving immediate recognition and a nonconventional chemotherapeutic approach.

Immune markers in hematologic malignancies

The precise delineation of biologic traits that distinguish normal hematopoietic cells from their malignant counterparts is of fundamental importance in understanding all aspects of hematologic malignancies. An increasingly sophisticated technologic battery has been utilized to dissect out these differences--primarily utilization of monoclonal antibodies, by immunoperoxidase, immunoalkaline phosphatase and flow cytometric techniques. An even more basic understanding of normal and malignant hematopoietic cells has begun to evolve as molecular biology begins to unravel gene misprogramming by Southern and Northern blot analysis and the polymerase chain reaction. These techniques not only help distinguish a normal cell from a malignant one, but characterize the malignant clone as B-lymphoid, T-lymphoid or myeloid and allow further subcategorization within these broad lineages. These distinctions are vital to the entire spectrum of basic and clinical research involving hematologic malignancies and are assuming an increasingly important role in their diagnosis, prognosis and treatment.

The LCK gene is involved in the t(1;7)(p34;q34) in the T-cell acute lymphoblastic leukemia derived cell line, HSB-2

HSB-2 is a cell line derived from a patient who had T-cell acute lymphoblastic leukemia (T-cell ALL) with a t(1;7)(p34;q34). We used a genomic probe from the T-cell receptor beta (TCR beta) locus (7q34) to identify DNA rearrangements in HSB-2. Two rearranged BglII DNA fragments were cloned, and one of these clones was shown to contain the translocation breakpoint on the derivative chromosome I [der(I)]. We used a probe derived from this clone to isolate an unrearranged phage clone encompassing the breakpoint at Ip34. The restriction map of this clone was compared to the published maps of known protooncogenes located at Ip32-34. By restriction mapping, Southern blot analysis, and DNA sequencing we showed that the translocation breakpoint on chromosome I is located within the first intron of the LCK gene. The LCK gene codes for p56lck, a member of the SRC family of cytoplasmic tyrosine protein kinases. There are two classes of LCK transcripts (type I and type II), each expressed from a distinct promoter, and each having a unique 5' untranslated region (UTR); the protein coding regions of the two classes are identical. The breakpoint in the t(1;7) separates the two LCK promoters and juxtaposes the constant region of the TCR beta locus with the proximal promoter and with the protein-coding region of the LCK gene on the der(I) chromosome.

Developmental process of the T-cell receptor alpha and delta gene assembly in B-cell precursor acute lymphoblastic leukaemia

We analysed the organization of V delta genes and delta recombining element (delta Rec) in 27 children with B-cell precursor acute lymphoblastic leukaemia. Twenty-two of 54 alleles showed rearrangements of the T-cell receptor (TCR) delta locus. These rearrangements resulted either from D2D delta 3 (2 alleles) or V delta 2(Dn)D delta 3 (20 alleles) recombinations, and the other V delta and delta Rec were not rearranged. Of 23 alleles with deletion of C delta and rearrangements of J alpha, V delta 2, V delta 4 and V delta 5 appeared to rearrange to J alpha on five alleles. With regard to the relationship between the rearranged V alpha/delta and J alpha genes, gene segments 5' to V delta 2 frequently rearranged to J alpha more proximal to C alpha, whereas V delta 2 and gene segments 3' to V delta 2 showed a tendency to rearrange to J alpha distal to C alpha. Based on these findings, we suggest that the initial recombination event of the TCR-alpha/delta gene may be D2D delta 3 joining, followed by V delta 2 recombination with the D2D delta 3 complex. It was also suggested that use of V alpha/delta and J alpha/delta may depend on the distance between the involved V alpha/delta and J alpha/delta at least in B-lineage cells. These rearrangements in B-precursor cells appear to be aberrant. However, this recombinational process may be one of the normal differentiation pathways in T-lineage cells, because cells with a V delta 2(Dn)D delta 3 rearrangement were detected in 0.1-0.01% of normal peripheral mononuclear cells by the polymerase chain reaction.

Rearrangement of T-cell Receptor (Delta, Gamma and Beta) Genes and its Significance in T-cell Chronic Leukaemias

The configuration of the delta, gamma and beta TCR genes and IgH genes was studied using appropriate DNA probes in 12 patients previously diagnosed as having T-cell chronic leukaemia. One or more TCR genes showed rearrangement and/or deletion in 11 patients, whereas rearrangement of IgH genes were seen in 3 patients only. TCR genes showed four distinct patterns: (a) rearrangement and/or deletion of each of the three TCR genes (7 patients), (b) re-arrangement of two TCR genes (3 patients), (c) rearrangement/deletion of one TCR gene only (1 patient), (d) germ-line state of all TCR genes (1 patient). These patterns had no demonstrable relationship with the clinical status either at the time of diagnosis or during the subsequent course of the disease. The findings provided unequivocal evidence of T-cell lineage of the leukaemic cells in 10 out of 12 patients. In one patient the lineage of leukaemic cells remained indeterminate. In the last patient the germ-line state of all TCR genes and rearrangement of both IgH alleles genes indicated that the leukaemia was of B-cell origin, even though the leukaemic cells had other features regarded as characteristic of T-lymphocytes. The different patterns of TCR genes, seen in the context of the hierarchical nature of the rearrangement process, suggest that the leukaemic transformation occurred at different stages of T-cell ontogeny and was followed by arrest of subsequent TCR gene rearrangement.

Constitutive expression of a groEL-related protein on the surface of human gamma/delta cells

Rabbit antibodies to hsp58 (P1), the human homologue of the Escherichia coli stress protein groEL, react specifically in indirect immunofluorescence and complement-dependent microcytoxicity experiments with a cell surface antigen expressed constitutively by T cell lines bearing gamma/delta receptors. This anti-hsp58-reactive antigen is not demonstrable on T cells that express alpha/beta receptors or on various cells that lack T cell receptors. Certain evidence was obtained to suggest that the target antigen on the surface of gamma/delta T cells is a approximately 77-kD protein distinct from intracellular hsp58 and known members of the hsp70 stress protein family. While the exact nature and significance of this anti-hsp58-reactive protein remain to be determined, these data may help to clarify the roles of groEL-related stress proteins and gamma/delta cells that recognize groEL homologous in immunologic defense against infection and in autoimmune disease.

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.

Adhesion molecules of cultured hematopoietic malignancies. A calcium-dependent lectin is the principle mediator of binding to the high endothelial venule of lymph nodes

This study documents that a calcium-dependent phosphomanosyl-binding site on human lymphoid malignancies mediates attachment to the peripheral node high endothelial venule (PNHEV). The phorbol ester PMA coordinately upregulates lectin activity and binding to the PNHEV in the human T-lymphoblastic cell line Jurkat but not in the less phenotypically mature lines HSB2, Molt4, CEM, and HPB-ALL. In contrast, expression of CD18, CD2, and several common epitopes of the putative adhesion receptor gp90Hermes (CD44) did not correlate with attachment to PNHEV in this series of cell lines. Insensitivity to inhibition by the CD18 MAb TS 1.18, temperature and divalent cation requirements further distinguish the Jurkat-PNHEV adhesive interaction from CD11a/18- and CD2-mediated adhesion. The PMA-induced phenotypic changes in the Jurkat line parallel late thymocyte differentiation as well as lymphocyte activation, suggesting that expression of the endothelial-binding lectin may be linked to one or both of these processes. The lectin-like activity on Jurkat cells is functionally indistinguishable from those previously linked to PNHEV recognition in normal human lymphocytes, normal rat lymphocytes and both normal and malignant murine lymphoid cells. In the mouse, this activity is either contained in or functionally linked to a member of the LEC-CAM family gp90Mel14, suggesting that Jurkat cells express the human homologue of the murine nodal homing receptor. Thus cultured T lymphoblastic malignancies express a variety of potential endothelial adhesion molecules but use primarily a highly conserved surface lectin to interact with PNHEV.

T cell receptor gamma and delta rearrangements in hematologic malignancies. Relationship to lymphoid differentiation

We have studied recombinatorial events of the T cell receptor delta and gamma chain genes in hematopoietic malignancies and related these to normal stages of lymphoid differentiation. T cell receptor delta gene recombinatorial events were found in 91% of acute T cell lymphoblastic leukemia, 68% of non-T, non-B lymphoid precursor acute lymphoblastic leukemia (ALL) and 80% of mixed lineage acute leukemias. Mature B-lineage leukemias and acute nonlymphocytic leukemias retained the T-cell receptor delta gene in the germline configuration. The incidence of T cell receptor gamma and delta was particularly high in CD10+CD19+ non-T, non-B lymphoid precursor ALL. In lymphoid precursor ALL, T cell receptor delta was frequently rearranged while T cell receptor gamma was in the germline configuration. This suggests that TCR delta rearrangements may precede TCR gamma rearrangements in lymphoid ontogeny. In T-ALL, only concordant T cell receptor delta and gamma rearrangements were observed. Several distinct rearrangements were defined using a panel of restriction enzymes. Most of the rearrangements observed in T-ALL represented joining events of J delta 1 to upstream regions. In contrast, the majority of rearrangements in lymphoid precursor ALL most likely represented D-D or V-D rearrangements, which have been found to be early recombinatorial events of the TCR delta locus. We next analyzed TCR delta rearrangements in five CD3+TCR gamma/delta+ ALL and cell lines. One T-ALL, which demonstrated a different staining pattern with monoclonal antibodies against the products of the TCR gamma/delta genes than the PEER cell line, rearranges J delta 1 to a currently unidentified variable region.

Demonstration of delta rec-pseudo J alpha rearrangement with deletion of the delta locus in a human stem-cell leukemia

It has been hypothesized that a rearrangement between the delta recombining element (delta Rec) and a pseudo J alpha gene serves to delete the TCR-delta locus before rearrangement of the TCR-alpha genes. We have now sequenced a direct, site-specific rearrangement between the delta Rec element and a pseudo J alpha gene in a human leukemic stem-cell line. Putative "N-sequence" addition was noted at the site of recombination, suggesting that this event occurred at a time when the enzyme(s) involved in N-region addition were active in this cell. This provides support for the view that deletion of the TCR-delta locus is required before rearrangement of the TCR-alpha chain genes.

Rearrangement of TCR gamma chain gene involving JP1 suggests early thymocyte origin of peripheral T-cell lymphoma

Peripheral T-cell lymphomas (PTL) are morphologically and immunophenotypically heterogeneous. We have examined a series of cases to determine whether this heterogeneity is reflected at the level of developmentally specific T-cell receptor (TCR) gene rearrangement. 4 of 5 cases had clonal rearrangements of TCR beta and gamma chain genes; one of these also had a probable DQ52-J immunoglobulin heavy chain gene rearrangement. 2 of the 4 TCR gamma gene rearrangements involved the most 5' J region, JP1, a characteristic of immature thymocytes. These 2 cases also had immunophenotypic features of immaturity. Taken together, our results suggest that TCR gene rearrangement is correlated with surface marker data and shows that in some cases PTL may arise from a very early stage of thymocyte maturation.

Rearrangement of variable region T cell receptor gamma genes in acute lymphoblastic leukemia. V gamma gene usage differs in mature and immature T cells

Using probes recognizing variable regions (V gamma) and joining regions (J gamma) of the T cell receptor (TCR) gamma gene, we have analyzed the usage of V gamma genes in 24 patients with T cell acute lymphoblastic leukemia (ALL) and 36 patients with B-precursor ALL. In CD3- T-ALL derived from immature T cells, V gamma genes more proximal to J gamma were frequently rearranged; V gamma 8, V gamma 9, V gamma 10, and V gamma 11 were used in 19 of 24 rearrangements. In contrast, CD3+ T-ALL derived from a more mature stage of T cell ontogeny, showed a high frequency of rearrangements involving V gamma genes distal to J gamma; V gamma 2, V gamma 3, V gamma 4, and V gamma 5 were used in 17 of 25 rearrangements. In B-precursor ALL, no notable bias of V gamma gene usage was observed. This probably reflects the possibility that TCR genes may not rearrange according to a T cell hierarchy when under control of a B cell gene program. Furthermore, deletions of those V gamma genes located 3' to rearranged V gamma genes were observed in all patients analyzed. This supports the theory that loop deletion is a major mechanism for TCR-gamma gene rearrangement.

Chromosomal translocation in a human leukemic stem-cell line disrupts the T-cell antigen receptor delta-chain diversity region and results in a previously unreported fusion transcript

We have studied a leukemic stem-cell line, DU.528, that is able to differentiate into myeloid and lymphoid cells. The leukemic cells have a translocation between chromosomes 1 and 14, t(1;14)(p33;q11), which we have molecularly cloned and sequenced. Initial screening used joining (J)-segment probes from the T-cell receptor (TCR) alpha- and delta-chain loci. In apparent concert with the translocation, a deletion has occurred between delta-chain diversity (D)-region genes D delta 1 and D delta 2. D delta 2 was observed on derivative chromosome 1 [der(1)] and D delta 1 on der(14) with a deletion of the intervening 10 kilobases of germ-line DNA. The nature of the D delta 1-D delta 2 deletional event implicates a lymphoid recombinase in the mechanism of the translocation. As a consequence of the translocation, an unusual fusion transcript was generated. Probes from chromosome 1 detected a previously unreported transcript in RNA from both the cell line and the patient. A chromosome 14 probe identified the same transcript, thus confirming a fusion transcript derived from both chromosomes 1 and 14. This translocation may identify a gene for which we propose the name SCL (stem-cell leukemia) that is important for hemopoietic development and oncogenesis and that has been disrupted or altered in this stem-cell line.

T-cell receptor gene rearrangement in B-cell non-Hodgkin's lymphoma: correlation with methylation and expression

Two of 19 B-cell non-Hodgkin's lymphoma (NHL) were found to have clonally rearranged T-cell receptor (TCR) beta chain genes with a germline TCR-gamma gene configuration. The inappropriate rearrangements had a similar structure to the TCR-beta rearrangements described in B-cell chronic lymphocytic leukemia. All cases analysed displayed a consistent germline transcription of TCR-beta and alpha chain genes which was independent of rearrangement. Consistent with this, all cases showed some degree of hypomethylation of the TCR-beta chain locus similar though distinguishable from the pattern seen in mature T cells, but quite different from that seen in normal mature B cells. Taken together, these data suggest that most NHL's arise from an immature B-lymphocyte precursor at a stage of differentiation where lineage commitment is incomplete.

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.

T cell receptor delta gene rearrangements in acute lymphoblastic leukemia

Using a newly isolated cDNA clone encoding the TCR-delta gene and genomic probes, we have analyzed T cell receptor (TCR) delta gene rearrangement in 19 patients with T cell acute lymphoblastic leukemia (T-ALL) and 29 patients with B-precursor ALL. Five out of seven CD3- T-ALL and 4 of 12 CD3+ T-ALL showed bi-allelic rearrangements of the TCR-delta gene. In three CD3+ patients, a single allelic TCR-delta gene rearrangement was observed with rearrangement of the TCR-alpha gene on the other allele. In five CD3+ patients with bi-allelic rearrangements of the TCR-alpha gene, the TCR-delta gene locus was deleted. Transcription of the TCR-delta gene was also analyzed in six T-ALL. Five patients expressed TCR-delta transcripts. Only one T-ALL, presumably derived from the most immature T lineage cells, did not have TCR-delta transcripts, but expressed TCR-gamma and 1.0-kb truncated TCR-beta transcripts. In B-precursor ALL, 20 patients (69%) showed rearrangements of the TCR-delta gene. The frequency of TCR-delta gene rearrangement was higher than TCR-alpha (59%), gamma (52%), or beta (31%) genes. These findings suggest that TCR-alpha gene rearrangements may take place after rearrangements of the TCR-delta gene with concomitant deletion of rearranged TCR-delta genes in T cell differentiation. Among leukemic cells of B lineage, the TCR-delta gene is the earliest rearranging TCR gene, followed by TCR-gamma and beta gene rearrangements.