T-cell Antigen Receptor Beta-chain Gene Research Articles

Mutant p53: epigenetic mutator of the T-cell receptor via induction of methylation.

The mechanism and effects of epigenetic alterations in human carcinogenesis are not well understood, except that cancers often have alterations in the methylation status of their genomes. Additionally, human cancers, including aggressive T-cell leukemias and lymphomas, have a high frequency of p53 mutations, particularly missense mutations, which raises the possibility of gain-of-new-function proteins, but the new proteins' oncogenic functions are mechanistically ill-defined. To investigate the mechanisms behind the high prevalence of p53 tumor suppressor gene mutations in aggressive or relapsed T-cell leukemias, we transfected Jurkat cells null for p53 protein with a temperature-sensitive p53 mutant. We showed that this mutant p53 abrogated expression of the T-cell antigen receptor (TCR) by affecting the methylation of an at least 20-kb region of DNA, 5'to the TCR beta-chain gene enhancer region, which includes TCRbetaC1 and betaC2. Expression of the TCR is restored when the temperature is reduced to 32 degrees C, at which temperature the mutant p53 regains wild-type function. The TCR, a common site of dysfunction in T-cell malignancies, is the principal signal transduction moiety controlling both T-cell activation and activation-induced apoptosis. These results suggest a new role for mutant p53-as an epigenetic mutator, bridging p53, methylation, and transcriptional silencing-and suggest novel mechanisms in immunosuppression and cancer progression.

Regulation of T-cell antigen receptor (TCR) alpha-chain expression by TCR beta-chain transcripts.

The TCR is an alpha beta heterodimer, a part of the multimeric structure through which physiological T-cell activation occurs. The expression of TCR alpha chain is greatly diminished in a beta-chain-deficient mutant Jurkat cell line (J.RT3-T3.5). The relationship between the expression of the TCR alpha and beta chains has been examined by stable transfection of a series of TCR beta-chain mutant constructs into this mutant cell line. The level of alpha-chain transcript was dramatically upregulated by the expression of the beta chain and specifically by a transcript of the beta-chain variable region alone, including a transcript in which the ATG start codon was mutated. The downregulation of the endogenous alpha-chain transcripts in mutants cells lacking complete beta-chain transcripts occurred primarily at the posttranscriptional level. This evidence for a regulatory function of the TCR beta-chain gene represents an unusual regulatory pathway in which the transcript of one gene is required for the optimal expression of another gene.

T-cell receptor gene homologs are present in the most primitive jawed vertebrates.

The phylogenetic origins of T-cell immunity and T-cell antigen receptor (TCR) genes have not been established. A PCR approach using short, minimally degenerate oligodeoxynucleotide primers complementing conserved variable region segments amplifies TCR-like products from the genomic DNA of Heterodontus francisci (horned shark), a representative phylogenetically primitive cartilaginous fish. One of these products has been used as a probe to screen a Heterodontus spleen cDNA library and a clone was identified that is most related at the nucleotide sequence and predicted peptide levels to higher vertebrate TCR beta-chain genes. Genomic analyses of the TCR homologs indicate that recombining variable and joining region segments as well as constant region exons are encoded by extensive gene families, organized in the multicluster form, characteristic of both the immunoglobulin heavy- and light-chain gene loci in the cartilaginous fishes. Greater numbers of homologous products were identified when a probe complementing the putative constant region of the TCR homolog was used to screen the same cDNA library. A high degree of intergenic variation is associated with the putative variable region segments of these isolates. Direct evidence is presented for TCR-like genes, which presumably are associated with T-cell function, at the earliest stages in the phylogenetic emergence of jawed vertebrates.

Unusual organization of the human T-cell receptor beta-chain gene complex is linked to recombination hotspots.

Two rare Sfi I polymorphisms of 360 kb and 280 kb present within the human T-cell antigen receptor beta-chain gene complex were revealed by pulsed-field gel electrophoresis. They represent allelic variants of the polymorphic 330- and 300-kb Sfi I fragments previously described. The 360-kb polymorphism results from duplication of the 30-kb DNA fragment responsible for the 330/300-kb insertion/deletion-related polymorphism. The 280-kb polymorphism results from a 20-kb deletion from the 300-kb SfiI allele. The rare polymorphisms also map on either side of a Sal I site located near a recombination hotspot, suggesting that germline duplications and deletions arose from nonhomologous crossover events.

Pathogenesis of feline leukemia virus T17: contrasting fates of helper, v-myc, and v-tcr proviruses in secondary tumors.

A naturally occurring feline thymic lymphosarcoma (T17) provided the unique observation of a T-cell antigen receptor beta-chain gene (v-tcr) transduced by a retrovirus. The primary tumor contained three classes of feline leukemia virus (FeLV) provirus, which have now been characterized in more detail as (i) v-tcr-containing recombinant proviruses, (ii) v-myc-containing recombinant proviruses, and (iii) apparently full-length helper FeLV proviruses. The two transductions appear to have been independent events, with distinct recombinational junctions and no sequence overlap in the host-derived inserts. The T17 tumor cell line releases large numbers of FeLV particles of low infectivity; all three genomes are encapsidated, but passage of FeLV-T17 on feline fibroblast and lymphoma cells led to selective loss of the recombinant viruses. The oncogenic potential of the T17 virus complex was, therefore, tested by infection of neonatal cats with virus harvested directly from the primary T17 tumor cell line. A single inoculation of FeLV-T17 caused persistent low-grade infection culminating in thymic lymphosarcoma and acute thymic atrophy, which was accelerated by coinfection with the weakly pathogenic FeLV subgroup A (FeLV-A)/Glasgow-1 helper. Molecularly cloned FeLV-tcr virus (T-31) rescued for replication by a weakly pathogenic FeLV-A/Glasgow-1 helper virus was similarly tested in vivo and induced thymic atrophy and thymic lymphosarcomas. Most FeLV-T17-induced tumors manifested either v-myc or an activated c-myc allele and had undergone rearrangement of endogenous T-cell antigen receptor beta-chain genes, supporting the proposition that the oncogenic effects of c-myc linked to the FeLV long terminal repeat are targeted to a specific window in T-cell differentiation. However, neither the FeLV-T17-induced tumors nor the T-31 + FeLV-A-induced tumors contained clonally represented v-tcr sequences. Only one of the FeLV-T17-induced tumors contained detectable v-tcr proviruses, at a low copy number. While v-tcr does not have a readily transmissible oncogenic function, a more restricted role is not excluded, perhaps involving antigenic peptide-major histocompatibility complex recognition by the T-cell receptor complex. Such a function could be obscured by the genetic diversity of the outbred domestic cat host.

Prognostic value of lymphocyte surface markers in acute myeloid leukemia [see comments

We studied the expression of cell surface antigens associated with myeloid and lymphoid leukemias on bone marrow-derived blast cells from 339 patients with newly diagnosed de novo acute myeloid leukemia (AML) enrolled on Cancer and Leukemia Group B (CALGB) chemotherapy protocols. Surprisingly, of 211 cases studied for the expression of CD2 (T-cell marker, sheep erythrocyte binding receptor for T lymphocytes) 45 were positive (21%). In addition, of 298 patients studied for CD19 (B- lymphocyte marker), 41 were positive (14%). Overall, of 170 patients studied for both CD2 and CD19, 56 (33%) were positive. Interestingly, central review of the French-American-British (FAB) morphology of the CD2- and CD19-positive cases showed that FAB M3 was twice as frequent, and M4E eight times as frequent compared with the CD2- and CD19- negative cases. Of 22 lymphocyte antigen-positive cases in which cells were available for studies of Ig or T-cell antigen receptor (TCR) gene rearrangement, 20 were germline, one had a rearranged Ig heavy chain gene, and one had rearranged TCR beta and Ig heavy chain genes. The presence of messenger RNA for CD2 was demonstrated in four CD2 surface antigen-positive cases, thus validating the cell surface data. Lymphocyte antigen-positive cases had karyotypes commonly seen in AML; 71% of cases with an abnormal clone had t(8;21)(q22;q22), inversion 16(p13q22), t(15;17)(q22;q12), or t(9;11)(p22;q23). The patients with lymphocyte markers had a significantly higher incidence of these karyotypic abnormalities compared with patients with lymphocyte antigen- negative AML (34% v 15%, P less than .02). When the outcome to therapy of the lymphocyte antigen-positive cases was compared with that for the CD2, CD19-negative cases, we found that the CD2, CD19-positive cases actually had higher complete remission rates (75% v 59%, P = .04), and significantly longer time to failure (P = .02; 32.4% +/- 6.0% v 18.0% +/- 4.1% at 2 years) and overall survival (P = .02; 43.5% +/- 6.3% v 26.0% +/- 4.5% at 2 years). CD2 antigen-positive cases also had a significantly superior survival (P = .02; 43.8% +/- 7.9% v 29.8% +/- 3.8% at 2 years). There were no significant differences (P less than or equal to .05) between the two groups in age, leukocyte count at diagnosis, incidence of extramedullary disease, or FAB classification.(ABSTRACT TRUNCATED AT 400 WORDS)

Rearrangements of T-cell antigen receptor delta chain gene in hematologic neoplasms

Rearrangements of the T-cell antigen receptor (TCR) delta chain gene were studied in primary neoplastic cells from 137 patients with leukemia or lymphoma. TCR delta gene rearrangements or deletions were observed in all 50 T-cell neoplasms: 5 of 8 CD3- T-cell neoplasms showed rearrangements, whereas biallelic deletion of TCR delta gene was the most common pattern in CD3+ T-cell neoplasm (39 of 42 patients). Rearrangements of TCR delta gene were also detected in 23 of 40 immature B-cell leukemias, including 22 of 25 patients with rearrangements of TCR gamma gene, 2 of 17 mature B-cell neoplasms, and 3 of 30 myeloid leukemias. Thus, TCR delta gene rearrangement or deletion is always found in T-cell neoplasms and is frequently found in immature B-cell leukemias associated with TCR gamma gene rearrangement. Furthermore, TCR delta gene rearrangements associated with the germline configuration of the TCR beta, gamma, and immunoglobulin heavy chain genes were observed in two immature T-cell leukemias, suggesting that TCR delta gene rearrangements precede TCR gamma and beta gene rearrangements. These results indicate that an analysis of TCR delta gene rearrangement provides potential tools to establish the clonality of immature T-cell neoplasms and to identify the normal stages of lymphocyte differentiation.

Rearrangements of T-Cell Antigen Receptor 8 Chain Gene in Hematologic Neoplasms

Rearrangements of the T-cell antigen receptor (TCR) delta chain gene were studied in primary neoplastic cells from 137 patients with leukemia or lymphoma. TCR delta gene rearrangements or deletions were observed in all 50 T-cell neoplasms: 5 of 8 CD3- T-cell neoplasms showed rearrangements, whereas biallelic deletion of TCR delta gene was the most common pattern in CD3+ T-cell neoplasm (39 of 42 patients). Rearrangements of TCR delta gene were also detected in 23 of 40 immature B-cell leukemias, including 22 of 25 patients with rearrangements of TCR gamma gene, 2 of 17 mature B-cell neoplasms, and 3 of 30 myeloid leukemias. Thus, TCR delta gene rearrangement or deletion is always found in T-cell neoplasms and is frequently found in immature B-cell leukemias associated with TCR gamma gene rearrangement. Furthermore, TCR delta gene rearrangements associated with the germline configuration of the TCR beta, gamma, and immunoglobulin heavy chain genes were observed in two immature T-cell leukemias, suggesting that TCR delta gene rearrangements precede TCR gamma and beta gene rearrangements. These results indicate that an analysis of TCR delta gene rearrangement provides potential tools to establish the clonality of immature T-cell neoplasms and to identify the normal stages of lymphocyte differentiation.

Nonlinkage of the T cell receptor alpha, beta, and gamma genes to systemic lupus erythematosus in multiplex families.

To test the possibility that T cell antigen receptor (TcR) genes are linked to the genes involved in the pathogenesis of systemic lupus erythematosus (SLE), genomic DNA restriction fragment length polymorphisms were studied, using the Southern blot technique, in 5 families with multiple members with SLE, 14 unrelated SLE patients, and 14 normal controls. Polymorphic patterns were detected with probes for all 3 TcR chains, but there was no significant difference in the distribution of the restriction fragment length polymorphism pattern among the patients, the relatives, and the controls. Furthermore, in the families with at least 2 individuals with the disease, each of the 3 TcR chain genes did not cosegregate with the disease. We conclude that TcR alpha, beta, and gamma chain genes are not likely to be linked to genes related to SLE.

DNA segment containing C beta 1, a gene for the constant region of the beta chain of the T-cell antigen receptor, was inserted into chromosome 6 in cells from one patient with human T-cell leukemia.

DNA rearrangements that occurred in the vicinity of T-cell antigen receptor beta-chain gene clusters residing on chromosome 7 were examined in human T-cell acute lymphoblastic leukemia cells. In one patient, it was observed that, for the T-cell receptor beta-chain genes, a D beta 1-J beta 2.3 (where D is diversity and J is joining) junction was found on one chromosome, while the other chromosome kept the germ-line configuration. If this D beta-J beta junction was formed by the customary deletion mechanism, the C beta 1 gene (where C is constant) located between the D beta 1 and J beta 2.3 loci should have disappeared from this chromosome. The C beta 1 gene indeed was absent from the rearranged chromosome 7, but it was found on chromosome 6 as an inserted segment. The implications of the observations are discussed.

Genotypic Analysis of Cutaneous T-Cell Lymphomas

The gene encoding the beta-chain of the T-cell antigen receptor (TCR) has been analyzed for evidence of rearrangement in skin, blood, and lymph node specimens from 23 cases of known or suspected cutaneous T-cell lymphoma (CTCL). Two cutaneous large cell lymphomas, 4 cases of Sézary syndrome, and 5 cases of advanced (tumor) stages of mycosis fungoides showed clonal rearrangement of the TCR beta-chain gene in all samples, including lymph nodes in which histologic examination revealed only dermatopathic lymphadenitis. These results indicate that DNA analysis provides a valuable means for improving the diagnosis of extracutaneous disease in advanced stages of CTCL. In contrast, the gene was in a germline configuration in all samples from 12 patients with plaque stages of mycosis fungoides or suspected early CTCL, suggesting that in these 2 conditions the T-cell proliferation is either polyclonal or contains very few monoclonal (i.e., neoplastic) cells.

Retroviral transduction of T-cell antigen receptor beta-chain and myc genes.

Support for multistage models of oncogenesis has been provided by several highly leukaemogenic retrovirus isolates that have transduced more than one host cell gene. Where functional studies have been performed, these retroviral oncogenes show synergy for in vitro transformation and leukaemogenesis. In naturally occurring feline leukaemias associated with feline leukaemia virus (FeLV), retroviral transduction of myc is a frequent oncogenic mechanism. But evidence suggesting that the FeLV v-myc genes might be insufficient for leukaemogenesis was provided by the latency (12 weeks) and clonality of FeLV/v-myc-induced tumours and the absence of demonstrable in vitro transformation by these viruses. In the search for secondary leukaemogenic events in FeLV/v-myc tumours, we have identified a case of FeLV transduction of a T-cell antigen receptor beta-chain gene. The proviruses carrying this gene (which we have named v-tcr) were a separate population from those carrying v-myc. In its normal role, the T-cell receptor beta-chain forms part of a multimeric complex involved in antigen recognition and T-cell activation. We suggest that v-tcr is a novel viral oncogene which assisted v-myc in the genesis of a naturally occurring case of thymic lymphosarcoma.

Viral transduction of host genes in naturally occurring feline T-cell leukaemias: transduction of myc and a T-cell antigen receptor beta-chain gene.

Feline leukaemia virus has been a particularly useful tool in cancer research since many of the naturally occurring tumours associated with this virus group have yielded recombinant retroviruses containing hostderived oncogenic information. The prevalence of transduction as an oncogenic mechanism was seen first in multicentric fibrosarcoma, a relatively rare tumour in FeLV-infected cats (Hardy et al. 1982; Besmer 1984). In a significant percentage of cases of this disease, oncogene-containing feline sarcoma viruses have been identified. More recently, we and others have found that in the more common FeLV-associated neoplasm, thymic lymphosarcoma, viral capture of the c-myc gene can occur (Neil et al. 1984; Levy et al. 1984; Mullins et al. 1984). Since the oncogenes carried by feline sarcoma viruses do not include myc, these reports provided the first evidence that myc may be a target for oncogenic activation by FeLV.KeywordsViral TransductionFeline Leukaemia VirusAntigen Receptor GeneProviral InsertionAntigen Receptor Gene RearrangementThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Functional alpha and beta T cell chain receptor messages can be detected in old but not in young athymic mice.

The expression and sequences of T cell antigen receptor (TcR) alpha and beta-chain genes were investigated in the spleens from congenitally athymic (nude) mice. A small number of Thy-1+ cells (approximately 7.0%) was found in nylon wool-enriched spleen cells from young (8 weeks old) nude mice but no L3T4 or Lyt-2 surface antigens were detected. These nude mice expressed only a low level of 1.0-kb beta-chain mRNA and little or no alpha-gene transcripts. On the other hand the number of Thy-1+ spleen cells increased slightly (to 24%) in old (20 weeks old) nude mice and a small number of L3T4+ (10%) and/or Lyt-2+ (5%) cells were detectable. "Full length" 1.7-kb alpha-chain and 1.3-kb beta-chain messages could be found in nylon wool-enriched spleen cells from old nude mice. Sequence analysis of the cDNA revealed that no functional alpha and beta-chain genes can be detected in the spleen cells of young athymic mice while some of the old mice with nu/nu genotype are composed of completely rearranged V-(D)-J-C-gene segments which encode potentially functional proteins. Interestingly, two of three independent cDNA clones encoding the alpha chain used the same V alpha and J alpha-gene segments. These results suggest that extrathymic TcR alpha and beta-chain gene rearrangements do occur, though slowly, to some extent, in nude mice and may be responsible for the limited antigen and/or H-2-related T cell functions in these old athymic mice. The data further suggests that the TcR repertoire in athymic mice may also be limited.

Abnormal recombination products result from aberrant DNA rearrangement of the human T-cell antigen receptor beta-chain gene.

Two unusual rearrangements of the T-cell antigen receptor beta-chain gene have occurred in the human T-cell tumor line CEM. The beta chain of the T-cell antigen receptor is encoded in germ-line DNA by immunoglobulin-like gene segments that rearrange during the somatic development of T cells to form active genes. Structural analysis of rearranged immunoglobulin genes has already revealed a great deal about the mechanisms by which these genes rearrange. To further characterize the mechanism by which beta-chain genes rearrange, we have determined the organization of the rearranged beta-chain gene segments in the human T-cell tumor line CEM. Three rearranged joining (J) or diversity (D) segments of the beta-chain gene are found in CEM. One of these segments rearranged during the formation of a normal rearranged beta-chain gene that comprises a variable (V beta), D beta, and J beta gene segment associated with a constant region gene segment. Two abnormal recombination products are found at the other rearranged beta-chain locus. One product has the structure, J beta-D beta-J beta, with the J beta gene segments joined in a head-to-head fashion, while the other one consists of a V beta-D beta recombined segment not associated with a J beta gene segment. We propose that the J beta-D beta-J beta structure was formed by an inversion of 6 kilobases of DNA and subsequently, a V beta-D beta rearrangement occurred. The presence of these products in CEM has important implications for our understanding of the mechanism by which somatic rearrangements of beta-chain gene segments occur.