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

Autocrine HGF/c-Met signaling pathway confers aggressiveness in lymph node adult T-cell leukemia/lymphoma

Adult T-cell leukemia/lymphoma (ATL) is an aggressive T-cell neoplasm. While ATL cells in peripheral blood (PB-ATL) are sensitive to anti-CC chemokine receptor 4 treatment, non-PB-ATLs, including lymph node ATLs (LN-ATLs), are more aggressive and resistant. We examined characteristic cytokines and growth factors that allow non-PB-ATLs to proliferate and invade compared with PB-ATLs. Protein array analysis revealed hepatocyte growth factor (HGF) and C-C motif chemokine 2 (CCL2) were significantly upregulated in non-PB-ATLs compared with PB-ATLs. The HGF membrane receptor, c-Met, was expressed in PB-ATL and non-PB-ATL cell lines, but CCR2, a CCL2 receptor, was not. Immunohistochemical analysis in clinical ATLs revealed high HGF expression in LNs, pharynx, bone marrow, and tonsils. The HGF/c-Met signaling pathway was active downstream in non-PB-ATLs. Downregulation of HGF/c-Met by siRNA or chemical inhibitors decreased in vitro and in vivo proliferation and invasion by non-PB-ATLs. Treatment with bromodomain and extra-terminal motif inhibitor suppressed HGF expression and decreased levels of histone H3 lysine 27 acetylation (H3K27Ac) and bromodomain-containing protein 4 (BRD4) binding promoter and enhancer regions, suppressing non-PB-ATL cellular growth. Our data indicate H3K27Ac/BRD4 epigenetics regulates the HGF/c-MET pathway in ATLs; targeting this pathway may improve treatment of aggressive non-PB-ATLs.

Development of a novel redirected T-cell–based adoptive immunotherapy targeting human telomerase reverse transcriptase for adult T-cell leukemia

The efficacy and safety of a novel redirected T-cell–based adoptive immunotherapy targeting hTERT for patients with adult T-cell leukemia. hTERT-specific T-cell receptor gene-transduced CD8+ T cells lyse ATL cells, but not normal cells, both in vitro and in vivo.

LKB1 tumor suppressor and salt-inducible kinases negatively regulate human T-cell leukemia virus type 1 transcription

BACKGROUND

Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia (ATL). Treatment options are limited and prophylactic agents are not available. We have previously demonstrated an essential role for CREB-regulating transcriptional coactivators (CRTCs) in HTLV-1 transcription.

RESULTS

In this study we report on the negative regulatory role of LKB1 tumor suppressor and salt-inducible kinases (SIKs) in the activation of HTLV-1 long terminal repeats (LTR) by the oncoprotein Tax. Activation of LKB1 and SIKs effectively blunted Tax activity in a phosphorylation-dependent manner, whereas compromising these kinases, but not AMP-dependent protein kinases, augmented Tax function. Activated LKB1 and SIKs associated with Tax and suppressed Tax-induced LTR activation by counteracting CRTCs and CREB. Enforced expression of LKB1 or SIK1 in cells transfected with HTLV-1 molecular clone pX1MT repressed proviral transcription. On the contrary, depletion of LKB1 in pX1MT-transfected cells and in HTLV-1-transformed T cells boosted the expression of Tax. Treatment of HTLV-1 transformed cells with metformin led to LKB1/SIK1 activation, reduction in Tax expression, and inhibition of cell proliferation.

CONCLUSIONS

Our findings revealed a new function of LKB1 and SIKs as negative regulators of HTLV-1 transcription. Pharmaceutical activation of LKB1 and SIKs might be considered as a new strategy in anti-HTLV-1 and anti-ATL therapy.

Clonal evolution of adult T-cell leukemia/lymphoma takes place in the lymph nodes

Adult T-cell leukemia/lymphoma (ATLL) is the neoplasm caused by human T-cell leukemia virus type 1 (HTLV-1). We performed oligo-array comparative genomic hybridization (CGH) against paired samples comprising peripheral blood (PB) and lymph node (LN) samples from 13 patients with acute ATLL. We found that the genome profiles of the PB frequently differed from those of the LN samples. The results showed that 9 of 13 cases investigated had a log2 ratio imbalance among chromosomes, and that chromosome imbalances were more frequent in LN samples. Detailed analysis revealed that the imbalances were likely caused by the presence of multiple subclones in the LN samples. Five of 13 cases showed homozygous loss regions in PB samples, which were not found in the LN samples, indicating that tumors in the PB were derived from LN subclones in most cases. Southern blot analysis of TCRγ showed that these multiple subclones originated from a common clone. We concluded that in many ATLL cases, multiple subclones in the LNs originate from a common clone, and that a selected subclone among the LN subclones appears in the PB.

NK314 potentiates antitumor activity with adult T-cell leukemia-lymphoma cells by inhibition of dual targets on topoisomerase II{alpha} and DNA-dependent protein kinase

Adult T-cell leukemia-lymphoma (ATL) is an aggressive disease, incurable by standard chemotherapy. NK314, a new anticancer agent possessing inhibitory activity specific for topoisomerase IIα (Top2α), inhibited the growth of various ATL cell lines (50% inhibitory concentration: 23-70nM) with more potent activity than that of etoposide. In addition to the induction of DNA double-strand breaks by inhibition of Top2α, NK314 induced degradation of the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), resulting in impaired DNA double-strand break repair. The contribution of DNA-PK to inhibition of cell growth was affirmed by the following results: NK314 inhibited cell growth of M059J (a DNA-PKcs-deficient cell line) and M059K (a cell line with DNA-PKcs present) with the same potency, whereas etoposide exhibited weak inhibition of cell growth with M059K cells. A DNA-PK specific inhibitor, NU7026, enhanced inhibitory activity of etoposide on M059K as well as on ATL cells. These results suggest that NK314 is a dual inhibitor of Top2α and DNA-PK. Because ATL cells express a high amount of DNA-PKcs, NK314 as a dual molecular targeting anticancer agent is a potential therapeutic tool for treatment of ATL.

Autoimmune regulator (AIRE) gene is expressed in human activated CD4+ T-cells and regulated by mitogen-activated protein kinase pathway

The autoimmune regulator (AIRE) gene is a gene responsible for autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy. Here we show that AIRE is expressed in human peripheral CD4-positive T-cells, and most highly in antigen-and interleukin 2-stimulated T (IL-2T) cells. Mitogen-activated protein kinases (MAPKs), including MAPK kinase (MEK) 1/2 and p38 MAPK, were phosphorylated in IL-2T cells and the expression of the AIRE gene was inhibited by a specific p38 MAPK inhibitor (SB203580), thereby indicating that AIRE gene expression is controlled by the MAPK pathway in IL-2T cells. These data suggested the possible significance of the AIRE gene in the peripheral immune system.

The CC Chemokine Receptor 4 as a Novel Specific Molecular Target for Immunotherapy in Adult T-Cell Leukemia/Lymphoma

Adult T-cell leukemia/lymphoma (ATLL) is a peripheral T-cell neoplasm with dismal prognosis, and no optimal therapy has been developed. We tested the defucosylated chimeric anti-CC chemokine receptor 4 (CCR4) monoclonal antibody, KM2760, to develop a novel immunotherapy for this refractory tumor. In the presence of peripheral blood mononuclear cells (PBMCs) from healthy adult donors, KM2760 induced CCR4-specific antibody-dependent cellular cytotoxicity (ADCC) against CCR4-positive ATLL cell lines and primary tumor cells obtained from ATLL patients. We next examined the KM2760-induced ADCC against primary ATLL cells in an autologous setting. Antibody-dependent cellular cytotoxicity mediated by autologous effector cells was generally lower than that mediated by allogeneic control effector cells. However, a robust ADCC activity was induced in some cases, which was comparable with that mediated by allogeneic effector cells. It suggests that the ATLL patients' PBMCs retain substantial ADCC-effector function, although the optimal conditions for maximal effect have not yet been determined. In addition, we also found a high expression of FoxP3 mRNA and protein, a hallmark of regulatory T cells, in ATLL cells, indicating the possibility that ATLL cells originated from regulatory T cells. KM2760 reduced FoxP3 mRNA expression in normal PBMCs along with CCR4 mRNA by lysis of CCR4+ T cells in vitro. Our data suggest not only that the CCR4 molecule could be a suitable target for the novel antibody-based therapy for patients with ATLL but also that KM2760 may induce effective tumor immunity by reducing the number of regulatory T cells.

Identification and characterization of a novel gene, C13orf25, as a target for 13q31-q32 amplification in malignant lymphoma

The amplification at 13q31-q32 has been reported in not only hematopoietic malignancies but also in other solid tumors. We identified previously frequent amplification of chromosomal band 13q31-q32 in 70 cases of diffuse large B-cell lymphoma patients by conventional comparative genomic hybridization analysis. In an attempt to identify a candidate gene within this region, we used array comparative genomic hybridization and fluorescent in situ hybridization to map the 13q31-q32 amplicon. We then screened the 65 expressed sequence tags and Glypican 5 (GPC5) by reverse transcription-PCR and Northern blotting. As a result, we identified a novel gene, designated Chromosome 13 open reading frame 25 (C13orf25), which was overexpressed in B-cell lymphoma cell lines and diffuse large B-cell lymphoma patients with 13q31-q32 amplifications. However, GPC5, which has been reported to be a target gene for 13q31-q32 amplification, was truncated in one cell line, Rec1, possessing the amplification, and its expression in various cell lines with amplification at 13q31-q32 was not significantly different from that in other cell lines without amplification, suggesting that GPC5 is not likely to be the candidate gene. Additional analysis identified two major transcripts in the C13orf25 gene. The two transcripts A and B predicted open reading frames of 32 and 70-amino acid polypeptides, respectively. The former has been reported as bA121J7.2, which is conserved among species. Transcript-B also contained seven mature microRNAs in its untranslated region. These results suggest that the C13orf25 gene is the most likely candidate gene for the 13q31-q32 amplicon found in hematopoietic malignancies.

Rapid isolation of viral integration site reveals frequent integration of HTLV-1 into expressed loci

Although there is tight association of the human T-cell leukemia virus type-1 (HTLV-1) with adult T-cell leukemia/lymphoma (ATLL), it has remained unresolved whether the HTLV-1 integration into the host genome has any role in the development of this disease. We isolated a total of 58 HTLV-1 integration sites using newly developed, adaptor-ligated PCR from 33 ATLL patients and five ATLL cell lines. We compared our data as well as the previously reported ones with the complete human genomic sequence for the location of its placement, structure, and expression of genes nearby the integration site. The chromosomal target for integration was selected at random, but the integration favorably occurred within the transcription units; more than 59.5% of total integration was observed within the transcriptional unit. All inserted genes by HTLV-1 integration were expressed in normal T cells. Upregulation of genes due to viral integration was found in two out of nine ATLL cases; about 4.4- and 102-fold elevated ankyrin-1 ( ANK-1) and gephyrin ( GPHN) gene expressions were observed, respectively. These data suggest that the preferential integration of HTLV-1 into an expressed locus occasionally causes deregulation of corresponding gene, which may lead to leukemogenesis of a fraction of ATLL.

Molecular cytogenetic analysis of the breakpoint region at 6q21-22 in T-cell lymphoma/leukemia cell lines

Chromosome band 6q21 is reported to be one of the most frequent target regions in T-cell lymphoma for both translocations and deletions. To explore whether the breakpoint clustering in T-cell malignancy indicates the presence of a common breakpoint region in 6q, we employed fluorescence in situ hybridization analysis using various YAC, BAC, and PAC clones aligned at 6q21-22. We identified two T-cell lymphoma/leukemia cell lines with different differentiation stages that had breakpoints within the same novel gene, TCBA1 (T-cell lymphoma breakpoint associated target 1). In a T-cell lymphoblastic lymphoma cell line, HT-1, the TCBA1 fused to SUSP1 (SUMO-1-specific protease), creating a SUSP1-TCBA1 chimeric gene. However, in an adult T-cell leukemia cell line, ATN-1, no chimeric gene was detected, although aberrant TCBA1 transcripts were produced. We conclude that TCBA1 is a possible target gene for T-cell lineage-specific chromosome aberrations at 6q21.

A novel c-Myc-responsive gene, JPO1, participates in neoplastic transformation

We have identified a novel c-Myc-responsive gene, named JPO1, by representational difference analysis. JPO1 responds to two inducible c-Myc systems and behaves as a direct c-Myc target gene. JPO1 mRNA expression is readily detectable in the thymus, small intestine, and colon, whereas expression is relatively low in spleen, bone marrow, and peripheral leukocytes. We cloned a full-length JPO1 cDNA that encodes a 47-kDa nuclear protein. To determine the role of JPO1 in Myc-mediated cellular phenotypes, stable Rat1a fibroblasts overexpressing JPO1 were tested and compared with transformed Rat1a-Myc cells. Although JPO1 has a diminished transforming activity as compared with c-Myc, JPO1 complements a transformation-defective Myc Box II mutant in the Rat1a transformation assay. This complementation provides evidence for a genetic link between c-Myc and JPO1. Similar to c-Myc, JPO1 overexpression enhances the clonogenicity of CB33 human lymphoblastoid cells in methylcellulose assays. These observations suggest that JPO1 participates in c-Myc-mediated transformation, supporting an emerging concept that c-Myc target genes constitute nodal points in a network of pathways that lead from c-Myc to various Myc-related phenotypes and ultimately to tumorigenesis.

Arsenic induces apoptosis in B-cell leukaemic cell lines in vitro: activation of caspases and down-regulation of Bcl-2 protein

We showed that arsenic inhibited the cell growth of four B-cell leukaemia cell lines of 11 various cell lines in vitro. In two of these four lines, KOCL44 and LyH7, apoptosis was identified by morphological and nucleosomal DNA fragmentation studies. Three of the four B-cell lines that were growth inhibited were acute infantile leukaemia with t(11;19)(q23;p13) translocations involving the MLL gene that encodes the transcriptional factor Drosophila trithorax. The arsenic-induced apoptosis in KOCL44 and LyH7 cells was found to be linked to caspases by Western blot and enzymological analyses. The amount of Bcl-2 was reduced during apoptosis in LyH7 as judged by Western blot analysis. We concluded that combined activation of the caspases and down-regulation of Bcl-2 could determine the fate of B-cell leukaemic cells in response to arsenic.

A novel myeloid cell line, Marimo, derived from therapy-related acute myeloid leukemia during treatment of essential thrombocythemia: consistent chromosomal abnormalities and temporary C-MYC gene amplification

A novel myeloid leukemia cell line, Marimo, was established from bone marrow cells of a patient with secondary acute myeloid leukemia (AML) that had developed during the treatment of essential thrombocythemia (ET) with busulfan. Karyotype at the ET phase was 46,XX,der(15)t(1;15) (q23;p12-13), but at the blastic phase changed to 44,XX,-5,del(8)(q22), add(17)(p11),+18, psu dic(18;9) (q23;p21) x 2 lacking t(1;15). In Marimo cells, C-MYC gene was temporarily amplified by double-minutes (dmin) but disappeared at 33 months, whereas t(10;14;11)(q22;q32;q13) and t(10;14)(q22;q32) were added in vitro psu dic(18;9) x 2 and add(17)(p11) were consistently found throughout the culture. These results suggest that this AML clone is not derived from ET but rather is therapy-related.

Karyotypic evolution of cells in culture: a new concept

The Chapter summarizes peculiarities of karyotypic variability during establishment and long-term cultivation of permanent cell lines. A new concept on pathways of karyotypic evolution of cells in culture is put forward. A detailed description is presented of the author's original approach of cytogenetic analysis of cell lines provided for a principally new characteristic of the cell line: its generalized reconstructed karyotype (GRK). Its use as a criterion to evaluate authenticity, purity, and stability of cell lines is discussed. Based on analysis of the GRK, two stages of karyotype evolution of cell lines are revealed: establishment and stabilization, different in karyotypic variability of the cell population and in peculiarities of clone selection. Comparison of peculiarities of karyotypic variability of leukemic and tumor cells both in vitro and in vivo was made, and general regularities of their karyotypic evolution have been established, such as nonrandom changes in the number and structure of chromosomes and deletion of one of the sex chromosomes, as well as regularities characteristic only of cells in culture in most human and animal cell lines (at least 85%) of disomy on all autosomes. The rest of the cell lines, 15%, are characterized by either partial or total monosomies on certain autosomes during long-term cultivation. Three main compensatory mechanisms of maintaining viability of cell lines that have lost genetic material are discussed: polyploidization of the initial cell clone, amplification of oncogenes (predominantly of mys family), and extracopying of whole autosomes or of their fragments.

Unusual feature of the T-cell receptor genes in T-lineage acute lymphoblastic leukemia

We characterized the T-cell receptor (TCR) gene rearrangements and sequences in 15 T-lineage acute lymphoblastic leukemia (T-ALL) and seven adult T-cell leukemia (ATL) samples. Southern blot analysis showed that neither of the two TCR delta alleles was deleted in two T-ALL samples, suggesting that the TCR alpha loci have a germ line configuration. The TCR alpha and beta sequences were cloned and sequenced by reverse transcriptase-inverse polymerase chain reaction. Two T-ALL samples had a long complementarity determining region (CDR), three of the alpha chain and the other two T-ALL samples had long CDR3 of the beta chain, compared with normal peripheral blood lymphocytes (PBL). Thus, a total of six T-ALL samples had unusual TCR gene structure, which was unrelated to the immunophenotype. On the other hand, CDR3 length in ATL samples was similar to normal PBL. These data suggest that T-ALL is derived from an immature T-cell repertoire which undergoes TCR gene rearrangement or has not been negatively selected.

Karyotypic characterization of human T-cell lines immortalized by Herpesvirus saimiri

Herpesvirus saimiri subgroup-C strains transform non-neoplastic human T lymphocytes in vitro to antigen-independent continuous growth. The karyotypes of 8 of these T-cell lines, derived from peripheral blood or bone marrow, are analyzed here. In general, these lines showed a normal diploid karyotype, although one of them had acquired a clonal chromosomal rearrangement after 21 months in culture. Chromosomally aberrant cell clones were found more frequently in cell lines derived from blood lymphocytes of leukemia patients than in cultures from healthy donors. However, the observed aberrations, some of which were defined in detail using chromosome in situ suppression hybridization (CISS) with chromosome-specific recombinant DNA libraries, did not show any relation between the various cell lines nor to the respective types of leukemia.

A human monoclonal antibody that detects HLA-A1, A23 and A24 antigens

We report the production and characterization of a human monoclonal IgM (mu, kappa) antibody recognizing the HLA A1, A23 and A24 antigens. B lymphocytes obtained from a multiparous Japanese woman were transformed in vitro by Epstein-Barr virus, screened with an immune adherence assay, and fused with a murine myeloma cell line, P3-X63-Ag8.653. After subcloning by limiting dilution three times, a stable antibody-secreting hybridoma cell line, 4-35-7, was identified. The culture supernant had a titer of 1:32-64 against each of A1-, A23- and A24-positive lymphocyte panels, and showed complete correlation (r = 1.00) with the A1, A23 and A24 antigens on a lymphocyte panel of 287 unrelated, class I HLA-typed donors by the NIH cytotoxicity assay. Monoclonality of the antibody was ensured by Southern blot analysis of the human immunoglobulin heavy chain gene of 4-35-7. In view of the published data on HLA class I nucleotide sequences, the antibody may recognize an antigeneic determinant including two amino acid residues, Asp-166 and Gly-167, in the alpha 2 helix of the class I molecule that are specific for A1, A23 and A24 so far analyzed.

GD2 ganglioside on human T-lymphotropic virus type I-infected T cells: possible activation of beta-1,4-N-acetylgalactosaminyltransferase gene by p40tax

Ganglioside expression on adult T-cell leukemia (ATL) and human T-cell lymphotropic virus type I (HTLV-I)-infected cells was determined by using a panel of monoclonal antibodies. ATL lines and HTLV-I-infected cells specifically expressed GD2. Leukemia cells from ATL patients generally expressed low levels of GD2 but the percentage of GD2+ cells increased up to 40-70% after in vitro culture in the presence of interleukin 2 for about a week. No other type of leukemia cells and normal peripheral T cells expressed GD2 during in vitro culture under the same conditions. The appearance of GD2 in the cultured ATL cells corresponded with the expression of p40tax, a product of the HTLV-I gene. Peripheral lymphocytes infected with a p40tax-expressing retroviral vector expressed high levels of GD2 in comparison with control lymphocytes containing the neomycin-resistance gene alone. The apparently increased levels of beta-1,4-N-acetylgalactosaminyltransferase (GM2/GD2 synthase) mRNA in these cells were demonstrated by reverse transcription-polymerase chain reaction analysis. Concordance between mRNA expression for the HTLV-I tax1/rex1 genes and the beta-1,4-N-acetylgalactosaminyltransferase gene was also observed in uncultured ATL cells. These results suggest that high GD2 expression was due to neosynthesis from precursor GD3 by increased expression of this enzyme induced by p40tax in vitro and in vivo.