[Show abstract][Hide abstract] ABSTRACT: PAX5 is a transcription factor that is required for the development and maintenance of B cells. PML is a tumor suppressor
and pro-apoptotic factor. The fusion gene, PAX5-PML, has been identified in acute lymphoblastic leukemia (ALL) with chromosomal
translocation t(9;15)(p13;q24). We previously reported that PAX5-PML dominant-negatively inhibited PAX5 transcriptional activity
and impaired PML function by disrupting PML nuclear bodies (NBs). We herein demonstrated the leukemogenicity of PAX5-PML by
introducing it into normal mouse pro B cells. The arrest of differentiation was observed in PAX5-PML-introduced pro B cells,
resulting in the development of ALL after a long latency in mice. Among the transactivation targets of PAX5, BLNK was selectively
repressed in leukemia cells and enforced BLNK expression abrogated differentiation block induced by PAX5-PML, indicating the
importance of BLNK repression for the differentiation block. We also showed that PML NBs were intact in leukemia cells and
attributed this to the low expression of PAX5-PML, indicating that the disruption of PML NBs was not required for the PAX5-PML-induced
onset of leukemia. These results provide novel insights into the molecular mechanisms underlying the onset of leukemia by
Preview · Article · Dec 2015 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: Peripheral T-cell lymphomas (PTCLs) are a heterogeneous group of non-Hodgkin lymphomas with poor prognosis and their molecular pathogenesis has not been entirely elucidated. We previously showed that 6q24 is one of the most frequently deleted regions in primary thyroid T-cell lymphoma. In this study, we extended the analysis to other subtypes of PTCLs and performed functional assays to identify the causative genes of PTCLs that are located on 6q24. Genomic loss of 6q24 was observed in 14 of 232 (6%) PTCL cases. The genomic loss regions identified at 6q24 always involved only two known genes, STX11 and UTRN. The expression of STX11, but not UTRN, was substantially lower in PTCLs than in normal T-cells. STX11 sequence analysis revealed mutations in 2 cases (one clinical sample and one T-cell line). We further analyzed the function of STX11 in 14 cell lines belonging to different lineages. STX11 expression only suppressed the proliferation of T-cell lines bearing genomic alterations at the STX11 locus. Interestingly, expression of a novel STX11 mutant (p.Arg78Cys) did not exert suppressive effects on the induced cell lines, suggesting that this mutant is a loss-of-function mutation. Additionally, STX11-altered PTCL not otherwise specified cases were characterized by presence of hemophagocytic syndrome (67% versus 8%, P = 0.04). They also tended to have a poor prognosis compared with those without STX11 alteration. These results suggest that STX11 plays an important role in the pathogenesis of PTCLs and they may contribute to the future development of new drugs for the treatment of PTCLs. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Leukemia is one of the leading journals in hematology and oncology. It is published monthly and covers all aspects of the research and treatment of leukemia and allied diseases. Studies of normal hemopoiesis are covered because of their comparative relevance.
[Show abstract][Hide abstract] ABSTRACT: Clonal heterogeneity in lymphoid malignancies has been recently reported in adult T-Cell lymphoma/leukemia, peripheral T-cell lymphoma, not otherwise specified, and mantle cell lymphoma. Our analysis was extended to other types of lymphoma including marginal zone lymphoma, follicular lymphoma, and diffuse large B-cell lymphoma. To determine the presence of clonal heterogeneity, 332 cases were examined using array comparative genomic hybridization analysis. Results showed that incidence of clonal heterogeneity varied from 25% to 69% among different types of lymphoma. Survival analysis revealed that mantle cell lymphoma and diffuse large B-cell lymphoma with clonal heterogeneity showed significantly poorer prognosis, and that clonal heterogeneity was confirmed as an independent predictor of poor prognosis for both types of lymphoma. Interestingly, 8q24.1 (MYC) gain, 9p21.3 (CDKN2A/ 2B) loss, and 17p13 (TP53, ATP1B2, SAT2, SHBG) loss were recurrent genomic lesions among various types of lymphoma with clonal heterogeneity, suggesting at least in part that alterations of these genes may play a role in clonal heterogeneity. This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Epstein-Barr virus (EBV) positive diffuse large B-cell lymphoma (DLBCL) of the elderly [EBV(+)DLBCL-E] is classified as a subtype of DLBCL. Until now, its molecular pathogenesis remained unknown. To identify pathways characteristic of EBV(+)DLBCL-E, gene expression profiling of five EBV(+)DLBCL-E and seven EBV-negative DLBCL [EBV(-)DLBCL] cases was undertaken using human oligonucleotide microarray analysis. Gene set enrichment analysis and gene ontology analysis showed that gene sets of the JAK-STAT and NF-κB pathways were enriched in EBV(+)DLBCL-E cases. To confirm the results of the expression profiles, in vitro analysis was performed. Expression profiling analysis showed that high activation of JAK-STAT and NF-κB pathways was induced by EBV infection into DLBCL cell lines. Activation of the NF-κB pathway was confirmed in EBV-infected cell lines using an electrophoretic mobility shift assay. Western blot analysis revealed an increased protein expression level of phosphorylated STAT3 in an EBV-infected cell line. Protein expression of phospho-STAT3 was frequently observed in lymphoma cells of EBV(+)DLBCL-E clinical samples using immunohistochemistry [EBV(+)DLBCL-E: 80.0% (n=20/25) vs.
38.9% (n=14/36), p=0.001]. The results of the present study suggested that activation of JAK-STAT and NF-κB pathways was characteristic of EBV(+)DLBCL-E, which may reflect the nature of EBV-positive tumor cells. Targeting these pathways as therapies might improve clinical outcomes of EBV(+)DLBCL-E. This article is protected by copyright. All rights reserved.
[Show abstract][Hide abstract] ABSTRACT: Patients in the chronic phase (CP) of chronic myelogenous leukemia (CML) have been treated successfully following the advent of ABL kinase inhibitors, but once they progress to the blast crisis (BC) phase the prognosis becomes dismal. Although mechanisms underlying the progression are largely unknown, recent studies revealed the presence of alterations of key molecules for hematopoiesis, such as AML1/RUNX1. Our analysis of 13 BC cases revealed that three cases had AML1 mutations and the transcript levels of wild-type (wt.) AML1 were elevated in BC compared with CP. Functional analysis of representative AML1 mutants using mouse hematopoietic cells revealed the possible contribution of some, but not all, mutants for the BC-phenotype. Specifically, K83Q and R139G, but neither R80C nor D171N mutants, conferred upon BCR-ABL-expressing cells a growth advantage over BCR-ABL-alone control cells in cytokine-free culture, and the cells thus grown killed mice upon intravenous transfer. Unexpectedly, wt.AML1 behaved similarly to K83Q and R139G mutants. In a bone marrow transplantation assay, K83Q and wt.AML1s induced the emergence of blast-like cells. The overall findings suggest the roles of altered functions of AML1 imposed by some, but not all, mutants, and the elevated expression of wt.AML1 for the disease progression of CML.
[Show abstract][Hide abstract] ABSTRACT: Evidence is accumulating that hematological malignancies develop following acquisition of multiple genetic changes. Despite providing many insights into the way by which given genetic changes contribute to the development of disease, the generation of animal models is often laborious. Here we show a simplified method that allows the retroviral transduction of genes of interest into mouse B or T cells, thus leading to the rapid generation of models of lymphoid neoplasm in mice. Specifically, germinal center B cells induced in vitro from naïve mouse B cells and infected with retroviruses for Myc and Bcl2 rapidly developed a neoplasm of immunoglobulin-expressing mature B cells in transplanted mice. Likewise, T cells induced in vitro from immature hematopoietic cells and infected with retroviruses for Myc, Bcl2 and Ccnd1 rapidly developed CD4+CD8- and CD4+CD8+ T cell neoplasm in transplanted mice. These findings support the utility of our simplified method as a versatile tool for lymphoma research.
No preview · Article · Apr 2013 · Experimental hematology
[Show abstract][Hide abstract] ABSTRACT: The initial steps involved in the pathogenesis of acute leukemia are poorly understood. The TEL-AML1 fusion gene usually arises before birth, producing a persistent and covert preleukemic clone that may convert to precursor B cell leukemia following the accumulation of secondary genetic "hits". Here we show that TEL-AML1 can induce persistent self-renewing pro-B cells in mice. TEL-AML1+ cells nevertheless differentiate terminally in the long term, providing a "window" period that may allow secondary genetic "hits" to accumulate and lead to leukemia. TEL-AML1-mediated self-renewal is associated with a transcriptional program shared with embryonic stem cells (ESCs), within which Mybl2, Tgif2, Pim2 and Hmgb3 are critical and sufficient components to establish self-renewing pro-B cells. We further show that TEL-AML1 increases the number of leukemia-initiating cells that are generated in collaboration with additional genetic "hits", thus providing an overall basis for the development of novel therapeutic and preventive measures targeting the TEL-AML1-associated transcriptional program.
[Show abstract][Hide abstract] ABSTRACT: NK cell neoplasms are lymphoid malignancies with an aggressive clinical course. In the present study, we analyzed gene expression profiling of NK cell neoplasms and attempted to identify important molecular pathways and new effective drugs. Pathway analysis of gene expression profiles suggested the important roles of the JAK-STAT pathway, NF-B pathway or Wnt pathways in NK cell neoplasms. Notably, western blot analysis revealed that STAT3 was expressed and phosphorylated at a higher level in NK cell lines than in normal NK cells or other cell lines. These findings indicate the occurrence of JAK-STAT activation in NK cell neoplasms. Connectivity map (CMAP) analysis of gene expression profiles identified candidate drugs against NK cell neoplasms. Among the drugs suggested by CMAP analysis, we focused on puromycin, phenoxybenzamine, LY294002, wortmannin, vorinostat and trichostatin A because they exhibited high enrichment scores. We added these drugs to NK cell lines and other cell lines. Among the drugs, vorinostat suppressed NK cell line proliferation at a significantly lower concentration compared to other cell lines. Suppression of the JAK-STAT pathway appeared to contribute to this effect. Vorinostat may be a good candidate for use in the therapy against NK cell neoplasms.
[Show abstract][Hide abstract] ABSTRACT: Peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS) with genomic aberrations has been shown to resemble lymphoma-type adult T-cell leukemia/lymphoma (ATLL) in terms of its genomic aberration patterns, histopathology, and prognosis. We have shown recently that a majority of patients with acute-type ATLL have multiple subclones that were likely produced in lymph nodes. In this study, we analyzed whether PTCL, NOS with genomic aberrations also has multiple subclones as found in ATLL by means of high-resolution oligo-array comparative genomic hybridization (CGH). Thirteen cases of PTCL, NOS were available for 44K high-resolution array CGH analysis. The results showed that 11 (84.6%) of the 13 cases had a log2 ratio imbalance, suggesting that multiple subclones exist in PTCL, NOS with genomic aberrations. In order to analyze the association between multiple subclones and prognosis, we used previous bacterial-artificial chromosome (BAC) array analyses for 29 cases and found that the existence of multiple subclones was associated with a poor prognosis (P = 0.0279).
[Show abstract][Hide abstract] ABSTRACT: FOXO3 and PRDM1 are located on 6q21, one of the most frequently deleted regions among natural killer (NK) cell neoplasms. We previously demonstrated that forced expression of each gene suppresses the proliferation of NK cell lines with the 6q deletion. In this study, the forced expression of FOXO3 or PRDM1 was performed in various cell lines to clarify these suppressive effects. Forced expression of PRDM1 suppressed the proliferation of not only NK cell lines, but also other broad lineage cell lines. On the other hand, forced expression of FOXO3 was only effective on NK cell lines. FOXO3 functions as a transcriptional factor when it is localized in nuclei. Akt is known to induce cytoplasmic localization of FOXO3 as a result of phosphorylation. Transduced FOXO3 was predominantly localized in nuclei of NK cell lines, while it was localized in the cytoplasm of all non-NK cell lines. NK cell lines showed significantly lower Akt activity compared to other lineage cell lines. The low Akt activity and nucleic localization of FOXO3 in NK cell neoplasms seemed to cause NK cell-specific suppression. These findings indicate the "functional lineage specificity" of FOXO3 and the possibility for NK cell-specific gene therapy with minimal unexpected effects.
No preview · Article · Aug 2012 · Experimental hematology
[Show abstract][Hide abstract] ABSTRACT: Constitutive nuclear factor-kappa B (NF-κB) activation has been reported in ocular adnexal lymphoma (OAL). TNFAIP3/A20 is a "global" inhibitor of NF-κB pathway. We have shown that OAL has preferential loss of the 6q23.3 region where TNFAIP3/A20 exist, which is suggested to involve in lymphomagenesis of OAL. The mechanisms causing NF-κB activity in OAL remain elusive. Recently, NF-κB canonical pathway genes including CARD11, CD79B and MYD88 were shown to be frequently mutated in diffuse large B-cell lymphomas. In this study, we analyzed the mutation status of these genes by direct sequencing in 24 OAL cases including 9 cases with loss of 6q23.3 previously identified by array comparative genomic hybridization. We showed that genetic alterations of these genes were not found in OAL, a finding differing from that of most B-cell lymphomas. Genetic or epigenetic alterations in other genes are likely to be relevant in pathogenesis of OAL case without A20 loss.
Full-text · Article · Jul 2012 · International journal of clinical and experimental pathology
[Show abstract][Hide abstract] ABSTRACT: Self-renewal activity is essential for the maintenance and regeneration of the hematopoietic system. The search for molecules capable of promoting self-renewal and expanding hematopoietic stem cells (HSCs) has met with limited success. Here, we show that a short isoform (AML1a) of RUNX1/AML1 has such activities. Enforced AML1a expression expanded functionally defined HSCs, with an efficiency that was at least 20 times greater than that of the control in vivo and by 18-fold within 7 days ex vivo. The ex vivo-expanded HSCs could repopulate hosts after secondary transplantations. Moreover, AML1a expression resulted in vigorous and long-term (> 10(6)-fold at 4 weeks) ex vivo expansion of progenitor cell populations capable of differentiating into multilineages. Gene expression analysis revealed that AML1a expression was associated with up-regulation of genes, including Hoxa9, Meis1, Stat1, and Ski. shRNA-mediated silencing of these genes attenuated AML1a-mediated activities. Overall, these findings establish AML1a as an isoform-specific molecule that can influence several transcriptional regulators associated with HSCs, leading to enhanced self-renewal activity and hematopoietic stem/progenitor cell expansion ex vivo and in vivo. Therefore, the abilities of AML1a may have implications for HSC transplantation and transfusion medicine, given that the effects also can be obtained by cell-penetrating AML1a protein.
[Show abstract][Hide abstract] ABSTRACT: Oligo-array comparative genomic hybridization (CGH) and gene-expression profiling of natural killer (NK)-cell neoplasms were used in an effort to delineate the molecular pathogenesis involved. Oligo-array CGH identified two 6q21 regions that were most frequently deleted (14 of 39 or 36%). One of these regions included POPDC3, PREP, PRDM1, ATG5, and AIM1, whereas the other included LACE1 and FOXO3. All genes located in these regions, except for POPDC3 and AIM1, were down-regulated in neoplastic samples, as determined by gene-expression analysis, and were therefore considered to be candidate tumor-suppressor genes. A20 and HACE1, the well-known tumor-suppressor genes located on 6q21-23, were included as candidate genes because they also demonstrated frequent genomic deletions and down-regulated expression. The Tet-Off NK cell line NKL was subsequently established for functional analyses. Seven candidate genes were transduced into Tet-Off NKL and forced re-expression was induced. Re-expression of FOXO3 and PRDM1 suppressed NKL proliferation, but this was not the case after re-expression of the other genes. This effect was confirmed using another NK cell line, SNK10. Furthermore, genomic analyses detected nonsense mutations of PRDM1 that led to functional inactivation in one cell line and one clinical sample. PRDM1 and FOXO3 are considered to play an important role in the pathogenesis of NK-cell neoplasms.
[Show abstract][Hide abstract] ABSTRACT: A synergistic effect resulting from a combination of BCL2 and MYC or MYC and CCND1 has been implicated in human B-cell lymphomas. Although the identification of other cooperative genes involved is important, our present understanding of such genes remains scant. The objective of this study was to identify the additional cooperative gene(s) associated with BCL2 and MYC or MYC and CCND1. First, we assessed whether Bcl2, Myc and Ccnd1 could cooperate. Next, we developed a synergism-based functional screening method for the identification of other oncogene(s) that act with Bcl2 and Myc.
Growth in culture, colony formation and oncogenicity in vivo were assessed in mouse primary B cells exogenously expressing various combinations of Bcl2, Myc and Ccnd1. For the functional screening, Bcl2- and Myc-expressing primary B cells were infected with a retroviral cDNA library. Inserted cDNA of transformed cells in culture were then identified.
Primary B cells exogenously expressing Bcl2, Myc and Ccnd1 showed factor-independent growth ability, enhanced colony-forming capability and aggressive oncogenicity, unlike the cases observed with the expression of any combination of only two of the genes. We identified CCND3 and NRAS as cooperative genes with Bcl2 and Myc through the functional screening.
Bcl2, Myc and Ccnd1 or Bcl2, Myc and CCND3 synergistically transformed mouse primary B cells into aggressive malignant cells. Our new synergism-based method is useful for the identification of synergistic gene combinations in tumor development, and may expand our systemic understanding of a wide range of cancer-causing elements.
[Show abstract][Hide abstract] ABSTRACT: The Ets-related gene (ERG) located on human chromosome 21 encodes a transcription factor and is thought to be causally related to Down syndrome-associated acute megakaryocytic leukemia in childhood. In clinical adult leukemia, however, increased expression of ERG is indicative of poor prognosis in T-cell acute lymphoblastic leukemia and cytogenetically normal acute myeloid leukemia, although the involvement of ERG in the development of adult leukemia remains elusive. Here, we show that forced expression of ERG in adult BM cells alters differentiation and induces expansion of T and erythroid cells and increases frequencies of myeloid progenitors in mouse BM transplantation models. The expanded T cells then develop T-cell acute lymphoblastic leukemia after acquisition of mutations in the Notch1 gene. Targeted expression of ERG into B cells also altered differentiation and promoted growth of precursor B cells. Overall, these findings suggest a general role of ERG in promoting growth of adult hematopoietic cells in various lineages. In line with this, shRNA-mediated silencing of ERG expression attenuated growth of human leukemia cell lines of various lineages. Thus, ERG is capable of promoting the development of leukemia and is crucial for its maintenance.