Bahcc1 is critical for the aberrant epigenetic program in a mouse model of MLL-ENL-mediated leukemia.

ABSTRACT: In leukemogenesis, genotoxic stress in hematopoietic stem and progenitor cells (HSPCs) drives individual context-dependent programs of malignant transformation. In light of the various differentiation stages of HSPCs based on a recently revised definition using CD150/CD48, our analyses showed that a subpopulation of long-term repopulating HSCs was most susceptible to MLL-ENL-mediated transformation. An analysis of the molecular mechanism identified Bromo-adjacent homology domain and coiled-coil containing 1 (Bahcc1), which encodes a reader molecule of trimethylated histone H3 lysine 27 (H3K27me3), as a candidate gene involved in distinct susceptibility to leukemic transformation. Interestingly, Bahcc1 was previously reported to be highly expressed in acute myeloid leukemia (AML) with an unfavorable prognosis, including some cases of MLL-rearranged AML. We found that MLL-ENL upregulated Bahcc1 through binding to its promoter, and that Bahcc1 was involved in MLL-ENL-mediated immortalization at least partly through repression of H3K27me3-marked Cdkn1c. Analyses using bone marrow transplantation in mice showed that depletion of Bahcc1 suppressed the leukemogenic activity of MLL-ENL. In a public database, high BAHCC1 expression was found to be associated with a poor prognosis in pediatric AML, in which BAHCC1 expression was significantly lower in MLL-AF9-AML than in other MLL-fusion-AML. These findings shed light on the distinct immortalization potential of HSPCs and suggest a novel MLL-fusion-Bahcc1 axis, which may lead to development of molecular targeted therapy against MLL-fusion-mediated leukemia.

Inhibition of lung microbiota-derived proapoptotic peptides ameliorates acute exacerbation of pulmonary fibrosis.

Idiopathic pulmonary fibrosis is an incurable disease of unknown etiology. Acute exacerbation of idiopathic pulmonary fibrosis is associated with high mortality. Excessive apoptosis of lung epithelial cells occurs in pulmonary fibrosis acute exacerbation. We recently identified corisin, a proapoptotic peptide that triggers acute exacerbation of pulmonary fibrosis. Here, we provide insights into the mechanism underlying the processing and release of corisin. Furthermore, we demonstrate that an anticorisin monoclonal antibody ameliorates lung fibrosis by significantly inhibiting acute exacerbation in the human transforming growth factorß1 model and acute lung injury in the bleomycin model. By investigating the impact of the anticorisin monoclonal antibody in a general model of acute lung injury, we further unravel the potential of corisin to impact such diseases. These results underscore the role of corisin in the pathogenesis of acute exacerbation of pulmonary fibrosis and acute lung injury and provide a novel approach to treating this incurable disease.

Non-propagative human parainfluenza virus type 2 nasal vaccine robustly protects the upper and lower airways against SARS-CoV-2.

We developed an intranasal vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using the replication-incompetent human parainfluenza virus type 2 (hPIV2) vector BC-PIV, which can deliver ectopic gene as stable RNA and ectopic protein on the envelope. BC-PIV expressing the full-length prefusion-stabilized spike gene (K986P/V987P) of SARS-CoV-2, S-2PM, possessed a corona-like viral envelope. Intranasal vaccination of mice with BC-PIV/S-2PM induced high levels of neutralizing immunoglobulin G (IgG) and mucosal IgA antibodies against the spike protein. Although BC-PIV showed hemagglutinating activity, BC-PIV/S-2PM lacked such activity, in accordance with the presence of the massive spike protein on the viral surface. Furthermore, single-dose intranasal vaccination of hamsters with BC-PIV/S-2PM completely protected the lungs from SARS-CoV-2 at 11-week post-immunization, and boost vaccination two weeks before the challenge conferred virtually complete protection of the nasal turbinates against SARS-CoV-2. Thus, this chimeric hPIV2/spike intranasal vaccine is a promising vaccine candidate for SARS-CoV-2 to curtail virus transmission.

Tet1 is not required for myeloid leukemogenesis by MLL-ENL in novel mouse models.

The Ten Eleven Translocation 1 (TET1) gene encodes an epigenetic modifying molecule that is involved in demethylation of 5-methylcytosine. In hematological malignancies, loss-of-function mutations of TET2, which is one of the TET family genes including TET1, are frequently found, while the mutations of TET1 are not. However, clinical studies have revealed that TET1 is highly expressed in some cases of the hematological malignancies including acute myeloid leukemia. Indeed, studies by mouse models using conventional Tet1 knockout mice demonstrated that Tet1 is involved in myeloid leukemogenesis by Mixed Lineage Leukemia (MLL) fusion gene or TET2 mutant. Meanwhile, the other study showed that Tet1 is highly expressed in hematopoietic stem cells (HSCs), and that deletion of Tet1 in HSCs enhances potential self-renewal capacity, which is potentially associated with myeloid leukemogenesis. To examine the role of Tet1 in myeloid leukemogenesis more precisely, we generated novel conditional Tet1-knockout mice, which were used to generate the compound mutant mice by crossing with the inducible MLL-ENL transgenic mice that we developed previously. The leukemic immortalization in vitro was not critically affected by conditional ablation of Tet1 in HSCs with the induced expression of MLL-ENL or in hematopoietic progenitor cells retrovirally transduced with MLL-ENL. In addition, the leukemic phenotypes caused by the induced expression of MLL-ENL in vivo was not also critically affected in the compound mutant mouse model by conditional ablation of Tet1, although we found that the expression of Evi1, which is one of critical target genes of MLL fusion gene, in tumor cells was remarkably low under Tet1-ablated condition. These results revealed that Tet1 was dispensable for the myeloid leukemogenesis by MLL-ENL, suggesting that the therapeutic application of Tet1 inhibition may need careful assessment.

Genetic polymorphisms and vincristine-induced peripheral neuropathy in patients treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone therapy.

Vincristine (VCR)-induced peripheral neuropathy (VIPN) is a common and life-long toxicity in lymphoma patients receiving current standard chemotherapy. The association between VIPN and genetic polymorphisms is largely unknown in adult lymphoma patients. To examine the possible relationship between known genetic polymorphisms in patients with pediatric acute lymphoblastic leukemia and incidence of VIPN in adult patients with B cell lymphoma, we examined CEP72 rs924607, ETAA1 rs17032980, MTNR1B rs12786200, CYP3A5 rs776746, rs7963521, and rs1045644 genetic polymorphisms in samples from 56 adult patients with B-cell lymphoma who received rituximab, cyclophosphamide, doxorubicin, VCR, and prednisone (R-CHOP) chemotherapy. Mutation analysis was performed by direct sequencing. The median age was 65 years (range 30-79). The median cumulative dose of VCR was 12 mg (range 2-16). VIPN was documented in 42 patients (75%), and 9 (16%) had grade 2-4 VIPN. Age, impaired glucose tolerance, number of cycles of R-CHOP, and VCR cumulative dose were not associated with incidence of VIPN. There was no association between the incidence of grade 2-4 or any grade VIPN and these six genetic polymorphisms. These results indicate that CEP72, MTNR1B, ETAA1, CYP3A5, rs7963521, and rs1045644 genetic polymorphisms are not associated with VIPN in patients with B-cell lymphoma who received R-CHOP.

Eya2 is critical for the E2A­HLF­mediated immortalization of mouse hematopoietic stem/progenitor cells.

The immunoglobulin enhancer­binding factor/hepatic leukemia factor (E2A­HLF) oncogenic fusion gene, generated by t(17;19)(q22;p13) translocation in childhood B­cell acute lymphoblastic leukemia with a very poor prognosis, encodes a chimeric transcription factor in which the transactivation domains of E2A are fused to the DNA­binding and dimerization domain of HLF. E2A­HLF has been demonstrated to have an anti­apoptotic effect. However, the molecular mechanism underlying E2A­HLF­mediated leukemogenesis remains unclear. The present study identified EYA transcriptional coactivator and phosphatase 2 (Eya2), the forced expression of which is known to immortalize mouse hematopoietic stem/progenitor cells (HSPCs), as a direct target molecule downstream of E2A­HLF. E2A­HLF­immortalized mouse HSPCs expressed Eya2 at a high level in the aberrant self­renewal program. Chromatin immunoprecipitation­quantitative polymerase chain reaction and a reporter assay revealed that E2A­HLF enhanced the Eya2 expression by binding to the promoter region containing the E2A­HLF­binding consensus sequence. Eya2 knockdown in E2A­HLF­immortalized cells resulted in reduced colony­forming efficiency. These results suggest a critical role of Eya2 in E2A­HLF­mediated leukemogenesis.

Eya2, a Target Activated by Plzf, Is Critical for PLZF-RARA-Induced Leukemogenesis.

PLZF is a transcription factor that confers aberrant self-renewal in leukemogenesis, and the PLZF-RARA fusion gene causes acute promyelocytic leukemia (APL) through differentiation block. However, the molecular mechanisms of aberrant self-renewal underlying PLZF-mediated leukemogenesis are poorly understood. To investigate these mechanisms, comprehensive expression profiling of mouse hematopoietic stem/progenitor cells transduced with Plzf was performed, which revealed the involvement of a key transcriptional coactivator, Eya2, a target molecule shared by Plzf and PLZF-RARA, in the aberrant self-renewal. Indeed, PLZF-RARA as well as Plzf rendered those cells immortalized through upregulation of Eya2. Eya2 also led to immortalization without differentiation block, while depletion of Eya2 suppressed clonogenicity in cells immortalized by PLZF-RARA without influence on differentiation and apoptosis. Interestingly, cancer outlier profile analysis of human samples of acute myeloid leukemia (AML) in The Cancer Genome Atlas (TCGA) revealed a subtype of AML that strongly expressed EYA2 In addition, gene set enrichment analysis of human AML samples, including TCGA data, showed that this subtype of AML was more closely associated with the properties of leukemic stem cells in its gene expression signature than other AMLs. Therefore, EYA2 may be a target for molecular therapy in this subtype of AML, including PLZF-RARA APL.

MYD88, CD79B, and CARD11 gene mutations in CD5-positive diffuse large B-cell lymphoma.

BACKGROUND: CD5-positive (CD5+ ) diffuse large B-cell lymphoma (DLBCL) is characterized by frequent central nervous system recurrence and a predominant activated B-cell-like nature. Primary DLBCL in sanctuary sites (DLBCL-SS) also demonstrates these features, and >70% of patients harbor myeloid differentiation primary response 88 (MYD88) (L265P) and CD79B mutations. The objective of the current study was to elucidate a possible relationship between CD5+ DLBCL and DLBCL-SS. METHODS: MYD88, CD79B, CD79A, and caspase recruitment domain family member 11 (CARD11) mutations were examined in samples from 40 patients with CD5+ DLBCL. Mutation analysis was performed by direct sequencing. RESULTS: MYD88 and CD79B mutations were detected in 33% (13 patients) and 38% (15 patients), respectively, of the 40 patients with CD5+ DLBCL. Ten patients had these 2 gene mutations, and 1 had a CD79A mutation. One of 2 patients with testicular involvement had both MYD88 and CD79B mutations. The other patient had a MYD88 mutation alone. None of the 31 patients examined was found to have a CARD11 mutation. MYD88 and CD79B mutations were found to be associated with localized disease (P = .038 and P = .003, respectively). Primary extranodal lymphoma was associated with higher frequencies of mutations in MYD88 or both MYD88 and CD79B (P = .008 and P = .014, respectively). There was no significant difference in overall survival based on MYD88 and CD79B mutation status. CONCLUSIONS: The incidence of MYD88 and CD79B mutations in patients with CD5+ DLBCL is lower than that in patients with DLBCL-SS, suggesting that CD5+ DLBCL is not the same disease as DLBCL-SS in terms of gene mutation status. CARD11 mutations are rare in patients with CD5+ DLBCL. Cancer 2017;123:1166-1173. © 2016 American Cancer Society.

Expressions of SH3BP5, LMO3, and SNAP25 in diffuse large B-cell lymphoma cells and their association with clinical features.

Diffuse large B-cell lymphoma (DLBCL) is clinicopathologically and genetically heterogeneous with variable clinical outcomes. We previously identified signature genes overexpressed in CD5-positive (CD5(+) ) DLBCL, which is a poor prognostic subgroup of DLBCL. To elucidate the clinical significance of the protein expression of the signature genes overexpressed in CD5(+) DLBCL with regard to all DLBCL, not otherwise specified (NOS), 10 genes (SH3BP5, LMO3, SNAP25, SYT5, SV2C, CABP1, FGF1, FGFR2, NEUROD1, and SYN2) were selected and examined immunohistochemically with samples from 28 patients with DLBCL, NOS. Only three protein expressions, SH3BP5, LMO3, and SNAP25, were detected in DLBCL cells and then analyzed further with samples from 187 patients with DLBCL, NOS. The SH3BP5, LMO3, and SNAP25 proteins were expressed in 60% (103/173), 34% (59/175), and 46% (77/168) of DLBCL patients, respectively. These protein expressions were associated with CD5 expression, and only SH3BP5 was frequently expressed in activated B-cell-like DLBCL (P = 0.046). Compared to the SH3BP5-negative group, the SH3BP5(+) group was correlated with elderly onset (>60 years, P = 0.0096) and advanced-stage disease (stage III/IV, P = 0.037). The LMO3(+) group showed a worse performance status (>1, P = 0.0004). The SH3BP5(+) group and the LMO3(+) group had significantly worse overall survival than the negative groups (P = 0.030, 0.034; respectively) for the entire group. In a subgroup analysis of patients treated with rituximab-containing chemotherapy, there was no significant difference between groups. To the best of our knowledge, this is the first report showing the protein expressions of SH3BP5, LMO3, and SNAP25 in DLBCL cells and their clinical significance in patients with DLBCL. The SH3BP5 and LMO3 protein expressions are associated with the baseline clinical characteristics of DLBCL.

Novel working hypothesis for pathogenesis of hematological malignancies: combination of mutations-induced cellular phenotypes determines the disease (cMIP-DD).

Recent progress in high-speed sequencing technology has revealed that tumors harbor novel mutations in a variety of genes including those for molecules involved in epigenetics and splicing, some of which were not categorized to previously thought malignancy-related genes. However, despite thorough identification of mutations in solid tumors and hematological malignancies, how these mutations induce cell transformation still remains elusive. In addition, each tumor usually contains multiple mutations or sometimes consists of multiple clones, which makes functional analysis difficult. Fifteen years ago, it was proposed that combination of two types of mutations induce acute leukemia; Class I mutations induce cell growth or inhibit apoptosis while class II mutations block differentiation, co-operating in inducing acute leukemia. This notion has been proven using a variety of mouse models, however most of recently found mutations are not typical class I/II mutations. Although some novel mutations have been found to functionally work as class I or II mutation in leukemogenesis, the classical class I/II theory seems to be too simple to explain the whole story. We here overview the molecular basis of hematological malignancies based on clinical and experimental results, and propose a new working hypothesis for leukemogenesis.

Plzf drives MLL-fusion-mediated leukemogenesis specifically in long-term hematopoietic stem cells.

Oncogenic transformation requires unlimited self-renewal. Currently, it remains unclear whether a normal capacity for self-renewal is required for acquiring an aberrant self-renewal capacity. Our results in a new conditional transgenic mouse showed that a mixed lineage leukemia (MLL) fusion oncogene, MLL-ENL, at an endogenous-like expression level led to leukemic transformation selectively in a restricted subpopulation of hematopoietic stem cells (HSCs) through upregulation of promyelocytic leukemia zinc finger (Plzf). Interestingly, forced expression of Plzf itself immortalized HSCs and myeloid progenitors in vitro without upregulation of Hoxa9/Meis1, which are well-known targets of MLL fusion proteins, whereas its mutant lacking the BTB/POZ domain did not. In contrast, depletion of Plzf suppressed the MLL-fusion-induced leukemic transformation of HSCs in vitro and in vivo. Gene expression analyses of human clinical samples showed that a subtype of PLZF-high MLL-rearranged myeloid leukemia cells was closely associated with the gene expression signature of HSCs. These findings suggested that MLL fusion protein enhances the self-renewal potential of normal HSCs to develop leukemia, in part through a Plzf-driven self-renewal program.

Cynomolgus monkey induced pluripotent stem cells established by using exogenous genes derived from the same monkey species.

Induced pluripotent stem (iPS) cells established by introduction of the transgenes POU5F1 (also known as Oct3/4), SOX2, KLF4 and c-MYC have competence similar to embryonic stem (ES) cells. iPS cells generated from cynomolgus monkey somatic cells by using genes taken from the same species would be a particularly important resource, since various biomedical investigations, including studies on the safety and efficacy of drugs, medical technology development, and research resource development, have been performed using cynomolgus monkeys. In addition, the use of xenogeneic genes would cause complicating matters such as immune responses when they are expressed. In this study, therefore, we established iPS cells by infecting cells from the fetal liver and newborn skin with amphotropic retroviral vectors containing cDNAs for the cynomolgus monkey genes of POU5F1, SOX2, KLF4 and c-MYC. Flat colonies consisting of cells with large nuclei, similar to those in other primate ES cell lines, appeared and were stably maintained. These cell lines had normal chromosome numbers, expressed pluripotency markers and formed teratomas. We thus generated cynomolgus monkey iPS cell lines without the introduction of ecotropic retroviral receptors or other additional transgenes by using the four allogeneic transgenes. This may enable detailed analysis of the mechanisms underlying the reprogramming. In conclusion, we showed that iPS cells could be derived from cynomolgus monkey somatic cells. To the best of our knowledge, this is the first report on iPS cell lines established from cynomolgus monkey somatic cells by using genes from the same species.

Manipulation of human early T lymphopoiesis by coculture on human bone marrow stromal cells: potential utility for adoptive immunotherapy.

T cell precursors are an attractive target for adoptive immunotherapy. We examined the regulation of human early T lymphopoiesis by human bone marrow stromal cells to explore in vitro manipulation of human T cell precursors in a human-only coculture system. The generation of CD7(+)CD56(-)cyCD3(-) proT cells from human hematopoietic progenitors on telomerized human bone marrow stromal cells was enhanced by stem cell factor, flt3 ligand, and thrombopoietin, but these stimulatory effects were suppressed by interleukin 3. Expression of Notch ligands Delta-1 and -4 on stromal cells additively promoted T cell differentiation into the CD7(+)cyCD3(+) pre-T cell stage, while cell growth was strongly inhibited. By combining these coculture systems, we found that initial coculture with telomerized stromal cells in the presence of stem cell factor, flt3 ligand, and thrombopoietin, followed by coculture on Delta-1- and -4-coexpressing stromal cells led to a higher percentage and number of pre-T cells. Adoptive immunotherapy using peripheral blood T cells transduced with a tumor antigen-specific T cell receptor (TCR) is a promising strategy but has several limitations, such as the risk of forming a chimeric TCR with the endogenous TCR. We demonstrated that incubation of TCR-transduced hematopoietic progenitors with the combination of coculture systems gave rise to CD7(+)TCR(+)CD3(+)CD1a(-) T cell precursors that rapidly proliferated and differentiated under the culture condition to induce mature T cell differentiation. These data show the regulatory mechanism of early T lymphopoiesis on human stromal cells and the potential utility of engineered human stromal cells to manipulate early T cell development for clinical application.

IKAROS isoform 6 enhances BCR-ABL1-mediated proliferation of human CD34+ hematopoietic cells on stromal cells.

The BCR-ABL1 induces chronic myelogenous leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL). Recent studies revealed high ratios of loss of the IKZF1 gene which encodes IKAROS in BCR-ABL1+ ALL and lymphoblastic crisis (LBC) of CML. However, little is known about the cooperativity between the aberrant IKAROS and BCR-ABL1 in primary human hematopoietic cells. We investigated the effects of expression of BCR-ABL1 and/or IK6, a natural dominant negative isoform of IKAROS, on proliferation and differentiation of human CD34+ cord blood cells with or without human bone marrow-derived stromal cells which support early B cell differentiation. Cell proliferation was remarkably enhanced by co-expression of BCR-ABL1 and IK6, with reduced expression of glycophorin A and increased expression of CD41, especially on stromal cells, compared with expression of BCR-ABL1 alone that resulted in expansion of erythroid progenitors. Interestingly, p190BCR-ABL1 showed higher dependency on stromal cells to stimulate cell growth with IK6, than p210BCR-ABL1. Furthermore, the cooperation was found to depend on direct cell adhesive interaction of hematopoietic progenitors with stromal cells. These findings suggest that IK6 and BCR-ABL1 synergistically contribute to leukemogenesis in human bone marrow stromal microenvironment, and may provide a clue to elucidate the mechanisms of leukemogenesis of Ph+ ALL and CML-LBC.

FLT3-ITD induces ara-C resistance in myeloid leukemic cells through the repression of the ENT1 expression.

Fms-related tyrosine kinase 3-internal tandem duplications (FLT3-ITD) are strongly associated with the refractory nature of acute myeloid leukemia (AML) by the standard combined chemotherapy. FLT3-ITD-expressing murine and human myeloid cell lines, HF6/FLT3-ITD and K562/FLT3-ITD cells, respectively, were developed in order to clarify whether FLT3-ITD is involved in the resistance to cytotoxic agents in AML. Both of these cell lines were specifically resistant to the pyrimidine analogue cytosine arabinoside (ara-C), an essential agent for AML, accompanied by the downregulation of equilibrative nucleoside transporter 1 (ENT1), a transporter responsible for the cellular uptake of ara-C. The ENT1 promoter activity and the cellular uptake of ara-C were reduced in K562/FLT3-ITD cells, and rescued by pretreating the cells with PKC412, a FLT3 inhibitor. In addition, the expression of hypoxia inducible factor 1 alpha subunit (HIF1A) transcripts was upregulated in K562/FLT3-ITD cells, and the induction of HIF-1alpha reduced the promoter activity of ENT1 gene in K562 cells. Taken together, these findings suggest that FLT3-ITD specifically induces ara-C resistance in leukemic cells by the repression of ENT1 expression, possibly through the upregulation of HIF-1alpha, while also partially accounting for the poor prognosis of AML with FLT3-ITD due to resistance to the standard chemotherapy protocols which include ara-C.

Possible involvement of RasGRP4 in leukemogenesis.

It is now conceivable that leukemogenesis requires two types of mutations, class I and class II mutations. We previously established a mouse bone marrow-derived HF6, an IL-3-dependent cell line, that was immortalized by a class II mutation MLL/SEPT6 and can be fully transformed by class I mutations such as FLT3 mutants. To understand the molecular mechanism of leukemogenesis, particularly progression of myelodysplastic syndrome (MDS) to acute leukemia, we made cDNA libraries from the samples of patients and screened them by expression-cloning to detect class I mutations that render HF6 cells factor-independent. We identified RasGRP4, an activator of Ras, as a candidate for class I mutation from three of six patients (MDS/MPD = 1, MDS-RA = 1, MDS/AML = 2, CMMoL/AML = 1 and AML-M2 = 1). To investigate the potential roles of RasGRP4 in leukemogenesis, we tested its in vivo effect in a mouse bone marrow transplantation (BMT) model. C57BL/6J mice transplanted with RasGRP4-transduced primary bone marrow cells died of T cell leukemia, myeloid leukemia, or myeloid leukemia with T cell leukemia. To further examine if the combination of class I and class II mutations accelerated leukemic transformation, we performed a mouse BMT model in which both AML1 mutant (S291fsX300) and RasGRP4 were transduced into bone marrow cells. The double transduction led to early onset of T cell leukemia but not of AML in the transplanted mice when compared to transduction of RasGRP4 alone. Thus, we have identified RasGRP4 as a gene potentially involved in leukemogenesis and suggest that RasGRP4 cooperates with AML1 mutations in T cell leukemogenesis as a class I mutation.

AML1 mutations induced MDS and MDS/AML in a mouse BMT model.

Myelodysplastic syndrome (MDS) is a hematopoietic stem-cell disorder characterized by trilineage dysplasia and susceptibility to acute myelogenous leukemia (AML). Analysis of molecular basis of MDS has been hampered by the heterogeneity of the disease. Recently, mutations of the transcription factor AML1/RUNX1 have been identified in 15% to 40% of MDS-refractory anemia with excess of blasts (RAEB) and MDS/AML. We performed mouse bone marrow transplantation (BMT) using bone marrow cells transduced with the AML1 mutants. Most mice developed MDS and MDS/AML-like symptoms within 4 to 13 months after BMT. Interestingly, among integration sites identified, Evi1 seemed to collaborate with an AML1 mutant harboring a point mutation in the Runt homology domain (D171N) to induce MDS/AML with an identical phenotype characterized by marked hepatosplenomegaly, myeloid dysplasia, leukocytosis, and biphenotypic surface markers. Collaboration between AML1-D171N and Evi1 was confirmed by a BMT model where coexpression of AML1-D171N and Evi1 induced acute leukemia of the same phenotype with much shorter latencies. On the other hand, a C-terminal truncated AML1 mutant (S291fsX300) induced pancytopenia with erythroid dysplasia in transplanted mice, followed by progression to MDS-RAEB or MDS/AML. Thus, we have developed a useful mouse model of MDS/AML that should help in the understanding of the molecular basis of MDS and the progression of MDS to overt leukemia.

Disruption of Sept6, a fusion partner gene of MLL, does not affect ontogeny, leukemogenesis induced by MLL-SEPT6, or phenotype induced by the loss of Sept4.

Septins are evolutionarily conserved GTP-binding proteins that can heteropolymerize into filaments. Recent studies have revealed that septins are involved in not only diverse normal cellular processes but also the pathogenesis of various diseases, including cancer. SEPT6 is ubiquitously expressed in tissues and one of the fusion partner genes of MLL in the 11q23 translocations implicated in acute leukemia. However, the roles of this septin in vivo remain elusive. We have developed Sept6-deficient mice that exhibited neither gross abnormalities, changes in cytokinesis, nor spontaneous malignancy. Sept6 deficiency did not cause any quantitative changes in any of the septins evaluated in this study, nor did it cause any additional changes in the Sept4-deficient mice. Even the depletion of Sept11, a close homolog of Sept6, did not affect the Sept6-null cells in vitro, thus implying a high degree of redundancy in the septin system. Furthermore, a loss of Sept6 did not alter the phenotype of myeloproliferative disease induced by MLL-SEPT6, thus suggesting that Sept6 does not function as a tumor suppressor. To our knowledge, this is the first report demonstrating that a disruption of the translocation partner gene of MLL in 11q23 translocation does not contribute to leukemogenesis by the MLL fusion gene.

A simple X-ray emitter.

A compact X-ray emission instrument is made, and the X-ray spectra are measured by changing the applied electric potential. Strong soft X-rays are observed when evacuating roughly and applying a high voltage to an insulator settled in this device. The X-ray intensity is higher as the applied voltage is increased. A light-emitting phenomenon is observed when this device emits X-rays. The present X-ray emitter is made of a small cylinder with a radius of 20 mm and a height of 50 mm. This X-ray generator has a potential to be used as an X-ray source in an X-ray fluorescence spectrometer.

Roles of a trithorax group gene, MLL, in hematopoiesis.

The mixed-lineage leukemia (MLL) gene is a trithorax group (trxG) gene that was originally identified at chromosomal translocations in patients developing acute leukemia. Although Polycomb group (PcG) genes, which counteract trxG genes, were found to play essential roles in hematopoiesis, little has been understood about the roles of trxG genes in hematopoiesis except for MLL. MLL has been found fused with 1 of more than 30 different partner genes to yield a diverse collection of MLL fusion oncoproteins that lead to the aberrant expression of HOX genes. Recent studies have revealed that MLL assembles, as do some trxG proteins, into a chromatin-modifying transcriptional regulatory supercomplex to regulate epigenetic pathways, including the methylation of histone H3 lysine 4, which is conferred by the Su (var)3-9, enhancer of zeste, and tritho-rax (SET) domain. Other studies also indicated that MLL plays a nonredundant and essential role in definitive hematopoiesis and induces the proliferation and differentiation of hematopoietic progenitors by maintaining appropriate up-regulation of HOX genes. Further progress in the field will provide novel insights into trxG- and PcG-mediated hematopoiesis and help us understand the epigenetic process by which developing stem cells coordinate proliferation and differentiation.