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Kinuko Mitani

Publications and source records attributed to Kinuko Mitani.

At least 37 records · Page 2Linked to original sources
PubMed2004

Molecular mechanisms of leukemogenesis by AML1/EVI-1.

The AML1/EVI-1 chimeric gene is generated by the t(3;21)(q26;q22) translocation and plays a pivotal role in progression of hematopoietic stem cell malignancies such as chronic myelocytic leukemia and myelodysplastic syndrome. In AML1/EVI-1, an N-terminal half of AML1 including a runt homology domain is fused to the entire zinc-finger EVI-1 protein. AML1 is essential for hematopoietic cell development in fetal liver and its lineage-specific differentiation in adult. In contrast, EVI-1 is barely expressed in normal hematopoietic cells, but it is overexpressed in chronic myelocytic leukemia in blastic crisis and myelodysplastic syndrome-derived leukemia. There are at least four mechanisms identified in AML1/EVI-1 fusion protein that possibly lead into malignant transformation of hematopoietic stem cells. Firstly, AML1/EVI-1 exerts dominant-negative effects over AML1-induced transcriptional activation. Although target genes repressed by AML1/EVI-1 are still not known, binding competition to a specific DNA sequence and histone deacetylase recruitment through a co-repressor CtBP in EVI-1 part are conceivable underlying mechanisms for the dominant-negative effects. Secondly, AML1/EVI-1 interferes with TGF beta signaling and antagonizes the growth-inhibitory effects of TGF beta. The first zinc-finger domain of EVI-1 associates with Smad3, a TGF beta signal transducer, and represses its transcriptional activity by recruiting histone deacetylase through CtBP that interacts with EVI-1. Thirdly, AML1/EVI-1 blocks JNK activity and prevents stress-induced apoptosis. AML1/EVI-1 associates with JNK through the first zinc-finger domain of EVI-1 and disturbs the association between JNK and its substrates. Lastly, AML1/EVI-1 enhances AP-1 activity by activating the c-Fos promoter depending on the second zinc-finger domain of EVI-1, and promotes cell proliferation. All these functions cooperatively contribute to the malignant transformation of the hematopoietic stem cells by AML1/EVI-1.

Cell Division↗
PubMed2004

Functional analysis of a dominant-negative DeltaETS TEL/ETV6 isoform.

A transcriptional repressor TEL belongs to the ETS family transcription factors and acts as a tumor suppressor. We identified five alternatively spliced TEL isoforms generated possibly through exon skipping mechanisms, by using reverse transcriptase-polymerase chain reaction analysis. Among them, we examined molecular and biological functions of a DeltaETS-TEL isoform (TEL-f). This isoform abrogated specific DNA-binding capacity to and trans-repressional ability through the ETS-binding site. Regardless, it showed dominant-negative effects over wild-type-TEL (TEL-a)-mediated transcriptional repression partly through sequestration of TEL-a from nucleus to cytoplasm. Moreover, TEL-f dominantly interfered with TEL-a-mediated erythroid differentiation in MEL cells and growth suppression in NIH3T3 cells. Interestingly, TEL isoforms without the entire (Delta exons 6+7-TEL) or a part (Delta exon 7-TEL) of ETS domain were expressed more frequently in myelodysplastic syndrome-derived leukemia than in myelodysplastic syndrome before transformation. This observation suggests that accumulation of the dominant-negative DeltaETS-TEL molecules could be a related phenomenon to leukemic progression of myelodysplastic syndrome.

Alternative Splicing↗
PubMed2004

AML-1 is required for megakaryocytic maturation and lymphocytic differentiation, but not for maintenance of hematopoietic stem cells in adult hematopoiesis.

Embryonic development of multilineage hematopoiesis requires the precisely regulated expression of lineage-specific transcription factors, including AML-1 (encoded by Runx1; also known as CBFA-2 or PEBP-2alphaB). In vitro studies and findings in human diseases, including leukemias, myelodysplastic syndromes and familial platelet disorder with predisposition to acute myeloid leukemia (AML), suggest that AML-1 has a pivotal role in adult hematopoiesis. However, this role has not been fully uncovered in vivo because of the embryonic lethality of Runx1 knockout in mice. Here we assess the requirement of AML-1/Runx1 in adult hematopoiesis using an inducible gene-targeting method. In the absence of AML-1, hematopoietic progenitors were fully maintained with normal myeloid cell development. However, AML-1-deficient bone marrow showed inhibition of megakaryocytic maturation, increased hematopoietic progenitor cells and defective T- and B-lymphocyte development. AML-1 is thus required for maturation of megakaryocytes and differentiation of T and B cells, but not for maintenance of hematopoietic stem cells (HSCs) in adult hematopoiesis.

Adult↗
PubMed2004

AML1 is functionally regulated through p300-mediated acetylation on specific lysine residues.

AML1 (RUNX1) is one of the most frequently disrupted genes in human leukemias. AML1 encodes transcription factors, which play a pivotal role in hematopoietic differentiation, and their inappropriate expression is associated with leukemic transformation of hematopoietic cells. Previous studies demonstrated that the transcription cofactor p300 binds to the C-terminal region of AML1 and stimulates AML1-dependent transcription during myeloid cell differentiation. Here, we report that AML1 is specifically acetylated by p300 in vitro. Mutagenesis analyses reveal that p300 acetylates AML1 at the two conserved lysine residues (Lys-24 and Lys-43). AML1 is subject to acetylation at the same sites in vivo, and p300-mediated acetylation significantly augments the DNA binding activity of AML1. Disruption of these two lysines severely impairs DNA binding of AML1 and reduced the transcriptional activity and the transforming potential of AML1. Taken together, these data indicate that acetylation of AML1 through p300 is a critical manner of posttranslational modification and identify a novel mechanism for regulating the function of AML1.

Acetylation↗
PubMed2004

Myelodysplastic syndrome with central diabetes insipidus manifesting hypodipsic hypernatremia and dehydration.

Central diabetes insipidus (DI) is a rare but recognized complication of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) that is caused by leukemic infiltration to the hypothalamo-neurohypophyseal system. In rare patients in whom a wide region of the hypothalamus is involved, central DI results in hypodipsic hypernatremia and dehydration. Typical DI symptoms such as polydipsia, polyuria, and marked thirst are concealed in these cases, because the hypothalamic "thirst center" cannot send thirst stimuli to the cerebral cortex. Herein we describe a patient with MDS developing into AML, who presented with hypodipsic hypernatremia and dehydration. A diagnosis of central DI was made on the ground of a low level of serum anti-diuretic hormone (ADH) despite high serum osmolality. A magnetic resonance imaging study revealed attenuation of a physiological "bright spot" of the neurohypophysis. An induction course chemotherapy including regular-dose cytarabine and daunorubicin produced a rapid improvement of hypernatremia. The bone marrow aspirate after two courses of chemotherapy showed complete remission. At that point, ADH release and the "bright spot" were recovered. In order to correctly diagnose central DI in association with hematological malignancies, we should not overlook this atypical type of DI.

Dehydration↗
PubMed2004

The corepressor mSin3A regulates phosphorylation-induced activation, intranuclear location, and stability of AML1.

The AML1 (RUNX1) gene, one of the most frequent targets of translocations associated with human leukemias, encodes a DNA-binding protein that plays pivotal roles in myeloid differentiation through transcriptional regulation of various genes. Previously, we reported that AML1 is phosphorylated on two serine residues with dependence on activation of extracellular signal-regulated kinase, which positively regulates the transcriptional activity of AML1. Here, we demonstrate that the interaction between AML1 and the corepressor mSin3A is regulated by phosphorylation of AML1 and that release of AML1 from mSin3A induced by phosphorylation activates its transcriptional activity. Furthermore, phosphorylation of AML1 regulates its intranuclear location and disrupts colocalization of AML1 with mSin3A in the nuclear matrix. PEBP2 beta/CBF beta, a heterodimeric partner of AML1, was shown to play a role in protecting AML1 from proteasome-mediated degradation. We show that mSin3A also protects AML1 from proteasome-mediated degradation and that phosphorylation-induced release of AML1 from mSin3A results in degradation of AML1 in a time-dependent manner. This study provides a novel regulatory mechanism for the function of transcription factors mediated by protein modification and interaction with cofactors.

Animals↗
PubMed2004

Leukemia-related transcription factor TEL is negatively regulated through extracellular signal-regulated kinase-induced phosphorylation.

TEL is an ETS family transcription factor that possesses multiple putative mitogen-activated protein kinase phosphorylation sites. We here describe the functional regulation of TEL via ERK pathways. Overexpressed TEL becomes phosphorylated in vivo by activated ERK. TEL is also directly phosphorylated in vitro by ERK. The inducible phosphorylation sites are Ser(213) and Ser(257). TEL binds to a common docking domain in ERK. In vivo ERK-dependent phosphorylation reduces trans-repressional and DNA-binding abilities of TEL for ETS-binding sites. A mutant carrying substituted glutamates on both Ser(213) and Ser(257) functionally mimics hyperphosphorylated TEL and also shows a dominant-negative effect on TEL-induced transcriptional suppression. Losing DNA-binding affinity through phosphorylation but heterodimerizing with unmodified TEL could be an underlying mechanism. Moreover, the glutamate mutant dominantly interferes with TEL-induced erythroid differentiation in MEL cells and growth suppression in NIH 3T3 cells. Finally, endogenous TEL is dephosphorylated in parallel with ERK inactivation in differentiating MEL cells and is phosphorylated through ERK activation in Ras-transformed NIH 3T3 cells. These data indicate that TEL is a constituent downstream of ERK in signal transduction systems and is physiologically regulated by ERK in molecular and biological features.

Animals↗
PubMed2004

[Adult-onset Still disease presenting with disseminated intravascular coagulation].

A 17-year-old female was admitted to our hospital because of pyrexia and thrombocytopenia in May 2002. Laboratory examination showed a platelet count of 50,000/microliter with an increased level of fibrinogen degradation product, leading to a diagnosis of disseminated intravascular coagulation (DIC). Gabexate mesilate was intravenously administrated without any effects. Several days later, erythema, joint pain and neck lymphadenopathy developed sequentially. The patient was diagnosed as having adult-onset Still disease (AOSD) complicated with DIC. Moreover, serum inflammatory cytokine levels had increased and activated macrophages were observed in the bone marrow, suggesting the presence of macrophage activation syndrome. After additional treatments with dalteparin and aspirin, the clinical symptoms and laboratory findings associated with AOSD and DIC disappeared. Although this was a severe case of AOSD associated with preceding DIC, the AOSD symptoms resolved in this patient with the treatment of the DIC and with aspirin only without any relapse.

Adolescent↗
PubMed2004

[Autologous peripheral blood stem cell transplantation for Japanese multiple myeloma patients: results of a feasibility study].

A feasibility study on high-dose therapy with autologous peripheral blood stem cell transplantation (HDT/PBSCT) was performed in Japanese patients with multiple myeloma (MM). Twenty evaluable patients younger than 65 years old with stage II/III MM were enrolled in this study. Three courses of VAD were used as initial chemotherapy. High-dose etoposide or cyclophosphamide followed by G-CSF was used for PBSCH, and 1.2-89.3 (median 23.4) x 106/kg of CD34+ cells were collected. Single (11 patients) or tandem (9 patients) HDT with melphalan (MEL) 200 mg/m2 or MEL 140 mg/m2 plus TBI 10 Gy were performed. The incidence of grade 4 toxicity (COG) was 10% and treatment-related mortality was 5%. Complete response and tumor reduction of more than 75% were obtained in 4 (21%) and 16 (84%) out of 19 patients, respectively. The actuarial 3-year overall survival (OS) and event-free survival (EFS) after PBSCT/HDT were 65.6% and 22.0%, respectively. The median EFS duration was 18 months. These preliminary results indicated that HDT/PBSCT is feasible for Japanese MM patients. A prospective randomized clinical trial will be required to assess the efficacy.

Adult↗
PubMed2004

[Myelodysplastic syndrome associated with intestinal tract-type Behçet disease characterized by an esophageal ulcer].

A 55-year-old man with advanced myelodysplastic syndrome was hospitalized prior to undergoing an allogeneic bone marrow transplantation. Immediately before hospitalization, he had suffered from phlegmon in both lower extremities and right forearm as well as genital and oral ulcers. After admission, he developed an esophageal ulcer and was thus diagnosed as having intestinal tract-type Behçet disease. HLA-B51 was not present. Within a month, he died of pulmonary hemorrhage associated with pneumonia, possibly because of a low platelet count, and vasculoendothelial damage related to Behçet disease. This is a rare case of myelodysplastic syndrome that developed Behçet disease with a severe esophageal ulcer.

Behcet Syndrome↗
PubMed2004

[Myeloperoxidase].

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Acute Disease↗
PubMed2003

Leukemia-related transcription factor TEL accelerates differentiation of Friend erythroleukemia cells.

TEL belongs to a member of the ETS family transcription factors that represses transcription of target genes such as FLI-1. Although TEL is essential for establishing hematopoiesis in neonatal bone marrow, its role in erythroid lineage is not understood. To investigate a role for TEL in erythroid differentiation, we introduced TEL into mouse erythroleukemia (MEL) cells. Overexpressing wild-type-TEL in MEL cells enhanced differentiation induced by hexamethylene bisacetamide or dimethylsulfoxide, as judged by the increased levels of erythroid-specific delta-aminolevulinate synthase and beta-globin mRNAs. TEL bound to a corepressor mSin3A through the helix-loop-helix domain. A TEL mutant lacking this domain still bound to the ETS binding site, but lost its transrepressional effect. This mutant completely blocked erythroid differentiation in MEL cells. Moreover, it showed dominant-negative effects over TEL-mediated transcriptional repression and acceleration of erythroid differentiation. Endogenous TEL mRNA was found to increase during the first 3 days in differentiating MEL cells and drastically decrease thereafter. All these data suggest that TEL might play some role in erythroid cell differentiation.

5-Aminolevulinate Synthetase↗
PubMed2003

Monocytic leukemia with CALM/AF10 rearrangement showing mediastinal emphysema.

The t(10;11)(p12-14;q14-21) is a non-random translocation that results in the fusion of CALM gene on chromosome 11 with AF10 gene on chromosome 10. This translocation is observed in acute myeloid leukemia, acute lymphoblastic leukemia, and lymphoblastic lymphoma. Here we report a patient with t(10;11) who was diagnosed with AML-M4. Reverse transcriptase-polymerase chain reaction (RT-PCR) assay revealed one type of CALM/AF10 and three types of AF10/CALM fusion transcripts. Sequencing analysis for these RT-PCR products determined the breakpoint in CALM at nucleotide (nt) 1926-1927 and in AF10 at nt 423-424. The latter breakpoint was the same as that identified in three monocytic cell lines carrying t(10;11). After achieving complete remission, the patient developed mediastinal emphysema during the course of consolidation therapy, possibly due to the necrosis of his mediastinal mass. Monocytic leukemias with CALM/AF10 fusion are frequently associated with mediastinal invasion. We need to pay special attention to such a complication, even if the chest X-ray is normal at presentation.

Adolescent↗
PubMed2003

Extranodal diffuse follicular center lymphoma mimicking mantle cell lymphoma of the intestine.

We report a case of diffuse follicular center lymphoma (FCL), which is a morphological variant of follicular lymphoma, resembling multiple lymphomatous polyposis (mantle cell lymphoma of the intestine). The patient was a 48-year-old Japanese man who was found, by colonoscopy, to have numerous small polypoid lesions along the entire large intestine. Abdominal computed tomography revealed hepatosplenomegaly and enlargement of multiple mesenteric lymph nodes. Histologically, the lesion was characterized by diffuse proliferation of small- to medium-sized lymphocytes with cleaved nuclei in the mucosa and submucosa. Immunohistochemical studies showed that the tumor cells were CD20+, CD10+, BCL-2+, CD5-, surface IgM-, and cyclin D1-. Moreover, a cytogenetic study showed a translocation at (14;18)(q32;q21). Finally, this case was diagnosed as diffuse FCL, although the tumor was mimicking mantle cell lymphoma.

Chromosomes, Human, Pair 14↗