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K Mitani

Publications and source records attributed to K Mitani.

At least 91 records · Page 5Linked to original sources
PubMed1998

Mutation analysis of the WT1 gene in myelodysplastic syndromes.

The WT1 tumor suppressor gene was examined for mutations in a panel of 44 patients with myelodysplastic syndromes (MDS) including acute myelogenous leukemias (AML) secondary to MDS, using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) analysis and sequencing analysis. A WT1 mutation was detected in one out of 17 cases of AML secondary to MDS. This mutation exists upstream of the zinc finger region and is predicted to produce a truncated WT1 protein lacking the zinc finger region. No mutations were detected in 27 MDS patients who had not progressed to AML. This is the first report of analysis for WT1 mutations in a large number of MDS patients, suggesting that WT1 mutations are uncommon in MDS. Abnormalities in this gene may, however, contribute to a small proportion of cases showing progression from MDS into AML.

Amino Acid Sequence↗
PubMed1998

[Flow cytometric DNA analysis and MR imaging of salivary gland tumors].

We correlated the histopathology of 32 cases of salivary gland tumors with MR imaging and flow cytometric DNA analysis. All malignant tumors were invasive and/or had an ill-defined margin. Fifty-seven percent of the pleomorphic adenomas were shown as a high signal intensity area on T2 weighted images. Fifty-six percent of Warthin tumors were shown as a low or iso signal intensity area on T2 weighted images associated with the cystic portion. Sixty-seven percent of malignant tumors were characterized by DNA aneuploidy and/or a total percentage of the S-phase fraction plus the G2 + M fraction higher than 10%. It was less than 10% and the Ki-67 positive fraction was higher than 20% in all pleomorphic adenomas. The Ki-67 positive fraction was less than 20% in 78% of Warthin tumors. The histopathology of all malignant tumors, 86% of the pleomorphic adenomas, and 89% of Warthin tumors was correctly predicted by the combination of MR images and flow cytometry. We suggest that the MR images combined with flow cytometric analysis of fine needle aspiration-derived materials is useful in the pre-operative histopathologic diagnosis of salivary gland tumors.

Adenolymphoma↗
PubMed1997

Efficient transfer of genes into senescent cells by adenovirus vectors via highly expressed alpha v beta 5 integrin.

Although various methods for transferring genes into mammalian cells have been established, none have been successful with senescent cells. In this report, we present evidence of the efficient transfer of a gene into human senescent fibroblasts using an adenoviral vector. By employing a recombinant adenovirus vector harboring the beta-galactosidase gene (Ad-CAG beta NR), we observed a good correlation between the proportion of beta-galactosidase positive cells and population doubling of the infected cells. In addition, 1.5- to 6.0-fold greater beta-galactosidase activity was observed in senescent fibroblasts (population doubling [PD] = 58) than in young cells (PD = 15). Western blotting analysis revealed that, compared with young fibroblasts, senescent fibroblasts expressed larger amounts of alpha v beta 5 and alpha v beta 3 integrins which were thought to form part of the adenovirus receptor. These results suggest that higher expression of alpha v beta 5 and alpha v beta 3 integrins in senescent cells renders them more sensitive to adenovirus infection than young cells. Thus, adenovirus vectors may prove to be useful in gene therapy strategies directed against senescence-related disorders.

Adenoviridae↗
PubMed1997

The phosphatidylinositol 3' kinase pathway is required for the survival signal of leukocyte tyrosine kinase.

Leukocyte tyrosine kinase (LTK) is a receptor tyrosine kinase which belongs to the insulin receptor superfamily and is mainly expressed in pre-B lymphocytes and neuronal tissues. Recently, we demonstrated that LTK utilizes Shc and IRS-1 as two major substrates and while both equally activate the Ras pathway, only IRS-1 suppresses apoptosis of hematopoietic cells, suggesting the existence of another unidentified signaling pathway downstream of IRS-1, which is relevant to the anti-apoptotic activity. In the present study, we found that wortmannin, a specific inhibitor of phosphatidylinositol 3' (PI3)-kinase, abolished the survival effects of LTK. Although c-Cbl is found to be phosphorylated by LTK and therefore is a second candidate linking LTK with the PI3-kinase pathway along with IRS-1, we found that the p85 subunit of PI3 kinase directly binds to tyrosine 753 of LTK, which is located within a YXXM motif, a consensus binding amino acid sequence for the SH2 domain of p85, but fails to bind to IRS-1 or c-Cbl. Ba/F3 cells which stably express the EGF receptor-LTK chimeric receptor carrying a mutation at tyrosine 753 fell into apoptotic death even in the presence of EGF, indicating that the PI3 kinase pathway is required for the survival effects of LTK.

Androstadienes↗
PubMed1997

Purification and molecular cloning of SH2- and SH3-containing inositol polyphosphate-5-phosphatase, which is involved in the signaling pathway of granulocyte-macrophage colony-stimulating factor, erythropoietin, and Bcr-Abl.

Grb2/Ash and Shc are the adapter proteins that link tyrosine-kinase receptors to Ras and make tyrosine-kinase functionally associated with receptors and Ras in fibroblasts and hematopoietic cells. Grb2/Ash and Shc have the SH3, SH2, or phosphotyrosine binding domains. These domains bind to proteins containing proline-rich regions or tyrosine-phosphorylated proteins and contribute to the association of Grb2/Ash and Shc with other signaling molecules. However, there could remain unidentified signaling molecules that physically and functionally interact with these adapter proteins and have biologically important roles in the signaling pathways. By using the GST fusion protein including the full length of Grb2/Ash, we have found that c-Cbl and an unidentified 135-kD protein (pp135) are associated with Grb2/Ash. We have also found that they become tyrosine-phosphorylated by treatment of a human leukemia cell line, UT-7, with granulocyte-macrophage colony-stimulating factor (GM-CSF). We have purified the pp135 by using GST-Grb2/Ash affinity column and have isolated the full-length complementary DNA (cDNA) encoding the pp135 using a cDNA probe, which was obtained by the degenerate polymerase chain reaction based on a peptide sequence of the purified pp135. The cloned cDNA has 3,958 nucleotides that contain a single long open reading frame of 3,567 nucleotides, encoding a 1,189 amino acid protein with a predicted molecular weight of approximately 133 kD. The deduced amino acid sequence reveals that pp135 is a protein that has one SH2, one SH3, and one proline-rich domain. The pp135, which contains two motifs conserved among the inositol polyphosphate-5-phosphatase proteins, was shown to have the inositol polyphosphate-5-phosphatase activity. The pp135 was revealed to associate constitutively with Grb2/Ash and inducibly with Shc using UT-7 cells stimulated with GM-CSF. In the cell lines derived from human chronic myelogenous leukemia, pp135 was constitutively tyrosine-phosphorylated and associated with Shc and Bcr-Abl. These facts suggest that pp135 is a signaling molecule that has a unique enzymatic activity and should play an important role in the signaling pathway triggered by GM-CSF and in the transformation of hematopoietic cells caused by Bcr-Abl.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Antisense repression of proto-oncogene c-Cbl enhances activation of the JAK-STAT pathway but not the ras pathway in epidermal growth factor receptor signaling.

Many growth factors including epidermal growth factor (EGF) induce tyrosine phosphorylation of the c-Cbl proto-oncogene product, whose function, however, remains unclear. Recently, Sli-1, a Caenorhabditis elegans homologue of c-Cbl, was found to be a negative regulator of let-23-mediated vulval induction pathway, suggesting that c-Cbl may negatively regulate EGF receptor (EGFR)-mediated signaling. In this study, by an antisense RNA approach, we examined the effects of expression level of c-Cbl on EGFR signaling and showed that overexpression of c-Cbl reduces and antisense repression of c-Cbl enhances autophosphorylation of EGF receptors and activation of the JAK-STAT pathway. However, in contrast to the Sli-1 protein, the expressed amount of c-Cbl does not affect activation of the Ras pathway, suggesting that the EGFR-mediated signaling pathways are differently regulated by c-Cbl among nematodes and mammals.

3T3 Cells↗
PubMed1997

Mutations and loss of expression of a mismatch repair gene, hMLH1, in leukemia and lymphoma cell lines.

Defects in genes involved in DNA mismatch repair have been detected in both hereditary and sporadic tumors of colon, endometrium, and ovary and suggested to be associated with tumorigenesis. To investigate disruptions of the mismatch repair system in hematological malignancies, we examined alterations of the human mutL homologue 1 (hMLH1) gene, a member of the mismatch repair gene family, in a total of 43 human leukemia and lymphoma cell lines, by polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) and sequencing analyses. Mutations of the hMLH1 gene were detected in three cell lines established from lymphoid leukemias. Moreover, Northern and Western blot analyses showed that expression of hMLH1 transcript or protein was abrogated in these three leukemia cell lines. Further studies for microsatellite loci showed that these cell lines without hMLH1 expression showed microsatellite instability. This is the first report that describes mutations and inactivation of the hMLH1 gene in human leukemia cells, suggesting that disruption of DNA mismatch repair system may play an important role in the development of human lymphoid leukemias.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Granulocyte colony stimulating factor-producing tongue carcinoma.

BACKGROUND: Leukocytosis without infection in patients with malignancies is known as the leukemoid reaction. The mechanisms involved in this phenomenon remain uncertain. METHODS: We describe the clinical, biochemical and immunohistochemical findings in a patient with recurrent tongue carcinoma accompanied by marked leukocytosis as high as 96200/ mm3. RESULTS: The serum granulocyte colony stimulating factor (G-CSF) concentration was increased to 204 (normal: < 30) pg/ml, which paralleled to the elevation of white blood cell (WBC) count and the tumor growth. The G-CSF content of the tumor tissue was also elevated (131 pg/mg protein) compared to that in control patients (6.63 +/- 2.63 pg/mg protein). Production of G-CSF from the tumor was evidenced by immunohistochemical staining with monoclonal antibody against human recombinant G-CSF. CONCLUSIONS: We suggest that the G-CSF production of the tumor participates in the mechanisms of the leukemoid reaction.

Aged↗
PubMed1997

Necrotizing Bacillus cereus infection of the meninges without inflammatory reaction in a patient with acute myelogenous leukemia: a case report.

A 64-year-old man in a severely immunocompromised state due to acute myelogenous leukemia died, respirator-unaided, about 10 h after the abrupt onset of coma. An earlier blood culture had yielded Bacillus cereus. The autopsy, performed 2 h after death, demonstrated diffuse subarachnoid hemorrhage without berry aneurysms, and the formalin-fixed brain was tinged with gray-brownish discoloration. The sections of the brain presented a whitish tint of the surface layer of all portion of the cerebral cortices, even those in the sulci. Histological examination of the brain revealed leptomeningeal B. cereus dissemination, and widespread necrosis of the leptomeninges and arachnoid vessels without inflammatory cell reaction. The grossly recognizable whitish surface layer of the cerebral cortex showed overt hyperchromatism, and contained neurons more degenerative than those located in the deeper cortical layer. The total absence of inflammatory reaction may be explained by a combination of the immunocompromised state of the patient and the character of B. cereus infection, which in itself induces little inflammatory reaction. The prominent lesions were confined to the cerebral surface layer and leptomeningeal tissue including the arachnoid vessels, which were all bathed in the cerebrospinal fluid, suggesting that some necrotizing toxins had been secreted into the fluid by the B. cereus. The necrosis of arachnoid vessels is thought to have in turn caused diffuse subarachnoid hemorrhage and marked disturbance of the cerebral blood flow, resulting in the terminal coma.

Bacillus cereus↗
PubMed1997

Subcellular localization of the MEN, MLL/MEN and truncated MLL proteins expressed in leukemic cells carrying the t(11;19)(q23;p13.1) translocation.

The t(11;19)(q23;p13.1) translocation is exclusively associated with myeloid leukemias. Previously, we cloned several species of MLL/MEN chimeric cDNAs in a patient with myeloid leukemia carrying the t(11;19)(q23;p13.1) translocation. The MEN sequence directly followed the 5' region of MLL cDNA in some species and otherwise there presented an inserted sequence of 120 bp between the MLL and MEN sequences in others. Because the insertion sequence contained an in-frame termination codon, they coded only for the NH2-terminal part of MLL (truncated MLL). We also cloned the normal MEN cDNA in full-length with a cDNA library derived from K562 cells. We expressed the normal MEN, MLL/MEN chimeric and truncated MLL proteins in COS7 cells with the corresponding cDNAs and detected them with antibodies raised against the MEN and MLL peptides. Immunostaining and subcellular fractionation showed nuclear localization of all these proteins. These findings suggested that MLL/MEN chimeric cDNAs were actually translated into both MLL/MEN fusion and truncated MLL proteins and that they were localized in the nucleus of leukemic cells. Recently, Conaway et al. reported that MEN is an RNA polymerase II elongation factor. The leukemogenesis by the t(11;19)(q23;p13.1) translocation may have resulted from the alteration of transcription regulation induced by the MLL/MEN fusion protein and/or the truncated MLL protein.

Animals↗
PubMed1997

No concomitant occurrence of the N-ras and p53 gene mutations in myelodysplastic syndromes.

Mutations of the N-ras oncogene and p53 tumor suppressor gene were simultaneously investigated in bone marrow cells from 44 patients with myelodysplastic syndrome (MDS) or MDS-derived leukemia by single-strand conformation polymorphism (SSCP) analysis followed by direct sequencing. The mutations of the N-ras gene were detected only in two cases with MDS-derived leukemia. Three patients with MDS-derived leukemia and one with refractory anemia with excess of blasts exhibited five mutations of the p53 gene. No concomitant mutations of both genes were observed in our study, suggesting that alterations of both genes could play an important role in the progression of MDS in a non-cooperative manner.

Anemia, Refractory↗
PubMed1997

High prevalence of hantavirus infection in a group of Chinese patients with acute hepatitis of unknown aetiology.

In southwestern China, small but substantial numbers of patients with acute hepatitis were found without known hepatropic viral infections (hepatitis A, B, C, D or E, cytomegalovirus, Epstein-Barr virus) and were receiving no hepatotoxic drugs. Prevalence of antibodies, both neutralizing and specific immunoglobulin (Ig)M and IgG, to Hantaan virus were evaluated in a cohort of 136 such patients: 83 were of unknown aetiology, 53 had known viral hepatitis and 59 healthy subjects acted as controls. The results showed that the incidence of neutralizing antibody to Hantaan virus in acute hepatitis patients with non-hepatitis A-E virus infections (13 of 83) was significantly higher than in those with A-E infections (0 of 53, P<0.01). Furthermore, the incidence of specific IgM antibody to Hantaan virus in acute hepatitis patients with non-hepatitis A-E virus infections (6 of 83) was significantly higher than in those with A-E infections (0 of 53, P<0.05) and in healthy subjects (0 of 59, P < 0.05). These findings suggest that Hantaan virus may be an important agent, contributing, at least in southwestern China, to a significant number of the cases of acute hepatitis of unknown aetiology. This hantavirus infection resulted in an acute hepatitis, differing from the typical diseases: haemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS).

Acute Disease↗
PubMed1997

Triple synergism of human T-lymphotropic virus type 1-encoded tax, GATA-binding protein, and AP-1 is required for constitutive expression of the interleukin-5 gene in adult T-cell leukemia cells.

Accumulated evidence demonstrates that adult T-cell leukemia (ATL) is frequently associated with eosinophilia, and human T-lymphotropic virus type 1 (HTLV-1)-infected cells frequently express interleukin-5 (IL-5). However, the molecular mechanism of constitutive IL-5 expression in HTLV-1-infected cells remains unclear. To clarify the mechanism of aberrant IL-5 expression in HTLV-1-infected cells, we investigated the response of the human IL-5 promoter to the HTLV-1-encoded protein Tax. Cotransfection experiments using Jurkat cells revealed that Tax is incapable of activating the IL-5 promoter by itself but that it synergistically transactivates the promoter with GATA-binding protein (GATA-4) and 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulation. By introducing a series of mutations within the IL-5 promoter, we found that conserved lymphokine element 0 (CLE0) is responsible for mediating the signal induced by Tax-TPA. A deletion construct of the promoter indicated that the -75 GATA element and CLE0 are sufficient to mediate synergistic activation of the IL-5 promoter. Electrophoretic mobility shift assays using Jurkat cell nuclear extracts demonstrated that TPA induces a transcription factor to bind CLE0, and an experiment using JPX-9 cell nuclear extracts showed that Tax enhances this binding activity. An antibody supershift experiment revealed that this band consists of c-Jun and JunD. However, among the Jun family members, only c-Jun is able to cooperate with Tax and GATA-4 to activate the IL-5 promoter. We have determined the minimum factors required for IL-5 gene activation by reconstituting the IL-5 promoter activity in F9 cells. This is the first report to demonstrate the functional involvement of Tax protein in IL-5 gene regulation and to suggest the functional triple synergism among Tax, GATA-4, and AP-1, which disrupts regulated control of the gene and leads to constitutive expression of the IL-5 gene.

Calcimycin↗
PubMed1997

Fulminant septicemic syndrome of Bacillus cereus in a leukemic patient.

We report a rapidly fatal Bacillus cereus septicemia in a leukemic patient receiving remission-induction therapy. Symptoms resembling food poisoning and fever preceded coma accompanied by neurologic abnormalities. Autopsy revealed necrotizing leptomeningitis with subarachnoid hemorrhage and coagulation necrosis of the liver with bacterial infiltration. These clinicopathologic findings were closely similar to those of reported cases. Because of a rapidly fatal clinical course, suspicion of this syndrome early in the course is important to determine an appropriate treatment. Therefore, we propose that this type of septicemia should be termed as fulminant septicemic syndrome of Bacillus cereus.

Bacillus cereus↗
PubMed1997

[Familial parkinsonism: different clinical phenotype between a mother and her daughter].

We reported a familial case of parkinsonism in which clinical features are different between a mother and her daughter. The mother developed rigidity and bradykinesia at age 76. Her symptoms were slowly progressive, and were responsive to levodopa. Thus, she was diagnosed as having Parkinson's disease. In contrast, her daughter developed postural instability as well as rigidity and bradykinesia at age 53 in rapid progression. In addition, she also developed pyramidal signs and autonomic failures, including orthostatic hypotension and urinary incontinence. The disease phenotype of the daughter resembled that of striatonigral degeneration (SND). However, PET studies showed normal binding of 11C-N-methyl-spiperone (NMSP) in the striatum, suggesting that the daughter was also affected with Parkinson's disease.

Aged↗
PubMed1997

Leukemogenesis by the chromosomal translocations.

The AML1 is the most commonly involved transcription factor gene in human leukemias and forms chimeric transcription factor genes, namely, AML1/MTG8 by the t(8;21), AML1/EVI-1 by the t(3;21), and TEL/AML1 by the t(12;21). The AML1a and AML1b, two isoforms of the AML1 protein, are translated from the AML1 gene by the alternative splicing. The shorter form and longer form are named as AML1a and AML1b, respectively. The AML1b contains the runt homology domain as a DNA-binding domain and the serine/proline/threonine-rich domain (PST domain) as a putative transactivation domain. The AML1a contains only the runt homology domain, but not the PST domain. The AML1b has a transactivation ability through the PEBP2 site and stimulates differentiation of myeloid cells. On the other hand, AML1a cna bind the PEBP2 site, but does not show a transactivation ability through the PEBP2 site. The AML1a dominantly suppresses transactivation induced by the AML1b and has the ability to block differentiation of myeloid cells. It is a reasonable hypothesis that the molecular ratio of AML1a to AML1b in myeloid cells could determine whether they proliferate or undergo a terminal differentiation.

Alternative Splicing↗
PubMed1997

An acute myeloid leukemia gene, AML1, regulates transcriptional activation and hemopoietic myeloid cell differentiation antagonistically by two alternative spliced forms.

The AML1 gene on chromosome 21 is disrupted in the (8;21)(q22;q22) and (3;21)(q26;q22) translocations associated with myelogenous leukemias and encodes a DNA-binding protein. From AML1 gene, two representative forms of proteins, AML1a and AML1b, are produced by an alternative splicing. Both forms have DNA-binding domain, but AML1a lacks a putative transcriptional activation domain which AML1b has. Here we demonstrate that AML1a, which solely has no effects as a transcriptional regulator, dominantly suppresses transcriptional activation by AML1b, and that AML1a exhibits the higher affinity for DNA-binding than AML1b. Furthermore a dominant negative form of AML1, AML1a, totally suppressed granulocytic differentiation otherwise induced by granulocyte colony-stimulating factor when AML1a was overexpressed in 32Dc13 murine myeloid cells. Such differentiation block by AML1a was canceled by the concomitant overexpression of AML1b. These data strongly suggest that a transcriptionally active form of AML1 is essential for the myeloid cell differentiation. In addition, we observed an altered expression level of AML1 along with the myeloid differentiation in several hemopoietic cell lines. In these cases, at least, the AML1 expression level is a potential regulator for myeloid cell differentiation.

Alternative Splicing↗