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T Tauchi

Publications and source records attributed to T Tauchi.

At least 19 recordsLinked to original sources
PubMed2007

Identification and functional signature of genes regulated by structurally different ABL kinase inhibitors.

Dasatinib is an ATP-competitive, multi-targeted SRC and ABL kinase inhibitor that can bind BCR-ABL in both the active and inactive conformations. From a clinical standpoint, dasatinib is particularly attractive because it has been shown to induce hematologic and cytogenetic responses in imatinib-resistant chronic myeloid leukemia patients. The fact because the combination of imatinib and dasatinib shows the additive/synergistic growth inhibition on wild-type p210 BCR-ABL-expressing cells, we reasoned that these ABL kinase inhibitors might induce the different molecular pathways. To address this question, we used DNA microarrays to identify genes whose transcription was altered by imatinib and dasatinib. K562 cells were cultured with imatinib or dasatinib for 16 h, and gene expression data were obtained from three independent microarray hybridizations. Almost all of the imatinib- and dasatinib-responsive genes appeared to be similarly increased or decreased in K562 cells; however, small subsets of genes were identified as selectively altered expression by either imatinib or dasatinib. The distinct genes that are selectively modulated by dasatinib are cyclin-dependent kinase 2 (CDK2) and CDK8, which had a maximal reduction of <5-fold in microarray screen. To assess the functional importance of dasatinib regulated genes, we used RNA interference to determine whether reduction of CDK2 and CDK8 affected the growth inhibition. K562 and TF-1BCR-ABL cells, pretreated with CDK2 or CDK8 small interfering RNA, showed additive growth inhibition with imatinib, but not with dasatinib. These findings demonstrate that the additive/synergistic growth inhibition by imatinib and dasatinib may be mediated in part by CDK2 and CDK8.

Benzamides↗
PubMed2006

Telomerase inhibition with a novel G-quadruplex-interactive agent, telomestatin: in vitro and in vivo studies in acute leukemia.

The telomerase complex is responsible for telomere maintenance and represents a promising neoplasia therapeutic target. Recently, we have demonstrated that treatment with a G-quadruplex-interactive agent, telomestatin reproducibly inhibited telomerase activity in the BCR-ABL-positive leukemic cell lines. In the present study, we investigated the mechanisms of apoptosis induced by telomerase inhibition in acute leukemia. We have found the activation of caspase-3 and poly-(ADP-ribose) polymerase in telomestatin-treated U937 cells (PD20) and dominant-negative DN-hTERT-expressing U937 cells (PD25). Activation of p38 mitogen-activated protein (MAP) kinase and MKK3/6 was also found in telomestatin-treated U937 cells (PD20) and dominant-negative DN-hTERT-expressing U937 cells (PD25); however, activation of JNK and ASK1 was not detected in these cells. To examine the effect of p38 MAP kinase inhibition on growth properties and apoptosis in telomerase-inhibited cells, we cultured DN-hTERT-expressing U937 cells with or without SB203580. Dominant-negative-hTERT-expressing U937 cells stopped proliferation on PD25; however, a significant increase in growth rate was observed in the presence of SB203580. Treatment of SB203580 also reduced the induction of apoptosis in DN-hTERT-expressing U937 cells (PD25). These results suggest that p38 MAP kinase has a critical role for the induction of apoptosis in telomerase-inhibited leukemia cells. Further, we evaluated the effect of telomestatin on the growth of U937 cells in xenograft mouse model. Systemic intraperitoneal administration of telomestatin in U937 xenografts decreased tumor telomerase levels and reduced tumor volumes. Tumor tissue from telomestatin-treated animals exhibited marked apoptosis. None of the mice treated with telomestatin displayed any signs of toxicity. Taken together, these results lay the foundations for a program of drug development to achieve the dual aims of efficacy and selectivity in vivo.

Acute Disease↗
PubMed2004

A G-quadruplex-interactive agent, telomestatin (SOT-095), induces telomere shortening with apoptosis and enhances chemosensitivity in acute myeloid leukemia.

Telomerase, the ribonucleoprotein enzyme maintaining the telomeres of eukaryotic chromosomes, is up-regulated in the vast majority of human neoplasias but not in normal somatic tissues. Therefore, the telomerase complex represents a promising universal therapeutic target in cancer. Telomeric G-rich single-stranded DNA can adopt in vitro an intramolecular quadruplex structure, which has been shown to inhibit telomerase activity. We examined G-quadruplex interactive agent, telomestatin (SOT-095), for its ability to inhibit the proliferation of human leukemia cells, including freshly obtained leukemia cells. Telomere length was determined by either the terminal restriction fragment method or flow-FISH, and apoptosis was assessed by flow cytometry. Moreover, chemosensitivity was examined in telomestatin-treated U937 cells before ultimate telomere shortening. Treatment with telomestatin reproducibly inhibited telomerase activity in U937 and NB4 cells followed by telomere shortening. Enhanced chemosensitivity toward daunorubicin and cytosine-arabinoside was observed in telomestatin-treated U937 cells, before ultimate telomere shortening. Telomere shortening associated with apoptosis by telomestatin was evident in some freshly obtained leukemia cells from acute myeloid leukemia patients, regardless of sub-types of AML and post-myelodysplasia AML. These results suggest that disruption of telomere maintenance by telomestatin limits the cellular lifespan of AML cells, as well. However, in a minority of AML patients apoptosis was not evident, thus indicating that resistant mechanism might exist in some freshly obtained AML cells. Therefore, further investigation of telomestatin as a therapeutic agent is warranted.

Acute Disease↗
PubMed2003

Telomerase inhibition enhances apoptosis in human acute leukemia cells: possibility of antitelomerase therapy.

Telomerase is a ribonucleoprotein enzyme that maintains protective structures at the ends of eukaryotic chromosomes. We examined the impact of telomerase inhibition by the dominant-negative human catalytic subunit of telomerase (DN-hTERT) on the biological features of acute leukemia. We introduced vectors encoding dominant- negative (DN)-hTERT, wild-type (WT)-hTERT, or a control vector expressing only a drug-resistant marker into a telomerase-positive human acute lymphoblastic leukemia cell line, HAL-01. Expression of DN-hTERT dramatically inhibited telomerase activity, leading to apoptotic cell death. Mutant telomerase expression also enhanced daunorubicin-induced apoptosis. Nude mice (n=5 per group) received subcutanous implants of HAL-01 cells expressing the control vector or DN-hTERT or WT-hTERT. Implantation of HAL-01 cells expressing control vector (n=5) rapidly produced tumors, whereas implantation of those expressing DN-hTERT (n=5) did not. Thus, telomerase inhibition both growth of HAL-01 cells in vitro and tumorigenic capacity in vivo. Furthermore, the G-quadruplex-interactive telomerase-specific inhibitor, telomestatin, shortened the telomere length and induced apoptosis in freshly isolated primary acute leukemia cells. These results suggest that antitelomerase therapy may be useful in some acute leukemias in combination with antileukemic agents such as daunorubicin.

Acute Disease↗
PubMed2001

CIS1, a cytokine-inducible SH2 protein, suppresses BCR/ABL-mediated transformation. Involvement of the ubiquitin proteasome pathway.

OBJECTIVE: BCR/ABL is a chimeric oncoprotein that exhibits deregulated tyrosine kinase activity and is implicated in the pathogenesis of Philadelphia chromosome (Ph)-positive leukemia. A general understanding of BCR/ABL signaling events is emerging, but little is known about the endogenous inhibitors of p210 BCR/ABL. The present study focused attention on CIS1, a cytokine-inducible SH2 protein, as a potential physiologic antagonist for BCR/ABL. MATERIALS AND METHODS: The murine hematopoietic cell line NSF/N1.H7 stably transfected with BCR/ABL was compared to the parental counterparts for induction of CIS1 by immunoblotting and immunoprecipitation. Cells were treated with a proteasome inhibitor to examine the effect of a proteasome inhibitor on CIS1 protein expression. To determine the effect of CIS1 on BCR/ABL-mediated transformation, we generated Rat-1 fibroblasts transfected with either a control vector, CIS1, BCR/ABL p210, or CIS1 plus BCR/ABL p210. RESULTS: Three forms of CIS1 with molecular masses of 32, 37, and 47 kDa were detected in BCR/ABL-transformed cells. The 47-kDa protein was a ubiquitinated protein. The proteasome inhibitor increased the formation of complexes between CIS1 and BCR/ABL. Transformation of p210 BCR/ABL was significantly suppressed in cells overexpressing CIS1. CONCLUSION: The results suggest that CIS1 is an endogenous inhibitor of p210 BCR/ABL and is likely to be important in the pathogenesis of Ph-positive leukemia.

3T3 Cells↗
PubMed2001

Successful treatment with cyclosporin A for myelodysplastic syndrome with erythroid hypoplasia associated with T-cell receptor gene rearrangements.

Myelodysplastic syndrome (MDS) with erythroid hypoplasia, a rare form of MDS, has not yet been clearly defined. We report four patients with MDS with erythroid hypoplasia who received immunosuppressive therapy. All were elderly, had severe transfusion-dependent anaemia, morphological evidence of myelodysplasia and a low percentage (3.2-13.6%) of erythroid precursors. Administration of cyclosporin A (CsA) improved their anaemia; all transfusion-dependent patients achieved transfusion-independence. An inverted CD4/8 ratio was seen in three patients who also demonstrated T-cell receptor (TCR)-beta and -gamma gene rearrangements by Southern blotting and clonality by polymerase chain reaction. Treatment with CsA can be an attractive alternative treatment for patients with MDS with erythroid hypoplasia, which may be associated with a clonal abnormality in T cells.

Aged↗
PubMed2001

Telomere dynamics in myelodysplastic syndromes and acute leukemic transformation.

Myelodysplastic syndromes (MDS) are characterized by cytopenias in the blood and dysplastic features in the hematopoietic cells. Although the impact of cytogenetic abnormalities is considerable for prognosis, the exact genetic mechanism of MDS remains undetermined. In this study we assessed cytogenetic changes, microsatellite alterations, and telomere dynamics in order to obtain further insight into the pathogenesis of MDS. Thirty-three percentage of MDS patients and 60% of post-MDS acute leukemia (post-MDS AML) had de novo microsatellite changes. In the MDS phase, however, > 60% of patients showed reduction of telomere lengths without microsatellite changes, indicating that telomere reduction in most MDS patients does not seem to be directly linked to genome instability, or that reduction of telomere length does not induce microsatellite changes in the MDS phase. Some MDS patients had microsatellite changes without telomerase elevation, indicating that genome instability might accumulate during the disease progression in some MDS patients, and this condition (cellular senescence) may be related to ineffective hemopoiesis in MDS patients. In contrast, 40% of post-MDS AML patients had elevated telomerase activity with microsatellite changes, indicating that approximately 40% of patients with post-MDS AML patients had accumulation of genome instability resulting in elevated telomerase activity in an attempt to obtain genetic stability. However, the remaining MDS patients had microsatellite changes without telomerase up-regulation, suggesting that some MDS had genome instability even after leukemic transformation. Most MDS patients with elevated telomerase activity in the AML phase had elevated telomerase activity even in the MDS phase without apparent change in telomere length before and after leukemic transformation. These findings indicate that telomerase activity in the MDS phase may be independent of telomere length, although telomere shortening seems to be related to genomic instability, and this process may be linked to apoptosis of MDS cells.

Cell Transformation, Neoplastic↗
PubMed2001

Impaired telomere regulation mechanism by TRF1 (telomere-binding protein), but not TRF2 expression, in acute leukemia cells.

Telomere regulation is suggested to be an important mechanism in cellular proliferation and cellular senescence not only in normal diploid cells but also in neoplastic cells, including human leukemia cells. We studied the possible correlation among telomere length, telomerase (a ribonuclear protein that synthesizes the telemeres de novo) activity, hTERT (a catalytic subunit of telomerase) expression, and TRF1 and TRF2 (telomere DNA binding proteins) expression in human acute leukemia cells. The hTERT expression level was strongly associated with telomerase activity (P=0.0001), indicating that the expression level of the catalytic subunit (hTERT) regulates telomerase activity in human acute leukemia cells. TRF1 expression, which is believed to control telomere length, was significantly elevated in patients with acute lymphoblastic leukemia (ALL) (P=0.0232) compared to those in acute myeloid leukemia (AML); TRF1 expression tended to be higher in patients without telomere shortening (P=0.077) and in those with hTERT expression (P=0.055). This indicates that TRF1 may act to monitor telomere length under the condition of up-regulated telomerase activity in some neoplastic cells. In contrast, TRF2 expression in acute leukemia did not show any correlation with telomere parameters in this study. Although the precise regulation mechanism of telomere length is still uncertain, these results may suggest that regulation of telomere length is partially associated with TRF1 expression, whereas dysfunction of TRF1 expression may be speculated in a subset of acute leukemia.

Adolescent↗
PubMed2000

Changes of the sacrum in severe spondylolisthesis: a possible key pathology of the disorder.

Deficient development of the posterior lumbosacral portion has been thought to be a possible etiology of severe spondylolisthesis. However, the precise causes of the deformity have yet to be revealed. To our knowledge, progression of the disorder has not been discussed in the light of sacral changes on magnetic resonance imaging (MRI). The objectives of the present study were to document changes of the sacrum on MRI scans in patients with severe spondylolisthesis and to discuss the relation of these changes to the progression of deformities. Roentgenograms and MRI scans of 13 patients (10 women and 3 men) with severe spondylolisthesis were retrospectively reviewed. Average age at first MRI examination was 20 years (range, 12 to 50 years). The MRI scans commonly showed a defect at the antero-superior portion of the sacrum. This lesion seems to appear during the period of progression of slipping associated with lumbosacral kyphosis. The defect of the sacrum was considered a unique feature to discriminate this type of olisthesis from others. Taking into consideration the present results, the deformity can be called kyphospondylolisthesis.

Adolescent↗
PubMed2000

Chronic lymphocytic leukemia complicated by plasmacytoma originating from different clones.

In a woman with chronic lymphocytic leukemia (CLL), a plasmacytoma developed on the back region after four years. CLL cases complicated with plasmacytoma are rare. In the present case, the plasmacytoma showed kappa cytoplasmic immunoglobulin (Ig), and the CLL showed gamma lambda surface Ig. To reveal the clonal origin of CLL and plasmacytoma, we analyzed Ig gene rearrangements in the patient's peripheral blood and plasmacytoma. Ig gene DNA analysis confirmed the presence of different rearrangements in the heavy and light chain genes of CLL and plasmacytoma. These findings suggest that in this patient, the two B cell malignancies arose from expansion of two phenotypically and genotypically distinct clones.

Blotting, Southern↗
PubMed2000

Telomere dynamics and genetic instability in disease progression of chronic myeloid leukemia.

Chronic myeloid leukemia (CML) is characterized by a Philadelphia (Ph) translocation creating a novel BCR-ABL oncoprotein, and CML patients have a chronic phase for several years followed by an intractable blast cell proliferation, called blast transformation. In the blast phase, more than 60% of patients show additional cytogenetic changes, e. g., double Ph, +8, i(17q). In this review, we would like to address genetic changes, including genome instability, cytogenetic changes, and telomere dynamics that relate to karyotypic instability. In the chronic phase, approximately 60% of CML patients show reduced telomere length without highly elevated telomerase activity or microsatellite alterations, indicating that telomere reduction may be linked to cell replication. Therefore, the Ph translocation might be a first event to immortalize cell proliferation. In the blast phase, 50% of CML patients have high levels of elevated telomerase activity and the same number of patients had microsatellite changes. Of note is that most patients with telomerase up-regulation in the blast phase had additional cytogenetic changes and >60% of them showed microsatellite changes at least at one locus. In contrast, most patients without telomerase activity did not show microsatellite changes. These findings may indicate that telomerase up-regulation in the blast phase of CML patients is closely associated with microsatellite changes (representative of genome instability), while blast cells in the remaining patients (30%) maintain their proliferative capability without microsatellite changes and telomerase up-regulation. This further suggests that there is also an unknown mechanism for genome stability without the process of telomerase up-regulation in some patients with CML in blast crisis.

Cell Transformation, Neoplastic↗