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H Tahara

Publications and source records attributed to H Tahara.

At least 55 records · Page 3Linked to original sources
PubMed2000

Telomerase activity and the expression of telomerase components in pituitary adenoma with malignant transformation.

BACKGROUND: Telomerase activity responsible for cellular immortality may participate the development of human cancers. Telomerase is a multisubunit ribonucleoprotein composed of at least three components: hTERT, hTERC, and TEP1. This is the first report showing telomerase activity and telomerase component expression in pituitary adenoma with histological malignant transformation. DESCRIPTION: A 16-year-old male with a prolactin-producing pituitary adenoma with metastasis is presented. The patient underwent three partial resections of an intra- and suprasellar lesion over a 2-year period and received focal irradiation. Eight years after the first admission, a metastatic lesion to the subarachnoid space around the medulla oblongata was detected and the lesion was resected as the fourth operation. Furthermore, the suprasellar lesion showed regrowth and partial resection was performed as the fifth operation. The last two specimens were diagnosed as pituitary carcinoma. Radiotherapy with gamma knife was performed for the residual suprasellar lesion and a new lesion in the left temporal lobe after the fifth operation. Telomerase activity was examined by TRAP/TRAP-HPA methods, qualitatively and quantitatively. Telomere length was examined by Southern blot analysis, and the expression of telomerase components (hTERT, hTERC, and TEP1) was examined by reverse transcriptase-polymerase chain reaction (RT-PCR). The MIB1 index, telomerase activity, and hTERT expression increased according to histologic malignancy chronologically in this patient. None of the specimens showed immunoreactivity for p53, EGFR, or bc12. No telomerase activity was detected in pituitary adenomas without malignant transformation, other benign brain tumors, or normal brain tissues. CONCLUSION: We report a patient with pituitary adenoma transforming to carcinoma. The tumor cells acquired immortality and revealed malignant transformation during the course of the disease, that was proved by an increase of telomerase activity and hTERT expression.

Adenoma↗
PubMed2000

Expression of telomerase component genes in hepatocellular carcinomas.

The aim of the study was to clarify the role of telomerase component genes in hepatocarcinogenesis and to examine both the relationship between the expression of telomerase component genes and histological differentiation in hepatocellular carcinoma (HCC) and the relationship between expression levels of telomerase component genes and telomerase activity in HCCs. Telomerase is a ribonucleoprotein enzyme composed of a template RNA and several proteins. Recently, three such telomerase component genes have been identified: human telomerase reverse transcriptase (hTERT); human telomerase RNA component (hTERC); and telomerase-associated protein 1 (TEP1). The expression of these components was evaluated in 34 HCCs and 24 non-cancerous liver tissues by reverse transcriptase-polymerase chain reaction (RT-PCR). Expression of hTERT mRNA was detected in most HCCs, but not in the non-cancerous tissues (P<0.01). Expression of hTERC was detected in both HCCs and non-cancerous tissues, but the expression level in HCCs was higher than that in non-cancerous tissues (P<0.01) and tended to increase as histological differentiation became less marked. The expression level of hTERT mRNA correlated with relative telomerase activity (P<0.01). These results suggest that telomerase reactivation during hepatocarcinogenesis might be regulated by only hTERT and an increase in telomerase activity level in tumour progression might be regulated by both hTERT and hTERC.

Adult↗
PubMed2000

The design and synthesis of a new tumor-selective fluoropyrimidine carbamate, capecitabine.

To identify an orally available fluoropyrimidine having efficacy and safety profiles greatly improved over those of parenteral 5-fluorouracil (5-FU: 1), we designed a 5-FU prodrug that would pass intact through the intestinal mucisa and be sequentially converted to 5-FU by enzymes that are highly expressed in the human liver and then in tumors. Among various N4-substituted 5'-deoxy-5-fluorocytidine derivatives, a series of N4-alkoxycarbonyl derivatives were hydrolyzed to 5'-deoxy-5-fluorocytidine (5'-DFCR: 8) specifically by carboxylesterase, which exists preferentially in the liver in humans and monkeys. Particularly, derivatives having an N4-alkoxylcarbonyl moiety with a C4-C6 alkyl chain were the most susceptible to the human carboxylesterase. Those were then converted to 5'-deoxy-5-fluorouridine (5'-DFUR: 4) by cytidine deaminase highly expressed in the liver and solid tumors and finally to 5-FU by thymidine phosphorylase (dThdPase) preferentially located in tumors. When administered orally to monkeys, a derivative having the N4-alkoxylcarbonyl moiety with a C5 alkyl chain (capecitabine: 6) The highest AUC and Cmax for plasma 5'-DFUR. In tests with various human cancer xenograft models, capecitabine was more efficacious at wider dose ranges than either 5-FU or 5'-DFUR and was significantly less toxic to the intestinal tract than the others in monkeys.

Administration, Oral↗
PubMed2000

Growth inhibition of human glioma cells by transfection-induced P21 and its effects on telomerase activity.

The aim of this study is to investigate the effect of the p21 gene transfection on the growth of cultured human glioma cell lines, and analyze the telomerase activity, and detection of telomerase components in p21 transfectant. The p21 gene was transfected into human glioma cell lines, U251MG and T98G with our novel liposome. The cell growth was assessed by counting the number of trypan blue-excluding cells in a hemocytometer and flow cytometry analysis. The expression of P21 protein and its mRNA were examined by Western and Northern blot analysis. The telomerase activity was assayed by TRAP (telomerase repeat amplification protocol)/TRAP-HPA (hybridization protection assay) method qualitatively and quantitatively. The length of telomere was measured by Southern blot analysis. The expression of telomerase components (hTERT, hTERC and TEP1) were examined by RT-PCR (reverse transcriptase-polymerase chain reaction). The p21 transfectant demonstrated the expression of P21 protein and its mRNA. The p21 transfection of human glioma cells results in growth inhibition and G0/G1 arrest. The p21 transfectant revealed a decrease of telomerase activity and hTERT expression as compared with control cells. These results suggest that p21 transfection induces G0/G1 arrest in human glioma cells which associates with the reduction in the telomerase activity and hTERT expression.

Blotting, Northern↗
PubMed2000

Characterization and transduction of a retroviral vector encoding human interleukin-4 and herpes simplex virus-thymidine kinase for glioma tumor vaccine therapy.

Vaccination with cytokine-transduced tumor cells represents a potentially important approach to the treatment of central nervous system tumors. We have recently demonstrated the therapeutic efficacy of tumor cell vaccines expressing the murine interleukin 4 (IL-4) and the herpes simplex virus-thymidine kinase in a rat brain tumor model in which nonirradiated vaccine cells can be eliminated by the subsequent administration of ganciclovir. In this report, we demonstrate the construction and characterization of a retroviral vector that encodes human IL-4, neomycin phosphotransferase, and herpes simplex virus-thymidine kinase genes for use in human clinical trials. An MFG-based retroviral vector was used to generate the recombinant retrovirus, TFG-hIL4-Neo-Tk, in which a long terminal repeat-driven polycistronic transcript encodes three cDNAs that are linked and coexpressed using two intervening internal ribosome entry site fragments from the encephalomyocarditis virus. The amphotropic retroviral vector TFG-hIL4-Neo-Tk was then used to infect human primary glioma cultures and skin-derived fibroblasts. After infection and G418 selection, cells produced 89-131 ng/10(6) cells/48 hours of human IL-4, which was determined to be biologically active. Transduced glioma cells were highly sensitive to the cytotoxic effect of ganciclovir. These data demonstrate the suitability of the TFG-hIL4-Neo-Tk vector for therapeutic studies of cytokine-transduced autologous tumor vaccination in patients with malignant gliomas.

Animals↗
PubMed2000

Feasibility of CTLA4Ig gene delivery and expression in vivo using retrovirally transduced myeloid dendritic cells that induce alloantigen-specific T cell anergy in vitro.

Dendritic cells (DC) are highly specialised, bone marrow (BM)-derived antigen-presenting cells (APC) that initiate and regulate immune responses. They provide costimulatory signals (in particular, CD40 and the CD28 ligands CD80 and CD86) necessary for naive T cell activation. Functional expression of CD80 and CD86 is blocked by the fusion protein cytotoxic T lymphocyte antigen 4-immunoglobulin (CTLA4Ig), that promotes tolerance induction in animals. Here, replicating mouse (B10; H2b) myeloid DC progenitors, were retrovirally transduced to express CTLA4Ig using the centrifugal enhancement method. Gene product was detected by immunocyto- or histochemistry. Maximal DC transduction efficiency was 62%. Compared with control, zeomycin-resistance gene (Zeo)-transduced DC, CTLA4Ig-expressing cells showed markedly impaired capacity to stimulate naive allogeneic (C3H; H2k) T cell proliferation and cytotoxic T lymphocyte (CTL) generation. Their ability to induce alloantigen-specific T cell hyporesponsiveness was reversed by exogenous IL-2 in secondary mixed leukocyte reactions (MLR). Following local (s.c.) transfer to allogeneic recipients, the genetically modified DC trafficked to T cell areas of draining lymphoid tissue, where transgene expression was detected. Ex vivo analysis of proliferative and CTL responses revealed donor-specific inhibition of alloimmune reactivity by the CTLA4Ig-transduced DC. This effect was associated with marked inhibition of interferon (IFN)-gamma production, but significant augmentation of IL-4 and IL-10 secretion. Thus, retroviral transduction of DC permits in vivo delivery of CTLA4Ig to the precise microenvironment where antigen (Ag) presentation occurs. Comparatively nonimmunogenic retroviral vectors, that allow permanent transgene expression in DC, and promote localized delivery of the immunosuppressive transgene product, promote immune deviation and Ag-specific T cell hyporesponsiveness.

Abatacept↗
PubMed2000

Deep venous thrombosis and pulmonary thromboembolism associated with a huge uterine myoma--a case report.

A 51-year-old woman with a large uterine myoma suffered from acute pulmonary thromboembolism. Venography revealed thrombosis in the right common iliac vein and almost complete obstruction of the left common iliac vein. The ascending lumbar vein showed collateral drainage. Treatment was initiated with continuous intravenous heparin sodium, and a Greenfield filter was inserted to prevent the extension of the pulmonary embolism during and after hysterectomy. After a total hysterectomy, venography revealed restoration of patency in the bilateral common iliac veins, and no flow was seen in the ascending lumbar vein. Thorough clinical examinations failed to identify any other prothrombotic conditions. These results suggest that a large uterine myoma compressed veins in the pelvis, and the resulting impaired blood flow caused deep venous thrombosis and pulmonary thromboembolism.

Female↗
PubMed2000

Rare somatic inactivation of the multiple endocrine neoplasia type 1 gene in secondary hyperparathyroidism of uremia.

The molecular pathway of autonomous growth of the parathyroid glands in uremic patients is poorly understood. Loss of heterozygosity at the recently identified multiple endocrine neoplasia type 1 (MEN1) gene locus on chromosome 11q13 has been found in a subset of parathyroid glands from patients with refractory hyperparathyroidism. To clarify the role of the MEN1 gene in parathyroid tumorigenesis, we analyzed 81 parathyroid glands from 22 Japanese uremic patients for allelic loss on chromosomal arm 11q13 DNA using 3 flanking markers (PYGM, D11S4946, and D11S449) and for mutations of the MEN1-coding exons by PCR-based single strand conformation polymorphism analysis and sequencing. Allelic loss on 11q13 was observed in 6 glands (7%), and 1 of 6 demonstrated a previously unrecognized somatic frameshift deletion (331delG) of the MEN1 gene. This mutation would probably result in a nonfunctional menin protein, consistent with a tumor suppressor mechanism. Clinical and pathological characteristics of hyperparathyroidism were unrelated to the presence or absence of loss of heterozygosity on 11q13 and MEN1 gene mutations. These observations indicate that somatic inactivation of the MEN1 gene contributes to the pathogenesis of uremia-associated parathyroid tumors, but its role in this disease appears to be very limited.

Chromosome Mapping↗
PubMed2000

Persistent increase in bone turnover in Graves' patients with subclinical hyperthyroidism.

Hyperthyroid patients exhibit accelerated bone loss by increased bone turnover, and normalization of thyroid function is associated with a significant attenuation of increased bone turnover, followed by an increase in bone mineral density. However, of patients with Graves' disease (GD) maintained on antithyroid drug (ATD) treatment, some exhibit persistent suppression of TSH long after normalization of their serum free T3 (FT3) and free T4 (FT4) levels. The aim of this study was to examine whether bone metabolism is still enhanced in TSH-suppressed premenopausal GD patients with normal FT3 and FT4 levels after ATD therapy (n = 19) compared with that in TSH-normal premenopausal GD patients (n = 30), and to evaluate the relationship between serum TSH receptor antibody (TRAb), an indicator of disease activity of GD, and various biochemical markers of bone metabolism. No difference was found between the two groups in serum Ca, phosphorus, or intact PTH, or in urinary Ca excretion. Serum bone alkaline phosphatase (B-ALP), bone formation markers, and urinary excretions of pyridinoline (U-PYD) and deoxypyridinoline (U-DPD), which are bone resorption markers, were significantly higher in the TSH-suppression group than in the TSH-normal group (B-ALP, P < 0.05; U-PYD, P < 0.001; U-DPD, P < 0.001). For the group of all GD patients enrolled in this study, TSH, but neither FT3 nor FT4, exhibited a significant negative correlation with B-ALP (r = -0.300; P < 0.05), U-PYD (r = -0.389; P < 0.05), and U-DPD (r = -0.446; P < 0.05), whereas TRAb exhibited a highly positive and significant correlation with B-ALP (r = 0.566; P < 0.0001), U-PYD (r = 0.491; P < 0.001), and U-DPD (r = 0.549; P < 0.0001). Even in GD patients with normal TSH, serum TRAb was positively correlated with B-ALP (r = 0.638; P < 0.001), U-PYD (r = 0.638; P < 0.001), and U-DPD (r = 0.641; P < 0.001). In conclusion, it is important to achieve normal TSH levels during ATD therapy to normalize bone turnover. TRAb was not only a useful marker for GD activity, but was also a very sensitive marker for bone metabolism in GD patients during ATD treatment.

Adult↗
PubMed2000

Telomerase activity in primary and secondary glioblastomas multiforme as a novel molecular tumor marker.

OBJECT: Telomerase activity is responsible for cell immortality. To examine the role of telomerase in the carcinogenesis of human glioblastomas multiforme (GBMs), the authors studied telomerase activity, telomerase component expression, and telomere lengths in 42 GBM samples. METHODS: In all samples, EGFR and MDM2 amplifications and overexpressions were examined using Southern and Northern blot analyses. The p53 mutation was analyzed using polymerase chain reaction-single strand conformational polymorphism and by direct sequence analysis. Specimens of tissues were immunostained with p53, EGFR, and MDM2 antibodies. Allelic loss on chromosomes 17p and 10 was assessed by loss of heterozygosity (LOH) assays. Telomerase activity, expression of its components (human telomerase reverse transcriptase [hTERT], human telomerase RNA component [hTERC], and telomerase-associated protein [TEP1]), and telomere lengths were analyzed using the telomeric repeat amplification protocol (TRAP)-hybridization protection assay, reverse transcription-polymerase chain reaction, and Southern blot analysis. According to the results of assessments of EGFR and MDM2 amplifications, p53 mutation, LOHs in chromosomes 17p and 10, and the clinical course of the disease, the 42 samples were classified into 22 primary and 20 secondary glioblastomas. Twenty-six (61.9%) of all 42 samples demonstrated detectable telomerase activity during the TRAP assay. Secondary GBMs displayed significantly higher levels of telomerase activity and hTERT expression than primary GBMs. Tumors with a p53 gene mutation demonstrated significantly higher telomerase activity than those without a p53 mutation. Four samples with a codon 175 mutation demonstrated an exceptionally high amount of telomerase activity. In secondary GBMs, the increase in telomerase activity and the hTERT expression level correlated with the increased frequency of p53 mutations. There was no significant difference in telomere length between primary and secondary GBMs. CONCLUSIONS: These results suggest that telomerase activity and p53 mutations both play important roles in the multistep carcinogenesis of GBMs. Telomerase activity and hTERT expression may be considered as novel distinctive factors in human GBMs.

Aged↗
PubMed2000

Cloning of a human hepatocyte growth factor/scatter factor transcription variant from a gastric cancer cell line HSC-39.

A new transcription variant of hepatocyte growth factor/scatter factor (HGF/SF) was cloned from human gastric cancer cell line HSC-39. Northern blot analysis of eight human gastric cancer cell lines (TMK-1, MKN-1, MKN-7, MKN-28, MKN-45, MKN-74, KATO-III and HSC-39) demonstrated that HSC-39 cells expressed a 1.3 kb abnormal HGF/SF transcript. Screening of 1 x 10(6) colonies of cDNA library from HSC-39 constructed in pAP3neo mammalian expression vector selected four positive clones containing HGF/SF transcript. Among them, two contained a 1.3 kbp insert detecting the identical transcript to that obtained with HGF/SF probe by Northern blotting. Deoxynucleotide sequencing of the 1.3 kbp insert revealed that it was composed of a part of HGF/SF cDNA from exon 14 to exon 18, corresponding to the whole sequence of HGF/SF light chain, with 5' 75 nucleotides unrelated to any sequence involved in HGF/SF.

Base Sequence↗
PubMed2000

Interleukin-2: developing additional cytokine gene therapies using fibroblasts or dendritic cells to enhance tumor immunity.

PURPOSE: Recombinant interleukin (IL)-2 administration can mediate regression of solid tumors in patients with melanoma and renal cell carcinoma. A better understanding of the mechanisms of IL-2-mediated antitumor effects has led to the investigation of novel immunotherapeutic approaches. The rationale for these immunotherapeutic approaches and the results of preliminary clinical studies are presented. PATIENTS AND METHODS: The therapeutic potential of dendritic cells and the role of FLT3 ligand, a potent hematopoietic growth factor, was investigated in a variety of preclinical models. In addition, a clinical study with autologous dendritic cells pulsed with synthetic melanoma peptides derived from the MART1/ Melan A, gp100, and tyrosinase proteins was conducted. Twenty-eight human leukocyte antigen (HLA)-A2+ melanoma patients received an average of 106 dendritic cells a week for 4 weeks. RESULTS: In a murine liver metastases model, FLT3 ligand administration alone or in combination with IL-12 or IL-2 had significant antitumor effects and resulted in significant infiltration of the tumor border by lymphocytes and dendritic cells, which was associated with an increased number of apoptotic figures. Administration of melanoma peptide-pulsed dendritic cells to 28 patients with advanced metastatic melanoma produced a complete response in two patients and a partial response in one. Significant infiltration of T cells and dendritic cells into melanoma lesions was observed. CONCLUSION: These studies confirm the feasibility of immunotherapeutic approaches using dendritic cells and FLT3 ligand and demonstrate their potential antitumor activity. These approaches may be effective for patients with metastatic melanoma and other solid tumors and will likely be used to improve the efficacy of IL-2-based immunotherapy.

Cancer Vaccines↗
PubMed1999

Transduction of dendritic cell progenitors with a retroviral vector encoding viral interleukin-10 and enhanced green fluorescent protein allows purification of potentially tolerogenic antigen-presenting cells.

BACKGROUND: Dendritic cells (DC) are important antigen-presenting cells that play critical roles in the initiation and modulation of immune responses. Genetic engineering of DC to express immunosuppressive molecules is a novel approach to the inhibition of allograft rejection. Retroviral delivery of viral interleukin (vIL)-10 to replicating myeloid DC progenitors (DCp) impairs their T-cell stimulatory capacity and promotes the induction of antigen-specific T-cell hyporesponsiveness. However, transduction efficiency with retroviral vectors is comparatively low. Enhanced green fluorescent protein (EGFP) is important both as a marker of gene transduction and for the selection of transduced cells. Our aims were to construct a retroviral vector encoding both vIL-10 and EGFP, to positively select transduced DC, and to assess the impact of these highly purified, vIL-10-secreting antigen-presenting cells on allogeneic T-cell responses. METHODS: DCp propagated from bone marrow of C57BL10 (H2b) mice in granulocyte-macrophage colony-stimulating factor (GM-CSF)+IL-4 were transduced with a retroviral vector encoding both vIL-10 and EGFP by centrifugal enhancement. Gene transfer efficiency was determined by flow cytometry. Transduced cells were flow sorted, and vIL-10 secretion was quantified by ELISA. DC function was assessed by the ability of the cells to induce naive allogeneic (C3H; H2k) T-cell proliferation and cytotoxic T lymphocyte generation. RESULTS: Retrovirally transduced DC expressed both vIL-10 and EGFP gene products. Approximately 20% of unsorted cells expressed EGFP, as determined by flow cytometry. vIL-10 was produced at a mean rate of 31 ng/40 hr/10(6) cells. After sorting, the incidence of EGFP+ DC was increased dramatically to at least 95%, and the production of vIL-10 was increased approximately three- to fourfold, to a mean of 107 ng/40 hr/10(6) cells. These highly purified, vIL-10-secreting DC exhibited markedly diminished capacity to induce allogeneic T-cell proliferative and cytotoxic responses. CONCLUSIONS: DCp retrovirally transduced to express both vIL-10 and EGFP can be rapidly identified and sorted to high levels of purity. The availability of highly enriched preparations of vIL-10-transduced DC facilitates studies of their immunoregulatory function and may enhance their therapeutic potential in transplantation or autoimmune disease.

Animals↗
PubMed1999

Telomerase activity in hybrids between telomerase-negative and telomerase-positive immortal human cells is repressed in the different complementation groups but not in the same complementation group of immortality.

The expression of telomerase is essential for cells to be immortalized, and most immortal cell lines possessed telomerase activity. Using the cell fusion technique, it has been shown that mortal and telomerase-negative phenotypes of normal cells are dominant over immortal and telomerase-positive phenotypes, suggesting that the normal cells possessed dominant repressor-type activity for telomerase expression. Several telomerase-negative immortal human cell lines were reported, in which telomerase-independent mechanisms was supposed to maintain telomere length. We aimed at seeing whether the telomerase-negative phenotype of these immortal cells is dominant over telomerase-positive phenotype of other immortal cells in correlation with cellular mortality. Results showed that, when telomerase-positive and -negative immortal parental cell lines belonging to the different complementation groups were fused, telomerase-negative mortal hybrid clones arose, i.e. telomerase-negative phenotype was dominant as well as mortal phenotype. However, when immortal hybrid cells arose from telomerase-positive and -negative immortal parents belonging to either the same or different complementation groups, they were all telomerase-positive, i.e. telomerase-negative phenotype appeared to be recessive. Telomerase-negative immortal hybrid was never established from any combinations between telomerase-negative and -positive immortal parental cells.

Base Sequence↗
PubMed1999

Telomerase activity in central nervous system malignant lymphoma.

BACKGROUND: Primary central nervous system malignant lymphoma (PCNSL) has been regarded as a rare neoplasm. Recently, however, its incidence has been rapidly increasing. Despite active clinical trials, its clinical and biologic features remain unknown and there has been no effective treatment or prognostic factor. The current study attempted to elucidate telomerase activity and expression of the telomere-related RNA of PCNSL as novel prognostic factors. METHODS: The subjects were 12 patients with histologically diagnosed PCNSL. All patients were treated with chemoradiotherapy consisting of whole-brain radiation, vincristine, etoposide, and prednisolone. Telomerase activity in the resected tumor was analyzed both qualitatively and quantitatively using the TRAP (telomeric amplification assay protocol)/TRAP-HPA (hybridization protection assay) method. The expression of telomere-related RNA (hTERT, hTERC, and TEP1) was analyzed by reverse transcriptase-polymerase chain reaction. RESULTS: Telomerase activity was detected in 10 of 12 patients with PCNSL, with an average activity of 148.9 relative light units. The average telomere length was 5.55 kb. The expression of hTERT correlated with telomerase activity, and there was a statistically significant correlation between telomerase activity and both the duration of survival and the interval to tumor progression. CONCLUSIONS: Telomerase activity and the expression of hTERT may be novel prognostic factors in patients with PCNSL.

Adult↗