Biomedical subjects

H Tahara

Publications and source records attributed to H Tahara.

At least 73 records · Page 4Linked to original sources

PubMed1999

Induction of systemic and therapeutic antitumor immunity using intratumoral injection of dendritic cells genetically modified to express interleukin 12.

Bone marrow-derived dendritic cells (BM-DCs) retrovirally transduced with genes encoding murine interleukin (IL)-12 stably expressed bioactive IL-12 protein at high levels. Intratumoral injection with IL-12 gene-modified BM-DCs resulted in regression of day 7 established weakly immunogenic tumors (MCA205, B16, and D122). This antitumor effect was substantially better than that of IL-12-transduced syngeneic fibroblasts or nontransduced BM-DCs. Furthermore, intratumoral injection with IL-12-transduced dendritic cells (DCs) induced specific TH1-type responses to the tumor in regional lymph nodes and spleen at levels greater than those of IL-12-transduced fibroblasts or nontransduced BM-DCs. Trafficking studies confirmed that intratumorally injected IL-12-transduced DCs, but not fibroblasts, could migrate to the draining lymph node to the same extent as nontransduced BM-DCs. This strategy designed to deliver genetically modified DCs to tumor sites is associated with systemic and therapeutic antitumor immunity and is an alternative approach to those that use delivery of DCs loaded with tumor antigen. These results support the clinical application of IL-12 gene-modified DCs in patients with cancer.

Animals↗

PubMed1999

Differential antitumor effects of administration of recombinant IL-18 or recombinant IL-12 are mediated primarily by Fas-Fas ligand- and perforin-induced tumor apoptosis, respectively.

Systemic administration of rIL-18 protein to mice significantly suppresses the growth of murine tumor cell lines. The antitumor effect of IL-18 appears to be primarily mediated by asialo GM1+ cells. Since IL-18 enhances Fas ligand (FasL) expression on NK cell lines, the IL-18 antitumor effects could be mediated by FasL-induced cross-linking of Fas and subsequent tumor apoptosis. To address this question, rIL-18 or rIL-12 was administered to animals bearing the CL8-1 melanoma inoculated intradermally into wild type (wt), lymphoproliferation gene (lpr) (Fas deficient), or generalized lymphoproliferative disease gene (gld) (FasL deficient) mice. Although rIL-12 treatment retained significant antitumor effects in gld and lpr mice, those of rIL-18 administration were completely abrogated in gld but not lpr or wt mice. In vitro cytotoxicity was significantly enhanced against NK-sensitive YAC-1 cells and CL8-1 cells by rIL-18 administration to wt mice, but not to gld mice. Furthermore, rIL-18 administration augmented the cytotoxicity of liver lymphocytes harvested from perforin-deficient mice, whereas rIL-12 administration did not. Consistent with the role of this pathway, rIL-18 administration also up-regulates the expression of FasL mRNA in splenocytes. Lysis of CL8-1 cells induced by anti-Fas agonistic Ab was enhanced about 1.4-fold by IFN-gamma, a cytokine that is induced by IL-18 in vitro and in vivo. We conclude that the antitumor effect of IL-18 is exerted predominantly through a Fas-dependent pathway. The perforin pathway, however, appears to be the predominant cytolytic pathway mediating IL-12 antitumor effects.

Adjuvants, Immunologic↗

PubMed1999

Immuno-histochemical detection of human telomerase catalytic component, hTERT, in human colorectal tumor and non-tumor tissue sections.

Human telomerase is expressed in germ tissues and in the majority of primary tumors. Cell renewal tissues and some pre-cancerous tissues also have weak telomerase activity. Yet, neither the exact location and frequency of telomerase-positive cells nor the changes in telomerase expression during differentiation or carcinogenesis of individual cells are known. This paper reports on the expression of hTERT (telomerase reverse transcriptase) protein in tumor and non-tumor colorectal tissues by Western blotting and tissue sections by immunohistochemistry using antibodies raised against partial peptides of hTERT. Though telomerase activity and hTERT expression at both mRNA and protein levels were generally higher in tumor part than in non-tumor part, these two were not always correlated: expression of hTERT did not always give rise to high telomerase activity. Colonic carcinoma cell nuclei were stained with anti-hTERT antibodies but not with antigen-preabsorbed antibodies. In normal mucosa, hTERT protein was expressed, though weaker than in carcinoma, in all colonic crypt epithelial cells except those at the tip; the expressing-cell distribution was much wider than that of Ki-67 positive cells which were located at the bottom of the crypt. Isolated crypt contained a significant level of hTERT protein revealed by Western blotting, while having very weak telomerase activity. Telomerase activity was detected in epithelial cells only at the bottom half of the crypt. Specific hTERT-staining was positive in tissue lymphocytes but negative in almost all other stromal cells. It is of interest to see whether a significant level of hTERT expression with low telomerase activity is characteristic of physiologically regenerating tissues containing stem cells. In situ detection of the hTERT protein will permit further analysis of cancer diagnosis and stem cell differentiation.

Blotting, Western↗

PubMed1999

Effect of antisense human telomerase RNA transfection on the growth of human gastric cancer cell lines.

The majority of gastric cancers express high levels of human telomerase template RNA (hTR) that is essential for cellular survival. In this study, we examined whether antisense hTR (ahTR) had a growth inhibitory effect on three gastric cancer cell lines, MKN-1, MKN-28, and TMK-1, through transfection via an ahTR expression vector. Both the ahTR transfected MKN-1 and TMK-1 cells changed morphologically into multinucleate giant cells, and subsequently underwent cell death. Conversely, the ahTR transfected MKN-28 cells survived over 50 PDs in spite of telomere shortening. Surprisingly, high levels of telomerase activity were observed in the telomere-reduced cells. Furthermore, the expression of mRNAs for p21/Waf1/Cip1/Sdi1, IRF-1 and IFN inducible 6-16 was higher in the telomere-reduced cells than in the parental cells. These results suggest overall that the ahTR expression may bring about telomere shorting, leading to cell death or cellular senescence in gastric cancer cells.

Cell Cycle↗

PubMed1999

Plasma fatty acids concentrations in postoperative patients with biliary atresia.

The concentrations of plasma fatty acids in postoperative patients with biliary atresia (BA) were measured to clarify whether they had essential fatty acid deficiency. Thirty-eight fasting blood samples from 14 postoperative patients with BA were studied. All of them had the hepatic portoenterostomy without any stoma. Samples were divided into three groups on the basis of liver function. The concentrations of fatty acids in the plasma fat were measured quantitatively. Non-essential fatty acids levels were increased and omega-3 fatty acids levels were decreased with the progress of deterioration of hepatic function. Regarding omega-6 fatty acids, C18:2 and 20:4 did not show any significant difference between the three groups and the control, and only C20:3 increased with the deterioration of liver dysfunction. The ratio of C20:3 (omega-6) to C20:4 (omega-6) was increased significantly with the progress of liver dysfunction. The activity of delta-5 desaturase was suspected to be suppressed in BA patients with poor liver function. The BA patients with poor bile flow did not show any decrease of omega-6 fatty acids in the plasma, but were at risk of developing omega-3 fatty acid deficiency.

Biliary Atresia↗

PubMed1999

Effective cytokine gene therapy against an intracranial glioma using a retrovirally transduced IL-4 plus HSVtk tumor vaccine.

To explore the potential for molecular immunotherapies in the treatment of malignant gliomas, we evaluated the efficacy of subcutaneous tumor cell vaccines in the treatment of intracranial 9L tumors, using 9L gliosarcoma cell lines stably transduced with the murine interleukin-4 cDNA (9L-IL4), the herpes simplex virus-thymidine kinase cDNA (9L-Tk) or both (9L-IL4-Tk). The expression of multiple genes from a single transcript was achieved by incorporating internal ribosomal entry site (IRES) cassettes in the retroviral constructs. Subcutaneous immunization of rats with nonirradiated 9L-IL4 cells or 9L-IL4-Tk cells followed by treatment with ganciclovir (GCV) completely protected the animals from a subsequent intracranial challenge with wild-type 9L cells. In contrast, only 50% of animals immunized with 9L-Tk cells and 0% of 9L-neo immunized animals rejected the same challenge with wild-type 9L. More importantly, treatment of established (day 3) intracranial 9L tumors with genetically engineered tumor cells resulted in long-term survival (> 100 days) for 25-43% of 9L-IL4-Tk immunized animals and for 27% of nonirradiated 9L-IL4 immunized animals. In striking contrast, no 9L-Tk, 9L-neo or irradiated 9L-IL4 immunized animals survived for more than 33 days. As a marker of a cellular immune response, splenocytes from nonirradiated 9L-IL4, 9L-Tk or 9L-IL4-Tk immunized animals produced interferon-gamma (IFN-gamma) in greater amounts than those from 9L-neo immunized or Hank's balanced salts solution (HBSS) treated animals when stimulated with wild-type 9L in vitro. Our findings support the use of tumor cell vaccines expressing the IL-4 and HSVtk genes for the treatment of malignant gliomas.

Animals↗

PubMed1999

Potent antitumor effects mediated by local expression of the mature form of the interferon-gamma inducing factor, interleukin-18 (IL-18).

IL-18 is produced during the acute immune response by macrophages and immature dendritic cells. IL-18 receptors are induced on T cells and NK cells by IL-12 and together they enhance a cellular immune response. We constructed retroviral and adenoviral vectors encoding the mature bioactive murine IL-18 in order to examine their immune and antitumor effects in murine tumor models. Secretion of bioactive IL-18 from murine tumor cells was facilitated by transfecting them with recombinant viral vectors carrying the prepro leader sequence of human parathyroid hormone fused to the 5' end of the mature murine IL-18 cDNA. Direct injection of the IL-18 recombinant adenoviral vector (Ad.PTH.IL-18) into an established MCA205 murine fibrosarcoma completely eradicated tumor in all animals with concomitant induction of protective systemic immunity. Co-administration of systemic IL-12 provided synergistic antitumor effects when combined with peritumoral injections of Ad.PTH.IL-18 without apparent side-effects as we observed with systemic administration of IL-18. Depletion of asialo GM-1+ cells completely abrogated the antitumor effects of Ad.PTH.IL-18, suggesting a major role for NK cells in mediating the anti-tumor effects of IL-18. Peritumoral injection of Ad.PTH.IL-18 was also associated with reduced numbers of CD8+ cells found within the tumor (HBSS versus Ad.PTH.IL-18, P < 0.0001). This suggests that IL-18 could be utilized as an alternative cancer gene therapy especially when combined with systemic administration of IL-12.

Adenoviridae↗

PubMed1999

Interferon-alpha gene therapy in combination with CD80 transduction reduces tumorigenicity and growth of established tumor in poorly immunogenic tumor models.

Interferon-alpha (IFN-alpha) or CD80 transduction of tumor cells individually reduces tumorigenicity and enhances antitumor responses. Here, we report that the combination of IFN-alpha and CD80 cancer gene therapy in poorly immunogenic murine tumor models, the colorectal adenocarcinoma cell line MC38, and the methylcholanthrene-induced fibrosarcoma cell line MCA205 reduces tumor growth more efficiently without affecting in vitro growth. Wild-type (WT), neomycin-resistance (Neo) gene-, or CD80-transduced tumor cells grew progressively in all immunocompetent mice. In contrast, IFN-alpha-transduced MC38 or MCA205 cells were rejected in 13 of 15 and seven of 15 mice, respectively. Synergistic effects were observed when IFN-alpha- and CD80-transduced tumor cells were mixed and inoculated. These admixed cells were rejected by 14 of 15 (MC38) or seven of 15 mice (MCA205), whereas, a mixture of IFN-alpha and Neo cells or CD80 and Neo cells led to tumors associated with progressive growth. Induction of long-lasting tumor immunity against WT tumor cells was demonstrated by rejection of a subsequent rechallenge in 10 of 13 (MC38) and six of seven (MCA205) tumor-free mice. The therapeutic efficacy with established WT MC38 tumors was shown when mice were treated with a vaccine consisting of repetitive injections of IFN-alpha- and CD80-transduced MC38 cells into the contralateral flank (P < 0.01). This treatment was associated with accumulation of CD4+, CD8+ cells and dendritic cells within the established tumor, demonstrating induction of antitumor immune responses. Combination gene therapy using IFN-alpha and CD80 is an effective immune therapy of cancer and could be considered for clinical trials.

Animals↗

PubMed1999

Molecular-pathological diagnosis of gastrointestinal tissues and its contribution to cancer histopathology.

Multiple genetic and epigenetic alterations of cancer-related genes and molecules are involved in the course of the development and progression of gastrointestinal cancers. These include telomerase activation, genetic instability, and abnormalities of oncogenes, tumor suppressor genes, cell cycle regulators, cell adhesion molecules and DNA repair genes. By analyzing these alterations in pathology specimens, we can improve differential diagnosis of cancer, obtain information of grade of malignancy, and identify patients at high risk for developing multiple primary cancers. Since 1993, a system of molecular-pathological diagnosis was established, and has been performed as a routine service in collaboration with Hiroshima City Medical Association Clinical Laboratory. More than 10 000 cases of gastrointestinal biopsy and surgery have been analyzed, and additional information of differential diagnosis, biological malignancy and tumor multiplicity could be obtained. Molecular-pathological diagnosis may provide a new approach to cancer diagnosis and novel therapeutics for the 21st century. Furthermore, the analysis of the genetic and epigenetic abnormalities in clinical materials may clarify the molecular mechanism of carcinogenesis and comparative morphological changes. From the analyses of p27KIP1 and telomerase in gastrointestinal adenomas, we have learned that morphological abnormality of the nucleus is an indicator for cells with immortality and malignant potential that must participate in super-early diagnosis (detection of true precancerous lesions) of gastrointestinal cancer. Molecular-pathological diagnosis thus contributes to detailed understanding of cancer histopathology and improves the histopathological diagnosis.

Adenocarcinoma↗

PubMed1999

Immunohistochemical detection of human telomerase reverse transcriptase in normal mucosa and precancerous lesions of the stomach.

Telomerase activity confers cell immortality through stabilization of the chromosome, participating in the development of a majority of human cancers. Human telomerase reverse transcriptase (TERT) has been identified as a catalytic subunit of telomerase, and is overexpressed in most gastric carcinomas. We immunohistochemically examined the expression of TERT in normal gastric mucosa and candidate precancerous lesions such as intestinal metaplasia and adenoma. In non-neoplastic gastric mucosa including intestinal metaplasia and normal fundic mucosa, weak but significant expression of TERT was detected in nuclei of epithelial cells located in the lower two-thirds of the glands (wider than the proliferative zone). The telomerase activity was found in a half of gastric adenomas, whose levels of the activity were about 10% of those in gastric carcinomas. TERT protein was expressed in the nuclei of the adenoma cells at moderate levels, that were not necessarily comparable with the telomerase activities. These findings overall suggest that TERT expression may be one of the prerequisites for telomerase activation in an early stage of stomach carcinogenesis.

Adenoma↗

PubMed1999

Multilocular cystic adenomyoma of the pelvic cavity: A rare clinical and histological entity in a young man.

We report a large complex cystic pelvic mass encountered in a 16-year-old man complaining of perineal discomfort. A large and elastic hard mass was palpated on the right anterior wall of the rectum with no discernible prostate on digital rectal examination. Prostatic tumor markers were elevated. Excretory urography and urethrocystography showed a filling defect with a smooth edge on the right side of the bladder. Magnetic resonance imaging demonstrated a mass with a mosaic pattern between the right side of the bladder and the rectum. We performed ultrasound-guided transrectal needle core biopsy of the mass. The pathologist suspected hyperplastic glandular epithelium of prostatic origin with focal inflammatory cell infiltration, but there was no sign of malignancy. We thought that the tumor arose from the prostate. Surgery was successfully performed. The tumor was located on the right side of the pelvic cavity and adhered to the right lobe of the seminal vesicle. En bloc excision was performed. This lesion histologically proved to be a multilocular prostatic tissue with a seminal vesicle component, without communication to the surrounding tissue. Such a lesion has not previously been reported in the literature.

Adenomyoma↗

PubMed1999

Effects of high temperature on the emergence and survival of adult Culex pipiens molestus and Culex quinquefasciatus in Japan.

The emergence rate and adult survival (longevity) of Japanese strains of Culex pipiens molestus and Culex quinquefasciatus were compared at temperatures of 21, 25, and 30 degrees C. The pupation and emergence rates in both strains were higher at 21 and 25 degrees C than at 30 degrees C. The adult emergence rate, especially in females, was lower in Cx. p. molestus than in Cx. quinquefasciatus. Longevity of females and males was lower in Cx. p. molestus at 25 degrees C and above. The survival of Cx. p. molestus was adversely affected by temperatures of 28 degrees C and higher. High temperature may restrict the distribution of this species. Therefore, if Cx. p. molestus infests the Okinawa region, the likelihood that it will become established is minimal.

Animals↗

PubMed1999

[Left ventricular relaxation in lone atrial fibrillation and atrial fibrillation with heart disease].

Atrial fibrillation with organic heart disease shows a steady value for the time constant of left ventricular isovolumetric relaxation (TC), whereas left ventricular contractility varies from beat to beat. However, there is no report on left ventricular relaxation in lone atrial fibrillation. This study assessed left ventricular relaxation in 5 patients with lone atrial fibrillation, 3 with ischemic heart disease and one with hypertrophic cardiomyopathy. Left ventricular pressure was recorded at 3 msec intervals, with a high fidelity micromanometer-tipped catheter. Maximal positive dP/dt (dP/dtmax) and TC of isovolumetric left ventricular relaxation period [P(t) = (P0-P infinity) exp (-t/TC) + P infinity] were measured as indices of left ventricular contractility and left ventricular relaxation, respectively. Correlation coefficients of dP/dtmax and TC versus the ratio of the preceding to the pre-preceding RR-interval (RR2/RR1) were calculated. A good correlation was found between dP/dtmax and RR2/RR1 in all patients (r = 0.71-0.84, p < 0.0001). No correlation between TC and RR2/RR1 was found in patients with atrial fibrillation with organic heart disease, but a good correlation was found between TC and RR2/RR1 in patients with lone atrial fibrillation (r = 0.74-0.95, p < 0.0001). The correlation between TC and RR2/RR1 is well preserved in lone atrial fibrillation. The mechanism of the variation of TC with the RR2/RR1 interval in lone atrial fibrillation may be similar to the change of TC in postextrasystolic potentiation, which is attributed to the change of intracellular Ca2+ concentration. Absence of correlation between TC and RR2/RR1 interval may indicate that left ventricular relaxation is disturbed in patients with atrial fibrillation with organic heart disease.

Aged↗

PubMed1999

Quantitative reevaluation of telomerase activity in cancerous and noncancerous gastrointestinal tissues.

Telomerase activity has been examined extensively in a variety of human cancerous and noncancerous tissues. However, it was sometimes difficult to measure telomerase activity quantitatively with the methods used and in the tissues examined. We examined telomerase activity quantitatively in gastrointestinal tissues by using the hybridization protection assay combined with the telomeric repeat amplification protocol (TRAP) to assess the diagnostic utility of measuring telomerase activity and to determine the relationship between telomerase activity and human telomerase reverse transcriptase (hTERT) expression. We report here that (i) polymerase chain reaction (PCR) inhibitors in the tissue extracts used for the telomerase assay were practically nullified by using tissue extract at 0.1 microg of protein/assay; (ii) RNase activity in tissue extracts should be blocked with 0.5 U of RNase inhibitor/microg tissue protein for the quantitative telomerase assay; (iii) no inhibitors of telomerase were found in tissue extracts other than RNase and PCR inhibitors (iv) higher telomerase activity in cancerous tissue than in noncancerous tissue from the same patients was observed in both gastric and colorectal tissues, but the telomerase activity varied from low to high levels in cancerous tissues, and it was not practical to set a general cut-off level for cancer diagnosis; (v) hTERT was expressed in both cancerous and noncancerous tissues, and (vi) the telomerase activity levels were generally lower than expected from the hTERT expression levels, suggesting posttranscriptional regulation of expression of telomerase activity.

Adenocarcinoma↗

PubMed1998

Retroviral delivery of viral interleukin-10 into myeloid dendritic cells markedly inhibits their allostimulatory activity and promotes the induction of T-cell hyporesponsiveness.

BACKGROUND: Dendritic cells (DC) play critical roles in the initiation and modulation of immune responses and may determine the balance between tolerance and immunity. Viral interleukin-10 (vIL-10), encoded by the Epstein-Barr virus, is highly homologous to the "immunosuppressive" cytokine, mammalian IL-10. It impairs antigen-presenting cell function but lacks certain immunostimulatory properties of mammalian IL-10. We accomplished the following: (1) evaluated the effects of vIL-10 protein on DC phenotype and function, (2) transduced mouse bone marrow-derived DC to express vIL-10, and (3) assessed the impact of transgene expression on DC allostimulatory activity. METHODS: DC progenitors propagated from bone marrow of B10 (H2b) mice in granulocyte-macrophage colony-stimulating factor plus IL-4 were repeatedly transduced by centrifugation, using retroviral supernatant obtained from the BOSC 23 ecotropic packaging cell line. To evaluate transduction efficiency, DC were transduced with the retroviral vector MFG-enhanced green fluorescence protein as a marker gene. Transgene and key cell surface molecule expression were examined by flow cytometry. The level of vIL-10 gene product in the culture supernatant was quantitated by ELISA. DC function was assessed by evaluation of the ability of DC to induce allogeneic (C3H;H2k) T-cell proliferation and cytotoxic T lymphocytes in primary mixed leukocyte reactions. Secondary mixed leukocyte reactions were used to test for T-cell hyporesponsiveness. RESULTS: The early addition of vIL-10 protein to cultures inhibited DC maturation and function. vIL-10 gene transfer was achieved with an approximate transduction efficiency of 35 to 40%. Transduced DC expressed vIL-10 at a level of 40 ng/10(6) cells/48 hr. In comparison with controls, vIL-10-transduced cells showed decreased surface expression of major histocompatibility complex class II and costimulatory molecules, reduced ability to stimulate T-cell proliferation and cytotoxic T lymphocyte generation, and potential to induce alloantigen-specific hyporesponsiveness. CONCLUSIONS: DC can be effectively transduced to express vIL-10 and limit their ability to stimulate in vitro. These genetically engineered antigen-presenting cells may have therapeutic potential to inhibit undesired immune responses to allo- or autoantigens.

Animals↗

PubMed1998

Bone marrow-derived dendritic cells pulsed with a tumor-specific peptide elicit effective anti-tumor immunity against intracranial neoplasms.

Although the central nervous system (CNS) is often regarded as an immunologically privileged site, it is well established that specific CNS immunoreactivity can be generated through peripheral vaccination with CNS antigens. Dendritic cells (DC) are potent antigen presenting cells of hematopoietic origin that have emerged as a promising tool for cancer immunotherapy capable of evoking significant anti-tumor immunity when pulsed with tumor-associated peptides. To explore a role for DC-based immunization strategies for the treatment of CNS tumors, we developed a brain tumor model using the C3 sarcoma cell line which expresses the tumor-specific, major histocompatibility complex (MHC) class I-restricted peptide epitope E7(49-57). Syngeneic C57Bl/6 mice receiving intravenous (i.v.) injections of bone marrow-derived DCs pulsed with E7 peptide were effectively protected against a subsequent intracerebral challenge with C3 tumor cells. More importantly, this systemic immunization strategy was effective in a therapy model as 67% of animals (10 of 15) with established (day 7) intracerebral C3 tumors treated with 3 weekly injections of E7 peptide-pulsed DCs achieved a long-term survival (>90 days) while no control animals survived beyond day 41. In vivo depletion of CD8+ cells, but not CD4+ or asialo-GM1+ cells, abrogated the efficacy of E7 peptide-pulsed DC therapy of established tumors, indicating a pivotal role of specific CD8+ T-cell responses in mediating the anti-tumor effect. Our findings support the hypothesis that effective CNS anti-tumor immunoreactivity can be generated with DC-based tumor vaccines.

Animals↗

PubMed1998

Extra-chromosomal telomere repeat DNA in telomerase-negative immortalized cell lines.

We found novel extra-chromosomal telomere repeat (ECTR) DNAs in telomerase-negative immortalized KMST-6 cells, by staining these cells with a (TTAGGG)n probe using both cycling oligonucleotide-primed in situ synthesis and by fluorescence in situ hybridization. Relatively small amounts of ECTR DNAs were also observed in telomerase-negative VA13 and SUSM-1 cells, but not observed in telomerase-positive immortalized HeLa cells. The ECTR DNAs existed mainly in the nucleoplasm with a small amount in the cytoplasm. The nucleoplasm ECTR DNAs were co-stained with an antibody directed to the telomeric-repeat binding factor 1 (TRF1), suggesting that they exist as a complex with TRF1. In consistent with these cytological studies, Southern blot analysis showed the existence of small telomere repeat DNAs. The ECTR DNA may provide an insight into the elucidation of the mechanisms responsible for the maintenance of telomeres in telomerase-negative immortalized cells.

Cell Line↗

PubMed1998

A hVti1 homologue: its expression depends on population doubling levels in both normal and SV40-transformed human fibroblasts.

A cDNA clone was isolated by differential colony hybridization from a cDNA library prepared from life-extended SV40-transformed human fibroblasts. The clone, tentatively named N-10, was 1272 bp in length coding for 232 amino acids. Northern analysis revealed that the expression level of N-10 was increased in normal senescent and life-extended SV40-transformed fibroblasts than in their young counterparts but was not enhanced by growth arrest. The protein fused to GFP (green fluorescent protein) localized in cytoplasmic granule. Enforced expression of N-10 resulted in premature senescence in young fibroblasts. The deduced amino acid sequence of N-10 was identical to the recently reported hVti1 gene except in one amino acid: Asp24(GAC) was ours and Asn24 (AAC) was reported. Additional base differences were found, so we referred to our sequence as the hVti1 homologue. As hVti1 protein was suggested to be involved in the vesicle transport process, the homologue may be concerned with increased secretion of extracellular matrix and various cytokines associated with cellular senescence.

Carrier Proteins↗