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Biomedical subjects

Satoshi Ohno

Publications and source records attributed to Satoshi Ohno.

At least 19 recordsLinked to original sources
PubMed2007

Site-selective post-translational modification of proteins using an unnatural amino acid, 3-azidotyrosine.

An efficient method for site-selective modification of proteins using an unnatural amino acid, 3-azidotyrosine has been developed. This method utilizes the yeast amber suppressor tRNA(Tyr)/mutated tyrosyl-tRNA synthetase pair as a carrier of 3-azidotyrosine in an Escherichia coli cell-free translation system, and triarylphosphine derivatives for specific modification of the azido group. Using rat calmodulin (CaM) as a model protein, we prepared several unnatural CaM molecules, each carrying an azidotyrosine at predetermined positions 72, 78, 80 or 100, respectively. Post-translational modification of these proteins with a conjugate compound of triarylphosphine and biotin produced site-selectively biotinylated CaM molecules. Reaction efficiency was similar among these proteins irrespective of the position of introduction, and site-specificity of biotinylation was confirmed using mass spectrometry. In addition, CBP-binding activity of the biotinylated CaMs was confirmed to be similar to that of wild-type CaM. This method is intrinsically versatile in that it should be easily applicable to introducing any other desirable compounds (e.g., probes and cross-linkers) into selected sites of proteins as far as appropriate derivative compounds of triarylphosphine could be chemically synthesized. Elucidation of molecular mechanisms of protein functions and protein-to-protein networks will be greatly facilitated by making use of these site-selectively modified proteins.

Amino Acid Sequence↗
PubMed2006

A base pair at the bottom of the anticodon stem is reciprocally preferred for discrimination of cognate tRNAs by Escherichia coli lysyl- and glutaminyl-tRNA synthetases.

Although the yeast amber suppressor tRNA(Tyr) is a good candidate for a carrier of unnatural amino acids into proteins, slight misacylation with lysine was found to occur in an Escherichia coli protein synthesis system. Although it was possible to restrain the mislysylation by genetically engineering the anticodon stem region of the amber suppressor tRNA(Tyr), the mutant tRNA showing the lowest acceptance of lysine was found to accept a trace level of glutamine instead. Moreover, the glutamine-acceptance of various tRNA(Tyr) transcripts substituted at the anticodon stem region varied in reverse proportion to the lysine-acceptance, similar to a 'seesaw'. The introduction of a C31-G39 base pair at the site was most effective for decreasing the lysine-acceptance and increasing the glutamine-acceptance. When the same substitution was introduced into E.coli tRNA(Lys) transcripts, the lysine-accepting activity was decreased by 100-fold and faint acceptance of glutamine was observed. These results may support the idea that there are some structural element(s) in the anticodon stem of tRNA, which are not shared by aminoacyl-tRNA synthetases that have similar recognition sites in the anticodon, such as E.coli lysyl- and glutaminyl-tRNA synthetases.

Amino Acyl-tRNA Synthetases↗
PubMed2006

A phase I/II trial of a WT1 (Wilms' tumor gene) peptide vaccine in patients with solid malignancy: safety assessment based on the phase I data.

OBJECTIVE: We conducted a phase I study to investigate the safety of a weekly WT1 tumor vaccine therapy in patients with solid tumors that had been refractory to all other anti-cancer therapies. METHODS: Skin-test-negative patients were intradermally injected weekly for 12 weeks with 3.0 mg of an HLA-A*2402-restricted modified 9-mer WT1 peptide emulsified in Montanide ISA51 adjuvant. We estimated the Bayesian posterior probability of the occurrence of grade 3 or 4 toxicity when receiving the weekly WT1 vaccination. This analysis provided the basis for making a decision to terminate the phase I study and switch to phase II. Moreover, we performed an exploratory assessment of the anti-tumor effects of WT1 treatment. RESULTS: Ten patients received 114 vaccinations with WT1 on a weekly schedule. No grade 3 or 4 toxicities were observed. Based on the Bayesian approach, it was highly likely that the probability of grade 3 or 4 toxicity was below 20% (the posterior probability = 0.914). Fifteen grade 2 and two grade 1 toxicities were observed; all of these incidents, however, were determined by the Independent Data and Safety Monitoring Committee to be unrelated to the WT1 treatment. One patient exhibited a partial response; five additional patients had stable disease while receiving weekly WT1 treatment. CONCLUSION: This paper confirms that the potential toxicities of the treatment schedule of weekly WT1 vaccination are acceptable and suggested a potential anti-tumor effect. Consequently, we validated the decision to continue to the phase II trial.

Adolescent↗
PubMed2006

High Twist expression is involved in infiltrative endometrial cancer and affects patient survival.

Epithelial-mesenchymal transition (EMT) is critical not only for morphogenesis during embryonic development but also the conversion of early-stage tumors into infiltrative phenotypes. The present study examines the expression of Twist, a highly conserved bHLH transcription factor that is known to promote EMT, and evaluated its prognostic significance in endometrial cancers. Tissue specimens from 70 patients with endometrial cancer who underwent primary surgery were immunohistochemically evaluated for Twist expression. A semiquantitative scoring system was developed based on the intensity and extent of cancer cells with Twist expression. Thirty-six patients (51%) exhibited high Twist expression and 34 (49%) had low expression. Most cases exhibited both cytoplasmic and nuclear staining mainly observed in cancer foci and, preferentially, at the margin but, in some cases, the stromal cells located adjacent to cancer foci as well. Among various clinical variables, high Twist expression was significantly associated with deep myometrial invasion (>1/2) (P = .012) and concurrent with decreased E-cadherin expression (P < .001), a hallmark of EMT. In univariate survival analyses, both myometrial invasion and Twist expression influenced overall survival, but Cox multivariate analyses revealed that only Twist was an independent predictor of patient survival (hazard ratio, 5.12; P = .023). Thus, our data implies that high Twist expression is a potential novel prognostic factor for disease survival of endometrial cancer. Furthermore, the present study implicates Twist as a potential therapeutic target for this tumor type.

Adenocarcinoma↗
PubMed2006

Immunogenic variation between multiple HLA-A*0201-restricted, Hepatitis C Virus-derived epitopes for cytotoxic T lymphocytes.

CD8+ cytotoxic T lymphocytes (CTLs) play a critical role in the immune control of Hepatitis C Virus (HCV) infection. In the current study, a number of HLA-A*0201-restricted CTL epitopes derived from HCV were evaluated by examining the peptide-binding affinity for major histocompatibility complex (MHC) class I molecules, the stability of peptide-MHC complexes, killing activities of peptide-induced CTLs, and frequencies of intracellular interferon (IFN)-gamma-positive CD8+ T cells. Among 24 peptides tested, 15 peptides induced high or medium killing activities of peptide-specific CTLs. Thirteen of the 15 peptides exhibited high or medium binding affinities for HLA-A*0201 molecules, indicating that the high binding affinity for MHC class I molecules is an important factor for immunogenicity. In contrast, the stability of peptide-MHC class I complexes was not correlated with killing activities of peptide-induced CTLs. Furthermore, only a limited number of peptides could induce high or medium frequencies of IFN-gamma-producing CD8+ T cells, which were generally considered to play a crucial role for the clearance of HCV. Analyses of the immunogenicity of CTL epitopes such as in the current study should provide important information about the design of an efficient HCV vaccine that induces vigorous, sustained, and broad HCV-specific CTL responses.

Amino Acid Sequence↗
PubMed2006

Use of RNase P for efficient preparation of yeast tRNATyr transcript and its mutants.

Because T7 RNA polymerase has a strong preference for particular sequences to initiate transcription, some RNAs having pyrimidine-rich sequences at their 5'-end (yeast tRNA(Tyr), for example) are hardly transcribed by this enzyme. To circumvent this inconvenience, we have developed an efficient method for in vitro preparation of such tRNAs. The RNA of interest is first transcribed as a precursor form that has purine-rich extra sequences at its 5'-end, then processed with RNase P to generate the objective tRNAs. By using this protocol, we were able to prepare easily and efficiently yeast tRNA(Tyr) transcript and its mutants harboring base substitutions within the anticodon loop and/or acceptor stem regions. Aminoacylation analyses of these tRNA transcripts with yeast tyrosyl-tRNA synthetase revealed that the replacement of G34 by C34 (mutation to amber suppressor) severely impaired the aminoacylation, whereas the replacement of the U4:G69 wobble base-pair in the acceptor stem region by C4:G69 normal Watson-Crick type base-pair improved it.

Acylation↗
PubMed2006

Misacylation of yeast amber suppressor tRNA(Tyr) by E. coli lysyl-tRNA synthetase and its effective repression by genetic engineering of the tRNA sequence.

Through an exhaustive search for Escherichia coli aminoacyl-tRNA synthetase(s) responsible for the misacylation of yeast suppressor tRNA(Tyr), E. coli lysyl-tRNA synthetase was found to have a weak activity to aminoacylate yeast amber suppressor tRNA(Tyr) (CUA) with L-lysine. Since our protein-synthesizing system for site-specific incorporation of unnatural amino acids into proteins is based on the use of yeast suppressor tRNA(Tyr)/tyrosyl-tRNA synthetase (TyrRS) pair as the "carrier" of unusual amino acid in E. coli translation system, this misacylation must be repressed as low as possible. We have succeeded in effectively repressing the misacylation by changing several nucleotides in this tRNA by genetic engineering. This "optimized" tRNA together with our mutant TyrRS should serve as an efficient and faithful tool for site-specific incorporation of unnatural amino acids into proteins in a protein-synthesizing system in vitro or in vivo.

Amino Acyl-tRNA Synthetases↗
PubMed2006

Crystallization and preliminary X-ray crystallographic analysis of yeast tyrosyl-tRNA synthetase complexed with its cognate tRNA.

Yeast tyrosyl-tRNA synthetase (yTyrRS) has been crystallized by the vapor diffusion method in the presence of its cognate tRNA(Tyr). The crystals belong to a tetragonal space group P4(1)2(1)2 with cell dimensions of a = b = 63.85 Angstrom, and c = 330.3 Angstrom. The asymmetric unit contains one molecule each of yTyrRS and tRNA(Tyr) (one-half of a 2:2 complex). X-ray diffraction data have been collected up to 2.5 Angstrom resolution.

Crystallization↗
PubMed2006

[A case of pyothorax caused by Mycobacterium avium].

A 74-year-old woman was admitted to our hospital in December, 2003 because of anorexia and weight loss lasting from August, 2003. Chest CT scan showed empyema with a niveau in the right lung and infiltrative and nodular shadows in the left lung. Acid-fast bacilli were detected in pleural effusion. Polymerase chain reaction (PCR) test was negative for Mycobacterium tuberculosis (M. tuberculosis) but positive for Mycobacterium avium (M. avium). PCR test for M. avium was also positive in bronchial lavage fluid, and many colonies of M. avium complex ( MAC) were cultured from pleural effusion. After we administered 4 drugs including RFP, EB, SM, and CAM, cultured colonies of M. avium decreased, the inflammatory reaction improved, and infiltrates in the left upper lobe has disappeared. These improvements confirmed the diagnosis of empyema caused by M. avium. Since nontuberculous mycobacteria induced empyema has rarely been reported, the clinical features of this disease should further be examined.

Aged↗
PubMed2006

[Penicillamine-induced bronchiolitis obliterans diagnosed by transbronchial lung biopsy].

A 57-year-old woman had been treated with penicillamine (200 mg/day) for degenerative arthritis initially misdiagnosed as rheumatoid arthritis since 2003. She presented with dyspnea and was admitted to our hospital in 2004. Pulmonary function tests revealed mixed pattern of dysfunction with severe airway obstruction. Chest computed tomography showed mosaic ground-glass opacities. Bronchoalveolar lavage fluid (BALF) demonstrated increase in total cells and lymphocytes. Since specimens of transbronchial lung biopsy (TBLB) showed lymphocytic infiltration in membranous bronchiole and occlusion of the membranous bronchiole lumen, bronchiolitis obliterans was diagnosed by TBLB. After penicillamine, which had been administered for 7 months, was stopped, she was successfully treated with steroid and macrolides.

Antirheumatic Agents↗
PubMed2005

Role of cyclooxygenase-2 in immunomodulation and prognosis of endometrial carcinoma.

Although there are several hypotheses explaining the mechanisms of immune-privileged status of malignant tumor, the exact pathway has yet to be explored. Cyclooxygenase (COX)-2 plays a vital role in prognosis of cancer patients in terms of contribution to neoangiogenesis and apoptosis inhibition; however, the impact of COX-2 in immunomodulation has not been reported. We have evaluated the expression of COX-2 and its impact on infiltration of immune-competent cells into the tumor cell nest in endometrial carcinoma. Tissue specimens from 70 endometrial carcinoma patients who had undergone a curative resection were evaluated for COX-2 expression and host immune status (CD8+ T cells). COX-2 expression was associated with FIGO stage and myometrial invasion, but there was no statistically significant impact. CD8+ T cells within cancer cell nest (Nest CD8) were inversely correlated with the expression level of COX-2 (p = 0.0006). Nest CD8 became an independent predictor of patient survival (Hazard ratio = 10.300, p = 0.0304) in Cox's multivariate analysis. The expression level of COX-2 was found to be a significant predictor of disease relapse in univariate analysis (p = 0.0294) but not in multivariate analysis (p = 0.5949). In conclusion, increased nest CD8 produced a survival advantage in endometrial carcinoma patients. Moreover, tumor-produced COX-2, which reduces the infiltration of CD8+ T cells into cancer cell nests, may allow tumors to avoid immune surveillance.

Adult↗
PubMed2005

Aromatase expression in stromal cells of endometrioid endometrial cancer correlates with poor survival.

PURPOSE AND EXPERIMENTAL DESIGN: To assess the prognostic significance of intratumoral aromatase in endometrioid endometrial cancer, sections from 55 patients with endometrial cancer were evaluated for expression of aromatase using immunohistochemistry, and the correlation between aromatase expression and clinicopathologic parameters were analyzed. RESULTS: Immunohistochemical staining for aromatase was positive for 32 (58%), 20 (36%), and 19 (34%) patients in cancer epithelial cells, stromal cells, and myometrial cells around the flank invasion, respectively. In situ hybridization also detected aromatase mRNA in all three types of cells. RT-PCR analysis revealed that aromatase mRNA was 2.5 +/- 1.0 amol/mug total RNA (mean +/- SE; n = 7) in tumor tissue. Western blot analysis detected the expected aromatase protein size of 58 kDa in cancer tissues more abundantly than in cancer-free endometrium (n = 3). The immunoreactivity in stromal cells correlated positively with advanced surgical stage and poor survival. Survival analysis revealed that the immunoreactivity of stromal cells was a significant prognostic factor, independent of histologic grade, muscular invasion, and lymph node metastasis, but dependent on surgical stage. By contrast, the immunoreactivity of aromatase both in cancer epithelial cells and myometrial cells did not correlate with prognosis. CONCLUSIONS: To the best of our knowledge, this is the first evidence associating intratumoral aromatase expression in stromal cells and poor survival in endometrioid endometrial cancer. This positive linkage indicates that local expression of aromatase plays a role in tumor progression through the formation of in situ estrogens. In situ expression of aromatase may offer a potential target for management of endometrial cancers.

Aromatase↗
PubMed2005

[A clinical study of endoscopic local coagulation therapy for hepatocellular carcinoma (HCC)].

Eighteen subjects with cases of HCC who underwent endoscopic local coagulation therapy at Hiroshima City Hospital between 1998 and 2004 were studied and compared with 6 cases of HCC patients who underwent laparoscopic partial hepatectomy during the same period. The subjects composed of 10 cases of laparoscopic microwave coagulation therapy (L-MCT), 5 cases of laparoscopic radio frequency ablation therapy (L-RFA), and 3 cases of thoracoscopic microwave coagulation therapy (T-MCT). The operation time was 114 minutes for L-MCT and 92 minutes for L-RFA, both of which were significantly shorter than 208 minutes for resection cases. No complications were developed in any of the cases and the postoperative hospitalization period of the cases was 13.1 days, 8.2 days, and 13.0 days, respectively. Although each case of local recurrence was observed both in L-MCT and L-RFA groups, one case displayed observation difficulty from the liver surface and the other required a daughter nodule. The three-year survival rate was 71.4%, while the five-year survival rate was 53.6%. Endoscopic local coagulation therapy is not too invasive and useful for hepatocellular carcinoma in which percutaneous RFA is difficult. However, it is well indicated when the scope is evident with observation being feasible from the liver surface.

Carcinoma, Hepatocellular↗
PubMed2004

Effects of the traditional Japanese medicine Unkei-to on the corticotropin-releasing factor-induced increase in locomotor activity.

The effect of Unkei-to, a traditional Japanese herbal medicine and strong in vitro releaser of cytokine-induced neutrophil chemoattractant (CINC), on the increase in locomotor activity induced by intracerebroventricular (icv) injection of corticotropin-releasing factor (CRF) in male rats in a familiar environment was investigated. Oral administration of Unkei-to (100 mg/kg) for 1 week significantly attenuated the CRF-induced increase in locomotor activity. Unkei-to also reduced the CRF-induced accumulation of hypothalamic CINC, which has a functional antagonistic action on the response to CRF; the reduction may reflect an increased release of CINC. These results suggest that Unkei-to has an alleviative effect on the action induced by brain CRF and the mechanism of this effect may partly involve CINC.

Animals↗
PubMed2004

Three-dimensional structure of the ternary complex of yeast tyrosyl-tRNA synthetase.

The archaeal/eukaryotic tyrosyl tRNA synthetase (TyrRS)-tRNA(Tyr) pairs do not cross-react with their prokaryotic counterparts. Recently, crystal structure analyses of prokaryotic and archaeal TyrRSs complexed with their cognate tRNA(Tyr) have been reported, however, no structure is available for eukaryotic TyrRS complexed with its cognate tRNA(Tyr). Here we report the crystal structure of yeast Tyrosyl-tRNA synthetase (yTyrRS) complexed with its cognate tRNA(Tyr) and Tyr-AMP analog.

Crystallization↗