Biomedical subjects

G Tamura

Publications and source records attributed to G Tamura.

At least 19 recordsLinked to original sources

PubMed1998

Functionally inactivating point mutation in the tumor-suppressor IRF-1 gene identified in human gastric cancer.

Loss of heterozygosity (LOH) observed in human tumors strongly suggests the existence of (a) tumor-suppressor gene(s) at the concerned locus. A series of studies has revealed that LOH on the long arm of chromosome 5 (5q) frequently occurs in differentiated gastric adenocarcinomas. Furthermore, it has been shown that the interferon regulatory factor-1 (IRF-1) locus on chromosome 5q31.1 is one of the common minimal regions of LOH in these cancers. IRF-1 is a transcriptional activator that shows tumor-suppressor activity in the mouse. In the present study, we examined the sequence of the IRF-1 gene in 9 cases of histologically differentiated gastric adenocarcinomas, all of which exhibited LOH at the IRF-1 locus. We identified a mis-sense mutation in the residual allele in one case. This mutated form of IRF-1 showed markedly reduced transcriptional activity. In addition, overexpression of wild-type IRF-1 induced cell-cycle arrest, whereas such activity was attenuated in the mutant IRF-1. These results suggest that the loss of functional IRF-1 is critical for the development of human gastric cancers.

3T3 Cells↗

PubMed1998

Tissue-specific involvement of multiple mitochondrial DNA deletions in familial mitochondrial myopathy.

It is still uncertain how deleted mitochondrial DNA (mtDNA) is distributed to each tissue during development, although deletions of mtDNA have been extensively observed in various pathologic conditions. This paper presents two Japanese siblings with progressive external ophthalmoplegia exhibiting multiple mtDNA deletions. In one patient, similar multiple mtDNA deletions were found in skeletal muscle specimens as well as in the spinal cord but not in the myocardium, liver or leukocytes. A similar deletion pattern was found in the skeletal muscle but not in the leukocytes of the other patient. The results suggest the complex mechanism to generate, expand and eliminate the deleted mtDNA in humans.

Adult↗

PubMed1998

Loss of heterozygosity during the development and progression of differentiated adenocarcinoma of the stomach.

In a recent allelotypic analysis of differentiated adenocarcinoma of the stomach, loss of heterozygosity (LOH) was found frequently on chromosomes 2q, 4p, 5q, 6p, 11q, 14q, 17p, 18q, and 21q. To clarify the sequence of these chromosomal losses during gastric carcinogenesis, microsatellite analysis of the chromosome arms described above was performed in 25 early and 29 advanced differentiated adenocarcinomas of the stomach. LOH on these chromosome arms fell within a range of 20-50 per cent. On 4p, 7q, 14q, 17p, and 21q, LOH was detected at a similar frequency in both early and advanced carcinomas, while LOH on 2q, 5q, 6p, 11q, and 18q was observed more than twice as frequently in advanced than in early lesions. Mean fractional allelic losses (FALs) were 0.221 in early and 0.413 in advanced carcinomas, representing a significant difference P < 0.05). These results suggest that LOH on 4p, 7q, 14q, 17p, and 21q is a relatively early event, while LOH on 2q, 5q, 6p, 11q, and 18q typically accumulates during the progression of gastric carcinogenesis.

Adenocarcinoma↗

PubMed1998

Infrequent frameshift mutations of polynucleotide repeats in multiple primary cancers affecting the esophagus and other organs.

Frequent frameshift mutations of simple nucleotide repeats in the protein-encoding regions, as well as replication errors (RERs) at microsatellite loci, have recently been demonstrated in gastrointestinal tumors. These genetic instabilities have been considered indicative of an increased risk of accumulating mutations in cancer-associated genes and of developing multiple cancers. We studied frameshift (or insertion/deletion) mutations of simple nucleotide repeats in five genes (TGFbeta type II receptor [TGFbetaRII], E2F4, MSH2, MSH3, and MSH6) in 23 tumors from 12 patients who had synchronous cancers of the esophagus and other organs. Genetic instability at four microsatellite loci, as well as mutations in the TP53, APC, and KRAS2 genes, were also studied. No frameshift mutations were observed in the TGFbetaRII, MSH3, and MSH6 genes. RER and a deletion mutation of BAT26 in MSH2 were present in one (1/23; 4%) gastric cancer. This tumor also carried a deletion mutation in the serine (AGC) repeat of the E2F4 gene. Mutation screening of the TP53, APC, and KRAS2 genes revealed that the synchronous cancers did not carry the same mutations. Our results suggested that genetic instability, such as insertion/deletion mutations in simple nucleotide repeats, is not significantly associated with the development of multiple primary cancers of the esophagus and other organs, and that these synchronous cancers developed independently according to their different environmental factors.

Colonic Neoplasms↗

PubMed1998

Tylosis esophageal cancer locus on chromosome 17q25.1 is commonly deleted in sporadic human esophageal cancer.

BACKGROUND & AIMS: Tumor-suppressor genes found in inherited cancer predisposition syndromes are also responsible for sporadic cancers of the same type. Recently, the tylosis oesophageal cancer (TOC) gene locus has been mapped to 17q25 by linkage analyses of pedigrees with focal nonepidermolytic palmoplantar keratoderma associated with a high risk of esophageal cancer development. The aim of this study was to clarify whether the TOC locus is affected in sporadic esophageal cancers. METHODS: We investigated loss of heterozygosity (LOH) on 17q in 58 sporadic esophageal squamous cell carcinomas (ESCs) using 20 microsatellite markers focusing on the TOC locus. RESULTS: LOH on 17q was observed in 37 of 52 (71%) informative cases at one or more loci, 80% (33/37) of which included the TOC locus. The smallest common deleted region was at D17S1839 within the TOC locus. CONCLUSIONS: The constructed deletion map revealed that the TOC locus is commonly deleted in sporadic ESCs, suggesting that a tumor-suppressor gene responsible for ESC is contained within this locus.

Carcinoma, Squamous Cell↗

PubMed1998

Tazanolast inhibits ozone-induced airway hyperresponsiveness in guinea pigs.

We studied the inhibitory effect of tazanolast, a selective mast-cell-stabilizing drug, on ozone-induced airway hyperresponsiveness in guinea pigs. Airway responsiveness to methacholine peaked at 2 h after ozone exposure (2.0 ppm for 2 h) and the number of neutrophils in bronchoalveolar lavage (BAL) fluid continued to increase until 6 h. Tazanolast administered before ozone exposure at doses of 30, 100, or 300 mg/kg inhibited ozone-induced airway hyperresponsiveness in a dose-dependent manner. However, tazanolast administered after ozone exposure did not inhibit the airway hyperresponsiveness. Tazanolast did not significantly change the cell distribution of BAL cells at 2 h after the exposure. We conclude that tazanolast significantly inhibits ozone-induced airway hyperresponsiveness in guinea pigs. This result suggests that mast cells may play an important role in its development.

Airway Resistance↗

PubMed1998

Mutations in the human homologue of the Drosophila patched gene in esophageal squamous cell carcinoma.

The human homologue (PTCH) of the Drosophila segment polarity gene patched has recently been identified as a tumor-suppressor gene for nevoid basal cell carcinoma syndrome and for sporadic basal cell carcinomas of the skin. We analyzed 30 esophageal squamous cell carcinomas (ESCC) for intrageneic mutations of the PTCH gene by polymerase chain reaction-single-strand conformation polymorphism analysis followed by DNA sequencing. We identified two somatic PTCH mutations (7%) in 30 ESCC. These were a nonsense mutation (CAG to TAG at codon 361) in exon 8 and a missense mutation (CAG to CTG, Gln to Leu at codon 816) in exon 14. These tumors exhibited loss of heterozygosity at the polymorphic site of the PTCH gene. These results indicate that inactivation of the PTCH gene via a two-hit mechanism occurs in a subset of ESCC.

Amino Acid Substitution↗

PubMed1998

[Antigen-induced airway hyperresponsiveness in infantile guinea pigs].

To investigate the development of airway hyperresponsiveness in infantile guinea pigs, animals (10 days old) were immunized twice and challenged by inhalation of 1% ovalbumin for 10 min with 7 days intervals. Similar to adult guinea pigs, infantile ones developed an increased airway responsiveness to acetylcholine 24 hr after antigen challenge. There was a marked increase in the number of total leukocytes, eosinophils and lymphocytes in bronchoalveolar lavage fluid (BALF). Suplatast tosilate (suplatast) and pemirolast potassium (pemirolast) given orally throughout the experiments suppressed the development of airway hyperresponsiveness in infantile animals. They showed similar potency in the suppression of eosinophil accumulation in BALF and lung tissue, while suplatast inhibited lymphocyte accumulation stronger than pemirolast. Collectively, the present model of airway hyperresponsiveness in infantile guinea pigs may be useful in predicting the efficacy of antiallergic agents in the treatment of asthmatic children.

Animals↗

PubMed1997

TGF-beta induced by oral tolerance ameliorates experimental tracheal eosinophilia.

Induction of peripheral tolerance is one of the feasible approaches for the control of autoimmunities and allergies. Therapeutic applications of oral tolerance to autoimmunities are in progress both experimentally and clinically, while those to allergies have been poorly investigated. We examined the induction of CD4+ T cells with suppressive properties by oral tolerance and the mechanism by which these cells down-regulated Ag-induced eosinophilia in the trachea. Feeding of mice transgenic for anti-OVA TCR with high doses of OVA inhibited the airway eosinophilic inflammation induced by the intratracheally administered Ag. This inhibition reflected the mechanism of active suppression, since the inhibitory effect was adoptively transferred by splenic CD4+ T cells from the transgenic mice fed with high doses of OVA. The Ag specificity of the suppressor T cells was documented by the failure of spleen cells from mice that were orally tolerant of OVA to suppress irrelevant Ag, KLH-specific airway eosinophilic inflammation. The suppressive effect of the transferred T cells on eosinophil recruitment was neutralized by anti-TGF-beta mAb, but not anti-IFN-gamma mAb, indicating that the suppression is due to the inhibitory effect by secreted TGF-beta, but not to the dominance of the transferred Th1 cells over Th2 cells. This is the first study to reveal a link between oral tolerance and the regulation of Th2-mediated experimental tracheal eosinophilia through TGF-beta. Our experimental model suggests possible therapeutic applications of oral tolerance for the treatment of allergic disorders such as bronchial asthma.

Adoptive Transfer↗

PubMed1997

Inducible nitric oxide synthase and tumor necrosis factor-alpha in myocardium in human dilated cardiomyopathy.

OBJECTIVES: We examined the mRNA expression and protein localization of inducible nitric oxide synthase (iNOS) and tumor necrosis factor-alpha (TNF-alpha) in myocardial tissue obtained from patients with dilated cardiomyopathy (DCM). BACKGROUND: The etiology of DCM is unknown, but viral infection or autoimmune abnormalities that induce cytokine expression have been proposed as pathogenetic factors. Nitric oxide (NO), synthesized by nitric oxide synthase (NOS), has negative inotropic and cytotoxic effects on cardiomyocytes. Cytokines such as TNF-alpha are potent stimulators of iNOS expression. Expression of iNOS leads to excessive production of NO in the myocardium and may modulate cardiac contractility and ventricular morphology. METHODS: We examined the mRNA expression and protein localization of iNOS and TNF-alpha in myocardial tissue obtained from 24 patients with DCM, 20 patients with hypertrophic cardiomyopathy (HCM) and 15 control subjects, using the reverse transcriptase-polymerase chain reaction method and immunohistochemical studies. We then compared the differences in clinical characteristics between DCM patient subgroups with and without myocardial iNOS expression. RESULTS: Messenger RNA expression of iNOS and TNF-alpha was observed, respectively, in 13 (54%) and 18 (75%) patients with DCM. Gene expression of TNF-alpha was consistently detected in endomyocardial tissue from patients with DCM and INOS expression. Inducible NOS protein was evident only in cardiomyocytes, whereas TNF-alpha was apparent in both cardiomyocytes and endomyocardial endothelium. Neither mRNA expression nor protein localization of iNOS or TNF-alpha was observed in cardiac tissue obtained from patients with HCM or control subjects. Patients with DCM and iNOS mRNA showed a lower left ventricular ejection fraction (p < 0.01) and a higher left ventricular volume (p < 0.05) than the negative DCM group. CONCLUSIONS: Inducible NOS was consistently coexpressed with TNF-alpha in myocardial tissue obtained from a subgroup of patients with DCM and advanced left ventricular dysfunction.

Adult↗

PubMed1997

Esophageal carcinosarcoma: a genetic analysis.

Carcinosarcoma of the esophagus is a rare malignant neoplasm that consists of both carcinomatous and sarcomatous elements. The histogenesis of the sarcomatous component is generally considered to result from metaplasia of carcinomatous cells toward mesenchymal differentiation. True carcinosarcoma, characterized as a collision between a carcinoma and a sarcoma, is extremely rare. We describe a patient with primary achalasia who developed a true carcinosarcoma of the esophagus in which clonal differences between carcinomatous and sarcomatous elements were genetically and immunohistochemically demonstrated. A polypoid tumor located in the middle third of the esophagus developed in a 51-year-old man with longstanding achalasia. The tumor was predominantly composed of spindle-shaped sarcomatous cells. Squamous cell carcinoma in situ and islands of well-differentiated squamous cell carcinoma in the sarcomatous element were histologically observed. The sarcomatous element was immunoreactive for both mesenchymal and myoid markers. The carcinomatous component expressed type I and type II cytokeratins as well as epithelial membrane antigen. Analysis for chromosomal loss of heterozygosity performed in multiple microdissected samples of each sarcomatous and carcinomatous element revealed distinct genetic clonalities. These differences in immunohistochemical and genetic clonalities suggest that the tumor composed of squamous cell carcinoma and leiomyosarcoma originated separately from epithelial and mesenchymal precursors.

Carcinosarcoma↗

PubMed1997

Metachronous development of malignant Leydig cell tumor.

Leydig cell tumor (LCT), a rare testicular tumor, is malignant in only about 10% of the cases. We report the case of a patient with bilateral malignant LCTs that developed metachronously. After undergoing a right inguinal orchiectomy for a malignant LCT at the age of 43 years, the patient was given cisplatin-based chemotherapy for suspected para-aortic lymph node metastasis. Eighteen months after the right orchiectomy, examination of a left testicular biopsy specimen showed a malignant LCT and a left inguinal orchiectomy was performed. Histologically, the initial malignant LCT exhibited a highly pleomorphic appearance with mitotic figures (58/10 HPF), whereas the second malignant LCT showed fewer mitoses (2/10 HPF). The proliferating cell nuclear antigen (PCNA)-labelling index in these tumors also differed (right-sided tumor, 50%; left-sided tumor, 28%). These findings suggest that the malignant LCT in the left testis developed as a second primary rather than as a metastatic tumor. There have been no known similar cases, although three cases of malignant LCT with contralateral metastasis have been reported.

Adult↗

PubMed1997

Commonly deleted region on the long arm of chromosome 7 in differentiated adenocarcinoma of the stomach.

Loss of heterozygosity (LOH) at several chromosomal loci is a common event in human malignancies. Frequent LOH on the long arm of chromosome 7 has been reported in various human malignancies, and investigators have identified the most common site of LOH as 7q31.1. We have identified ten chromosomal loci, including chromosome 7q, that have been shown by previous allelotype study to be sites of frequent LOH in differentiated adenocarcinoma of the stomach. In the present study, we performed a polymerase chain reaction (PCR) microsatellite analysis to define the common deleted region on 7q, using 14 polymorphic microsatellite markers in matched tumour and non-tumour DNAs from 53 patients with primary gastric carcinoma of the differentiated type. LOH at any locus on 7q occurred in 34% (18 out of 53) of the tumours. Although many tumours exhibited total or large interstitial deletions, we determined the smallest common deleted region to be at D7S480 (7q31.1). This is identical to the region identified for other human malignancies. These observations indicate that a putative tumour suppressor gene at 7q31.1 may be involved in the pathogenesis of differentiated adenocarcinoma of the stomach.

Adenocarcinoma↗

PubMed1997

Analysis of the DPC4 gene in gastric carcinoma.

Allelic loss on chromosome 18q is involved in the progression of gastric carcinoma. Recently, DPC4 (deleted in pancreatic carcinoma, locus 4), a candidate tumor suppressor gene, has been localized at 18q21.1. This gene is inactivated in nearly one half of pancreatic carcinomas. We tested for DPC4 gene mutations and allelic status at 18q21 in 30 primary gastric carcinomas and 5 gastric carcinoma cell lines. Polymerase chain reaction single-strand conformation polymorphism and sequencing analyses revealed no DPC4 mutations in any of the primary tumors or cell lines. Homozygous deletion of DPC4 was observed in only 1 (MKN-45) of the 5 (20%) cell lines. This suggests that the target gene for loss on 18q is not DPC4. The true tumor suppressor gene, encoded near DPC4, has yet to be identified.

Chromosome Deletion↗

PubMed1997

MAD-related genes on 18q21.1, Smad2 and Smad4, are altered infrequently in esophageal squamous cell carcinoma.

The MAD (mothers against decapentaplegic)-related genes, Smad2 (former name MADR2 or JV18-1) and Smad4 (former name DPC4), have been identified on chromosome 18q21.1. We analyzed 30 primary esophageal squamous cell carcinomas (ESCC) and 7 cell lines derived from ESCC for intragenic mutations and loss of heterozygosity (LOH) of the Smad2 and Smad4 genes. LOH was detected in 5 of 14 (35%) informative cases. However, no mutations in either gene were detected in either the primary carcinomas or the cell lines, and only a G-to-A base transition within the 3'-untranslated region of the Smad4 gene was observed in a carcinoma. There were no homozygous deletions in either of the genes in the cell lines. MAD-related genes on chromosome 18q21.1 are altered infrequently in ESCC.

Carcinoma, Squamous Cell↗

PubMed1997

Patch-clamp characterization of secretory process in human basophils.

The effects of the intracellular Ca2+ concentration ([Ca2+]i) and a nonhydrolyzable guanosine triphosphate, guanosine 5'-o-(3-thiotriphosphate) (GTP-gamma-S), on secretion were studied by a patch-clamp technique in human basophils. When 10 microM Ca2+ were applied intracellularly, the granules dispersed rapidly, moved vigorously and fused to the cell membrane in 5 min. When the cells were exposed to 2 microM [Ca2+]i and 100 microM GTP-gamma-S, the granules dispersed gradually and granule fusion continued for 7-10 min. The plasma membrane conductance did not appreciably change with either 10 microM [Ca2+]i alone or 2 microM [Ca2+]i + 100 microM GTP-gamma-S. Intracellular application of Ca2+, 1-10 microM, caused a dose-dependent increase in cell membrane capacitance, which reflects granule membrane fusion, indicating exocytosis in a Ca2+ concentration-dependent manner. The addition of 100 microM GTP-gamma-S promoted an increase in the plasma membrane capacitance at concentrations from 0.1 to 2 microM [Ca2+]i and at 2 microM [Ca2+]i the increase was 4.4 times greater than that with 2 microM [Ca2+]i alone. These results indicate that certain G protein(s) promote Ca2+-dependent exocytosis in human basophils.

Basophils↗

PubMed1997

CD44 expression on blood eosinophils is a novel marker of bronchial asthma.

Bronchial asthma is characterized by infiltration of the respiratory tracts by eosinophils. A wide variety of adhesion molecules expressed by eosinophils have been proposed to be involved in binding of eosinophils to the vascular endothelium and subsequent transmigration from the circulation to the airways, while little is known about CD44 expression on eosinophils. We introduced a novel staining combination with which surface markers on eosinophils could be analyzed without purification prior to staining, and examined the expression of CD44 on eosinophils. Staining of eosinophils with anti-CD 16 and anti-VLA-4 mAbs enabled us to delineate eosinophils as VLA-4high CD 16- cells from any other leukocyte populations in the whole blood. CD44 was found to be constitutively expressed on resting eosinophils, and expression increased upon cytokine-mediated activation. In all bronchial asthma patients examined, CD44high eosinophils were enriched in sputum relative to peripheral blood, indicating that eosinophils in sputum were more activated than those in blood. By comparing the extent of CD44 expression on blood eosinophils from poorly controlled and well-controlled asthma patients, we unexpectedly found that the density of CD44 expression is higher on blood eosinophils from the well-controlled group. Thus, the extent of CD44 expression on blood eosinophils is a novel marker indicative of the mangement of bronchial asthma. Deterioration of the asthma management with a concomitant decrease in CD44 expression on peripheral eosinophils implies that CD44 may play an important role in facilitating the transmigration of activated, CD44high eosinophils from the circulation to the respiratory tracts.

Asthma↗

PubMed1997

Eosinophils as a source of matrix metalloproteinase-9 in asthmatic airway inflammation.

Bronchial asthma is characterized by eosinophil infiltration and tissue remodeling. Matrix metalloproteinases (MMPs) are thought to play critical roles by degradating interstitial matrices in a wide range of lung diseases associated with reorganization of the airway architecture. To investigate whether MMPs are involved in the pathologic processes of bronchial asthma, we examined MMP expression in asthmatic subjects. In situ hybridization revealed abundant expression of MMP-9 (gelatinase B) mRNA in biopsy specimens from asthmatic subjects (n = 5), with an average positive cell distribution of 117.8 +/- 41.1 (mean +/- SEM)/mm2. In contrast, sparse expression of the mRNA (10.8 +/- 4.8 /mm2) was observed in specimens from normal subjects (n = 4). The vast majority of cells expressing the mRNA were eosinophils in asthmatic tissues (92.2 +/- 1.2%). MMP-9 protein, which was confined to the submucosal cells in the normal subjects, was not abundantly expressed in inflammatory cells, but there was positive reactivity for MMP-9 protein in the extracellular matrix. Immunoelectron microscopic analysis showed sparse immunolocalization of MMP-9 in the perinuclear spaces of eosinophils, but not in the granules. These findings suggest the overexpression of MMP-9 by eosinophils in bronchial tissues of asthmatic individuals, and the participation of MMPs in the pathologic changes in asthmatic airways.

Adult↗