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S Shirasawa

Publications and source records attributed to S Shirasawa.

At least 19 recordsLinked to original sources
PubMed2006

STAT1-independent inhibition of cyclooxygenase-2 expression by IFNgamma; a common pathway of IFNgamma-mediated gene repression but not gene activation.

Cyclooxygenase-2 (COX-2), the rate-limiting enzyme in the synthesis of prostaglandins, promotes the development of colorectal cancer, and is a key molecular target of non-steroidal anti-inflammatory drugs, compounds that reduce the relative risk of developing colon cancer. In this study, we showed that interferon gamma (IFNgamma) inhibits the expression of COX-2 protein in intestinal epithelial cells (IECs) through a pathway that requires Janus-activated kinase (JAK) activity. In contrast, we demonstrated that transcriptional inhibition of COX-2 by IFNbeta or IFNgamma occurs in cells with silenced signal transducer and activator of transcription 1 (STAT1) expression and that IFNs retained the ability to inhibit COX-2 transcription in cells with activated RasV12, in which IFNgamma failed to induce STAT1. Thus, unlike the activity of JAK, STAT1 is not required for the inhibition of COX-2 expression by IFNgamma. In contrast to COX-2, the activation of genes in response to IFNgamma, such as interferon regulatory factor-1, was severely impaired by both STAT1 silencing and by constitutive Ras signaling. To determine whether there is a general differential requirement for STAT1 in gene activation and gene repression in response to IFNgamma in intestinal cells, we performed genome-wide analysis of IFNgamma target genes in an IEC line in which STAT1 expression was silenced by small interfering RNA. The results confirmed that the activation of the majority of genes by IFNgamma required STAT1. In contrast, the repression of several genes, as we showed for COX-2 specifically, was largely unaffected in cells with silenced STAT1. Our results therefore demonstrate that in general gene activation by IFNgamma is more sensitive to STAT1 deficiency than gene repression, and suggest that IFNgamma activates and represses gene expression via distinct pathways that can be distinguished, at least in part, by their requirement for STAT1.

Cells, Cultured↗
PubMed2006

Detachment-induced upregulation of XIAP and cIAP2 delays anoikis of intestinal epithelial cells.

Detachment of normal epithelial cells from the extracellular matrix triggers apoptosis, a phenomenon called anoikis. Conversely, carcinoma cells tend to be relatively more anoikis-resistant than their normal counterparts, and this increased resistance represents a critical feature of the malignant phenotype. Mechanisms that control susceptibility and resistance to anoikis are not fully understood. It is now known that detachment of non-malignant epithelial cells triggers both pro- and antiapoptotic signals, and it is the balance between these signals and the duration of detachment that determine further fate of the cells. Detachment-induced antiapoptotic events delay anoikis and if cells reattach relatively soon after detachment they survive. Direct regulators of apoptosis responsible for this delay of anoikis are unknown. We found that detachment of non-malignant intestinal epithelial cells triggers upregulation of inhibitors of apoptosis protein (IAP) family, such as X-chromosome-linked inhibitor of apoptosis protein and cellular inhibitor of apoptosis-2 (cIAP2). We demonstrated that this upregulation requires detachment-dependent activation of the transcription factor nuclear factor-kappaB. We further observed that various IAP antagonists accelerate anoikis, indicating that upregulation of the IAPs delays detachment-triggered apoptosis. We conclude that the IAPs are important regulators of the balance between detachment-triggered life and death signals. Perhaps, not by coincidence, these proteins are often upregulated in carcinomas, tumors composed of cells that tend to be anoikis-resistant.

Anoikis↗
PubMed2004

Assessment of synthetic peptides of severe acute respiratory syndrome coronavirus recognized by long-lasting immunity.

In order to determine highly immunogenic severe acute respiratory syndrome coronavirus (SARS-CoV) epitope peptides capable of inducing long-lasting immunity, we first screened immunoglobulin-G (IgG) antibodies reactive to 197 different overlapping 15-mers from the SARS-CoV proteins in the sera of three infected patients. Forty-two peptides among them were reactive to the sera from all three patients. Consequently, we tested for the reactivity of these 42 peptides to patients' sera (n = 45) at 6-month post-infection. The significantly higher levels of IgG antibodies specific to three (S791, M207 and N161) of 42 peptides were detectable in the post-infection sera from 23 (51%), 27 (60%) and 19 (42%) of 45 patients, respectively. These three peptides, recognized by their long-lasting immunity, may provide a better understanding of the immunogenicity of SARS-CoV.

Enzyme-Linked Immunosorbent Assay↗
PubMed2001

Formation of brainstem (nor)adrenergic centers and first-order relay visceral sensory neurons is dependent on homeodomain protein Rnx/Tlx3.

Brainstem visceral sensory and (nor)adrenergic neurons play crucial roles in modulating cardiovascular and respiratory functions. The origins and formation of these neurons are poorly understood. Here we show that these two classes of neurons are derived from Mash1-positive precursor cells, and can be prospectively identified by combinatorial expression of two homeobox genes, Rnx and Phox2 (Phox2a or Phox2b). It was previously shown that Rnx-deficient mice die from respiratory failure. Here we show that Rnx function is required for formation of first-order relay visceral sensory neurons in the brainstem. In addition, as in Phox2b-deficient mice, the development of most (nor)adrenergic centers is compromised in Rnx mutants. We also provide genetic evidence to show that Rnx and Phox2 proteins may function independently to specify the (nor)adrenergic phenotype. Our studies reveal a surprising ontogenetic relationship between relay visceral sensory and (nor)adrenergic neurons, and suggest that it may be a common theme in the developing nervous system that the same set of transcriptional regulators is associated with formation of multiple components within a neuronal network.

Animals↗
PubMed2001

Identification of susceptibility loci for autoimmune thyroid disease to 5q31-q33 and Hashimoto's thyroiditis to 8q23-q24 by multipoint affected sib-pair linkage analysis in Japanese.

Autoimmune thyroid disease (AITD), including Graves' disease (GD) and Hashimoto's thyroiditis (HT), is caused by multiple genetic and environmental factors. The clinical and immunological features of GD and HT are distinct; however, there are multiplex families with both GD and HT, and cases in which GD evolves into HT. Thus, there may be specific susceptibility loci for GD or HT, and common loci controlling the susceptibility to both GD and HT may exist. A genome-wide analysis of data on 123 Japanese sib-pairs affected with AITD was made in which GD- or HT-affected sib-pairs (ASPs) were studied to detect GD- or HT-specific susceptibility loci, and all AITD-ASPs were used to detect AITD-common susceptibility loci. Our study revealed 19 regions on 14 chromosomes (1, 2, 3, 5, 6, 8, 9, 10, 11, 12, 13, 15, 18 and 22) where the multipoint maximum LOD score (MLS) was >1. Especially, chromosome 5q31-q33 yielded suggestive evidence for linkage to AITD as a whole, with an MLS of 3.14 at D5S436, and chromosome 8q23-q24 yielded suggestive evidence for linkage to HT, with an MLS of 3.77 at D8S272. These observations suggest the presence of an AITD susceptibility locus at 5q31-q33 and a HT susceptibility locus at 8q23-q24.

Abatacept↗
PubMed2001

[A case of giant dumbbell shaped schwannoma with massive pleural effusion].

A 58-year-old female was admitted to the hospital complaining of dyspnea. The chest roentgenogram and CT scan revealed a large mediastinum tumor and massive pleural effusion in the right hemithorax. The diagnosis of lung cancer with carcinomatous pleulitis was performed through thoracocentesis an treatment of chemotherapy was chosen. After 6 years, she was admitted again to the hospital complaining of dull pain in the right leg. Chest CT scan and MRI showed a giant dumbbell shaped mass connected to the spinal canal. The tumor was larger than that of six years ago and diagnosed as schwannoma by CT-guided pericutaneous needle biopsy. At operation, hemilaminectomy of Th 1-3 was done first, and total tumor resection was performed through posterolateral thoracotomy. Intrathoracic adhesion was severe and it was difficult to control air leakage from the lung, thoracoplasty was performed.

Female↗
PubMed2000

Involvement of deregulated epiregulin expression in tumorigenesis in vivo through activated Ki-Ras signaling pathway in human colon cancer cells.

To identify the genes located downstream of the activated Ki-Ras signaling pathways in human colon cancer cells, a PCR-based cDNA subtraction library was constructed between HCT116 cells and HCT116-derived activated Ki-ras-disrupted cells (HKe3). One of the genes in HCT116 that was evidently up-regulated was epiregulin, a member of the epidermal growth factor family that is expressed in many kinds of human cancer cells. HKe3-stable transfectants expressing activated Ki-Ras regained over-expression of epiregulin. To further elucidate the biochemical structure and significance of epiregulin expression in tumorigenesis, HKe3-stable transfectants expressing epiregulin (e3-pSE cells) were established. Epiregulin existed as highly glycosylated membrane-bound forms, and TPA rapidly induced ectodomain shedding of epiregulin. Furthermore, the conditioned medium of e3-pSE cells showed more DNA synthesis for 32D cells expressing epidermal growth factor receptor (DER) cells than that of HKe3. Although anchorage-independent growth in soft agar was not observed for e3-pSE cells, tumorigenicity in nude mice was observed evidently, and their growth rate was correlated with each amount of exogenous epiregulin expression. These results suggested that activated Ki-Ras will be one of the factors contributing to the overexpression of epiregulin in human colon cancer cells, and that epiregulin will play a critical role in human tumorigenesis in vivo.

Animals↗
PubMed2000

Opposing effects of Ras on p53: transcriptional activation of mdm2 and induction of p19ARF.

Mdm2 acts as a major regulator of the tumor suppressor p53 by targeting its destruction. Here, we show that the mdm2 gene is also regulated by the Ras-driven Raf/MEK/MAP kinase pathway, in a p53-independent manner. Mdm2 induced by activated Raf degrades p53 in the absence of the Mdm2 inhibitor p19ARF. This regulatory pathway accounts for the observation that cells transformed by oncogenic Ras are more resistant to p53-dependent apoptosis following exposure to DNA damage. Activation of the Ras-induced Raf/MEK/MAP kinase may therefore play a key role in suppressing p53 during tumor development and treatment. In primary cells, Raf also activates the Mdm2 inhibitor p19ARF. Levels of p53 are therefore determined by opposing effects of Raf-induced p19ARF and Mdm2.

Animals↗
PubMed2000

Rnx deficiency results in congenital central hypoventilation.

The genes Tlx1 (Hox11), Enx (Hox11L2, Tlx-2) and Rnx (Hox11L2, Tlx-3) constitute a family of orphan homeobox genes. In situ hybridization has revealed considerable overlap in their expression within the nervous system, but Rnx is singularly expressed in the developing dorsal and ventral region of the medulla oblongata. Tlx1-deficient and Enx-deficient mice display phenotypes in tissues where the mutated gene is singularly expressed, resulting in asplenogenesis and hyperganglionic megacolon, respectively. To determine the developmental role of Rnx, we disrupted the locus in mouse embryonic stem (ES) cells. Rnx deficient mice developed to term, but all died within 24 hours after birth from a central respiratory failure. The electromyographic activity of intercostal muscles coupled with the C4 ventral root activity assessed in a medulla-spinal cord preparation revealed a high respiratory rate with short inspiratory duration and frequent apnea. Furthermore, a coordinate pattern existed between the abnormal activity of inspiratory neurons in the ventrolateral medulla and C4 motorneuron output, indicating a central respiratory defect in Rnx mice. Thus, Rnx is critical for the development of the ventral medullary respiratory centre and its deficiency results in a syndrome resembling congenital central hypoventilation.

Abnormalities, Multiple↗
PubMed2000

[Effects of impression of faces on recognition of changes in face arrays: addition versus deletion].

A study was conducted examine whether the asymmetric confusability effect was generalized to an array of face photographs, and furthermore to investigate how the impression of faces affected the recognition of addition and deletion of the faces. In a preliminary investigation, 27 subjects rated the impression of 83 face photographs, and the photographs to be used in the present study were chosen on the basis of the impression scores. In the study, 40 subjects saw 14 photographs consisted of three or four faces and took a recognition test of unchanged photographs and changed photographs with a specific face added or deleted. The data showed that (a) the addition superiority was not found in the recognition of changes in face arrays; (b) the impression of faces differentially affected the recognition of addition and deletion changes in face arrays. These results suggest that the mechanism underlying the recognition of the deletion of a face may be different from that of addition.

Adult↗
PubMed1999

Activated Ki-Ras suppresses 12-O-tetradecanoylphorbol-13-acetate-induced activation of the c-Jun NH2-terminal kinase pathway in human colon cancer cells.

Although the frequency of activated Ki-ras genes is high in human colorectal tumors, much less is known of activated Ki-ras-mediated signaling pathways. Using gene targeting, we examined HCT116 cells that contain the Gly-13-->Asp mutation of Ki-ras and activated Ki-ras-disrupted clones derived from HCT116. 12-O-Tetradecanoylphorbol-13-acetate (TPA) induced immediate early genes, such as c-Jun, c-Fos, and Egr-1 in activated Ki-ras-disrupted clones, whereas c-Jun induction was rare in HCT116. TPA induced both phosphorylation of stress-activated protein kinase kinase 1 (SEK1) and c-Jun NH2-terminal kinase (JNK) in the activated Ki-ras-disrupted clones but not in HCT116. On the other hand, TPA-induced mitogen-activated protein kinase kinase 1/2 (MEK1/2)-extracellular signal-regulated kinase (ERK) activation was equally induced between HCT116 and the Ki-ras-disrupted clones. Furthermore, TPA-induced SEK1-JNK activation was observed in a DLD-1-derived activated Ki-ras-disrupted clone but not in DLD-1. The TPA-induced SEK1-JNK activation in these disrupted clones was completely inhibited by the protein kinase C (PKC) inhibitor, GF109203X (1 microM), but not by another PKC inhibitor, H7 (50 microM), whereas TPA-induced MEK1/2-ERK activation was partially and completely inhibited by GF109203X (1 microM) and H7 (50 microM), respectively. A phosphoinositol 3-kinase inhibitor, LY294002, did not inhibit the TPA-induced SEK1-JNK activation. Taken together, these results suggest that activated Ki-Ras-mediated signals are involved in the SEK1-JNK pathway through a PKC isotype that is distinct from that involved in MEK1/2-ERK activation in human colon cancer cells and independent of phosphoinositol 3-kinase activation, and the imbalance between ERK and JNK activity caused by activated Ki-Ras may play critical roles in human colorectal tumorigenesis.

Alleles↗
PubMed1999

Targeted disruption of the K-ras oncogene in an invasive colon cancer cell line down-regulates urokinase receptor expression and plasminogen-dependent proteolysis.

The urokinase receptor, overexpressed in invasive colon cancer, promotes tumour cell invasion. Since K-Ras is activated in many colon cancers, we determined if urokinase receptor overexpression is a consequence of this activated oncogene. Accordingly, urokinase receptor expression was compared in HCT 116 colon cancer cells containing either a mutation-activated K-Ras or disrupted for this oncogene (by homologous recombination). HCT 116 cells containing the disrupted K-Ras oncogene expressed between 50 and 85% less urokinase receptor protein compared with the parental HCT 116 cells. Reduced urokinase receptor expression in cells containing the disrupted mutated K-Ras was not due to a physical impairment of the urokinase receptor gene since phorbol ester treatment was inductive for its expression. Constitutive urokinase receptor expression in HCT 116 cells required an intact AP-1 motif in the promoter (at -184) and electrophoretic mobility shifting assays indicated less c-Jun, JunD, c-Fos and Fra-1 bound to this motif in the K-Ras-disrupted cells. Since the urokinase receptor accelerates proteolysis, laminin degradation was compared in cells containing the mutation-activated and disrupted K-Ras oncogene. The latter cells displaying fewer urokinase receptors, degraded 80% less laminin. This is the first study to demonstrate a role for K-Ras as a regulator of the constitutive expression of the urokinase receptor.

Cell Nucleus↗
PubMed1998

Impact of oncogenes in tumor angiogenesis: mutant K-ras up-regulation of vascular endothelial growth factor/vascular permeability factor is necessary, but not sufficient for tumorigenicity of human colorectal carcinoma cells.

Targeted disruption of the single mutant K-ras allele in two human colorectal carcinoma cell lines (DLD-1 and HCT-116) leads to loss of tumorigenic competence in nude mice with retention of ability to grow indefinitely in monolayer culture. Because expression of the mutant K-ras oncogene in these cell lines is associated with marked up-regulation of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF), we sought to determine whether this potent angiogenesis inducer plays a role in K-ras-dependent tumorigenic competence. Transfection of a VEGF121 antisense expression vector into DLD-1 and HCT-116 cells resulted in suppression of VEGF/VPF production by a factor of 3- to 4-fold. The VEGF/VPF-deficient sublines, unlike the parental population or vector controls, were profoundly suppressed in their ability to form tumors in nude mice for as long as 6 months after cell injection. In contrast, in vitro growth of these sublines was unaffected, thus demonstrating the critical importance of VEGF/VPF as an angiogenic factor for HCT-116 and DLD-1 cells. Transfection of a full-length VEGF121 cDNA into two nontumorigenic mutant K-ras knockout sublines resulted in a weak but detectable restoration of tumorigenic ability in vivo in a subset of the transfectants, with no consistent change in growth properties in vitro. The findings indicate that mutant ras-oncogene-dependent VEGF/VPF expression is necessary, but not sufficient, for progressive tumor growth in vivo and highlight the relative contribution of oncogenes, such as mutant K-ras, to the process of tumor angiogenesis.

Animals↗
PubMed1998

MHC class I bound peptides of a colon carcinoma cell line, a Ki-ras gene-targeted progeny cell line and a B cell line.

MHC class I associated peptides on cancer cells represent potential targets for CD8+ cytotoxic T cell activity against tumor cells. We eluted the naturally bound MHC class I peptides of a colon carcinoma cell line and compared them to peptides isolated from a B cell line and a slow-growing activated Ki-ras-disrupted colon cancer cell line. While we failed to detect any significant differences in class I associated peptides due to the presence or absence of activated Ki-ras in colon cancer cell lines, the colon cancer cell lines and B cell line presented vastly different peptide repertoires in the context of HLA-A*0201 molecules.

B-Lymphocytes↗
PubMed1997

Activated Ki-ras enhances sensitivity of ceramide-induced apoptosis without c-Jun NH2-terminal kinase/stress-activated protein kinase or extracellular signal-regulated kinase activation in human colon cancer cells.

The activation of c-Jun NH2-terminal kinase (JNK)/stress-activated protein kinase (SAPK) and/or extracellular signal-regulated kinase (ERK) is involved in ceramide-induced apoptosis in certain cells. To examine the relationship between activated Ki-ras-mediated signals and ceramide-induced apoptosis in human colon cancer cells, JNK/SAPK and ERK activity, as initiated by ceramide, was examined in HCT116, which has a mutation of Ki-ras at codon 13, and HCT116-derived clones, HKe-3 and HKh-2, in which activated Ki-ras was disrupted through gene targeting. In HKe-3 and HKh-2, the activity of JNK/SAPK increased significantly within 60 min following C2 ceramide stimulation, and some apoptosis followed. In contrast, C2 ceramide caused a marked apoptosis in HCT116, but activation of JNK/SAPK was not observed. C2 ceramide did not activate ERK in any of the cell lines. These results suggest that activated Ki-ras contributes to the sensitivity of ceramide-induced apoptosis without JNK/SAPK or ERK activation and that other signaling pathways involved in ceramide-induced apoptosis may be present in human colon cancer cells.

Apoptosis↗
PubMed1997

Suppression of serum-induced c-jun expression by activated Ki-ras in human colon cancer cells.

Through gene-targeting, we have established human colon cancer cell lines, HK2-6 and HKe-3, with and without activated Ki-ras, respectively, derived from a human colon cancer cell line HCT116, and we have reported that activated Ki-ras is involved in the deregulation of c-myc expression. To further examine the relation between Ki-ras-mediated signals and other immediate early genes, c-jun was analyzed on these cells stimulated by serum. Rapid and strong induction of c-jun was observed in HKe-3, but not in HCT116 or HK2-6. To elucidate the regulatory mechanisms of c-jun expression by Ki-ras, protein kinase C (PKC) and c-Raf were examined at serum-starved and serum-stimulated conditions. Phosphorylations of c-Raf were same among these cells, however, the cytosolic PKC activity in HKe-3 was two times higher than that in HCT116 on serum-starved and serum-stimulated conditions. These results suggested that serum responsiveness of c-jun may be suppressed by activated Ki-ras through PKC rather than c-Raf pathway in colon cancer cells.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1997

Enx (Hox11L1)-deficient mice develop myenteric neuronal hyperplasia and megacolon.

The isolated homeobox gene Enx (Hox11L1) is expressed in enteric neurons innervating distal ileum, and proximal and distal colon. Enx-deficient mice develop megacolon with massive distension of the proximal colon. The number of myenteric ganglia, total neurons per ganglion, and NADPH diaphorase presumptive inhibitory neurons per ganglion are increased in the proximal and distal colon, but decreased in the distal ileum of all Enx-/- mice. Enx-/- mice provide a model for human neuronal intestinal dysplasia (NID), in which myenteric neuronal hyperplasia and megacolon are seen. These results suggest that Enx is required for the proper positional specification and differentiative cell fate of enteric neurons.

Animals↗