Biomedical subjects

T Monden

Publications and source records attributed to T Monden.

At least 73 records · Page 4Linked to original sources

PubMed1996

Function of nuclear co-repressor protein on thyroid hormone response elements is regulated by the receptor A/B domain.

Recently, a family of nuclear co-repressor proteins (TRACs) have been identified that interact with thyroid hormone (TR) and retinoic acid receptors to mediate ligand-independent repression of gene transcription. In this report, we have cloned and characterized a human TRAC, which when expressed as a truncated protein lacking its repressing domains, can abolish endogenous cellular TRAC activity. Use of this inhibitor has uncovered a differential function of TRACs on negative versus positive thyroid hormone response elements and has demonstrated the importance of the TR A/B domain in modulating TRAC function. Thus, isoform-specific functions of the TR may be mediated by their functional interaction with co-repressor proteins.

DNA-Binding Proteins↗

PubMed1996

Mutations of the transforming growth factor beta type II receptor gene and microsatellite instability in gastric cancer.

Forty-three sporadic gastric cancers were analyzed with regard to whether mutations of simple repeated sequences in the transforming growth factor beta type II receptor (TbetaR-II) gene are associated with microsatellite instability (MSI) and gastric carcinogenesis. In 12 of the 43 cancers (28%), MSI was observed at least at 1 of the 2 microsatellite loci. Frameshift mutations of the TbetaR-II gene, all of which were 1 base deletion of 10 adenine repeats, were detected in 3 of 6 cancers, with MSI at 2 loci. However, mutations were not detected in 6 cancers, with MSI only at 1 locus and 31 cancers without MSI. Moreover, microanalysis in these cases revealed that the mutant-type alleles of TbetaR-II were invariably common in different areas within the tumor, in contrast to the markedly variable alleles of microsatellite loci. Our results suggest that frameshift mutation of the TbetaR-II gene may be a critical event associated with MSI and may contribute to carcinogenesis of the stomach. One of the possible mechanisms of escape from growth control by TGFbeta during gastric carcinogenesis could involve frameshift mutations of the TbetaR-II gene caused by DNA replication errors.

Adenine↗

PubMed1996

Expression of truncated midkine in human colorectal cancers.

Midkine (MK) is a growth differentiation factor originally found as the product of a retinoic acid-responsive gene. The expression of MK was examined in 35 surgically resected specimens of primary colorectal cancer using the reverse transcription-polymerase chain reaction (RT-PCR). All of the cancerous tissues expressed MK. In 5/25 cancerous tissues a truncated form of MK, which was recently found in various human tumor cell lines, was detected in addition to the full-size MK. In contrast, the truncated from of MK could not be detected in non-cancerous tissues, whereas the wild-type form was detected in 8/10 non-cancerous tissues. These results suggest that the expression of the truncated form of MK may be associated with tumorigenesis.

Carrier Proteins↗

PubMed1996

Immunohistochemical study of Cell Cycle Modulators in G(1)-S Transition in Clinical Breast Cancer Tissue.

In the present study, we investigated immunolocalization of the modulators of G(1)-S transition by using monoclonal or polyclonal antibodies for each of the modulators in 65 cases of clinical breast cancer. Two prominent cyclin dependent kinase(cdk)-cyclin complexes, cdk4-cyclin D and cdk2-cyclin E, were proved to have different modes of mutual expression. cdk4-positive lesions were found to equal cyclin D-expressing lesions in 55 cases, while the former were more extensive than the latter in 9 cases. On the other hand, cyclin E expression was detected in all the cases examined and was more dominant than that of cdk2/cdc2 in as many as 40 cases whereas the reverse was seen in only 1 case. Interestingly, cdk4(P<0.01)and cyclin E(P<0.05)expressions showed an inverse relationship with the tumor size and the cancer stage. A similar tendency was also detected for two other positive modulators of G(1)-S transition, indicating that cell cycle progression must be regulated by the cancer itself once it has grown to a certain extent. p21, which has been regarded as a universal inhibitor of the cell cycle, was expressed in 43.1% of the cases examined and its immunoreactivity showed an inverse relationship with lymph node metastasis(P<0.05). It also tended to be absent more frequently in T3 or larger cancers and stage III cases. Moreover, two patients who died as a result of cancer and three patients with recurrence were all p21 negative, suggesting that p21 is prognosticably the most significant of all these modulators.

Journal Article↗

PubMed1996

The tumor suppressor protein APC colocalizes with beta-catenin in the colon epithelial cells.

The APC gene is mutated in familial adenomatous polyposis and sporadic colorectal tumors. The product of this gene is a 300 kDa cytoplasmic protein associated with catenin. In the present study, we examined the subcellular localization of the APC protein and beta-catenin in the mouse colon by double-labeling immunocytochemistry. While the APC protein was localized in the lateral and apical cytoplasm and in microvilli of the epithelial cells, beta-catenin was present exclusively in the lateral cytoplasm. Double-labeling-immunoelectron microscopy demonstrated precise colocalization of the APC protein and beta-catenin along the lateral plasma membrane. These results suggest that the APC protein functions in cooperation with beta-catenin in the lateral cytoplasm but has other functions independent of beta-catenin in the apical cytoplasm and in microvilli.

Adenomatous Polyposis Coli Protein↗

PubMed1996

Analysis of cytotoxic activity of the CD4+ T lymphocytes generated by local immunotherapy.

We previously reported that the anti-tumour effect of OK-432 is considerably enhanced by its intratumoral injection together with fibrinogen. In the present study, we generated killer T cells by culturing tumour-infiltrating lymphocytes from thyroid cancer patients who had received this local immunotherapy. Phenotypic analysis revealed that the T cells were positive for CD3+, CD4+, Leu8-, CD45RO+ and T-cell receptor (TCR)alpha beta+, as well as showing strong surface expression of HLA-DR, CD25, LFA-1 and ICAM-1. The generated CD4+ T cells secreted interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha, TNF-beta, and interleukin (IL)-6 (but not IL-4), and exhibited a high level of cytolytic activity against several tumour cell lines. The cytolytic activity of these T cells for Daudi cells was inhibited by preincubation with an anti-intercellular adhesion molecule (ICAM)-1 antibody, but not by preincubation with anti-TCR alpha beta, anti-CD2, or anti-LFA-1 antibodies. Pretreatment with anti-ICAM-1 antibody inhibited T-cell cytolytic activity, but not conjugation with target cells. In addition, incubation with immobilised anti-ICAM-1 enhanced the secretion of IFN-gamma by T cells. We conclude that ICAM-1 expressed on the effector cytotoxic CD4+ T lymphocytes delivers regulatory signals that enhance IFN-gamma secretion.

Adjuvants, Immunologic↗

PubMed1996

Primary human fibroblasts induce diverse tumor invasiveness: involvement of HGF as an important paracrine factor.

Fibroblasts have been considered to play an important role in tumor progression. In order to evaluate the contribution of fibroblasts to tumor invasion, TE2-NS, an esophageal cancer cell line, was cultured on collagen gel containing primary fibroblasts derived from normal esophageal submucosa or cancerous tissues of seven esophageal cancer patients. TE2-NS showed diverse invasiveness into the underlying gel containing fibroblasts, but did not invade the gel not containing fibroblasts. The invasiveness of TE2-NS, which expressed hepatocyte growth factor (HGF) receptor, was well-correlated with the concentration of HGF in conditioned medium. Administration of neutralizing antibody against HGF effectively suppressed the invasion, but application of recombinant HGF without fibroblasts induced little invasion into the gel. Fibroblasts from non-cancerous tissue generally secreted a larger amount of HGF and induced tumor invasion to a greater extent than those from cancer tissue, with large diversity. Interestingly, HGF secretion of fibroblasts from non-cancerous tissue was stimulated by co-culture with TE2-NS in two lines, but not in the other four. These results indicate that HGF is an important paracrine factor which induces tumor cell invasion, and the diversity of HGF production by fibroblasts might suggest different potentiality to induce tumor invasion among patients.

Cadherins↗

PubMed1996

Beta-catenin expression in human cancers.

Cell-cell adhesion in tissue is mainly regulated by homotypic interaction of cadherin molecules, which are anchored to the cytoskeleton via cytoplasmic proteins, including alpha- and beta-catenin. Although we previously demonstrated that alpha-catenin is crucial for cadherin function in vivo, little is known about the role of beta-catenin. We examined the expression of beta-catenin in human carcinoma samples along with normal tissue (esophagus, stomach, and colon) by immunostaining using our antibody for beta-catenin. Normal epithelium strongly expressed beta-catenin. However, beta-catenin expression was frequently reduced in primary tumors of the esophagus (10 of 15, 67%), stomach (9 of 19, 47%), and colon (11 of 22, 50%). From an immunoprecipitation study, we found that beta-catenin forms a complex with E-cadherin not only in the normal epithelium but also in cancerous tissues. In coexpression patterns of E-cadherin and beta-catenin, 43 (77%) of the 56 tumors showed a similar expression of both molecules, whereas the other 13 tumors (23%) showed positive staining for E-cadherin and reduced expression of beta-catenin. These findings suggest that beta-catenin forms a complex with E-cadherin in vivo and down-regulation of beta-catenin expression is associated with malignant transformation.

Adenocarcinoma↗

PubMed1996

[Locoregional injection of OK-432/fibrinogen/thrombin for unresectable metastatic liver tumors].

We performed the locoregional injection of OK-432/fibrinogen/thrombin to unresectable hepatic tumors metastasized from colorectal cancers, which were hardly controlled by arterial infusion chemotherapy. CEA was markedly decreased following this treatment, although abdominal CT did not show a significant reduction of tumor mass. This immuno-injection therapy may be a choice of treatment for metastatic liver tumors, refractory to treatment by conventional chemotherapy.

Antineoplastic Agents↗

PubMed1996

[A patient with unresectable cancer of pancreas head, effectively treated by a local injection of the mixture of OK-432, fibrinogen and thrombin].

The effective treatment of unresectable pancreatic cancer remains to be elucidated. We report herein a patient who underwent a local injection of a mixture of OK-432, fibrinogen and thrombin. Tumor size and tumor markers significantly decreased following this procedure. Local injection therapy with OK-432, fibrinogen and thrombin may be a promising treatment for unresectable pancreatic cancer.

Adenocarcinoma↗

PubMed1996

[RB gene expression in gastrointestinal tract].

pRB, the retinoblastoma tumor suppressor gene product, regulates the cell cycle at G1/S transition negatively. Many cell cycle regulators modulate pRB function through its phosphorylation status. G1 cyclins (cyclin D, E)/cyclin-dependent kinases (cdk2, 4) inactivates pRB through its phosphorylation, while p21 (WAF1) and p16 inhibit cdks. In several kinds of cancer, Rb gene alteration or functional inactivation of pRB has been reported. In esophageal cancer, loss of heterozygosity of Rb gene and cyclin D gene amplification were frequently detected. But in gastric and colorectal cancer, Rb gene loss or deletion has been shown to be rare. In this study we investigated the expression of pRB, G1 cyclins, cdks and cdk-inhibitors in adenoma-carcinoma sequence of colorectum. And we compared the phosphorylation status of pRB in colorectal normal mucosa and cancer tissue. In adenoma only cyclin D and E were overexpressed but not cdks. In cancer in adenoma pRB and cdk2 were overexpressed with high frequency, and cdk4 overexpression was detected in advanced cancer. p16 overexpression was detected in almost all cancers, but in contrast p21 overexpression was rare event. Comparative study showed that pRB-positive cancer cells also expressed both cdc2/cdk2 and cyclin E. Densitometric analysis revealed that in advanced cancer pRB was hyperphosphorylated compared with normal mucosa. These results indicate that overexpression of cyclin D/cdk4 and cyclin E/cdk2 would phosphorylate pRB, and insufficient expression of p21 may accelerate pRB inactivation.

Cell Cycle↗

PubMed1996

[Cyclin D, CDK4 and p16 expression in colorectal cancer].

G1/S transition of cell cycle is regulated by G1 cyclins/cyclin-dependent kinases (CDKs) and their inhibitors. Cyclin D/CDK4 complex phosphorylates retinoblastoma gene product and p16 inhibits CDK4 in competition with cyclin D. Aberrant expression of these proteins may deregulate cell proliferation and moreover may lead to tumor formation and progression. In this study we examined the expression of cyclin D, CDK4 and p16 in adenoma-carcinoma sequence of colorectum. Immunohistochemical staining revealed that cyclin D was overexpressed in 55 of 66 (83%) adenomas, 8 of 8 (100%) carcinomas in adenoma (CIAs), 26 of 45 (58%) advanced carcinomas and even in hyperplastic mucosa. CDK4 was overexpressed in 0 of 52 (0%) adenomas, 0 of 14 (0%) CIAs and 39 of 45 (87%) advanced carcinomas, but not in hyperplastic mucosa. p16 was overexpressed in only 5 of 52 (10%) adenomas, 10 of 14 (71%) CIA and 59 of 60 (98%) advanced carcinomas, but not in hyperplastic mucosa. And comparative study of CDK4 and p16 showed that CDK4-positive cancer cells also expressed p16. Western blot analysis also revealed that primary regions of advanced colorectal cancer tissues showed 4.61, 3.30, 1.65 and 8.03-fold overexpression on the average in cyclin D1, cyclin D2, CDK4 and p16 respectively. These results indicate that both cyclin D and CDK4 may contribute to phosphorylation of pRB. p16 overexpression would be induced as a brake at G1/S transition through pRB phosphorylation by CDK4 overexpression in advanced colorectal carcinomas.

Adenoma↗

PubMed1995

The sugar composition and partial structure of the self-induced endogenous elicitor from potato.

The self-induced endogenous elicitor isolated from potato having molecular weight 9200 was degraded with trifluoroacetic acid to determine the sugar composition. The requisite composition of the elicitor was estimated to be a 2:3:4:7 mixture of galactose, rhamnose, arabinose, and galacturonic acid. Furthermore, the structure of oligogalacturonic acid moiety was found to consist mainly of alpha-1,4-pentagalacturonic acid by use of high pH anion exchange chromatography-pulsed amperometric detection.

Carbohydrate Conformation↗

PubMed1995

Activation of the thyrotropin-releasing hormone (TRH) receptor by a direct precursor of TRH, TRH-Gly.

We studied the mechanism by which thyrotropin-releasing hormone (TRH)-Gly stimulated prolactin and thyrotropin (TSH) secretion in pituitary, using a pituitary mammotropic cell line, GH3 cells, and a cell line stably expressing a human TRH receptor (TRH-R). In GH3 cells expressing endogenous TRH-R, an addition of TRH-Gly evoked an immediate rise of intracellular calcium concentration, indicating that TRH-Gly reacted directly without converting from TRH-Gly to TRH. In order to determine whether this reaction might occur through TRH-R, we established a cell line stably expressing a human TRH-R, by transfecting a human TRH-R cDNA into Chinese hamster ovary cells (CHO cells). In this cell line, 10 nM TRH elevated intracellular calcium significantly; the Kd for MeTRH was 1.7 nM. One micromolar and 100 nM TRH-Gly also elevated intracellular concentration of calcium significantly, but not in CHO cells which were not transfected with the TRH-R cDNA. Competition studies further revealed that TRH-Gly displaced MeTRH binding (IC50, 12 microM). These data indicate that at high concentration, TRH-Gly interacts directly with TRH-R to activate signal transduction pathway, and that release of prolactin and TSH induced by TRH-Gly in vitro may be due, at least in part, to the direct effect of TRH-Gly on the TRH-R.

Animals↗

PubMed1995

Ligand-independent and -dependent functions of thyroid hormone receptor isoforms depend upon their distinct amino termini.

Isoform specificity likely plays a large role in the ability of the thyroid hormone receptor (TR) to specifically regulate gene expression in both the presence and absence of its cognate ligand, triiodothyronine. To investigate further the mechanism of isoform specificity of human TRs (TR alpha 1 and TR beta 1), we have examined their functional effects on positive thyroid hormone response elements (TREs) both in the presence and absence of ligand. TR alpha 1 was greater than 2-fold more potent than TR beta 1 on both TREs studied, in terms of both ligand-independent repression and ligand-dependent stimulation. By creating a number of chimeric and mutant receptors, we have established that the increased functional potency of TR alpha 1 is due to its unique amino terminus. Deletion or substitution of the TR alpha 1 amino terminus leads to a loss of both its ligand-independent and -dependent functions on positive TREs. Furthermore, the TR alpha 1 amino terminus antagonizes homodimer formation on the positive TREs studied. TR constructs, which contain the TR alpha 1 amino terminus, are unable to form homodimers and form exclusively heterodimers with RXR alpha on direct repeat and palindromic TREs. Deletion of the amino terminus from either TR isoform leads to preferential homodimer formation, which suggests that the TR amino terminus is important for relative heterodimerization capability. From these data, we conclude that TR alpha 1 isoform specificity on positive TREs resides predominantly in its amino terminus through its ability to favor heterodimerization with the retinoid X receptor or other nuclear proteins.

Base Sequence↗

PubMed1995

Coexpression of cdk2/cdc2 and retinoblastoma gene products in colorectal cancer.

The retinoblastoma gene (Rb gene) is a tumour-suppressor gene and its product (pRB) is known to act as a negative regulator of the cell cycle. Although lack of pRB expression resulting from gene alterations is considered to be responsible for the genesis of several human malignancies, increased expression of pRB has been demonstrated in a majority of colorectal cancer cases. In the present study, we investigated the expression of pRB as well as that of its related kinases, cdk2 and cdc2, in colorectal cancer, since these kinases have been reported to phosphorylate and inactivate pRB. Western blot analysis revealed that colorectal cancer expressed higher levels of cdk2 and cdc2 than did normal mucosa and that the ratio of the hyperphosphorylated form of pRB was higher in colorectal cancer. Furthermore, immunohistochemical studies showed that cdk2/cdc2 was expressed exclusively in the cancer cells positive for pRB. These results suggest that an increase in the expression of cdk2/cdc2 in colorectal cancer may have prevented pRB from braking the cell cycle through phosphorylation.

Blotting, Western↗

PubMed1995

A novel analog of TRH, YM14673, causes a decrease in brain TRH receptors in vitro.

Biochemical mechanisms by which analogs of thyrotropin-releasing hormone (TRH) produce their potent neuropharmacological actions on the brain remain ill-defined. We tested effects of YM14673, a novel analog of TRH, on TRH receptors in rat brains in vitro. No significant binding of [3H]YM14673 to brain plasma membranes occurred. In contrast, preincubation of membranes with YM14673 caused dose-dependent decreases in TRH binding. This was not due to competition for TRH binding sites or existence of metabolites of YM14673. Preincubation with DN1417 (an another TRH analog), cyclo(His-Pro) or methionine-enkephalin did not affect the binding. Affections of YM14673 on TRH binding were observed when cerebral cortical membranes were studied; those were not seen in membranes prepared from hypothalamus, striatum, midbrain, hippocampus, or pons-medulla. The present data indicate that YM14673 exerts its characteristic neuro-pharmacological functions through interacting with TRH binding sites in the brain.

Animals↗

PubMed1995

The human thyrotropin-releasing hormone gene is regulated by thyroid hormone through two distinct classes of negative thyroid hormone response elements.

TRH is the principal positive regulator of TSH synthesis and secretion in man. T3 is able to control TRH synthesis through feedback inhibition at the transcriptional level, presumably by binding to its receptor which interacts with one or more negative thyroid hormone response elements (TREs) present within the human TRH promoter. In the present study we have identified the specific negative TREs within the TRH promoter and characterized their ability to interact with thyroid hormone receptors (TRs), and the retinoid X receptor (RXR). Our analysis demonstrates that ligand-independent and dependent regulation of the human TRH promoter is restricted to the TR beta 1 isoform. Deletional analysis of the TRH promoter identified two discrete regions that are responsible for mediating ligand-dependent negative regulation of the TRH promoter. Mutagenesis of potential TR binding half-sites within these regions identified three separate half-sites (site 4 from -55 to -60 base pairs (bp); site 5, +14 to +19 bp; and site 6, +37 to +42 bp) which act in combination to allow for negative regulation. Mutation and/or deletion of each of these sites leads to a loss of negative regulation of the TRH promoter by T3. Gel-mobility shift assays of site 4 and its surrounding nucleotides revealed that this region of the promoter is capable of binding TR monomers, homodimers, and TR-RXR heterodimers. Mutagenesis of site 4 leads to a loss of all binding to this region. The region encompassing sites 5 and 6 binds only TR monomer, and the addition of RXR to the binding reaction leads to a loss of specific monomeric binding. To assess the functional importance of site 4 and its surrounding nucleotides we cotransfected RXR isoforms along with TR beta with TRH promoter constructs containing either site 4 or its mutant. In the presence of wild type site 4 sequence, cotransfected RXR enhanced negative regulation of the TRH promoter. Mutation and or deletion of site 4 leads to a loss of this enhancement. These data demonstrate that two structurally different negative TREs cooperate to allow for negative regulation of the human TRH promoter and that negative regulation is TR isoform-specific and modulated by the RXR-signaling pathway through a novel negative TRE.

Animals↗