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Biomedical subjects

O Hino

Publications and source records attributed to O Hino.

At least 55 records · Page 3Linked to original sources
PubMed1999

Renal carcinogenesis, hepatic hemangiomatosis, and embryonic lethality caused by a germ-line Tsc2 mutation in mice.

Germ-line mutations of the human TSC2 tumor suppressor gene cause tuberous sclerosis (TSC), a disease characterized by the development of hamartomas in various organs. In the Eker rat, however, a germ-line Tsc2 mutation gives rise to renal cell carcinomas with a complete penetrance. The molecular mechanism for this phenotypic difference between man and rat is currently unknown, and the physiological function of the TSC2/Tsc2 product (tuberin) is not fully understood. To investigate these unsolved problems, we have generated a Tsc2 mutant mouse. Tsc2 heterozygous mutant (Tsc2+/-) mice developed renal carcinomas with a complete penetrance, as seen in the Eker rat, but not the angiomyolipomas characteristic of human TSC, confirming the existence of a species-specific mechanism of tumorigenesis caused by tuberin deficiency. Unexpectedly, approximately 80% of Tsc2+/- mice also developed hepatic hemangiomas that are not observed in either TSC or the Eker rat. Tsc2 homozygous (Tsc2-/-) mutants died around embryonic day 10.5, indicating an essential function for tuberin in mouse embryonic development. Some Tsc2-/- embryos exhibited an unclosed neural tube and/or thickened myocardium. The latter is associated with increased cell density that may be a reflection of loss of a growth-suppressive function of tuberin. The mouse strain described here should provide a valuable experimental model to analyze the function of tuberin and its association with tumorigenesis.

Animals↗
PubMed1999

Isolation and characterization of a rat homologue of the human tuberous sclerosis 1 gene (Tsc1) and analysis of its mutations in rat renal carcinomas.

In the Eker rat, a germ-line mutation in the homologue of the human tuberous sclerosis gene (Tsc2) causes renal cell carcinomas (RCs) with a complete penetrance in all heterozygotes. Tsc2 mutations have also been found in a subset of chemically induced non-Eker rat RCs. Because tuberous sclerosis patients with alteration of either of the two predisposing genes (TSC1 and TSC2) show identical symptoms, the products of these two genes are thought to be involved in a common biological pathway. In this study, to analyze the possible overlap between the functions of Tsc2 and Tscl gene products, we isolated and characterized a rat homologue of the TSC1 gene (Tsc1). The rat Tsc1 gene, which has an identical exon-intron structure to that of human TSC1 and is localized on rat chromosome 3, has been shown to encode a protein (hamartin) that is highly homologous to the human counterpart with an approximately 86% amino acid sequence identity. Using PCR-single-strand conformational polymorphism analysis, we identified two splicing donor site mutations in one chemically induced rat RC (1 of 15). This suggests that alterations of the Tsc1 gene may be involved in the development of a subset of rat RCs.

Adult↗
PubMed1999

Determination of the clonal origin of multiple human hepatocellular carcinomas by cloning and polymerase chain reaction of the integrated hepatitis B virus DNA.

The poor prognosis of hepatocellular carcinoma (HCC) is partly the result of the high rate of recurrence that is caused either by intrahepatic metastasis (IM) or independent multicentric occurrence (MO). For convenience, discrimination of IM and MO is based on pathological findings, but reliable parameters are not sufficiently established. In the case of hepatitis B virus (HBV)-associated HCC, molecular discrimination of IM from MO can be achieved by comparison of integrated HBV DNAs. However, Southern blotting cannot be used for this purpose when one tumor is saved in frozen form and the other is in paraffin-embedded form. To solve this problem, we employed polymerase chain reaction (PCR) assays to confirm the clonality of primary and recurrent tumors. From the frozen tissue, we determined the junction between the integrated HBV and flanking genomic DNA by molecular cloning, and checked the existence of an identical junction in the DNA of paraffin-embedded tissue by PCR. Using this method, as well as Southern blotting, we proved in 6 of 8 patients that two nodular HCC lesions resected metachronously or simultaneously were caused by MO, while the remaining 2 cases were caused by IM. In 1 IM case, band patterns between two HCCs detected by Southern blotting were not identical.

Aged↗
PubMed1999

Distribution of Tsc2 protein in various normal rat tissues and renal tumours of Tsc2 mutant (Eker) rat detected by immunohistochemistry.

Alterations in the rat tuberous sclerosis gene (Tsc2) are responsible for the hereditary renal carcinomas (RCs) of Eker rat. We examined protein distribution in various normal rat tissues and the Eker RCs by immunohistochemistry. Tsc2 protein is expressed in the mammary ducts, salivary glands, gastric glands, parathyroid, small and large intestine, ovary and uterus. Specific expression of Tsc2 protein is found in the B cells of pancreatic islets and in the smooth muscle of lung veins. Interestingly, in the RCs of Eker rat, Tsc2 protein was detectable with some variation in reactivity.

Animals↗
PubMed1999

Hepatitis C virus and hepatocarcinogenesis.

Although human hepatocellular carcinoma (HCC) is one of the most common types of tumors in the world, the molecular mechanisms underlying hepatitis-C-related human hepatocarcinogenesis are still not clear. HCC is accompanied by virus infections in most cases, and it is suggested that hepatitis B virus and hepatitis C virus (HCV) significantly influence the oncogenic process. The persistence of inflammation following HCV infection is reportedly related to carcinogenesis, and the mechanism of chronic inflammation has been approached by taking viral, immunologic, cytokine and apoptotic responses into consideration. With the progress made in molecular biology, the functional abnormality of oncogenes/tumor suppressor genes has been identified and, apart from the p53 gene, involvement of the IGF-II gene has also been described recently. Furthermore, it has been suggested that uncontrolled proliferation of cancer cells might be based on abnormal regulation of intracellular signal transduction pathways. Here we review the cutting edge of molecular hepatitis C virology in terms of virus-cell interactions, which may contribute to the development of human HCCs. We also discuss the recent progress made in the molecular and cell biology of human hepatocarcinogenesis.

Chromosome Aberrations↗
PubMed1999

Chronic hepatitis in interferon-gamma transgenic mice is associated with elevated CPP32-like activity and interleukin-1beta-converting enzyme activity suppression.

Interferon-gamma (IFN-gamma) transgenic mice strongly express IFN-gamma in the liver and develop chronic hepatitis. Furthermore, hepatocyte apoptosis was shown by the TdT-mediated dUTP-biotin nick endlabeling method. In the present study, interleukin-1beta-converting enzyme (ICE) and CPP32-like protease activities in the liver of IFN-gamma transgenic mice were measured, using the synthetic substrates Ac-YVAD-MCA and Ac-DEVD-MCA. Plasma aspartate aminotransferase and alanine aminotransferase activities as well as CPP32-like activity were significantly elevated, while ICE activity was significantly reduced. The addition of the ICE inhibitor Ac-YVAD-CHO to IFN-gamma transgenic mouse liver cell cytosol had no effect on the CPP32 activity, in contrast to a CPP32 inhibitor. The present results indicate that chronic hepatitis in the IFN-gamma transgenic mouse is associated with a decrease in ICE and induction of CPP32-like activity.

Alanine Transaminase↗
PubMed1999

The mouse interferon-gamma transgene chronic hepatitis model (Review).

Acute hepatitis models are widely used for the evaluation of drugs for liver disease or for basic research on hepatitis. However, it is difficult to produce similar liver conditions to human chronic hepatitis with an acute hepatitis model. The interferon-gamma (IFN-gamma) transgenic mouse, which carries the mouse IFN-gamma gene, strongly expresses the IFN-gamma gene in the liver and develops chronic hepatitis from the age of 6-10 weeks. We found that the hepatitis in this mouse reflects human chronic hepatitis at least in the following points, i) infiltration by lymphoid cells into the portal areas and necroinflammation in the lobules, and ii) expression of Fas antigen and Fas ligand mRNAs in the liver. Furthermore, the induction of CPP32-like protease activity in the transgenic mouse liver suggests the involvement of this protease activity in the development of chronic hepatitis.

Animals↗
PubMed1999

Long lasting chronic hepatitis is accompanied by cyclin D1 gene expression in the mouse.

The interferon-gamma (IFN-gamma) transgenic mouse expresses the IFN-gamma gene strongly in the liver and develops chronic hepatitis from 6-10 weeks of age. Previously we reported the detection of hepatocyte apoptosis and the expression of the Fas system in the transgenic mouse liver. The objective of the present study was to examine the possible development of favorable conditions for predisposing cells to malignancy. The connection between the cell cycle and cancer has become evident, and the relation of cyclin D1 (CD1) with hepatocellular carcinomas has been strengthened. In the liver of transgenic mice of 48 weeks of age, c-myc and CD1 gene expression was induced, indicating progression of the cell cycles. p21 gene expression in the transgenic mouse liver might counteract cell-cycle progression promoted by c-myc and CD1. In the liver of 8-week-old transgenic mice, expression of c-myc mRNA was correlated with the levels of plasma transaminase activities. In these 8-week-old transgenic mice, however, CD1 mRNA was not induced, regardless of the progression of hepatitis. Based on these results, we conclude that long lasting hepatitis may lead to favorable conditions for predisposing cells to malignancy.

Animals↗
PubMed1999

[Prevalence of TT virus infection and viral integration in human hepatocellular carcinoma].

In 1997, Nishizawa et al cloned a novel DNA virus designated as TT virus (TTV) from a patient with post-transfusion hepatitis and this virus is being thought to be a new hepatitis virus. Approximately 5 to 10% of hepatocellular carcinomas (HCCs) in Japan occurs in hepatitis B virus-negative and hepatitis C virus-negative (NBNC) patients. In order to study the possible role of TTV in hepatocarcinogenesis, we studied the prevalence of the TTV DNA in liver tissue of HCC patients. As a result, TTV was shown not to be specific for NBNC HCC and TTV integration into host DNA was not detected in any HCC patient by Southern blotting.

Biomarkers↗
PubMed1998

Hepatocellular carcinomas infected with the novel TT DNA virus lack viral integration.

A novel DNA virus designated TT virus (TTV) was cloned from a patient with posttransfusion hepatitis and is thought to be a new hepatitis virus. At present, hepatitis B virus (HBV) and hepatitis C virus (HCV) are known to induce hepatocellular carcinoma (HCC). But, actually, in Japan approximately 5 to 10% of HCCs are in HBV-negative and HCV-negative (NBNC) patients. In order to study the possible role of TTV in hepatocarcinogenesis, we investigated the frequency of the TTV genome in liver tissue of 20 HCC patients. As a result, 3 of 8 NBNC HCC patients and 5 of 12 HBV- or HCV-associated HCC patients were TTV positive, and TTV was shown not to be specific for NBNC HCC. For all TTV-positive patients, we also confirmed that the TTV genome was not integrated into host hepatocyte DNA.

Aged↗
PubMed1998

Biallelic mutations of the Tsc2 gene in chemically induced rat renal cell carcinoma.

A number of cancer genes have been identified by the study of hereditary human cancers and shown to be involved in sporadic genesis of the same tumors. We have identified a germline mutation in the rat homologue of the human tuberous sclerosis (TSC2) predisposing gene in the Eker rat model. In this study, we searched for mutations of the Tsc2 gene in chemically induced non-Eker rat renal cell carcinomas (RCs). N-ethyl-N-hydroxyethylnitrosamine (EHEN)- and diethylnitrosamine (DEN)-induced non-Eker rat primary RCs were subjected to polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis using specific primers covering all exons of the Tsc2 gene (41 coding exons and 1 non-coding exon). We simultaneously searched for mutations in the Vhl gene, a rat homologue of von Hippel-Lindau disease (VHL) gene, as well as the Tsc2 gene. Mutations in the Vhl gene were not detected in any rat RCs (0/8). In contrast, Tsc2 gene mutations were detected at a high frequency in EHEN-induced RCs (2/3) and DEN-induced RCs (3/5) (total 5/8) (p < 0.05). By a direct cloning approach utilizing PCR analysis in 2 applicable cases, we could demonstrate the presence of intragenic somatic mutations in both alleles of the Tsc2 gene. Our results suggest that Tsc2 gene inactivation plays an important role in EHEN- and DEN-induced RCs as well as in Eker rat RCs.

Alleles↗
PubMed1998

Paxillin isoforms in mouse. Lack of the gamma isoform and developmentally specific beta isoform expression.

Paxillin, a focal adhesion protein, exists as multiple isoforms in humans (alpha, beta, and gamma). To understand more about the physiological role of each isoform, we have employed the mouse system. We found that although the alpha and beta isoforms are present in the mouse, the gamma isoform is not. The alpha isoform protein was detected clearly in most adult tissues, whereas the beta isoform protein was almost undetectable except in spleen, testis, thymus, and lung. On the other hand, mRNAs of both isoforms were detectable in all tissues we examined. High levels of the beta isoform protein was detected in peritoneal exudate macrophage cells in adult mouse as well as in cultured fibroblasts, together with the alpha isoform. The alpha isoform was expressed at a constant level throughout the embryonic stages we examined, whereas the beta isoform protein was detected at the mid-stages of development and increased to levels almost equal to those of the alpha isoform during the late stages of embryogenesis. Therefore, unlike the alpha isoform, expression of the beta isoform protein is restricted in adult tissues. Moreover, we showed that alpha and beta isoforms were colocalized within the same focal adhesion plaques, and cytoplasmic pools of both isoforms exist in the perinuclear area, colocalized with the Golgi apparatus.

3T3 Cells↗
PubMed1998

Identification of cDNAs induced by the tumor suppressor Tsc2 gene using a conditional expression system in Tsc2 mutant (Eker) rat renal carcinoma cells.

Alteration of the rat homologue of the tuberous sclerosis 2 (TSC2) gene is associated with dominantly inherited cancer in the Eker rat model, indicating a tumor suppressor nature. The ability of Tsc2 to activate signal transduction and transcription suggests that genes induced by Tsc2 may mediate its biological roles. Using a subtractive hybridization approach in combination with tetracycline operator systems, we identified a set of downstream genes affected by Tsc2. Regulated expression of wild-type Tsc2 gene in Eker renal carcinomas (RCs) resulted in marked expression of cell arrest or programmed cell-death-related genes and stress-induced genes. Thus, the data suggest that Tsc2 might contribute to regulation of the cell cycle and cell survival.

Animals↗