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Biomedical subjects

Y Hiasa

Publications and source records attributed to Y Hiasa.

At least 37 records · Page 2Linked to original sources
PubMed1998

Different ras gene mutational frequencies in thyroid papillary carcinomas in Japan and Thailand.

The incidence and pattern of ras oncogene mutations in human malignancies demonstrate geographic and racial differences. For example, specificity of alterations is found in cholangiocellular carcinomas in Thai patients with a different etiology from those in Japanese patients. In the present study, a comparison of ras gene mutations in thyroid papillary carcinomas from Japanese and Thai patients was performed using single-strand conformation polymorphism and direct sequencing analyses. The incidence of ras mutation differed markedly in Japanese (two of 24 carcinomas, 8.3%) and Thai (five of 10 carcinomas, 50%) patients. In addition, all but one ras mutation occurred at codon 12 of the K-ras gene in the Thai cases. These results suggest that thyroid cancers in Thailand may be due to specific genetic and/or environmental factors.

Adult↗
PubMed1998

Low stimulatory capacity of lymphoid dendritic cells expressing hepatitis C virus genes.

To determine the role of antigen presenting cells (APCs) during hepatitis C virus (HCV) infection, murine lymphoid dendritic cells (LDCs), the most potent APCs, were transfected with HCV genes using adenovirus vector-mediated gene transfer. At a multiplicity of infection (MOI) of 100, more than 90% of the transfected LDCs expressed the HCV genes (encoding core-E2 region). The stimulatory capacity of these LDCs (LDC-AxCA327) in the allogeneic mixed leukocyte reaction (Allo MLR) was significantly lower (P < 0.01) than that of LDCs infected with control adenovirus vector lacking the HCV genes (LDC-Axw1). LDC-AxCA327 also produced significantly lower levels of IL-12 than LDC-Axw1 (P < 0.05). These findings suggest that the inadequate APC capability of LDCs that express HCV genes is related to immunopathology during HCV infection and that IL-12 appears to be involved in this process.

Animals↗
PubMed1998

Formation of 8-hydroxydeoxyguanosine in rat kidney DNA after administration of N-ethyl-N-hydroxyethylnitrosamine.

N-Ethyl-N-hydroxyethylnitrosamine (EHEN) is known to induce renal and liver tumors in rodents. Recent reports have indicated the formation of 8-hydroxydeoxyguanosine (8-OHdG), an oxidative DNA product, induced by various carcinogens. In the present study, to examine whether oxygen radicals are involved in tumorigenesis induced by EHEN, we investigated the formation and localization of 8-OHdG in kidney, liver and lung of rats. The effects of reduced glutathione (GSH) and diethylmaleate on these responses were also studied. Multiple doses of EHEN administrations (250, 500 or 750 mg/kg, i.p.) resulted in a significant elevation of the 8-OHdG level in kidney DNA in a dose-dependent manner and the formation of 8-OHdG reached the maximal level at 1-2 h after EHEN injection and recovered to the control level at 4 h. On the other hand, no increase in the 8-OHdG level was observed in the DNA of liver and lung. Combined pre- and post-treatment of rats with 2 x 800 mg/kg of GSH i.p. inhibited the elevation of the 8-OHdG level induced by EHEN. Pre-treatment with 0.3 ml/kg of diethylmaleate i.p. increased the formation of 8-OHdG. In the immunohistochemical examinations of rats treated with EHEN (750 mg/kg, i.p.), nuclear expression of 8-OHdG was detected in the epithelial cells of renal cortex, while no induction was observed in liver and lung. These findings suggest that the formation of 8-OHdG by active oxygen species may be an important factor in the initiation of EHEN-induced kidney carcinogenesis.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1998

Frequent alterations of cell-cycle regulators in astrocytic tumors as detected by molecular genetic and immunohistochemical analyses.

Alterations of CDKN2A, RB, and cyclin D1 genes and expression of their products in astrocytic tumors were studied using a combination of molecular genetic and immunohistochemical assays. In addition, the association of gene status with clinical outcome was evaluated. Alterations of CDKN2A and RB gene in 30 lesions were analyzed by single-strand conformation polymorphism of polymerase chain reaction (PCR-SSCP), direct sequencing, and Western blotting. Methylation of the CDKN2A promoter was detected by methylation-specific PCR. Immunohistochemistry was applied to determine the expression of gene products in tumors from 94 patients for whom clinical outcome was also evaluated. Analyses of the CDKN2A gene revealed 12 homozygous or hemizygous deletions, one mutation in exon 1, and three methylations in the promoter. Expression of p 16 protein was not detected in 18 of 30 cases. RB mutations leading to loss of expression of the pRb were found in four (13%) cases, and six were immunohistochemically negative for this protein. Overexpression of cyclin D1 was obtained in 51 (54%) of 94 cases. Patients with pRb-negative tumors had a significantly greater risk of earlier death than those with p16 and cyclin D1 alterations, Both p16 and pRb immunohistochemistry provides useful complementary information and may provide valuable predictive information in screening. The biological consequences of deregulating individual components along cell control pathways are unequal, perhaps reflecting their hierarchical roles in the G1 checkpoint.

Adolescent↗
PubMed1998

Genetic variations in recurrent astrocytic tumors detected by restriction landmark genomic scanning.

The genetic mechanisms associated with recurrence of advanced astrocytic tumors are poorly understood. We therefore analyzed 24 biopsy specimens from 12 patients with a recurrent astrocytic tumor by a two-dimensional gel electrophoresis method, termed restriction landmark genomic scanning (RLGS). Four spot changes were commonly present in the primary astrocytomas, indicating that the corresponding gene alterations were early events in the development of this tumor type. Altered spots were more frequent and of different distribution in recurrent tumors than in the primary astrocytomas. In particular, specifically increased intensity for spots on chromosomes 9-12 and 18 were observed in the secondary tumors, suggesting a relation with recurrence. The same spot changes observed in primary tumors were also found in the respective secondary lesions but with strikingly different densities in some cases, suggesting increased genetic instability. The altered segments provide important candidate regions for the search for genes involved in events leading to progression and more malignant recurrent tumors.

Astrocytoma↗
PubMed1998

Genomic aberrations in renal cell carcinomas detected by restriction landmark genomic scanning.

In order to reveal and characterise genetic events occurring in renal tumorigenesis, samples of sporadic renal cell carcinomas (RCCs) were examined using restriction landmark genomic scanning (RLGS), an electrophoretic separation technique which detects gene amplification and deletion. We were able to find two fragments frequently amplified and 10 others commonly showing reduced signal intensity within the 16 tumour samples analysed. These altered spots were located on chromosomes 2, 3, 9-12, 16, 17 and 18 according to chromosomal assigned RLGS. A subset of reduced fragments appeared to be correlated to tumour type and were located within a new chromosomal region, suggesting genetic specificity within the process of renal carcinogenesis.

Aged↗
PubMed1998

Genomic alterations in oral squamous cell carcinoma cell lines detected by two-dimensional gel analysis.

To initially analyze the genomic abnormalities in human oral squamous cell carcinoma, DNA extracted from each of four oral carcinoma cell lines (Ca9-22, HO-1-u-1, HSC-2, KB) was examined using restriction landmark genomic scanning (RLGS), a method especially conducive to detection of amplifications and rearrangements of genomic DNA. Isolated cell line and normal oral epithial DNAs were sequentially cleaved with specific restriction enzymes, radiolabelled and separated in two-dimensional gel electrophoreses. Thirteen distinct fragments were commonly amplified in the oral cancer cell lines, six of which were evident in all samples. These results suggest genetic alterations characteristic of oral squamous cell carcinogenesis.

Carcinoma, Squamous Cell↗
PubMed1998

Drug resistance and apoptosis in ENU-induced rat brain tumors treated with anti-cancer drugs.

To cast light on the mechanisms of drug-resistance, experimental brain tumors were immunohistochemically evaluated for expression of glutathione S-transferase (GST)-alpha, mu, pi, p-glycoprotein and apoptosis-related factors, such as bcl-2 and p53, as well as by the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling (TUNEL) method. Rat brain tumors induced by means of prenatal exposure to ethylnitrosourea (ENU) were treated with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU) and/or vincristine. Tumors more than 2 mm in size were considered to be drug resistant. The expression of GST-mu was strongly positive in ACNU-treated brain tumors, while p-glycoprotein was overexpressed in vincristine-treated brain tumors. Neither p53 nor bcl-2 expression directly correlated with apoptosis identified by TUNEL method, but tumors lacking apoptotic cells always demonstrated the expression of either GST-mu or p-glycoprotein. These results indicate that tumors resistant to chemotherapy might not be susceptible to induction of apoptosis, and therefore that mechanisms of drug resistance are related to programmed cell death in brain tumors.

Animals↗
PubMed1998

Overexpression of CD44 variant transcripts in rat transplantable thyroid carcinoma lines demonstrating lung metastasis.

Expression of CD44 isoforms has been reported to be involved in tumor invasion and metastasis in both rodents and man. We earlier documented establishment of rat transplantable thyroid carcinoma lines in vivo from primary lesions induced by a chemical carcinogen. Recently, two lines (L1a-M4 and L2a-M6) were found to spontaneously metastasize to the lung after subcutaneous transplantation. To determine whether CD44 splice variants contribute to their metastatic spread, carcinoma lines with and without lung metastasis were evaluated quantitatively and qualitatively using RT-PCR followed by hybridization and immunohistochemical analyses. The L1a-M4 and L2a-M6 metastatic lines showed significant overexpression of CD44 variant transcripts containing variant exons v4-v6 or v9-v10/v8-v10, respectively, with concomitant reduced levels of standard transcripts. Investigation of the precise composition of alternatively spliced mRNA in normal tissues and carcinoma lines using an exon-specific RT-PCR method, revealed major chain variant transcripts containing v2/v3, v4-v6, v7-v10 and v8-v10 in all specimens. Applying the same RT-PCR analysis to mRNAs derived from cultured cell lines, demonstrated essentially the same pattern. The results suggest that quantitative increase rather than qualitative change in CD44 variant isoforms is associated with the pathogenesis of lung metastasis of rat thyroid carcinomas.

Alternative Splicing↗
PubMed1998

Detection of DNA amplification in human renal cell carcinoma cell lines using restriction landmark genomic scanning.

Gene amplification, which has often been observed in various human cancers, appears to be associated with the development and progression of malignant phenotypes. However, in renal cell carcinoma (RCC), conventional analytic methods requiring specific primers and probes have revealed infrequent amplification of known oncogenes. We attempted to determine if gene amplification was truly uncommon in RCC. The genomic DNAs extracted from 5 human RCC cell lines were examined by restriction landmark genomic scanning (RLGS), a two-dimensional gel analysis which allows evaluation of approximately 2,000 radiolabelled DNA fragments. By this method, we detected 24 distinct spots commonly amplified in at least 2 RCC cell lines compared to normal kidneys. Comparing the present results with chromosomal assigned-RLGS, approximately one half of these DNA fragments proved to be located on chromosome 2, 5 or 7. Our data suggest that amplification of unknown genes is likely to occur in RCC cell lines.

Carcinoma, Renal Cell↗
PubMed1997

Retinoblastoma protein expression and MIB-1 correlate with survival of patients with malignant astrocytoma.

BACKGROUND: Regulatory coupling of cell proliferation and apoptosis is suggested by recent findings with regard to certain tumors, such as the finding of tumor resistance to anticancer therapy caused by inhibition of apoptosis. The processes leading to apoptosis appear to be regulated by a variety of oncogenes and tumor suppressor genes. In the current study, the relation between apoptosis and expression of retinoblastoma protein (pRB) was assessed in 50 primary anaplastic astrocytomas (AAs) and 46 recurrent tumors in the same patients as the primary tumors after macroscopic total surgical resection and chemoradiotherapy. METHODS: Apoptotic cells were identified by the in situ 3'-end labeling technique. Proliferative potential, pRB expression, and p53 expression were evaluated immunohistochemically using anti-Ki-67 (MIB-1), anti-pRB, and anti-p53 antibodies, respectively. The prognostic value of these biologic markers in AA patients undergoing treatment was also evaluated. RESULTS: The mean apoptotic index (AI) was 0.91 +/- 0.70% for specimens obtained at the initial surgery and 2.32 +/- 1.71% for those obtained at recurrence. There was no apparent correlation between the AI and the MIB-1 staining index (MI) in primary AAs, whereas significantly higher AI and MI were observed in recurrent pRB negative cases than in their pRB positive counterparts. The survival of patients with AAs showing a high MI and negative pRB immunostaining was significantly shorter than in the other cases. Neither the size of the apoptotic fraction nor the p53 expression in primary tumor correlated with the overall survival. CONCLUSIONS: The clinical outcome of patients with AA may be associated with aberrant pRB function and increased proliferative activity rather than an inability of tumor cells to undergo apoptosis.

Adult↗
PubMed1997

Comparison of ras activation in prostate carcinoma in Japanese and American men.

BACKGROUND: Comparative studies of point mutations in K-, N-, and H-ras oncogenes were performed on prostate carcinoma from Japanese and American patients to clarify the racial difference. METHODS: We probed for mutations in 70 Japanese and 31 American specimens using polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) analysis and immunohistochemistry for ras p21. RESULTS: Within the 70 Japanese specimens, eight mutations in codon 12 of K-ras (five GGT-->GTT transversions and three CGT-->GAT transitions) and one mutation in codon 12 of the N-ras gene (a GGT-->GTT transversion) were confirmed, whereas the American samples yielded only one definable mutation, a GGT-->GAT transition, in codon 12 of K-ras. CONCLUSIONS: The frequency of ras gene mutations in clinical carcinoma in Japanese men was higher than that in American men. It is suggested that there may be fundamental differences in the etiology of prostate carcinoma in Japan and the United States, perhaps based on genetics and/or environmental factors.

Adenocarcinoma↗
PubMed1997

Genomic alterations of human gliomas detected by restriction landmark genomic scanning.

Alterations of genomic DNA in eight primary astrocytic tumors and two glioma cell lines were examined using a recently developed two-dimensional gel electrophoresis method called restriction landmark genomic scanning (RLGS). RLGS allows us to detect amplifications, deletions, and methylation in genomic DNA in one procedure without requiring any polymorphic markers. Approximately 2000 spots (landmark sites) in tumor specimens were compared with those in normal brain tissue. The 10 spots with intensified signal were reproducibly detected in at least 50% of primary tumors, implying amplification of corresponding DNA sequences. Conversely, 12 spots with reduced signal were observed in more than 50% of all tumors, suggesting inactivation by allelic loss, homozygous deletion, or CpG island methylation. These results suggest that common genetic alterations are closely correlated with the genesis or progression of human gliomas.

Brain Neoplasms↗
PubMed1997

Analyses of human gliomas by restriction landmark genomic scanning.

The 16 primary gliomas were examined for changes in genomic DNA using a recently developed 2-dimensional gel electrophoresis method called restriction landmark genomic scanning (RLGS). This approach allows detection of DNA amplification, deletion, methylation and potentially other genetic rearrangements represented as decreases and increases in spot/fragment intensity on an autoradiogram. Approximately 2,000 landmark sites in tumor DNA were compared with those of DNA isolated from normal brain tissues. Seven spots showing intensified signal were consistently detected in at least 50% of tumors, implying activation of corresponding DNA sequences, and 8 additional spots having reduced signal were observed, again in more than 50% of all tumors, suggesting inactivation by the loss of 1 allele or homozygous deletion. Decreased signal may also infer relative CpG island methylation state. Of those spots consistently identified in tumors, 2 amplified and 4 reduced spots were found to be characteristic of low- and high-grade tumors, while the remaining 5 amplified and 4 reduced spots were associated with high-grade gliomas only, suggesting a link of specific mutations to degree of malignancy. A separate subset of glioblastomas evaluated, however, showed no alterations in these 'hot spots' which were detected in even low grade astrocytomas. The results demonstrate the genetic heterogeneity of glioblastoma and implicate the progression of neoplasia via differing genetic pathways.

Astrocytoma↗
PubMed1997

Genomic alterations in human glioma cell lines detected by restriction landmark genomic scanning.

Restriction landmark genomic scanning (RLGS) is a 2-dimensional gel analysis capable of detecting amplifications, deletions and rearrangements in genomic DNA. Using RLGS, we examined genomic DNA from each of 6 human-derived malignant glioma cell lines and from normal brain tissue samples. RLGS allows us to screen genomic DNAs as approximately 2,000 landmark sites in one procedure without any polymorphic markers. The resulting 2,000 spots in tumor samples were compared with those in normal brain. Six spots common to 5 of the 6 cell lines showed intensified signal, suggesting amplification of a tumor-specific DNA fragment. In addition, 25 spots common to 5 of the 6 lines showed a decrease in signal intensity, conversely indicating allelic loss of homozygous deletion. These results imply the existence of consistent genetic alterations in human glioma.

Brain Neoplasms↗
PubMed1997

Genetic alterations in N-bis(2-hydroxypropyl)nitrosamine-induced rat transplantable thyroid carcinoma lines: analysis of the TSH-R, G(alpha)s, ras and p53 genes.

It has recently been shown that point mutations of the TSH-R or G(alpha)s genes are associated with autonomous hyperfunctioning thyroid adenomas and differentiated carcinomas. We therefore screened for mutations in the TSH-R, G(alpha)s, ras and p53 genes in nine rat transplantable thyroid carcinoma lines derived from tumors induced by DHPN as a chemical carcinogen. Mutations were identified using single-strand conformation polymorphism and DNA sequencing analysis. Point mutations in G(alpha)s codon 201 (CGC-->CAC) were detected in three lines (33%), resulting in a heterozygous alteration (Arg-->His) in the expressed G(alpha)s protein. The mean intracellular cAMP level (2.30 +/- 0.27 nmol/mg) of the three mutated cell lines was significantly increased as compared with that of the lines (1.54 +/- 0.32 nmol/mg) without the G(alpha)s mutation (P < 0.01, by paired t-test). Also, these three cell lines had an activating mutation in Ki-ras codon 12 (GGT-->GAT). One TSH-R gene mutation was found with a base substitution in codon 636 (TGC-->TGT) but no amino acid change. No p53 gene (exons 5-8) mutations were detected in any of the cell lines analyzed. The results suggest that mutational activation of the G(alpha)s gene may play a tumorigenic role through constitutive activation of the cAMP pathway and that G-->A point mutations in the G(alpha)s and ras genes in thyroid carcinomas directly reflect interaction of the chemical carcinogen with guanine residues in DNA.

Animals↗
PubMed1997

Genetic changes in prostate cancer.

Recent advances in molecular biology have allowed us to understand that it is the accumulation of genetic alterations which leads to each step of tumorigenesis. What the specific alterations may be, however, often varies with each neoplasm. Prostate cancer is somewhat unique in its presentation to the pathologist of a bewildering array of histologies difficult to assign to diagnostic categories and contributing to misinterpretations of underlying molecular events. As with any malignancy, it is of utmost importance to thoroughly analyze and record the genetic aberrations found in prostate cancer with the objective of correlation to the pathology and natural history of the disease. Multiple oncogenes and tumor suppressor genes have been investigated in both clinical and latent cancer using conventional mutational analyses. To probe deeper into these genes and to uncover novel molecular events, genomic tumor DNA were examined using restriction landmark genomic scanning (RLGS), a method which allows the identification and comparison of specific genetic alterations within large segments and multiple samples of DNA at a time. This article reviews what has been identified based on numerous molecular studies, focusing on the genetic alterations peculiar to human prostate cancer.

Chromosome Deletion↗