Biomedical subjects

J Yokota

Publications and source records attributed to J Yokota.

At least 73 records · Page 4Linked to original sources

PubMed1999

Microsatellite instability in lymphoid leukemia and lymphoma cell lines but not in myeloid leukemia cell lines.

Microsatellite instability (MSI) represents a defect in the DNA mismatch repair system and has been shown to take part in the genesis and/or progression of several human malignancies. In hematological malignancies, the relevance of MSI has been a matter of controversy. Therefore, 29 microsatellite loci were examined for MSI in 57 leukemia and lymphoma cell lines by PCR analysis. Ladder formation of bands representing MSI was observed at multiple loci in 6 of 24 lymphoid leukemia/lymphoma cell lines and in 0 of 33 myeloid leukemia cell lines. Analysis for the BAT-26 and BAT-25 loci confirmed the presence of MSI in five of six lymphoid cell lines exhibiting ladder formation of bands. Thus, at least 5 out of 24 (21%) lymphoid leukemia/lymphoma cell lines were considered as being MSI-positive. These results indicate that MSI contributes to the development of lymphoid but not to myeloid malignancies.

Humans↗

PubMed1999

Activation of EVI1 transcripts with chromosomal translocation joining the TCRVbeta locus and the EVI1 gene in human acute undifferentiated leukemia cell line (Kasumi-3) with a complex translocation of der(3)t(3;7;8).

A cell line (Kasumi-3) established from acute myeloid leukemia (AML-M0) had unique phenotypes of undifferentiated leukemia cells with expression of both T cell and myeloid antigens. Kasumi-3 cells with t(3;7)(q26;q22) highly expressed a 6 kb transcript of EVI1, which is located on chromosome 3q26. Therefore, we further characterized the chromosomal breakpoint by pulsed-field gel electrophoresis near EVI1. We identified and isolated the chromosomal breakpoint at approximately 80 kb upstream from the 5' end of EVI1. Sequence analysis of the breakpoint revealed that the whole Vbeta region from T cell receptor beta (TCRbeta) at 7q35 was translocated to the upstream of EVI1. A 1.0 kb TCRbeta transcript was expressed in the Kasumi-3 cells, suggesting that TCRbeta rearrangement occurred as Dbeta-Jbeta joining events. Fluorescence in situ hybridization analysis revealed that the inverted chromosome 7q22-q35 segment between TCRbeta and the region proximal to the erythropoietin gene at 7q22 was translocated to the region distal to EVI1 in der(3). Since the telomeric region of chromosome 8 q was also translocated to the inverted chromosome 7q22-q35 segment in der(3), the chromosomal abnormalities of der(3) were defined as being der(3)t(3;7;8)(3pter-3q26::7q35-7q22::8q22 -8qter). It is suggested that a translocated enhancer element in the TCRbeta locus and/or loss of a negative regulatory element near EVI1 might function to enhance the EVI1 expression. Therefore, the enhanced EVI1 expression may contribute to the development of a subset of undifferentiated leukemia.

Acute Disease↗

PubMed1999

Mutation and expression of the p51 gene in human lung cancer.

A newly identified gene, p51, is a functional and structural homologue of the p53 gene and thus a Candidate tumor suppressor gene. To elucidate the role of the p51 gene in lung carcinogenesis, we determined the sequences of exon-intron boundaries and the 5'- and 3'-flanking regions of all the 15 coding exons and performed a mutation analysis, as well as detailed analysis for gene expression. A frameshift mutation was detected in 1 of 44 lung cancer cell lines, whereas no mutation was detected in 45 primary lung cancers. Thus, p51 mutation occurs only in a small subset of lung cancer. Expression of the p51 gene was detected in 23 of 43 cell lines by Northern blot analysis and 34 of 44 by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Thus, p51 expression is low or absent in a subset of lung cancer. The deltaN isotype of p51 transcripts was dominantly expressed in several cell lines, particularly in cell lines with high levels of p51 expression. Because the deltaN isotype encodes a protein that transdominantly suppresses the transactivation function of the TA type of p51, it is possible that p51 protein is not functionally active, even in lung cancer cells with p51 mRNA expression, due to expression of dominant-negative p51 protein. These results suggested that the p51 gene is inactive in a considerable proportion of lung cancers. RT-PCR analysis also revealed the presence of a novel type of mRNA transcript, p51delta, which lacks exons 12 and 13 by alternative splicing. The delta isotype was expressed in 18 of 44 lung cancer cell lines and in diverse normal tissues. Further analysis on p51 expression in cancerous as well as noncancerous cells will provide us with valuable information for the understanding of multiple functions of the p53 family proteins in human carcinogenesis.

Base Sequence↗

PubMed1999

Familial gastric cancer: clinicopathological characteristics, RER phenotype and germline p53 and E-cadherin mutations.

Gastric cancer frequently occurs in family members with hereditary non-polyposis colorectal cancer (HNPCC) and Li-Fraumeni syndrome (LFS) and germline E-cadherin mutations were recently identified in a subset of familial gastric cancers. Thus, families with an aggregation of gastric cancers were recruited by reviewing the genealogical trees of 3632 patients with gastric cancer. The criteria for recruiting such families were the following: at least three relatives should have gastric cancer and one of them should be a first degree relative of the other two; at least two successive generations should be affected; in one of the relatives gastric cancer should be diagnosed before age 50. Thirty-one cases (0.9%) fitted all three of these criteria. There were only gastric cancer patients in 18 of the 31 families and there were no families that fitted clinical criteria of HNPCC or LFS. Paraffin-embedded tissues were available in 29 probands and DNA was successfully isolated for molecular analyses in 13 probands. RER phenotype was detected in three (23%) cases, whereas germline p53 mutations were detected in none of 13 cases. A germline E-cadherin mutation was detected in one of three diffuse types and none of 10 intestinal types, however, a mutation resulting in the replacement of Gly by Val was detected in the precursor sequence. Thus, although familial clustering of gastric cancer occurs in approximately 1% of gastric cancer patients, germline mutations of the DNA mismatch repair, p53 and E-cadherin genes do not significantly contribute to such a clustering.

Adolescent↗

PubMed1999

How many tumor suppressor genes are involved in human lung carcinogenesis?

To date, only a limited number of tumor suppressor genes have been identified as being inactivated in lung cancer. The p53 and RB genes are frequently inactivated by genetic alterations such as chromosomal deletions and loss-of-function mutations, while the p16 gene is inactivated not only by genetic alterations but also by transcriptional silencing due to hypermethylation. Recently, it was shown that the FHIT gene encompassing the chromosomal fragile site, FRA3B, is also inactivated in a large proportion of lung cancers. Several lines of evidence indicate the presence of additional tumor suppressor genes involved in lung carcinogenesis. Lung cancer cells often show deletions at multiple chromosomal regions, and deletion mapping studies have defined more than 30 regions dispersed on 21 different chromosome arms as candidate tumor suppressor loci. Several chromosomal regions hypermethylated in lung cancer cells and a number of chromosomal fragile sites have been mapped to the regions deleted in lung cancer. These chromosomal loci can harbor unknown tumor suppressor genes inactivated in lung cancer. Studies on the inherited susceptibility to lung cancer in mice have also indicated the presence of additional tumor suppressor genes for lung cancer. Further analyses of these loci should elucidate how many tumor suppressor genes are involved in human lung carcinogenesis. Molecular and functional analyses of those genes will make it possible to fully understand the molecular mechanism of lung carcinogenesis.

Acid Anhydride Hydrolases↗

PubMed1999

Detection of three genetic polymorphisms in the 5'-flanking region and intron 1 of human CYP1A2 in the Japanese population.

Interindividual variability of the activity of CYP1A2 may be expected to affect cancer susceptibility, since the enzyme is capable of activating several carcinogens. In the present study, we found three new polymorphisms in the 5'-flanking region (CYPIA2/B) and intron 1 (CYPIA2/C and CYP1A2/D) of CYP1A2 in Japanese by using polymerase chain reaction-single strand conformation polymorphism. We developed methods to detect these polymorphisms by polymerase chain reaction-restriction fragment length polymorphism and performed a population study (159 subjects) to estimate the frequencies of the alleles. The frequencies of the CYP1A2/A (adenine), CYP1A2/B (thymine-deleted), CYP1A2/C (guanine) and CYP1A2/D (adenine) variants were 21.1, 42.0, 8.2 and 61.3%, respectively. The results of family study supported the idea that these CYP1A2 genotypes are inherited with an autosomal codominant transmission.

Cytochrome P-450 CYP1A2↗

PubMed1999

Ovarian cancer: loss of heterozygosity frequently occurs in the ATM gene, but structural alterations do not occur in this gene.

Ataxia-telangiectasia is a multisystem recessive disease characterized clinically by cerebellar ataxia, oculocutaneous telangiectasias, immunodeficiency, sensitivity to radiomimetic agents and an increased predisposition to cancer. This pleiotropic disorder is caused by mutations in the ATM gene, which is located at the human chromosomal region 11q23. Loss of heterozygosity (LOH) at 11q22-q23 is a frequent event in ovarian cancer, suggesting the presence of a tumor suppressor gene in this region. We have found that LOH in the ATM gene occurred in 44% of informative cases in a series of 22 primary ovarian tumors. LOH of this region occurred at the same frequency during the advanced stages (III-IV; 3/9, 33%) as in the early stages (I-II; 4/13, 31%) of ovarian cancer. To investigate the role of ATM in ovarian cancer, we used a PCR-based single-strand conformation polymorphism assay for mutation detection of the entire coding sequence of the ATM gene (65 exons) in 22 ovarian tumors. No somatic alterations of the ATM gene were found in these ovarian cancer samples including those with LOH present in the ATM gene. Our study has identified a region (11q23) which probably contains a frequently altered tumor suppressor gene in ovarian cancer, and this gene does not appear to involve the coding sequences of the ATM gene.

Adenocarcinoma↗

PubMed1999

Activation of RB tumor suppressor protein and growth suppression of small cell lung carcinoma cells by reintroduction of p16INK4A gene.

The p16INK4A tumor suppressor gene is frequently inactivated in non-small cell lung carcinoma (NSCLC) and is less frequently inactivated in small cell lung carcinoma (SCLC) by mutation, deletion or DNA methylation. There are several reports that the reintroduction of the p16INK4A gene into p16(-) NSCLC cells results in significant growth suppression. However, there have been no reports of reintroduction of the p16INK4A gene into SCLC cells. To assess the biological significance of p16INK4A inactivation in the development of SCLC, full-length p16INK4A cDNA was introduced into an SCLC cell line, Ms-13, in which the p16INK4A protein was not detected. SCLC cells stably transfected with the p16INK4A expression vector formed only 2-16% of the number of neomycin-resistant colonies formed by cells transfected with a control vector, and no expression of exogenous p16INK4A protein was detected in any of 16 expanded clones. Transient transfection of the p16INK4A gene into SCLC cells resulted in exogeneous p16INK4A protein expression and dephosphorylation of endogenous retinoblastoma (RB) protein. These results suggest that the restoration of the p16INK4A function suppresses the growth of SCLC cells by dephosphorylation of the RB protein. Therefore, inactivation of p16INK4A may play an important role in the enhancement of growth of p16INK4A(-) RB(+) SCLC tumors in vivo.

Adult↗

PubMed1999

Comprehensive analysis of p53 gene mutation characteristics in lung carcinoma with special reference to histological subtypes.

To date, the characteristics of p53 gene mutations in lung cancer have been extensively investigated. However, current estimates of p53 alterations are inaccurate, since most investigators have limited their analyses to exons 5 to 8 of the p53 gene. We examined 52 lung carcinoma cell lines and 106 primary non-small cell lung carcinomas (NSCLC) for mutations in the entire coding region of the p53 gene, from exons 2 to 11. High resolution single strand conformation polymorphism analysis was performed using a modified electrophoretic apparatus with a high concentration gel (14%) and accurate temperature control. The prevalence of mutations was high (more than 80%) in both small cell lung carcinoma (SCLC) (15 of 18) and NSCLC cell lines (28 of 34), and 9 of 45 mutations (20%) were detected outside the region of exons 5 to 8. The frequency of the mutations in primary NSCLC was 48% (51 of 106) and was significantly different (p=0.01) between adenocarcinoma (39%) and squamous cell carcinoma (67%). A-->G transitions (14%, 6 of 43 cases) as well as G-->T transversions (26%, 11 of 43 cases) were frequently detected with significant strand bias in smoking patients, suggesting that carcinogens causing these mutations are involved in smoking associated lung carcinogenesis.

Adenocarcinoma↗

PubMed1999

Prognostic significance of allelic imbalances on chromosome 9p in stage I non-small cell lung carcinoma.

Loss of heterozygosity (LOH) on chromosomes 2q, 9p, 18q, and 22q frequently occurs in advanced non-small cell lung carcinoma (NSCLC). The association of p53 mutations with prognosis is still unclear in NSCLC. Therefore, we investigated the prognostic significance of allelic imbalances (AI) on these chromosomes and p53 mutations in 108 cases of stage I NSCLC by PCR amplification of polymorphic dinucleotide repeat-containing sequences and PCR-single strand conformation polymorphism analysis. AI on 2q, 9p, 18q, and 22q was detected in 22, 38, 29, and 15% of cases, respectively, whereas p53 was mutated in 41% of stage I NSCLC. AI on 9p and 22q and p53 mutations were significantly associated with shortened survival of the patients (P = 0.010, 0.024, and 0.022, respectively). Although gender and smoking history showed more significant associations with prognosis than other clinicopathological and molecular parameters, independent prognostic significance for AI on 9p was observed (P = 0.002) in male patients with a positive smoking history. These results indicate that clinical aggressiveness of early-stage NSCLC can be partly defined by the presence of AI on chromosome 9p in cancer cells, and that AI on 9p could be a clinically useful prognostic indicator for early-stage NSCLC patients.

Adult↗

PubMed1999

[Genetic and epigenetic alterations associated with cancer metastasis].

It is now well accepted that cancer is attributed to the accumulation of genetic alterations in the cells. Thus, to understand the molecular mechanisms of cancer metastasis, it is indispensable to identify the genes whose alterations accumulate during cancer progression as well as the genes whose expression is responsible for invasion and metastasis. Two different molecular approaches have been taken to identify such genes. One is the identification of genes whose alterations accumulate during cancer progression. The other is the identification of genes whose expression is responsible for the acquisition of metastatic potential in cancer cells. Molecular analyses of cancer cells in various stages of progression have revealed that alterations of tumor suppressor genes and oncogenes accumulate during cancer progression and correlate with the clinical aggressiveness of cancer cells. Comparative analyses of gene expression profiles between high-metastatic and non-metastatic cells have also revealed that various genes are differentially expressed in association with the metastatic potential of cancer cells. In the near future, the information obtained from these studies can be applied to the diagnosis, treatment and prevention of metastases.

Base Pair Mismatch↗

PubMed1999

Genetic polymorphism of CYP2D6 in the Japanese population.

The frequencies of CYP2D6 mutations in a Japanese population were investigated. Individuals were classified into three groups: control individuals, cancer patients and Parkinsonians. Genotyping for CYP2D6*3, CYP2D6*4 and CYP2D6*18 was carried out using the polymerase chain reaction, and that for CYP2D6*5 was also carried out using XbaI restriction fragment length polymorphism. The frequencies of the CYP2D6*3, CYP2D6*4, CYP2D6*5 and CYP2D6*18 mutant alleles were 0%, 0.77%, 4.10% and 0.53% in more than 256 Japanese control individuals, respectively. Based on these data, the population frequency of the CYP2D6 poor metabolizer phenotype was estimated to be 0.29%. The distribution of the four mutated alleles was not significantly different between control individuals and cancer patients or Parkinsonians.

Alleles↗

PubMed1999

Familial gastric cancer: overview and guidelines for management.

Families with autosomal dominant inherited predisposition to gastric cancer have been described. More recently, germline E-cadherin/CDH1 mutations have been identified in hereditary diffuse gastric cancer kindred. The need to have protocols to manage and counsel these families in the clinic led a group of geneticists, gastroenterologists, surgeons, oncologists, pathologists, and molecular biologists to convene a workshop to produce consensus statements and guidelines for familial gastric cancer. Review of the available cancer pathology from people belonging to families with documented germline E-cadherin/CDH1 mutations confirmed that the gastric cancers were all of the diffuse type. Criteria to define the different types of familial gastric cancer syndromes were agreed. Foremost among these criteria was that review of histopathology should be part of the evaluation of any family with aggregation of gastric cancer cases. Guidelines for genetic testing and counselling in hereditary diffuse gastric cancer were produced. Finally, a proposed strategy for clinical management in families with high penetrance autosomal dominant predisposition to gastric cancer was defined.

Cadherins↗

PubMed1999

[Acquired pendular nystagmus after pontine hemorrhage].

A 60-year-old hypertensive woman had a pontine hemorrhage that caused slight right hemiplegia, deep sensory disturbance on her right side and dysarthria. Three months after the stroke, she was transferred to our hospital for rehabilitation. Approximately 6 months later, she gradually began to complain of the visual oscillation. Continual, unceasing conjugate vertical/rotatory eye movements were observed. Fixation was momentary at best because of an inability to dampen the spontaneous eye movements. Electrooculography (EOG) showed bilateral vertical/rotatory sinusoidal eye movements of 2.5 Hz frequency and 10- to 35-degree amplitude. Both vertical and horizontal optokinetic nystagmus were absent. Caloric stimulation did not evoke any responses bilaterally. There were no rhythmical movements at similar frequencies in other parts of the body such as palatal myoclonus. MRI revealed not only hematoma mainly at the dorsal pontine tegmentum but also hypertrophy of the inferior olive nucleus, suggesting disruption of the central tegmental tract. Lesions of this tract may be one cause of pendular nystagmus. Several drug therapies were investigated for the nystagmus. There was no response to baclofen 15 mg. Trihexyphenidyl 4 mg was discontinued because of drug-induced hallucinations. Tiapride 600 mg and phenobarbital 90 mg were each slightly effective in reducing both frequency and amplitude of nystagmus. Treatment with clonazepam 1 mg resulted in the striking disappearance of nystagmus. She was aware of this and no longer experienced oscillopsia. Despite the visual benefit, however, the patient did not wish to continue this drug because of drowsiness and muscle relaxation. The potential long-term therapeutic application of clonazepam should be further investigated. To our knowledge, there have been no reports of successful treatment in acquired pendular nystagmus with clonazepam. Therefore, based on this favorable experience, it is suggested that clonazepam should be added to the list of potential therapies for pendular nystagmus.

Anticonvulsants↗

PubMed1999

hOGG1 Ser326Cys polymorphism and lung cancer susceptibility.

The human homologue of the yeast OGG1 gene, hOGG1, has been cloned, and its genetic structure has been determined. Several polymorphisms in the hOGG1 gene were detected in the Japanese populations, and among them, the Ser-Cys polymorphism at codon 326 has been shown to have a functional difference in complementation of mutant Escherichia coli that is defective in the repair of 8-hydroxyguanine. Activity in the repair of 8-hydroxyguanine is greater in hOGG1-Ser326 protein than in hOGG1(326) protein. Because many environmental carcinogens produce 8-hydroxyguanine residue and mismatching to this modified base potentially causes oncogenic mutations, the capacity to repair these lesions can be involved in cancer susceptibility in human beings. We, therefore, examined allele distributions of the Ser326Cys polymorphism in a case-control study of male lung cancer in Okinawa. The analyses based on 241 cases and 197 hospital controls disclosed the following findings. (a) Those with the Cys/Cys genotype were at an increased risk of squamous cell carcinoma and nonadenocarcinoma compared to those with the Ser/Cys and those with the Ser/Ser genotypes combined. The odds ratios adjusted for age and smoking history were 3.01 (95% confidence interval, 1.33-6.83) and 2.18 (95% confidence interval, 1.05-4.54), respectively. (b) The odds ratios for other histological subtypes of lung cancer or those in total were not significant. Those for Cys/Cys or Ser/Cys genotype against Ser/Ser did not reach statistical significance in any cell type. (c) The distributions of this polymorphism varied for different populations (Chinese, Japanese, Micronesians, Melanesians, Hungarians, and Australian Caucasians), with much less prevalence of Cys allele in the latter three populations. Although our sample size was limited, these results indicate that the Ser326Cys variant may be related to squamous cell lung cancer susceptibility. The Cys/Cys genotype appears to be more susceptible to squamous cell carcinoma, although the risk is less than that previously reported to be associated with the CYP1A1 gene. Further studies are needed to assess the importance of the interpopulation variation to cancer susceptibility.

Adult↗

PubMed1998

The p16 (CDKN2A) gene is involved in the growth of neuroblastoma cells and its expression is associated with prognosis of neuroblastoma patients.

We previously reported that loss of heterozygosity (LOH) on chromosome 9p21 correlates with poor prognosis of neuroblastoma and the p16 gene is not expressed in approximately two thirds of neuroblastoma cell lines. Here we demonstrated that p16 expression was induced by 5-aza-2-deoxycytidine treatment in cell lines with 5' CpG island methylation but not in cell lines without methylation. Furthermore, the cell cycle of neuroblastoma cell lines significantly delayed with accumulation of cells in G1 phase by transfection of a wild-type p16 expression vector. These results indicate that p16 is inactivated in part by DNA methylation and its expression is involved in the growth of neuroblastoma cells in vitro. To assess the biological and clinical significance of p16 expression in primary tumors, we undertook immunohistochemical analysis in 74 paraffin sections of neuroblastomas. p16 protein was undetectable in 45 of 74 cases (61%) and lack of p16 expression significantly correlated with poor prognosis of patients and advanced stage of the disease. There was no correlation between loss of p16 expression and N-myc amplification in these tumors. These results indicate that inactivation of the p16 gene is involved in the progression of neuroblastoma independently of N-myc amplification.

Azacitidine↗

PubMed1998

Clinicopathological significance of Fhit protein expression in stage I non-small cell lung carcinoma.

Abnormalities in structure and expression of the FHIT gene have been detected in a considerable fraction of primary lung tumors. Previous reports indicated that FHIT gene alterations can be simply detected by immunohistochemical methods. Therefore, we investigated the association of Fhit expression with clinicopathological features and allelic imbalance (AI) at the FHIT locus in 105 stage I non-small cell lung cancers (NSCLC) by the immunohistological method and PCR analysis. Thirty-six of 105 (34%) tumors showed marked reduction of Fhit immunoreactivity. Fhit expression was markedly reduced in most squamous cell carcinomas (24 of 28, 86%), whereas such a reduction was detected only in a small subset of adenocarcinomas (7 of 67, 10%; P < 0.001). A marked reduction of Fhit protein expression was observed more frequently in patients with a smoking history (32 of 80, 40%) than in patients without a smoking history (4 of 25, 16%; P = 0.013). These results indicate that FHIT gene alterations preferentially occur in squamous cell carcinomas and in smokers. Furthermore, a reduction of Fhit protein expression in tumor cells was associated with a poorer survival of patients with stage I NSCLC, irrespective of histological subtypes of tumors (P = 0.005; log-rank test). Fhit expression was reduced preferentially in tumors with AI at the FHIT locus; however, AI at the FHIT locus did not correlate with patients' survival (P = 0.262; log-rank test). These results suggested that Fhit protein expression could be a useful molecular marker for the prognosis of patients with surgically resected stage I NSCLC.

Acid Anhydride Hydrolases↗

PubMed1998

Molecular karyotype (amplotype) of metastatic colorectal cancer by unbiased arbitrarily primed PCR DNA fingerprinting.

Genomic instability characterizes the aneuploid cancer cell. Losses of genetic material are critical in cancer by exposing recessive mutations in tumor suppressor genes. Gains of genetic material also may lead to overexpression of genes contributing to tumor progression either in the presence or absence of mutation. However, the detection of moderate gains (such as tri-tetraploidy) has been a challenge in cancer research. Unbiased DNA fingerprinting by the arbitrarily primed PCR allows the detection of moderate gains (in addition to losses) of DNA sequences of known chromosomal localization. We have generated in this manner a molecular karyotype of metastatic colon cancer. This amplotype shows that sequences from several chromosomes undergo both losses (1, 4, 9, 14, and 18) and gains (6, 7, 12, and 20) in over half of the tumors. Moreover, gains of sequences from chromosomes 8 and 13 occurred in most tumors, indicating the existence in these chromosomes of positive regulators of cell growth or survival that are under strong positive selection during tumor progression. We conclude that overrepresentation of these chromosomal regions is a critical step for metastatic colorectal cancer. Comparative amplotype analysis from primary and metastatic tumors suggest the existence in chromosome 4 of gene(s) whose loss is specifically selected in cells that reach the metastatic stage.

Alleles↗